Neurosurgical Operative Atlas Second Edition
Pediatric Neurosurgery
American Association of Neurosurgeons • Rolling Meadows, Illinois
Neurosurgical Operative Atlas Second Edition
Pediatric Neurosurgery
James Tait Goodrich, MD, PhD, DSci (Honoris Causa) Professor of Clinical Neurological Surgery, Pediatrics, Plastic and Reconstructive Surgery Albert Einstein College of Medicine Director, Division of Pediatric Neurosurgery Center for Craniofacial Disorders Children’s Hospital at Montefiore Bronx, New York
Thieme New York • Stuttgart American Association of Neurosurgeons Rolling Meadows, Illinois
Thieme Medical Publishers, Inc. 333 Seventh Ave. New York, NY 10001
American Association of Neurosurgeons (AANS)* 5550 Meadowbrook Drive Rolling Meadows, Illinois 60008-3852
*The acronym AANS refers to both the American Association of Neurological Surgeons and the American Association of Neurosurgeons. Associate Editor: Birgitta Brandenburg Assistant Editor: Ivy Ip Vice President, Production and Electronic Publishing: Anne T. Vinnicombe Production Editor: Print Matters, Inc. Vice President, International Marketing and Sales: Cornelia Schulze Chief Financial Officer: Peter van Woerden President: Brian D. Scanlan Cover illustration: Anita Impagliazzo Compositor: Compset, Inc. Printer: Everbest Printing Company Library of Congress Cataloging-in-Publication Data Neurosurgical operative atlas. Pediatric neurosurgery / [edited by] James Tait Goodrich. p. ; cm. Includes bibliographical references and index. ISBN 978-1-58890-510-9 (alk. paper) 1. Nervous system—Surgery—Atlases. 2. Children—Surgery—Atlases. 3. Pediatric neurology—Atlases. I. Goodrich, James T. [DNLM: 1. Nervous System Diseases—surgery—Atlases. 2. Child. 3. Infant. 4. Neurosurgical Procedures—methods—Atlases. WL 17 P371 2008] RD593.P3822 2008 618.92’8—dc22 2007048827 Copyright © 2008 by Thieme Medical Publishers, Inc., and the American Association of Neurosurgeons (AANS). This book, including all parts thereof, is legally protected by copyright. Any use, exploitation, or commercialization outside the narrow limits set by copyright legislation without the publisher’s consent is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage. Important note: Medical knowledge is ever-changing. As new research and clinical experience broaden our knowledge, changes in treatment and drug therapy may be required. The authors and editors of the material herein have consulted sources believed to be reliable in their efforts to provide information that is complete and in accord with the standards accepted at the time of publication. However, in view of the possibility of human error by the authors, editors, or publisher of the work herein or changes in medical knowledge, neither the authors, editors, or publisher, nor any other party who has been involved in the preparation of this work, warrants that the information contained herein is in every respect accurate or complete, and they are not responsible for any errors or omissions or for the results obtained from use of such information. Readers are encouraged to confirm the information contained herein with other sources. For example, readers are advised to check the product information sheet included in the package of each drug they plan to administer to be certain that the information contained in this publication is accurate and that changes have not been made in the recommended dose or in the contraindications for administration. This recommendation is of particular importance in connection with new or infrequently used drugs. Some of the product names, patents, and registered designs referred to in this book are in fact registered trademarks or proprietary names even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain. Printed in China 54321 ISBN 978-1-58890-510-9
To Setti S. Rengachary, MD, and Robert H. Wilkins, MD When the first edition of this remarkable atlas came out in early 1990s, it was an instant and powerful success in the neurosurgical literature. Drs. Rengachary and Wilkins recognized the power of the illustrated text and in this case designed a work that was clearly visual with the text being secondary. As neurosurgeons are visual animals, this was a successful design. Drs. Rengachary and Wilkins’ contributions to neurosurgery have been enormous. It is a true pleasure to help bring this remarkable atlas back in a second edition. However, it must be remembered that their original editorship led to this most elegant and influential series of operative chapters. In acknowledgment of their insights, their educational leadership, and, most importantly, their longstanding contributions to neurosurgery, I dedicate this work to these two scholars and superb neurosurgeons.
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Contents
Continuing Medical Education Credit Information and Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Continuing Medical Education Disclosure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii Series Foreword Robert Maciunas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xiii Foreword Richard D. Hayward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xix Chapter 1
Fibrous Dysplasia Involving the Craniofacial Skeleton. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 James Tait Goodrich
Chapter 2
Chiari Malformations and Syringohydromyelia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Elizabeth C. Tyler-Kabara and W. Jerry Oakes
Chapter 3
Unilateral and Bicoronal Craniosynostosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Kant Y. K. Lin, John A. Jane Jr., and John A. Jane Sr.
Chapter 4
Transoral Surgery for Craniovertebral Junction Abnormalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Arnold H. Menezes
Chapter 5
Malposition of the Orbits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 John A. Persing and Bianca I. Knoll
Chapter 6
Ventriculoatrial Shunting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 John Drygas and Stephen J. Haines
Chapter 7
Repair of “Growing” Skull Fracture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Tadanori Tomita
Chapter 8
Occipital Encephaloceles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 William O. Bell
Chapter 9
Surgical Management of Pansynostosis (Craniosynostosis) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 James Tait Goodrich and David L. Staffenberg
Chapter 10
Tethered Spinal Cord, Intramedullary Spinal Lipomas, and Lipomyelomeningoceles. . . . . . . . . . . . . . . . . . . . . . . . . 62 Elizabeth C. Tyler-Kabara and W. Jerry Oakes
Chapter 11
Encephaloceles of the Anterior Cranial Base. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Jonathan P. Miller and Alan R. Cohen
Chapter 12
Exorbitism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Constance M. Barone, David F. Jimenez, and James Tait Goodrich
Chapter 13
Depressed Skull Fracture in Infants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Marion L. Walker
Chapter 14
Orbital Hypertelorism and Orbital Dystopia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 Constance M. Barone, David F. Jimenez, and James Tait Goodrich
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viii Contents Chapter 15
Closure of the Myelomeningocele . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 David G. McLone
Chapter 16
Dandy-Walker Malformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Arthur E. Marlin and Sarah J. Gaskill
Chapter 17
Surgical Management of Chiari I Malformations and Syringomyelia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Elizabeth C. Tyler-Kabara, Richard B. Morawetz, and W. Jerry Oakes
Chapter 18
Split Cord Malformations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 Dachling Pang
Chapter 19
Tethered Cord Syndrome Secondary to Previous Repair of a Myelomeningocele . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 Timothy A. Strait
Chapter 20
Sectioning of the Filum Terminale. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 Frederick B. Harris, Naina L. Gross, and Frederick A. Boop
Chapter 21
Diastematomyelia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 Frederick B. Harris, Naina L. Gross, and Frederick A. Boop
Chapter 22
Lipomyelomeningoceles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Frederick B. Harris, Naina L. Gross, and Frederick A. Boop
Chapter 23
Untethering of the Spinal Cord after a Previous Myelomeningocele Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 Frederick B. Harris, Naina L. Gross, and Frederick A. Boop
Chapter 24
Brain Abscesses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Darric E. Baty, Eli M. Baron, and Christopher M. Loftus
Chapter 25
Unilateral Coronal Synostosis (Plagiocephaly) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 James Tait Goodrich and David L. Staffenberg
Chapter 26
Moyamoya Syndrome in Children with Pial Synangiosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 R. Michael Scott and Edward R. Smith
Chapter 27
Selective Dorsal Rhizotomy for Spastic Cerebral Palsy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Tae Sung Park and James M. Johnston
Chapter 28
Treatment of Lambdoidal Synostosis with Calvarial Reconstructive Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184 David F. Jimenez, Constance M. Barone, and James Tait Goodrich
Chapter 29
Early Treatment of Lambdoid Synostosis with Endoscopic-Assisted Craniectomy . . . . . . . . . . . . . . . . . . . . . . . . . . 190 David F. Jimenez and Constance M. Barone
Chapter 30
Posterior Plagiocephaly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Richard G. Ellenbogen, Sudesh J. Ebenezer, and Richard Hopper
Chapter 31
Sagittal Synostosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 Larry A. Sargent and Timothy A. Strait
Chapter 32
The Separation of Craniopagus Twins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Sami Khoshyomn and James T. Rutka
Chapter 33
Endoscopic Approaches to the Ventricular System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 David F. Jimenez
Chapter 34
Intraventricular Endoscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 Jonathan P. Miller and Alan R. Cohen
Chapter 35
Infected Ventriculoperitoneal Shunts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 Keyne K. Thomas, Sohaib A. Kureshi, and Timothy M. George
Chapter 36
Combined Fronto-Orbital and Occipital Advancement for Total Calvarial Reconstruction . . . . . . . . . . . . . . . . . . . 241 Ian F. Pollack
Chapter 37
Lumbosacral Meningoceles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 Ciaran J. Powers, Eric M. Gabriel, and Timothy M. George
Contents
ix
Chapter 38
Surgical Correction of Unilateral and Bilateral Coronal Synostoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256 Jack Chungkai Yu and Ann Marie Flannery
Chapter 39
Myelomeningoceles, Split Cord Malformations, and Filum Terminale Dysgenesis . . . . . . . . . . . . . . . . . . . . . . . . . . 262 Robert F. Keating
Chapter 40
Lipomyelomeningoceles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 James Tait Goodrich
Chapter 41
Brain Stem Gliomas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 Darlene A. Lobel and Mark R. Lee
Chapter 42
Posterior Fossa Decompression without Dural Opening for the Treatment of Chiari I Malformation . . . . . . . . . 281 Jonathan D. Sherman, Jeffery J. Larson, and Kerry R. Crone
Chapter 43
Metopic Synostosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286 Kant Y. K. Lin, John A. Jane Jr., and John A. Jane Sr.
Chapter 44
Total Cranial Vault Repair for Sagittal Craniosynostosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 John A. Jane Jr., Kant Y. K. Lin, Tord D. Alden, and John A. Jane Sr.
Chapter 45
Metopic Craniosynostosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 Paul C. Francel and Jayesh Panchal
Chapter 46
Unicoronal Synostosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 Jayesh Panchal and Paul C. Francel
Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
Continuing Medical Education Credit Information and Objectives
◆ Objectives Upon completion of this activity, the learner should be able to: 1. Describe the treatment and surgical management of pediatric neurosurgical disorders. 2. Demonstrate a full understanding of current neurosurgical operative techniques in pediatric neurosurgical disorders. 3. Discuss the operative management of complex pediatric neurosurgical disorders.
◆ Accreditation This activity has been planned and implemented in accordance with the Essentials and Standards of the Accreditation Council for Continuing Medical Education through the American Association of Neurological Surgeons (AANS*). The AANS is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.
◆ Credit The AANS designates this educational activity for a maximum of 15 AMA PRA Category 1 credits™. Physicians should only claim credit commensurate with the extent of their participation in the activity. The Home Study Examination is online on the AANS Web site at: www.aans.org/education/books/atlas3.asp Estimated time to complete this activity varies by learner; activity equaled up to 15 Category 1 credits of CME.
◆ Release/Termination Dates Original Release Date: August 1, 2008 The CME termination date is: August 1, 2011
*The acronym AANS refers to both the American Association of Neurological Surgeons and the American Association of Neurosurgeons.
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Continuing Medical Education Disclosure
The AANS controls the content and production of this CME activity and attempts to ensure the presentation of balanced, objective information. In accordance with the Standards for Commercial Support established by the Accreditation Council for Continuing Medical Education, speakers, paper presenters/authors, and staff (and the significant others of those mentioned) are asked to disclose any relationship they or their co-authors have with commercial companies which may be related to the content of their presentation. Speakers, paper presenters/authors, and staff (and the significant others of those mentioned) who have disclosed a relationship* with commercial companies whose products may have a relevance to their presentation are listed below.
Author Name
Disclosure
Type of Relationship
Frederick A. Boop Richard G. Ellenbogen Paul C. Francel Arthur E. Marlin John A. Persing Jonathan D. Sherman
Cyberonics NIH/NCI Medtronic Medical Energy W. Lorenz Group Zimmer TransOne
Paid for speech given at Grand Rounds 2/2007 Grant Clinical research study grant Consultant fee Grant (no personal funds paid) Consultant fee (signed agreement) Honorarium—gave speech
Speakers, paper presenters/authors, and staff (and the significant others of those mentioned) who have reported they do not have any relationships with commercial companies: Author Name Tord D. Alden Eli M. Baron Constance M. Barone Darric Baty William O. Bell Alan R. Cohen Kerry R. Crone John Drygas Sudesh J. Ebenezer Ann Marie Flannery Eric M. Gabriel Sarah J. Gaskill Timothy M. George
James Tait Goodrich Naina L. Gross Stephen J. Haines Frederick B. Harris Richard Hopper John A. Jane Jr. John A. Jane Sr. David F. Jimenez James M. Johnston Robert F. Keating Sami Khoshyomn Bianca Knoll Sohaib A. Kureshi
Jeffery J. Larson Mark R. Lee Kant Y. K. Lin Darlene A. Lobel Christopher M. Loftus David G. McLone Arnold H. Menezes Jonathan P. Miller Richard B. Morawetz W. Jerry Oakes Jayesh Panchal Dachling Pang Tae Sung Park
Ian F. Pollack Ciaran J. Powers James T. Rutka Larry A. Sargent R. Michael Scott Edward R. Smith David L. Staffenberg Timothy A. Strait Keyne K. Thomas Tadanori Tomita Elizabeth C. Tyler-Kabara Marion L. Walker Jack C. Yu
*Relationship refers to receipt of royalties, consultantship, funding by research grant, receiving honoraria for educational services elsewhere, or any other relationship to a commercial company that provides sufficient reason for disclosure.
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Series Foreword
The Publications Committee of the American Association of Neurological Surgeons began publishing the first edition of the Neurosurgical Operative Atlas in 1991. To allow for timely publication, coverage of six operations was published at bimonthly intervals in looseleaf format in the order finished manuscripts were received. The completed series had nine volumes and covered the entire spectrum of neurosurgery. The goal was to publish a comprehensive reference that included well-established neurosurgical procedures as practiced in the United States and Canada by authors who are respected in the field. Working together, the AANS Publications Committee and Thieme New York have organized the second edition of this atlas series. The atlas’s main purpose remains the same, to be a ready reference for well-established neurosurgical procedures for trainees and practitioners of neurosurgery worldwide. The new edition contains five volumes, covering neurooncology; spine and peripheral nerves; functional; pediatric; and vascular neurosurgery. For each volume, one or more
lead editors with known expertise in the subject area were selected. Each volume editor had complete freedom to add, revise, or delete chapters. The number of chapters per volume is approximately the same as the number of chapters in that particular subject area found in the first edition. Each chapter is designed to teach a specific surgical technique or approach. The illustrations of the techniques are a vital part of the work, and the authors commissioned most of the drawings in color. The text in each chapter covers the case selection, the operative indications and contraindications, special points in the anesthetic technique, a step-bystep detailed description of the operation, and postoperative complications. Detailed discussion of diagnostic techniques, pathology, mechanisms of disease, histology, and medical management are not included since they are logically outside the scope of a surgical atlas. Detailed tables, reference lists, and statistical analysis of results are also not included because they are readily available in standard texts. We hope you find this reference of value in your practice of neurosurgery. Robert Maciunas, MD Past Chair, AANS Publications Committee Professor of Neurosurgery University Hospitals of Cleveland Cleveland, Ohio
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Foreword
I came to pediatric neurosurgery after a nearly exclusively adult neurosurgical training, and I confess to being a late convert to pediatric neurosurgery as an almost autonomous specialty. The surgical skills required to remove a medulloblastoma were no different, I thought, to those needed to excise a cerebellar metastasis (a far more frequently occurring pathology), and as for all those shunts . . . ! And the conditions whose management fell within the province of the pediatric neurosurgeon were all so rare . . . I was wrong for several reasons, not least of which was to regard pediatric neurosurgery too narrowly—as no more than the deployment of particular operations. But I was right about how uncommon (fortunately) in terms of their overall incidence the conditions we deal with are. Pediatric neurosurgery is a specialty greedy for the resources it devours to treat comparatively few patients, hydrocephalus aside. How should the expense of managing a newborn with, say, Apert syndrome through infancy, childhood, and adolescence be balanced against returning so many more adults to their former lifestyle after the replacement of a painful hip or knee? Or screening for such occult harbingers of morbidity as hypertension or glaucoma? It does not take long for the fascination, indeed the privilege, of working with children and their families to suppress such thoughts, but nevertheless these remain questions to which every pediatric neurosurgeon must have their own answer. It has been said, and rightly so, that a society should be judged by the way it treats its young and its old—those on the vulnerable edges of life. James Goodrich, in assembling the impressive list of internationally renowned experts who make up the list of his contributors, has demonstrated only too clearly the commitment of the North American pediatric neurosurgical community to the care of its sick children. Since the first edition of this book there has been further acceptance and consolidation of pediatric neurosurgery as a discipline that requires its own specialty training. The conditions that are encountered in a pediatric neurosurgical practice vary markedly from those encountered in an adult practice, as a glance at the titles of these chapters with their emphasis upon a variety of congenital disorders immediately reveals.
The days are long past, I hope, when a surgeon, as ambitious as foolish, would wish to embark upon his or her first transoral procedure with no more technical experience than having read Arnold Menezes’s excellent chapter on this subject. Then who—and what—is an Operative Atlas such as this for? It is first and foremost a most valuable educational tool, one that I would submit should be an essential companion for pediatric neurosurgeons at all stages of their career. Neurosurgical residents can read up on the procedures on which they are about to assist; the increased understanding of how and why these procedures are done will make them not only more knowledgeable but all the more useful. Furthermore, when the surgery is over they can come back to the atlas to find out exactly why and how some maneuver, whose significance may have escaped them at the time, was accomplished. And not only the residents. Just as there exists no operation that cannot be improved (the final improvement being to do away with the need for surgery altogether) so there is no neurosurgeon whose training is finished; indeed, anyone who makes such a claim about themselves has, whether they recognize it or not, already retired. What pediatric neurosurgeon, however long ago their residency ended, would not wish to discover how the experts who have contributed to this volume deal with conditions as frustrating as a lipomyelomeningocele or a brainstem glioma? Or the management of a common nuisance such as a shunt infection? Or something more critical, such as a total calvarial remodelling for the older child with sagittal synostosis—surely the limit to which “cosmetic” neurosurgery can be stretched? I cannot imagine a pediatric neurosurgeon (in or postresidency) who will not be stimulated, intrigued, and (hopefully) sometimes provoked by what has been contributed by the heady selection of experts James Goodrich has assembled here. He is to be congratulated not only for bringing them together to produce this book but also for demonstrating so clearly the commitment of the pediatric neurosurgical community of North America to its own continuing education for the benefit of sick and disabled children worldwide. Richard D. Hayward, FRCS Professor, Pediatric Neurosurgery Great Ormond Street Hospital for Children London, United Kingdom
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Preface
O! Author, with what words will describe with such perfection the whole configuration, such as the sketch does here? Leonardo da Vinci Quaderni d’Anatomia Volume II, fol. 2r. Christiania: Dybwad, 1911–1916. O! reader, the same feeling that inspired Leonardo to restate the Vitruvian man and provide the perfect proportion inspired the authors to provide this palimpsest atlas, now in the second edition with pages now re-etched and redone. Surgical techniques have continued to evolve with both new technologies and also newly designed surgical approaches. In the early part of the 16th century, Leonardo da Vinci planned a 120-volume text on anatomy with mostly anatomic illustrations. Early on, Leonardo recognized that the visual images were more important in educating the individual; he has clearly remained the master at that concept. In producing a second edition of this work, we clearly wanted to keep the original design with the illustrations being paramount and with text being added clarification. In an effort to disseminate these surgical techniques, this atlas was formulated on the principle that the visual image is most important; it must be clear, precise, and bring forth the surgical design with precision. In addition, the text design and presentation needs to be straightforward and practical. The atlas-style format using an operative narrative was selected in the belief that, like Leonardo da Vinci, surgeons are more comfortable with the “visual” image than the written word—though both are provided! Starting with the first edition of this work, we selected the chapters that dealt with pediatric subjects. The original authors were asked to update and revise their presentations as they felt necessary. In some cases extensive changes were made, and in others only some editing was done. A number of the chapters are edited by several surgical subspecialists, a common trend these days. Many surgical procedures have clearly benefited from the skills of several surgical subspecialties. In recent years new materials, techniques, and equipment have been offered to neurosurgeons for their operations. When relevant, those contributions have been added. We specifically asked the authors to avoid lengthy bibliographies and to be
practical in their presentations; we think the readership will see that this is clearly evident throughout the volume. Where appropriate, the authors have been asked to include imaging, whether computed tomography, magnetic resonance imaging, or other radiologic studies. The format of the chapters has been kept the same throughout in order that the presentation remains clear and follows a consistent structure. For our surgical colleagues outside of neurosurgery, a careful review of this book will reveal useful surgical ideas and techniques. The format is designed so that not only is the concept provided and discussed, but the surgical technique is discussed step by step in an atlas format, detailing each member of the surgical teams’ contributions. Standards, techniques, and styles are continuing to change so that hopefully a third edition of this book will be necessary in the not so distant future. Our founding neurosurgical father Harvey Cushing put it best when he stated: The knowledge which a man can use is the only real knowledge, the only knowledge which has life and growth in it and converts itself into practical power. The rest hangs like dust about the brain and dries like raindrops off the stones. Harvey Cushing Laboratories: Then and Now, 1922, p. 9
Acknowledgments No book comes about without the efforts of a number of people, and this book is certainly no exception. We would like to start by thanking the editorial and production teams at Thieme New York—as always an extremely talented and most pleasant group to work with—it is clearly through their efforts that the published result is so outstanding. At the top of the list of people are Brian Scanlan, Tim Hiscock, Birgitta Brandenburg, Richard Rothschild, Dominik Pucek, and Ivy Ip. A special thanks to you all for your individual contributions, which included skilled editing, production, and design. To Helen Lopez and Daniel Jimenez, a sincere thanks for handling all the calls, mailing the bulky manuscripts, and reminding us to be nice and to be on time.
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xviii Preface This book is about neurosurgery, and a fundamental part of that team is our neurosurgical operating room nurses and technicians. To my operating room nurses and technicians, such an essential part of my surgical team, special thanks for watchful vigilance and your helpful advice and insight offered in the care of patients. Hopefully this volume will be helpful to operating room teams around in the world. Thanks to Mary Speranza,
Esther Ko-Uy, Katie Thompson, Charles Price, Loretta Caldwell, Sylvan Fowles, Gabriel Ofurhie, Noel Greene, Danielle Dunne, Cecille Edwards, Bindu Peter, and, finally, Charisse Terry—a most remarkable and skilled team with which to work! Finally, to all the authors who contributed to this book, thanks for doing such a wonderful job in presenting some very complex subjects.
Contributors
Tord D. Alden, MD Assistant Professor Department of Pediatric Neurosurgery Feinberg School of Medicine Northwestern University Division of Neurosurgery Children’s Memorial Hospital Chicago, Illinois Eli M. Baron, MD Attending Neurosurgeon Cedars-Sinai Institute for Spinal Disorders Los Angeles, California Constance M. Barone, MD, FACS Division Head and Professor University of Texas Health Science Center at San Antonio Division of Plastic and Reconstructive Surgery San Antonio, Texas Darric E. Baty, MD Resident Department of Neurosurgery Temple University School of Medicine Temple University Hospital Philadelphia, Pennsylvania William O. Bell, MD, FACS Neurosurgical Associates of the Carolinas Winston-Salem, North Carolina Frederick A. Boop, MD Associate Professor of Neurosurgery Chief, Pediatric Neurosurgery Semmes-Murphey Clinic LeBonheur Children’s Hospital Memphis, Tennessee
Alan R. Cohen, MD Division of Pediatric Neurosurgery Rainbow Babies and Children Hospital Cleveland, Ohio Kerry R. Crone, MD Professor of Neurosurgery and Pediatrics Director, Pediatric Neurosurgery Cincinnati Children’s Hospital Medical Center Cincinnati, Ohio John Drygas, MD, MS Neuroscience and Spine Associates Naples, Florida Sudesh J. Ebenezer, MD, EdM Department of Neurological Surgery The University of Washington Children’s Hospital and Regional Medical Center Seattle, Washington Richard G. Ellenbogen, MD, FACS Professor and Chairman Department of Neurological Surgery University of Washington School of Medicine Neurological Surgeon Children’s Hospital and Regional Medical Center Seattle, Washington Ann Marie Flannery, MD, FACS, FAAP Reinert Chair in Pediatric Neurosurgery Department of Surgery Saint Louis University School of Medicine Cardinal Glennon Children’s Hospital St. Louis, Missouri Paul C. Francel, MD, PhD Oklahoma Sports Science and Orthopedics Oklahoma City, Oklahoma
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xx Contributors Eric M. Gabriel, MD St. Vincent’s Medical Center Jacksonville, FLorida Sarah J. Gaskill, MD, FAAP, FACS Associate Professor Department of Neurosurgery University of South Florida Tampa, Florida Center for Pediatric Neurosurgery and Neuroscience All Children’s Hospital St. Petersburg, Florida Timothy M. George, MD, FAAP, FACS Chief of Service Dell Children’s Medical Center of Texas Austin, Texas James Tait Goodrich, MD, PhD, DSci (Honoris Causa) Professor of Clinical Neurological Surgery, Pediatrics, Plastic and Reconstructive Surgery Albert Einstein College of Medicine Director, Division of Pediatric Neurosurgery Center for Craniofacial Disorders Children’s Hospital at Montefiore Bronx, New York Naina L. Gross, MD Department of Neurosurgery Oklahoma University Oklahoma City, Oklahoma Stephen J. Haines, MD Professor and Head Department of Neurosurgery University of Minnesota Minneapolis, Minnesota Frederick B. Harris, MD, MS Division of Neurosurgery St. Mary’s Duluth Clinic Duluth, Minnesota Richard Hopper, MD Surgical Director Craniofacial Center Children’s Hospital & Regional Medical Center Seattle, Washington
John A. Jane Jr., MD Assistant Professor of Neurosurgery and Pediatrics Department of Neurosurgery University of Virginia Health System Charlottesville, Virginia John A. Jane Sr., MD, PhD Professor and Chairman Department of Neurosurgery University of Virginia Charlottesville, Virginia David F. Jimenez, MD Professor and Chairman Department of Neurosurgery University of Texas Health Science Center at San Antonio San Antonio, Texas James M. Johnston, MD Department of Neurosurgery Washington University School of Medicine St. Louis Children’s Hospital St. Louis, Missouri Robert F. Keating, MD Associate Professor of Neurological Department of Surgery and Pediatrics George Washington University School of Medicine Division of Pediatric Neurosurgery Children’s National Medical Center Washington, DC Sami Khoshyomn, MD Pediatric Neurosurgery Fellow Hospital for Sick Children Toronto, Ontario Canada Bianca I. Knoll Chief Resident Department of Plastic Surgery Yale University School of Medicine Division of Plastic Surgery Yale-New Haven Hospital New Haven, Connecticut Sohaib A. Kureshi, MD Neurosurgical Medical Clinic Chula Vista, California Jeffrey J. Larson, MD Neurosurgeon Coeur d’ Alene Spine and Brain, PLLC Coeur d’Alene, Idaho
Contributors Mark R. Lee, MD Chairman, Department of Neurosurgery Medical College of Georgia Augusta, Georgia Kant Y. K. Lin, MD Professor Department of Plastic Surgery University of Virginia School of Medicine Charlottesville, Virginia Darlene A. Lobel, MD Chief Resident Department of Neurosurgery Medical College of Georgia Augusta, Georiga Christopher M. Loftus, MD, DHC (Hon.), FACS Professor and Chairman Department of Neurosurgery Assistant Dean for International Affiliations Temple University School of Medicine Philadelphia, Pennsylvania Arthur E. Marlin, MD, MHA Professor Department of Neurosurgery University of South Florida Division of Pediatric Neurosurgery All Children’s Hospital Tampa, Florida David G. McLone, MD Professor Department of Pediatric Neurosurgery Feinberg School of Medicine Northwestern University Children’s Memorial Hospital Chicago, Illinois Arnold H. Menezes, MD, FACS, FAAP Professor and Vice Chairman Department of Neurosurgery University of Iowa Carver College of Medicine Department of Neurosurgery University of Iowa Hospitals and Clinics Iowa City, Iowa Jonathan P. Miller, MD Department of Neurosurgery University Hospitals and Health System Cleveland, Ohio Richard B. Morawetz, MD Division of Neurosurgery UAB Hospital Birmingham, Alabama
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W. Jerry Oakes, MD Dan L. Hendly, Professor Department Surgery Division of Neurosurgery University of Alabama at Birmingham School of Medicine Pediatric Neurosurgery Children’s Hospital Birmingham, Alabama Jayesh Panchal, MD, MBA, FRCS Genesis Plastic Surgery and Medical Spa Edmond, Oklahoma Dachling Pang, MD, FRCS(C), FACS Professor of Pediatric Neurosurgery University of California Davis Chief, Regional Centre of Pediatric Neurosurgery Kaiser Permanente Hospital, Northern California Oakland, California Tae Sung Park, MD Shi H. Huang Professor of Neurosurgery Department of Neurosurgery Washington University in St. Louis–School of Medicine Division of Neurosurgery St. Louis Children’s Hospital St. Louis, Missouri John A. Persing, MD Professor and Chief Department of Plastic Surgery Yale University School of Medicine Division of Plastic Surgery Yale–New Haven Hospital New Haven, Connecticut Ian F. Pollack, MD, FACS, FAAP Professor Department of Neurosurgery University of Pittsburgh School of Medicine Chief of Pediatric Neurosurgery Children’s Hospital of Pittsburgh Pittsburgh, Pennsylvania Ciaran J. Powers, MD, PhD Department of Surgery, Division of Neurosurgery Duke University Division of Neurosurgery Durham, North Carolina James T. Rutka, MD, PhD, FRCS(C), FACS, FAAP Professor and Chairman Department of Neurosurgery University of Toronto Division of Neurosurgery The Hospital for Sick Children Toronto, Ontario Canada
xxii Contributors Larry A. Sargent, MD Professor and Chair Department of Plastic Surgery UT College of Medicine–Chattanooga Unit Chattanooga, Tennessee
Keyne K. Thomas, MD Pediatric Neurosurgery Service Division of Neurosurgery Duke University Medical Center Durham, North Carolina
R. Michael Scott, MD Neurosurgeon-in-Chief Department of Neurosurgery The Children’s Hospital Boston, Massachusetts
Tadanori Tomita, MD The Yaeger Professor of Pediatric Neurosurgery Professor of Neurosurgery Feinberg School of Medicine Northwestern University Chairman, Division of Pediatric Neurosurgery Children’s Memorial Hospital Chicago, Illinois
Jonathan D. Sherman, MD Mountain Neurosurgical and Spine Center, PA Asheville, North Carolina Edward R. Smith, MD Assistant Professor Department of Neurosurgery Harvard Medical School Attending Neurosurgeon The Children’s Hospital, Boston Boston, Massachusetts David L. Staffenberg, MD Associate Professor Department of Clinical Plastic Surgery, Neurological Surgery, and Pediatrics Albert Einstein College of Medicine, Yeshiva University Montefiore Medical Center, Children’s Hospital at Montefiore Bronx, New York Timothy A. Strait, MD Clinical Assistant Professor of Surgery Department of Surgery University of Tennessee College of Medicine– Chattanooga Unit The Neurosurgical Group of Chattanooga Chattanooga, Tennessee
Elizabeth C. Tyler-Kabara, MD, PhD Assistant Professor Department of Neurological Surgery University of Pittsburgh School of Medicine Division of Pediatric Neurosurgery Children’s Hospital of Pittsburgh Pittsburgh, Pennsylvania Marion L. Walker, MD Professor Department of Neurosurgery University of Utah School of Medicine Division of Pediatric Neurosurgery Primary Children’s Medical Center Salt Lake City, Utah Jack Chungkai Yu, MD, DMD, MS Ed Department of Surgery Section of Plastic and Reconstructive Surgery Medical College of Georgia Augusta, Georgia
1 Fibrous Dysplasia Involving the Craniofacial Skeleton James Tait Goodrich This chapter will deal with fibrous dysplasia of the craniofacial complex, in particular those regions involving the forehead, orbital rim, lateral and medial orbital walls, the orbital roof, and the optic foramen. The discussion will involve the “worst case scenario,” assuming that, if the surgeon can handle this type of case, the simpler cases will be easier to treat. Fibrous dysplasia can involve the calvaria and any of the upper facial bones. Its etiology is unknown, but the pathology involves a replacement of normal bone with a fibroosseous matrix. The surgical principle involves removing all of the dysplastic bone (or as much as possible) and replacing it with normal calvarial bone harvested from other parts of the head. Fibrous dysplasia can be of a simple type called monostotic, where only one bone unit is involved, or polyostotic, where two or more bones are involved. In this chapter we will deal with the more complicated polyostotic type. The most common presenting complaints in fibrous dysplasia of the craniofacial complex are proptosis (Fig. 1–1), diplopia and headaches, and in severe cases, progressive
blindness due to optic nerve compression; fortunately, blindness is an extremely rare outcome. An x-ray film of the skull will show a sclerotic mass expanding the calvarial and orbital bones. The radiologist typically describes a “ground glass” appearance. There will also be sclerosis or even a cystic appearance to the bone. It is not uncommon to see complete obliteration of the frontal and nasal sinuses. The proptosis is secondary to the orbital fibrous dysplasia compressing the globe and forcing the eye forward. As a result of this, an early presenting complaint can be diplopia. The principle behind the surgical treatment of fibrous dysplasia of the craniofacial complex is threefold: (1) relief of optic nerve compression (decompression of the nerve should be considered though is not always essential); (2) removal of all dysplastic bone if possible, as any residual can form a new dysplastic center; and (3) use of the patient’s own bone for grafts to achieve a satisfactory cosmetic result is preferred. We now avoid the use of any foreign implantable materials such as methylmethacrylate, wire mesh, or metal fixation plates, particularly in children, due to high risk of migration and infection.
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A Figure 1–1 (A) Frontal view and (B) superior view of a patient with orbital proptosis secondary to fibrous dysplasia. Typical proptosis is evident and fibrous dysplasia involving the right orbital unit including
rim, lateral, and medial walls. As a result, the eye is pushed forward and downward. Interestingly, the only visual symptom was double vision: The visual acuity was normal.
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2 Pediatric Neurosurgery At the Craniofacial Center of the Children’s Hospital at Montefiore we now do as much as possible of the reconstruction with “normal” calvarial bone, that is, bone not involved with fibrous dysplasia. We have found this considerably lessens the risk of resorption, which occasionally occurs with rib grafts placed in the craniofacial region. The use of ribs, particularly in the forehead region, can sometimes lead to an unacceptable “washboard” appearance. Another advantage of using calvarial bone is the reduction in operative exposure. This technique also avoids the complications that can occur with rib harvesting, such as pneumothorax and chest wall pain.
Preoperative Preparation Evaluation All patients should have radiographic studies of the skull in the routine views to document the extent of dysplastic involvement of the skull and surrounding orbital and nasal structures. Computed tomography scanning with bone windows in the axial and coronal views along with threedimensional reformatting are obtained for the operative planning. We have not found magnetic resonance imaging to be helpful, so we do not use it routinely. If the optic nerve is compressed, we routinely do visual acuity and visual field testing to have baseline values. Damage to the optic apparatus and to the nerves supplying the extraocular muscles are the most significant complications to be avoided. Subtle damage may already have occurred preoperatively, and it is essential to document this prior to any surgical intervention. In recent years our ophthalmologic colleagues now feel it is no longer always necessary to decompress the optic nerve, even in cases of severe radiological compression. Some surgical teams now feel the risk of removing the dysplastic bone is too great in causing direct injury to the nerve. As a result of these recent discussions we no longer just routinely decompress the optic nerve. The exception is a rapid and clear progression of visual loss due to an overgrowth of dysplastic bone. We routinely start an anti-staphylococcal antibiotic at the time of anesthetic induction in the operating room. Because the surgical manipulations are extradural, we do not routinely use anticonvulsant medications.
pressure line. An arterial line is highly recommended for monitoring blood gases, hematocrit, electrolytes, etc., during the procedures. We request an osmotic diuresis, usually with mannitol (0.5 mg/kg) at the time of anesthetic induction. A spinal drainage system for cerebrospinal fluid (CSF) removal can sometimes also be helpful for brain relaxation. These relaxation measures can be key in getting a relaxed frontal lobe for retraction when working back toward the optic foramens. We do not routinely use steroids in these types of cases; the exception is if there is evidence of brain or optic nerve edema during the case.
Operative Procedure Positioning The patient is placed in the supine position with the head resting on a cerebellar (horseshoe) headrest (Fig. 1–2). The head is placed in a slightly extended, brow-up position. Rigid fixation devices such as a Mayfield clamp are specifically avoided, as the surgical team will need to move
Preparation Fibrous dysplastic bone can be, and usually is, highly vascular. As a result, the blood loss in these procedures can be significant. We routinely plan for a blood loss of 2 to 3 units. If the family wishes, we arrange for pedigree blood donations from family members 1 week in advance. The patient can also donate his/her own blood prior to surgery. If available, a “cell saver” unit can rescue up to 50% of the patient’s lost blood volume. Because of the risk of extensive blood loss, all patients require at least two large-bore intravenous lines of 16 gauge or larger. If there is any history of cardiac or pulmonary problems, we routinely put in a central venous
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10.1055/978-1-60406-039-3c001_f002 Figure 1–2 Schematic showing the location of the surgical and anesthesia teams.
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1 Fibrous Dysplasia Involving the Craniofacial Skeleton the head (usually never more than 10 to 15 degrees): This flexibility can prove to be very useful. We also like to reverse the operating room table so the head of the patient is at the foot end of the operating room table. This positioning allows the surgeon and assistant to sit with their knees comfortably under the table and not obstructed by the table pedestal or foot unit. Anesthesia equipment is placed on the side opposite the lesion and parallel to the table. Routine orotracheal intubation is performed. All lines are run off to the side of the anesthesia unit. The operating surgeon is placed at the head of the patient with the assistant to the side. The scrub nurse comes in over the patient’s abdomen but is positioned no higher than the mid-thoracic region. This allows the surgeon to be able to move around to see the patient’s face fully for cosmetic evaluation. For this reason we also avoid the use of bulky overhead tables, such as the Fallon table. If the patient has significant proptosis or the threat of injury to the globe is significant, then we place tarsorrhaphies just prior to formal surgical draping. This maneuver can be quite helpful in preventing any unintentional injury to the globe and cornea.
Surgical Draping The head is draped for a bicoronal incision. The hair is not shaved but is either parted for the incision or a small 1.5 cm width of hair is taken for the incision line. We also find it helpful to braid the hair if it is long to keep it out of the field. In children a zig-zag type of incision is made. We have found these incisions reduce the keloid formation over the temporalis muscle and also prevent the hair from parting directly over the incision when it is wet. The draping is done in such a fashion that both eyes are visible. The facial drape is placed over the nose and nares but well below the lower orbital rim. This allows the eyes to be visualized during the reconstruction. The rest of the draping can be done according to the surgeon’s preference. An important additional point is to keep the drapes reasonably loose, so that the head can be moved. We routinely run all our suction lines, cautery cords, etc., past the foot of the patient. As both surgeons are sitting, this allows easy mobility of the chair; that is, they are not rolling over the cords and tubes. Because the operative site is usually copiously irrigated during the procedure, it is important to have waterproof outer drapes. Some of the recent drape designs provide a large plastic bag for fluid collection: We have found these to be quite useful.
Skin Incision Over the years we have used several different incisions but now almost always routinely use a bicoronal incision carried from ear to ear. The incision is started behind the ear helix, not in front (as is typically the case with most surgeries), to reduce scarring. The incision, particularly in children, is done in a zig-zag fashion until reaching the vertex, where it is straightened. The incision is made well behind
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the patient’s hairline, not at the hair edge, a common error in placement. This incision type allows for an extensive exposure of the calvaria for tumor removal and additional bone harvesting as necessary. In addition a large sheet of pericranium is available for any repairs of dura or frontal sinuses.
Flap Elevation A full-thickness flap is turned following the standard subgaleal plane. It is important to leave the pericranium intact. The pericranium is then elevated as a second separate layer. The flaps are carried down to the orbital rim to the level of the supraorbital nerve and artery. These structures are frequently encased in a small notch of bone. This notch can be opened with a small Kerrison rongeur or osteotome. It is easier to elevate the artery and nerve with the pericranial layer. It is important to preserve these structures or there will be anesthesia, or even worse dysesthesia, in the forehead postoperatively. The flap must also expose the entire belly of the temporalis muscle and the zygomatic arch. In the midportion of the face the nasion suture should be fully exposed. Using the small periosteal dissector or a Penfield dissector it is possible to come under the orbital rim and dissect it safely back ~1 to 2 cm. The temporalis muscle has to be elevated as a unit. Starting at its squamosal insertion, it is elevated using a Bovie electrocautery with a fine needle tip. The dissection is performed in such a fashion that the temporalis muscle will be elevated from the frontozygomatic suture back to the ear, fully exposing the pterional “keyhole.”
Craniotomy The craniotomy is performed to incorporate all of the dysplastic bone in the removal. It is easiest to do the frontal craniotomy by first taking out a forehead bone flap that encompasses as much of the forehead dysplasia as possible (labeled A in Fig. 1–3). This provides the window that will allow exposure to the orbital roof and walls. We prefer to use a high-speed drill system with a craniotome (e.g., Midas Rex with a B-1; Medtronic Inc. footplate [Fort Worth, Texas]) as this gives a speedy bone removal, thereby decreasing blood loss. In some cases the dysplastic bone can be extremely thick and we will use an S-1 attachment. We next elevate the frontal lobe with gentle retraction to see how far into the orbital roof the dysplastic bone extends. Then, by further dissecting under the orbital roof, the dysplastic portion can be completely visualized (Fig. 1–4). There is usually extensive blood supply crossing these planes, so the bleeding can be quite copious. Keep plenty of Avitine and Gelfoam available for packing in these spaces to control the oozing. Once the limits of the dysplastic bone have been determined and the brain is adequately relaxed and retracted, we proceed with the bone resection. Using a combination of osteotomes and a small cutting bur, such as the Midas Rex C-1 attachment, the roof is removed as a unit (Fig. 1–4). It is helpful to have the assistant place a malleable retractor under the orbital roof. This will prevent the drill or osteotome from damaging the perioribita. On occasion, the dysplasia can go back to the
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4 Pediatric Neurosurgery
Figure 1–3 Frontal view showing four-piece bone removal. (A) Frontal bone maximally involved with fibrous dysplasia; (B) lateral orbital wall; (C) medial orbital wall. The orbital wall roof, which is also removed, is not shown in this drawing. (D) Graft site from the opposite calvaria. 10.1055/978-1-60406-039-3c001_f003
clinoids and orbital foramen. In these cases, an operative decision has to be made in regards to the orbital nerve—leave the foramen alone or unroof it (Fig. 1–4) A small diamond bur on a high-speed drill unit is the best method for removing this part of the bone. Copious irrigation is applied to prevent any unnecessary thermal injury to the bone and nerve. Once this is completed, attention is turned to the lateral orbital wall and zygoma (labeled B in Fig. 1–3). This portion of the procedure can be done quite easily. The only important points are to have adequate exposure of the zygomatic arch and a good dissection of the orbit. The lateral canthal ligament must be sectioned and then reattached at the end of the procedure. We often place a suture through the canthal ligament for later identification. Doing this prior to the medial part will allow easy mobilization of the eye and surrounding structures with minimal trauma. Next, attention is turned to the most difficult phase— resecting the medial nasal structures (labeled C in Fig. 1–3). By removing the orbital roof and lateral orbital wall, the surgeon now has some mobility and freedom in the moving the globe. If the dysplastic bone involves the nasal bone and medial orbital wall, the medial canthal ligament is identified with a ligature and then cut. The assistant then retracts the eye laterally, and the bone is removed with an osteotome and
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Figure 1–4 Schematic drawing showing the frontal fossa after removal of the dysplastic orbital roof and decompression of the optic nerve at the foramen. 10.1055/978-1-60406-039-3c001_f004
fine cutting bur. The frontal sinuses are often obliterated with dysplastic bone, which can complicate matters. If the sinuses are not occluded, the frontal sinus can be entered and used as an operating space within which to work. Once all the dysplastic bone is removed, the reconstruction is started.
Some Helpful Hints On occasion, the dysplastic bone can be extremely thick, in one case more than 8 cm in thickness, which exceeds the cutting width of any known craniotome. In these cases one can just shave the bone down with a large bur. The other option is to put a long, fine cutting tip on a short attachment and then gently cut the bone. The disadvantage is one cannot see deep into the craniotomy so the craniotomy is all done by feedback to the fingers. Careful attention has to be focused on the midline structures such as the sagittal sinus. We have also found on occasion the dura can also be very dysplastic and densely adherent to the overlying bone. It can be extremely tedious to remove the dura from the dysplastic bone and care must be taken to avoid disrupting large veins that commonly run through the dura. On a couple of occasions serious air embolisms have occurred, and the anesthesia and surgical teams need to prepare to ag-
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1 Fibrous Dysplasia Involving the Craniofacial Skeleton
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gressively deal with an air embolism as these are potentially life-threatening situations if not treated rapidly.
Calvarial Bone Harvesting By using a bicoronal skin flap, typically a large amount of normal calvarial bone can be exposed. Once the surgeon has resected the dysplastic bone and determined how much bone is needed to reconstruct the defect, a craniotomy is performed on the opposite calvaria (labeled D in Fig. 1–3). Remember that the most useful bone is over the convexity, where the diploë is well formed. In the squamosal area, the bone thins out and is harder to split. The bone is taken to a sterile table set up next to the operating field. Using a combination of small osteotomes, a fine cutting tip such as a Midas Rex C-1, and a reciprocating saw, the bone is split along the diploic space. Copious irrigation is essential to prevent thermal injury to the bone; dead or necrotic bone does not heal well. Once the bone has been split, the inner table of the calvaria is placed back in the harvest site. The outer table, because of its smooth contours, is used as the reconstructing bone.
Craniofacial Reconstruction The reconstruction is done in the reverse order from the resection. The medial orbital wall is constructed first and plated into position (labeled C in Fig. 1–5). The nasal bone and cribriform plate are usually the most solid structures to work with. The medial canthal ligament also has to be reattached, which can be done easily through a small drill hole. Next, a piece of bone is fashioned to form the orbital roof. This is an important structure that must be solidly placed (Fig. 1–6). If it is not, subsequent proptosis (sometimes enophthalmos, too) of the eye can occur due to downward pressure of the frontal lobe. The bone used to reconstruct the lateral orbital wall is attached to the roof with either wires or miniplates (labeled A in Fig. 1–5). The squamosal portion of the temporal bone can also act as an excellent place to anchor this bone. The orbital rim is then fashioned 10.1055/978-1-60406-039-3c001_f005
Figure 1–6 Schematic drawing showing the split-thickness calvarial bone graft in position in the orbital roof region. This bone unit is key to preventing an unacceptable eye migration. 10.1055/978-1-60406-039-3c001_f006
and attached medially to the nasal unit and opposite orbital rim (labeled B in Fig. 1–5). This is the key cosmetic unit and must be perfectly placed to avoid facial asymmetry. The rest of the craniotomy is then closed in a mosaic fashion using the remaining pieces of bone. Miniplates have proved to be extremely useful in stabilizing these various bone units. In children and adolescents we now routinely use the absorbable plating systems (Figs. 1–7 and 1–8).
Repair of Frontal Sinus One of the most devastating postoperative complications is infection arising from the sinus. If the frontal sinus is not obliterated by dysplastic bone, it must be cleaned and exenterated of mucosal lining. We routinely cover the sinus with the pericranial flap to isolate it from the epidural space. The same principle applies to the other paranasal sinuses if they are violated.
Pericranial Tissue Figure 1–5 Schematic drawing showing the harvested bone grafts in position.
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The pericranial tissue is a most useful repair structure. It not only provides additional vascularity to the bone, but it also helps smooth out the rough contours of the bone that
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6 Pediatric Neurosurgery Use of Dysplastic Bone in Repair In some cases, if there is a shortage of bone for the repair, the dysplastic bone can be reused. The dysplastic bone must be firm, if not hard, with no soft or mushy spots present. In some cases we have found the dysplastic bone to be nearly as firm as normal bone and have reused it in the reconstruction. In some cases, where there is extensive fibrous dysplasia, one has no choice but to reuse the original diseased bone. However, the caveat remains: If normal bone is available, this is the better option to use.
Closure
Figure 1–7 Intraoperative view showing the harvested bone grafts in position.
The closure is done in a routine fashion. Hemostasis must be meticulous because of the amount of dead space that can form. In some, but not all, cases a subgaleal drain to light suction is placed for 24 to 48 hours. A fluid collection next to sinus spaces can lead to a devastating postoperative infection. Scalp closure is done in a routine fashion closing both the subgaleal and skin layers.
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has been harvested and used as grafts. Therefore, we make every effort to use this structure and place it back into its natural anatomical position.
Temporalis Muscle To prevent a postoperative depressed concavity over the temporal unit, the temporalis muscle is laid back into position. Sometimes a relaxing incision must be made posteriorly to allow the muscle to be advanced forward to cover the keyhole and to be reattached to the zygoma. This is critical or there will be a significant “hourglass” deformity over this region postoperatively.
Figure 1–8 Postoperative photograph taken 6 weeks after surgery showing aesthetic reconstruction obtained.
Postoperative Management Including Possible Complications We routinely place the patient on antibiotics to cover skin organisms and possible nasal contaminants for at least 72 hours. The risk of osteomyelitis is high and can be quite devastating to the patient, so every attempt must be made to avoid it. There may be significant periorbital swelling postoperatively; ice packs are applied to the eye and periorbital region for symptomatic relief. If there is significant swelling at the end of the operation, we ordinarily leave the tarsorrhaphy in place for about 2 days. Intensive care for at least 48 hours is mandatory with close monitoring for hemodynamic changes from excessive blood loss and for the development of an epidural hematoma. The neurosurgeon must always be attentive to postoperative CSF leaks. If dural tears have occurred, they must be repaired meticulously. Should a postoperative CSF leak occur, then placement of a lumbar CSF drain may be necessary to divert the fluid. These drains usually need to be left in place for 5 to 7 days. However, close attention to dural tears and verifying dural integrity by asking the anesthesiologist to perform a sustained Valsalva maneuver at the end of the case should prevent this problem from occurring. Acknowledgment This chapter is a revision of the chapter, “Fibrous Dysplasia Involving the Craniofacial Skeleton” by James T. Goodrich, M.D. and Craig D. Hall, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 1, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Craig Hall, M.D., for his help and efforts on the original chapter published in the first edition of this work.
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2 Chiari Malformations and Syringohydromyelia Elizabeth C. Tyler-Kabara and W. Jerry Oakes Chiari malformations, or hindbrain hernias, are being diagnosed and operated upon with increasing frequency. For the purposes of this chapter, two separate entities will be discussed. The Chiari I malformation is characterized by caudal descent of the cerebellar tonsils. The brain stem and neocortex are typically not involved and the patient does not suffer from a myelomeningocele. Syringomyelia is commonly but not invariably present. The Chiari II malformation is almost always seen in conjunction with spina bifida and is a more severe form of hindbrain herniation. The neocortex and brain stem are dysmorphic and the cerebellar vermis (not the tonsils) is displaced into the cervical spine. Accompanying the vermis are dysmorphic and elongated aspects of the medulla and lower pons as well as the lower aspect of the fourth ventricle. Again, syringomyelia is commonly associated with this lesion. Not discussed in this chapter is the rare Chiari III malformation.
Chiari I Malformations Patient Selection With the advent of magnetic resonance imaging (MRI) the detection of caudal displacement of the cerebellar tonsils and the presence of an associated syrinx has become safe and accurate. Typically the tonsils are at least 3 mm below the plane of the foramen magnum. They lose the rounded appearance of their caudal pole and become pointed or “peg-like.” This is associated with obliteration of the subarachnoid space at the craniocervical junction with the impaction of tissues into this confined region. When all of the above criteria are not met, the situation should be judged in conjunction with the clinical symptomatology of the patient. The presence of syringomyelia or other developmental anomalies will further assist in the interpretation of the intradural findings at the craniocervical junction. Patients with a symptomatic Chiari I malformation are generally offered operative intervention. The more severe the neurological deficit, the stronger the case for intervention. When occipital pain is the only symptom and no neurological signs are present, the degree of disability from the discomfort should be carefully weighed against the risks of the procedure, prior to the implementation of surgical intervention. With advances in cine MRI, some patients with occipital headaches and mild hindbrain hernias have been
found to have abnormal cerebrospinal fluid (CSF) flow at the craniocervical junction. When syringomyelia is present, we generally favor intervention even with minimal symptoms. The absence of caudal displacement of the cerebellar tonsils but with a “compressed look” to the tissues at the foramen magnum associated with a significant syrinx has been termed a Chiari 0. When the syrinx is significant, the Chiari 0 patient should be considered for decompression. Intracranial pressure should be normalized prior to consideration of craniocervical decompression. Approximately 10% of patients with Chiari I malformation will have hypertensive hydrocephalus, and ventriculoperitoneal shunt insertion should precede other considerations. Flexion and extension views of the cervical spine are also important to resolve questions of spinal stability and other bony anomalies. If significant basilar invagination or retroflexion of the dens is present, the need for an anterior decompression should be discussed prior to proceeding with a posterior procedure. If the posterior procedure is performed first, it should be recognized that acute neurological decompensation postoperatively warrants emergent anterior decompression.
Preoperative Preparation Once a candidate for surgery has been appropriately chosen, the patient is prepared with preoperative antibiotics. The patient is positioned prone (Fig. 2–1) in a pin-type head holder with the neck flexed. The head of the table is elevated somewhat, but no central venous access is mandatory because lowering the head will eliminate the gradient for air embolization. A chest Doppler monitor may be used for the detection of air embolization and to monitor slight changes in the patient’s pulse. Patients are paralyzed and are not allowed to breathe spontaneously. This significantly lowers the likelihood of serious pulmonary complications postoperatively. Muscle relaxants are allowed to become fully effective during the induction of anesthesia to avoid the Valsalva maneuver during placement of the endotracheal tube. A severe Valsalva maneuver has been associated with progression of symptoms in some patients.
Operative Procedure The skin incision is made from a point 2 cm below the external occipital protuberance to the midportion of the
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Figure 2–1 Optimal positioning of a patient for exposing a Chiari malformation. 10.1055/978-1-60406-039-3c002_f001
spinous process of C-2 (Fig. 2–2A). It is quite unusual for the tonsilar tissue to descend below the level of the upper portion of C-2 (Fig. 2–2B), and by preserving the important muscular attachments at C-2 postoperative pain is significantly decreased. The likelihood of postoperative spinal deformity seen in conjunction with syringomyelia is also substantially lessened. The avascular midline plane of the occipital musculature is divided with monopolar current. No incision transecting muscle is necessary in this procedure because the plane dividing the left and right muscular bundles completely separates these two groups. A small amount of fat will mark this natural cleavage plane. Again using the monopolar current, the muscle insertion immediately above the foramen magnum is separated from the occipital bone and the posterior arch of C-1. First the occipital bone is removed followed by the arch of C-1 (Fig. 2–2C). There is no need for lateral exposure, and bone laterally situated is left intact. This minimizes the risk of injury to the vertebral veins and arteries. The bone edges are waxed, and the dura is opened in the midline. Initially, the dura over C-1 is opened. Care is taken as the incision is extended across the circular sinus near the foramen magnum. This sinus can be formidable and should not be ap-
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proached nonchalantly. With the dura retracted laterally, the arachnoid is opened in the midline. The subarachnoid adhesions are lysed with a sharp instrument and are not simply torn. The arachnoid edge is then clipped to the dural edge with metal clips. The tonsils, which can be recognized by their vertical folia, are separated in the midline to expose the floor of the fourth ventricle (Fig. 2–2C). Care is taken to free the caudal loop of the posterior inferior cerebellar artery and to avoid damage to this vessel or its branches. Again adhesions are cut rather than torn. On separating the cerebellar tonsils, a veil of arachnoid is sometimes encountered. This veil should be opened widely. Obstruction to CSF flow can also occur from the posterior inferior cerebellar arteries. These vessels may approximate in the midline and be adherent to one another. They should be separated and mobilized laterally with great care. Closure is then accomplished with a generous dural graft. We prefer to use the patient’s own pericranium, but either cadaveric or artificial dural substitutes may be used. The dural closure is with absorbable suture, which is known to react minimally in the subarachnoid space. A Valsalva maneuver is performed to check for CSF leaks prior to closing the wound in multiple layers.
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Postoperative Management Including Possible Complications Following the operation, patients may experience some nausea and vomiting as well as hiccups. These are almost always self-limited. Neurological deficits that are wellestablished prior to the operation are unlikely to reverse following manipulation. Long-standing pain and temperature loss is very unlikely to return. Hand and arm weakness with fasciculations and loss of muscle bulk may improve functionally but may not normalize. A particular problem exists when pain is a major component of the presentation. Children and adolescents infrequently have a major problem with pain. Adults, however, may be quite discouraged by the persistence of discomfort in the neck, shoulders, and/or arms. Pain may very well persist despite a physiologically
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Figure 2–2 (A) Schematic of incision placement and bone work for operative exposure of a Chiari I malformation. (B) Chiari I malformation associated with syringomyelia, midline sagitttal section. (C) Operative exposure of a Chiari I malformation with the floor of the fourth ventricle exposed.
successful operation with obliteration of the syrinx cavity. This limitation of surgical intervention should be carefully explained to the patient prior to surgery. Mild scoliosis (less than 35 degrees) may improve or simply stabilize, whereas more severe spinal deformity may well progress despite adequate treatment. With the advent of MRI scanning the status of syringohydromyelia can be assessed easily. If a sizable syrinx persists months to years after craniocervical decompression, a second decompression should be considered. It is our experience that >85% of children will have resolution of their syringes following a simple craniocervical decompression. If the syrinx persists for 9 to 12 months following the initial decompression or if there is a return of symptoms and a syrinx that had once shown evidence of decompression, then consideration should be given to a secondary decompression. During this secondary procedure
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10 Pediatric Neurosurgery one or both cerebellar tonsillar tips are resected to allow an unimpeded expansion of the foramen of Magendie. With this second intervention the vast majority of the recurrent and persistent syringes will resolve. If after two decompressions a larger syrinx is persistent and symptoms attributable to this lesion are serious or progressive, consideration can be given to a laminectomy over the lower aspect of the syrinx and the placement of a syrinx to subarachnoid shunt or a syrinx to peritoneal shunt. If a syrinx to subarachnoid shunt is chosen, placement of the distal catheter in the free subarachnoid space is an important technical maneuver. Catheters can easily be mistakenly placed in the subdural space without benefit to the patient.
Chiari II Malformations Patient Selection Children with myelomeningocele may develop symptoms referable to their hindbrain hernias. Symptoms and signs are generally age-specific, with infants developing lower cranial nerve disturbances (difficulty with swallowing, weak cry, inspiratory wheeze, aspiration pneumonia, absent gag, and opisthotonos) and older children more commonly developing progressive upper extremity spasticity. Ataxia of the trunk or appendages is recognized much less often. Because some degree of hindbrain herniation is present in the vast majority of spina bifida patients, MRI evidence of hindbrain herniation must be accompanied by progressive or significant symptomatology to warrant operative intervention. Many patients will remain clinically stable for long periods despite significant anatomical deformity. As many as one-third of patients will develop difficulty with phonation, swallowing, or apnea by age 3 years. If the “asymptomatic” remainder were followed for a longer period or if less serious symptoms were considered significant, this one in three figure would undoubtedly be higher. Because the symptoms of the Chiari II malformation are frequently life-threatening, symptomatic Chiari II malformation is the leading cause of death in the treated myelomeningocele population today. When treated conservatively, as many as 5 to 10% of all patients will die from the malformation by the age of 3 years. The decision for surgical intervention is controversial. Because there is a significant likelihood of stabilization or actual improvement with conservative care, some would argue against operative intervention. This is supported to some degree by autopsy material that demonstrates hypoplasia or aplasia of vital lower cranial nerve nuclei. Against this, however, is the experience of numerous surgeons who have seen dramatic improvement in many patients following decompression. In addition, objective evidence of physiological functioning has been reported to improve with both brain stem evoked responses and CO2 curve following operation. With these conflicting pieces of evidence one can quickly appreciate the surgeon’s dilemma. With increasing experience, the senior author’s willingness to operatively intervene is increasing. This is due to the
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relatively low incidence of operative complications and the clear improvement demonstrated by some patients. Poor results are more commonly due to a delay in offering operative intervention. Once serious difficulties are clinically evident with breathing, swallowing, or phonation, the situation may very well be irreversible. In that case, the best outcome that surgery can be expected to yield is maintenance of the poor level of lower cranial nerve function seen immediately prior to operation. Problems with aspiration pneumonia, apnea, and other life-threatening difficulties may very well persist. The solution to this problem does not seem to be a continuation of a conservative approach, accepting 10 to 15% mortality. Rather, an earlier identification of patients at high risk for serious problems, and offering this group intervention, seems to be a more logical option. Being able to detect this high-risk group prior to the development of irreversible life-threatening problems is a key provision. If serious problems with phonation, swallowing, or breathing are detected and normal intracranial pressure is present, urgent intervention is appropriate when full support of the child is proposed. It is also important to emphasize that normalization of intracranial pressure is a prerequisite to consideration of craniocervical decompression. Patients with questionable shunt function are well served to first have their shunts revised. If progressive or serious symptoms persist after adequate shunt revision, decompression of the craniocervical junction can be contemplated. Again, the MRI has made the diagnostic evaluation of this group of patients almost risk-free and quite precise.
Preoperative Preparation As with the Chiari I patients, preoperative antibiotics are given. The anesthetic management and positioning of the patient are similar to those for the Chiari I patient. Of some difference, however, is the fact that decompression should extend to the level of the caudally displaced posterior fossa tissue. This is frequently below the level of C-4. By removing this additional bone and displacing the musculature, the risks of cervical deformity are substantially increased even if the laminectomy is kept quite medial, preserving the facets. Because the lower portion of the fourth ventricle is usually not within the posterior fossa, the occiput may need to be removed minimally if at all (Figs. 2–3A and 2–3B). If it is elected to open the dura over the posterior fossa, great care is necessary. The transverse sinus in the patient with spina bifida is frequently placed near if not at the level of the foramen magnum (Fig. 2–3B). An unknowing opening of the dura and sinus in this area may well lead to an operative disaster. The elasticity of the tissues of the cervical spine is pronounced. In removing the laminal arch of small infants, each bite with the rongeur needs to be crisp and clean. Undue distortion of the spinal cord may occur if this principle is not followed. It is important to study the preoperative MRI for the position of the fourth ventricle, the cerebellar vermis, and the possibility of a medullary kink. The position of all these structures is critical to the intradural exploration.
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C Figure 2–3 (A) Schematic of incision placement and bone work for operative exposure of a Chiari II malformation. (B) Chiari II malformation, midline sagittal section. (C) Operative exposure of a Chiari II malformation before and after the floor of the fourth ventricle is exposed. 610.1055/978-1-60406-039-3c002_f003
Operative Procedure Once the dura is opened, finding the caudal extent of the fourth ventricle can be difficult (Fig. 2–3C). Intraoperative ultrasound may be of help in localizing this structure. The
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choroid plexus usually maintains its embryonic extraventricular position, marking the caudal end of the fourth ventricle. When present, this is a reliable intraoperative marker. Unfortunately, dense adhesions and neovascularity at points of compression or traction may be found, especially near
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12 Pediatric Neurosurgery C-1, and this may make dissection treacherous. The fourth ventricle may be covered by vermis with its horizontal folia, or the choroid plexus may simply lie within the displaced ventricle. The purpose of the intradural manipulation is to open the fourth ventricle and provide free egress of CSF from the fourth ventricle. It is necessary to find and open the tissue widely over the caudal aspect of the fourth ventricle. It may happen that several planes of dissection are developed before the floor of the fourth can be adequately appreciated. It is important during the exploration of each of these avenues that vascular and neural tissues be preserved and that natural planes are developed so that no irreparable damage to the delicate tissues of the lower brain stem occurs. The caudal aspect of a medullary kink can easily be mistaken for the appropriate target. This dissection is one of the most difficult in pediatric neurosurgery. Errors or simple tissue manipulation may convert a tenuous portion of the medulla or lower pons to permanently damaged tissue. The surgeon should always bear in mind the risk-benefit ratio for each of his or her actions, as this particular area is unforgiving of even small excesses of manipulation. Grafting of the dura and closure are similar to the previous description.
Postoperative Management Including Possible Complications Following the operation, patients may experience some nausea and vomiting as well as hiccups. These are almost always self-limited. Neurological deficits that are well-
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established prior to the operation are unlikely to reverse following manipulation. With the advent of MRI scanning the status of syringohydromyelia can be assessed easily. If a sizable syrinx persists months to years after craniocervical decompression, a second decompression should be considered. If after two decompression a larger syrinx is persistent and symptoms attributable to this lesion are serious or progressive, consideration can be given to a laminectomy over the lower aspect of the syrinx and the placement of a syrinx to subarachnoid shunt or a syrinx to peritoneal shunt. If a syrinx to subarachnoid shunt is chosen, placement of the distal catheter in the free subarachnoid space is an important technical maneuver. Catheters can easily be mistakenly placed in the subdural space without benefit to the patient.
Conclusion In addition to the avoidance of problems with infection, hemorrhage, and increased neurological deficit, patient selection and the timing of intervention are critical to the successful outcome of decompressing a patient with a Chiari malformation. Despite what was thought to be appropriate and timely intervention, an alarmingly high percentage of patients with lower cranial nerve abnormalities treated surgically eventually progress. This raises the question of whether the current strict selection criteria are too restrictive and whether less symptomatic infants should be considered for decompression. This area of speculation remains in dispute.
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3 Unilateral and Bicoronal Craniosynostosis Kant Y. K. Lin, John A. Jane Jr., and John A. Jane Sr.
Coronal craniosynostosis is defined as the premature fusion of the coronal suture(s) of the skull; sutural involvement may be either unilateral or bilateral. Because of the position of the coronal suture, the consequences of premature fusion are manifested in the calvaria as well as in the face. As with all forms of craniosynostosis, compensatory growth occurs at the adjacent nonaffected suture sites. This is evident in cases of unilateral involvement at the contralateral coronal suture, where the contralateral side of the metopic and sagittal sutures, and at the ipsilateral squamosal suture growth leading to a unilateral anterior plagiocephaly (Fig. 3–1). In bilateral involvement, compensation is noted at both squamosal sutures, as well as at the sagittal suture leading to an overall turribrachycephalic or “tower-shaped” appearance (Fig. 3–2). With the resulting skull shapes being so disparate, operative treatments must be geared toward different issues, and the two types will be discussed separately. Coronal craniosynostosis may be associated with elevated generalized intracranial pressure. The likelihood of this occurrence increases when more than one suture is involved. Bilateral coronal craniosynostosis in often associated with craniosynostosis syndromes, such as Crouzon’s or Apert’s syndrome. A distinction must be made between the syndromic and nonsyndromic varieties as management and expectations of outcome differ between the two.
Patient Selection Diagnosis is based on the characteristic medical history and physical examination. Confirmation and more precise delineation of the dysmorphology are obtained from computed tomography of the skull. In particular, three-dimensional reconstruction of the images is useful for presurgical planning. A thorough ophthalmologic examination is indicated both for purposes of detecting intracranial hypertension, as well as to document any orbital axis issues related to the changes in the bony orbit secondary to the stenotic adjacent coronal suture. Often an eyelid ptosis or extraocular muscle imbalance is seen and must be addressed, usually after the bone deformities are corrected. Increasingly sophisticated DNA mapping techniques have resulted in an additional method of diagnosis that is especially useful with inherited forms of coronal craniosynostosis, or when a craniosynosotosis syndrome is involved.
Indications and Timing of Surgery Indications for surgical correction of a unilateral deformity are improvement of overall skull shape with advancement of a recessed forehead and correction of the bossed contralateral forehead, correction of the orbital dysmorphology, which can subsequently allow for correction of the orbital adnexal structures, and possible relief of either generalized or localized intracranial hypertension. Indications for surgical correction of the bilateral deformity are similar but also include the need to correct the overly high or tower-shaped skull and the overall brachycephaly. Diagnosis of intracranial hypertension can be difficult and is based on “soft” findings such as cerebral markings seen on the inner calvarial table (“copper-beaten” appearance) on plain x-rays, or by late fundoscopic changes seen by slit lamp evaluation. Earlier signs suggestive of increased pressure may be seen with subtle behavioral changes in the child, or with a bulging anterior fontanelle. In the final analysis, a monitoring bolt is needed to accurately record pressures intracranially. Any evidence of elevated pressures is an indication for a more urgent need for surgery. Although controversial, most surgeons would agree that surgery is best performed before the child has reached the age of 1 year. Our tendency is to perform surgery closer to 6 months of age. Because the volume of the brain almost triples in the first year of life, it would seem prudent to allow the intracranial cavity to accommodate this rapid growth through earlier surgery. The correction should certainly be performed before brain damage has occurred; often, subsequent brain growth can be utilized to help direct future growth and maintain the newly corrected skull and orbit shape following suture release and bony recontouring. Earlier correction also spares the child emotional or psychological trauma over his/her appearance, before the age of self-awareness (5 years or younger).
Preoperative Preparation Once the decision has been made to proceed with surgery, a preoperative workup consisting of routine blood tests, including a complete blood cell count, electrolyte panel, and a pro-time and prothrombin time, are performed. Because of the potential for significant blood loss, a type and screen
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14 Pediatric Neurosurgery are obtained and compatible donors among relatives are encouraged to donate for donor-directed intra- and perioperative transfusions. The child is brought to the hospital on the day of surgery having been kept NPO for 4 hours prior to the anticipated start time for surgery. At least two large-bore (≥20 gauge) intravenous lines are required for access due to the potential for significant blood loss or fluid shifts during surgery. An arterial line is placed and a central line is also helpful to monitor the total body intravascular volume for both operative and postoperative fluid management. A Foley catheter is useful to record urinary output, and a thermistor is used to record core body temperature. A Doppler monitor is placed over the heart to monitor blood flow and is used to detect the possibility of unanticipated intraoperative air embolism. Steroids and anticonvulsants are not routinely used. Prophylactic antibiotics are given just prior to the incision. In young children, the hair is clipped to allow the surgeon full visualization of the degree of the skull deformity, so that the surgical correction can be tailored accordingly. This also helps facilitate the scalp closure and postoperative wound care by the nursing staff and the parents. Once the intraoral endotracheal intubation has been performed, we have found it helpful to secure the tube with either a circummandibular or a circumdental wire, thus obviating the need for taping and allowing full access to the face during surgery. Temporary tarsorrhaphy sutures are also placed for intraoperative corneal protection.
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Operative Procedure Positioning
B Figure 3–1 Skull deformity in unilateral coronal synostosis. The ipsilateral forehead is flattened and the superior and lateral orbital rims are recessed. (A) Compensatory growth (depicted by arrows) occurs at adjacent sutures. Compensatory growth at the metopic and contralateral open coronal sutures causes unilateral frontal bossing. Growth at the sagittal and open coronal sutures leads to a contralateral parietal bulge. (B) Skull-base deformity along the anterior cranial fossa also occurs. 10.1055/978-1-60406-039-3c003_f001
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The patient with unilateral coronal synostosis is placed in a supine position on the operating table with the head resting in slight extension in a Mayfield headrest. The patient with bilateral coronal synostosis is positioned differently, the details of which will be discussed separately from the unilateral deformity. The headring is reinforced with additional soft padding to prevent excessive pressure over bony prominences during the lengthy procedure. The scalp and face are prepped with Betadine (providone-iodine) solution, with emphasis placed on scrubbing the external auditory canals, which tend to colonize with bacteria. The head, face, and neck are then draped to the clavicles, and staples are used to secure the drapes. A 180 degree access to the head and facial region is required, and the surgical table is rotated so that the anesthesiologist is positioned at the patient’s side at the foot level. The nursing staff and all instrumentation, which has been placed on a single large table, is positioned opposite the anesthesiologist, who is also at the foot of the bed. A smaller Mayo stand is positioned over the patient’s abdomen, and only those instruments most currently in use are kept for ready access.
Skin Incision and Flap Elevation A standard wavy bicoronal incision is performed extending from just behind one ear across to the opposite side. Care is
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10.1055/978-1-60406-039-3c003_ Figure 3–2 Skull deformity in bilateral coronal synostosis. Bilateral coronal synostosis leads to significant bilateral forehead flattening (with a decrease in the overall anteroposterior dimension of the skull) and re-
taken to make the incision posterior to the anterior hairline, yet forward enough to allow for access to the orbital region once the scalp flap is dissected. The scalp flap is elevated anteriorly down to the level of the supraorbital rim. The supraorbital neurovascular bundle is preserved and may occasionally need to be freed from its foramen with a thin osteotome. Dissection is then extended laterally down each lateral orbital rim detaching the lateral canthi to the junction with the inferior orbital rim, and medially up to, but not detaching, the insertion of the medial canthal tendons. The nasolacrimal apparati are also carefully preserved. The nasion is exposed during this part of the dissection as well. Inferolaterally, the anterior aspect of the maxilla, the malar eminence, and the anterior aspect of the zygomatic arch are also exposed. The temporalis muscles are elevated off their insertions and left attached to the undersurface of the scalp flap, thus allowing access to the infratemporal hollow. The temporal and sphenoid bones are exposed from the lateral orbital rim close to the junction where the zygomatic arch meets the posterior temporal bone. This area will allow the formation of a tenon extension, once the orbital osteotomies are performed, of the supraorbital bone unit that will be advanced and reshaped to compensate for the temporal narrowing seen in this condition.
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cession of the orbital rims. Compensatory growth (depicted by arrows) at the squamosal suture causes vertical elongation of the skull. Growth at the sagittal suture causes the skull to widen.
Craniotomy and Craniofacial Reconstruction Unilateral Coronal Craniosynostosis Emphasis has been placed on the concept that despite unilateral sutural involvement, the deformity is, in almost all cases and occasionally significantly, bilateral. Whereas the ipsilateral side reflects growth restriction, the contralateral side exhibits the effects of compensatory changes driven by the growth of the brain. A bifrontal craniotomy is performed with the posterior extent of the cuts being posterior to both the fused and nonfused coronal sutures and the anterior cut ~1 cm above the level of the supraorbital rims. Retraction of the frontal and temporal lobes of the brain is then performed, taking care to remain anterior to each olfactory bulb. Three-quarter orbital osteotomies are completed across the orbital roof, superior aspect of the medial orbital wall, lateral orbital wall, and the lateral aspect of the orbital floor into the inferior orbital fissure. Tenon extensions are made extending laterally into the sphenoid and temporal bones. The final remaining cut is made across the nasion just above the nasofrontal suture (Fig. 3–3). This forms a single orbital unit that is removed in its entirety to be reshaped. The remaining portion of the
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Figure 3–3 Craniotomy and orbital rim osteotomies for unilateral coronal synostosis. The surgery begins with a bifrontal craniotomy that includes both coronal sutures. Radial osteotomies are performed, and the frontal bone is recontoured. Bilateral three-quarter orbital osteotomies are then performed, elevating the visor as a single unit. Dotted lines depict areas of osteotomies.
Figure 3–4 Orbital rim reconstruction in unilateral coronal synostosis. During the reconstruction, the ipsilateral superior and lateral orbital rims are advanced and reshaped to match the contralateral side. The contralateral orbital rim often needs to be recessed by removing a portion of the contralateral tenon. A template of bicortical graft is then placed over the contralteral orbital rim and is used as an onlay graft for the ipsilateral orbital rim. Further reshaping of the ipsilateral rim often requires a combination of burring down the inner cortex of the orbital rims, thus softening them enough to use the Tessier bone benders. 10.1055/978-1-60406-039-3c003_f004
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abnormally shaped and positioned greater wing of the sphenoid bone is then carefully rongeured medially up to the fused frontosphenoid suture, and into the superior orbital fissure. This will allow for subsequent brain expansion behind the newly configured orbital unit. The goals for reshaping the orbital unit include: (1) advancement of the ipsilateral lateral orbital rim; (2) advancement of the retruded supraorbital rim in relationship to the inferior orbital rim in the anteroposterior (AP) plane; (3) recreation of the overall shape of the orbit to match the opposite orbit; and (4) recessment of the contralateral lateral orbital rim to take out any compensatory changes. These changes are effected by a combination of burring down the inner cortex of the orbital rims, thus softening them enough to use the Tessier bone benders to reshape the bone in the proper configuration. The recessed portion is given additional projection via advancement of the tenon extension along the lateral temporal bone. A portion of the distal end of the tenon extension on the contralateral side is removed to allow for recessing, again at the temporal bone region (Fig. 3–4). Finally, the retruded supraorbital rim and the reshaping of the orbital box are addressed simultaneously by placing an onlay bone graft, harvested from the bifrontal bone piece and fixed with an absorbable lag screw, over the deficient area and burred to the matching configuration of the opposite side (Fig. 3–5).
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Figure 3–5 Orbital rim reconstruction and advancement in unilateral coronal synostosis. The recessed portion is given additional projection via advancement of the tenon extension along the lateral temporal bone. A portion of the distal end of the tenon extension on the contralateral side is removed to allow for recessing, again at the temporal bone region. The onlay graft is fixed to the ipsilateral orbital rim with lag screws. In addition, a portion of the greater wing of the sphenoid is also removed up to the frontosphenoid suture and into the superior orbital fissure to allow for subsequent brain expansion into the previously constricted space. 10.1055/978-1-60406-039-3c003_f005
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3 The newly configured orbital unit is then returned to its original position, albeit advanced on the affected side and recessed on the opposite side, and secured with 2 mm thick resorbing plates and screws bridging the tenon extensions to the adjacent temporal skull. The segment of frontal bone is also reshaped through a combination of Tessier bone benders, inner and outer cortex burring, and barrel-stavenlike osteotomies to match the new curve of the supraorbital unit and to recreate a smooth and symmetric forehead. The segment can be rotated 180 degrees to use the more properly shaped curve of the posterior edge to match the curve of the supraorbital unit if needed. This segment can be secured with either resorbable plates and screws or even absorbing sutures to avoid any possibility of future growth restriction or transcranial migration of any fixation hardware (Fig. 3–6). To prevent early relapse of the deformity, we believe that firmer rigid fixation via plate-and-screw use should be employed but judiciously and only in those areas where significant postoperative pressure can be expected. Prior to closure, lateral canthopexies are performed by attaching the lateral canthi to the orbital rim with permanent sutures anchored through drill holes in the bone.
Figure 3–6 Final reconstruction in unilateral coronal synostosis. The orbital rims have been reconstructed using an onlay graft and by advancing the recessed rim and recessing the advanced rim. The orbital rims are attached to the parietal bone using absorbable plates. The segment of frontal bone is also reshaped through a combination of Tessier bone benders, inner and outer cortex burring, and barrelstaven-like osteotomies to match the new curve of the supraorbital unit and to recreate a smooth and symmetric forehead. The segment can be rotated 180 degrees to use the more properly shaped curve of the posterior edge to match the curve of the supraorbital unit if needed. This segment can be secured with either resorbable plates and screws or even absorbing sutures to avoid any possibility of future growth restriction or transcranial migration of any fixation hardware. 10.1055/978-1-60406-039-3c003_f006
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Unilateral and Bicoronal Craniosynostosis
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Bilateral Coronal Craniosynostosis The problem with the bilateral deformity is twofold: first, the height of the skull and the recession of both supraorbital rims and lateral orbital rims and second, the brachycephaly that presents a significant problem because it is difficult to correct and failure to correct it will compromise the overall result (Fig. 3–2). The issue is whether its correction is warranted in every instance. This can be addressed in two ways: (1) osteotomy and advancement of the single orbital unit consisting of both orbits and the supraorbital bar, as previously described; and (2) expansion of the entire cranial base region that allows for a downward settling of the top portion of the skull along the vertex, thus reducing overall skull height. It is this second goal that necessitates a change in the operative positioning from that used in the unilateral deformity. The patient is placed in a modified prone position, the so-called sphinx position, to correct both the frontal and height abnormalities. Before placing the patient in this position, however, it is important to assess the stability of the cervical spine and the craniovertebral junction by preoperative lateral cervical spine roentgenograms in flexion and extension. Positioning the patient on the operating table is greatly aided by a vacuum-stiffened bean bag to mold the upper body and neck. The face and arms are padded with thick, cushioning foam to prevent pressure sores and compression nerve palsies (Fig. 3–7). Bur holes are placed in the pterion regions bilaterally, and parasagittally in the anterior parietal bone, just posterior to the coronal suture. Similarly, a biparieto-occipital bone graft is outlined with multiple bur holes adjacent to the sagittal and transverse sinuses. Once the bone is elevated both frontally and parieto-occipitally, further dissection epi-
Figure 3–7 Operative positioning for bilateral coronal synostosis. The patient is placed in a modified prone position, the so-called sphinx position, to correct both the frontal and height abnormalities. Before placing the patient in this position, however, it is important to assess the stability of the cervical spine and the craniovertebral junction by preoperative lateral cervical spine roentgenograms in flexion and extension. Positioning the patient on the operating table is greatly aided by a vacuum-stiffened bean bag to mold the upper body and neck. 10.1055/978-1-60406-039-3c003_f007
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18 Pediatric Neurosurgery durally may be performed below the level of the transverse sinus to allow the surgeon to fracture outwardly (in the posterior direction) the occipital bone. The outfractures or barrel-staven-like osteotomies increase the bony capacity by enlarging the perimeter of the skull locally. This allows later brain and dural displacement or settling into this region as the height of the skull becomes reduced secondarily by gravitational forces (Fig. 3–8). Barrel-staven-like osteotomies in the occipital bone in the midline and paramedian regions are longer than those placed further laterally, to achieve elongation along the AP axis of the skull, without further widening of the parieto-occiput. The thickened and abnormally elevated superior portion of the greater wing of the sphenoid bone is removed by rongeur in a manner similar to that described for the unilateral deformity. The abnormally convex squamous portion of the temporal bone
Figure 3–8 Craniotomies and osteotomies for bilateral coronal synostosis. The craniotomized segments include midline biparietal, bifrontal, and bioparieto-occipital flaps. Once the bone is elevated both frontally and parieto-occipitally, further dissection epidurally may be performed below the level of the transverse sinus to allow the surgeon to fracture outwardly (in the posterior direction) the occipital bone. The outfractures or barrel-stavenlike osteotomies increase the bony capacity by enlarging the perimeter of the skull locally. The barrel-staven-like osteotomies in the occipital bone are longer than those placed further laterally, to achieve elongation along the anteroposterior axis of the skull. The abnormally convex squamous portion of the temporal bone is left in place but is addressed in a similar manner with barrel-staven-like osteotomies. The bilateral three-quarter orbital osteotomies are elevated, reshaped, and advanced. 10.1055/978-1-60406-039-3c003_f008
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is left in place but is addressed in a similar manner with barrel-staven-like osteotomies. The bone is reshaped and straightened by radial osteotomies into the center of the convexity and controlled outfracturing of the bone segments with Tessier bone benders. By leaving the temporal bone in place, the overall stability in the lateral portions of the skull is increased. The craniotomized frontal and parietooccipital bones are reconfigured using similar bone-shaping techniques before being returned to their orthotopic positions. These are then held loosely in their desired positions by fixation with absorbable sutures to the rigidly fixed advanced orbital unit anteriorly, to the radially cut temporal bone laterally, and to the outfractured occipital base bone posteriorly. The vertex of the infant, composed primarily of the fibrous anterior fontanelle, is loosely reattached at the top of the skull with absorbable sutures to the adjoining bones, purposely avoiding any downwardly directly external cinching (Fig. 3–9). We believe that as a consequence of the expansion of the skull-base perimeter, gravitational forces will act to settle the brain and dural into a more inferior overall position, thus having the effect of decreasing the overall height of the skull. This obviates the need for any deliberate downward cinching of the skull vertex as previously described, which did occasionally lead to adverse effects on cerebral circulation.
Figure 3–9 Final reconstruction in bilateral coronal synostosis. The craniotomized bifrontal and biparieto-occipital bones are reconfigured using similar bone-shaping techniques before being returned to their orthotopic positions. These are then rigidly fixed to each other and held in their desired positions with absorbable sutures to the rigidly fixed advanced orbital unit anteriorly, to the radially cut temporal bone laterally, and to the outfractured occipital base bone posteriorly. The vertex of the infant, composed primarily of the fibrous anterior fontanelle, is loosely reattached at the top of the skull with absorbable sutures to the adjoining bones, purposely avoiding any downwardly directly external cinching. 10.1055/978-1-60406-039-3c003_f009
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3 Closure The operative field is copiously irrigated to remove all nonviable debris and bone dust that could act as a nidus for future infection. Because the temporalis muscles were never detached from the overlying scalp flap, there is no need to reattach the muscles to their insertions, as they will naturally return to their proper position as the scalp flap is brought posteriorly. The scalp flap is reapproximated and closed in a two-layer fashion with buried absorbable sutures both in the subgaleal plane and on the skin. A snug but nonconstricting dressing using a sterile surgical towel wrapped as a turban is placed over the entire head, and the head is kept elevated at all times. The tarsorrhaphy sutures and the wire around the endotracheal tube are then removed.
Specialized Instrumentation A significant advance in instrumentation for pediatric craniofacial surgery occurred with the introduction of resorbable plate-and-screw fixation hardware. These new biomaterials consisting of polymers of polylactic acids are designed to be totally resorbed within 9 to 15 months following implantation. Studies have confirmed that they have tensile strength properties comparable to previously used metallic hardware at the time of their initial use, which allows for the same adaptability when used in three-dimensional calvarial reconstruction. Due to the relatively long retention lifespan of the fixation hardware, the reconfigured and repositioned bone segments can heal with additional support from the plates and screws. Any concern about future translocation of the hardware or restriction of further craniofacial growth is obviated because of predictable resorption of the hardware. High-speed drill and saw systems have made the surgery technically easier.
Postoperative Management Including Possible Complications Immediate postoperative care is given in the pediatric intensive care unit. Vital signs and central venous pressures are monitored, and laboratory values are obtained for review of evidence of hypovolemia and blood loss. Depending on the degree of blood deficit, blood transfusions are frequently necessary and the concomitant replacement of coagulation factors may be required. Appropriate dosages of analgesia are given intravenously to keep the patient comfortable. The child is positioned on his/her back in bed to keep pressure off the forehead and orbits, and the head is elevated at 30 degrees to prevent excessive postoperative swelling. As a result of the periorbital manipulations, the eyelids commonly swell shut within 24 hours following surgery. This can cause anxiety for both the parents and the child, and reassurance
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must be given that the majority of the swelling will resolve in 3 to 4 days. In most instances, the child is ready for transfer to the regular ward within 24 to 48 hours. Usually, the child will run a slightly elevated temperature between 38°C and 39°C at day 3 or 4 following surgery. A routine fever workup is performed, but only rarely is the fever caused by infection. The child is considered stable for discharge from the hospital once the child is tolerating a regular diet and eyelid swelling has resolved enough to permit eye opening. A follow-up visit is arranged for 1 week after hospital discharge.
Complications Early postoperative complications arise from intraoperative or perioperative blood loss, which can be compounded by inadequate blood replacement. Tears in the sagittal sinus during the craniotomy can have immediately devastating consequences and must undergo repair quickly. Meticulous attention must be directed when looking for possible tears in the dura mater, which can lead to a persistent cerebrospinal fluid leak. Once recognized, the tear can be easily repaired with a single absorbable suture of 4–0 Nurolon. An air embolism is also a possibility, particularly if the patient is slightly volume-depleted and a sinus is inadvertently entered. This can be detected by the precordial Doppler ultrasound, as well as by the end-tidal volume gas spectrometer. Treatment includes placing the patient in a Trendelenburg position and flooding the field with saline to prevent further intake of air into the circulation. A small amount of air is usually tolerated with minimal deleterious effect. Injury to the brain itself, as well as the globes, can occur if proper precautionary measures are not taken during the osteotomies, although this risk remains low with an experienced craniofacial surgical team. Pressure sores must be avoided by attention to and protection of the areas where the skull rests during the procedure. The most frequent late complications include infection and recurrence or relapse of the original defect due to suture restenosis. To prevent infection postoperatively, strict sterile technique must be adhered to and prophylactic antibiotics used up to the time of removal of the drain. If osteomyelitis occurs, there is a high risk of loss of the bone grafts. Acknowledgment This chapter is a revision of the chapter, “Treatment of Unilateral or Bilateral Coronal Synostosis” by John A. Persing, M.D., and John A. Jane, Sr., M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 1, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank John A. Persing, M.D., for his help and efforts on the original chapter published in the first edition of this work.
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4 Transoral Surgery for Craniovertebral Junction Abnormalities Arnold H. Menezes Abnormalities of the craniovertebral junction (CVJ) have been documented for many centuries with postmortem examination. The antemortem recognition of these lesions, in the past five decades, has now stimulated surgical therapy. Several approaches to the anterior craniovertebral border have been developed. Of these, the transoral-transpalatopharyngeal route is the most frequently used for decompression of the ventral cervicomedullary junction. This author has performed more than 700 of these procedures and shares his experience with the readership. The advances in microsurgical instrumentation and neurodiagnostic imaging have expanded the use of this approach.
Patient Selection Bony abnormalities of the craniovertebral junction can be divided into those that are reducible and the irreducible categories. The primary treatment for reducible CVJ lesions is stabilization. Surgical decompression of the ventral cervicomedullary junction is performed when irreducible pathology is encountered. This decompression must be performed in a manner in which encroachment has occurred. The transoral-transpalatopharyngeal approach is utilized when a lesion is ventrally situated. The other possible approaches to the ventral CVJ are the lateral extrapharyngeal and the maxillary dropdown procedures. In lateral compressions, a lateral or posterolateral approach is utilized. When dorsal compression is evident, a posterior approach is made. If instability exists following any of the situations, a posterior fixation becomes mandated. Thus, the factors that guide the surgical approaches to the lesions of the CVJ are: (1) reducibility of the lesion; (2) the direction of the encroachment; and (3) the type of the lesion.
Preoperative Preparation The relevant diagnostic imaging for treating abnormalities at the CVJ consists of plain radiographs of the region that include the skull and cervical spine. Dynamic studies in the extended and flexed positions assess stability and possible reduction. Computed tomography (CT) of the CVJ is an integral part of the assessment. This should be augmented with three-dimensional CT reconstructions to provide an understanding of the location of the skull base as well as
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the atlas and the axis and the odontoid process in particular. The latter, the odontoid process, is usually smaller than in the normal adult, when combined with segmentation abnormalities. Magnetic resonance imaging (MRI) is now the mainstay in neurodiagnostic imaging of the craniocervical junction (Fig. 4–1). This should be performed with thin-section midsagittal images in both the T1 and T2 modes and should include the dynamic flexed and extended positions. It provides information about the relationship to neural structures, the osseous abnormality, and the vascularity. Magnetic resonance angiography (MRA) is an essential part of the investigation, especially in patients with neurological dysfunction that cannot be explained on the basis of the previous studies. This is done with the patient in the flexed and in the extended positions as well as in a rotated position to look for vascular occlusions that can change with position. It is crucial to attempt “reduction” in children. This is because in 80% of children with atlantoaxial dislocation or basilar invagination below the age of 12 to 14 years, a reduction is possible so as to relieve compression on the neural structures and thus avoid the ventral procedure. In that circumstance where a reducible lesion is documented, stabilization is the operation required.
Assessment of Nutritional Status and Dental Hygiene This is particularly important in children who present with brain stem dysfunction or a failure to thrive. Preoperative nutritional support is mandatory. Dental hygiene is assessed to eradicate causes of operative bacterial contamination. Dental guards are also fashioned to protect the upper and lower dentition during the oncoming operative procedure.
Assessment of Co-Morbidities It is necessary to assess pulmonary function as well as to assess sleep apnea in those children who have obvious brain stem dysfunction or abnormalities that pertain to the glossopharyngeal, vagus, and hypoglossal nerves. This may require a tracheostomy to be performed before the start of the operative procedure. However, in the author’s experience in the past 15 years, a tracheostomy has not been performed preoperatively because postoperative improvement is the rule. On the other hand, two patients have had to have a tra-
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procedure and similarly Peridex (chlohexidine gluconate) gargles. It is necessary to recognize that the entrance to the oral cavity must provide a working distance of 2.5 to 3 cm between the upper and lower incisor teeth. This span may not be available in children with juvenile rheumatoid arthritis and with involvement of the temporomandibular joint, who have ventral cervicomedullary compression. There were four instances of children with segmentation abnormalities of the cervical spine and acute kyphosis of the craniocervical junction that necessitated mandibular split with midline glossotomy due to small oral access.
Preoperative Cervical Traction A
B Figure 4–1 (A) Composite of mid-sagittal T2- and T1-weighted magnetic resonance imaging (MRI) of posterior fossa and cervical spine. This 8-year-old girl presented with difficulty swallowing, sleep apnea, and distal arm weakness. Note the ventral bony abnormality of the clivusodontoid indenting into the ventral mid-medulla oblongata. There is tonsillar ectopia through the foramen magnum, and the cervicomedullary buckle is behind the body of C-2. A syringohydromyelia is evident at the cervicothoracic junction. (B) Composite of T2- and T1-weighted MRI of the craniocervical junction and cervical spine of patient in Fig. 1A. These postoperative images were made a year following transpalatopharyngeal resection of the lower clivus and the odontoid process with medullary decompression. Note the collapse of the cervicothoracic syrinx in addition to the medullary decompression.
Skeletal traction is usually applied through an MRIcompatible crown halo device so as to assess the reducibility of the bony lesion. In the pediatric patient between the ages of 8 and 16 years, this is instituted 4 days prior to the planned anterior and posterior surgical procedures at the craniocervical junction. Should the lesion be reducible, a dorsal fixation is made. On the other hand, if it is irreducible, both the ventral and dorsal procedures are performed in the same anesthetic. In situations where an irreducible lesion is defined at the initial assessment, the crown halo traction is placed only after the induction of general anesthesia to stabilize the CVJ. In children between the ages of 2 and 8 years, it is not feasible to do preoperative traction. This author has utilized intraoperative traction and fluoroscopy to document irreducibility in the very young child. The same principles regarding reducibility apply. The transoral-transpalatopharyngeal route to the craniocervical border has been safe and has provided the author with a direct approach to this region. It has been utilized between 1977 and 2005 in more than 700 patients (Fig. 4–2). The infection rate for the operation is less than 1%. A dorsal occipitocervical fusion has been necessary in all children. The indication for ventral transoral-transpalatopharyngeal approach to the craniocervical border is irreducible ventral bony abnormalities (including pannus) with compression of the cervicomedullary junction. This indication is reserved for extradural bony and soft tissue masses and a few intracranial-intradural tumors. Preoperative antibiotics consist of 1 g of penicillin G started 2 hours before the commencement of the transoral procedure.
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Operative Procedure cheostomy after failing weaning from the endotracheal intubation 10 days after the ventral decompressive procedure.
Oropharyngeal Cultures Three days prior to the operation oropharyngeal and nasal cultures are obtained. No antibiotics are instituted if normal oral flora is present. Mupirocin nasal ointment is utilized in the nasal passages twice a day prior to the operation. Nystatin rinses are instituted 3 days prior to the operative
The pediatric patient is brought into the operating suite with a cervical collar in place as a precaution for the intubation maneuvers as well as for positioning. Topical oropharyngeal and nasopharyngeal analgesia is utilized to facilitate the fiber-optic endotracheal intubation. An awake fiber-optic intubation is made in the older pediatric patient. In the young child, general endotracheal and intravenous anesthesia is then followed by a fiber-optic endotracheal intubation, which is accomplished through the mask. The
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Figure 4–2 Illustration of rostral-caudal exposure (between arrows) obtained via the transoral operation. 10.1055/978-1-60406-039-3c004_f002
position of the patient during intubation is judged by the preoperative dynamic studies. In the awake patient following intubation, the patient is positioned for the operative procedure and examined awake to check the neurological status. General anesthesia is then administered. The author avoids nasopharyngeal intubation because it disrupts the integrity of the high nasopharyngeal mucosa and obstructs the operative field. The patient is now positioned supine on the operating table with the head resting on a padded headrest, with mild extension with cervical traction in place at 7 lb weight, in the older child. In children between the ages of 5 and 8 years, this weight should be reduced to 4 to 5 lb. The oral endotracheal tube is now secured to the skin over the middle half of the mandible on the left with sutures and adhesive tape. The nasal passages are topically anesthetized with 4% cocaine and are then packed with nasal paddies. The laryngopharynx is occluded with a throat pack, and the cleansing of the oral cavity and pharynx now commences. This is done with successive rinses of 10% povidone-iodine followed by normal saline and then hydrogen peroxide and subsequently the saline rinse. The dental guards are now used over the upper and lower dentition to protect them
during the operative procedure. The author also prepares the right anterior abdominal wall for possible harvesting of donor external oblique aponeurosis and fat should this be necessary if the dura is opened during the transoral procedure. The circumoral area as well as the anterior abdominal wall are prepared and draped in a sterile fashion. A Dingman mouth retractor with an incorporated tongue blade is utilized for automatic exposure. In circumstances where the operative procedure is at the foramen magnum and above, it is necessary to split the soft palate and at times the hard palate. On the other hand, if the procedure is limited to the level of the atlas and axis vertebrae, the soft palate may be elevated by catheters attached to the soft palate via the nasal passages and secured to either side of the soft palate and then withdrawn into the high nasopharynx to allow for exposure. A gauze pack occludes the laryngopharynx. Lidocaine solution (0.5%) with 1:200,000 epinephrine is injected into the median raphe of the soft palate. The microscope is now used for magnification and a concentrated light source, and to aid in the operative dissection. The soft palate incision (when performed) starts at the base of the uvula to one side of the midline and ascends into the median raphe within 1 cm to then proceed up in the midline to the hard palate (Fig. 4–3A). Stay sutures provide for lateral retraction and are held in place via the springs of the Dingman mouth retractor. Should exposure be necessary into the lower clivus, an extension of the hard palate incision is made in the midline and a subperiosteal exposure of the midline hard palate is then accomplished. Topical cocaine is now used to anesthetize the posterior pharyngeal wall. The median raphe of the pharynx is then infiltrated with 0.5% lidocaine solution with 1:200,000 epinephrine. A midline incision is made in the posterior pharyngeal median raphe extending from the rostral clivus to the C-3 level (Fig. 4–3B). The leaves of the posterior pharyngeal wall are now reflected laterally and folded upon themselves with stay sutures to prevent damage to the orifices of the eustachian tubes and to allow for exposure. The prevertebral fascia and longus colli muscles are reflected free of their osseous ligamentous attachments to expose the caudal clivus and the ventral surface of the atlas and the axis vertebrae (Fig. 4–3C). The anterior longitudinal ligament and the occipital ligaments are dissected free of their bony attachments to expose further the caudal clivus, the anterior arch of the atlas, and the anterior surface of the axis body (Fig. 4–3D). This provides an exposure of 3 to 3.5 cm in width. One should avoid an attempt at further lateral exposure because this brings a risk of damage to the eustachian tube orifices as well as the vertebral arteries and their entrance into the vertebral canal and possible injury to the hypoglossal nerve. The anterior arch of the atlas is now removed with a highspeed drill for a width of ~20 to 25 mm (Fig. 4–3E). The author utilizes a 4 mm cutting bur that is then changed to a diamond bur using an electric drill. In situations where the odontoid process has invaginated into the posterior fossa, the inferior edge of the hard palate may need to be resected. This latter procedure is accomplished with Kerrison rongeurs. If the inferior portion of the clivus needs to be removed, it is done by thinning the ventral aspect with a diamond bur
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D A
E B
F C Figure 4–3 (Continued on 24)
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G Figure 4–3 (A) Illustration of exposure of the oral cavity and the pharynx with the Dingman mouth retractor in place. The soft palate has been incised exposing a portion of the hard palate at the apex of the incision. The view through the operating microscope is within the circle. (B) Drawing and view through the microscope. The soft palate is retracted laterally with stay sutures and the posterior pharyngeal wall has been incised. (C) The longus colli muscles as well as the posterior pharyngeal wall are retracted laterally to expose the fascia overlying the anterior arch of the atlas as well as the body of C-2. (D) The dens is revealed when the anterior arch of the atlas is removed. The caudal clivus is exposed with the invaginating odontoid process underneath the caudal clivus. (E) The shell of the odontoid process is removed along with a portion of the axis body. (F) The cored out odontoid process and shell are being removed with curettes and rongeurs. (G) The cruciate ligament is visible after removal of the odontoid process. Dura now fills the area of decompression. 10.1055/978-1-60406-039-3c004_f003
and defining the inferior border. It should be separated from the circular venous sinus and the dura as well as the tectorial membrane, which is attached to the posterior aspect of the clivus. The author prefers the use of fine Kerrison rongeurs for clivus resection after the thinning out has been done to prevent inadvertent entrance into the dura or the circular sinus. The odontoid process removal is accomplished by starting at the tip and then proceeding downward in a rostral-caudal manner. The odontoid process is first cored out and subsequently the lateral margins are defined using fine curettes and rongeurs. It is essential to sharply divide the apical ligament as well as the alar ligaments with curettes (Fig. 4–3F). Resection of the odontoid process should proceed into the body of the axis dictated by preoperative diagnostic studies, which must be referred to during the operation. Fine up-biting Lee-Smith Kerrison rongeurs with 1 mm footplates are used as well as microcurettes and microbiopsy forceps to facilitate removal of the odontoid process. Removal of pannus from behind the odontoid process (especially in unstable situations when it is present) and from the posterior fossa is done in a piecemeal fashion with bipolar cauterization with angled and ringed curettes. The lateral extent of the exposure should encompass the amount of decompression necessary, dictated by the preoperative CT and MRI.
At this point, the cruciate ligament should be visualized (Fig. 4–3G). In such situations when it is frayed, such as with tumor, it should be removed. Otherwise, this author has preferred to leave it in place. Likewise, the tectorial membrane must be preserved. The cervical traction is maintained during the operation for inherent or potential instability. In circumstances where pannus or granulation tissue acts as a mass, especially in children, this is removed with bipolar cauterization and piecemeal reduction. It is not necessary to remove the entire granulation tissue because this will ultimately fibrose and aid in the healing process. Aerobic and anaerobic bacterial cultures are obtained from the depths of the wound at the end of the decompression and resection. The author has utilized a combination of bacitracin powder and microfibrillar collagen to layer the resection bed. The longus capitis and the longus colli muscles are now approximated in the midline with interrupted sutures of 3–0 polyglycolic using a figure-of-eight technique. A similar strength suture is utilized to bring together the pharyngeal constrictor muscles and separately the posterior pharyngeal mucosa. In young children there is exuberant adenoid tissue present. The mucosa over the clivus is quite delicate and friable, and attempts to bring this together will only cause further bleeding. In this circumstance, large cerclage sutures are made and compressed Avitine is placed over the area. A blanket of Gelfoam soaked in thrombin is then placed over the reconstituted pharyngeal wall. The throat pack is now removed. A nasopharyngeal-gastric feeding tube is now passed via the nostril into the pharynx and under direct vision into the esophagus and subsequently into the stomach (Fig. 4–4). The position of this tube is confirmed by insufflation of air into the tubing and the anesthesiologist auscultating over the abdomen. This tube is then secured to the ala of the nostril. The closure of the soft palate must be in a layered fashion. It is done by bringing together the nasal mucosa together with interrupted 3–0 polyglycolic suture. The muscular layer as well as the oral mucosa of the soft palate are approximated with interrupted vertical mattress sutures of similar strength. Tension in these sutures must be carefully assessed so as not to be too snug, which leads to dehiscence. A dorsal occipitocervical fusion combined with posterior fossa decompression is usually mandated and accomplished with the same anesthetic.
Special Circumstances Transpalatal Route In congenital abnormalities where the underlying pathology consists of a foreshortened clivus, the clivus-odontoid articulation is high and the clivus itself tends to be more horizontal than vertical. In this circumstance, removal of the posterior 1 cm of hard palate in the sagittal dimension may be necessary, and the width of this resection is ~8 mm to either side of the midline to allow for exposure of the high nasopharynx and the clivus. The posterior edge of the
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Postoperative Management Including Possible Complications
Figure 4–4 The photomicrograph through the operating microscope after closure of the longus colli muscles, the posterior pharyngeal musculature, and the posterior pharyngeal mucosa in a layered fashion. A nasogastric feeding tube is now visualized in the posterior pharynx. 10.1055/978-1-60406-039-3c004_f004
vomer becomes visualized and may be removed. Closure of this soft palate is made in a layered fashion as previously described. This technique allows high nasopharyngeal exposure without splitting the mandible or doing a median glossotomy.
Intradural Extension of Tumor and Repair of CSF Leak An intradural lesion at the upper cervical spine, craniocervical border, or behind the clivus necessitates preoperative recognition of the dural extension and placement of a lumbar subarachnoid drain prior to commencement of the operation. The dural turgidity may be reduced by draining spinal fluid during the operation. The dural incision is made in a cruciate fashion. The vertical component of this starts inferiorly, proceeding in a rostral dimension with careful cauterization of the circular sinus at the foramen magnum. Once the intradural operation is complete, it is essential to bring the dural leaves together with 4–0 polyglycolic suture. This is then covered with external oblique aponeurosis graft, which is sutured to the dura as a transfixing suture through the fascia. This latter maneuver prevents migration of the graft during further closure. Adherence to the dura is confirmed with the application of fibrin glue. The fascia and dura are then covered by the fat obtained from the anterior abdominal wall, after which the posterior pharyngeal closure is made in the described layered fashion. During and after the operative procedure, CSF tension is reduced by drainage from the lumbar subarachnoid space. Triple antibiotic therapy consisting of cefotaxime, metronidazole, and methicillin are continued for the first 5 days after operation. If no bacterial flora is identified on CSF examination, the third-generation cephalosporin is discontinued and the antibiotics terminated at the end of 10 days. At this time the CSF drainage is discontinued.
The endotracheal tube is maintained in place for postoperative convalescence until the swelling in the tongue and oral tissues has receded. This usually lasts for 3 to 4 days. It is our policy to maintain a daily caloric intake of 2500 to 3000 calories by the third to fourth postoperative day. The transpyloric placement of the nasogastric tube facilitates this. The postoperative management consists of ventilator and respiratory care and nutritional support, antibiotic regimen, pain management, and immobilization. The vast majority of children who have undergone a transoral-transpalatopharyngeal decompression of the craniocervical border will leave the operating theater with an endotracheal tube in place secured to the circumoral area, intravenous and intra-arterial lines that have been required for intraoperative care, and nasogastric feeding tube. In addition, the child should have had a dorsal stabilization procedure at the craniocervical junction. The child is then transported to the intensive care location with a soft cervical collar in place. The halo ring that was utilized intraoperatively for traction and stabilization is left in place if it is later to be incorporated into a halo vest. Intravenous penicillin G is administered for 48 hours and then discontinued. However, if wound cultures grow pathological flora, appropriate antibiotics are instituted. The Peridex and nystatin rinses that were instituted preoperatively are now done at 8-hour intervals to minimize bacterial flora, especially in light of the operative procedure and the prolonged intubation necessary. The dental guards serve to prevent inadvertent biting on the endotracheal tube. The cuffed endotracheal tube is intermittently deflated only after proper oral care is accomplished. The soft tissues of the retropharyngeal space are monitored with lateral cervical radiographs. By the end of the third or fourth postoperative day, when lingual swelling has receded and the pharyngeal edema has resolved, an attempt at endotracheal extubation is made. This should be performed by an intensivist and with a neurosurgeon in attendance. Prior to this, nasogastric feedings are discontinued and the endotracheal tube cuff is deflated to detect leakage of air around the tubing. Our policy is to attempt extubation only with the utilization of a “tube exchanger” replacing the endotracheal tube. This smaller diameter tube exchanger allows for satisfactory ventilation and should this be possible, the tube exchanger is removed. If not, the tube exchanger acts as a stylet to allow for rapid reintubation. The position of the nasogastric feeding tube placed during the operation is confirmed with appropriate chest and abdominal films. It is preferable to have the feeding tube in a transpyloric location. Enteral feedings are instituted in a graduated manner at the end of 24 hours. A clear oral intake is initiated by the fifth postoperative day, at which time the oral endotracheal tube had been removed. A full liquid diet is started by the 10th day. By this time, the patient’s caloric intake is between 2500 and 3000 calories. A soft diet is instituted by the end of the 15th day.
26 Pediatric Neurosurgery Postoperative immobilization is accomplished with a soft collar until the final decision is made to use either a halo vest or an occipitocervical brace. An immediate placement of a halo vest after the operation hampers postoperative oral care as well as jeopardizes extubation and respiratory function.
Complications The complications are divided into perioperative complications of transoropharyngeal surgery and delayed complications.
Perioperative Complications It is necessary to make sure that the distance between the incisor teeth is more than 25 mm to accomplish the operation. Otherwise, a mandibular split or a tongue split may be necessary or another approach contemplated. However, the situation may improve with the administration of intravenous paralyzing agents during the operation. The damage to the eustachian tubes and hypoglossal nerves can be avoided by limiting the lateral exposure from the midline to <2 cm. In situations where one is unable to reach the clivus for resection due to platybasia, it is necessary to divide the soft palate and the hard palate, and the surgeon’s location is confirmed with intraoperative fluoroscopy. Resection of the base of the odontoid process in an attempt to pull down the anchored tip is always fraught with difficulty. Hence, the resection should start from the dens and then proceed downward. A novice may use “frameless stereotaxy” or intraoperative fluoroscopy. Persistent bleeding from the circular sinus necessitates the use of hemostatic agents and even possibly an attempt to clip both the leaves of the bleeding dural site. Pannus and arterial bleeding must be controlled with cauterization. CSF leakage should be addressed as previously described.
Delayed Complications of Transoropharyngeal Surgery Postoperative lingual swelling may be controlled partially by the use of intravenous Decadron (dexamethasone) dur-
ing the operation and postoperatively. At times, intermittent release of the tongue depressor helps with relieving venous stasis as well as lymphatic obstruction in prolonged operations. If meningitis occurs, it is mandatory to obtain CSF and also place a lumbar drain. During this time, no oral intake should be allowed and intravenous antibiotics must be instituted. An attempt at closure of the leakage site should be made. Early palatal dehiscence requires an immediate attempt at reclosure. A delayed small palatal opening should be treated with hyperalimentation, and if this does not close over several weeks, it will require freshening of the opening and reclosure. Pharyngeal dehiscence is a dreaded complication. When it occurs within the first week, reclosure must be attempted. If, however, this occurs on a delayed basis after a week, the patient is treated with hyperalimentation and intravenous antibiotics. Neurological worsening requires an assessment of the alignment to make sure that there is no meningitis, abscess formation, or retained lesion. Thus, an MRI must be repeated and possibly an MRA to look for vascular compromise. A retropharyngeal abscess requires drainage in an extra-pharyngeal manner and not through the mouth. This is to prevent fistula formation. In circumstances of retropharyngeal abscess, one must check for meningitis and osteomyelitis. Delayed pharyngeal bleeding must signal the treating physician to look for infection, osteomyelitis, and possible vertebral artery erosion and a false aneurysm. Angiography is necessary. If the vertebral artery abnormality is recognized, this should be occluded with either coils or a balloon. Velopalatine incompetence is mostly seen in children and occurs about 4 to 6 months after operation. It signifies fibrosis of the palate or pharyngeal wall. The treatment for this has been pharyngeal retraining, the use of a palatal prosthesis, and at times a pharyngeal flap. Persistent hoarseness of voice 4 to 6 weeks after the operation necessitates visualization of the vocal cords to look for granulomas and polyps.
5 Malposition of the Orbits John A. Persing and Bianca I. Knoll
Malposition of the orbits is a congenital deformity that is frequently seen in craniofacial anomaly centers. There are two commonly encountered forms of this abnormality involving the mediolateral axis of the orbits. The first is telorbitism, which refers to a widened distance between the two orbits. This is to be distinguished from the second type, hypercanthorum, in which there is a widened distance between the medial canthi alone (the distance between the lateral canthi is normal). The widened distance between the canthi may be due to bone, soft tissue, or both being displaced laterally. Other forms of orbit malposition also exist. Superior and inferior displacements (vertical dystopia) as well as anterior and posterior displacements (AP dystopia) with or without accompanying rotational components (rotary dystopia) occur. Dysfunction may include diplopia, amblyopia, and absence of normal depth perception. The goal of surgical treatment in these patients, therefore, has been to create an aesthetic cranioorbitalfacial image while restoring or maintaining visual function. Only the anomalies of the mediolateral axis will be discussed in this review.
Patient Selection The appropriate operative procedure for correction for the patient with hypercanthorum entails translocation of the medial portion of the orbits only, whereas in the patient with telorbitism, both the medial and lateral orbital walls are translocated medially. Patients are chosen for the two different operative approaches based on the clinical measurement of a widened intercanthal distance (medial and lateral), plain radiograph and computed tomography scan demonstration of widened bony intercanthal distance. Surgery is elected usually at approximately 5 years of age, unless a concurrent abnormality such as an encephalocele is present, providing the opportunity for one-stage treatment at an earlier age. Age 5 is chosen because this allows for correction of the abnormality when the bone is sufficiently strong to avoid inadvertent fracture during surgical mobilization, the orbit has reached relative maturity, and the child has not reached school age, so that major deformity can be corrected, or at least ameliorated, prior to critical peer interaction in school.
Preoperative Preparation The risks of the operative procedure include potential injury to the brain and visual system, including enophthalmos, extraocular muscle entrapment, optic nerve damage, cerebrospinal fluid leakage, and recurrence of the intercanthal deformity postoperatively. Translocation of the orbits medially in early childhood may negatively affect midfacial growth, particularly if the osteotomy is significantly below the inferior orbital rim. Damage to developing tooth roots, particularly the canine tooth root, as it is located most cephalad, is possible. Injury there may further reduce growth potential of the maxilla. Preoperative preparation includes prophylactic use of intravenous antibiotics at the time of surgery to cover aerobic and anaerobic flora in the nose, and prophylactic, shortterm anticonvulsants. No steroids are used. A comprehensive anesthetic technique is advocated, which includes orotracheal intubation, monitoring for blood loss with central venous catheters, arterial line, Foley catheter, and monitoring for air embolus by Doppler, endtidal CO2, and nitrogen monitors. Hypotension is induced by increasing concentrations of the inhalation of anesthetic agent at the time of craniotomy to minimize blood loss. Autologous or designated donor blood transfusion is preferred if blood transfusion is necessary. Spinal drains are placed in the lumbar cistern following the induction of anesthesia. The drains are not opened, however, until bur holes have been made and the craniotomy is about to be performed. A Bair Hugger blanket (Arizant Healthcare, Eden Prairie, Minnesota) is used to keep body temperature above 36.5°C. All irrigation fluids are warmed before use to reduce the likelihood of hypothermia.
Operative Procedure The initial preparation for the treatment of patients with hypercanthorum or telorbitism is the same. The patient is placed supine with the head on a well-padded headrest and the neck is slightly flexed. Draping of the patient includes full exposure of the scalp to the region of the midportion of the vertex of the skull and to the level of the mouth caudally. Hair removal in the scalp, if performed at all, is minimal, and corresponds to the course of the coronal incision.
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28 Pediatric Neurosurgery Hair anterior to the skin incision line is braided with rubber bands to remain out of the way during the operative procedure and is covered with masking tape or heavy aluminum foil. A coronal incision is performed, extending down to the level of the superior tragus anteriorly, to allow for periorbital dissection. The dissection of the anterior scalp flap is performed in a supraperiosteal plane to the level of the orbital rims, followed by elevation of the periosteal flap, based anteriorly, on the supraorbital vessels from the same coronal incision site to be used later as a covering flap for the anterior cranial fossa floor defect created by the orbit translocation procedure. Bilateral pterion bur holes and one parasagittal bur hole posterior to the coronal suture are placed. A bifrontal craniotomy line is drawn on the skull leaving ~1 cm height of frontal bone superior to the apex of the superior orbital rim. A bifrontal craniotomy is performed. The outer table of the midline frontal bone of the glabelar region is removed with a side cutting bur, and the frontal bone is fractured forward. Alternatively, as frequently is the case in the region of excess bone in the glabelar region, a bur hole may be placed in the area of intended bone removal (Fig. 5–1A).
Hypercanthorum In patients with hypercanthorum, the remaining bifrontal bone segment is bisected, leaving a supraorbital bar, ~5 to 6 mm in width, cephalad to the medial portion of the orbital rim. If the nasal profile is acceptable, a segment of midline nasal bone may be left ~3 mm wide to simulate a new nasal bridge. Two additional approaches exist, however, if the nasal profile is unacceptable. The midline bone may be removed entirely, leaving a 5 mm wide bone segment laterally on each medial orbital rim (Fig. 5–1B). When the orbital rims are translocated medially, the medial border of the orbital rim defines a new, more acceptable nasal profile. The second and most often used alternative is to leave a 3 mm segment of nasal bone in the midline to serve as a base for scaffolding for on-lay bone graft augmentation of the dorsum of the nose. The bone used for augmentation is usually from the rib because of the potential to include a pressureresistant cartilaginous cap. With all these techniques, the medial orbital osteotomy is usually performed with a sagittal or oscillating saw to avoid unwanted fracture of the nasal and lacrimal bones. The frontal lobes are allowed to reposition posteriorly by the cerebrospinal fluid drainage for an osteotomy in the orbital roof extending posterior to the midpoint of the globe’s anteroposterior axis (Fig. 5–1C). The medial limit of the osteotomy is the lateral cribriform plate, avoiding injury, at this time, to the olfactory nerve fibers. Characteristically, the cribriform area is excessively widened and frequently obstructs medial translocation of the orbital rim. Therefore, the anterior-most olfactory fibers are divided, and the proximal segments of these nerve fibers and surrounding dura are oversewn to prevent cerebrospinal fluid leakage postoperatively. The antereolateral portion of the ethmoid air cells are removed by rongeur to allow subsequent unobstructed movement of the orbits medially.
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If the medial canthi position relative to one another and to the anteroposterior axis of the nasal bone is unacceptable, effort is made to preserve their attachment to the lacrimal bone. To avoid displacement of the canthi during dissection, a subciliary, transconjunctival Caldwell-Luc incision is made infraorbitally to complete the caudal dissection and osteotomy paralleling the superior orbit osteotomy (Figs. 5–1D—5–1F). A transversely oriented osteotomy is placed the paramedical frontal bone, leaving a 5 to 6 mm width of frontal bone as the medial extension of the supraorbital bar. If the midline nasal bone is to remain in situ, the osteotomy line does not extend into the plane of the medial nasal bones. The segment complex of frontal ethmoid, and more laterally situated nasal bones, is removed by osteotome bilaterally (Fig. 5–2A). The medial rim with superior and inferior rim extensions, in the form of the letter “C,” are mobilized. Ordinarily, the greatest resistance to movement is encountered in the deep nasomaxillary region. Prying of the rim with an osteotome usually frees the bony and soft tissue attachments. Care must be taken, however, to avoid injury to the nasolacrimal duct during this maneuver. As the orbits are translocated medially, infolding of nasal cartilage (septal and upper lateral) and mucosa usually results, requiring trimming of the excess tissue. The openings in the mucosa are oversewn to prevent gross air and bacterial contamination into the epidural space postoperatively. The medial orbital walls and the nasal bones are trimmed with the air drill to ~33 to 4 mm wide so that the overall distance between dacryon and dacryon is ~10 mm or less (Fig. 5–2B). Trimming is done at this time rather than earlier to avoid fracture of the medial orbit during the prying maneuvers. The nasal process of the maxilla is aggressively trimmed to avoid occlusion of the airway as the orbital rim is moved medially. The orbital rims are placed in position but are not yet secured. If the medial canthi need to be repositioned, a transnasal medial canthapexy may be performed. It is easier to perform the initial stages of the canthapexy prior to stabilization for the orbital bones because of the greater visibility afforded by the mobile and widely separated bone segments. A drill is used to open the entry point into the posterior superior lacrimal bone (Figs. 5–2C, 5–2D, and 5–3A) to avoid fracture of this fragile bone. If the medial orbital wall is exceedingly thin and does fracture, a split calvarial bone graft (Fig. 5–3B) from the parietal region may serve as a substitute for the medial orbital wall. It will provide stabilization of the medial canthus and avoid anterior as well as lateral migration of the canthus postoperatively. The medial orbital rims are then translocated medially and secured to each other and the frontal supraorbital bar. If the midline nasal profile remains unacceptable after translocation of the medial orbits, a cantilevered costochondral bone graft may be secured to the existing nasal profile (Figs. 5–3C and 5–3D). Costochondral rib grafts are the primary choice graft material because the cartilaginous tip, unlike even calvarial membranous bone, resists resorption extremely well. To lessen the likelihood of epidural infection postoperatively, the pericranial flap previously elevated at the time of anterior scalp flap dissection is tacked over the
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Figure 5–1 (A) A bur hole is placed in the glabelar region at the site of intended bone removal (green) to allow for safe dissection of the midline dura and sagittal sinus. Orbital osteotomies are located, as shown, to include provision for removal of the medial inferior portion of the nasal process of the maxilla so as not to impinge on the nasal airway following medial orbital translocation. A supporting frontal bone bar, ~5 mm tall, is left above the medial superior orbital rim. (B1) The midline nasal bone has satisfactory projection, but the breadth is too great. The midline nasal bone is in situ, and resection of excess bone occurs in the paramedical local left (green). (B2) The midline projection is unacceptable. The midline bone is removed, and the medial orbital walls, when translocated medially, form the new nasal profile. (B3) The existing nasal profile is deficient, but, rather than excising the midline nasal bone, it is allowed to remain in situ to serve as base scaffolding for dorsal 10.1055/978-1-60406-039-3c005_f001
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augmentation by placement of a cantilevered bone graft. (C1) View of the anterior skull base from above. The orbital roof osteotomy extends from the midportion of the orbit laterally to the cribriform plate medially. (C2) The osteotomy extends posteriorly well behind the midpoint of the axis of the globe. Bone is removed medially (green) adjacent to the cribriform plate to allow for medial translocation of the orbital roof. (D) To place osteotomies in the inferior orbital region, either a transconjunctival Caldwell-Luc or subciliary incision is made. (E) In transconjunctival and subciliary approaches, a pre septal dissection is preferred to expose the inferior orbital rim. (F) The inferior orbital osteotomy is placed at the level of the infraorbital foramen in children to avoid damage to developing tooth buds. (From Persing J, Edgerton M, Jane J, Eds, Scientific Functions and Surgical Treatment of Craniosynostosis 1989. Baltimore: Williams and Wilkins. 263–269. Reprinted by permission.)
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30 Pediatric Neurosurgery
Figure 5–2 (A) Dissection is performed posterior to the lacrimal crest medially. An oscillating saw is used to complete the superior and inferior orbital osteotomies. The posterior medial orbital wall osteotomy is complete by an osteotome. Particular attention is necessary to remove enough bone in the ethmoid air cell region to allow for unimpeded translocation of the medial portion of the orbital rim. (B) Following mobilization of the orbital rims, the midline bone and remaining medial orbital rims are trimmed (green) with a shaping bur to achieve the 10.1055/978-1-60406-039-3c005_f002
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thinnest possible final nasal midline (ordinarily 8 to 10 mm encompassing the medial orbital walls and the midline bony strut). (C) The medial canthi are elevated with an accompanying periosteal pennant from the dorsum of the nose. (D) A drill hole (green) is placed in the posterior superior lacrimal bone for the periosteal pennant and the canthus to be passed transnasally. (From Persing J, Edgerton M, Jane J, Eds, Scientific Functions and Surgical Treatment of Craniosynostosis 1989. Baltimore: Williams & Williams. 263–269. Reprinted by permission.)
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Figure 5–3 (A) An air-driven bur is used to penetrate the lacrimal bone perpendicular plate of the ethmoid to allow threading of the canthal tendon. Any significant opening in the nasal mucosa is oversewn. (B) If the lacrimal bone is too fragile or otherwise unusable, a split calvarial bone graft can be used to serve as a buttress substitute for the lacrimal bone. The canthal periosteal pennants are tightened following medial translocation and fixation of the orbital rims. (C) Augmentation of the
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nasal bridge is accomplished following translocation of the orbits by placing a wedge of bone beneath the antilevered costochondal cartilage graft. (D) The graft is secured to the underlying medial orbital rims by transosseous wiring. (From Persing J, Edgerton M, Jane J, Eds, Scientific Functions and Surgical Treatment of Craniosynostosis 1989. Baltimore: Williams & Wilkins. 263–269. Reprinted by permission.
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32 Pediatric Neurosurgery ethmoid air cells on the anterior cranial base. The scalp flap is then closed in two layers, galea and skin. The translocation of the medial orbit rim medial in hypercanthorum effectively enlarges the orbit. This may result in enophthalmos if the movement is more than 3 to 4 mm. In this case, adding intraorbital bone grafts or bone substitutes is highly desirable. In rare circumstances, medial translocation of the medial orbital walls at the level of dacryon is desirable. This approach avoids an open craniotomy and may be very useful in patients with indwelling ventriculoperitoneal shunts, or other co-morbidities. Here, the nasal osteotomy is performed much as described for the medial translocation of the whole medial wall, except that it is done at an infracranial level. Bone is removed from caudal to cephalad with the superior point at the level of dacryon or below the cranial base.
Hypertelorism (Telorbitism) For patients with hypertelorism (telorbitism), the operative approach is much the same as just described for hypercanthorum, but, in addition, the lateral orbit is moved with the medial as a single unit. The movement of the lateral skull with the medial maintains orbital volume, and it obviates the need for intraorbital volume augmentation. The patient is positioned supine, following placement of a lumbar cerebrospinal fluid drain, and a bifrontal craniotomy, including temporalis muscle elevation, is performed. The supraorbital bar is left 1 cm wide at the level of the orbital rim apex (Figs. 5–4A—5–4C). The supraorbital bar will be transversely bisected when translocation of the orbit is performed, leaving a 5 mm wide supraorbital bar for fixation, and a 5 mm wide orbital rim a the rim’s apex. The orbital roof and lateral orbital wall are cut posterior to the midpoint of the globe following protection of the anterior tip of the temporal lobe. If correction of an accompanying orbital malrotation is not necessary, horizontally oriented osteotomies are placed on the anterior surface of the maxilla through or below the level of the infraorbital foramen (Fig. 5–4D) in adults. In young children, the more cephalad osteotomy is desirable to avoid injury to developing tooth roots. Olfactory fiber section and frontonasoethmoid resections are performed as described previously for the treatment of hypercanthorum. In patients with hypertelorism, the medial canthi may require repositioning. This is performed by transnasal canthopexy as described earlier (hypercanthorum). Likewise, the need for repositioning of the lateral canthi ~2 mm above the medial canthi on the horizontal axis also may be evident. After the orbits have been translocated and secured, the attachment point for the lateral canthi, in most cases, is placed just inside the orbital rim (Figs. 5–4E—5–4H). When
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severe exorbitism (globe protrusion beyond the eyelids secondary to a constricted orbit volume) coexists, the canthi are attached to orbital rim bone on the external surface of the zygomatic process of the frontal bone. This reduces the projection of the globe beyond the eyelid. The temporal fossa is filled with calvarial bone chip grafts, and the temporalis muscle is advanced forward to be attached to the orbital rim, to prevent an “hourglass” deformity or hollowing postoperatively in the temporal region. The incisions are closed in two layers, galeal and skin. The nose is packed with petroleum-based gauze. No drain is inserted in the galeal region to avoid aspiration of nasopharyngeal bacteria into the subgaleal space.
Postoperative Management Including Possible Complications The patients are monitored postoperatively by clinical measures, and intracranial pressure (ICP) monitoring is not used routinely. This is because placement of a lumbar cistern drain allows for false low recordings of ICP despite clinical evidence of cerebral edema. This may lead to a tardy diagnosis of elevated ICP or intracranial hemorrhage. Because of this, pain control postoperatively should still allow for clinical assessment of neurological status.
Complications Complications from the operative procedure are relatively few. The major immediate concerns relate to cerebral edema and/or intracranial hemorrhage and injury to the visual system, either to the globe or optic nerve by trauma or hematoma, or to the extraocular muscle system. Also, it is important to note that if sufficient bone is not removed from the medial portion of the cribriform plate as the orbit is translocated medially, there is the possibility of impingement of the medial rectus muscle on the corner of the remaining bone. This may require reoperation to correct. Later concerns include cerebrospinal fluid leakage, subdural or epidural infection, and osteomyelitis. The possibility of cerebrospinal fluid leakage and meningitis should be significantly reduced by watertight dural closure supported by the use of fibrin glue at the suture line, with further support by the pericranial flap overlying the dural closure. Unresolved problems are soft tissue relaxation at the medial canthal region resulting in an apparent redevelopment of hypercanthorum, and the possibility of growth disturbance on the nasomaxillary and midface regions with surgery performed in early childhood.
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Figure 5–4 (A) A bifrontal craniotomy is performed with a 1 cm tall supraorbital bar left above the apex of the orbital rim. It is bisected leaving a 5 mm thick supraorbital rim that may be translocated medially, following removal of paramedian frontal and nasal bone (green), and a 5 mm supraorbital bar to which the orbital rim bone is affixed. (B) Note resection of the nasal process of the maxilla to avoid impingement on the nasal airway. (C) The orbits are then translocated medially. (D) Bone grafts are inserted posterior to the lateral rim of the orbit and in the region of the sigma to prevent a postoperative “hourglass” deformity. A drill is used to trim the lateral portion of the supraorbital bar. (E) The normal position of the lateral canthus is approximately at or 2 mm above the level of the medial canthus. 10.1055/978-1-60406-039-3c005_f004
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(F) Drill holes are placed in the frontal process of the zygoma. The lateral canthus is attached transosseously to the internal surface of the zygomatic process of the frontal bone, if the patient does not demonstrate globe proptosis. (G) If the patient has accompanying significant proptosis, the canthus is placed on the external surface of the sigma in an effort to reduce the malrelationship between the globe and the eyelids and to restore normal lid-globe anatomical relationships. (H) A slight overcorrection of the lateral fissure position superiorly will allow normalization of its position with subsequent soft-tissue relaxation. (From Persing J, Edgerton M, Jane J, Eds, Scientific Functions and Surgical Treatment of Craniosynostosis 1989. Baltimore: Williams & Wilkins Reprinted by permission.)
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6 Ventriculoatrial Shunting John Drygas and Stephen J. Haines
The ventriculoatrial (VA) shunt was introduced as a method of treatment for hydrocephalus in the 1950s and was the first predictably successful valve-regulated cerebrospinal fluid (CSF) shunt. Technical developments have since made ventriculoperitoneal (VP) shunts reliable and because they are easier and quicker to insert and revise, and have less propensity to systemic bacteremia if infected, they are the initial treatment of choice for hydrocephalus for most patients. VA shunts are now the second most common shunt procedure, representing 2 to 10% of all implanted shunts in recent series. Where both VP and VA shunting are contraindicated, shunts to the pleural space, the gall bladder, the ureter, the bone marrow, the subarachnoid space, and other areas, including direct heart catheterization, have been reported to be successful.
Patient Selection VA shunts are indicated for the treatment of hydrocephalus, either obstructive or communicating, which is not transient in nature or amenable to endoscopic third ventriculostomy. Other indications for shunting, which may occasionally require VA shunting, include the treatment of pseudotumor cerebri and drainage of arachnoid cysts and subdural hygromas that are unresponsive to other therapeutic measures. There are some patients in whom a VA shunt is the procedure of first choice, such as those patients with fibrosis or inflammation in the peritoneum from remote or recent infections or multiple previous abdominal operations. The peritoneal cavity or pleura of some patients, particularly small infants, may occasionally not have sufficient absorptive capacity to handle the necessary amount of CSF.
Contraindications Bacteremia or infection of the CSF or proposed shunt tract are absolute contraindications to the placement of a VA shunt. In the presence of infection elsewhere in the body, a shunt should be inserted only in very unusual circumstances. Congestive heart failure and pulmonary hypertension may both interfere with shunt function and be aggravated by the additional fluid load delivered to the heart; these are relative contraindications to the procedure, especially in infants.
Abnormal venous anatomy, previous jugular or subclavian vein thrombosis, and unusual cardiac irritability are relative contraindications.
Preoperative Preparation Preoperatively the patient and his or her parents are informed that the major risks of the procedure are those of infection approximating 8% and shunt malfunction of up to 40% in the first year, either of which would necessitate revision or replacement of the shunt. When a VA shunt is placed in an infant, malfunction due to growth-related migration of the atrial catheter into the superior vena cava (SVC) is so predictable that elective revision at about 2 years of age has been recommended by some. There is a slight risk of intracranial hemorrhage (which may be increased in patients with marked hydrocephalus). Rare surgical risks of air embolism, cardiac rupture and tamponade, and thromboembolism are mentioned, as are the attendant risks of general anesthesia. Remote risks include immune complex glomerulonephritis and pulmonary hypertension from chronic thromboembolism or volume overload. Where possible, an antiseptic scrub is administered preoperatively for both inpatients and outpatients. The hair may be shaved immediately preoperatively, although recent studies suggest that this is not necessary. An appropriate dose of an anti-staphylococcal antibiotic is administered at least 30 minutes prior to incision. This has been shown to reduce infection in standard surgical procedures and in shunt procedures with an infection rate higher than 5%.
Anesthetic Considerations Most patients with hydrocephalus can be presumed to have some degree of increased intracranial pressure (ICP). Because of this a gentle anesthetic induction is preferred, being careful to avoid any manipulations that would increase ICP, that is, Valsalva maneuvers, coughing, prolonged hypoventilation. Appropriate inhalational or intravenous anesthetics that decrease ICP and preserve cerebral autoregulation are used, combined with hyperventilation if deemed necessary. Succinylcholine is avoided because of its propensity to increase ICP.
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Special Equipment An ultrasound imaging system is very useful for cannulating the vein for placement of the distal catheter and for visualizing the ventricle in infants with an open fontanelle. A C-arm fluoroscopic unit is extremely helpful in verifying correct catheter placement. Operating room personnel must remember to don lead aprons prior to scrubbing. It is also useful to have intravenous contrast material available. Heparinized saline is necessary to flush the atrial catheter, as well as an antibiotic saline solution with which to irrigate the shunt system and wounds. The appropriate shunt system is chosen preoperatively. Programmable valves may be used. The distal atrial catheter should have a radio-opaque marker of some type to aid in identification on images. There is some suggestion that antibiotic-impregnated shunt catheters may reduce the risk of shunt infection. A central venous pressure or electrocardiogram (EKG) monitoring device must be available to monitor pressure waves or EKG tracings as the atrial catheter is advanced if these methods are to be used for locating the tip of the atrial catheter.
Figure 6–1 (A) Lateral and (B) vertex views of incision landmarks and (C) side view of padding placed under the head and shoulders for optimal positioning. Note the intersecting lines drawn to represent two planes. The ventricular catheter should be passed along the line that is the intersection of these two planes. 10.1055/978-1-60406-039-6c006_f001
Operative Procedure Positioning The basic principle of positioning the patient is to provide clear access to the head for ventricular puncture and to the neck for cannulation of the venous system. Therefore, following induction of satisfactory general endotracheal anesthesia, with the patient in the supine position the head is turned to the appropriate side. In the preferred setting, the head is turned to the left to provide access to the right neck. Because of the vascular anatomy, right-sided cannulations are often easier than left-sided ones. The ear maybe taped forward and thereby easily draped out of the field. Soft padding is placed beneath the shoulders to expose the anterior triangle of the neck (Fig. 6–1C). The skin and/or hair in the operative field and surrounding area is then prepared with an appropriate antiseptic. Prior to draping, the landmarks for ventricular access and access to the venous system are drawn on the skin (Figs. 6–1A and 6–1B). A mark is placed ~2.5 to 3 cm from the midline and 11 to 12 cm posterior to the nasion in the adult (or approximately one-seventh of the distance from the coronal suture to the nasion in the child). A line is then drawn from this mark toward the inner canthus of the ipsilateral eye. Another line is drawn that passes through this point and a point midway between the tragus and the lateral canthus of the ipsilateral eye. If these lines are taken to represent imaginary planes in partial sagittal and coronal directions, their intersection forms a line that should pass through the foramen of Monro (Fig. 6–2). Sterile drapes are then applied in such a manner as to allow for access to head and neck sites. In draping the head, it is helpful to place a sterile towel with one border on the midline to use as a landmark in placing the bur hole. If intraoperative ultrasound is to be used in the case of an infant, the anterior fontanelle should be draped into the operative field.
Figure 6–2 A ventricular catheter traveling along the intersection of the two drawn planes will be directed at the foramen of Monro. 10.1055/978-1-60406-039-6c006_f002
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36 Pediatric Neurosurgery The shunt hardware, including ventricular and atrial catheters, valve system, reservoir, and connectors, should be chosen before the procedure, opened, and placed in an antibiotic-saline solution on the instrument table before the incision is made. We generally use gentamicin and avoid the use of bacitracin because its foaming action may interfere with the function of some valves. Unless a programmable valve is to be used, it is prudent to have several valves with different pressures readily available. The valve system to be used should be tested according to the manufacturer’s recommendations to ensure its appropriate function. (Most manufacturers now advise that although patency testing is sensible, specific pressure testing in the operating room cannot reproduce laboratory testing requirements and therefore cannot accurately evaluate the functioning pressure of the valve. Therefore we only evaluate patency at the time of surgery.) It should be filled with saline solution, have all air bubbles removed, be connected to distal and proximal tubing with permanent suture, and be clamped on the proximal end with a mosquito clamp shod with suture boots to keep it full of fluid. To the greatest extent possible, one should avoid touching the skin and shunt system with the gloved hand to minimize the risk of postoperative infection. It is also recommended that the shunt system not touch cloth drapes, as electrostatic forces may cause cloth fibers to adhere to the shunt and be implanted with it.
Steps The operation is performed in a logical, stepwise fashion. We prefer to place the ventricular and vascular catheters as the last part of the operation because of the risk of dislodging either catheter before it is secured in final position.
Step One—Percutaneous Access of the Internal Jugular Vein or Isolation of the Common Facial Vein We prefer to use a percutaneous technique similar to that used for placing central venous catheters. Usually the internal jugular vein is used for access, though the subclavian may be used, and the procedure is identical to cannulation for standard central venous catheters. For the internal jugular vein, a thin-walled, 18 or 20 gauge needle that is contained in most central venous access kits is used. The skin is punctured ~4 to 6 cm (2–3 finger breadths) above the clavicle between the heads of the sternocleidomastoid muscle or a proportionate distance in a child. The tip of the needle should be aimed at the sternal notch (Fig. 6–3). Alternatively, the carotid artery can be palpated and the needle aimed lateral to it. The use of ultrasonic guidance by the surgeon can facilitate the percutaneous access to the internal jugular vein from the most routine adult to the most difficult pediatric patient. For the subclavian vein, the needle is inserted just below the junction of the middle and inner thirds of the clavicle and aimed at the sternal notch. Once the vein is punctured, the syringe is removed and a flexible J-wire (0.021 in. in diameter for older children and adults) is inserted through the needle; its position can be checked with fluoroscopy. The needle is removed when the wire is verified to be in the SVC. A small incision is made
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Figure 6–3 Guidelines for percutaneous placement of the atrial catheter. 10.1055/978-1-60406-039-6c006_f003
at the point of entry to facilitate passage of the introducer and to connect the shunt system with the atrial catheter and bury it. A standard, tear-away introducer sheath over a vessel dilator is then passed over the wire through the subcutaneous tissue and into the vein. The wire and dilator are removed, and a finger is placed over the sheath to prevent the introduction of air. The atrial catheter can now be threaded through the sheath to its proper position described in Step Four below. If percutaneous access is unsafe or not possible, the open approach through the common facial vein may be used. To isolate the common facial vein, a 2 cm transverse neck incision is made one finger breadth below and parallel to the ramus of the mandible in an adult, and a proportionally smaller distance below the jaw in children. This should be centered just medial to the medial border of the sternocleidomastoid muscle (Fig. 6–4). The platysma is split in the direction of its fibers, and using a combination of blunt and sharp dissection along the avascular plane medial to the sternocleidomastoid muscle, the common facial vein is identified. The vein is isolated for ~1 cm of its length, and
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Step Three—Placement of the Valve System At this point the valve system is passed subcutaneously from the cranial incision to the neck incision, passing in front of the parietal boss and behind the ear. Care must be taken to avoid the very thin skin just behind the ear and not to have the bulky portion of the valve or reservoir over a bony prominence where it may cause pressure erosion of the skin. Depending on the size of the patient, a small transverse incision may be necessary behind the ear so that the distal tubing may be passed the remainder of the distance to the neck incision. The proximal shunt system tubing is then cut to the appropriate length. Both ends of the system are clamped with rubber shod clamps to maintain the system fluid-filled and free of air bubbles, and to avoid inadvertently pulling the tubing out of the incision, and they are covered with sponges moistened in an antibiotic solution. The purpose of placing the valve-reservoir system first is to minimize the number of manipulations once the vein and the ventricle have been catheterized. When the venous or ventricular catheter is placed early in the procedure, it may be dislodged inadvertently. Because of this possibility, we then place the atrial catheter, and we place the ventricular catheter last.
Step Four—Placement of the Atrial Catheter
Figure 6–4 Complete ventriculoatrial shunt in place. 10.1055/978-1-60406-039-6c006_f004
two ligatures of a size appropriate to the size of the vessel are placed around it. The vein is then ligated using the most cephalad tie.
Step Two—Placement of a Cranial Bur Hole The ventricular catheter may be placed into the frontal or occipital horn of the lateral ventricle depending on the preference of the surgeon and the individual patient’s ventricular anatomy. We prefer the frontal approach because our experience indicates that such shunts function better than parieto-occipitally placed ones, although the evidence in this regard is contradictory. The patient’s nondominant hemisphere is selected because of the remote risk of parenchymal damage caused by hemorrhage at the site of insertion. A curved incision is made with its base directed inferiorly so that no portion of the incision will be overlying the shunt apparatus. A subgaleal pocket is created using blunt dissection to allow placement of the valve system. The bur hole is then made using a standard hand or power drill at the predetermined site, bone wax is applied, and the exposed dura is covered with a saline-soaked sponge or cottonoid patty until later in the procedure.
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The goal in placement of the atrial catheter is to position the catheter midway between the SVC–right atrium junction and the tricuspid valve. A variety of techniques are available to confirm this placement, the least reliable of which is the chest x-ray, upon which we do not rely. A more accurate, yet simple, way of correctly placing the catheter utilizes continuous pressure wave recordings as the catheter is advanced. Another simple technique optimizes the EKG recording of the right atrium, using the shunt tubing as an EKG lead. The atrial catheter is introduced into the jugular vein either through the percutaneous sheath or directly through the common facial vein or jugular vein. In the latter cases a purse string suture should be placed prior to making the venotomy. The ligature is cinched around the catheter just enough to prevent back bleeding yet allow the catheter to advance easily. The catheter has been filled with an isotonic heparinized saline solution with the proximal end connected to a pressure transducer or EKG monitor for continuous monitoring in a closed system, and to prevent air aspiration. When attached to a pressure transducer a characteristic change is noted as the catheter is advanced first from the SVC into the right atrium and then into the right ventricle (Fig. 6–5). The catheter is then withdrawn until the atrial pressure tracing is again identified. Fluoroscopy is often used during advancement of the catheter. If necessary, the catheter may be made more visible by the injection of an appropriate quantity of contrast material. When the proper position has been identified, the position is maintained by clamping the catheter with a shod mosquito clamp. If there is a ligature around the catheter, it is tied around the catheter so that it cannot move but still will permit free flow of CSF. The catheter should be aspirated to remove air bubbles and then flushed with
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38 Pediatric Neurosurgery
Figure 6–5 Typical pressure wave form readings seen with advancing catheter positions. 10.1055/978-1-60406-039-6c006_f005
heparinized saline. A shod clamp is placed proximally, and a straight connector is tied to the proximal end of the catheter, which is then covered with an antibiotic-moistened sponge.
tip and an internal stylet in place is then advanced through the dural opening utilizing the guidance lines and planes described above in Fig. 6–2 until CSF return is evident. (We do not use flanged ventricular catheters because of the tendency of the choroid plexus to grow into the interstices of the catheter. This can lead to intraventricular hemorrhage when the catheter is removed during a revision.) Usually the resistance encountered when the catheter pops through the ventricular ependymal surface is easily felt. The stylet is then removed and the catheter advanced ~1 cm. A depth of 5 to 6 cm is usual in adults and is proportionally less in children. A manometer may be connected to the catheter, and the ventricular pressure may be measured and recorded. The catheter is then clamped with a shod clamp, cut, and connected to the valve system with a permanent suture, keeping the knot on the side to prevent skin erosion. The connector should then be secured to the periosteum with a single stitch to prevent migration out of the ventricle during growth or movement. The system is now inspected to ensure spontaneous flow of CSF from the valve’s distal tubing, and the atrial catheter is again aspirated and flushed and connected to the valve system with the previously placed straight connector and a permanent suture. The sutures can be tied across the connector, to further protect against disconnection. There should be no excess slack at this connection. The position of the atrial catheter is again checked fluoroscopically. The tip of the catheter should be seen overlying the seventh thoracic vertebra. The ventricular catheter position can also be checked fluoroscopically. By use of intraoperative fluoroscopy one can avoid leaving the operating room with an inadvertently poor catheter placement. All wounds are inspected and irrigated with antibiotic-saline solution and then closed in the standard fashion. The galea is first closed with interrupted 3-0 or 4-0 absorbable sutures, and the skin is closed according to the surgeon’s preference. In children we use 4-0 or 5-0 absorbable monofilament suture, which avoids the need for suture removal. In adults fine nylon suture is often used. The posterior auricular and cervical incisions are closed in two layers, and sterile dressings are applied.
Intraoperative Problems
Step Five—Placement of the Ventricular Catheter
Difficulty in Locating the Ventricles
The goal in placement of the ventricular catheter is to place the tip in the frontal horn just anterior to the foramen of Monro. In an infant, ultrasound through the anterior fontanelle can often be used to direct the catheter placement in this fashion. The center of the exposed dura is coagulated with a needle-point monopolar cautery to create an opening with a diameter equal to that of the catheter. This reduces the risk of CSF egress around the catheter, reducing the incidence of CSF leak, especially in pediatric patients with a thin cortical mantle. The catheter should be marked in some fashion so that it is not advanced excessively (beyond 7 cm in the adult). A ventricular catheter with multiple side holes at its
We find the above method of passing the catheter most successful in cannulating the anterior part of the frontal horn of the lateral ventricle. If unsuccessful, three passes are made at slightly different mediolateral angles, at no time passing the catheter to a depth greater than 7 cm in an adult. Passing the catheter perpendicular to a plane tangent to the skull at the point of entry is often helpful. As mentioned, ultrasound can be used in a child with an open anterior fontanelle, or in an adult by creating an adjacent bur hole. If difficulty in ventricular catheter placement is anticipated (usually because of slit ventricles) image-guided catheter placement (frameless or framed stereotaxy) should be used.
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Difficulty Passing the Atrial Catheter in a Patient with Normal Vascular Anatomy
the ICP is particularly high to protect against collapse of the cerebral mantle.
Once the catheter enters the vein, it usually passes straight into the SVC and right atrium. If any difficulty is encountered, a standard J-wire commonly used for central vascular access can be passed into the vein and almost always easily directed into the atrium under fluoroscopy. The catheter can then be threaded over the wire.
Complications
Difficulty Passing the Atrial Catheter in a Patient with Abnormal Vascular Anatomy If a problem with venous access is anticipated, such as a patient who has had multiple VA shunts, previous SVC or jugular thrombosis, or multiple previous central venous access lines, it is advisable to obtain preoperative venography to define the anatomy. Where the internal jugular has been previously sacrificed or thrombosed, the external jugular may be of use. It is also possible with the aid of an interventional radiologist to catheterize a femoral or hepatic vein in a retrograde fashion using an angiographic catheter. One may then cut down directly on the wire or snare, and this may be used to direct the catheter into the atrium.
Difficulty Positioning the Atrial Catheter We find the method of using continuous pressure recordings the easiest and most accurate way of placing the tip of the catheter correctly in the atrium. The use of contrast material under intraoperative fluoroscopy is another method. Or, using the saline-filled atrial catheter as an EKG lead, the characteristic biphasic P-wave changes seen in the atrium may be identified. Two-dimensional intraoperative echocardiography has also been used successfully for this purpose, but is technically cumbersome.
Postoperative Management Including Possible Complications Antero-posterior and lateral x-ray films of the skull and thorax should be obtained within the first 2 postoperative days to verify catheter positions and continuity of the system. Since the C-arm was used for the thoracic localization, it can be directed cranially for ventricular catheter localization before leaving the operating room. A computed tomography scan should be done a few weeks after surgery in the case of a first-time shunt placement to document ventricular size at a time when the shunt is known to be functional. This can be invaluable in assessing shunt function in the future. We monitor the EKG for the first 24 hours postoperatively because of the possibility of arrhythmia. One may wish to nurse the patient in the supine position for the first day if
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Malfunction of the shunt system and infection are the two most common complications of the procedure and may occur at any time after operation, including in the recovery room. The former may be a consequence of an indolent CSF infection, obstruction of any part of the valve or tubing by proteinaceous debris or fibrosis, or disconnection. We believe the technique of securing all connections with a nonabsorbable suture tied across the connector can help prevent disconnection. Infection can be minimized by the use of perioperative antibiotics, by keeping the handling of the shunt system to a minimum, and possibly by the use of antibiotic-impregnated shunt materials. When at all possible, the system should be manipulated with instruments rather than with the gloved hand. When tapping the shunt reservoir the skin should always be adequately prepared with an appropriate antiseptic. Patients with a VA shunt should be advised to follow standard bacterial endocarditis antibiotic prophylaxis before any surgical or dental procedure. Significant but rare complications include pulmonary venous thromboembolism, pulmonary hypertension, sepsis, immune complex glomerulonephritis, and hemorrhage from erosion of the SVC. Elective revision can be anticipated after 2 years in an infant or child due to growth-related migration, which can be followed by routine thoracic radiographs.
Conclusion Ventricular shunting procedures are commonly thought of as “minor” neurosurgical procedures. Given short shrift in training and low priority in practice, the operation may give suboptimal results. However, with meticulous technique and skillful execution, the VA shunt can be a safe and effective alternative in the neurosurgeon’s armamentarium for the treatment of hydrocephalus in patients who would not benefit from endoscopic third ventriculostomy or VP shunt. Acknowledgment This chapter is a revision of the chapter, “Ventriculoatrial Shunting” by Paul J. Camarata, M.D. and Stephen J. Haines, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 1, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Paul J. Camarata, M.D., for his help and efforts on the original chapter published in the first edition of this work.
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7 Repair of “Growing” Skull Fracture Tadanori Tomita
Growing fracture is a rare complication of skull fracture occurring in infancy and early childhood. This late complication of skull fracture is also known as a leptomeningeal cyst. “Growing” fracture is somewhat of a misnomer, but it is characterized by progressive diastatic enlargement of the fracture line. Although skull fracture is a common occurrence in the pediatric age groups, the incidence of growing fracture is only 0.05 to 1% among skull fractures in childhood.
Patient Selection The usual presentation of the growing fracture is a progressive, often pulsatile, lump on the head. Neurological symptoms such as seizure, hemiparesis, and mental retardation are less frequent. Often these patients are perfectly asymptomatic, and a palpable mass or widening of the fracture line is the sole sign of neurological sequalae noted incidentally by the parents. Usually a growing fracture develops within a few months following the initial skull fracture, but it may not be recognized for many years. Growing skull fractures usually occur during the first 3 years of life (most often during infancy), and almost never occur after 8 years of age. Although fractures may form in any part of the skull, the most common site for growing fracture is over the skull vault in the parietal region. Dural laceration is always present along the fracture line, and it is an essential factor for the development of a growing fracture. The dural laceration enlarges with the growing fracture. Computed tomography (CT) or magnetic resonance imaging (MRI) often demonstrates a focal dilatation of the lateral ventricle near the growing fracture. Lack of resistance of both dura and skull leads to focal amplification of the pulse wave of the intracranial pressure, causing herniation of the brain or subarachnoid space through the fracture line and the dural defect. The “growth” of the fracture line is caused by bone resorption due to continuous pulsatile pressure at the edge of the fracture line. A rapidly developing infantile brain and associated pathological conditions such as brain edema or hydrocephalus also contribute an outward driving force to cause brain herniation through the dural and skull defect. This pulsatile force of the brain during the period of its rapid growth produces the brain herniation through the dural laceration and fracture line, causing the enlargement of the fracture line of the thin skull.
One of the risk factors for the development of a growing fracture is the severity of head trauma. A linear skull fracture with underlying hemorrhagic contusion of the brain suggests a severe injury, significant enough to cause a dural laceration. Initial CT scans for the evaluation of head trauma in patients who ultimately develop a growing fracture usually reveal significant hemorrhage or contusion subjacent to the skull fracture. When a growing fracture is inspected at the time of surgical repair, the herniated brain is seen to be developing a cerebromeningeal cicatrix. In some cases, loculated subarachnoid cerebrospinal fluid (CSF) cyst(s) may be noted with underlying gliotic, atrophic brain. Although the loculated subarachnoid apace may become cystic (leptomeningeal cyst), true leptomeningeal cysts are rare. The cystic changes in the growing fracture usually represent cystic encephalomalacia. Depressed fractures usually do not cause growing fractures, but a linear fracture extending from the depressed fracture can lead to a growing fracture. The child who on initial x-ray films of the skull has diastasis of the fracture >4 mm is considered to be at risk for future development of a growing fracture. Diastasis of a cranial suture, however, is an unusual site for a growing fracture. A growing fracture at the skull base can occur in an older age group, especially where the bone is thin such as in the orbital roof, if a linear fracture is accompanied by a dural laceration. Growing fracture and a meningoencephalocele can develop with a similar mechanism as those occurring in the skull vault of the young patient.
Radiological Studies X-ray films of the skull show wide diastases of the fracture line. If initial skull films are available, one can compare the films to confirm “growth” of the fracture line during the interval. When multiple fractures are noted in the same patient, healing of the fracture in one area may be noted as opposed to a growing fracture in another area. The fracture line can cross the coronal or lambdoid sutures but is usually limited to one parietal bone. Neuroimagings such as CT and MRI provide information regarding the sequelae within the growing fracture and any intracranial pathological changes. Furthermore, if they are available from the time of initial trauma, it should be possible to demonstrate progressive changes. It is not unusual that the initial neuroimagings show hemorrhagic contu-
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sion, or subarachnoid or extraparenchymal hemorrhage. At the time of discovery of the growing fracture, neuroimagings demonstrate the diastasis of the fracture line and often cystic lesions near the fracture site. These cystic lesions represent encephalomalacia, a loculated arachnoidal cyst, or cortical atrophy. The ipsilateral ventricle tends to show focal porencephalic dilatation with ipsilateral shift of the midline structure. This phenomenon may be due not only to lack of dural resistance but also to cerebral atrophy.
Management Surgical intervention is indicated with a growing fracture line, seizure disorder, or progressive neurologic deficits. A progressive cystic degeneration in the brain that has herniated through the dural and cranial defects can occur; therefore, surgical correction is recommended in young children even when seizures or other neurological symptoms or signs are absent. However, incidental, asymptomatic, and stable fractures in late childhood or adulthood probably do not require surgery. The goal of surgery for growing skull fractures is to repair the dural laceration and cranial defect, and to resect seizure foci. Growth of the growing fracture may arrest after CSF diversion shunting by a decrease of the CSF pulse pressure, but this does not correct a seizure disorder. Placing a shunt for primary treatment of these patients is not advised unless hydrocephalus is present. Shunting for nonhydrocephalic patients creates undesirable shunt dependency.
Operative Procedure The scalp incision should be large enough to expose the entire length of the skull defect. An S-shaped or semicircular skin incision is made, and the scalp flap is turned subgaleally, leaving the underlying periosteal tissue intact (Fig. 7–1A). By palpation, the entire length of the cranial defect covered by pericranium is exposed in surgical view. The site of the cranial defect is often bulging and may be accompanied by blush appearance due to an underlying subarachnoid cyst. As the cranial defect is dissected by incising the pericranium along the edge of the bony defect (Fig. 7–1B), soft tissues adherent to the edge of the cranium defect are scraped off by a sharp dissector. The surgeon should remember that the dural edge is invariably larger than the cranial defect, and that the pericranium is directly adherent to the underlying cerebral tissue at the cranial defect. An effort to expose the dural edge by removing the cranial edge should not be undertaken, as this procedure is often complicated by removing the dura simultaneously with the skull bone due to the adhesive nature of the dural edge. To identify the dura, several bur holes are made away from the skull defect with a distance of at least 50% of the width of the cranial defect. At this time, a large enough amount of pericranium is removed from the neighboring skull to use it for repair of the dural defect. Once the dura is identified at each bur hole site, the dura is separated from the inner table of the skull toward the defect (Fig. 7–1C). A craniotomy is made around the skull defect by connecting the bur
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Figure 7–1 (A) The scalp flap is turned subperiosteally. The cranial defect is usually covered by the pericranium. (B) The pericranium is incised along the edge of the cranial defect. Then, the edge of the cranial defect is exposed by scraping off the soft tissues adherent to it. (C) The pericranium is removed from the surrounding skull surface and preserved for dural repair. Four bur holes are made in the surrounding skull for a craniotomy. After the confirmation of intact dura matter under the bur hole, the dura is separated from the bur hole toward the cranial defect. The surgeon should not attempt to identify the dura by removing the bone from the edge of the cranial defect. The craniotomy is performed on both sides of the growing fracture. The two bone flaps are removed and preserved for autologous bone cranioplasty. 10.1055/978-1-60406-039-3c007_f001
holes with a craniotomy. Two pieces of the craniotomy flap are obtained, one from each side of the growing fracture. After the craniotomy is completed (Fig. 7–2A), reactive periosteal tissue and the cerebromeningeal cicatrix are identified in the dural defect. Under magnified vision by means of surgical loupes, the cicatrix including the periosteal tissue is lifted, and all abnormal tissue is separated and transected using a bipolar cautery until normal white matter is exposed (Fig. 7–2B). The edge of the dura is separated from the cerebral tissue, carefully avoiding trauma to the cerebral blood vessels. In this region, abnormal tissue such as cystic changes or xanthochromic discoloration due to previous hemorrhage is often noted. After adequate debridement of the cicatrix at the growing fracture and freeing of the intact dural edge from the cortical surface, the dural defect is closed using the periosteal graft (Fig. 7–2C). Autologous pericranium is preferable to cadaver dura. A watertight closure of the dura is important to avoid a recurrence of the growing fracture or postoperative CSF leakage. Each of the obtained craniotomy flaps is split at the diploic space with an osteotome, separating it into inner and outer tables (Fig. 7–2D). The cranial defect is then repaired
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42 Pediatric Neurosurgery by laying in the split autologous skull grafts. Usually four pieces are laid next to each other side by side to fill the cranial defect. These flaps are secured to each other with either nylon sutures or stainless steel wires through drill holes (Fig. 7–2E). These flaps are further secured to the craniotomy edge. If the defect of the skull is too large or the skull is too thin to separate into inner and outer tables, one may consider autologous rib grafts. These autologous bone grafts are well incorporated, and healing is excellent. Foreign materials such as methyl methacrylate should be avoided for cranioplasty in the growing skull.
Specific Considerations The growing fracture may extend toward a dural venous sinus such as the superior sagittal or lateral sinus. Although these venous sinuses were spared from direct injury at the initial trauma, direct exposure of them is not advised or
necessary. When the fracture line extends perpendicularly to these sinuses, the closest end to the sinus does not need dural repair. However, if the growing fracture is parallel and near to the sinus, dural repair may be difficult due to the lack of enough dural edge next to the sinus. In these cases, one may repair the dural defect with a periosteal graft sutured to the periosteum of the skull above the sinus.
Postoperative Management Including Possible Complications CSF diversion shunting has been recommended for persistent postoperative CSF leakage from the craniotomy wound. It is justified if coexisting hydrocephalus is evident, or if CSF leakage occurs despite adequate repair of the growing fracture. A lumboperitoneal shunt or temporary lumbar CSF drainage is to be considered under these circumstances.
10.1055/978-1-60406-039-3c007_f002 Figure 7–2 (A) After the craniotomy, the intact dura mater is exposed around the dural defect, which is covered by the periosteum. Underneath the overgrowing periosteum is a cerebromeningeal cicatrix that is removed using bipolar cautery and sharp dissection until healthy white matter is exposed. (B) After all pathological tissues have been removed, the edge of the surrounding dura is separated from the intact cortical surface. (C) The previously removed periosteum is used to repair the dural defect. A watertight closure is achieved with 4–0 sutures. (D) The bone grafts are split at the diploic space between the inner and outer tables by means of an osteotome. (E) The obtained split bone flaps are used to repair the cranial defect. The bone flaps are secured to each other and to the edge of the cranial defect with nylon sutures or stainless steel wires.
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8 Occipital Encephaloceles William O. Bell
Encephaloceles are uncommon congenital malformations of the central nervous system (CNS) occurring in ~1 to 3 of every 10,000 live births in Western civilization. Seventy to eighty percent of all encephaloceles occur in the occipital area, with the remainder located anteriorly or at the base of the skull. In the Far East, anterior and skull-base encephaloceles are the most common, and cranial CNS malformations are more common than spinal malformations. Occipital encephaloceles range in size from quite small (1–2 cm) to larger than the neonate’s head. Almost all are covered with partial-thickness skin, although the skin over smaller defects is usually full-thickness. Identification of these anomalies is usually straightforward as they are almost always quite obvious. In my experience the majority of encephaloceles are small, sessile, and nearly planar with the surrounding skin, thereby making their identification somewhat more difficult. The presence of an encephalocele can have prognostic implications, especially if hydrocephalus is also present. The occurrence of hydrocephalus in the presence of encephalocele is due to aberrant development of the brain stem and cerebrospinal fluid (CSF) pathways. Hydrocephalus may be present at birth or develop following repair of the encephalocele. Up to 50% of infants with a large occipital encephalocele will require a CSF shunt for control of hydrocephalus. However, hydrocephalus is rare in small, skin-covered encephaloceles.
Patient Selection All except the very smallest encephaloceles must be repaired, but because the majority of these are covered with skin, there is no emergent need to take the child to surgery within 24 to 48 hours of birth. This delay allows adequate time for preoperative planning and a full discussion of the implications of an encephalocele with the infant’s parents. Although the risk of seizures after repair is high, I do not begin prophylactic anticonvulsants preoperatively but wait for seizures to occur before starting these drugs. Smaller encephaloceles are usually slightly raised with darker, thicker hair at the central portion. They are covered by full-thickness skin and invariably are located at the vertex. Operative closure of these very small encephaloceles is not a necessity, but I recommend it for cosmetic purposes.
In my experience many of these lesions are hyperpathic and should be excised for the comfort of the infant. For these smaller lesions I recommend waiting until the infant is 3 to 6 months of age for excision, as that allows the anesthesia and surgery to be less risky.
Preoperative Preparation Operative closure/excision of an occipital encephalocele is usually straightforward, as long as certain important points are kept in mind. A computed tomography (CT) or magnetic resonance imaging (MRI) scan should be obtained preoperatively to assess the intracranial contents for gross brain structure and ventricular size. I prefer a CT scan using 3 mm cuts because the information sought can be obtained easily by this procedure and monitoring the infant during an MRI scan may be problematic. Current-generation CT scanners can obtain the necessary information in a matter of minutes. Very often, there are brain abnormalities that will affect prognosis, and these should be discussed with the parents before the operative repair is begun. The majority of occipital encephaloceles are located infratentorially. The exact locations of the major venous sinuses and their relationship with the encephalocele can be determined accurately with MRI if needed.
Operative Procedure A general anesthetic is required for this procedure. In the vast majority of instances, a balanced anesthetic technique is sufficient. The infant must be positioned prone (Fig. 8–1). If the encephalocele is large, this positioning will result in undue pressure being placed on the globes unless appropriate care is taken to keep the area of the orbits free from any encumbrance. I use umbilical tape around the padded horseshoe headrest at the level of the orbits for this purpose (Fig. 8–1). For lesions at the vertex, the neck may be placed in a neutral position, but for lesions in the suboccipital area, the neck must be flexed as much as possible for the surgeon to work effectively. For very large defects, I recommend that the encephalocele be suspended from an overhead device to allow proper skin preparation and to keep the weight off the head until the defect can be excised. The anesthesiolo-
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Figure 8–1 The patient’s position for repair of an occipital encephalocele. Note the umbilical tape around the horseshoe headrest at the level of the eyes and the rolls placed beneath the child. 10.1055/978-1-60406-039-3c008_f001
gist should be aware that the neck will be flexed and that this maneuver may change the position of the endotracheal tube once the child is turned prone. Extraordinary care must be taken to ensure that the endotracheal tube is securely taped and secured to avoid its dislodgement during the procedure. The child’s torso is placed on soft rolls oriented either vertically or horizontally, and care is taken to avoid any pressure points. I usually do not place an arterial line or a Foley catheter because these operations are neither bloody nor lengthy. I use 3M Steri-Drape1010 surgical drapes (3M, St. Paul, Minnesota) because they nicely establish the perimeter of the area to be draped and reduce the amount of exposed skin, thereby allowing the infant to retain body heat during the procedure. In addition, these drapes prevent the skin preparation solution, bodily fluids, and irrigation fluid from dislodging the tape holding the endotracheal tube in place. For skin-covered defects, I prepare the skin using diluted providone-iodine scrub, tincture of iodine, and alcohol in that order. For defects with exposed tissue, I use Betadine scrub and Betadine solution, followed by a normal saline rinse. This avoids applying alcohol to the exposed tissue. For small, skin-covered lesions, I recommend a horizontal ellipse-shaped opening encompassing the lesion. Dissection is done along the skull from all directions toward the skull defect. The skull defect most commonly measures in millimeters and has good-sized arteries and veins coursing through it. The periosteum surrounding the skull defect is usually thickened, and I excise this also. The dural defect is either very small or nonexistent and can be closed with a re-
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absorbable suture. If there is a substantial skull defect, then a piece(s) of bone can be harvested from the adjoining skull and placed into the defect. The skin is closed in a standard fashion with galeal and skin sutures. I recommend reabsorbable sutures for both layers. Undermining the scalp in the subgaleal space around the defect will ensure that there is no tension on the skin closure. For larger lesions, I open the encephalocele sac either vertically or horizontally with a scalpel and then use Metzenbaum scissors (Figs. 8–2A and 8–2B) to obtain a direct view of the interior of the sac. The walls of the sac may be resected or they may be everted with stay sutures (Fig. 8–2C), whichever provides the best exposure. Frequently, there are multiple concentric layers of arachnoid that need to be opened with forceps to expose the neural tissue that is located at the base of the encephalocele sac (Fig. 8–2C). What to do with neural tissue located outside the cranial cavity is somewhat controversial. Some have advocated pushing it back inside the cranium; others have suggested first performing electroencephalographic or evoked potential recordings to determine whether it is functional neural tissue. Whether the externalized tissue is functional or not, forcing it inside a cranium that has not been housing it may exacerbate hydrocephalus or disrupt intracranial dynamics. Histological sections of this external neural tissue invariably show disorganized neural tissue without layered cerebral or cerebellar cortex. The neurons are usually interspersed in a glial background in what appears to be a random manner. My usual practice is to excise the exposed neural tissue (Figs. 8–3A and 8–3B). Frequently, there are reasonably
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Figure 8–2 (A) The initial incision may be made vertically or horizontally and (B) then opened further with the scissors. (C) Generally, there are arachnoidal layers that must be opened with forceps so that the abnormal neural tissue at the base can be identified. 10.1055/978-1-60406-039-3c008_f002
large vascular channels (both arterial and venous) coursing through the tissue, and these must be electrocoagulated carefully with the bipolar forceps (Fig. 8–3A) before the scissors are used to excise the tissue (Fig. 8–3B). If the location of the major venous sinuses is known beforehand and reasonable care is taken during the excision, the torcular herophili and transverse sinuses are rarely encountered.
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There is always a dural defect, and it is always somewhat smaller than the associated skull defect. To obtain a watertight dural closure, I use the surrounding periosteum (Figs. 8–4A–8—4C). A no. 15 blade scalpel is used to incise the periosteum, which is then reflected with an elevator such as the Dingman periosteal elevator (Figs. 8–4A and 8–4B). The periosteum/dura is then closed with an interrupted or
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46 Pediatric Neurosurgery
Figure 8–3 (A) After careful electrocoagulation with the bipolar forceps, (B) the abnormal tissue is then excised with the scissors. 10.1055/978-1-60406-039-3c008_f003
running absorbable suture such as 4–0 Vicryl in a “vestover-pants” fashion (Figs. 8–4C and 8–5A). Because dura and periosteum have been used, this type of closure may allow some ossification of the skull defect, but complete ossification has been rare in my experience. If the skull defect is large, a piece of adjoining skull can be used to cover the defect, sutured in place with absorbable 3–0 or 4–0 sutures. The area from which the graft is taken will reossify quickly.
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The skin may be closed in a vertical, horizontal, or oblique direction. The first step toward closure of the skin is to trim away excess partial-thickness skin (Fig. 8–5B) and then to begin blunt dissection in the subgaleal space (Fig. 8–6A). The most distance for skin closure is obtained in the cephalocaudal direction, and it is for this reason that I usually choose a horizontal skin closure (Fig. 8–6B). The galea is closed with interrupted, buried 4–0 Vicryl sutures and the skin with a running 4–0 monofilament or re-absorbable su-
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Occipital Encephaloceles
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Figure 8–4 (A) The periosteum is incised with a scalpel and (B) then reflected using a periosteal elevator. (C) The dura is closed in a “vest-overpants” fashion using absorbable suture. 10.1055/978-1-60406-039-3c008_f004
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Figure 8–5 (A) Once the dural closure has been completed, the bone edges of the defect are identified. (B) The excess partial-thickness skin may then be trimmed. 10.1055/978-1-60406-039-3c008_f005
ture. I prefer a re-absorbable stitch for skin closure because this eliminates the need for suture removal in a squirming infant postoperatively.
sion until adequate healing has occurred, and that one be vigilant for developing hydrocephalus. Before the infant is discharged from the hospital, if overt hydrocephalus has not developed, a follow-up CT scan or ultrasound study should be obtained as a baseline.
Postoperative Management Including Possible Complications Postoperative care is routine, with the only admonition being that the infant be kept from lying directly on the inci-
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Figure 8–6 (A) Undermining is done in the subgaleal space to allow for skin mobilization sufficient for closure. (B) After the galea is closed, the skin is closed using a running monofilament suture. 10.1055/978-1-60406-039-3c008_f006
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9 Surgical Management of Pansynostosis (Craniosynostosis) James Tait Goodrich and David L. Staffenberg
Patient Selection Children born with severe pansynostosis are usually diagnosed at birth or very shortly thereafter. The craniofacial team is ideally notified of the child’s condition very early on, and is involved in the surgical planning as soon as possible. The most important factor in timing the surgery is the presence of increased intracranial pressure (ICP). In our experience, almost all children born with pansynostosis have increased ICP (>90%). The most difficult child to sort out is one with pansynostosis secondary to microcephaly. Fortunately a good pediatric workup and genetic screen can isolate this child. The typical pansynostotic child has all the signs of increased ICP including severe “beaten metal” appearance or “thumbprinting” of the skull. There are usually associated clinical signs of lethargy, increased irritability, early signs of developmental delay, and so on. In some cases these signs or symptoms present so early that the surgery has to be scheduled within the first month of life. This leads us into the surgical timing problems that involve multiple considerations.
Preoperative Preparation Timing of Surgery and Other Preoperative Considerations Children with pansynostosis are typically diagnosed within the first 2 or 3 weeks of life, if not at birth. In craniofacial surgery, the ideal time in elective cases is 4 to 6 months of age. This growth period allows for an ideal surgical weight plus a fully developed hematological system. In children with severe pansynostosis and associated constricted calvarial growth, the luxury of waiting 6 months is very rarely, if ever, possible. Typically the surgery will have to be scheduled within the first 6 weeks to prevent damage to the developing brain. The longer the surgical team can wait the safer the surgery will be. The decision to operate is a joint one among the pediatricians (including neonatalogists and intensive care personnel) plus the anesthesiologists, family, and craniofacial team. The potential risks to the very young child are the significant blood loss (almost all of these children will require blood transfusions), and
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the surgical team is operating on a child with fetal hemoglobin, and in many cases other associated congenital anomalies. Ideally, in children with pansynostosis, the preoperative evaluation includes a thorough evaluation for any cardiac, renal, or other associated systemic anomalies, which are not at all uncommon. Absolutely essential is a full radiographic workup including standard computed tomography (CT) and magnetic resonance imaging (MRI) scans. Congenital anomalies such as holoprosencephaly, underlying maldevelopmental problems of the brain, should all be worked out prior to surgery. In many cases we ask our bio-ethics team to be involved to make sure the child is a reasonable candidate for surgery and to make the family aware of future developmental problems. Included in the radiological studies should be an evaluation of the ventricular system, as a high percentage of these children do develop hydrocephalus because of associated severe cranial-based anomalies. Because of unusual positioning problems in these children (i.e., it is not uncommon to have the child in hyperextension) the skull base and cervical medullary junction need full evaluation. Chiari malformations, narrow or distorted foramen magnum, etc., are all seen in this population. To prevent a child from awakening from surgery as a quadriplegic, it is important to sort out these details first. If, for example, a Chiari malformation is detected, then the surgeon will appropriately modify the positioning to avoid hyperextension or undue stress on the cervical region. The use of prophylactic anticonvulsant drugs (ACDs) preoperatively remains controversial; on our service we do not routinely place a child on anticonvulsants unless there has been a seizure history. If ACDs are used, then the appropriate loading dose should be given at least 24 hours in advance of the surgery and continued for 30 days after surgery. Because these children typically have severe skullbase anomalies, we complete a full endocrine workup to rule out any hypothalamic-pituitary dysfunction. A routine coagulation profile is done prior to surgery. As mentioned earlier, a full and complete medical workup is done to rule out any cardiac, liver, or renal dysfunction. If any are detected, then the surgical management plan includes the appropriate treatment of these medical problems. It cannot be overemphasized how thorough this preoperative workup should be—it is not at all unusual to find one or more other system abnormalities in the preoperative workup.
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Surgical Management of Pansynostosis (Craniosynostosis)
Anesthetic and Monitoring Surgical correction of a pansynostosis is a long and technically complex procedure. Our anesthesia team manages these children as if they all have increased ICP so that inhalation agents that increase ICP are avoided. Use of paralytic agents is encouraged to prevent any movement during the case and also to assist in reducing ICP. We no longer use dehydration agents (mannitol 0.5. g per kg) prior to induction; the exception is if the brain looks tight at the opening. A Foley catheter is placed to monitor urine output. A temperature probe is placed either in the esophagus or rectally to monitor body temperature. Heating blankets (e.g., Bair Hugger blanket; Arizant Healthcare, Eden Prairie, MN) are placed both below and on top of the patient to maintain an euthermic body temperature. There is almost always a significant blood loss associated with these cases; therefore, at least two large-bore intravenous lines need to be placed. If vascular access is difficult, then a subclavian or jugular line can be placed. Arterial monitoring is essential to allow for evaluation of blood pressure, serial electrolytes, and blood gases. The child is typically kept in hypotensive range with a mean arterial pressure of 40 to 50 mmHg to help reduce blood loss. We now routinely use oxygen saturation monitors, which can be placed on the child’s finger or toe. We position the child in mild hyperextension. We also try to place the head level with the heart to help reduce air embolism; fortunately air embolism is rare in these types of cases. With meticulous skin incisions and careful coagulation of all bleeding sites, plus careful waxing of the small emissary veins that travel through the skull bone, the risk of air embolism can be markedly reduced. It has been our experience that these children, because of increased ICP, often have dilated venous patterns over the scalp and, in addition, large diploic veins. These can be treacherous sources of blood loss plus sources of venous air embolism and must be carefully waxed or coagulated. Perioperative antibiotics are used; typically only the skin organisms are covered, for example, Staphylococcus and Streptococcus. The drug of choice is oxacillin (or vancomycin if the child is allergic). If the child has another source of infection such as a otitis media or upper respiratory infection, these are treated preoperatively and cleared prior to the start of any surgery.
Operative Procedure Positioning The typical child with pansynostosis requires almost the entire calvaria remodeled and repositioned (Fig. 9–1—9–6). As a result the entire calvaria must be exposed in the operative field. This surgical field includes from the level of the orbits to the level of the inion and sometimes the foramen magnum. To do this we place the child in the prone position with the head extended (after radiological evaluation has shown no abnormalities of the cervical medullary junction). The chin rests on a horseshoe that is well padded (Figs. 9–1A,
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9–1B, and 9–4A). The draping is done with a split sheet, keeping the orbits and entire calvaria in the operative field. Bilateral tarsorrhaphies are done at the beginning the case to protect the eyes. We no longer do a full head shave, rather we either part the hair or trim the hair for ~2 cm where the skin incision is to be made. Fig. 9–7 shows the operating room layout. The operating table is usually reversed head to foot so that the surgeons have more room to place their legs comfortably under the table. The operator works at the end of the table with the assistant to the side. The nurse with the instrumentation is placed to the right of the assistant. A Mayo stand is placed over the table and on this the nurse places the instruments directly in use. Behind the nurse is a larger table that holds the main instrument groups. A Mayo stand is placed to the left of the operating surgeon and directly to side of the child’s head. When the drapes are in place, this then allows the anesthesiologist an access tunnel to the child’s airway and to the child’s peripheral lines. All the suction tubes, cautery lines, etc., are run off the opposite end of the table. This allows the surgeon and assistant to sit and not to have their chairs run over the various tubes and cables that can be present. The only item at the foot of the surgeon should be the cautery pedals and the pedals to run the air drills when necessary. An additional point to consider in the draping is the use of waterproof drapes. As these cases require considerable bone removal, the saline irrigation used can be copious. It is important that the drapes in contact with the body not get wet during the case. In addition we place heating blankets both below and on top of the child. Because these are small children the heat loss can be considerable and rapid, so hypothermia has to be carefully monitored and avoided.
Skin Incision These cases require a large and wide exposure of the calvaria. The simplest and most cosmetically efficient incision is the bicoronal incision done in a zig-zag fashion. This incision is started behind one ear and carried over to the opposite ear and normally follows a midpoint between the nasion and inion. This incision will easily allow the operator to expose from the level of the orbit and nasion over the convexity and to below the nuchal line. By this approach the entire calvaria can be visualized. During the skin incision the surgeon must be careful not to cut into the temporalis muscle fascia. The pericranium is elevated as a separate layer, and where it merges with the temporalis fascia it is incised. The temporalis muscle is then elevated as a separate layer and is hinged to its base. By doing this the temporalis is available to be laid down at the end of the case intact and sewn back to the pericranial layer. If the exposure is carried down to the foramen magnum, then the nuchal muscles can be elevated as a flap in continuity with the periosteal layer. This technique allows the nuchal muscles to be laid down at the end of the case when the periosteum is laid back. When elevating the frontal periosteal membrane the supraorbital nerve and artery complex can be easily elevated with the periosteum. This will allow preservation of this important nerve and
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A
B
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D Figure 9–1 (A) Operative positioning, lateral view. The child is placed prone in a mild hyperextended position. The child is face down resting on a well-padded horseshoe headrest. The electrocautery grounding pad is placed on the child’s back. (B) A frontal intraoperative view of a child with severe pansynostosis and a severe “cloverleaf” deformity of the skull. This child was diagnosed at birth and by 3 weeks of age had stopped all head growth. It is important to appreciate the number of deformities in the skull. Because of fusion of the coronal and squamosal sutures there is a severe dimpling in the temporal region. Over the calvaria several spots could be palpated secondary to brain “escaping” through the skull. The lambdoid sutures were so tightly fused the child did not develop the usual inion point. The head assumed the typi10.1055/978-1-60406-039-3c009_f001
cal early cloverleaf appearance that occurs when all the sutures fuse. (C) An intraoperative view of the forehead corresponds with the view in Fig. 3A after the skin flaps and pericranium have been elevated. Methylene blue has been used to mark out the osteotomy sites. The orbital bandeau will be harvested from just behind the coronal suture. The new forehead will come from the child’s left temporoparietal region (see Fig. 9–3A). (D) An axial computed tomography scan of this child showing the severe “thumbprinting” and bone invagination into the brain—all concepts that must be kept in mind when elevating the bone flaps. Getting these invaginated bones out of the brain can be extremely tedious and difficult.
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artery that run in the supraorbital notch. Occasionally the notch will need to be opened, especially in older children. The notch can be opened with either a small osteotome or a 2 mm Kerrison punch.
Operative Technique To illustrate the operative technique used in this type of craniofacial reconstruction we have selected two cases, each done with a different surgical technique. We have selected these two cases to illustrate various surgical procedures available to the craniofacial team.
Case One History: A 6-week-old child who presented with severe pansynostosis involving all the sutures resulting in increased ICP and severe “thumbprinting” appearance of the skull. Craniofacial reconstruction is going to require complete disassembly of the calvaria from orbit to posterior fossa (illustrated in Figs. 9–1—9–3). The patient is positioned in the supine position with head extended as shown in Fig. 9–1A and Fig. 9–1B. After the bicoronal incision is made and the periosteum is elevated, the entire calvaria is exposed in the field. As this child’s forehead and orbital rims are going to be advanced, a new bandeau and forehead unit needs to be marked out. Fig. 9–1C shows the intraoperative view after methylene blue is used to mark the plates to be harvested. The bandeau will come from an area just anterior to the coronal suture. The only area where a normal forehead unit could be located was over the left temporal parietal region. The rest of the osteotomies are designed to provide large pieces of bone for the reconstruction after the bandeau and forehead have been advanced. As this child has severe skull molding and thumbprinting of the inner table, the bone elevation has to be done with great care to avoid tearing the dura or entering a venous sinus (see Fig. 9–2). Using a high-speed footed drill and “walking” the footplate along the grooves and digital markings, these units can be elevated safely. Areas that are particularly treacherous are over the sinuses and between the orbits. On the CT the surgical team noted this child has a tongue of brain coming in deep between the orbits. Appreciating this anatomy early prevents an unacceptable situation of tissue damage to the frontal lobes. In many cases the sphenoid wings can be severely sclerosed (giving the “harlequin eyes”), and in these cases the excessive sphenoid ridges are removed bilaterally. Once the bone plates have been elevated, they are taken off the field to another sterile table where the surgeons can reconstruct the calvaria in the fashion best suited to give an advancement, keeping in mind the amount of bone available. In Figs. 9–2B and 9–2C we have reconstructed the new calvaria using the forehead unit and new orbital bandeau. To give an adequate advancement one can appreciate the “lack” of bone that occurs when the reconstruction is done. Important points to remember are a good forehead and bandeau unit first. Bone has to be placed over the calvaria along the sagittal sinus to prevent a later turricephaly that can occur. We have found that if the convexity/vertex is left open, the
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brain will go the path of least resistance and as a result turricephaly can occur. With proper attention placed to strut placement the brain (i.e., frontal lobes) will expand forward and not upward. These struts are placed along the convexity to help orient the direction of growth. The other pieces of bone are then placed in a mosaic fashion to cover as much of the brain as possible. In this particular child there was such a severe constriction of the head that after the calvaria was remodeled with the available bone, we realized only 60 to 70% of the brain was covered with bone. In young children, particularly under 1 year of age, reossification will occur easily and quickly. In some cases the bone harvested can be additionally split with fine sharp osteotomes. In children with severe pouching of the dura caused by thumbprinting there can occur dural tears. These tears must be attended to and sutured so that no cerebrospinal fluid (CSF) leaks occur. CSF leaks can be very troublesome days later with subgaleal collections so it is important to repair any CSF leaks or dural tears done in the opening. Fig. 9–2C shows the calvarial unit after placement. Absorbable sutures (e.g., 3–0 Vicryl) are used for stabilization and holding in position the forehead units. In cases where extra stabilization is needed, absorbable miniplates can be used. We no longer use any wire or metal miniplates because of unacceptable migration of these materials as the child grows. In several cases, at a later reoperation, we found these metallic materials had literally migrated through dura, and in a couple of cases they had actually come to rest within the brain.
Case Two History: An 8-month-old child was noted to have severe pansynostosis with lack of head growth from 4 months of age. After careful workup for microcephaly, which was ruled out, the craniofacial team determined the child had severe synostosis of all the calvarial sutures. However, in this child the orbital units and forehead were not severely affected, so the reconstruction was based on the units behind the coronal sutures. The positioning techniques and preliminary steps were the same as in case one. The significance of this child’s synostosis can be appreciated in Fig. 9–4, which shows the anteroposterior and superior views of the child. In this child all the calvarial sutures were either closed or severely sclerosed on x-ray. However, the aesthetic examination showed the orbits and forehead to be symmetrical. On the basis of this, rather than do a complete calvariectomy, we kept the forehead and orbital unit intact and reconstructed the calvaria and occipital region. In Figs. 9–4C and 9–4D the child’s head is shown from a lateral and superior view so as to see the methylene blue markings and where the osteotomies will be done (Fig. 9–6 shows a schematic reconstruction). To correct the deformity over the occipital region and to allow growth and advancement, a new bandeau is harvested from over the occipital calvaria. This will act as the base unit for reconstruction. To anchor this bandeau down, a “step-off” has been marked out over the asterion region (Fig. 9–4D). The entire occipital region and posterior fossa will be removed in two units, and these pieces will be used in the
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D Figure 9–2 (A) The unit of bone that came from the area labeled “B” in Figure 9–3B. The view is of the underside of the bone, that is, the inner table. One can appreciate the severe “thumbprinting” that can occur in these cases. The dura is pushing through these areas, and in addition there are points where the bone has been completely eroded through the dura and brain has been exposed. The elevation of this bone has to be done very gently and carefully to avoid injury to the sinuses and to the brain. See Fig. 9–1D for the CT view. (B) Once the various bone units are harvested, they are taken to a separate table and positioned 10.1055/978-1-60406-039-3c009_f002
to see how they will fit on the child. It is easy to appreciate from the photograph that severe pocketing and erosion of the bone has occurred. With the advancement necessary to decompress the brain, there is insufficient bone available to cover the calvaria. Two important pieces of bone are those struts that will be placed over the convexity to prevent a turricephaly from occurring. (C) An intraoperative forehead view of the child prior to closure. This view is an equivalent view of Fig. 9–3B. (D) The child at 10 months of age.
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A
B 10.1055/978-1-60406-039-3c009_f003 Figure 9–3 (A) An artistic reconstruction of the Figure 9–1C showing the various sites for osteotomies and harvesting. The bandeau is elevated from just behind the coronal suture. The new forehead unit (labeled “A”) is marked out with a Marchac template and elevated from the temporal-parietal region. (B) An artistic reconstruction of Figure 9–2 only here showing the various osteotomies on the left and their
repositioning on the right. The areas marked out as A and B will form the new forehead and posterior occipital unit. The bandeau is harvested and advanced forward and positioned in the right figure. A sagittal strip of bone is placed in the hopes of preventing a turricephaly from developing. The blank areas are exposed dura mater, which is common due to lack of bone that develops in the various advancements.
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B
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D Figure 9–4 (A) An intraoperative view of an 8-month-old child with severe synostosis of all the calvarial sutures. The dimpling about the temporal region and the flattening and distortion over the parietooccipital region can be appreciated. In this child the frontal unit and orbital bandeau are symmetrical and not distorted. The surgical team decided on a reconstruction behind the coronal suture rather than a total calvarial remodeling. (B) An intraoperative view similar to (A) with more of an oblique angle of the child's head showing the severe distortion of the calvaria that has occurred over the posterior parietal and occipital regions. (C) A vertex view similar to (A) after reflection of the skin and 10.1055/978-1-60406-039-3c009_f004
periosteal flaps, with the various osteotomies marked out in methylene blue. The orbital bandeau will be taken from just behind the coronal suture, which can be seen in this view. The area over the child's left occipitoparietal area was determined to have the best configuration to reconstruct a new occipital plate. (D) A lateral view after reflection of the skin and periosteal flaps. Using methylene blue the osteostomies have been marked out. The bandeau will come from just behind the coronal suture. This unit will be moved back and placed tongue-in-groove into the asterion step-off unit, which has also been marked out.
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reconstruction. The piece over the right occipital region (labeled “A” in Fig. 9–6A) was determined to have the closest symmetry to a new occipital plate, and this was marked out using a Marchac template (Walter Lorenz, Surgical, Jacksonville, Florida; see Figs. 9–5A and 9–6B). As the sagittal sinus lies under the sagittal suture, it is sometime useful to make an additional osteotomy lateral to each side of the suture. Then the plate of bone over the sagittal sinus is elevated last, allowing better control in case of any sagittal sinus bleeding. In some children the bone can be tightly attached at the suture lines so additional care must be taken in elevating the bone at these points. Once the bone has been harvested the bandeau is placed into position, tongue-in-grooved to the asterion unit. On this bandeau the new occipital unit, which had been previously fashioned, is placed. This acts as the framework upon which to build the rest of the calvaria in a mosaic fashion. In Fig. 9–5A we show the various bone units “gull-winged” out to show the location and position prior to suturing into position. In the older child, with firmer bone, it is occasionally useful to place radial cuts in the bone to allow the expanding brain to spread out (this can be seen in Fig. 9–5D). Fig. 9–5C is a superior view showing the bandeau in position; the new occipital unit has been placed and around this framework the calvaria is reconstructed in a mosaic fashion using the remaining bone (Figs. 9–5 and 9–6). As in case one, it is important to remember to cover the sagittal sinus first with bone, to act as a strut, and subsequently to prevent a turricephalic growth pattern from developing. Absorbable miniplates are again used in those parts that need the additional support. Absorbable suture material is used primarily to stabilize the various bone units. Where extra stabilization is needed we use absorbable miniplates.
Closure Technique After the calvarial bone units have been placed, the closure is done in a reverse fashion of the opening. The surface is then copiously irrigated with warm physiological saline solution. As these are long cases, with long exposure times, copious irrigation is essential to remove any debris and bacterial contaminants. The pericranium is elevated and carefully stretched out over the calvaria. The nuchal muscles should come up easily with the posterior pericranial layer. The frontal layer is then brought up and retention sutures are then placed between the front and back layers. These layers will not meet due to shrinkage and the advancement; however, they can be kept in position by retention sutures. Next the temporalis muscles have to be reattached to the pericranium, or sometimes they can be sewn to the sutures in the bone units. In any case the reattachment of the muscles is key for both aesthetics and muscle function. In the past we would place a drain in the subgaleal space, which we now no longer do. The reason we stopped this practice is that the drains seemed to increase the blood loss and increase the rate of infection. Rather than drains we pay very close attention to hemostasis prior to closure of the skin. Remembering that the reconstruction is a very fragile unit, a soft “fluffy” dressing is placed over the wound. We do not use any tight wraps or constricting type of dressing
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as this can lead to collapse of the reconstruction. A snug Kling type of dressing is normally adequate for holding the dressings in place.
Specialized Instrumentation These operations are done with a standard craniotomy set. It is recommended that a high-speed drill system with craniotome (e.g., Midas Rex; Medtronic Inc., Fort Worth, Texas) be used for harvesting the calvarial bone. These children typically have thinned skulls with severe inner table erosion, and so to prevent injury to the brain and dura the operator will need a well-controlled high-speed drill system with a fine foot plate to separate bone and dura. To mark out the forehead unit we have been using the Marchac forehead templates. These templates are quite useful in locating a unit of bone on the calvaria that most closely approximates the normal forehead.
Postoperative Management Including Possible Complications There are several known complications associated with these complex craniofacial procedures. It has been our experience that if the surgical team members think of them as they go through the preoperative, intraoperative, and postoperative preparations, in most cases they can be avoided.
Hemorrhage Blood loss occurs as a normal part of any operation. Because of the extensive nature of the craniectomies, amount of flap exposure, and osteotomies the potential loss of blood can be significant. To help reduce blood loss several procedures can be done. We routinely ask the family to arrange for pedigree blood to be given. Donor-directed reduces the risk of various infectious agents that can be carried in blood. The anesthesiology team keeps the child in the hypotensive (mean arterial pressure of 50 mmHg) range during the procedure. Blood transfusion is done only when the hematocrit drops below 25 or the child becomes clinically symptomatic. We routinely plan on transfusing at least 1 unit of blood and in ~20% of the cases a second unit will be needed. It goes without saying that attention to meticulous technique can help reduce the loss of blood. Use of epinephrine infiltration during the skin incision, skin clips, careful use of cautery, etc., all can help reduce blood loss.
Infection For any craniofacial procedure the child is preoperatively started on antibiotics for skin organisms (usually oxacillin) and treatment is continued for 24 hours postoperative. The rate of infection is fortunately quite low in these cases. Due to the length of these procedures and the debris that accumulates, it cannot be overemphasized how important it is to copiously irrigate at the completion of each case to remove the collected debris. These patients typically develop fevers
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Figure 9–5 (A) An intraoperative view (equivalent to Figs. 9–4A and 9–4B) after the various units have been repositioned. The new bandeau has been attached to the asterion, and the various bone units have been mounted on the bandeau unit. In this view the surgeon has laid the bone out to show where each of the units is being placed. (B) An intraoperative view equivalent to (A) with the bone laid into position and just prior to stablization. (C) An intraoperative view equivalent to (A) and (B) with the bone units sutured into position. (D) A posterior view (i.e., looking at the occipital region) showing the “radial cuts” made in the occipital unit to help mold and better position the bone. In the older child the bone is not as malleable, and this is a useful technique to help the brain remodel the bone as it grows. (E) An intraoperative view at the completion of the operation, equivalent to Figs. 9–4A—9–4C. The immediate correction that occurs with this type of technique can be appreciated here.
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Figure 9–6 (A) An artist reconstruction of Fig. 9–4A showing the various osteotomies. (B) An artist's reconstruction of Fig. 9–4D, only from the child’s right side showing the various units in their new position. The asterion step-off can be seen here, and this is where the bandeau will be anchored. (C) An artist’s reconstruction of Fig. 9–4D (opposite side view) showing the harvesting and direction of the new bandeau unit. This unit acts as the framework upon which the rest of the calvarial reconstruction will take place. (D) An artist’s reconstruction of Fig. 9–5C, from the child’s right side, showing the various units in their new positions. (E) An artist’s reconstruction of Figure 9–5C showing the bone units wired into position. The units have been labeled and are equivalent to the schematic in (A). The donor sites and their eventual location can be appreciated better here in this schematic.
10.1055/978-1-60406-039-3c009_f007 Figure 9–7 Operating room schematic. The surgeon typically sits at the head of the child with the assistant to the right. The nurse is positioned to the right of the assistant. A Mayo stand is brought over the child at the buttock level. Another Mayo stand is placed to the left of the child and parallel with the child. This provides a tunnel for the anesthesiologist to view the child and the respiratory apparatus. The anesthesia machinery is placed behind the anesthesiologist. A large table is placed behind the nurse where most of the instruments are placed. The Mayo stand is used only for the immediate instrumentation.
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in the first week postoperative. Routine fever workups are done, but rarely is a source found. We attribute these fevers to the resorption of blood that occurs from under the skin flap. In the case of an extensive advancement it is not uncommon to leave a large “dead space.” These spaces have the highest incidence of infection and if a child develops evidence of sepsis, these spaces many need to be tapped for a bacteriology culture. The incidence of this happening is fortunately low but always must be considered in the differential.
Patient Positioning Because of the need to place the child in hyperextension, it is important to get preoperative CTs or MRIs to rule out any abnormalities of the cervical medullary junction, a not uncommon finding in this patient population. Before a child is hyperextended the surgeon must rule out any evidence of a Chiari malformation, bony anomalies, or narrowing of the foramen magnum. If any of these are noted, the positioning has to be corrected to allow for it.
Cerebrospinal Leaks All CSF leaks should be identified and repaired prior to closure. A helpful technique in locating potential CSF leaks is to have the anesthesiologist provide a sustained positive pressure Valsalva maneuver prior to closure. CSF leaks can lead to large subgaleal collections and an increased risk of infection.
Use of Wire and Metal Fixation Miniplates Early on we used wire to stabilize the bone units. Due to unacceptable wire erosion through the skin, we have given up the use of this material and have replaced it with absorbable sutures and “absorbable” miniplates. Over the years we have
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found the metal miniplates to also migrate in unacceptable patterns in the growing child. As a result we no longer use metal fixation plates in a child under the age of 3. However, the use of absorbable miniplates has proven to be helpful in those areas where extra stabilization is needed.
Hydrocephalus There is a significant incidence of hydrocephalus reported in children with multiple suture closures. There are also differing views as to when to treat the hydrocephalus, that is, before or after the craniofacial reconstruction. It has been our policy to do the craniofacial procedure first and shunt second. We have found that in some cases the treatment of the pansynostosis alleviates the need to treat hydrocephalus (as was the situation in the first case). Plus the early correction of hydrocephalus can cause a dramatic collapse of the brain, which will work against the reconstruction. On the other hand, if the child is very sick from increased ICP, the shunt is placed to relieve ICP. Another factor to consider in a secondary placement of the shunt is the increased risk of infection due to the shunt being present during a lengthy reconstruction. Acknowledgment This chapter is a revision of the chapter, “Pansynostosis: Surgical Management of Multiple Premature Suture Closure” by James T. Goodrich, M.D., and Craig D. Hall, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 2, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Craig Hall, M.D., for his help and efforts on the original chapter published in the first edition of this work.
10 Tethered Spinal Cord, Intramedullary Spinal Lipomas, and Lipomyelomeningoceles Elizabeth C. Tyler-Kabara and W. Jerry Oakes Progressive dysfunction of the spinal cord may be caused by fixation or by compression from a neoplasm. This chapter focuses on three congenital entities that cause symptoms by different mechanisms. The patient with a tethered spinal cord develops symptoms from tension by a thickened and taut filum terminale on the distal spinal cord. Intramedullary spinal lipomas distort and compress the surrounding cord but do not have a component of fixation that causes the neurological deterioration. The lipomyelomeningocele has components of both cord fixation and compression, which is thought to be the underlying explanation of the progressive loss of neurological function associated with this lesion. Because the surgical approaches to these lesions are quite different they will be discussed separately.
Tethered Spinal Cord The concept that fixation of the distal spinal cord by a thickened filum terminale can cause progressive spinal cord dysfunction has become accepted during the past 50 years. Surgical procedures to section the filum have only become common in the past 30 years. The dysfunction of the spinal cord occurs from a combination of repeated small injuries or contusions as the cord is put under tension with movement (especially spinal flexion) and by apparent vascular compromise. The change in the superficial vasculature of the cord as well as its disturbed ability to metabolize oxygen has been demonstrated both in laboratory animals and in humans. The vascular changes that occur with tension of the cord seem to improve following release of the tension.
Patient Selection Patients may present for clinical attention with a variety of complaints. One group of patients will present for clinical attention only as a result of cutaneous evidence of occult spinal dysraphism. This may take many forms including a flat capillary hemangioma or a small dermal appendage. When one of these cutaneous findings is present, it suggests further investigation. The majority of patients with a flat capillary hemangioma will have normal intradural anatomy; however, a significant minority (as high as 10%) will have a tethered spinal cord. Waiting for the patient to demonstrate the clinical findings of a neurogenic bladder is
likely to result in a fixed neurogenic deficit that may not be reversible with surgical intervention. Prevention of further bladder dysfunction by early investigation and prophylactic surgery is warranted. Commonly, the initial clinical symptom in patients with tethered cord syndrome is the gradual and progressive loss of coordinated bladder activity. This may become manifest as repeated bouts of urinary infection or primary or secondary urinary incontinence. The urinary symptoms may be combined with evidence of spasticity of the lower extremities. The lower extremity involvement is frequently a combination of hyperactive deep tendon reflexes with upgoing toes and muscle wasting, fasciculations, and shortened foot or leg length. The combination of upper and lower motor neuron disturbances in the lower extremities is the signature of this problem. Even though the tension could be thought to be relatively symmetric on the distal cord, the leg findings are typically asymmetrical. Rectal incontinence is usually delayed until late in the course. Nonradicular pain in the back and legs may be the primary cause of presentation in the adult population. Occasional precipitous deterioration has been recognized. Sudden lower spinal flexion as in patients assuming the lithotomy position under anesthesia has resulted in dramatic worsening and even abrupt onset of paraplegia in occasional patients. In at least 10 to 20% of patients with congenital anorectal atresia, a tethered spinal cord will also be found. This group of patients clearly warrants early investigation in an effort to prevent the development of a neurogenic bladder and to improve the neurological input into the dysmorphic rectal sphincter. Many patients with a thickened filum terminale are seen to have some other form of neural tube abnormality. This may range from an obvious myelomeningocele to the combination of intact normal skin and an occult split cord anomaly or terminal syringohydromyelia. The suspicion of a tethered spinal cord is confirmed with magnetic resonance imaging (MRI). The use of computed tomography (CT) myelography in this patient population has been almost entirely replaced by MRI. In general, three criteria are necessary to radiographically confirm the clinical impression of a tethered spinal cord: caudal descent of the conus, fatty infiltration and thickening of the filum terminale, and a drawn-out or “funnel-like” appearance of the distal conus. Normally the conus should not descend below the L1-2 disk space. The conus progressively ascends within the
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spine throughout embryological development and early infancy. It normally attains its “adult” position by 3 to 6 months of age and maintains this position throughout adult life. In patients with tethered cord syndrome, the thin delicate structure of the normal filum terminale is lost. It becomes thickened (usually more than 3 mm in diameter) and is typically infiltrated by fat, which is easily appreciated by MRI on the axial T1 sequences. This thickening results in tension on the conus and a loss of the normal bulbar lumbar enlargement of the distal cord. The cord assumes a funnel-like appearance, dorsally displaced within the subarachnoid space and under tension. When all radiographic findings occur in a patient with an appropriate clinical setting, the diagnosis is secure. Unfortunately, there are occasions when patients present with progressive clinical symptoms that could easily be attributable to a tethered cord, but the radiographic findings are confusing. The conus may be in a normal position but the filum may be thick, infiltrated by fat, and dorsally displaced under tension. As with many clinical situations, judgment in analyzing the clinical and radiographic findings is essential to arrive at an appropriate decision for the patient. The natural history of the condition is not well understood. Many believe that the constant small trauma associated with tension on the distal cord by the thickened filum is associated with the relentless loss of neurological function in most patients. This loss may occur within the first few months of life or more typically over a much longer time. Occasional adult patients will demonstrate many decades of symptom-free survival only to come to clinical attention with irreversible bladder dysfunction. Pain-free adolescents and adults with normal neurological function but clear radiographic abnormalities attest to the incomplete ability of the clinician to predict the natural history of this condition. Patients with progressive symptoms and classic MRI changes are easily counseled to accept operation in an attempt to prevent further loss of function. Asymptomatic patients can be approached with a risk-versus-benefit analysis depending on the strength of the radiographic abnormalities and other evidence of dysmorphism, that is, anorectal atresia, hemivertebrae, etc.
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Once a decision to operate has been offered and accepted, the patient is positioned prone with bolsters placed under the iliac crest and thorax to allow free excursion of the abdomen (Fig. 10–1A). Some surgeons feel more comfortable utilizing intraoperative monitoring of rectal and/or urethral electromyography. Ultra-short-acting muscle paralysis is necessary to allow appropriate interpretation of these electrical parameters.
space to allow adequate visualization of the distal filum terminale. The dura is opened in the midline and the arachnoid is opened somewhat off the midline. The thickened filum can be recognized by the infiltration of fat within it, by its midline dorsal position, and by the size differential between this structure and the surrounding thin delicate roots that exit in a ventrolateral direction. Additionally, the filum has a characteristic vessel on its ventral surface that may be appreciated by rotating the filum. Once the filum is identified it is carefully separated from all adherent nerve roots, particularly those on the ventral surface (Fig. 10–2A). One must rotate the filum to visualize the undersurface and to ensure that no small roots are left adherent to the capsule of the filum. When this is confirmed the filum is coagulated and cut (Fig. 10–2B). This is done at two levels to allow the excision of a section of 5 to 8 mm that can be sent for histological analysis and to ensure that the two ends of the filum will not adhere to one another. Care is taken to ensure a watertight closure of the dura and the superficial soft tissues.
Operative Procedure
Postoperative Management
An incision is made from the spinous process of the tip of the L5 vertebra to the mid sacrum (Fig. 10–1B). The dorsal bony elements of S1 are removed by standard laminectomy technique, and the sacral dura is exposed. There is rarely need to expose more than 2 to 3 cm of the subarachnoid
Patients are routinely nursed flat for several days to allow adequate dural healing without the additional tension of orthostatic force of the cerebrospinal fluid (CSF). The likelihood of adherence of the cut ends of the filum is extremely small. Long-term complications are very rarely seen.
Preoperative Preparation
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64 Pediatric Neurosurgery congenital lesions that may lay dormant for many years or decades. They are not associated with spina bifida occulta and are relatively evenly distributed in the cord. There is a predilection for involvement of the dorsal aspect of the cord, but the fat is not connected with a defect of the arachnoid, dura, laminae, or skin. When symptomatic, these lesions are approached as any other intramedullary tumor with a laminectomy over the involved area.
Operative Procedure Using an ultrasonic aspirator or a CO2 laser at very low wattage, the fat can be removed and the fibrous septa between the various compartments of fat can be disrupted. The cord may be reconstructed into a tube following the resection of the fat and the redundant dura is closed primarily and tented dorsally in an effort to prevent adhesion from the resection site to the undersurface of the dura. The outlook for these patients is a function of the degree of neurological disability prior to surgery and the success of the resection. The goal of the operation is not to remove every pocket of fat but rather to debulk significant mass effect leaving the interface between the spinal cord and the lipoma unmanipulated.
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Results with regard to blunting of the previous rate of loss of neurological function are quite favorable. The ability to restore lost function, particularly bladder synergy, is poor. Relief of pain and sensory loss is gratifying. Progressive moderate scoliosis may be arrested. Restoration of motor function is less likely than sensory improvement or the relief of pain. Urologic dysfunction, which is the most common cause of clinical presentation, remains the least likely to improve once it is firmly established.
Intramedullary Spinal Lipoma Patient Selection Intramedullary fat that accumulates under the pia of the spinal cord may cause the patient to present for clinical attention with chronic myelopathy or pain. These are rare
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Subcutaneous fatty tumors over the midline lumbosacral region usually emerge through a fascial, bony, or dural defect and ultimately involve the caudal spinal cord. These lesions are best described by where they grow into the cord (dorsal or caudal). Lipomyelomeningoceles are part of the larger group of conditions termed occult spinal dysraphism and may be found in conjunction with a split spinal cord, tethered spinal cord, or other forms of this broader group. They do seem to have an enhanced genetic predisposition and may be associated with a Chiari I malformation or occasionally hydrocephalus. The special circumstance of a fatty mass associated with a terminal syringohydromyelia will be discussed later.
Patient Selection Symptoms related to these lesions range from a cosmetic presentation at birth with a significant subcutaneous fatty mass in the midline over the lumbosacral region to a subtle subcutaneous lipoma associated with primary or secondary urinary incontinence. It is unusual today to have children present primarily with evidence of pain or motor disturbance involving the lower extremities. In large part this is due to an increased awareness of the progressive natural history of this lesion and the ease of confirmation of spinal cord involvement by MRI. Decreased or absent rectal tone combined with a neurogenic bladder is a clinical indication of lower sacral root involvement from a neurogenic cause and should be investigated further. Today the procedures of choice to confirm the pathological anatomy are MRI and radiographs of the lumbar spine. These two modalities have almost totally replaced CT my-
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elography. Additionally, useful information can be obtained from urodynamic testing and occasionally from electromyography of the lower extremities. The natural history of patients with a lipomyelomeningocele is a progressive loss of neurological function. Occasional exceptions to this natural history can be demonstrated, but the vast majority of infants followed prospectively without operative treatment will develop progressive and relentless deterioration. Some forms of lipomyelomeningoceles can more clearly be positively influenced by surgery than others. These would include simple dorsal tubes of fat having a discrete point of fixation with the spinal cord. Lesions associated with a blending of the neural elements with the lateral aspect of the dural cul-de-sac benefit less certainly from operative intervention. Although most North American pediatric neurosurgeons continue to favor early intervention for all infants, other well-respected pediatric neurosurgeons have questioned this approach and may wait for the individual patient to demonstrate clear loss of neurological function before recommending intervention. Surgical exploration should include release of the traction on the cord and resection of a significant amount of the intramedullary lipoma. Reversal of bladder dysfunction is unlikely once it is established. For this reason alone, early aggressive surgery is logical and justified if felt to be feasible. It should be mentioned that there is no place for a superficial excision of the subcutaneous lipoma without disturbing the intradural contents. A superficial excision seriously complicates
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the eventual intradural procedure by the development of significant intradural adhesions.
Preoperative Preparation A patient chosen for exploration of the lesion is positioned prone with soft supports under the iliac crest and chest to allow free excursion of the abdomen. This significantly lessens epidural bleeding. The hips are flexed and, again, intraoperative rectal and urethral monitoring may be utilized.
Operative Procedure The skin incision is made in the midline directly over the subcutaneous mass and extends both above and below the mass (Fig. 10–3A). A common error is not to allow sufficient distal room for adequate exposure of the lesion. For routine lesions it is necessary to have access from the lower sacrum to two segments above the level of the fascial defect. The subcutaneous lipoma is almost always easily separable from the lumbodorsal fascia and the skin. As the neck of the lesion is circumferentially developed, large amounts of superficial lipoma may be excised, reducing the bulk of the lesion. The neck of fat coursing through the fascial defect is retained at this point (Fig. 10–3B). The soft tissues and muscle adherent to the last intact spinous process and laminae are reflected laterally (Fig. 10–3C). The muscles and
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Figure 10–3 (A) A typical skin incision over the dome of a lipomyelomeningocele. (B) The subcutaneous aspects of the lipoma dissected, the neck of the lesion coursing through the fascial defect is fully developed. Excessive lipoma can be removed safely to allow additional exposure (dashed lines). (C) After excessive circumferential fat is removed, the paraspinal muscles are then dissected off the last intact lamina. The constricting periosteal band immediately cephalad to the neck of the lipoma can then be sectioned.
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66 Pediatric Neurosurgery other soft tissues circumferentially adherent to the rudimentary laminae surrounding the neck of the lesion are also dissected. Immediately caudal to the last intact laminae a band of fibrous tissue corresponding to the periosteum of an incompletely formed bony element will commonly be encountered. With sectioning of this band the dura may expand significantly into the area. This band may be associated with acute angulation of the malformed cord as it is drawn dorsally toward the subcutaneous lipoma. Sectioning this band may significantly relieve the tension on the cord and reduce its posterior angulation (Fig. 10–3C). With adequate exposure of the dural tube cephalad to the lipoma, it is opened in the midline. Asymmetrical exiting roots can then be seen. The junction of the dura to the neck of the lipoma as it emerges through the dural defect is a key landmark for further dissection. Special care must be given at this point to appreciate the relationship of the dorsal roots that have been displaced laterally by the lipoma and the dura-lipoma complex (Fig. 10–4A). Obviously, no roots should be sacrificed, and yet the dura needs to be circumferentially dissected away from the dorsally displaced cord (Fig. 10–4B). The asymmetrical arrangement of exiting roots combined with rotation of the cord may further complicate this maneuver. Once this critical maneuver is complete and the cord has been moved into a relaxed ventral position within the dura, attention is turned to the intramedullary component of the lipoma. With the ultrasonic aspirator or the CO2 laser, the lipoma is progressively thinned until a
smaller layer of fat remains against the neural tissue. No attempt is made to completely excise all fat, but the bulk of the lesion is removed, which then allows reconstitution of a neural tube in most patients. This is done with fine inverted nonreactive suture (Fig. 10–5). Attention is then directed to the filum terminale, which may be thickened. Again, it is separated from the surrounding exiting roots and sectioned. The dura is reapproximated, allowing a capacious CSF space dorsal to the newly formed neural tube. The superficial soft tissues are reapproximated, but not at the expense of the dorsal CSF space. Numerous variations on this anatomical theme exist. One that deserves special comment occurs when the subcutaneous lipoma is asymmetrically situated off the midline and opposite to it is a cleft of grayish blue, thin epithelium. The thinned epithelium is seen to be blue from an underlying CSF collection being formed by a terminal syringohydromyelia (Fig. 10–6). Operatively, this lesion is approached in a similar manner, with circumferential dissection of the subcutaneous lipoma and cyst. With the last intact lamina removed, the dura is opened to expose the caudally displaced spinal cord. The plane between the dura-lipoma complex and the fatty infiltrated cord is again key. The cord may be quite expanded by the combination of fatty infiltration and enlargement of the central canal. Draining the cyst at this point may facilitate the circumferential dissection around the dural attachment
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Figure 10–4 (A) A three-dimensional view of a lipomyelomeningocele demonstrating the dura-lipoma complex and the position of the exiting dorsal roots. This relationship varies somewhat from patient to patient and with the degree of rotation of the cord. (B) A surgical view showing a hooked knife being used to open the dura while the cord is rotated slightly for better exposure of the dorsal roots. The upper part of the lipoma is also being excised by the CO2 laser.
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Figure 10–5 Following resection of the bulk of the intramedullary lipoma, the distal cord is reconstituted into a neural tube with inverted fine nonreactive sutures (upper inset). Last, the thickened filum terminal 10.1055/978-1-60406-039-3c010_f005
to the neck of the lipoma. The dura, too, may be infiltrated by fat. This makes adequate dural closure technically demanding. With careful dissection and constant changing of perspective, eventually the circumferential opening of the dura-fat interface can be accomplished. The dorsal roots may be seen to be adherent to the undersurface of the dura, and prior to each maneuver they should be sought. These roots are laterally displaced and will be seen to exit in an asymmetrical fashion. Excessive fat growing into the neural tissue will then be excised. The very caudal portion of the conus can be reconstructed into a neural tube. This may lessen the likelihood of secondary readherence at the site of separation. At times, a dural graft may be necessary. This can usually be harvested from the two-ply lumbodorsal fascia. Again, watertight dural closure with preservation of a capacious CSF space around the reformed neural tube is ideal.
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is sectioned. The dura is closed and a capacious CSF space dorsal to the newly formed neural tube is created (lower inset). This lessens the likelihood of retethering at the operative site.
The soft tissue closure superficial to the dura is performed in such a manner that the intradural contents are not constricted and, therefore, are less likely to become adherent.
Conclusion Long-term results following aggressive resection and repair of lipomyelomeningoceles are still being accumulated. What does seem clear is that the risk of a serious permanent injury from the operative manipulation is low in experienced hands and should be much less than 10%. The risks of spontaneous worsening without operation are high, probably greater than 90% within the first two decades of life. The likelihood of 5 to 10 years of clinical stability without further loss of neurological function following surgery is
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68 Pediatric Neurosurgery
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also high. If these are the representative risks and benefits, then early surgical intervention is reasonable and appropriate for most patients with this lesion. There are many anatomical variations within this category of congenital lesions. The experience and judgment necessary in the successful operative manipulation of this
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lesion are significant. This particular lesion should not be operated on by the surgeon who deals with it only occasionally. Serious loss of bladder and/or bowel function will occur with the inadvertent sacrifice of functioning nerve roots by the surgeon who does not perform this procedure regularly.
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11 Encephaloceles of the Anterior Cranial Base Jonathan P. Miller and Alan R. Cohen
The term encephalocele, derived from the Greek for “hernia of the brain,” is used to describe a congenital protrusion of intracranial contents beyond the normal confines of the skull. Encephaloceles are relatively rare malformations, occurring with a worldwide incidence of ~1 per 5000 live births. Because encephaloceles, which pass through the same internal skull defect, may project to different locations externally, the terminology used to describe them is often confusing and inconsistent. Conventionally, sac locations are described in relation to internal defects in the skull, not by proximity to external landmarks. Using this scheme, encephaloceles can be divided into two broad categories: those related to the cranial vault and those related to the cranial base. Cranial vault encephaloceles, which occur when the defect is on the outer surface of the skull, present as visible external masses and usually occur along the midline in the frontal, parietal, or occipital region, or rarely off the midline at the pterion. These are more common in females and account for the vast majority of encephaloceles encountered in the Western Hemisphere; the occipital encephalocele is the most frequent type seen in North America. Cranial base encephaloceles result from a defect in the basal skull. They are more common in males, and they are seen mostly in Southeast Asia, especially Malaysia, Burma, Indonesia, and Thailand, where they outnumber posterior cranial vault encephaloceles 9.5 to 1. Cranial base encephaloceles are subclassified into two types: frontoethmoidal (also called sincipital), which project forward and produce a mass on the face, and basal, which project downward and produce a mass in the nasopharynx. The frontoethmoidal encephalocele (Fig. 11–1) projects anteriorly and is seen as a visible defect on the face at the root of the nose, which accounts the term sincipital, derived from the Latin for the anterior and upper part of the head. The hernia sac usually passes through an enlarged foramen cecum, a normally blind opening between the frontal crest anteriorly and the crista galli posteriorly. Frontoethmoidal encephaloceles are subdivided anatomically into three types based upon the site of the external skull defect opening into the face: nasofrontal, nasoethmoidal, and naso-orbital. Nasofrontal encephaloceles project onto the face at the nasion through an opening between the frontal bone above and the nasal and ethmoid bones below. This is the site of the primitive fonticulus nasofrontalis, a fibrous membrane
bridging the nasal and frontal bones during embryological development that separates the dura from the developing skin. Nasoethmoidal encephaloceles are long-necked and project somewhat more inferiorly, between the frontal and nasal bones above and the displaced ethmoid bone and nasal cartilage below. Naso-orbital encephaloceles are rare and project through the inferomedial wall of the orbit, passing between the frontal process of the maxillary bone anteriorly and the lacrimal bone and lamina papyracea of the ethmoid bone posteriorly. By contrast, basal encephaloceles (Fig. 11–2) protrude downward into the nasopharynx, either directly through the cribriform plate or body of the sphenoid bone, or through an enlarged foramen cecum. Because herniation occurs internally, there may be no obvious visible external mass and clinical presentation is often more insidious. They usually present as nasal (or rarely pharyngeal) mass, with symptoms of nasal airway obstruction. Also, because the defect is close to the suprasellar cistern, these are much more likely to contain important neurovascular structures than frontoethmoidal encephaloceles. Basal encephaloceles are variously divided into subcategories such as sphenopharyngeal, spheno-orbital, sphenomaxillary, sphenoethmoidal, and transethmoidal, depending upon the exact location of the defect. Other midline facial anomalies may be seen, such as cleft lip, cleft palate, or hypertelorism; they are sometimes discovered incidentally during craniofacial reconstruction for hypertelorism. The contents of the encephalocele sac are quite variable. Most often, cerebrospinal fluid (CSF) and gliotic brain are found, but large amounts of brain tissue are not uncommon, and many critical structures such as the hypothalamus, optic apparatus, and anterior cerebral arteries have been encountered in large herniations. Unlike those of the cranial vault, anterior cranial base encephaloceles are not usually associated with neurological abnormality, although hydrocephalus and epilepsy have been reported. They are sometimes associated with other abnormalities such as microphthalmia, corneal opacity, coloboma, craniosynostosis, and corpus callosum agenesis or lipoma. The purpose of this chapter is to describe the clinical management of encephaloceles at the anterior skull base. Cranial vault encephaloceles are discussed elsewhere in this volume.
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Figure 11–2 Basal encephalocele. The stalk passes through a defect in the floor of the anterior fossa at the site of the foramen cecum. The sac terminates in the nasal cavity between the septum medially and the middle turbinate laterally. 10.1055/978-1-60406-039-3c011_f002
Preoperative Preparation
Figure 11–1 Frontoethmoidal (sincipital) encephalocele; three variants. Each of these projects anteriorly to create a visible deformity at the root of the nose. (A) Nasofrontal encephalocele passing between the frontal bone above and displaced nasal and ethmoid bones below. (B) Nasoethmoidal encephalocele passing between the frontal and nasal bones above and displaced ethmoid bone and nasal cartilage below. (C) Naso-orbital encephalocele projecting externally through the medial wall of the orbit. 10.1055/978-1-60406-039-3c011_f001
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The most common clinical presentation of a frontoethmoidal encephalocele is a visible protrusion on the face at the root of the nose. Basal encephaloceles, on the other hand, are often more insidious, and they can present with nasal obstruction, mouth breathing, snoring, CSF rhinorrhea, recurrent meningitis, or nasal discharge due to purulence in the nasopharynx. The encephalocele sac is visible in the nasal cavity, lying between the septum medially and the middle nasal turbinate laterally. It may be visualized as a glistening pink or blue intranasal mass that pulsates with the heartbeat and may swell with crying or Valsalva maneuver. Unique features of nasal encephaloceles are their tendency to enlarge with compression of the jugular veins (so-called positive Furstenberg test) and their tendency to be crossfluctuant with compression of the anterior fontanelle. Encephaloceles must be differentiated from other nasal masses. Nasal polyps are rare in infants and are located lateral rather than medial to the middle turbinate. Other congenital nasal lesions in the differential diagnosis include dermoids, lipomas, fibromas, hemangiomas, teratomas, and nasopharyngeal cysts. In older individuals, basal encephaloceles must be distinguished from a variety of benign and malignant skull base tumors, as well as inflammatory lesions such as mucoceles and granulomas of the nose and paranasal sinuses. Some authors distinguish the nasal en-
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cephalocele from a related clinical entity, the so-called nasal glioma, although these lesions appear to share a common embryology. The nasal encephalocele is distinguished from a nasal glioma by the presence of a stalk connecting the nasal mass with the brain. This distinction is sometimes difficult to make clinically, but it may be significant as nasal gliomas (and not encephaloceles) may be biopsied safely via a transnasal approach. Radiographic demonstration of an anterior skull-base encephalocele is best performed with magnetic resonance imaging (MRI). The midsagittal image provides a beautiful demonstration of the hernia sac passing through a defect in the frontal floor to terminate in the nasal cavity. MRI is also useful for detecting the rare instance in which important neurovascular structures pass into the encephalocele sac. Angiography is not routinely necessary but may be considered if MRI suggests involvement of the anterior cerebral arteries in the herniation. Computed tomography (CT) is often helpful to delineate the bony anatomy, and threedimensional CT can be helpful for planning more complex craniofacial repairs.
Operative Procedure Historically, anterior cranial base encephaloceles have been approached both transnasally and transcranially. The transnasal route is now rarely performed because of significantly higher risks of bleeding, infection, and CSF fistula formation. The transcranial approach was first described by Dandy in 1929, and variations are still commonly used. An encephalocele with a relatively narrow neck and a sac that terminates in the nasal cavity can be approached either intradurally or extradurally, and there is continued controversy over which is the better way. If there is a broad stalk or inclusion of critical neurovascular structures within the encephalocele, a combined extradural-intradural exploration may be appropriate. Encephaloceles associated with hypertelorism or those projecting onto the face are more complex and are best repaired in conjunction with a craniofacial team. For both the intradural and extradural approaches, preoperative nasal cultures are obtained and the patient is given anticonvulsants and antibiotics appropriate for staphylococci and streptococci. The operation is performed under general anesthesia with oral endotracheal intubation. Arterial, venous, and Foley catheters are inserted. Although the procedure is not usually associated with significant blood loss, even minor bleeding may have serious consequences in young infants, so blood is made available for transfusion. In older infants and adults, a lumbar subarachnoid catheter is used for intraoperative drainage of CSF. The patient is positioned supine on a warming blanket and covered with a regular blanket to minimize heat loss. The head is supported by a “doughnut” cushion, elevated 20 degrees, and extended with the brow up. Adults are positioned in a similar fashion using a Mayfield three-pin fixation device (Schaerer Mayfield, Cincinnati, Ohio). The scalp is then shaved and cleansed with alcohol followed by povidone-iodine soap and solution. A coronal incision well behind the hairline is outlined with a marking pen (Fig. 11–3). The operative
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Figure 11–3 Patient positioned for bifrontal craniotomy. A coronal scalp incision is outlined (dashed line). 10.1055/978-1-60406-039-3c011_f003
field is walled off with towels and covered with an iodoform-soaked adhesive drape. The scalp is infiltrated with a solution of 0.1% lidocaine with a 1:1,000,000 dilution of epinephrine. The incision is made with a no. 10 scalpel, and scalp hemostasis is obtained using Raney clips and Dandy clamps. Alternatively, in younger infants the scalp may be opened using a Shaw hemostatic scalpel. The scalp is reflected anteriorly in the avascular loose areolar plane, which lies deep to the galea but superficial to the pericranium. Great care is taken not to disturb the pericranium, which is mobilized as a separate vascularlized layer to reconstruct the skull base at the close of the procedure. The pericranium is incised with a knife and reflected anteriorly using squareended periosteal elevators. The pericranial flap is based on a vascular pedicle supplied by the frontal and supraorbital arteries. Any holes in the pericranial flap are repaired at this point using 4–0 Nurolon sutures. The scalp and pericranial graft are covered with moist sponges. For the extradural or combined approach, a bifrontal free bone flap is fashioned (Fig. 11–4). Bur holes are placed in the keyhole region bilaterally, and a small bur hole is placed in the low frontal midline using a high-speed drill (e.g., Midas Rex; Medtronic Inc., Fort Worth, Texas). The frontal sinus does not present a problem in infants because it is not yet pneumatized. A posterior midline bur hole can be avoided by using a knife and dental instrument to create “suturotomies” and separate
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10.1055/978-1-60406-039-3c011_f004 Figure 11–4 A bifrontal bone flap is (A) created and (B) removed. Note the preservation of a vascularized pericranial flap, which is projected anteriorly prior to the craniotomy. After removal of the encephalocele, this
dura from bone on either side of the anterior fontanelle. The bone flap is elevated using the high-speed drill and footplate system to connect the holes, with cuts directed away from the midline. The dura is tented up to the posterior margins of the craniotomy defect using 4–0 Nurolon sutures. The dura is then dissected gently off the floor of the anterior cranial fossa bilaterally using a Freer elevator or a bayonet forceps and cottonoid patties. The dissection is usually not difficult, but it can be troublesome medially in the region of the cribriform plate. When necessary, the dissection may be facilitated by the use of hyperventilation, mannitol, and drainage of CSF from the lumbar catheter to relax the brain. The surgeon can then identify the encephalocele stalk as it
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flap is sutured to the basal frontal dura and serves as a barrier between the remnant of the encephalocele stalk above and the bony defect opening into the nasal cavity below.
enters the bony defect at the foramen cecum (Fig. 11–5). The stalk is dissected circumferentially. A 4–0 Nurolon sutureligature is placed through and around the encephalocele stalk, and the stalk is divided with scissors just distal to the site of ligation (Fig. 11–6). The intracranial portion of the encephalocele is thereby disconnected from the intranasal portion of the sac, which may be grasped from below by an otolaryngologist and delivered through the nose (Fig. 11–7). If the nasal sac is tenacious, it is left alone and will either shrivel up, requiring no further treatment, or alternatively it may be removed easily after several weeks at a second sitting. Hemostasis is secured, and the ligated basal frontal dura is covered with a piece of thrombin-soaked Gelfoam,
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Figure 11–5 Extradural approach. The encephalocele stalk is identified and isolated. 10.1055/978-1-60406-039-3c011_f005
which may be infiltrated with fibrin glue. Bony reconstruction of the skull base is usually not necessary, but very large defects may benefit from a graft to support the dural repair and lessen the risk of a postoperative CSF leak. The vascularized pericranial graft is brought down to cover the skull base and is fixed to the frontobasal dura with 4–0 Nurolon sutures (Fig. 11–4B). After replacement of the bone flap, the scalp is closed in two layers. For the intradural approach, a unilateral craniotomy will suffice. The craniotomy is therefore made to midline and extended low toward the cranial base. The dura is opened, and the brain is gently retracted upward to reveal the root of the defect (Fig. 11–8). The stalk is amputated; at this point, the encephalocele can be pulled out through the nose by an otolaryngologist. The space at the base of the skull is then covered with a small piece of fat or Gelfoam and fibrin glue. A vascularized pericranial graft can be used to reinforce the repair. The dura is then closed in a watertight fashion, and
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the bone flap and scalp are closed. In older children and adults, the lumbar subarachnoid catheter is left in place for up to 5 days to protect the operative repair.
Postoperative Management Including Possible Complications Complications are generally related to infection or the formation of a CSF fistula, both of which may occur as a result of communication between the subarachnoid space and the nasal cavity. The risk of such a communication can be minimized by a meticulous dural closure protected by a vascularized graft of pericranium. For the same reason, a subgaleal drain should not be placed. If a CSF fistula develops, lumbar drainage for a few days will often solve the problem, but if not, the wound should be explored surgically.
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Figure 11–6 (A,B) The stalk of the encephalocele is ligated with a suture ligature and (C,D) is transected. 10.1055/978-1-60406-039-3c011
Conclusion Encephaloceles of the anterior cranial base are rare malformations that can present insidiously. Straightforward lesions may be approached intracranially using either an extradural or an intradural dissection, whereas more complex lesions may require a combined intradural-extradural
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approach. Goals of surgery should be protection of neurovascular structures and prevention of a CSF fistula. Although they are more difficult to repair than the posteriorly situated occipital encephaloceles, they are associated with a much better neurological prognosis, and outcome for most patients is excellent.
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Figure 11–7 (A) The sac of the encephalocele is removed transnasally (B) after its stalk has been ligated and divided intracranially. 10.1055/978-1-60406-039-3c011_f007
Figure 11–8 Intradural approach. After unilateral craniotomy, the dura is opened and the frontal lobe gently retracted to reveal the encephalocele. 10.1055/978-1-60406-039-3c011_f008
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12 Exorbitism Constance M. Barone, David F. Jimenez, and James Tait Goodrich
Patient Selection Exorbitism or proptotic eyes secondary to craniofacial dysostosis is a consequence of shallow orbital sockets and is not due to enlargement of the orbital contents (Figs. 12– 1A—12–1C). Therefore, corrective surgery for this problem consists of increasing the depth of the orbital cavities. This correction may be undertaken in two operations: as a fronto-orbital advancement done at 3 to 6 months of age, and later as a midface advancement done after the age of 4 years, preferably during adolescence. The midface operation should not be performed on the very young because their tooth buds are located high up in the maxilla and the osteotomies will disrupt them, leading to severe dental problems as the child grows. Some surgical teams have chosen to perform both operations as a single-step procedure, that is, the monoblock advancement. There is a much greater risk of infection with the monoblock procedure and that, along with the high incidence of tooth bud disruption, has led us to perform a two-stage procedure. Exorbitism and midface retrusion are commonly observed in craniofacial dysostosis, for example, Crouzon’s and Ap-
ert’s syndromes. Exorbitism, however, may occur without any midface deformity or dental malocclusion, as is demonstrated in the patient presented here. Correction in this particular case could be accomplished by orbitonasal osteotomies through bicoronal, lower lid, and buccal incisions. The principle in such surgical procedures is to restore a satisfactory aesthetic balance by recontouring the face with both advancements of bone units and onlay grafts if necessary. Our craniofacial team has elected to do our facial onlays and reconstructions with calvarial bone. Because it is membranous, the use of this type of graft lessens significantly the risk of graft resorption, which occurs occasionally with rib (endochondral bone) grafts. However, the techniques of both calvarial bone and rib harvesting will be discussed.
Preoperative Evaluation At our medical centers all patients with craniofacial disorders are evaluated at the respective Center for Craniofacial Disorders. The patient is evaluated by specialists from the fields of pediatrics, pediatric neurology, pediatric neurosurgery, genetics, plastic surgery, ophthalmology, dentistry,
Figure 12–1 (A–C) Three views of a patient with exorbitism.
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12 dentofacial surgery, otolaryngology, and speech therapy. All patients have plain x-ray films of the face and skull as well as computed tomography (CT) scanning with bone windows in axial and coronal planes. We now routinely use threedimensional CT scan reconstruction preoperatively. With the software programs available we can perform measurements and surgical osteotomies on the reconstructed CT model preoperatively. With this technique we are able to calculate the amount of advancement as well as the amount of bone to be harvested for the reconstruction. We have not found magnetic resonance imaging to be helpful in these cases.
Preoperative Preparation We routinely start an anti-staphylococcal antibiotic at the start of the operation. Because the surgical manipulations are all extradural, we do not routinely use anticonvulsant medications or steroids. Because there is considerable bone harvesting and multiple osteotomies in these procedures, the surgical team should be prepared for blood loss that is significant enough to require transfusion. If the family is interested, we routinely plan for pedigree (donor-directed) blood donations. If available, a cell saver unit can rescue up to 50% of the patient’s lost blood volume. Because of the risk of extensive blood loss, all patients require at least two large-bore intravenous lines of 16 gauge or larger. If there is any history of cardiac or pulmonary problems, we routinely put in a central venous pressure line. An arterial line is mandatory for monitoring blood gases, hematocrit, electrolytes, etc., during the procedure. For an advancement of the orbital rims alone, 2 units of packed red blood cells are made available. However, if the midface is also included in the advancement (i.e., a Le Fort III disconnection), 4 units of packed cells are made available. If a Le Fort III disconnection is planned and the patient is to be placed in intermaxillary fixation, then a tracheostomy should be considered. If the orbital rims alone are all that will be advanced, as in this case, then we routinely use orotracheal intubation. Ideally, the endotracheal tube should be sutured to the gingiva, around a tooth using a heavy silk suture, to prevent inadvertent extubation during the operation. To protect the eyes from corneal abrasions and exposure during the procedure, all patients have bilateral tarsorrhaphies prior to formal draping. If corneal shields are available, these may be used in place of the tarsorrhaphies.
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is essential during the operation to provide various views of the facial region. Anesthesia equipment is on the left side of the patient, placed below the patient’s shoulder level. The operating surgeon sits at the head of the patient with the assistant to the right of the surgeon. The instrument tray comes in over the patient’s abdomen but is positioned no higher than the midthoracic region. The surgical team therefore has access to both sides of the patient’s head as well as intraoral access. For this reason we avoid the use of bulky overhead tables that reduce access and visualization of the face.
Draping Because a bicoronal incision as well as intraoral and infraorbital incisions will be used, the entire face and mouth must be prepared in addition to the scalp. The mouth is irrigated copiously with Betadine (providone-iodine) solution, and the nares are also cleansed with cotton swabs soaked in Betadine solution. The head is shaved along the proposed bicoronal incision for a width of ~1.5 cm. We no longer do full-head shaving. Patients (or their parents) are quite appreciative of being able to comb the hair over the wound 1 week later. We have had no increased incidence of wound infections since starting this technique more than ten years ago. The head and entire face are then cleaned with Betadine scrub, cleansed with alcohol, and painted with Betadine solution. In an adult, the bicoronal incision site is then injected with 0.5% lidocaine and a 1:200,000 epinephrine solution. In a child (<7 years old) we use 0.25% lidocaine and a 1:400,000 epinephrine solution. Sterile towels are placed below the posterior portion of the bicoronal incision and are also stapled to the posterior aspect of the scalp. A facial drape is then placed over the lower lip, chin, and endotracheal tube. It is important that the drapes are loose so that the head can be moved during the procedure. We routinely run all our suction lines, cautery cords, etc., toward the foot of the patient. Because the surgical team sits, this allows easy mobility of the chairs (i.e., the chairs are not rolling over the cords and tubes). Because the operative site is heavily irrigated during the procedure, it is important to have waterproof outer drapes. Some of the newer drape designs have large plastic bags for fluid collection; we have found these to be quite useful.
Skin Incisions and Flap Elevation
Operative Procedure Positioning The patient is placed in the supine position with the head resting on a cerebellar (horseshoe) headrest. The head is placed in a slightly extended, brow-up position. Rigid fixation devices such as a Mayfield clamp are specifically avoided because the surgeon will need to move the head (although usually never more than 10 to 151 degrees: This flexibility
To gain access to the frontal bone, the supraorbital rims, and the nasal bridge, a bicoronal scalp incision is used. This incision is carried from tragus to tragus, well behind the hairline. A full-thickness skin flap is elevated, leaving the pericranium intact. The pericranial flap is then elevated separately as a second layer. Frequently the supraorbital nerve and artery are encased in a bony canal along the supraorbital rim; they can be freed by removing the anterior wall of the supraorbital canal with an osteotome or small Kerrison punch. The temporalis muscles are left intact and are elevated in a fan-shaped fashion from each temporal
78 Pediatric Neurosurgery fossa using a monopolar electrocautery. The dissection is carried forward and over the supraorbital rims following the subperiosteal plane and extending into the orbits to a depth of ~1.5 cm. The lateral portions of the orbit and the frontozygomatic process are also exposed on each side. To gain access to the inferior orbital rims, a lower eyelid incision is made on each side at the junction between the lower lid skin and the cheek skin. This incision is carried through the orbicularis oculi muscle onto the infraorbital rim. Subperiosteally, the orbital contents are elevated off the orbital floor to a depth of ~3 cm. The medial orbital contents as well as the lateral inferior orbital contents are elevated in a similar manner. Care is taken to preserve the infraorbital nerve. As an alternative, a subciliary incision can be used; however, this makes the dissection somewhat more difficult and introduces the possibility of an undesirable postoperative ectropion and/or ciliary inversion. At this point, the entire orbital contents are freed from their bony encasement in a subperiosteal plane. Next an intraoral, transbuccal incision is performed that extends across the midline of the pyriform aperture. The pyriform aperture and maxilla are exposed following the subperiosteal plane. Once again, care must be taken to protect the infraorbital nerves. Gentle retraction of the globes should be observed at all times.
Calvarial Bone Harvesting A large amount of calvarial bone is readily exposed via the bicoronal incision. Calvarial bone can be harvested utilizing one of two methods. The first method requires a craniotomy. A full-thickness piece of calvarial bone is removed and then split along the diploic space using the Midas Rex drill with a C-1 attachment and a reciprocating saw. The thickest bone is found over the parietal region. Once the bone has been split, the inner table is placed back in the donor site. The outer table is then used for reconstruction (the outer table has smoother contours, making it better for the aesthetic reconstruction). A second technique for bone harvesting does not require a craniotomy. A trough is developed around the edges of the proposed piece of bone. The trough is easily created with an olive-tip drill. Curved osteotomes are then used to split the calvaria along the diploic space, thereby elevating the outer table. Care must be taken to avoid getting too deep because the dura can be torn inadvertently. It is best to harvest a bone graft from the side of the nondominant hemisphere.
Rib Graft Harvesting Another technique for bone harvesting is the rib graft technique. This is easily done via an inframammary incision. Through this incision, adjacent ribs can be removed; usually ribs six and seven are selected. The ribs are dissected by first incising the anterior periosteum and then using a Key periosteal elevator to raise the anterior periosteum from the rib, an Alexander elevator is used to strip the superior and inferior borders of the rib free. A Doyen periosteal elevator is then used to separate the posterior (or deep) periosteum
from the undersurface of the rib. Care must be taken not to injure the underlying pleura. Prior to closure, irrigation with saline is performed while the anesthesiologist manually inflates the lungs to check for bubbling, a sign of an air leak. If a leak is found, the pleura has been entered inadvertently during the dissection. The tear should be repaired and a small red rubber tube (no. 10 French) placed into the pleural space. The tube is then placed to low water-seal suction (~20 ml water pressure). The donor site is closed in layers. When the patient is in the recovery room, an x-ray film of the chest is obtained. If there is no evidence of a pneumothorax, the chest tube is removed and an occlusive petroleum gauze dressing is applied. The harvested ribs are split along the superior and inferior borders using an osteotome and contoured using a Tessier rib bender. This technique doubles the available amount of rib bone for grafting.
Craniofacial Osteotomies With a reciprocating saw, the osteotomy is initiated across the nasal radix and extended to the medial orbital walls above the level of the lacrimal fossa. This area is easily approached via the bicoronal incision. Laterally, the osteotomy extends on the frontozygomatic process. This is done in a stepwise fashion, with the assistant using a malleable retractor to protect and retract the orbital contents (Fig. 12–2). During this stage of the operation, the anesthesiologist should monitor the vital signs closely; if there is too much traction on the globe, the blood pressure will increase and the heart rate will decrease. An osteotomy is then made across the orbital floor, back ~1.5 cm from the orbital rim. This osteotomy, most easily done via the lower lid incision, is extended across the medial orbital wall, finally connecting the osteotomy lines of the medial orbital walls together. During this dissection it is mandatory to protect the orbital contents with a malleable retractor. Outside the orbits the lateral cut continues along the body of the zygoma and then proceeds medially, below the infraorbital foramen and toward the pyriform aperture of the nose. This osteotomy is done through an intraoral approach. The process is repeated on the opposite side. The nasal septum is cut after a submucosal dissection has been performed. All the osteotomy lines should now be connected. The thin bones are easily fractured as the orbitonasal unit is mobilized in a forward and slightly downward direction. The spur that is developed in the inferior segment is made to abut against the rim of the superior segment after the lower part of the orbit is advanced. Autogenous bone blocks obtained from the split calvaria (or split rib) are impacted into the nasofrontal and zygomatic defects and secured in place using miniplates, microplates, or wires (Fig. 12–3). Split rib grafts or split calvarial grafts are then laid over the gaps created over the maxilla and orbital floors. Additional strips of either rib grafts or calvarial grafts are placed and either wired or lag screwed to the supraorbital rims. The pericranial flap is then placed over the superior orbital rims and the bone grafts in this area.
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Figure 12–2 Artistic reconstruction showing the various osteotomies and bone onlays. 10.1055/978-1-60406-039-3c012_f002
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Figure 12–3 Artistic reconstruction showing the bone onlays from a lateral view. 10.1055/978-1-60406-039-3c012_f003
Closure It is especially important to use extreme care with the globes and lacrimal system during the orbital dissection. If not, a fistula can occur. If proper care is not taken with the medial osteotomies, the surgeon may inadvertently extend into the cribriform plate and thus enter the anterior cranial fossa. If this happens, there is the possibility of a dural tear and subsequently a cerebrospinal fluid (CSF) leak. It is often useful at the end of the operation, prior to elevating the skin flap, to have the anesthesiologist perform an extended Valsalva maneuver while the surgeon looks for a CSF leak. If a CSF leak occurs in the postoperative period, a lumbar spinal drain placed for 5 to 7 days usually corrects the problem. If not, the patient has to be reexplored and the leak sealed.
Closure of the bicoronal incision begins with copious irrigation and hemostasis. Particular attention must be paid to the skin folds and the gutter space that develop because debris collects here and offers the most potential for infection. The temporalis muscles are then laid back in their proper position and secured into place using Vicryl sutures. These sutures are easily placed through the hole of the microplates or though holes made in the frontal bone. A drain is placed and attached to light suction for 48 hours. Scalp closure is accomplished using both galeal layer and the skin layer. The lower eyelid skin incisions are closed in a single layer using fine nylon (less than 5–0), which must be applied meticulously to reduce scarring. The mouth is again irrigated with Betadine solution, and the transbuccal incision is closed using a single layer of absorbable sutures.
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Figure 12–4 (A–C) Postoperative views of the patient 1 year after surgery.
The tarsorrhaphy sutures are then removed and the eyes irrigated with a balanced salt solution. Lacri-Lube (Allergan, Irvine, CA) is placed on both eyes and a head dressing is applied. Excellent results can be obtained using these aforementioned techniques (Figs. 12–4A—12–4C).
Postoperative Management Including Possible Complications Intensive care monitoring for at least 48 hours postoperatively is highly recommended for these patients. Because of the blood loss that can occur and the risk of epidural hematoma formation, hemodynamic monitoring is mandatory. The patient is kept on antibiotics for 3 days postoperatively. The patient takes a clear liquid diet for 3 days and
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then advances to a soft diet, rinsing the mouth with saline between meals throughout this period. After a period of 1 to 2 weeks, the patient usually may resume a regular diet. There will be significant postoperative periorbital swelling, especially by the third postoperative day, but this resolves gradually. It is often helpful to warn the parents and patient of this swelling preoperatively. The bone grafts may undergo resorption with time. If this happens, the patient may require future contouring. As mentioned previously, there is evidence that calvarial bone undergoes less resorption than rib grafts.
Distraction Osteogenesis Distraction osteogenesis utilizes application of a slow traction force on the osteotomeized bony segments, allowing new bone formation in the gap. This technique not only
C
Figure 12–5 (A) Profile view of Crouzon’s patient with shallow forehead and retruded infraorbital rims. (B) At the conclusion of monoblock distraction with the internal device. (C) Eight months after the removal of the distraction device. The exorbitism and midface retrusion have improved. 10.1055/978-1-60406-039-3c012_f005
82 Pediatric Neurosurgery expands the skeleton, but also the surrounding soft tissue, thereby avoiding the need for bone graft, and the relapse rate is lower. Distraction osteogenesis is particularly useful for monoblock advancement because there is no immediate creation of dead space. And thus, the infection rate is decreased. The distraction device can be either internal or external. In general, the external device offers a better three-dimensional control of the advancement. Fig. 12–5A shows a 5-year-old child who has Crouzon’s syndrome who presented with exorbitism. He has both flat forehead and shallow infraorbital rim in addition to retromaxillism. He is an ideal candidate for monoblock advancement. The frontal craniotomy is first performed, followed by Le Fort III osteotomies. It is critically important to completely mobilize the Le Fort III segment. Distraction is applied, and the frontal bone flap is fixated to the distraction device at a rate of 1 mm advancement per day (Fig. 12–5B). When the supraorbital rim and infraorbital rim reach the desired position, the distraction process is concluded. The
distraction pins are left for an additional 6 to 8 weeks for the bone to heal, known as the consolidation phase. The patient is then returned to the operating room to remove the distraction device. With the advent of the resorbable footplates, only the activation pins need to be removed at the bedside (Fig. 12–5C). Acknowledgment This chapter is a revision of the chapter, “Correction of Exorbitism” by Constance M. Barone, M.D., Ravelo Argamaso, M.D., David F. Jimenez, M.D., and James T. Goodrich, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 2, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Ravelo Argamaso, M.D., for his help and efforts on the original chapter published in the first edition of this work.
13 Depressed Skull Fracture in Infants Marion L. Walker
Patient Selection The depressed skull fracture in infants <1 year of age differs from depressed fractures in the older age groups. This is due to the relative plasticity of the skull, which is not yet fully ossified. These fractures, referred to as “ping-pong fractures” because of their resemblance to an indented pingpong ball (Figs. 13–1A and 13–1B), may often be treated by a conservative approach. Observation may be the only treatment required. These fractures will frequently remold within a short time, especially in newborns, making surgical approaches unnecessary. A surgical procedure is usually not indicated if remolding occurs, but if elevation of the fracture is needed the surgery is much less invasive than the typical depressed skull fracture requires. The surgery is generally nonemergent and is usually done weeks following the injury, after there has been adequate time to document that the fracture will not appropriately remold. It has been reported that, in newborns, the bone will eventually remodel to a normal contour without any surgical intervention. This may indeed occur, but signs of remodeling of the bone should begin within a few weeks. Prolonged pressure of the depression on the cortex could potentially generate a seizure focus, although this possibility is quite rare. The potential risks of the surgery are infection, intracranial hematoma formation, and blood loss. However, with good surgical technique the possibility of complication is very low.
Preoperative Preparation Anesthetic Considerations Anesthetic considerations are very important in this young age group. Current studies suggest that the child should have nothing by mouth for at least 3 hours after drinking clear fluids and for 4 to 6 hours after ingesting formula or milk. Good intravenous access is essential and blood should be available. After the induction of anesthesia, prophylactic antibiotics are given. Increased intracranial pressure usually is not a problem. Narcotics should be avoided in this age group. It is recommended that the arterial oxygen saturation levels be maintained at 90 to 93%. The young infant has
difficulty maintaining body temperature due to decreased insulation and the large amount of surface area of the head. Heat loss should be a major concern and the room must be kept warm. When the child is exposed, warming lights should be used. A heating blanket is always placed on the operating room table. Warming the anesthetic gases also helps to prevent hypothermia.
Operative Procedure The child is positioned on the operating table with a roll placed behind the back to create a 45 degree angle between the patient and the table (Fig. 13–1C). The head is turned to lie directly lateral. The partial lateral position of the body relieves any potential stress to the cervical musculature and ensures that there will be no obstruction of venous return. The incision is then outlined in a pattern extensive enough to encompass a scalp incision surrounding the fracture should this become necessary. When the child is draped, an area large enough to accommodate a larger incision around the fracture site should be allowed. The initial incision should be ~1.5 cm in length along the suture line nearest to the depressed fracture, most often the coronal suture, and at least 2 to 3 cm from the midline (Fig. 13–2A). The periosteum is opened with a Bovie electrocautery. A periosteal elevator is used to free the periosteum and delineate the bone edge at the suture line (Fig. 13–2B). The periosteal elevator is then used to strip the dura from the bone in a sweeping fashion until the depression of the bone is reached (Fig. 13–2C). With consistent gentle upward pressure, the periosteal elevator is used to lever the bone from a concave to a convex position (Fig. 13–3). In many cases, the surgeon will feel a snap as the bone resumes its normal contour. The bone can splinter, and gentle sweeping motions while continuing upward elevation may be necessary. Care should be taken not to push the instrument through a fracture line if one is present. Counter-pressure is obtained by placing the thumb or index finger of the opposite hand over the defect as pressure is exerted from below the fracture. This technique allows for greater control. Once the bone is elevated, the wound and epidural space are irrigated to ensure hemostasis. The galea is closed with 4–0 absorbable sutures in a simple interrupted fashion. The scalp may be closed with sutures or an adhesive substance.
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Figure 13–1 (A,B) The depressed skull fracture in an infant resembles an indentation in a ping-pong ball. (C) For operative treatment the child is placed supine, the shoulder is elevated 45 degrees, and the head is turned to a lateral position. 10.1055/978-1-60406-039-3c013
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13 Depressed Skull Fracture in Infants
Figure 13–2 (A) The 1.5 cm incision is made along the suture line nearest the fracture and a periosteal elevator is inserted. (B) The periosteal elevator is inserted through the suture line into the epidural space
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beneath the fracture. (C) The periosteal elevator is used in a sweeping motion, with upward pressure to elevate the fracture.
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Figure 13–3 (A) The periosteal elevator is passed through the suture, (B) is advanced into the epidural space beneath the fracture site, and (C) is used to lever the depressed bone back into a normal convex position.
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13 Depressed Skull Fracture in Infants
Postoperative Management Including Possible Complications The depressed skull fracture in the infant <1 year of age can be treated safely and effectively by the surgical method described if the fracture fails to remold within a reasonable time. The hospital stay is usually 24 to 48 hours. The results are excellent, and long-term sequelae may be avoided. The child is exposed to very little risk while undergoing this procedure.
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Acknowledgment This chapter is a revision of the chapter, “Depressed Skull Fracture in Infants” by Lyn C. Wright, M.D., and Marion L. Walker, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 2, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Dr. Lyn Carey, M.D., for her help and efforts on the original chapter published in the first edition of this work.
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14 Orbital Hypertelorism and Orbital Dystopia Constance M. Barone, David F. Jimenez, and James Tait Goodrich
Patient Selection
Preoperative Evaluation
Orbital hypertelorism is defined as true lateral displacement of the orbits. Clinically, this is seen as an exaggerated distance between the orbits. Normal measurements between the anterior lacrimal crests in Caucasian adults range from 18.5 to 29.9 mm for females and from 19.5 to 30.7 mm for males. Orbital dystopia refers to the position of the orbits aligned on the vertical axis. The 4-year-old girl presented here had craniofrontonasal dysplasia with both orbital dystopia and orbital hypertelorism. Her interorbital distance measured 34 mm preoperatively. Normal interorbital distance for a 4-year-old girl ranges from 13 to 21 mm, with the 50th percentile being 17 mm.
At the Montefiore Medical Center, all patients with craniofacial disorders are evaluated at the Center for Craniofacial Disorders. The patient is evaluated by individuals from the disciplines of pediatrics, pediatric neurology, pediatric neurosurgery, genetics, plastic surgery, ophthalmology, dentistry, dentofacial surgery, otolaryngology, and speech therapy. All patients have plain x-ray films of the face and skull as well as computed tomography (CT) scanning with bone windows in axial and coronal views. We routinely use three-dimensional CT scan reconstruction with a software program that allows us to perform measurements and surgical osteotomies on the reconstructed model preoperatively (Fig. 14–1).
Figure 14–1 Three-dimensional computed tomography reconstructions for preoperative planning. (A) The preoperative reconstruction shows the bony detail of the dystopia and orbital hypertelorism; from this image the amount of orbital movement required can be calculated. 10.1055/978-1-60406-039-3c014_f001
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(B) The orbital units are outlined. (C) The orbital repositioning necessary has been calculated and the bone units repositioned; the numbers generated by the computer are very helpful in determining the requirements for adequate positioning.
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procedure. For eye protection, all patients have bilateral tarsorrhaphies performed or corneal shields placed prior to formal draping. The patient is intubated orotracheally.
Operative Procedure Positioning The patient is placed in the supine position with the head on a cerebellar headrest. Rigid fixation devices such as a Mayfield head clamp are not used because the surgeon will need to move the head (never more than 10 to 15 degrees, however). Anesthesia equipment is on the left side of the patient and the nurse’s Mayo stand is placed over the midabdomen. Overhead tables are not used because they restrict frontal access and visualization of the patient’s head.
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Figure 14–2 A child with craniofrontonasal dysplasia manifested by orbital hypertelorism and orbital dystopia. 10.1055/978-1-60406-039-3c014_f002
In the patient presented here, the interorbital distance between anterior lacrimal crests was 34 mm. The right supraorbital rim was 8 mm lower than the left supraorbital rim, representing an orbital dystopia (Fig. 14–2). Multiple cranial defects were noted from a prior cranial operation at another institution. In addition, the nose was short, with the right nasal ala being higher than the left nasal ala. Such clinical findings are typical of those seen in children with craniofrontonasal dysplasia and require a complex craniofacial reconstruction.
Preoperative Preparation We routinely start antibiotic therapy (to cover for both skin and nasal flora) at the time of anesthesia induction in the operating room. Because all surgical manipulations are extradural, anticonvulsant and steroid therapies are not used routinely. With an extensive reconstruction in a 4-year-old child, two units of packed red blood cells are made available (preferably donor-directed). If available, a cell saver unit can rescue up to 50% of the patient’s lost blood volume. Because of the risk of extensive blood loss, all patients require at least two large-bore intravenous lines of 16 gauge or larger. An arterial line is placed during induction to permit serial blood gas and hematocrit measurements, etc., during the
Because a bicoronal incision as well as bilateral infraorbital incisions will be used, the head and the entire face down to the nose must be prepared. The nares are cleansed with cotton swabs soaked in Betadine (providone-iodine) solution. The head is shaved only along the proposed bicoronal incision for a width of ~1.5 cm. The face and head are cleaned with Betadine scrub, cleansed with alcohol, and painted with Betadine solution. In an adult, the bicoronal incision site is then injected with 0.5% lidocaine and a 1:200,000 epinephrine solution. In a child (<7 years old) we use 0.25% lidocaine and a 1:400,000 epinephrine solution. Sterile towels are placed below the posterior portion of the bicoronal incision and are also stapled to the posterior aspect of the scalp. A facial drape is then placed just below the nose and over the upper lip and endotracheal tube. It is important that the drapes are loose so that the head can be moved during the procedure. We routinely run all our suction lines, cautery cords, etc., toward the foot of the patient. Because our surgical team routinely sits, this allows easy mobility of the chairs (i.e., the chairs are not rolling over the cords and tubes). Because the operative site is often irrigated during the procedure, it is important to have waterproof outer drapes. Some of the newer drape designs have large plastic bags for fluid collection: We have found these to be quite useful.
Skin Incisions To gain access to the frontal bone, orbits, and nasal region, a bicoronal scalp incision is used. This incision is carried from tragus to tragus, well behind the hairline, both for a cosmetic closure and to allow for a large pericranial flap that can be used in the subsequent repair.
Flap Elevation A full-thickness scalp flap is elevated following the standard subgaleal plane, leaving the pericranium intact. The pericra-
90 Pediatric Neurosurgery nium is then elevated as a second separate layer. The flaps are carried forward to the orbital rims, to the level of the supraorbital nerve and artery on each side. These are frequently encased in a small notch of bone in the supraorbital rim. This notch can be opened easily using a small osteotome or small Kerrison rongeur. An inverted V-shaped skin incision is made on top of the glabelar region (Fig. 14–3) to allow proper nasal lengthening as well as resection of the excess skin after the orbits have been moved medially. If there is no asymmetry in nasal length, a midline incision is chosen. Particular care must be taken in elevating the scalp flap if the patient has had a prior operative cranial procedure (as did the patient presented here) because multiple bony defects may be present that cause the dura to be adherent to the overlying pericranium and galea. The scalp flap dissection must expose the belly of the temporalis muscle and the zygomatic arch bilaterally. In the central facial region, the nasal bones as well as the medial orbital wall should be exposed fully. The temporalis muscle is elevated as a unit using a monopolar needle tip electrocautery. To gain access to the infraorbital region as well as the maxilla, a lower eyelid incision is made between the cheek skin and the periorbital skin. This incision is made within a natural skin fold and usually is located directly above the infraorbital rim. As an alternative, a subciliary incision can be performed and the skin elevated as a skin-muscle flap. However, this sometimes leads to an ectropion and/or to subciliary inversion, so we are not as likely to use it.
Craniofacial Osteotomies A frontal craniotomy is performed ~2.5 cm above the superior orbital rims (Fig. 14–4). The use of a high-speed drill is preferred (e.g., Midas Rex drill with a 13–5 footplate [Medtronic Inc., Fort Worth, Texas]), which allows speedy bone removal in a single step and thus decreases blood loss. The frontal lobes are then gently retracted extradurally, thus exposing the orbital roof and anterior cranial fossa on each side. Filaments from the olfactory bulbs are cut, and the dura is oversewn if cerebrospinal fluid (CSF) leakage is noted. Subperiosteal elevation of the scalp flap continues over the orbital rims into the orbits to a distance just past the equators of the globes. A horizontal osteotomy is performed 1.5 cm above the superior orbital rims (Figs. 14–4 and 14–5). This leaves a horizontal bar or bandeau of bone attached to the cranium. A block of bone below the bandeau, consisting of the crista galli, the nasal bones, and the ethmoid bones, is removed en bloc using the Midas Rex drill with a C-1 attachment and an osteotome. The ethmoid sinuses are then exenterated carefully using pituitary rongeurs. Care must be taken to remove all mucosa so that a mucocele does not develop in the future. The cartilaginous nasal septum is identified between the septal mucosa and is dissected free from the mucosa. A septal resection is performed, with removal of all of the septal cartilage between the medial orbital walls. This creates room for the medial translocation of the orbitonasal complex and maintains an open airway. Tears in the nasal mucosa are repaired with chromic catgut sutures. A segment of the removed nasal bone is then placed in the midline opening at
Figure 14–3 An intraoperative view showing the V-Y correction to shorten the nasal bridge and correct the excessive nasal skin from a medial movement of orbits. 10.1055/978-1-60406-039-3c014_f003
the anterior cranial base, thus separating the cranial cavity from the nasal cavity. The periorbita is completely freed circumferentially around each globe. Using an osteotome, the lateral osteotomies are performed anterior to the zygoma, as approached from the bicoronal incision. This osteotomy is continued via the lower lid incision. In a 4-year-old girl, it is important to keep the osteotomy line above the infraorbital foramen on each side to avoid destroying future tooth buds. The lower osteotomies are continued until they meet the medial osteotomies, which were performed previously (Figs. 14–4 and 14–5). Because the right superior orbital rim was 8 mm lower than the left in our patient, an 8 mm segment of bone is now removed from the superior aspect of the right orbit to allow a superiorly directed repositioning of the right eye (Fig. 14–4). The osteotomy within the bony orbit is done circumferentially for a 360 degree cut, ~2 cm in from the orbital rim (Fig. 14–5). An assistant holds a malleable retractor to protect and retract the globe. An osteotome is placed in the inferior lid incision to perform the inferior and lower medial and lateral wall osteotomies. The orbital roof and upper medial and lateral orbital walls are divided through an intracranial approach with an assistant placing gentle retraction on the
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Figure 14–4 Artistic reconstruction showing the osteotomy lines and resection of the midline nasal complex and sinuses. 10.1055/978-1-60406-039-3c014_f004
frontal lobe and another protecting and retracting the globe with a malleable retractor (Fig. 14–5). A completed osteotomy is then confirmed using a 2 mm osteotome. Medial canthopexies are performed by first identifying the medial canthal ligaments, passing a 26 gauge wire through them, and then repositioning them through a new hole that is drilled posterior and superior to the lacrimal crest (Fig. 14–6). The wires are passed through these holes and then anteriorly over the medial orbital wall. The wires are tied together, bringing the orbits toward the midline. In addition, the right orbit is repositioned superiorly by 8 mm. These bone units are secured to the bandeau using microplates. Using Joseph scissors, the overlying nasal skin is separated from the underlying upper and lower lateral nasal cartilages, creating a pocket for a cantilever bone graft. The
cantilever bone graft consists of a full-thickness piece of calvarial bone, 8 mm wide and 5 cm long. The bone graft is then placed in the created nasal pocket and is secured in place using a microplate to the bandeau. This cantilever technique stabilizes the bone graft to improve the previously flat appearance of the nose. The distance between the medial orbital walls now measures 15 mm. We usually overcorrect the medial approximation of the orbital walls because the orbits tend to drift laterally with time. The pericranial flap is then reflected between the nasal and cranial cavities. The frontal bone plate is replaced and secured into position using microplates. The temporalis muscles are then rotated anteriorly and sutured in place using Vicryl sutures placed through holes in the microplates or through drill holes made in the bandeau and frontal bone.
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10.1055/978-1-60406-039-3c014_f005 Figure 14–5 Artistic reconstruction outlining the osteotomy lines along the orbital walls.
Closure Prior to closure it is extremely important to check for any CSF leaks. Undetected leaks can hinder postoperative recovery. The critical area for examination is around the cribriform plate region. Any dural tears during the craniotomy have to be repaired. We often have the anesthesiologist perform an extended Valsalva maneuver to look for a CSF leak. Closure of the bicoronal scalp incision is performed after copious irrigation with saline solution and meticulous hemostasis. Debris commonly collects beneath the scalp flap. These areas must be irrigated out thoroughly because
they are a potential source of infection. A drain is attached to light suction for 48 hours. Scalp closure is a standard two-layer closure with approximation of the galeal and skin layers. The lower eyelid incisions are closed in a single layer using a 5–0 or 6–0 nylon suture. The excess nasal skin is then removed along the prior inverted V incision (after a V-Y lengthening of the right side of the nose in the present case) (Fig. 14–3). This incision is closed in two layers. The tarsorrhaphy sutures are removed. The pupils are checked and the eyes irrigated with a balanced salt solution. Lacri-Lube (Allergan, Irvine, CA) is then placed in each eye.
14 Orbital Hypertelorism and Orbital Dystopia
Figure 14–6 Artistic reconstruction showing the bone units repositioned. Bone grafts have been placed laterally, to the side of each orbit. Because the right orbit had to be moved superiorly, a graft was placed in
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the defect inferior to the orbit. The medial canthal ligaments have been reattached in this schematic.
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Postoperative Management Including Possible Complications The patient is continued on antibiotics (selected to cover both skin and nasal flora) far 5 days postoperatively because the nasal cavity was entered, which increases the risk of infection. There is always significant periorbital swelling postoperatively as well as strabismus. The patient and family should be forewarned of this in the preoperative counseling sessions. In most patients the strabismus corrects to its original pattern. Any surgical correction of a postopera-
tive strabismus should be delayed for at least 6 months, and preferably for 1 year. CSF leakage, meningitis, mucocele formation, bone graft loss, epiphora from duct obstruction, visual loss, and death have all been reported with these types of complex craniofacial repairs. With proper attention to detail, such complications can be reduced to the very minimum. As mentioned above, dural tears must be repaired meticulously during the operation. The use of the pericranial flap to separate the nasal and cranial contents is also important in reducing the incidence of infection. These patients must be followed for the delayed development of mucoceles and meningitis.
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A
B Figure 14–7 (A) Frontal view of a child with hypertelorism prior to surgery; (B) 8 months after surgery.
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Patients undergoing canthopexies have the potential to develop lateral drifting of the medial canthopexies and may require later secondary revisions.
Clinical Case This 5-year-old child presents for orbital hypertelorism correction (Fig. 14–7A). Several alternative techniques are presented in this patient’s surgery. She underwent correction of bifid nasal tip previously with open rhinoplasty and unification of the domes of the lower lateral cartilages. Occasionally, silicone tubes may be inserted in the lacrimal punctae at the time of surgery if osteotomies were to interrupt the
A
nasolacrimal drainage. No midline forehead-glabelar incision was planned, as the brow position can be modified later with medial microplug hair grafting and lateral trimming. A zig-zag or wavy coronal incision was made in the scalp, followed by subperiosteal dissection to the superior orbital rim. Laterally, the superficial layer of the deep temporal fascia was entered at the level of the frontozygomatic suture to reach the zygomatic arch, to avoid injury to the frontal branch. Anteriorly, subperiosteal dissection was continued centrally caudal to the nasal bones. Care was taken to preserve the medial canthal attachments. Frontal craniotomies were performed without leaving an intact frontal bandeau, which facilitates osteomies in the anterior cranial fossa. The olfactory nerve is preserved whenever possible. The
B
Figure 14–8 (A) Three-dimensional computed tomography scan before surgery; (B) 8 months after surgery. 10.1055/978-1-60406-039-3c014_f008
14 Orbital Hypertelorism and Orbital Dystopia orbital osteotomies were performed as described except the osteomy at the infraorbital rim was performed from the coronal incision; therefore, a lower lid incision was not necessary. After medial translocation and fixation of the bony orbits with resorbable plates, a cantilever bone graft was placed on the nasal bridge. The integrity of the medial canthal tendon is checked, and if it is interrupted, then reattachment is performed. A pericranial flap was placed in the floor of the anterior cranial fossa to isolate the nasal cavity. Finally, at the conclusion of the procedure, paranasal bolster dressing was applied using trasnasal sutures. The bolster consists of inner Xeroform (Kendall Company, Mansfield, Massachusetts) and outer rigid support, such as aluminum plates. We believe that this step is important to reestablish the unique topography of the naso-orbital valley. Photo-
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graphs (Fig. 14–7) and CT scans (Fig. 14–8) demonstrate pre- and postoperative findings. Acknowledgment This chapter is a revision of the chapter, “Correction of Orbital Hypertelorism and Orbital Dystopia” by Constance M. Barone, M.D., Ravelo Argamaso, M.D., David F. Jimenez, M.D., and James T. Goodrich, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 2, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Ravelo Argamaso, M.D., for his help and efforts on the original chapter published in the first edition of this work.
15 Closure of the Myelomeningocele David G. McLone
Repair of the myelomeningocele in a newborn is relatively straightforward and based upon an understanding of the developmental anatomy of neurulation and what has gone wrong. Preservation of neurological function, detection of associated anomalies, and prevention of postoperative complications are the essential aims of this procedure. Pre-operative concerns include preparation of the infant for surgery and informing the family of the risks and advantages of surgery as well as what the future likely holds for the child.
Patient Selection Fortunately, prenatal ultrasound and serum AFP have allowed time for a decision about the future of the pregnancy and, if the pregnancy is going to term, time for the family to prepare for the birth of a child with a neural tube defect. When the birth of a child with a neural tube defect is a surprise, it is important for the parents to have some time to grapple with the many new issues facing them. It is equally important to proceed with definitive treatment in a timely fashion. Fortunately, most parents today are aware that the child will be born with spina bifida and have had prior counseling. Unless the newborn is critically ill, repair of the myelomeningocele should proceed. Significant delays increase both morbidity and mortality. Early closure of the myelomeningocele remains an important part of initial management. Although studies have not documented any increase in the deficits in the survivors of briefly delayed closure, our experience with patients transferred late and requiring delayed closure in the face of infection has been a decrease in motor function in some and an increased rate of ventriculitis (37%), as compared with that in patients with early closure (7%). The natural history of unrepaired newborns who are fed but denied antibiotics would indicate that 40 to 60% will survive, often much more significantly impaired. If antibiotics are added to the care of the unrepaired children, the mortality and morbidity fall to levels similar to those of neonates repaired in the first 24 hours. Optimally, we operate on the neonate soon after birth, preferably in the first few postnatal days. Prenatal diagnosis makes this increasingly more possible. The opera-
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tion may safely be deferred for up to 72 hours without an increase in complications. This delay is particularly important for the unstable or critically ill newborns. These babies can usually be stabilized within 72 hours, and this time is usually well spent. A search for coexistent anomalies of other organ systems should be undertaken during this time. Severe anomalies or absence of vital organs or unrepairable cardiac defects may portend a poor outcome. Renal anomalies are common but not usually life-threatening. Although the neonate may not produce significant amounts of urine during the first 24 hours, the presence of urine in the bladder implies the presence of functioning kidneys. Ultrasonography can delineate most major renal anomalies. Syndromes related to chromosomal anomalies may not be obvious upon initial inspection but should be sought out. Although most coexisting anomalies are not immediately life-threatening and may be dealt with without much difficulty, it is important to remember that a few newborns with myelomeningocele may have potentially fatal associated malformations and may not be saved. Intervention to prolong the lives of these infants in the setting of a dismal outlook makes little sense. They should be kept comfortable, and their families should be supported.
Preoperative Preparation The preparation of the neonate with a myelomeningocele for surgery is usually not difficult. Most have a high hematocrit and an adequate intravascular volume, and fluid resuscitation is therefore usually not necessary. Common perioperative complications include hypothermia and hypoglycemia, both of which are easily prevented through the judicious use of heating and monitoring of serum glucose. The placode may become desiccated with prolonged exposure to the air and should therefore be protected. Covering the placode with sterile, saline-soaked gauze is preferable. The dressing may be covered with plastic wrap to prevent rapid evaporation of the saline. Substances that are toxic to tissues and result in inhibition and delay of wound healing should not be used directly on the malformation. The use of perioperative antibiotics is left to the discretion of the surgeon. We have tended to use them.
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Closure of the Myelomeningocele
Operative Procedure
Missed Abnormalities
Preservation of Neurological Function
Split Cord (Diastematomyelia)
Preservation of Neural Tissue Prior to closure, the infant should be kept on his or her abdomen to reduce mechanical trauma to the neural tissue. During the subsequent surgical repair, great care must be taken to avoid drying, traction on neural elements, irrigation with hot saline, and excessive use of electrocautery. With magnification and microinstrumentation, the opening of significant blood vessels can be avoided. Occasionally, the entire closure can be performed without cautery. It has clearly been shown that the exposed neural tissue is functional. Movement of muscles subserved by spinal cord segments involved in the placode as well as the presence of somatosensory evoked potentials conducted through the placode both point to the functional nature of this tissue. Even when the initial examination fails to demonstrate movement of muscles innervated by the placode, the placode should still be considered functional because more than one third of these patients subsequently gain motor functions not previously detected. Therefore, all neural tissue must be preserved.
Preservation of Vascular Supply Preservation of the vascular supply to the placode is essential if this tissue is to survive. Unlike the normal spinal cord, the blood supply to the placode does not enter exclusively through the vertebral foramina along the nerve roots. Many large vessels pass directly through the laterally reflected dura mater and supply the myelomeningocele. Those supplying the junction between the neurulated spinal cord and the placode seem to be at greatest risk. Rarely is it possible to preserve all of these vessels, and, fortunately, they can sometimes be sacrificed if necessary without apparent injury to the placode. Nonetheless, great care must be exercised to preserve these vessels while mobilizing the dura for closure (Fig. 15–1A).
Inclusion Dermoid Great care should be exercised in separating the edge of the placode from the contiguous cutaneous epithelium (Figs. 15–2A and 15–2B). Some pearls of epidermoid tumors may already reside within the placode. Retained fragments, possibly even a single cell, could, if imbricated within the closure, produce an inclusion epidermoid tumor (Figs. 15–3A and 15–3B). These inclusion dermoids produce not only tumors but associated desquamation debris, which may also stimulate an intense arachnoiditis. Later in the child’s life, a tethered cord release in the face of the scar produced by this inflammatory process can be extremely difficult.
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Both the rostral and caudal ends of the closure site should be closely inspected prior to the closure of the placode to identify associated tethering, bony spurs, or fibrous bands. Cranially, removal of an additional lamina may be necessary to adequately visualize the adjacent spinal cord (Figs. 15–3C and 15–4). Hemimyelomeningoceles may also be readily visualized by examining the adjacent spinal cord. The presence of an asymmetrical neurological deficit preoperatively should alert the surgeon to the possibility of a hemimyelomeningocele or an associated split cord malformation.
Thickened Filum Terminale Caudal to the placode a thickened filum terminale may often be present (Figs. 15–1B, 15–5A, and 15–6A). This should be sectioned if present. Spinal cord tethering in these patients may result as much from a missed thickened filum as from adhesions to the placode.
Anatomical Reconstruction The “different types” of myelomeningocele are best understood in terms of an archetypal anatomical deformity and variation about that archetype. The basic deformity consists of an open neural placode, which represents the embryologic form of the caudal end of the spinal cord prior to neurulation (Fig. 15–5A—15–5C). A narrow groove passes down the placode in the midline. This represents the primitive ventral sulcus, and it is directly continuous with the central canal of the closed spinal cord above (and occasionally below) the neural placode. Cerebrospinal fluid passes down the central canal of the spinal cord and discharges from a small pit at the upper end of the placode to bathe the external surface of the exposed neural tissue. This fluid does not indicate rupture of subarachnoid space ventral to the myelomeningocele. The size of the sac on the baby’s back at the time of birth is dependent upon the amount of spinal fluid that is collected ventral to the neural placode. The majority of lesions will be flush with the baby’s back. A smaller number of placodes are raised far above the surface of the back by marked expansion of the subarachnoid space. Generally, however, both types are grouped under the myelomeningocele heading. In most cases, the spinal cord rostral to the neural placode is normal in gross form. Anomalies such as split cord and absence of a segment of the spinal cord can exist above the neural placode, however. Concurrent arteriovenous malformations and lipomas of the spinal cord are also possible. Occasionally, the neural placode is in a totally disorganized state. In these cases, the neural placode appears to have undergone intrauterine infarction so that portions of it are severely dysplastic and reduced to a simple membrane. This would support the concept that myelomeningocele is indeed a progressive intrauterine disease.
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Figure 15–1 (A) Vessels entering the placode (arrows) are preserved during reconstruction of the neural tube. (B) A drawing shows the free edges of the dura being held open as the neural tube is reconstructed. The arrow indicates the point where the thickened filum was cut. (C) A 10.1055/978-1-60406-039-3c015_f001
photograph showing the beginning of reconstruction of the neural tube at the rostral portion of the myelomeningocele. (D) The epidural space lateral to the neural tissue is opened; it is important not to carry this dissection ventral to the neural tissue.
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Figure 15–2 (A) A drawing shows the incision being made at the junction of normal and abnormal thin skin. (B) A photograph at surgery shows the abnormal thin skin being cut free at the junction (arrows) of the abnormal skin and the placode. 10.1055/978-1-60406-039-3c015_f002
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Figure 15–3 (A,B) Intraoperative photographs show inclusion dermoid tumors with marked arachnoiditis. (C) Photograph shows a split cord malformation (arrows) proximal to the myelomeningocele.
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Figure 15–4 A contrast computed tomography scan shows a hemimyelomeningocele, a split cord malformation; the hemi cord on the left had a myelomeningocele. 10.1055/978-1-60406-039-3c015_f004
Figure 15–5 (A) A terminal myelomeningocele; the arrow indicates the area of a thickened filum terminale. (B) A larger myelomeningocele shows the ventral sulcus in the midline and the arrow indicates the entrance to the central canal of the adjacent normal cord. (C) An infant with a large thoracolumbar myelomeningocele and a kyphotic deformity at the junction of the thoracic and lumbar spines. 10.1055/978-1-60406-039-3c015_f005
The functional motor and sensory levels are related to but not always consistent with the anatomical level of the lesion. Often, function is preserved below the anatomical segments involved. Again, functional asymmetry occurs and should raise the question of an additional lesion such as a split cord. The normal anatomical structures derived from the neural tube are almost always present but are open in the midsagittal plane (unneurulated), and the dorsal roots are therefore displaced laterally. Because the neural crest is usually involved in the defective neurulation, the dorsal roots are often attenuated or absent. The exposed neural surface is the ependymal surface of the neural placode and is continuous with the central canal of the spinal cord rostrally. The lateral edges of the neural tissue are developmentally the alar (sensory) plate with the dorsal root entry zones at the lateral edge. The medial portion of the placode is basal (motor) plate and contains the anterior motor horns. Ventral to the placode along either side of the midline the motor roots exist from the placode. The sensory roots enter the cord at the periphery of the placode lateral to the motor roots. The dorsal root ganglions are usually reduced or absent, so the dorsal roots are small or absent. The ventral surface of the placode is covered with pia-arachnoid, which is directly contiguous with the arachnoid membrane of the sac. The sac usually encloses an intact subarachnoid space. An understanding of this anatomy is essential to reconstituting the spinal cord and its coverings. Dissection of the myelomeningocele begins at the junction of the abnormal covering epithelium and the normal skin near the rostral end of the placode (Figs. 15–2A and 15–2B). This junction should be incised around the entire circumference of the myelomeningocele. Once this has been completed, the dissection is carried toward the neural placode. Dividing the epithelial junction from the neural tissue requires care because on the one hand, this is the region where dorsal roots and segmental vasculature enter the neural placode, and on the other hand, any residual skin elements may grow to become inclusive epidermoid tumors (Figs. 15–3A and 15–3B). The use of magnification enables one to dissect free any nerve roots that are adherent to surrounding tissues. When this has been completed, the neural tissue may float freely on an arachnoid enclosed sac of cerebrospinal fluid. Once the neural tissue is freed, every attempt should be made during anatomical reconstruction of the spinal cord to prevent later retethering of the placode. Although pial-to-pial closure of the placode into a tubular structure has not completely prevented retethering, it may reduce the incidence of this complication (Figs. 15–1B and 15–1C). More importantly, it makes untethering of the spinal cord later considerably easier to perform. The reapproximated neural tube is usually adherent only along the dorsal closure line (Figs. 15–7A—15–7D). In contrast, leaving the placode open allows the unclosed neural tissue to become densely adherent over the entire exposed ependymal area of the placode; the laterally displaced dorsal roots are usually caught in the scar and require tedious dissection to free them (Figs. 15–7E—15–7G). The central canal is reconstructed throughout its entire length so that the neural placode becomes a tube. Closing
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fascia allows the skin to be mobilized to aid closure. (C) A drawing shows closure of the skin.
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Figure 15–7 (A–D) A contrast computed tomography (CT) myelogram shows a reconstructed neural tube that has retethered along the suture line to the overlying dural closure. (F–G) Contrast CT myelograms show10.1055/978-1-60406-039-3c015
the neural placode into a neural tube and folding the arachnoid sac around the tube encloses the cord within an envelope of cerebrospinal fluid. By suspending the closed neural tube in an intact cerebrospinal fluid compartment, we hope to decrease the possibility of scarring and adherent neural elements that might later result in tethering of the spinal cord as the child grows. Magnetic resonance imaging has become the imaging modality of choice, and a postoperative study can demonstrate the reconstructed neural tube (Figs. 15–8A—15–8D), but not as clearly as a contrast computed tomography myelogram. The open edges of the dura mater attach to the underside of the skin lateral to open skin edge. To ensure adequate dura mater for closure, the most lateral extent of the dura must be found and detached at that point (Fig. 15–1B). No dissection in the epidural space ventral to the neural tissue should be attempted (Fig. 15–1D). The dura is usually very thin under the spinal cord, and if torn is difficult to repair. During dural closure, the neural tissue may become included in the suture. Therefore, care should be taken to avoid this preventable complication. Once the dura mater is free, it is closed in the midline. This layer should be closed “watertight” if possible. We prefer a running locked nonabsorbable suture of 5 or 7–0 (Fig. 15–6A). The dural closure must not constrict the underlying neural elements or interfere with the blood supply to the reconstructed cord. Potential recovery may be lost to ischemia or infarction if dural or fascial coverings constrict the underlying tissues. Mobilization and midline approximation of lateral para spinal muscle fascia are optional and not essential (Fig. 15– 6B). It may not be easy to obtain significant lateral tissues. Muscle closure at the lumbosacral level is often difficult
ing neural placodes adherent to the overlying dural closure. (H) A contrast CT myelogram showing a free-floating reconstructed neural tube.
because the fascia of sacrum and ileum are densely adherent to the bones. Thoracic and upper lumbar myelomeningoceles can be difficult to repair if associated with a kyphotic deformity (Fig. 15–5C). To allow skin closure without compression may require a kyphectomy. It has the benefits of making the closure easier, giving the patient a flat back, and converting muscles from flexors of the spine to extensors, which prevents progression of the deformity. Closure of the skin should be performed in the midsagittal plane whenever possible. Future untetherings or orthopedic procedures will be facilitated by a simple midline closure (Fig. 15–6C). Mobilization of the skin should also include the subcutaneous fat layer because the vascular supply to the skin comes through this layer. Blunt dissection in the plane between the muscle and subcutaneous fat is the best method to preserve the blood supply (Fig. 15–6B). Some consideration of cosmesis should be given here, but this is not a major consideration if it poses any added stress to neural tissue.
Hydrocephalus The timing of shunt placement is a matter of some debate. Approximately 20 to 30% of patients with myelomeningoceles do not need a shunt, and therefore we have advocated delaying a shunt procedure until well after the initial closure. In the presence of obvious severe hydrocephalus at birth, however, it would seem to make little sense to delay and subject the patient to a second anesthetic. Placement of the shunt at the time of initial closure in these cases is safe and reduces the risk of cerebrospinal fluid leakage or wound breakdown postoperatively.
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Figure 15–8 (A–D) Four neonates with myelomeningoceles. Postoperative magnetic resonance imaging axial T2 scans show the reconstructed neural tubes. 10.1055/978-1-60406-039-3c015
Postoperative Management Management of the Closure Site A variety of techniques have been employed to protect the closure site postoperatively, including placing the patient prone or suspending the patient from a sling. These maneuvers are of little value. We simply place the patient in a bassinet postoperatively and allow him or her to be held in the mother’s arms without restrictions. We have not encountered any significant problems using this regimen.
Care of the Patient At present, the patient is given intravenous fluids with 10% dextrose for the first 24 hours and then is given to the
mother for feeding. Daily inspection of the closure is recommended for signs of infection, separation of the skin edges, or leakage of cerebrospinal fluid. During the hospital stay, instruction is given to the parents to prepare them for caring for the baby in the home. This is the ideal time for the parents to become familiar with the team that will assist them in the care of the baby as an outpatient. It is essential that the parents gain confidence in their own ability to care for the baby and are aware that the team is always available for support.
16 Dandy-Walker Malformation Arthur E. Marlin and Sarah J. Gaskill
The Dandy-Walker malformation is a congenital anomaly of the posterior fossa composing 7% of cases of congenital hydrocephalus. This entity (Fig. 16–1) was first described in 1911, although Dandy’s original case of a 13-month-old with occlusions of the foramina of Magendie and Luschka was not published until 1914. The term Dandy-Walker syndrome (DWS) was introduced by Banda in 1954. The malformation consists of: (1) defective development of the cerebellar vermis; (2) cystic enlargement of the fourth ventricle; (3) hydrocephalus; (4) enlarged posterior fossa; (5) elevated transverse sinuses; and (6) obstruction of the outlets of the foramina of Magendie and Luschka (not seen in all cases). The pathogenesis is unknown. Some cases are suggestive that the enlarged fourth ventricle causes secondary aqueductal stenosis and dilatation of the lateral and third ventricles.
Treatment via Shunt Placement Although attempts at early re-establishment of the patency of the outlets of the fourth ventricle have been made, the mainstay of treatment is cerebrospinal fluid (CSF) diversion. Three options exist for ventricular shunt placement: (1) fourth ventricle; (2) lateral ventricle; and (3) both. The distal catheter is usually placed in the peritoneal cavity. If there are contraindications to peritoneal placement, such as peritonitis or multiple adhesions, the right atrium can be used. The “correct” type of diversion has been a controversial issue, with advocates and opponents for each option. A fourth ventricular shunt, especially early in the course of the disorder, may be all that is necessary, according to its advocates. However, if secondary aqueductal stenosis has occurred or there is not free communication between the supratentorial and infratentorial ventricular systems, this will not decompress the lateral ventricles and downward herniation can occur. The same type of argument exists for a lateral ventricular shunt; the posterior fossa cyst may not be adequately decompressed and upward herniation can occur. Preoperatively, ventricular communication can be assessed by radionuclide ventriculography or computed tomography (CT) positive contrast ventriculography. Recently there have been case reports of endoscopic third ventriculostomy with shunting of the fourth ventricle and even endoscopic third ventriculostomy and placement of an aqueductal stent.
The authors prefer a fourth and lateral ventriculoperitoneal shunt in DWS with panventricular enlargement. Two ventricular (lateral and fourth ventricle) catheters are connected proximally to a valve with a three-way connector and then to the peritoneal catheter (Fig. 16–2). This allows equalization of pressures between the intracranial compartments.
Selecting Shunt Equipment An extensive variety of shunt systems is available, suggesting that no ideal system exists. The authors prefer straight ventricular catheters, a proximal valve with a reservoir (to allow access for CSF sampling), and a peritoneal catheter with a distal open end and three series of side slits just proximal to the ending (offering no resistance). The selection of valve pressure is another area of controversy. In general, a low-pressure valve is appropriate for infants. Higher pressure valves should be used when the calvarium is closed. Variable resistance valves can also be used.
Patient Selection Patients usually present at birth or shortly thereafter. Not infrequently the diagnosis can be made prenatally by ultrasonography. Symptoms are referable to increased intracranial pressure. Macrocephaly at birth or, later, a rapidly enlarging head with a circumference crossing growth percentile lines, irritability, and vomiting are the usual modes of presentation. Examination reveals macrocephaly with a bulging fontanelle, suture diastasis, and, often, engorged scalp veins. The posterior fossa is commonly large and occipital transillumination is positive. The diagnosis can be made by ultrasonography, CT, or magnetic resonance imaging (MRI) (Fig. 16–3). CT and MRI are definitive.
Preoperative Preparation The issue of prophylactic antibiotics is unresolved for lack of a large, properly designed series. The authors use prophylactic anticoagulase-negative Staphylococcus agents based on recent hospital sensitivities. These are given just prior to the surgical incision. Vancomycin is not used in situations of increased intracranial pressure because of its potential
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Figure 16–1 An artist’s depiction of the Dandy-Walker malformation in the midsagittal plane. 10.1055/978-1-60406-039-3c016_f001
histamine release and the possibility of causing further increases in intracranial pressure. Attention to detail in the operating room is mandatory. Operating room personnel should be aware that infection is the most serious complication of any shunting procedure. Traffic in the operating room should be kept to a minimum once the instruments are open. Only necessary personnel should be present in the operating suite in an effort to keep airborne particles to a minimum. Movement within the operating room should also be kept to a minimum. If no intravenous access is present, an inhalational agent is given by mask until this is obtained. Anesthesia is accomplished after thiopental induction and endotracheal intubation with fentanyl and Versed (midazolam), or rectal Brevital (methohexial). A short-acting, nondepolarizing muscle relaxant such as mivacurium can be used for intubation.
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Operative Procedure Patient Positioning The patient is positioned supine with the head turned laterally (to the left for a right-sided shunt). A roll is placed under the shoulders. The size of the roll depends on the size of the patient and the head. The roll is placed so that the posterior auricular region, neck, thorax, and abdomen are on the same plane to ensure an easy pass of the shunt passer. If the head is very large, the body may need to be elevated with towels to accomplish this (Fig. 16–4). The head should be positioned at the edge of the table close to the surgeon. The patient’s bladder is emptied by a Credé maneuver to minimize the risk of bladder perforation during peritoneal catheter placement.
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Figure 16–2 Operative shunt positioning. 10.1055/978-1-60406-039-3c016_f002
Surgical Technique The landmarks for the lateral ventricle are identified. The cranium should be perforated supratentorially 4 to 6 cm above the inion and 2.5 to 4 cm lateral to the midline. The line from the projection of the anterior fontanelle (~1.5 cm above the eyebrow) is determined to establish the trajectory of the lateral ventricular catheter. As these landmarks will be obscured by the surgical drapes, external guidelines in the room can be used to ensure the proper trajectory. Enough hair is shaved to allow an adequate border for draping. A curvilinear incision is marked with an inferior limb of sufficient length to allow for a fourth ventricular catheter (Fig. 16–4). The skin is to be reflected laterally so that the shunt apparatus is not directly under the incision. A paraumbili-
cal incision is also marked. At this time, the length of the lateral ventricular catheter should be determined. The tip should be anterior to the choroid plexus; thus, the external landmark is anterior to the coronal suture. Thorough skin preparation is essential. This is accomplished by a 10 minute preparation with providone-iodine soap and solution followed by Betadine gel. Before draping, landmarks are again noted. Sterile towels are applied in a fashion to allow minimal skin exposure. Excess gel is removed with sponges and an Ioban-impregnated barrier drape is applied to hold the towels in place. Liquid-impenetrable drapes are then used to complete the draping of the field. We use the surgical isolation bubble if available. This is placed over the patient and the operative procedure is per-
Figure 16–3 (A) Sagittal and (B) axial magnetic resonance imaging views (T1-weighted images) of a patient with a Dandy-Walker malformation. 10.1055/978-1-60406-039-3c016_f003
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Figure 16–4 Patient positioning showing skin incisions (dashed lines). 10.1055/978-1-60406-039-3c016_f004
formed within the bubble (Fig. 16–5). All necessary instruments and supplies are also placed in the bubble. The shunt components (doubly wrapped) are kept in their second wrapper until inside the bubble, where they are opened and left to soak in a bacitracin solution until placement. If the bubble is not used, the shunt equipment is not opened until draping is complete. The three-way connector is attached with a double 3–0 silk tie to the flushing device (Fig. 16–6). The cranial incision is made first. Hemostasis is obtained with bipolar coagulation. A subcutaneous pocket is made with blunt dissection caudal to the area of the bur hole to house the flushing device. Some medial subcutaneous dissection is also done for the three-way connector and ventricular catheters. Retraction is accomplished with a small
self-retaining retractor that is also hemostatic. The calvarium is perforated supratentorially. The suboccipital muscles are split and the occipital squama identified. A twist drill hole is placed and enlarged with a rongeur so the dura is well visualized. In the newborn or young infant the dura may have extensive venous lakes. It can also appear bluish because of the underlying cyst. It is thus aspirated with a 22 gauge needle to ensure that there is not a venous lake. If no area can be found without blood return, a 4–0 silk purse-string suture is placed (Fig. 16–7). When placing the stitch, it is important to penetrate both leaves of the dura. The cranial incision is covered with bacitracin-soaked gauze while the paraumbilical incision is made. The shunt
Figure 16–5 The surgical isolation bubble. 10.1055/978-1-60406-039-3c016_f005
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Figure 16–6 A detailed depiction of the shunt connections. 10.1055/978-1-60406-039-3c016_f006
tube passer is then tunneled from the abdomen to the cranial incision so the distal tube can be passed from the cranium to the abdomen. Although this can be done in either direction, tunneling the passer from the abdomen to the cranium has less risk of penetrating the pleural space. The distal tubing is connected to the flushing device. The flushing device is seated in the subcutaneous pocket without kinks. The supratentorial dura is coagulated and a small opening is made with a no. 11 blade. The ventricular catheter on a stylet is passed and CSF is taken for culture, cell count, and glucose and protein determinations. The proper length of catheter should be determined preoperatively so that it will be anterior to the coronal suture and thus anterior to the choroid plexus. A good flow of CSF should be obtained and the catheter connected to one limb of the three-way connector with a double-tied 3–0 silk suture. Next, a small hole is made in the dura of the posterior fossa in the manner described above. The ventricular catheter is passed in ~3 to 4 cm; again, a good flow of CSF should
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be obtained. The surgeon should be careful to avoid placing the catheter so far into the cyst that it impinges on the brain stem. Cerebellar reconstitution is unlikely to occur, so the catheter need not be placed in a precise location within the cyst. The catheter here is secured gently to the muscle with a 3–0 absorbable suture to prevent kinking. A gentle curve is made with the tubing subcutaneously and it is brought rostrally to be secured to the remaining limb of the three-way connector, again with a double-tied 3–0 silk suture (Figs. 16–3 and Fig. 16–6). This region is now covered with a bacitracin-soaked gauze. Attention is turned to the abdominal incision. The peritoneal catheter should be draining CSF spontaneously. Not infrequently, the distal catheter will need to be aspirated with a blunt needle to remove an air lock and ensure spontaneous flow. If there are no contraindications such as previous abdominal surgery, peritonitis, or an enlarged or surgically augmented bladder, a trocar is placed through the rectus sheath into the peritoneal cavity, directed medially toward
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Figure 16–7 Placement of the ventricular catheter through a dural venous lake. 10.1055/978-1-60406-039-3c016_f007
the umbilicus. Simultaneously with trocar placement, the anesthesiologist gives the patient a Valsalva maneuver. The catheter is passed through the trocar. A full length (90 cm) of peritoneal catheter is placed as there are no associated complications, and the need for an elective shunt lengthening is eliminated. If the use of the trocar is contraindicated, then the rectus sheath is split. The peritoneum is identified and a small opening is made; the surgeon takes care to lift the peritoneum away from the underlying bowel. After function of the shunt catheter is confirmed by spontaneous flow of CSF, it is placed into the peritoneal cavity under direct vision. The rectus sheath is closed with absorbable sutures.
Postoperative Management Including Possible Complications In an infant, the head of the bed is elevated 30 degrees and feedings are begun as soon as bowel sounds are audible. In a child with a fixed cranium and very large ventricles (i.e., a small cortical mantle), the head of the bed is kept flat for the first postoperative night and then is elevated progressively. In this situation a variable resistance valve or antisiphon valve such as a Delta valve can be used and the patient mobilized the first postoperative day.
Complications Skin Closure Wounds are now copiously irrigated with a bacitracin solution, 100,000 units in 500 ml of normal saline. The subcutaneous tissue of the abdomen and the galea of the scalp are closed with 3–0 or 4–0 absorbable sutures. The skin is closed with a subcuticular stitch of 4–0 or 5–0 absorbable sutures and Steri-Strips.
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Volumes can be written on shunt complications, but with meticulous technique and attention to detail these should be minimal. Infection rates should not be more than 8% and may approach 1 to 2%. The treatment of infection involves sterilization of the CSF and, usually, shunt replacement. The postoperative x-ray films will forewarn of obstruction due to poor shunt positioning.
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110 Pediatric Neurosurgery CSF leakage around the cranial catheter can occur because of a lack of cortical mantle to seal the dural opening around the catheter or because of too large an opening. If this is not eliminated by head elevation, a bur-hole type device or Rickham reservoir may need to be placed instead of a straight ventricular catheter. Subdural effusions or hematomas are treated expectantly if asymptomatic.
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Intra-abdominal injury is rare. Intestinal perforation may present by shunt infection with gram-negative or multiple organisms. This can usually be treated by removing the catheter and treating the infection, followed by replacement of the shunt. Perforation of the bladder can be managed by catheter removal and Foley drainage of the bladder.
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17 Surgical Management of Chiari I Malformations and Syringomyelia Elizabeth C. Tyler-Kabara, Richard B. Morawetz, and W. Jerry Oakes This chapter outlines our approach to the adult patient with a Chiari I malformation and/or syringomyelia. As evidenced by the multiplicity of procedures used in the treatment of these patients, there is no proven optimal approach. In fact, there is no proof that a patient with an incidentally identified Chiari I malformation or syrinx is destined to become neurologically debilitated, because the natural history of this condition has never been described satisfactorily. It has become possible only in the era of magnetic resonance imaging (MRI) to elucidate the long-term efficacy of various surgical procedures in the treatment of Chiari I malformations and syringomyelia. Unfortunately, this information will not become available to us for another 5 to 15 years, and the follow-up of these patients can exceed the length of a single neurosurgeon’s career.
Patient Selection Abnormal neurological signs referable to a Chiari I malformation or syrinx, or progressive syrinx enlargement, on serial imaging studies are indications for surgical intervention. Weakness and dissociated sensory loss are commonly found in patients with syringomyelia, and bulbar signs often accompany syringobulbia. However, it is not uncommon to encounter patients with impressive abnormalities seen on imaging studies but without definite abnormal neurological signs (e.g., in a setting of pain following a work-related injury, or hemihypesthesia from head to toe, including the sacrum). In these cases a conservative approach could be adopted, with follow-up MRI studies at appropriate intervals. If the syrinx remains unchanged in size and the patient has not developed progressive neurological abnormalities, no intervention is indicated. Similarly, a period of observation is warranted for the patient with a Chiari I malformation who presents with headache alone. If the headache seems related to the Chiari I malformation, as evidenced by worsening with cough or Valsalva maneuver, we recommend surgical intervention but emphasize to the patient that the goal of surgical intervention is not to relieve the headache but to minimize any chance of neurological deterioration. Cine MRI may be helpful to identify patients with abnormal cerebrospinal fluid (CSF) flow at the craniocervical junction who are most likely to benefit from decompression.
In contrast, surgical intervention is warranted in patients with documented progressive syrinx enlargement, even in the absence of abnormal neurological signs, because these patients are at risk for development of progressive neurological dysfunction at a later date. At the other end of the spectrum, the potential benefits of surgical intervention in the wheelchair-bound, debilitated patient with syringomyelia must be weighed against the risk of acute respiratory failure and long-term ventilator dependence in the perioperative period. There are no proven guidelines to follow in the selection of surgical candidates in this setting.
Preoperative Preparation Preoperative assessment of these patients includes a computed tomography (CT) scan or MRI of the head to determine the presence or absence of hydrocephalus. Hydrocephalus, if present, should be treated by a shunting procedure prior to consideration of other surgical interventions. An MRI of the entire spinal cord should be obtained to assess the presence and/or extent of a syrinx. Electrophysiological studies are not routinely performed, because the results do not usually influence surgical decision making. It is important to emphasize that the goal of the procedure is to halt the progression of neurological signs and symptoms rather than to ameliorate the symptoms.
Operative Procedure Chiari I Malformation For the patient with a Chiari I malformation without syringomyelia, a suboccipital decompression and upper cervical laminectomy with a generous duraplasty are performed. No attempt is made to resect the tonsils, plug the obex, or shunt the fourth ventricle, because these interventions have not been demonstrated to improve results beyond those achieved by bony and dural decompression alone. The patient is positioned prone using a head pin fixation device. The neck is flexed and the head of bed is raised. Preoperative antibiotics are administered as anesthesia is induced. Fig. 17–1A illustrates the position of a vertical incision made from the inion to the mid-cervical region. The
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Figure 17–1 (A) Schematic of incision placement and bone work for operative exposure of a Chiari I malformation. (B) Operative exposure of a Chiari I malformation with the floor of the fourth ventricle exposed. 10.1055/978-1-60406-039-3c017_f001
paraspinous muscles are dissected using a subperiosteal technique (Fig. 17–1B). A suboccipital craniectomy and C-1 laminectomy are performed with an emphasis on achieving foramen magnum decompression rather than on a large lateral suboccipital craniectomy. The technique during this portion of the procedure should be quite gentle, as there is little subarachnoid space under the dura and there is risk of injury to the brain stem and upper cervical cord. A C-2 laminectomy may be performed to permit the decompression to be carried inferiorly, below the tonsils. Excessive laminectomies should be avoided to prevent the increased risk of postlaminectomy kyphosis. The dura is then opened in a vertical direction. The patient’s own pericranium may be used as a graft. Some surgeons prefer cadaveric or artificial dural substitutes. An elliptical graft is fashioned and sutured in place to provide a generous decompression of the cerebellar tonsils. The wound is closed in layers. We do not routinely image the patient in the immediate postoperative period unless there is an indication for the study. An occasional pseudomeningocele will develop but usually resolves. For the symptomatic patient with a Chiari I malformation and an associated syrinx, we perform the same procedure.
Syringomyelia For the patient with a large symptomatic syrinx that fails to respond to adequate craniocervical decompression, and for the management of posttraumatic syringomyelia, a syringoperitoneal shunting operation may be performed. Entrance into the syrinx in the midthoracic region is preferable so that any sensory deficit is localized to the chest wall. The
goal is to eliminate the pressure gradient across the wall of the syrinx and completely decompress it. The patient is placed in the lateral position with the left side down to allow access to the right upper quadrant of the peritoneal cavity (Fig. 17–2). A two-level laminectomy over the largest portion of the syrinx is performed. The dura is opened in a vertical fashion off the midline toward the side of the dorsal root entry zone to be entered. The proximal tip of a James peritoneal shunt is directed cephalad into the syrinx and a few of the drainage holes are also placed in the subarachnoid space, thereby creating a syringosubarachnoid as well as a syringoperitoneal shunt (Fig. 17–3). The dura is closed, and the shunt is secured to the dura using a purse-string suture. The distal portion of the shunt is tunneled subcutaneously to the abdominal wall and is placed in the peritoneal cavity.
Postoperative Management Including Possible Complications Follow-up MRI scans are obtained 6 months after operation to assess whether or not the syrinx has collapsed. Further intervention, however, is reserved only for the patient who worsens neurologically.
Difficult Cases Occasionally we are referred patients who have undergone one or more procedures for syringomyelia but who continue to deteriorate neurologically. In this setting, the imaging
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Figure 17–2 Positioning of a patient for a syringoperitoneal shunting operation. The location of the skin incision is shown as a dashed line. 10.1055/978-1-60406-039-3c017_f002
Figure 17–3 The proximal end of a syringosubarachnoid/syringoperitoneal shunt is being inserted into the syrinx. 10.1055/978-1-60406-039-3c017_f003
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Figure 17–4 Magnetic resonance imaging scan of a 33-year-old man with a previously treated multiloculated syrinx.
studies often demonstrate a persistent uncollapsed syrinx containing multiple loculations. In the patient with a Chiari I malformation who has undergone previous syringoperitoneal shunting, we believe that a craniocervical decompression is the next step. For the patient with a large syrinx but with no craniocervical abnormality, or in a patient who has previously undergone both shunting and craniocervical decompression, a craniocervical decompression is warranted. As a final option or in posttraumatic syringomyelia, a second syringoperitoneal shunt insertion, done with care to ensure syringosubarachnoid shunting, is performed. Caution is advised because potential damage to the spinal cord (particularly the dorsal columns) is high with repetitive shunt placements and with attempts to fenestrate syrinx loculations. Although septations in the syrinx are usually incomplete, occasionally a localized syrinx collapses without collapse of the more remote portion of the syrinx following a shunting operation. It is in this setting that treatment failure is usually seen. Fig. 17–4 illustrates the MRI of a 33-year-old male who had previously undergone two syringoperitoneal shunt placements for right hand weakness and numbness. His symptoms continued to progress, and MRI follow-up studies demonstrated that the cervical syrinx, which had multiple loculations, had increased. He subsequently underwent a suboccipital decompression and upper cervical duraplasty. Fig. 17–5 shows the continued presence of a large syrinx with septations despite multiple operative interventions.
Figure 17–5 Continued presence of a multiloculated syrinx despite multiple operations. 10.1055/978-1-60406-039-3c017_f005
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Conclusion The natural history of Chiari I malformations and syringomyelia is not fully understood, and the relative benefits of various treatment options remain unproven. We do not operate on asymptomatic patients unless imaging studies demonstrate a large or progressive syrinx enlargement, because there is no certain evidence that these patients are destined to develop a neurological abnormality. In the symptomatic patient with a Chiari I malformation, with or
without a syrinx, we perform a suboccipital decompression and upper cervical laminectomy with duraplasty. In patients who harbor a large persistent symptomatic or posttraumatic syrinx, a syringoperitoneal shunt is performed. Unfortunately, there exists a group of patients who present difficult management problems in that they continue to deteriorate neurologically despite surgical therapy. No uniformly satisfactory approach has been demonstrated for the treatment of these patients.
18 Split Cord Malformations Dachling Pang
Recently, Pang et al described a unified theory of embryogenesis that holds that all double spinal cord malformations arise from a common embryogenetic error: a failure of prospective notochordal cells to achieve midline integration following their ingress through Hensen’s node, allowing the simultaneously lengthening ectoderm and endoderm to form adhesions across this central fenestration in the notochord. The subsequent incorporation of multipotential mesoderm (mesenchyme) into this adhesion constitutes the endomesenchymal tract, which not only permanently bisects the notochord but also forces each overlying hemineural plate to neurulate against its own heminotochord in a severely compromised manner. The basic malformation, therefore, consists of two heminotochords and two hemineural plates separated by a midline tract containing ectoderm, mesenchyme, and endoderm. Further evolution of this basic form into the full-grown malformation depends on four factors: (1) the ability of the heminotochords and hemicords to achieve midline healing; (2) the interaction between each heminotochord and hemineural plate during neurulation; (3) the persistence of the endomesenmchymal tract; and (4) the developmental fates of the three germ elements. Variable healing of the notochord results in the spectrum of associated vertebral anomalies ranging from bifid vertebral bodies (“butterfly” vertebrae), to widened bodies with midline tracts, to plain widened bodies. Partial healing of the hemineural plates results in the so-called cleft cord, a single cord with double central canals and a deeply indented midsection. Abnormal neurulation of the hemineural plate, hinged to the cutaneous ectoderm on only one side and receiving mechanical and inductive influence from only one (lateral) set of paraxial mesoderm, results in a misshapened hemicord with unpredictable internal cytoarchitecture varying from four healthy gray horns to a single rudimentary gray column. Complete inability of one or both hemineural plates to neurulate, perhaps due to an untenable relationship with the heminotochord(s), results in an associated hemimyelocele or myelomeningocele, respectively. Persistence of the dorsal (ectodermal) portion of the endomesenchymal tract causes a patent dermal sinus tract to maintain continuity with the midline septum; the tract sometimes encysts to form a dermoid between the hemicords. Persistence of the ventral (endodermal) portion of the mesenchymal tract and its connection with the em-
bryonic gut explains the associations of split spinal cords with intestinal duplication and malrotation. Finally, and in some respects most importantly, the developmental fates of the germ elements within the midline endomesenchymal tract determine the state of the meningeal investment of the hemicords, the nature of the mature septum, the presence of ganglion cells and nerve roots bridging between a hemicord and the septum, the tethering of the hemicords to the dorsal dura by fibroneurovascular bands (myelomeningocele manqué), and the rare occurrence of an enterogenous (neurenteric) cyst in the midline cleft. Based on their proposed theory, Pang et al suggested replacing the terms diastematomyelia and diplomyelia (which would imply different embryogenetic mechanisms for the two types of double cord malformations) with the nomenclature split cord malformation (SCM). They introduced a new classification of double spinal cords founded on two easily identifiable features: the dural arrangements of the hemicords and the nature of the midline septum. If specialized mesodermal cells destined to form dura and neural arch (from the meninx primitiva), normally found in the region between the notochord and neural tube, are incorporated into the endomesenchymal tract, a median dural layer forms next to the medial aspect of the hemicord and joins the dura that normally grows around the lateral aspect of the hemicord to complete a separate dural tube for each hemicord. Additionally, in accordance with their sclerogenic function, the meninx primativa cells within the endomesenchymal tract facing away from the hemicords also form a midline bone spur between the two median dural walls, continuous with the bone of the developing vertebral centrum. This configuration, called type I SCM, therefore consists of two hemicords, each contained within its own dural tube, separated by a dura-sheathed rigid osseocartilaginous median septum. Inasmuch as the endomesenchymal tract frequently reaches the neural arches, the median bone spur bisects the spinal canal into two separate compartments. The spinal cord is transfixed solidly to the spinal canal by the bony and dural septa. The sclerogenic effect of the meninx primativa cells when these admix with cells of the developing neural arches accounts for the often massively hypertrophic fusion of several adjacent laminae at the level of a type I SCM (Fig. 18–1). In contrast, the endomesenchymal tract in a type II SCM does not recruit meninx primativa cells. A thin fibrous sep-
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A
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Figure 18–1 Type I SCM. (A) The typical features are depicted. (B) Axial view from computed tomographic myelogram showing a sagittal bony septum (BS), double dural sac, and hypertrophic neural arches.
tum, texturally different from dura, will form from the “ordinary” mesenchyme in the space between the hemicords. Here also, no arachnoid, bone, or cartilage will form. Both hemicords will lie within a single arachnoid and dural tube inside a noncompartmentalized spinal canal, separated by a fibrous rather than a rigid osseocartilaginous median septum (Fig. 18–2). However, this fibrous septum is always adherent to the medial aspect of the hemicords, and by virtue of its firm peripheral attachment to the ventral and/or
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dorsal dural wall, it is as real a tethering lesion as the bone spur of a type I SCM. The determining features of this classification do not overlap between the two types; there is never a type I SCM with dual dural sacs that does not have a rigid midline bone or cartilage within the median dural cleft, nor is there ever a type II SCM with a single dural sac but a naked piece of bone or cartilage unlined by dura. Typing is thus easily made with high-quality neuroimaging studies, an important pre-
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Figure 18–2 Type II SCM. (A )The typical features are depicted. (B) A midline filling defect just ventral to the hemicords, representing an axial view from a computed tomographic myelogram showing a single dural sac and a small ventral fibrous septum. 10.1055/978-1-60406-039-3c018_f002
operative step because the surgical techniques are different for each of the two types of SCM. The other commonly associated features of SCM such as paramedian nerve roots, myelomeningocele manqué, dermoids, dermal sinus tracts, centromedian blood vessels, thickened filums, and intestinal anomalies occur not only in both types of SCM but also in relatively similar frequencies.
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Patient Selection Thus, both types of SCM are tethering lesions. As with all other tethering lesions, the mere presence of an SCM in a child is sufficient indication for surgical release of the cord because neurologial deterioration is very common in these children, and because lost function is seldom reclaimable
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18 when treatment is rendered late. In both types of SCM, the operation aims at removing the median septum and all other associated bands, dermoids, lipomas, and enterogenous cysts that might be attaching or otherwise anchoring the hemicords to the surrounding dura. Unlike the obvious bony dural septum in a type I lesion, the thin fibrous septum in a type II SCM may not show up on preoperative neuroimaging studies. This should not deter an exploration, because in every case of type II SCM the author has explored, a taut fibrous or fibrovascular septum has been found to tether the hemicords. In addition, most SCMs located in the low thoracic or lumbosacral region have at least one associated lesion tethering the tip of the conus, which must also be removed during the same procedure. In contrast to children with SCM, the evidence to support prophylactic surgery in asymptomatic adults with SCM is much less convincing, and most adults have been operated on for symptoms and/or progressive deficits. There are currently no available data on the natural history of tethered cord syndrome in asymptomatic adults, but it is known that neurological deterioration can be precipitous after a fall or strenuous exercise. I therefore recommend operating on asymptomatic adults who are otherwise healthy and lead a physically vigorous life, but managing conservatively those who are old or infirm, or who have a sedentary lifestyle.
Preoperative Preparation Preoperative Neuroimaging Studies Magnetic resonance imaging (MRI) is an excellent screening test but will miss the details of structures within the median cleft. Computed tomographic myelography (CTM) with iohexol is more sensitive than MRI for displaying fine, soft tissue bands and associated myelomeningocele manqué, and it also shows the bony anatomy (such as the neural arches) to great advantage. It is superior to MRI in providing important information for precise localization of the septum and for delineating the size, obliquity, and relationships of the type I median septum. CTM is strongly recommended as the “surgical roadmap” for all SCMs.
Intraopearative Neurophysiological Monitoring Real-time intraoperative somatosensory evoked potentials (SEPs) are measured on all patients using standard needle electrodes overlying the common peroneal, posterior tibial, and median nerves. For monitoring the lower sacral sensory nerves and the S-2 to S-4 segments, pudendal SEPs are also obtained using pairs of disk or needle electrodes on either side of the penis in the male, and on the preclitoral skin and labia majora in the female. Occasionally, the lower sacral motor roots and the ventral conus segments need to be evaluated separately from the corresponding sensory pathways; for this, external urethral sphincter electromyography and external anal sphincter manometry using an anal balloon are also used during surgery. The latter techniques are especially useful to distinguish functioning lower sacral roots from taut fibrous bands that tether the conus.
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Operative Procedure Patient Positioning All patients are placed in the full prone position with parallel trunk rolls resting against the clavicles and anterior superior iliac spines. The abdomen must hang freely between the rolls to minimize venous bleeding. All electrophysiological stimulating electrodes and sphincter pressure monitors are checked for optimal functioning after the patient is settled in the final operative position but before operative drapes are applied.
Surgical Technique The aim of surgery is to relieve the cord of the tethering effect of the median mesenchymal septum. Because the relationship between septum and hemicords is so drastically different between type I and type II SCMs, the surgical techniques for the two lesions are also very different.
Type I SCM Planning the skin incision requires knowledge of the exact vertebral level of the median septum. This may be determined accurately from the preoperative CTM, then localized to the patient’s spine using a preoperative plain x-ray film and a surface metal marker, and finally confirmed at operation with an intraoperative x-ray film after exposure of the spinous processes. A linear midline skin incision is made to span at least two laminar levels above and two below the laminae bearing the septum. In a type I SCM, the bony septum is always extradural, being completely surrounded and excluded from CSF by the medial walls of the double dural tubes. The medial dural walls thus form a complete dural sleeve for the bone in the sagittal midline. The septum itself is frequently fused with, and thus hidden under, the neural arches so that it is not immediately visible after the subperiosteal exposure of the posterior bony structures. Noting the peculiar bony anatomy of the adjacent neural arches such as a bind state, eccentric spinous processes, exostoses, and abnormal fusion helps to guide the surgeon to the right level. Another useful hint is that the septum is often located where the spinal canal is widest, or where the neural arches and spinous processes are hypertrophic and fused with adjacent laminae into a knobby mass. The extent of the laminectomy should include at least one level rostral and one caudal to the septum-bearing laminae. The hypertrophic laminae are rongeured away piecemeal around the attachment of the septum until only a small island of lamina is left attached to the dorsal end of the septum (Fig. 18–3A). This affords a circumferential view of the bone spur still within its dural sleeve so that its dural attachment can be safely dissected off the bone deep within the cleft. However, it must be understood that once the dorsal support of the septum (by the laminae) is eliminated, the septum is no longer anchored rigidly at both ends and might be pushed from side to side depending on its ventral anchorage. Excessive lateral movement of the septum thus may injure the subjacent hemicords and must be avoided.
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120 Pediatric Neurosurgery A Woodson dental elevator with a thin, angulated, sharp edge is well suited to peel off the dura with minimal lateral “wedging” motions (Fig. 18–3B). In the majority of cases, the broader attachment of the septum is dorsal; its ventral junction with the vertebral body is usually narrow or even fibrocartilaginous rather than bony, which makes it easy to avulse the septum from its deep attachment (Fig. 18–3C). If the ventral attachment happens to be broad and bony, the ventral stub of the septum may be removed by a small pituitary rongeur or microdrill. Time is well spent during this part of the operation because complete extradural removal of the bone spur greatly facilitates later resection of the dural sleeve. In most type I lesions, the rigid septum is either purely bony or partly bony and partly fibrocartilaginous. Purely cartilaginous septa are rare. Bony or cartilaginous, the septum always encloses one or more prominent central blood vessels, which can give rise to brisk bleeding if torn. A quick plunge with a small piece of bone wax on a cotton patty deep into the cleft should handle the bleeding adequately. The dura is opened on both sides of the now-empty dural cleft to isolate the sagittal dural sleeve (Fig. 18–4A). The medial aspect of each hemicord is often tightly adherent to the dural sleeve by fibrous bands that must be cut (Fig. 18–4B). Paramedian dorsal nerve roots, when present in a type I lesion, typically stretch from the dorsomedial aspect of the hemicords to end blindly within the median dural sleeve. These are nonfunctional and must be cut prior to resection of the dural sleeve. The dural sleeve is always wedged against the caudal reunion site of the hemicords, and any “free” part of the hemicords not closely apposed to medial mesenchymal structures would be rostral to the septum. In a widely split cord, this free area is considerable and constitutes a safe area to begin resection of the dural sleeve. Proceeding caudally from the rostral margin of the sleeve where the hemicords are least adherent, the surgeon cauterizes the ventral attachment of the sleeve to seal the central vessels and then cuts it flush with the ventral dural wall (Fig. 18–5A). Not having the enclosed bone spur greatly simplifies the deep resection of the sleeve. The most hazardous part of this undertaking is at the caudal end where the hemicords reunite and hug tightly against the caudal margin of the sleeve, where the taut pressure on the cord is readily felt and where slight upward migration of the cord might sometimes be seen right after the whole sleeve has been resected. Complete resection of the dural sleeve exposes the ventral extradural space in the sagittal midline (Fig. 18–5B). If a prominent bony stump is left from the extradural removal of the septum, it can be trimmed down easily with a small ophthalmic rongeur until it is no longer in contact with the ventral surface of the hemicords. Closure of the anterior dural defect is unnecessary because of the abundant adhesions of the ventral dura to the posterior longitudinal ligament that would naturally prevent CSF leakage. Anterior dural closure may actually be undesirable because the anterior suture line potentially increases the likelihood of anterior cord tethering. Posterior dural closure ultimately converts the double dural tubes into a single sac. Occasionally, a fibroneurovascular stalk containing paramedian dorsal nerve roots, fibrous bands, and large blood
Figure 18–3 Exposure of a type I bony septum. (A) After the laminae rostral and caudal to the midline septum are resected, the septumbearing laminae are removed carefully around the dorsal “stump” of the septum where it is attached to the ventral surface of the hypertrophic neural arches. (B) The surgeon then performs subperiosteal separation of the median dural sleeve from the bony septum with a small dental elevator. (C) The bony septum is then avulsed from its ventral attachment, which is often slender. 10.1055/978-1-60406-039-3c018_f003
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Figure 18–4 Intradural exposure of a type I SCM. (A) A dural opening is made from rostral to caudal along the medial edge of the median dural sleeve (dashed line). (B) After lateral retraction of the dura, the median
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dural sleeve is isolated except ventrally. Note the paramedian dorsal roots attaching the medial aspect of each hemicord dural sleeve.
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vessels tautly tethers the hemicords to the dorsal dura (myelomeningocele manqué). These bands always penetrate the dura at a level more caudal than their origin from the hemicords, and they often form an exuberant tuft of vascular fibroadipose tissue clinging tenaciously to the outer surface of the dura. These bands must be cut flush with the hemicords to complete the untethering process. The tuft of extradural fibroadipose tissue, which cannot be swept away with the “normal” extradural fat, is a clue to the presence of the myelomeningocele manqué underneath.
Type II SCM In all cases of type II SCM, some form of fibrous (mesenchymal) septum is found within the midline cleft. The aim of surgery is to remove the tethering effect by resecting the fibrous septum and any associated bands such as those of a myelomeningocele manqué. Three patterns of such nonrigid median septa are found in type II lesions: (1) The least common is a complete fibrous septum stretching between the ventral and dorsal surfaces of the dural sac. The septum is entirely intrathecal. Except for this feature and the fact that it is nonosseous, the complete fibrous septum transfixes the hemicords to the surrounding
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Pitfall In 5 to 10% of type I SCMs, the bony septum is oblique. It arises from the midline posterior surface of the vertebral body but then immediately reaches diagonally across the spinal canal to divide it into two asymmetrical compartments. Without exception, the hemicord contained within the larger compartment (major hemicord) is much larger than the hemicord in the smaller compartment (minor hemicord), sometimes by a factor of 2 or 3. Moreover, the larger hemicord frequently possesses one set of lateral ventral roots but two sets of dorsal roots, whereas the smaller hemicord gives off only a single set of ventral roots. In these unusual cases, the exposure of the minor hemicord is hampered because it is partly sheltered by the overhanging oblique bone spur as well as being ventrally rotated away from the surgeon’s view. Moreover, the smaller hemicord is extremely delicate. It can thus be injured inadvertently during the removal of the bone spur. This unusual pattern of asymmetric splitting must be recognized through preoperative imaging as a signature of heightened risk, so that the surgeon can make every effort to avoid jarring the delicate minor hemicord while dealing with the blind underside of the oblique bone spur.
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A
B Figure 18–5 Resection of the median dural sleeve of a type I SCM. (A) The dural sleeve is resected flush with the ventral dural surface, proceeding from the rostral “free part” to the caudal end. Note the thickened filum terminale. (B) A ventral dural defect is left after complete
resection of the dural sleeve flush with the vertebral body. Note the sectioning of the thickened filum after it has been cauterized. The conus is now completely untethered.
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dura in the same manner as does the type I bony septum. (2) Slightly more common is the purely ventral fibrous septum. Its intimate adherence to the ventromedial aspects of the hemicords in effect anchors the cord ventrally where the incomplete septum fuses with or penetrates the ventral dura. (3) The most prevalent kind is the purely dorsal septum that attaches the dorsomedial aspects of the hemicords to the dorsal dura. A tuft of fibrovascular tissue in the extradural space is sometimes found connected to the septum through a small defect in the dorsal dura. Hypertrophic and fused laminae, common in type I lesions, are seldom found in type II SCMs. In fact, the neural arches of type II lesions are often attenuated or even bifid. Laminectomy for these SCMs is technically easy and safe. However,
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except where there is a tuft of fibrovascular tissue clinging tenaciously to the dura, marking the site of a dorsal septum, the exact location and extent of the purely intradural type II fibrous septum is usually not apparent after dural exposure. This underscores the importance of pinpointing the precise location of the type II septum before laminectomy by carefully studying the bony anatomy on the CTM. A midline dural opening immediately exposes the purely dorsal septum and the dorsal portion of a complete septum, to one side of the dural incision (Fig. 18–6A). A purely ventral septum and the ventral part of a complete septum have to be sought, either between the hemicords or by gently rotating the hemicords to one side (Fig. 18–6B). Like the type I bony septa, type II fibrous septa are found near the caudal
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A
B Figure 18–6 Treatment of a type II SCM. (A) Shown is a type II SCM with a purely dorsal fibrous septum attached to the medial aspects of the hemicords. Note the direction of the septum, which points caudally toward the dorsal dura. The large fibroneurovascular stalk of a myelomeningocele manqué is just caudal to the midline septum. Ex = an extradural fibroadipose tuft attached to the myelomeningocele manqué;
end of the split. However, the length of split in type II lesions is, by comparison, much shorter than that of the type I SCM, and, because fibrous septa are thin, the hemicords in type II SCM are apposed much closer together, with very little “free” part. “Intra-cleft” exploration in some type II lesions, therefore, should not be attempted. Fortunately, the spinal canal at the site of the split is usually wider than usual and thus will allow the hemicords to be rolled gently to one side for ventral exploration.
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MM = myelomeningocele manqué; N = a paramedian dorsal nerve root within the septum. (B) A type II SCM with a purely ventral fibrous septum. Note the anterior marginal artery at the edge of the septum, and the direction of the septum, pointing caudally toward its ventral dural attachment. 10.1055/978-1-60406-039-3c018_f006
The shape of the type II septum varies from a broad rectangular or trapezoid sheet to a narrow triangular sail, but one invariant feature is that the point of attachment between hemicords and septum is usually rostral to the point of attachment between dura and septum (Fig. 18–6A). This is true of all three kinds of fibrous septa, giving the appearance that the fibrous septum is dragged upward by rostral movement of the cord occurring after formation of the primordium of the septum. This upward dragging converts
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124 Pediatric Neurosurgery the incomplete (ventral or dorsal) septum into a backwardpointing oblique sheet and the complete septum into a Vshaped sheet with the apex pointing rostrally. Centromedian blood vessels are always seen with the type II septa, either as a marginal artery skirting the rostral or caudal edge of the septum (Fig. 18–6B), or as a leash of parasagittal vessels loosely incorporated with the septum on either side. Very rarely, a true arteriovenous malformation is seen, with large vessels weaving in and out of the median cleft. Unless these large vessels are contributing to the tethering of the hemicords, they should be left alone. Paramedian dorsal nerve roots and myelomeningocele manqué are commonly found in type II SCMs (Fig. 18–6A). Such roots invariably course dorsally after emerging from
Figure 18–7 A composite SCM (type I-type II-type I combination). (A) An axial view from a computed tomographic myelogram (CTM) shows a type I SCM at T-12 with an oblique bony septum and double dural tubes.
the dorsomedial aspect of the hemicords. The puny nerve roots either end blindly in the septum or penetrate the dorsal dura with the septum. The more robust fibroneurovascular stalks of the myelomeningocele manqué always penetrate the dorsal dura at a level more caudal than their hemicord origin. These bands contribute to the tethering and must be cut flush with the cord surface. Untethering is completed by simply cauterizing the central vessels and excising the median fibrous septum. In some cases of complete sepia, the fibrous and vascular elements are seen coming through a small defect in the ventral dura, presumably where the original endomesenchymal tract arose. This small defect never leaks CSF and does not need to be repaired.
(B) This CTM view shows a type II SCM at L-1 with an oblique fibrous septum within a single dural sac. (C) This CTM view shows a type I SCM at L-4. All three septa are coplanar in obliquity.
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18 Special Circumstances Associated Distal Tethering Lesions Associated tethering lesions not directly connected with the SCM are common. In my recently reported series of 39 cases, all SCMs located below T-7 were associated with at least one additional lesion tethering the conus, whereas the majority of SCMs above T-7 had no other cord anomaly. The most common conus lesion is a thickened filum, followed in prevalence by terminal and dorsal lipomas, dermal sinus tracts, and limited dorsal myeloschisis. Thus, the entire neuraxis
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must be screened carefully by preoperative neuroimaging. The untethering is not complete unless these secondary lesions are also treated (Fig. 18–5).
Composite SCMs and Multiple SCMs A composite SCM consists of two or more SCMs of differing types occurring in tandem, with no normal cord between each individual SCM. The most common composition of a composite SCM is a type I-type II-type I combination (Fig. 18–7). Each individual component is typical of its kind: Each
A
B Figure 18–8 Intraoperative exposure of a composite SCM (same lesions. The fibrous septum has been resected, which pro-case as shown in Fig. 18–7, after the two type I bony septa have vides room in the middle; the dural sleeves now can be resected been removed. (A) a midline
type II fibrous septum fills the safely from a middle free space toward the respective .crotches. interval between the median dural sleeves of the two type I of the split cord.
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126 Pediatric Neurosurgery of the type I lesions has an extradural osseocartilaginous spur, median dural sleeve, and hypertrophic neural arches, and the middle type II lesion has a median fibrous septum within a single dural tube. The three septa, although of two different textures, are invariably continuous, suggesting that the entire lesion results from a single (but very large) endomesenchymal tract in which meninx primitiva precursor cells have been included at both ends to cause the type I configuration, but they have not been included in the middle where the median septum remains fibrous. The total length of the septa can be very long, sometimes spanning as many as seven vertebral levels. The split cord is coextensive with the septa so that the rostral and caudal reunion sites of the hemicords hug tightly to the rostral margin of the rostral bone spur and the caudal margin of the caudal bone spur, respectively. Exposure, laminectomy, and extradural resection of the two type I bone spurs are as described above. The dural opening begins rostral to the rostral dural sleeve, skirts around it, returns to the midline over the type II lesion, and finally skirts around the second dural sleeve (Fig. 18–8A). Resection of the middle type II fibrous septum should then be done to gain a “free” area within the midportion of the median cleft. This will provide working room to begin the resection of the type I dural sleeves above and below; for the rostral dural sleeve, resection goes from caudal to rostral, whereas resection goes from rostral to caudal for the caudal dural sleeve. This way, the manipulation of the dural sleeve is always directed toward and never away from the tight reunion site of the hemicords at either end (Fig. 18–8B). Central vessels and paramedian nerve roots are scattered throughout the extent of the long row of midline septa and all have to be divided. Release of the cord is accomplished with total excision of all three septa and reconstruction of a single dural sac for the entire affected length of the cord. If two or more SCMs occur in the same patient but are separated by an interval of normal spinal cord, they are true multiple SCMs. These are rare because they result from multiple endomesenchymal tracts, that is, from multiple embryological errors in the same neural tube. The individual SCMs may be all type I or type II, or of each type. Their surgical treatment is as described.
Associated Dermal Sinus Tract and Dermoid Cyst A dermal sinus tract is formed when the original connection between the endomesenchymal tract and the cutaneous ectoderm is retained. Because of this embryological relationship, the deep end of the sinus tract is always in continuity with the mesenchymal median septum regardless of the type of SCM, but because the median septum is either extra- or intrathecal depending on the lesion type, the clinical significance of the retained dermal sinus tract depends on the type of SCM it is associated with. For a type I lesion, the dermal sinus tract can be traced all the way from the cutaneous opening (the pit) through midline defects in the lumbosacral fascia, muscles, and neural arches to the bone spur (Fig. 18–9A). Thus, the tract is
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always excluded from the CSF, and except in rare situations where it penetrates one wall of the median dural sleeve to involve the hemicord, it does not contribute to the tethering. It is removed together with the bone spur before the dura is ever opened. Even if the tract may occasionally encyst to form a dermoid cyst, it lies outside the dural sac and seldom becomes large enough to cause compression of the hemicords. In a type II SCM, however, the dermal sinus tract is of necessity intradural where it retains connection with the median fibrous septum. In its intradural course, the sinus tract is often densely adherent to the hemicords or the cord caudal to the caudal reunion site, thereby exerting a separate tethering effect on the cord. In addition, more than 50% of dermal sinus tracts in a type II SCM will develop a dermoid cyst within the dura, often large enough to cause cord compression (Fig. 18–9B). The entire intradural sinus tract and cyst must be excised to eliminate the tethering effect and prevent recurrence. The cyst is first collapsed by intracapsular evacuation of its “cheesy” content, and the cyst wall is then carefully peeled off the pial surface of the cord. Its deep end is removed with resection of the fibrous median septum.
Associated Myelomeningocele and Hemimyelocele Approximately 25 to 35% of SCMs have an associated, and adjacent, open neural tube defect. Depending on whether one or both hemicords are involved in the dysraphic sac, the lesion may contain a hemimyelocele or a full-blown myelomeningocele, respectively. In most myelomeningoceles, the open neural placode is terminal and thus is caudal to the SCM. Less commonly, the open placode is segmental and may therefore be either rostral or caudal to the SCM. Because the open dysraphic sac is usually treated at birth, by the time the SCM is diagnosed by later neuroimaging studies and explored via a second surgical procedure, the original neural placode would have already developed dense adhesions to the dorsal dura. Because the placode is always adjacent to the split cord and may well be contributing to the tethering, it is always freed from the dura when the SCM is being treated. The most caudal set of intact laminae above the open spinal defect are removed to expose normal, nonadherent dura. Depending on whether the placode is rostral or caudal to the SCM, it is carefully detached from the dorsal dura by sharp dissection with microscissors either before or after the median septum is excised. Most hemimyeloceles are segmental. The unaffected hemicord is usually hidden from view by the median septum during the original sac closure, when the hemiplacode is mistaken to be the whole lesion. During the definitive procedure for the SCM, the entire dural sac (double or single) must be exposed to give access to both hemicords. This often requires cutting into dense scar tissue. Again, removing the adjacent normal laminae helps to define the full width of the dura rostral to the scar. After identifying and removing the median septum, the hemiplacode is detached from the dorsal dura with sharp dissection.
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A
B Figure 18–9 SCM and associated dermal sinus tract. (A) In a type I SCM, the dermal sinus tract is continuous with its bony septum and median dural sleeve but is entirely extradural. (B) In a type II SCM, the dermal 10.1055/978-1-60406-039-3c018
Postoperative Management Including Possible Complications
sinus tract is intradural. A large dermoid cyst within this tract maintains a connection with the median fibrous septum (the original endomesenchymal tract).
Neurological Injury
the bone spur. This is especially true when the bony septum is oblique and the delicate minor hemicord is tucked under the overhanging septum within the acute angle made by the septum and the vertebral body. The risk of hemicord injury is minimized by the following precautions:
Worsening of neurological function occurs in <5% of patients following surgery for SCM. In general, the surgical morbidity is higher among patients with a type I SCM, probably as a result of injury to the hemicords during removal of
1. Accurate preoperative depiction of the peculiar angulation of the bony septum and the relationship of the minor hemicord to the bony overhang. 2. Wide laminectomy at the site of the septum to improve
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128 Pediatric Neurosurgery exposure of both dural sacs. Without wide exposure, the oblique bone spur may be mistaken for the lateral wail of the spinal canal. 3. Extremely careful piecemeal resection of the dorsal end of the septum. As more of this end of the septum is bitten away, more of the minor dural tube is exposed, which in turn will permit further peeling of the median dural sleeve off the underside of the septum to prepare for more bone removal.
Cerebrospinal Fluid Leakage Wound complications are seldom encountered in patients with SCM except when there is a previously treated open neural tube defect adjacent to the split cord. These children often have poor myofascial coverage as well as tenuous, scar-ridden skin over the dural sac and may develop CSF leakage through the incision. This underscores the importance of a watertight dural closure. In addition, these children should be managed in the fully prone position for 5 to 7 days after surgery similar to the way a newborn with a myelomeningocele is positioned after sac closure. Heavy sedation may be necessary to prevent an infant from wiggling too much and pulling too vigorously at the incision.
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Postoperative Bladder Management Transient detrusor weakness and urinary retention is not uncommon after the resection of a type I SCM. It can last from a few days to several months and tends to be more common in adults than in children. Permanent worsening in bladder function occurs in ~3% of patients. A bladder catheter is left in the first 2 postoperative days when the patient is confined to complete bedrest. The catheter is removed on the third postoperative day as the patient is encouraged to ambulate and use bathroom facilities. If there is obvious difficulty in micturition or if a large postvoid residual urine volume is obtained repeatedly, the patient is given a cholinergic agent such as bethanechol chloride to strengthen detrusor contraction, or an a-sympathetic blocker such as prazosin hydrochloride to encourage relaxation of the internal urethral sphincter. If the postvoid residual urine volume remains high on medication, an intermittent catheterization program is started in the hospital and is continued on an outpatient basis. After 4 to 6 weeks, a cystometrogram is obtained to evaluate bladder function and to determine whether therapy can be discontinued.
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19 Tethered Cord Syndrome Secondary to Previous Repair of a Myelomeningocele Timothy A. Strait Until a satisfactory technique for primary repair of a myelomeningocele in a newborn is devised, retethering with the potential for delayed neurological deterioration will remain a vexing problem for the pediatric neurosurgeon. Invariably, scarring occurs between the neural placode and the overlying dura, which fixates the end of the spinal cord. Progressive longitudinal tension builds up within the cord because its growth is exceeded by that of the spinal column. The greatest amount of tension exists within the cord segment between the attachments of the last pair of dentate ligaments at T-12 and the adherent neural placode. Cord damage probably occurs from a combination of repeated insults from both stretching with movement and compression by the overlying most caudal intact lamina. These mechanical forces have been shown to produce vascular changes that impair oxidative metabolism. Surgical untethering can reverse the vascular abnormalities and prevent permanent cord damage. This chapter will focus on the operative management of patients with a tethered cord syndrome arising from a previous myelomeningocele repair in the lumbar region. The fundamental principle of the surgical procedure is a rostral-to-caudal approach, working from normal to disturbed anatomy. This method allows for easy identification of the important anatomical landmarks, which safely leads to the area of tether and reduces the risk of inadvertent injury to viable neural elements.
is to halt the progression of the neurological deficit. When a tethered cord is present on MRI in a child who has not yet reached a major growth spurt, I generally favor intervention even in the absence of symptoms because of the risk of deterioration. Finally, most children should undergo elective untethering before corrective surgery for scoliosis. Once a candidate for surgery has been chosen, the preoperative neurological examination provides insight regarding the lowest level of functioning spinal cord.
Preoperative Preparation Anesthesia This operation is performed under general endotracheal anesthesia using inhalational agents. Muscle paralysis is not used because nerve stimulation is often necessary. Prophylactic vancomycin is administered at least 45 minutes prior to making the incision.
Precautions In most cases, latex precautions are undertaken. This includes avoidance of all items made of latex. Most importantly, cases are scheduled as first for the room because it has been shown that circulating latex particles are largely responsible for eliciting allergic reactions.
Patient Selection Children and young adults with a previous myelomeningocele repair who develop symptomatic retethering present commonly with progressive pain, leg weakness, and scoliosis. Physical examination is frequently difficult to interpret because the vast majority of patients have a preexisting neurological deficit. The detection of a tethered cord has become extremely accurate with magnetic resonance imaging (MRI). Typically, an elongated spinal cord is seen attached to the previous repair site. The terminal portion of the spinal cord is displaced dorsally and often contains a syringohydromyelic cavity (Fig. 19–1). Patients with a symptomatic tethered cord are generally offered operative intervention. The principal goal of surgery
Operative Procedure Positioning The patient is placed prone on the operating table with foam chest rolls to allow adequate respiratory excursion and reduce intra-abdominal pressure. Older children are placed in the knee-chest position on an Andrews spine frame. All pressure points are padded well. The head is turned to one side and rests on a comfortable headrest (Fig. 19–2A). The anesthesiologist, anesthesia equipment, and monitoring devices are all at the head of the operating table. The sur-
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Figure 19–1 Sagittal magnetic resonance imaging scan of a 4-year-old child with a previous L-5 myelomeningocele repair. An elongated spinal cord is seen with the terminal portion tethered to the previous operative
geon and assistant are opposite each other at the patient’s sides and the scrub nurse is next to the surgeon toward the patient’s feet. The operating microscope is mounted with the assistant’s observation port and is draped with commercially available plastic drapes. The microscope stand is positioned near the head of the table and is brought in from the side opposite the surgeon. The skin is shaved and adhesive plastic drapes are applied around the proposed incision. When plastic reconstruction of the previous skin incision is planned, an expanded surgical field is required. The lumbar area is scrubbed with providone-iodine soap and then painted with a 10% solution of providone-iodine. The surgical field is draped using first towels, then an iodinated adhesive plastic sheet, and finally disposable sheets. The proposed incision is infiltrated with lidocaine with 1:200,000 epinephrine for hemostasis.
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site. The cord is displaced posteriorly and contains a syringohydromyelic cavity. 10.1055/978-1-60406-039-3c019
Incision and Exposure The skin incision is in the midline, beginning over the most caudal intact lamina; it is carried down to the fascia. A selfretaining Weitlaner retractor is used to expose the underlying fascia. With the electrocautery, the fascia is incised and the paraspinal musculature is dissected from the spinous process and laminae in the subperiosteal plane. Retraction of the muscles is performed with a bilaterally bladed retractor. A complete laminectomy is performed with the Midas Rex pneumatic drill (Medtronic, Inc., Fridley, MN) to expose the dural tube several centimeters cephalad to the previous myelomeningocele repair. Once the dural plane has been established, the skin incision is then extended caudally and carried down to the level of the dura overlying the neural placode (Fig. 19–2B).
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Figure 19–2 (A) The patient is placed prone on the operating table with foam chest rolls. (B) Line drawings of sagittal and posterior views depict the surgical anatomy of a previously repaired lumbar myelomeningocele. The cord is tethered by the neural placode scarred to the dura. 10.1055/978-1-60406-039-3c019
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132 Pediatric Neurosurgery
A
B
C
D Figure 19–3 Following a laminectomy of the lowermost lamina, (A) the dura cephalad to the previous repair site is opened in the midline and (B) this opening is extended caudally to the neural placode. (C) The arachnoid is opened and (D) retracted bilaterally. 10.1055/978-1-60406-039-3c019
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At this point, the microscope is brought into the operative field. The dura cephalad to the repair site is opened in the midline with care to preserve the arachnoid (Figs. 19–3A and 19–3B). Dural tack-up sutures are placed and cottonoid strips are laid over the exposed dura. Tension on the tack-up sutures provides better exposure and relative hemostasis of bleeding from the epidural space. The dural incision is extended caudally to the neural placode (Fig. 19–3B and 19–3C). The dorsally displaced spinal cord is visible immediately beneath the arachnoid. The arachnoid is opened carefully by sharp dissection and its edges are secured to the dura with Weck clips (Fig. 19–3D). Arachnoid dissection is directed
caudally to permit identification of the spinal cord–neural placode junction. Dense adhesions between the neural placode and the overlying dura are encountered. It is usually unnecessary to dissect the entire neural placode from the overlying dura because it ordinarily contains no functional tissue. However, nerve roots exiting at this segment are stimulated with a stimulator to determine whether useful function is present (Fig. 19–4A). Functioning nerve roots are preserved carefully and mandate transection of the cord below the level at which they exit (Fig. 19–4B). The spinal cord generally is transected at the cephalad aspect of the neural placode. Usually the terminal portion of the spinal
A
B
C Figure 19–4 (A) The arachnoid dissection is directed caudally to the spinal cord–neural placode junction; the lowest functional nerve roots are identified. (B) The cord is transected at the cephalad aspect of the
neural placode. (C) The cord retracts rostrally and resides in an arachnoid enclosure.
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134 Pediatric Neurosurgery cord retracts rostrally and resides in a more ventral position within the arachnoid enclosure (Fig. 19–4C). The configuration of the superficial vasculature changes from linear to coiled after the cord tension is released. Another finding indicating successful untethering is that the exiting nerve roots from the lower portion of the cord follow a downward oblique course rather than a transverse or upward course (Fig. 19–4C).
Closure A large bulbous neural placode complex or a dermal inclusion cyst requires total excision to facilitate closure. Closure begins with a meticulous reapproximation of the previously opened arachnoid with 10–0 interrupted sutures (Fig. 19– 5A). This layer will prevent the transected end of the cord from retethering to the overlying dura. If a shallow dural
A
B C Figure 19–5 (A) Closure of the arachnoid layer prevents the retracted end of the cord from retethering to the overlying dura. (B) A duraplasty is performed with cadaver dura. (C) The rest of the wound is then closed in anatomical layers. 10.1055/978-1-60406-039-3c019
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tube exists, duraplasty with a cadaver dural graft is performed (Fig. 19–5B). Otherwise, the dura is closed with interrupted 4–0 sutures. A paravertebral fascial layer closure is accomplished after bilateral relaxing incisions are made. The subcutaneous layer and finally the skin edges are closed with sutures and staples, respectively (Fig. 19–5C). A sterile dressing is applied.
Postoperative Management Including Possible Complications
gery. Patients without an indwelling shunt are susceptible to postoperative cerebrospinal fluid leakage in the event that a watertight dural closure is not achieved. This problem is handled either by reoperation and suture closure or by inserting a temporary external lumbar drain and keeping the patient recumbent for several days. Wound dehiscence is prevented by excising broad dermal scars in an elliptical fashion and closing the skin without undue tension after widely undermining the subcutaneous layer from the fascia. The risk of retethering is reduced by a meticulous arachnoid closure.
A postoperative low-pressure headache is avoided by keeping the patient recumbent for the first 24 hours after sur-
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20 Sectioning of the Filum Terminale Frederick B. Harris, Naina L. Gross, and Frederick A. Boop
The tethered cord syndrome is a complex of neurological symptoms and orthopedic deformities associated with a low-lying conus medullaris (below L2–3). Embryologically, abnormal retrogressive differentiation of caudal cell mass presumably gives rise to the hypertrophied filum terminale leading to a tethered cord. Recent radiological advances have improved our knowledge and understanding of the pathogenesis and associated pathologies. It is a common feature in many congenital malformations such as spinal lipoma, diastematomyelia or split cord malformation, myelomeningocele, cloacal malformations, and tight filum terminale. Symptomatic tethering may also occur after longitudinal growth in patients with scarring after myelomeningocele repair, spinal tumor resection, or trauma. The tethered cord syndrome may be seen at any age; however, symptoms usually begin in childhood without gender predilection. Clinical signs and symptoms of the tethered cord syndrome may vary and commonly include spina bifida occulta, lower extremity weakness with gait difficulty, muscle atrophy, a short limb, ankle abnormality, perineal or lower extremity sensory deficits, bladder dysfunction, pain (back, leg, or foot arches), and kyphoscoliosis. Occult tethering may have delayed onset of symptoms into adulthood, with a peak incidence in the fourth decade of life. The advent of magnetic resonance imaging (MRI) has led to increased awareness of the tethered cord by pediatricians, orthopedists, and urologists, allowing for more frequent diagnosis. Many cases of tethered cord are incidential findings in neurologically normal patients due to imaging studies performed for other reasons. Surgery for the release of a tethered cord has become one of the most common operations done by pediatric neurosurgeons. Ninety percent of pediatric patients presenting with pain have complete relief or improvement following surgical sectioning of the filum terminale. Seventy five percent of patients presenting with motor symptoms have improvement in motor function following surgery. However, only 50% presenting with bowel and bladder dysfunction improve following surgery. Patients with progressive scoliosis may experience stabilization or improvement of their scoliotic curvature with early untethering; therefore, release of a tethered cord should generally be considered prior to scolioisis correction.
Patient Selection The diagnosis of a tethered cord in the newborn usually occurs after the recognition of a midline cutaneous anamoly such as an intergluteal sinus or dimple, tuft of hair, hemangioma, cutis aplasia, or subcutaneous lipoma. The diagnosis is also often made when infants with cloacal malformations (cloacal exstrophy, anal atresia, omphalocoeles) are studied with spinal ultrasound. Beyond the first few weeks of life, ossification of the dorsal elements may limit the use of ultrasound, therefore requiring MRI. Loss of continence after toilet training and an associated history of constipation are the most common symptoms beyond
Figure 20–1 A sagittal T1-weighted magnetic resonance image through the lumbar region demonstrates a thickened filum terminale. The hyperintensity (arrows) indicates fatty infiltration of the filum. 10.1055/978-1-60406-039-3c020_f001
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20 infancy. Complaints of intermittent back and leg pain, especially evoked by exertion, may be associated. These patients most commonly have a normal neurological exam, but physical findings may include pes cavous deformity, calf wasting, atrophy of a gluteus muscle, asymmetry of foot size, lower sacral hypesthesia, and mild scoliosis. Spinal radiographs may show spina bifida occulta and urodynamic studies may reveal a neurogenic bladder. Myelography is usually not necessary and MRI is the diagnostic study of choice (Fig. 20–1). Children symptomatic for 6 months or less can generally expect improvement in their symptoms following surgery. On the other hand, those symptomatic for 1 year or more may often have stabilization of their symptoms or deficits but a lower chance of neurological improvement. Once a child becomes symptomatic, the natural history is usually one of symptomatic progression. The best management for asymptomatic, neurologically normal children with incidental findings on imaging remains controversial. It is the responsibility of the surgeon to discuss with the family the information available on the natural history and chances of recovery once the child becomes symptomatic. Fat in the filum is a frequent incidental MRI finding, and if the conus is at a normal level and there are no clinical indications of a tethered cord, surgery is usually not recommended; however, these children should be followed clinically.
Preoperative Preparation Careful evaluation of the axial MRI through the lumbar spine is necessary preoperatively to document any associated pathology such as a dermal sinus tract. When this is noted, the filum may not traverse the length of the spinal canal but attach to the thecal sac dorsally. MRI is helpful in determining the appropriate level of the laminotomies.
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Patients are instructed to bathe well the night prior to surgery and receive perioperative antibiotics. Patients who already have an active infection of a sinus tract or meningitis should be treated adequately for such infection prior to any surgical intervention.
Anesthesia Considerations It is recommended that the anesthesiologist use a shortacting muscle relaxant during induction to allow for intraoperative stimulation of nerve roots, if necessary, and to allow for the recognition of motor response with inadvertent stimulation of nerve roots. Intraoperative spinal cord monitoring is not routine for a simple sectioning of a thickened filum terminale; however, it may be useful in other pathologies such as repair of a diastematomyelia.
Operative Procedure Positioning After securing the endotracheal tube and placement of a Foley catheter, if warranted, the patient is placed in the prone position on chest rolls extending from chest to the iliac crest (Fig. 20–2). This prevents abdominal compression and secondary distension of the epidural venous plexus, reducing venous bleeding. Arms are placed on arm boards for anesthesia access, and all pressure points are padded. The patient is then placed in a slight Trendelenburg position to reduce loss of cerebrospinal fluid during the procedure, which can be especially problematic in a patient with ventriculomegaly.
Figure 20–2 The patient is positioned prone on bolsters with padding of all extremities. A slight Trendelenburg position prevents the overdrainage of cerebrospinal fluid. 10.1055/978-1-60406-039-3c020_f002
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138 Pediatric Neurosurgery Surgical Technique An extended caudal-to-rostral sterile preparation and draping should be performed to allow for extension of the incision as needed. The planned incision is marked on the skin in the midline, and the dermis is injected with lidocaine with epinephrine. An incision is made and dissection is carried down to the level of the thoracolumbar fascia incorporating any existing dimple or sinus tract by ellipsing around the opening in the skin (Fig. 20–3). Hemostasis is obtained with the bovie and bipolar cautery. The surgeon must keep in mind that in spina bifida patients and infants that the lamina and spinous processes may not be fully developed or ossified. Care must be taken not to inadvertently pass instruments into the spinal canal. The paraspinous muscles are dissected away from the lamina in the subperiosteal plane out to the facets, leaving the facet joint capsule intact. A self-retaining retractor is then placed. The partial laminectomy is then performed removing both the inferior half of the superior lamina and the superior half of the inferior lamina at the level of pathology. Following
the laminotomy, the dura is cleared of ligamentum flavum and epidural fat using sharp dissection and bipolar cautery. A 2 cm segment of exposed dura is adequate for simple filum sectioning. At this point, hemostasis is imperative to prevent excessive bleeding from epidural veins once the dura is opened and the thecal sac decompressed. A midline durotomy is next performed using a sharp scapel and hook. 4–0 Surgilon suture is then placed in the dura to retract the edges (Fig. 20–4A). Next, microscissors are used to open the arachnoid and expose the filum. The filum is located in a dorsal midline position and has a different texture and color (purple hue) in comparison with nerve roots due to fatty infiltration and associated veins. Upon identification of the filum, it is elevated with a nerve hook and the undersurface inspected for possible adherent nerve rootlets (Fig. 20–4B). The filum is carefully isolated from all nerve roots. The filum may be stimulated with low electrical current if desired. Higher current is avoided because current spread may stimulate other roots and give a false impression. Once it is clearly identified, the filum is coagulated with bipo-
Figure 20–3 The surgeon’s view demonstrates the skin incision (straight dashed line) and the underlying laminectomy (dashed rectangle). 10.1055/978-1-60406-039-3c020_f003
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A
B Figure 20–4 (A) The dura is opened longitudinally and the filum terminale is exposed. (B) The thickened filum is elevated using a sharp nerve hook. It is inspected carefully for adherent nerve rootlets. Elec-
tricical stimulation may be necessary to differentiate this structure from a nerve root.
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140 Pediatric Neurosurgery
C
D Figure 20–4 (cont'd) (C) Bipolar coagulation prior to sectioning prevents bleeding from the retracted ends of the filum following transection. (D) The dura is repaired in a watertight fashion with 4–0 braided
nylon or silk. Note the rostral migration of the conus medullaris following sectioning of the filum.
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20 lar forceps and sectioned with microscissors (Fig. 20–4C). After sectioning, the ends of the filum will retract up into the spinal canal, so one must be sure of hemostasis prior to completing the sectioning.
Closure Prior to closure of the dura, the intradural space is thoroughly irrigated with sterile saline to wash out any blood. Once hemostasis is obtained and the irrigant is clear, the dura is closed with 4–0 Surgilon sutures (Fig. 20–4D). A Valsalva maneuver is performed to verify the integrity of the dural closure. The epidural space is irrigated with bacitracin in saline. Gelfoam is then placed in the epidural space to serve as a blood patch to prevent spinal headaches. A dural sealant such as Tisseal or DuraSeal (Confluent Surgical Inc., Waltham, MA) placed in the epidural space may allow earlier mobilization of the child. Quarter percent bupivicaine can then be infiltrated in the paraspinous muscles and wound edges for postoperative pain control. The paraspinous muscles and fascia are then reapproximated with 2–0 or 3–0 interrupted Vicryl sutures. The subcutaneous tissues are reapproximated, and the skin is closed with subcuticular Monocryl sutures.
Postoperative Management Including Possible Complications Dermabond (Ethicon Inc., Somerville, NJ) skin glue is applied to the wound to allow for early bathing without wound contamination. The patient is also left horizontal for up to 8 hours, thereby preventing spinal headaches. The patient’s diet is advanced as tolerated and fluids are encouraged. Patients are generally discharged home on the first postoperative day once ambulatory and voiding.
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Complications and Prognosis Low-grade fevers or symptoms of meningismus may occur secondary to intradural blood. Occasionally children may develop difficulty with urination requiring intermittent catheterization from manipulation of the lower nerve roots. All of these symptoms may prolong hospitalization; however, most resolve spontaneously within a few days. There is a very low risk of infection and also minimal blood loss occurs during this procedure. Spinal fluid leak is a risk but uncommon with good watertight wound closure. Souweidane and Drake have reported two cases in which the sectioned filum terminale scarred into the wall of the dura and, over time as the children grew, led to recurrent tethering. Aside from these two cases, it is generally felt that sectioning of a symptomatic filum is curative. Orthopedic and motor deficits should stabilize and sensory symptoms are likely to resolve. However, follow-up MRI imaging will always demonstrate a low-lying conus and, in the absence of clinical history, will be interpreted by the radiologist as showing a tethered spinal cord. Acknowledgment This chapter is a revision of the chapter, “Sectioning of the Filum Terminale” by Frederik A. Boop, M.D., and William M. Chadduck, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 3, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank William M. Chadduck, M.D., for his help and efforts on the original chapter published in the first edition of this work.
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21 Diastematomyelia Frederick B. Harris, Naina L. Gross, and Frederick A. Boop
Diastematomyelia, or split cord malformation (SCM) type I, is a congenital spinal anomaly in which the spinal cord is divided longitudinally by a fibrous or bony septum. It has been proposed that this malformation originates from one basic error that occurs at the time of closure of the primitive neurenteric canal. Formation or persistence of an accessory neurenteric canal between the yolk sac and the amnion occurs, creating an endomesenchymal tract that splits the notochord and neural plate. This defect has been reproduced in salamanders in the study of Emura, confirming the embryogenesis. There are two types of SCM. Type I SCM consists of two hemicords, each with its own dural tube and separated by a dura-ensheathed rigid bony (osseocartilaginous) median septum. Type II SCM consists of two hemicords within the same dural tube separated by a nonrigid, fibrous median septum. Type I SCMs are usually associated with cutaneous abnormalities at the level of the split, such as a tuft of hair, nevus, or hemangioma. Type II SCMs usually have no cutaneous abnormality at the level of the split, but spina bifida occulta is usually located in the lumbosacral region. In many instances, syringomyelia will be recognized on the preoperative magnetic resonance imaging (MRI) in association with the diastematomyelia. We generally plan to fenestrate the syrinx at the time of untethering if it is large and in the proximity of the diastematomyelia. Otherwise, it is recommended that the syrinx be followed with interval MRI scans. The syrinx rarely requires shunting and usually does not progress if the untethering is successful.
Patient Selection The diagnosis of SCM in the newborn usually occurs after the recognition of a midline cutaneous anomaly such as an intergluteal sinus or dimple, tuft of hair, hemangioma, cutis aplasia, or subcutaneous lipoma. It may also be seen in tandem with a myelomeningocele. The recognition of an asymmetrical lower extremity motor exam in the neonate born with a myelomeningocele should alert the clinician to the possibility of an associated SCM. These infants are often studied with spinal ultrasound, which may show a low-lying conus. After the first few weeks of life, ossification of the dorsal elements limits the use of ultrasound, therefore necessitating an MRI.
Loss of continence after toilet training, an associated history of constipation, and scoliosis are the most common symptoms beyond infancy. Complaints of intermittent back or leg pain evoked by exertion may be associated. These patients may have a normal neurological exam, but physical findings such as pes cavus deformity, calf wasting, atrophy of a gluteus muscle, asymmetry of foot size, lower sacral hypesthesia, and mild scoliosis may be common. Spinal radiographs may show spina bifida occulta and urodynamic studies should show evidence of a neurogenic bladder. If the children have been symptomatic for 6 months or less one can generally expect improvement in their symptoms. On the other hand, those symptomatic for 1 year or more may often have stabilization of their symptoms or deficits but may have less chance of neurological improvement. Once a child becomes symptomatic, the natural history is one of symptomatic progression. The best management for asymptomatic, neurologically normal children with incidental findings on imaging remains controversial. Whether these children undergo surgical correction or not, lifelong clinical followup is advised.
Preoperative Preparation Spinal radiographs show spina bifida occulta and widened pedicles and may define the bony spicule. Urodynamic studies commonly reveal a neurogenic bladder. Axial computed tomography (CT) scanning is important for the preoperative understanding of the bony anatomy. MRI may identify a thickened filum terminale and an associated syringomyelia, which will allow the surgeon to plan for an incision long enough for simultaneous sectioning of the filum and/or fenestration of the syrinx if it is large and in the proximity of the SCM. Careful evaluation of the imaging studies preoperatively is necessary to determine the SCM type and location of the separation of the hemicords and the bony septum. CT myelography may be necessary to visualize a meningocele manqué or a fibrous band between the two hemicords. All children should receive an antimicrobial bath the night prior to surgery. Perioperative antibiotics are given prior to the incision.
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Surgical Technique
The anesthesiologist should use a short-acting muscle relaxant during induction to allow for intraoperative stimulation of nerve roots if necessary and recognition of a motor response in inadvertent stimulation of the nerve roots. Intraoperative spinal cord monitoring may be of value during this repair.
Extensive preparation and draping should be performed to allow for extension of the incision as needed or placement of a second incision if the filum terminale is located a distance from the SCM. A midline incision is made down to the level of the thoracolumbar fascia (Fig. 21–1). The laminae at this level are always malformed and often incomplete. Careful dissection through the fascia and exposure of the bony anatomy is required to avoid inadvertent penetration through an incomplete arch and damage to the spinal cord. Laminectomy at the level of the malformation, one level above and one level below, is often adequate for the repair. The dura of both hemicords is then exposed (Fig. 21–2A). The canal at this level is normally quite wide. The bony septum of the SCM can be quite vascular, which is easily controlled with bone wax and Gelfoam. The bony septum is then removed with a small rongeur (Fig. 21–2B) or a highspeed drill (Fig. 21–2C) down to the posterior longitudinal ligament. A diamond bur helps to minimize bleeding from the septum. If there is a thickened filum causing tethering of the spinal cord, it should be sectioned at the same setting. This may require a separate incision and laminectomy depending on the location.
Operative Procedure Positioning After securing the endotracheal tube and placement of a Foley catheter, the patient is placed in the prone position on chest rolls extending from the chest to the iliac crest. This prevents abdominal compression and secondary distension of the epidural venous plexus, thus decreasing venous bleeding. The arms are placed on arm boards and all pressure points are padded. The patient is then placed in a slight Trendelenburg’s position to prevent excessive loss of cerebrospinal fluid during the procedure.
Figure 21–1 A midline skin incision (dashed line) is made over the level of the diastematomyelia. Note the accompanying thickened filum terminale, which may require a second incision. 10.1055/978-1-60406-039-3c021_f001
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A
B
C Figure 21–2 (A) Removal of the dysmorphic laminae allows exposure of the diastematomyelia. Periosteal elevators and other dissecting instruments should be used with care because the laminar arches may
Next, the dura is opened in the midline above the level of the malformation, ellipsing the defect, leading into a midline dural incision below the level of the defect (Fig. 21–2D). The ventral segment of the dura separating the two hemicords is approximated, if possible, with fine prolene sutures and inverted knots. This is done in an effort to recreate the floor of the spinal canal (Fig. 21–2E) and prevent the regrowth of the bony septum in a young child. Next, the hemicords are
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be incomplete. (B) The dorsal portion of the diastematomyelia septum is removed with a fine rongeur. (C) A high-speed air drill is used to bur away the residual septum of bone. (continued)
explored for tethering adhesions ventral and dorsal, which are taken down with sharp dissection using microscissors and/or a knife. Strict hemostasis is obtained, the intradural space is irrigated with saline, and the dura is closed with 4–0 Gore-Tex suture (Fig. 21–2F). This creates one thecal sac containing both hemicords (Fig. 21–2G). The epidural space is irrigated with bacitracin in saline. The epidural veins are coagulated as necessary for hemo-
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G Figure 21–2 (continued) (D) Once the septum has been removed, the dura is opened in an elliptical fashion. (E) The ventral dura is closed primarily when possible. (F) Completion of dorsal dural closure. (G) After
the ventral and dorsal incisions are closed, the two hemicords are contained within a single thecal sac.
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146 Pediatric Neurosurgery stasis and a Valsalva maneuver is performed to ensure watertight closure of the dural repair. A dural sealant may be used as well. Next, layered closure of the paraspinous muscle and fascia is performed with interrupted absorbable sutures. The subcutaneous tissue is approximated with absorbable sutures. The skin is closed with absorbable suture and covered with Dermabond (Ethicon Inc., Somerville, NJ).
neurological status. It is important to remember to place all patients on a stool softener as constipation secondary to narcotic medications is a common complication. Once postoperative muscle spasm has resolved in the child presenting with scoliosis, a repeat x-ray of the spine will generally show several degrees of improvement in the scoliosis. This improvement may be significant enough to obviate the need for spinal instrumentation.
Postoperative Management Including Possible Complications
Acknowledgment This chapter is a revision of the chapter, “Repair of Diastematomyelia” by Frederick A. Boop, M.D., and William M. Chadduck, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 3, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank William M. Chadduck, M.D., for his help and efforts on the original chapter published in the first edition of this work.
If anesthesia support is available, an epidural catheter may be placed under direct visualization at the time of closure to allow for postoperative pain control and potentially earlier mobilization. This catheter may then be removed after 24 to 48 hours, once pain is controlled by oral and/or intravenous medications. The patient is kept in the horizontal position for 24 to 48 hours postoperatively, thereby preventing spinal headaches. The patient is discharged once at baseline
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22 Lipomyelomeningoceles Frederick B. Harris, Naina L. Gross, and Frederick A. Boop
Patient Selection
Anesthesia Considerations
A lipomyelomeningocele is a subcutaneous lipoma that passes through a midline defect in the lumbar fascia, vertebral neural arch, dura, and meninges associated with an abnormally low spinal cord. It is believed to be caused by a failure of dysjunction of the cutaneous and neural ectodermal layers during secondary neurogenesis. More than 50% of patients will present with a midline cutaneous abnormality overlying the defect, 30% with bladder problems, and 10% with orthopedic deformities and/or neurological deficits in the lower extremities. Most patients are diagnosed at or before birth. Spinal ultrasonography or magnetic resonance imaging (MRI) should be performed on newborns with a subcutaneous lipoma or midline cutaneous birthmark. In infants with normal neurological function, MRI can be delayed until just prior to elective surgery. The appropriate timing of surgery is still debated; however, it has been said that all children by the age of 6 years will have some neurological deficit if the lipomyelomeningocele is not repaired. This remains contentious. It is clear that prophylactic surgery should be entertained only if the risk of surgical complications is small. For those who remain unrepaired, close neurological and urological follow-up is mandatory. It is not uncommon to see newly diagnosed patients present with neurological deterioration in their fourth or fifth decade of life.
The anesthesiologist should use a short-acting muscle relaxant during induction and no muscle relaxant during the surgery to allow for intraoperative stimulation of nerve roots. This also allows for the recognition of motor responses in inadvertent stimulation of nerve roots. Intraoperative monitoring of spinal cord, bladder, or rectal sphincter should be considered during the procedure.
Preoperative Preparation MRI of the entire spine should be performed to rule out other associated abnormalities of the spine and better define the levels of exposure needed, as intradural extension of the lipoma may progress several segments rostral to the point of dural penetration. Although ultrasound is a good screening tool, it does not define the needed anatomical detail in preparing for surgery. Plain films of the spine will likely show spina bifida, fusion abnormalities, and sacral defects in most cases. However, computed tomography (CT) and plain films add little additional information to that supplied by high-resolution MRI. All patients should have a detailed preoperative urological evaluation to document any voiding deficits. This is true whether or not there is a clinical history of voiding dysfunction. There is no longer a role for myelography in the evaluation of these children.
Operative Procedure Positioning After securing the endotracheal tube and placement of a Foley catheter, the patient is placed in the prone position on rolls extending from the chest to the iliac crest. This prevents abdominal compression and secondary distension of the epidural venous plexus, thereby decreasing venous bleeding. The arms are placed on arm boards and all pressure points are padded. The patient is then placed in slight Trendelenburg’s position to prevent excessive loss of cerebro-spinal fluid (CSF) during the procedure.
Surgical Technique Following sterile preparation, the skin is covered with an iodine-impregnated drape allowing for extensive caudal to rostral exposure. The skin incision begins midline and cephalad to the subcutaneous lipoma continuing inferiorly, ellipsing the mass. This allows for removal of excessive skin and adipose tissue (Fig. 22–1). The incision returns to midline caudal to the mass and is extended low enough to expose the cauda equina below the lipoma. Dissection of the subcutaneous lipoma is then performed down to the lumbar fascia (Fig. 22–2A). It is important during the dissection to provide only light retraction on the lipoma as the mass is attached to the dorsum of the spinal cord. The lipomyelomeningocele is then amputated at its area of fascial penetration (Fig. 22–2B). Occasionally, neural elements may extend up into the lipoma, as is seen in a lipomyelocystocele. Therefore, care should be taken to study the preoperative MRI and during the dissection to avoid amputating neural elements should they extend above the level of the fascia.
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Figure 22–1 An elliptical skin incision (dashed lines) allows for easy removal of the subcutaneous lipoma and later skin closure without redundant tissue. 10.1055/978-1-60406-039-1c022_f001
Understanding that neural arches will be malformed or incomplete, the lumbar fascial attachments to the lipoma are carefully dissected free and the fascia is opened in the midline caudal to the mass. The lamina is then exposed with meticulous dissection, avoiding inadvertently passing an instrument through a defect. A laminectomy is then performed both rostral and caudal to the dural defect created by the lipoma. Once normal-appearing dura is encountered, the dissection continues in the epidural plane to the area of abnormality. Similarly, normal dura can be exposed caudally and dissected up to the defect. Once the epidural space both rostral and caudal to the lipoma is defined, the dura is then opened with a scalpel in the midline rostral to the lipoma. Dural sutures are then placed for retraction of the dura. The dural opening is then extended to the stalk and dura-lipoma interface is defined with microdissection. In the case of a terminal lipoma, the stalk will appear as a fatty extension of the spinal cord, taking the place of the filum terminale. In such cases, the nerve roots are usually free both ventral and lateral to the lipoma. Once the nerve roots are clearly identified, the lipoma may be surgically removed at its exit from the dorsal defect in the thecal sac. During the dissection the use of a nerve stimulator may
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prove valuable in differentiating aberrant nerve roots from scar tissue. Rectal sphincter electromyography (EMG) and pudendal nerve monitoring may also be of use. In other cases, the so-called dorsal lipoma usually attaches to the dorsum of the spinal cord, just rostral to the conus medullaris. Dorsal lipomas may occur anywhere along the spinal cord and have been seen in the cervical and thoracic regions as well. The nerve roots will typically exit ventral to the lipoma. It is not unusual for nerve roots to infiltrate the lipoma or be adherent to the undersurface of the lipoma. Again, intraoperative neurophysiological monitoring can be of help in distorted anatomy. Remembering that one is working over the spinal cord; the use of intraoperative somatosensory evoked potentials may be useful as well. These lipomas may at times extend several centimeters rostrally or distally within the pia of the normal spinal cord. In such cases, their expansion may act like an intramedullary spinal cord tumor, causing injury by compression. The recognition of this pathology may require one to perform a myelotomy, following the lipoma and debulking it with the laser to completely decompress the involved spinal cord. The untethering requires meticulous dissection of the nerve roots from the mass with the use of microscissors and
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A
B Figure 22–2 (A) After the skin incision has been made, the subcutaneous lipoma is dissected free from the underlying thoracolumbar fascia. Caution should be used in retracting upon the subcutaneous lipoma because it is attached to the spinal cord. (B) Once the penetration of
irrigating bipolar forceps (Fig. 22–2C). An ultrasonic aspirator or contact yttrium-aluminum-garnet (YAG) laser is useful for careful and meticulous debulking of the lipomatous remnants (Fig. 22–2D). Once again, caution must be taken as the tran-
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the lipoma through the fascial defect has been defined, the subcutaneous mass can be removed and the remaining stalk followed through the fascial and dorsal dural defects. (continued)
sition from lipoma to neural tissue is indistinct; therefore, conservative partial resection is preferred (Fig. 22–2E). Care must be taken to completely free the lipoma from the dural attachments to allow for successful untethering.
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C
D
E Figure 22–2 (continued) (C) Microscissors and bipolar coagulation are used to debulk the intradural mass. (D) Because the residual lipoma attaches to the neural elements, the CO2 laser is used to vaporize the
remaining fatty tissue. (E) There is an indistinct blending of fibrous and neural tissue at this juncture, and conservatism at this point is wise.
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22 Transitional lipomas are a mixture of the dorsal and terminal variants with the rostral portion mimicking the dorsal variant with a transition ventrally as one moves caudally in the canal. In such cases, the conus is often bulbous or misshapen. These are particularly difficult as the nerve roots exiting the malformed conus often travel through the lipoma and are intermingled with the fatty tissue. They may be long on one side and short on the other. In some instances, these malformed roots may even serve as a source of tethering. Transitional lipomas at times may be too extensive to allow for safe untethering of the patient. In the patient with minimal deficits, one must at times terminate the procedure rather than risk injuring the child. Once the lipoma has been debulked, careful inspection of the cauda equina is performed. This allows for lysis and removal of adhesions that could potentially cause tethering. Sectioning of the filum terminale should be performed if it appears to have an abnormal or thickened appearance. Meticulous hemostasis is achieved and irrigation of the intradural space performed. The dura is closed primarily if there is redundant tissue. Otherwise, a dural patch should be placed with interrupted 4–0 Gore-Tex sutures. After watertight closure of the dura, irrigation of the epidural space is performed with bacitracin in saline. A Valsalva maneuver is performed to assess the dural closure. A dural sealant may then be placed over the suture line to lessen the risk of a spinal fluid leak. The fascia is then closed with interrupted absorbable sutures. The subcutaneous tissues are also closed in a watertight fashion with interrupted Vicryl sutures. Finally, the skin is closed with interrupted 4–0 Surgilon sutures or 4–0 Vicryl Rapide. Dermabond (Ethicon Inc., Somerville, NJ) skin glue is placed over the incision to prevent soilage.
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Postoperative Management Including Possible Complications If the dural closure is tenuous, the patient should be nursed in the horizontal position for 48 to 72 hours postoperatively. This will theoretically avoid spinal headaches and will allow the suture lines to begin healing without any additional stress. The Foley catheter is left in place while the patient remains flat. Once removed, the patient may require intermittent catheterization if voiding is difficult to initiate. Bladder function almost always returns to normal within 1 week of surgery. It is important to begin stool softeners postoperatively to avoid constipation and straining at stool. Some patients may have paresthesias or dysesthesias in the lower extremities during the first few postoperative days, which generally resolve in a few days in the pediatric population. In adults, this neuropathic pain tends to persist and can be very problematic. Acknowledgment This chapter is a revision of the chapter, “Repair of a Lipomyelomeningocele” by Frederick A. Boop, M.D., and William M. Chadduck, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 3, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank William M. Chadduck, M.D., for his help and efforts on the original chapter published in the first edition of this work.
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23 Untethering of the Spinal Cord after a Previous Myelomeningocele Repair Frederick B. Harris, Naina L. Gross, and Frederick A. Boop
Patient Selection The optimal timing of surgery for untethering of the spinal cord following the repair of a myelomeningocele in infancy is unclear. However, the development of severe pain, progressive neurological deficit, changes in bowel and bladder function, formation of a syrinx, and progressive scoliosis are specific reasons to investigate possible spinal cord tethering. It is agreed that the chance for functional recovery following untethering is best correlated with the duration of symptoms prior to surgery. Patients with a few months durations of symptoms can expect functional improvement following untethering. On the other hand, those with more long-term symptoms tend to have only stabilization of their disease following surgery. Therefore, it is important that these patients be enrolled in a multidisciplinary program utilizing the services of neurosurgery, orthopedics, urology, developmental pediatrics, and rehabilitation to allow for early detection of symptomatic and functional change. One must also keep in mind that the above symptoms of a tethered cord may also be caused by a nonfunctioning ventriculoperitoneal shunt. This is particularly true of the child who develops syringomyelia. In such cases, the central canal of the spinal cord may dilate preferentially over the ventricle of the brain. Performing an untethering operation on a patient with a nonfunctioning shunt carries the risk of brain herniation. The functionality of a shunt must be confirmed prior to any spinal surgery. The computed tomography (CT) scan of such patients can be deceiving in that slit ventricles do not always signify a properly functioning shunt. Therefore, at times, surgical exploration of a shunt may be prudent.
Preoperative Preparation In addition to evaluating shunt function, we will generally review a high-resolution magnetic resonance imaging (MRI) scan of the entire spine prior to untethering the lumbar spine. Several children with spina bifida cystica will have tandem lesions such as a split cord malformation higher up in the spine. If this has not been evaluated, one may find that the more rostral lesion is actually the cause of the tethering rather than the myelomeningocele. Likewise, a good set of plain spine x-rays is essential to evaluate which laminar
arches are intact and which are dysplastic. A standing spine film will also allow measurement of scoliotic curves, which can be compared following untethering to determine if the curves are improved. At most pediatric institutions, latex precautions are now routine for spina bifida patients. This is critical even for children with no real history of a reaction to latex. In days past the author has had patients anaphylax and die from this exposure. As such, it is standard ward and operating room precaution to avoid latex in all children with spina bifida, with a history of latex sensitivity, and who manage their bladders with clean intermittent catheterization.
Operative Procedure The patient is placed in the prone position on chest rolls with all pressure points padded, paying particular attention to areas of denervated skin to avoid formation of pressure sores. Patients with contractures are positioned with extra bolstering as needed. The use of latex precautions has become routine. Once again, the patient is placed in a slight Trendelenburg’s position to avoid excessive drainage of cerebrospinal fluid (CSF). The back is prepped and draped in a normal sterile fashion. The previous surgical scar is identified. A preoperative MRI will delineate the anatomy. The repaired neural placode is usually adhered to the dorsum of the spinal canal just beneath the skin. Therefore, the previous incision is opened in a very delicate and meticulous fashion to avoid injury to any neural elements (Fig. 23–1). For this reason, the skin should not be infiltrated with lidocaine and epinephrine. After opening the skin incision, dissection begins at the first spinal level rostral to the placode. Either a laminectomy or a partial laminectomy is performed above the defect to expose normal dura. Dissection then proceeds distally in the epidural plane to the area of malformation. In some cases, the dura cephalad to the placode may need to be opened due to difficulty identifying the epidural space. This is performed to identify normal spinal cord (Fig. 23–2A). Care should be taken when opening the dura in this location because the spinal cord is likely adherent to the dorsum of the thecal sac. Once the dura is entered cephalad, the neural elements can be dissected intradurally inferior to the region of the previous surgical repair. Microsurgical technique and care-
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Figure 23–1 The scar from the previous myelomeningocele repair may either be revised or reopened to the level of the subcutaneous fat. In a thin patient, care should be exercised at the time of incision of the skin because the neural elements may be just beneath it. 10.1055/978-1-60406-039-1c023_f001
ful hemostasis must be used when performing this dissection (Fig. 23–2B). The area over the dorsum of the placode is the most difficult area of the dissection; however, it is important that a dural layer and a fascial layer be identified to later facilitate a watertight closure. The nerve roots will be located lateral and ventral to the placode during dissection. Mobilization and lysis of adhesions of the adherent roots are often required. Large radicular vessels that may supply the placode and/or nerve roots should be spared. Careful inspection of the placode must be performed for the identification of any dermal inclusions. These are often present and may not be clearly identified on the preoperative MRI. When these dermal inclusions are present, they should be removed. If the inclusion is adherent to the placode, use of a contact yttrium-aluminum-garnet (YAG) laser may facilitate removal. The dissection is completed once the placode is dissected free and drops to the ventral aspect of the spinal canal (Fig. 23–2C). After the placode has been released, attention must then be focused on the thorough inspection and lysis of adhesions from the cauda equina. The filum terminale may also require sectioning for complete detethering. Thorough irrigation of the intradural space is performed with saline, and the wound is examined for hemostasis. The dura is closed primarily or a duroplasty may be required if the canal is compromised (Fig. 23–2D). It is important
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that the canal be patulent to avoid repeated scarring and tethering. The dura or dural substitute is closed with 4–0 Gore-Tex sutures. A dural sealant (DuraSeal) may also be applied to the suture line. The epidural space is irrigated with bacitracin in saline. The remaining layers are closed in a watertight fashion with interrupted sutures and the skin is closed with 4–0 Vicryl Rapide sutures.
Postoperative Management Including Possible Complications The patient is nursed in the horizontal position for 48 to 72 hours to prevent a spinal fluid leak through the wound and minimize the formation of a pseudomeningocele. Careful attention should be made to padding and protecting pressure points in these patients, who often have delicate skin. In patients with shunted communicating hydrocephalus, decompression of the thecal sac may lead to a shunt malfunction in the perioperative period; therefore, signs and symptoms of a malfunctioning shunt such as headache, nausea, vomiting, or lethargy should not be attributed to low spinal fluid pressure, postoperative pain, or narcotics. A spinal fluid leak through the previous scar tissue rarely occurs in the presence of a functioning shunt. If one can’t be sure on clinical grounds, one should have a low threshold
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A
10.1055/978-1-60406-039-1c023_f002 Figure 23–2 (A) The dissection is begun by defining normal dura and spinal cord at the level above that of the previous repair. This allows dissection of scar tissue from neural elements in defined planes. (B) The
for ordering a CT of the head to evaluate the shunt before increasing the pain medications. Likewise, patients with Chiari malformations have abnormal brain stem nuclei. In some patients, small amounts of narcotics may be sufficient to cause respiratory compromise or aspiration.
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B right side of the placode has been dissected away from the dura, and attention is now turned to the left side. Microinstruments prove very useful in this dissection. (continued)
Low-grade fevers and meningismus postoperatively may be explained by contamination of the spinal fluid with blood. However, high fevers should be evaluated by shunt tap to rule out bacterial meningitis. The Foley catheter is not removed until the patient is mobile. The patient should
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C
D
Figure 23–2 (continued) (C) Once dissected free, the neural placode will drop into the ventral aspect of the spinal canal, signaling that the dissection is complete. One must then inspect the cauda equina and section a thickened filum terminale if it exists. Meticulous bipolar hemostasis is achieved prior to dural closure. (D) A patulous dural closure may serve
to prevent repeated tethering of the neural elements. The authors prefer to use nonreinforced Silastic sheeting (Dow Corning, Midland, MI) for the closure because of its inert properties. The use of Dacron-reinforced Silastic for duraplasty should be avoided.
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156 Pediatric Neurosurgery return to his/her home catheritization schedule and bowel protocol. Acknowledgment This chapter is a revision of the chapter, “Untethering of the Spinal Cord after a Previous Myelomeningocele Repair” by Frederick A. Boop, M.D., and William M. Chadduck, M.D. The chapter
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appeared in the Neurosurgical Operative Atlas, Volume # 3, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank William M. Chadduck, M.D., for his help and efforts on the original chapter published in the first edition of this work.
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24 Brain Abscesses Darric E. Baty, Eli M. Baron, and Christopher M. Loftus
Brain abscesses, also termed cerebral abscesses, are focal infections of brain tissue that begin as early cerebritis and progress through four different stages, each with its own distinct histological characteristics. These abscesses are managed both medically and surgically; this chapter, however, will focus on the surgical management of brain abscesses.
Epidemiology The epidemiology of brain abscesses varies with location and socioeconomic status. In the United States, there are ~1500 to 2500 cases per year; in developing countries, the incidence is much higher. Some authorities feel that the overall incidence is increasing because of a larger population of immunosuppressed patients (e.g., AIDS, transplant recipients) who are living longer and acquiring opportunistic infections. The male to female ratio is 3:1 to 3:2. The reason for the higher occurrence in males is not known.
Risk Factors and Vectors Risk factors include congenital cyanotic heart disease (CCHD); pulmonary abnormality, from arteriovenous fistula to infection; AIDS or other immunocompromised state; penetrating head injury; bacterial endocarditis; gastrointestinal infection; dental abscess or recent odontogenic manipulation; previous infarction or ischemia in the setting of septic emboli in the brain; meningitis; sinusitis; and neurosurgical procedure, including placement of intracranial pressure monitor, ventriculostomy, and halo traction devices. In the pediatric population, the increased hematocrit and diminished arterial partial pressure of oxygen (pO2) associated with CCHD, especially tetralogy of Fallot, put the patient at an estimated risk of brain abscess that ranges from 4 to 7%. In addition, those with left-to-right shunts do not have the advantage of the filtering effects of the lungs and are more susceptible to cerebral abscesses. Patients with RenduOsler-Weber’s syndrome often have pulmonary arteriovenous fistulae. The lifetime risk of developing a brain abscess in patients with pulmonary arteriovenous fistulae is ~5%. In adults, the most common source for brain abscess is the lung. Specific entities include pulmonary abscess, bronchiectasis, and empyema. Acute endocarditis is more likely
to predispose to a cerebral abscess than the subacute form, but brain abscess in the setting of endocarditis is overall a rare finding. An odontogenic source is usually considered only in patients who have had procedures in the previous 4 months or who are found to have dental abscesses. There are three primary vectors for cerebral abscess: hematogenous spread, contiguous spread, and development following cranial trauma or a neurosurgical procedure (Fig. 24–1). With the advent of improved antibiotics, the most common vector has changed from the contiguous route (prior to 1980) to the hematogenous one. No source can be identified in up to 25% of cases, and dental sources may spread via the hematogenous or the contiguous route. Hematogenous dissemination to the brain and subsequent abscess formation result in multiple intracranial abscesses in ~10 to 50% of cases. In AIDS patients, the occurrence of pyogenic cerebral infection is relatively rare, and the same organisms affect these patients as the general population. Contiguous spread of infection into the brain usually originates from purulent sinusitis. Local osteomyelitis and emissary vein thrombophlebitis play a pivotal role in allowing transmission from the inside of the sinus cavities to the cerebral surface. Abscesses disseminated via this route are practically always singular, and they are uncommon in infants because they do not have aerated paranasal or mastoid sinuses. Temporal lobe and cerebellar abscesses typically come from mastoid air sinus and middle ear infections. Chronic otitis media in an adult portends a 1:10,000 risk of brain abscess formation per year, which can be significant over the person’s lifetime if left untreated. Nasal sinusitis leads to frontal lobe abscesses, whereas sphenoid sinus infection may spread to the cavernous sinus, with potentially devastating results. Neurosurgical procedures traversing air sinuses have an increased incidence of intracranial abscess formation, as do penetrating traumatic injuries, particularly with persistent cerebrospinal fluid (CSF) leaks not repaired surgically. Open skull fractures are associated with a 3 to 7% risk of cerebral abscess development. Simple aspiration is usually inadequate for abscesses that follow penetrating injuries—open debridement and removal of dead tissue is required; bone fragments may serve as niduses of infection in this setting. Even simple neurosurgical procedures, such as halo ring placement, may be complicated by brain abscess formation.
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Figure 24–1 Brain abscesses have several possible sources. Direct extension via mastoid, middle ear, or paranasal sinus infection and hematogenous spread from septic emboli and periodontal abscesses are recognized methods of dissemination.
Pathogens The organisms most commonly isolated from brain abscess cultures are Streptococcus species; many of these (33 to 50%) may be of the anaerobic or microaerophilic variety. No organism is cultured in up to 25% of cases. In 10 to 30% of cases, the cultures may grow multiple organisms, typically including anaerobes such as Bacteroides species. Common clinical sources for polymicrobial culture results are otitis media, mastoiditis, and lung abscess. When abscess formation is secondary to frontal or ethmoidal sinusitis, Streptococcus milleri and Streptococcus anginosus are frequently found. Following trauma, the most common organisms demonstrated are Staphylococcus aureus and Proteus species. In immunocompromised hosts, fungal infections from Aspergillus fumigatus pulmonary infections are commonly implicated, and infections from Toxoplasma gondii, Nocardia species, and Mycobacterium tuberculosis are also seen. Gram-negative or-
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ganisms are frequently seen in infants because IgM doesn’t cross the placenta.
Patient Selection Presentation In newborns, seizures, irritability, increasing occipitofrontal circumference secondary to patent sutures, failure to thrive, and meningitis are common presenting conditions; most newborns are not febrile but do not tend to do well. Papilledema is rare prior to the age of 2. In adults, signs or symptoms of increased intracranial pressure, including headache, nausea, emesis, and lethargy, are common but nonspecific for brain abscess. Edema surrounding the lesion often is responsible for, or at least contributory to, the symptomatology. High fevers are unusual, but low-grade
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24 Brain Abscesses 159 fevers can be seen. Altered mental status, from confusion to coma, can occur. Seizures and hemiparesis develop in 30 to 50% of cases.
Evaluation Blood work may be abnormal but is typically nonspecific for cerebral abscess. The peripheral white blood cell count (WBC) is significantly elevated in only 30 to 40% of patients and blood cultures are usually negative. Erythrocyte sedimentation rate (ESR) may be normal, especially in CCHD where the ESR is lowered by polycythemia. C-reactive protein (CRP) is also nonspecific, and levels can be elevated in brain tumors and abscesses elsewhere in the body. CSF analysis was abnormal in >90% of cases where lumbar puncture (LP) had been performed in patients with brain abscesses. The CSF findings are not diagnostic for abscess, and an organism is identified in only 6 to 22% of cases. The opening pressure is typically elevated, and there may be elevation of the WBC and protein. In the setting of known cerebral abscess, an LP is relatively contraindicated due the risk of transtentorial herniation. Computed tomography (CT) scanning approaches 100% sensitivity for detection of brain abscesses. The four characteristic stages are: early cerebritis (stage I) during the first 3 days; late cerebritis (stage II) during days 4 to 9; early capsule formation (stage II) from days 10 to 13; and late capsule formation (stage IV) from 2 weeks and onward. Steroids tend to prolong the evolution of this process and reduce the degree of contrast enhancement. Late cerebritis and early capsule formation can be difficult to distinguish. Late cerebritis tends to be more ill-defined and to have thick ring enhancement, whereas early capsule formation has a faint rim on precontrast studies and thin ring enhancement. Delayed scans taken 30 to 60 minutes after the contrast bolus is administered can also aid in the determination; lack of decay of enhancement is indicative of late cerebritis, whereas decay of enhancement is more typical of capsule formation. Magnetic resonance imaging (MRI) can also be used to image cerebral abscesses (Fig. 24–2). In the cerebritis stages, the affected region is hypointense on T1-weighted imaging (T1WI) and hyperintense on T2-weighted imaging (T2WI). After capsule formation, T1WI is usually hypointense in the center and in the perilesional edematous region, and mildly hyperintense along the rim; the T2WI is typically isointense or hypointense in the center with a well-defined rim, and hyperintense in the perilesional edematous region. Many times it can be difficult to radiographically distinguish cerebral abscess from a necrotic neoplasm. Brain abscesses usually have less edema associated with them than high-grade necrotic neoplasms such as glio-blastoma multiforme. Spectroscopic evaluation reveals abundant lactate and mobile lipids, as well as several amino acid signatures that are not seen with necrotic neoplasms. Diffusion-weighted imaging (DWI) may be even more useful: Abscesses have restricted diffusion, a hyperintense signal, and a low apparent diffusion coefficient (ADC), whereas necrotic tumors have a hypointense signal and an elevated ADC.
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In the rare instances where contrast-enhanced CT and MRI are nondiagnostic, or cannot be performed because of contraindications, WBC scintigraphy with technetium-99m (99mTc) is an excellent option, with a reported sensitivity and specificity of 100%. This is a tool that may also be useful for detecting recurrent abscesses, especially following surgery when the CT may be more obscured than usual with postoperative changes.
Medical versus Surgical Treatment Almost every patient should receive the benefit of combined medical and surgical treatment modalities. If possible, cultures should be obtained before the administration of antibiotics to improve the chances of identifying the organism and subsequently tailoring the therapies appropriately. Certainly, patients with lesions >2.5 cm should undergo surgery. Even poor surgical candidates with normal bleeding parameters can usually tolerate a stereotactic biopsy under local anesthesia.
Preoperative Preparation In cases where surgery is delayed and empiric antibiotics must be started, there is no one single correct treatment regimen, but it is advisable to provide broad coverage. The combination of vancomycin, a third-generation cephalosporin such as cefotaxime, and metronidazole (or chloramphenicol) is a reasonable initial treatment strategy. Metronidazole (or chloramphenicol) may be substituted with a one-time dose of rifampin for posttraumatic abscesses. In patients with AIDS, empiric treatment should incorporate sulfadiazine and pyrimethamine to include Toxoplasma gondii in the targeted spectrum of organisms. The use of steroids in the treatment of intracranial abscesses remains controversial. In general, if the patient exhibits signs or symptoms of elevated intracranial pressure and has a mass lesion on CT, steroids are administered even though they may inhibit host defenses and reduce penetration of antibiotics into the abscess cavity. With up to half of patients with brain abscesses experiencing seizures, prophylactic anticonvulsants are recommended. Phenytoin is generally loaded and administered to maintain therapeutic levels, unless the patient has a known contraindication. Phenobarbital may be used in a similar fashion, but it is typically more sedating, which is, of course, not desirable in the setting of an intracranial lesion.
Operative Procedure The two primary surgical options are needle aspiration and surgical excision. Needle aspiration can be performed using frame-based or frameless stereotaxy, or intraoperative ultrasound guidance (Fig. 24–3). Stereotactic methods tend to be less invasive, usually necessitating only a twist drill hole or a bur hole, whereas ultrasound guidance is typically performed with a generous-sized bur hole or a small craniotomy. There is a high reoperation rate, approaching 70% in
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Figure 24–2 A left apical molar abscess was the infectious source for the left temporal brain abscess in this male patient. The patient underwent a left posterior temporal craniotomy for excision of the abscess; microaerophilic streptococci grew from the intraoperative culture. (A) Preoperative axial T1-weighted magnetic resonance image demonstrating a left 10.1055/978-1-60406-039-1c024_f002
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posterior temporal lobe cystic lesion. (B) Gadolinium enhancement was seen at the periphery of the lesion. (C) The T2-weighted image showed marked edema surrounding the lesion. (D) Postoperative imaging, including this post-gadolinium T1-weighted scan, demonstrated postoperative changes and resolution of the abscess.
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Figure 24–3 Ultrasound guidance allows needle aspiration of the abscess, permitting removal of purulent material for culture and aiding in decompression of the mass, which facilitates dissection of the capsule. 10.1055/978-1-60406-039-1c024_f003
some series, for lesions treated with needle aspiration. Excision is reserved for well-encapsulated, solitary lesions in accessible locations, Nocardia abscesses, and posttraumatic abscesses associated with a foreign body; the length of antibiotics can be shortened, to about 3 days in some cases of total removal. Appropriately resected lesions have a much lower recurrence. General anesthesia is administered with typical intracranial precautions, unless the patient’s medical condition mandates use of local anesthetics exclusively. Hyperventilation and mannitol should be available for use as needed. Intraoperative steroids can be administered, as well as additional anticonvulsant, if the preoperative level is low or not available. The location of the abscess and the technique employed largely dictate the patient’s specific positioning. If feasible, the head of the table should be elevated; the patient is regularly placed in the Mayfield skull clamp (Integra LifeSciences Corporation, Cincinnati, Ohio), unless frame-based stereotaxy is being employed, permitting rigid immobilization and an attachment site for the Greenberg retractor system. Appropriate maneuvers are performed to ensure adequate venous drainage. The patient’s operative site is shaved, prepped, and draped in the usual sterile fashion. The skin incision and bone work are tailored to the planned procedure (e.g., a small stab incision for a frame-
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based stereotactic surgery or a multicentimeter curvilinear incision for a small craniotomy). If ultrasound guidance is utilized, the dura is flooded with irrigation and the region is scanned with the probe to ascertain the center point for the dural incision, directly over the abscess (Fig. 24–4). After reflecting the dura and localizing the lesion once again with ultrasound (Fig. 24–5), a brain needle is passed into the abscess cavity and the contents are aspirated, decompressing the lesion to aid in further dissection while also acquiring a specimen for cultures and stains (Fig. 24–6). If complete resection is indicated, the procedure is carried forward, as below; otherwise, the operative field is irrigated copiously, hemostasis is obtained, the dura is closed, the bone flap is secured, and the galea, subcutaneous tissues, and skin are reapproximated. When complete resection is indicated, a corticectomy is made directly over the abscess capsule, utilizing ultrasound guidance. Gentle suction and retraction are applied until the capsule is identified. Cottonoids are used to help define the plane between the capsule wall and the brain and to protect the brain surface (Fig. 24–7). The capsule is removed in its entirety following circumferential dissection and is sent for pathological and microbiological examination (Fig. 24–8). The resection cavity is irrigated, and all foreign material is removed. The closing is completed in routine fashion.
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10.1055/978-1-60406-039-1c024_f004 Figure 24–4 Ultrasound guidance allows accurate planning of the dural flap after the craniotomy has been performed.
Postoperative Management and Outcomes Antibiotic coverage must be adjusted to reflect new stain and culture data. Unless gross total resection of the abscess and capsule was performed, intravenous antibiotics are typically continued for 4 to 12 weeks (most commonly 6). A peripherally inserted central venous catheter or Hickman catheter is usually necessary. Steroid medication is quickly tapered. Anticonvulsants are frequently continued for 1 to 2 years. Routine head CT should be acquired at 1 and 2 weeks following surgery, and emergently if the patient deteriorates. As CT findings lag behind clinical resolution,
head CT scans need to be followed every 2 to 4 weeks after the full course of antibiotic therapy until radiographic resolution, then every 2 to 4 months for 1 year. Emergent CT is obtained for any patient presenting with neurological deterioration.
Outcome Five to 20% of abscesses recur within 6 weeks of discontinuation of antibiotic therapy. The modern mortality rate for brain abscess is ~10%, but for fungal abscesses in transplant recipients the rate rises to almost 100%. Neurological disability is present in 45% of patients, and 29% have residual
10.1055/978-1-60406-039-1c024_f005 Figure 24–5 The ultrasound probe is again used to locate the abscess and plan the corticectomy. Note that the medial reflection of the dural flap protects the sagittal sinus whenever craniotomies close to the midline are used.
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10.1055/978-1-60406-039-1c024_f006 Figure 24–6 Internal decompression of the mass is performed with a brain needle. The purulent material is sent to the laboratory for cultures and sensitivity testing.
10.1055/978-1-60406-039-1c024_f007 Figure 24–7 The abscess capsule is prepared for removal using a combination of gentle suction, dissection, and progressive retraction, following the corticectomy. The neighboring cortex is protected with cottonoids.
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10.1055/978-1-60406-039-1c024_f008 Figure 24–8 Excision of the capsule is performed following circumferential dissection by gently elevating and then freeing it from the underlying cortex.
hemiparesis. Late focal or generalized seizures are present in 27% of patients.
Conclusion Patients with brain abscesses have focal brain infections that progress through four histological stages and portend a relatively poor prognosis for full neurological recovery. Aggressive medical and surgical therapies are needed to provide the best patient care, and close persistent follow-up is required to find and treat recurrences, even after successful initial management.
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Acknowledgment This chapter is a revision of the chapter, “Surgical Management of Brain Abscess” by Timothy C. Ryken, M.D. and Christopher M. Loftus, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 3, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Timothy C. Ryken, M.D., for his help and efforts on the original chapter published in the first edition of this work.
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25 Unilateral Coronal Synostosis (Plagiocephaly) James Tait Goodrich and David L. Staffenberg
The surgical treatment of plagiocephaly (unilateral coronal synostosis) has undergone several technical changes over the last 50 years. Several different techniques, including strip craniectomies, lateral canthal advancement, facial augmentations, and others have been developed to treat this congenital disorder. This chapter will address the treatment of plagiocephaly using the bandeau/forehead reconstruction techniques.
Patient Selection Plagiocephaly is a common and easily recognized disorder caused by a premature fusion/sclerosis of one coronal suture. As a result of this premature fusion/sclerosis, the patient typically develops a flattening over the side of the involved suture with a compensatory frontal bossing of the contralateral forehead (Fig. 25–1). As a result of unequal growing planes, the child develops an orbital dystopia. When viewing the child frontally the orbit on the affected side is wider, whereas the orbit on the other side is narrower. This occurs by the frontal bone being pushed forward and down by the brain. In other words, when viewed frontally, the child appears to have one eye wide open and the other partially closed. To address the problem of plagiocephaly requires correcting the orbital dystopia, reducing the compensatory frontal bossing, and providing a symmetrical alignment of the forehead.
Preoperative Preparation Evaluation Children with plagiocephaly are commonly diagnosed at birth or at the least by 3 months of age. It is not uncommon for the pediatrician to typically follow these children for 3 to 6 months before calling upon the craniofacial team. Once the diagnosis of craniosynostosis is recognized, a series of diagnostic studies can be helpful in clarifying the diagnosis. A routine skull series, in most cases, will identify the sclerosed suture. A three-dimensional reformatted computed tomography (CT) scan is extremely helpful in the preoperative planning, plus it also documents the extent of suture synostosis. The head circumference is measured and closely followed to assess head growth. It is uncommon to have restricted head growth in a single suture closure, though it has been reported to occur in up to 10% of cases. It is common to see areas of digital markings on the inner table of the skull on CT indicating localized areas of increased intracranial pressure. These areas of pressure rarely become clinically significant in the younger child (i.e., <1year of age). As part of the preoperative evaluation, the patient and family are seen by all members of the craniofacial team, which includes the following: neurosurgeon, plastic surgeon, pediatrician, pediatric neurologist, geneticist, social worker, and the child life specialist. After each team member has seen the patient and family, a conference is held and the surgical recommendations to the family are planned.
Timing of Surgery Few subjects provoke as much discussion among craniofacial surgeons as the one on timing of the surgery. Initially we felt these children should be operated on as soon as possible, even as early as 2 to 3 weeks of age. We now prefer to wait until the child is 4 to 6 months of age. This allows for a more mature hematological system and a larger blood volume for the anesthesiologist. In addition, the calvarial bone is firmer with a more mature matrix allowing better contouring and placement. The 6 to 12 month age period is critical in the developing child. This is a period of rapid head growth, and this growth assists in the final remodeling of the child's head and face; therefore, it is critical to use this period of rapid growth to assist in the reconstruction.
Preparation A child with an isolated case of plagiocephaly is typically healthy and rarely has medical problems associated with a single suture synostosis. We routinely have the pediatrician do a well-baby checkup a day or two before the child is to be admitted. If the child comes in with a fever and workup shows no active bacterial infection (normal white blood cell count with no shift), we will proceed with surgery. If the child has a upper respiratory infection but no signs of congestion, we will also proceed. However, if the child appears septic or an active bacterial source is identified, then the surgery is canceled and rescheduled. Before we instituted this protocol nearly one-quarter of our patients were canceled on the day of surgery because of an unknown fever
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10.1055/978-1-60406-039-1c025_f001 Figure 25–1 Artist's rendering of a child with right side coronal craniosynostois (plagiocephaly). The area over the right coronal suture is flattened; a compensatory frontal bossing has occurred in the left forehead. The sphenoid wing also becomes deformed, giving rise to the “harlequin eye” seen on a anterioposterior skull x-ray.
source. We have reduced this figure to <5% with the above protocol. The parents are counseled on providing donor-directed blood from the family should they want to take advantage of this option. Due to potential blood loss all patients require at least two large-bore intravenous lines of 20 gauge or larger. Arterial lines are placed for monitoring blood gases, hematocrit, electrolytes, etc., during the procedure. A Foley catheter is placed to monitor urine output. We do not routinely use steroids or anticonvulsants. Antibiotics are used (oxacillin 50 mg/kg) beginning with a preoperative dose and performed for 24 hours.
parallel to the patient's side at foot level. The nursing team is placed on the opposite side at the foot of the patient. A small Mayo stand is placed over the patient's abdomen. A second mobile stand is placed off to the side for surgical trays. As multiple teams are involved in a staged fashion, several surgical trays are needed. Our nursing team has found it beneficial to keep a large table in the background with the various tray setups. As each surgical team comes into the field, their instruments are placed on the mobile table, and the working instruments needed are placed on the Mayo stand.
Skin Incision and Flap Elevation
Operative Procedure Positioning The patient is placed in a supine position with the head resting in a horseshoe headrest. This headrest allows some movement and repositioning of the head during the case. The draping is done so that the head is fully exposed from the nasal tip to vertex. A 180 degree access to the head and facial region is required so no stands are placed to either side of the head of the patient. The anesthesia team is placed
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A bicoronal incision is performed in a zig-zag fashion and carried from ear to ear well behind the hairline. In most children it is not necessary to shave the hair; rather, the incision can be carried through a parted hairline. The skin flap is elevated separately from the pericranium and carried down to the orbital rims bilaterally. Both orbitozygomatic sutures have to be exposed. The pericranium is then elevated as a second layer and also carried down to the orbital rims. The neurovascular bundle is identified at the supraorbital notch and elevated. There is often a thin rim of bone at the notch that can be easily opened with a fine osteotome. The dis-
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25 Unilateral Coronal Synostosis (Plagiocephaly) 167 section is then carried further around and under the orbital rims. At the completion of the skin incision and forehead flap, both orbital rims and zygomatic sutures are exposed. The temporalis muscles are elevated from their insertion point at the temporal line down to the level of the zygoma. The belly of the muscle is not incised as this will cause atrophy and later, a cosmetic deformity. The temporalis muscle is elevated with monopolar needle tip cautery on a lowcurrent setting and winged out on its base. The orbital rims are further dissected until the nasion suture is exposed. Laterally the orbital rims are dissected to the attachment of the lateral canthal ligament. We rarely detach this ligament except in severe cases of orbital dystopia. If this ligament is to be detached, an identification suture is placed through the ligament and then cut on the side closest to the orbital wall. This suture is key to locating and reattaching the ligament at the end of the operation.
Craniotomy and Craniofacial Reconstruction The two types of reconstruction we use in surgically correcting plagiocephaly are presented. In the younger child (<1 year) with malleable bone, we elevate the original orbital bandeau and then reshape it prior to replacement (Fig. 25– 2). In those cases where the bandeau is too deformed, a new bandeau is developed from over the calvarial vertex. (Figs. 25–3 and 25–4). In a plagiocephalic child, the forehead unit is almost always markedly deformed; therefore, a new forehead is marked out with a Marchac template. The osteotomy cuts are outlined (Fig. 25–3) and intraoperatively will be marked out with methylene blue. The team first makes the decision as to which type of craniotomy is to be performed, and then the appropriate marks are mapped out.
A Figure 25–2 (A) Technique for elevating the original bandeau and harvesting a new forehead from the right parietal region. (B) The bandeau and forehead have been plated (using absorbable miniplates) to make the “tiara” reconstruction. In this illustration the absorbable plates are
Fig. 25–2 illustrates a case where the original bandeau was elevated and a new forehead elevated from the right parietal region. The technique for elevating these units requires a round bur (e.g., Midas Rex M-33; Medtronic Inc., Ft. Worth, Texas) and a foot-plated craniotome (e.g., Midas Rex B-5). The new forehead is marked and elevated first. Superior cuts along the orbital rim are then made. The remaining original forehead unit is now elevated as a single piece taking care not to injury the sagittal sinus. Once this forehead unit is off, the frontal lobes are gently retracted exposing both orbital roofs and bilateral sphenoid wings. Osteotomies are made just behind the bandeau and carried over both orbital roofs and in front of the cribiform plate. The zygomatic arch is cut at the suture line. The nasal bone is cut at the nasion suture. Once the bandeau is freed up it is handed off to the plastic surgery team who construct a “tiara” bandeau and forehead (see insert on Fig. 25–2B). Typically one to three absorbable miniplates are used to reconstruct this unit; we now place these plates inside of the bone rather than on the outside. We have converted to this technique of placement to reduce the “palpable” contour of the plates under the skin. The neurosurgery team uses this interval to inspect for any dural or sinus tears, which must be meticulously closed. The bandeau and forehead are now replaced in a symmetrical fashion and tongue and groove to the temporal/squamosal bone. If there is an asymmetry in the squamosal bone, radial cuts can be made and the bone greensticked and outfractured. A bone strut is placed from the top of the tiara to the skull (Figs. 25–5 and 25–6). The two open areas, lateral to the strut, are now reconstructed with the remaining bone in a mosaic fashion. A Tessier rib bender is helpful in remodeling the bone. Split lamellar bone grafts are harvested from the inner table to
B on the “outside” of the bone. We now place the plates on the inside of the bone except at the lateral tongue-and-groove fixation points. By doing this we have reduced the postoperative complaints from parents, who can feel these plates through the skin.
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Figure 25–3 An intraoperative view showing the methylene blue markings for the osteostomies. The lack of a coronal suture can be appreciated on the right side, as well as the resultant deformity in the anterior fontanelle and metopic suture. A Marchac template has been used to mark out the new forehead, which is being taken from just above the bandeau. 10.1055/978-1-60406-039-1c025_f003
patch any remaining defects. In our experience, bone defects >1.5 to 2.0 cm will not close, particularly in the child >1 year of age. With the use of split-thickness bone grafts we now rarely leave any open bone defects. The bone units are secured into position with either 4–0 Nurolon or 3–0 Vicryl. We no longer use wire because of the risk of skin protrusion. Metal miniplates are no longer used in the child <3 years of age. We have moved away from the use of wire and metal miniplates because of unacceptable migration patterns in the growing child. The recently developed absorbable miniplates can be quite helpful, but again are used only in areas where extra structural support is needed. As can be seen in Fig. 25–5 we use absorbable sutures mostly to stablize the flaps. This technique has worked well for the last 10 years with no cases of bone displacement requiring further surgery. An alternative craniofacial technique is used when the original bandeau is too deformed to be reshaped. A new bandeau is harvested from high over the parietal convexity (Fig. 25–4). In this case the new forehead unit comes from just behind the bandeau. The dissection techniques and osteotomy cuts are the same as explained above. The original bandeau that is removed is cut up and used in the mosaic reconstruction.
Closure Technique Once the bone units have been stabilized, the operative field is copiously irrigated to removed bone dust, debris, and other potential sources of infection. The gutters formed
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A
B Figure 25–4 (A) Artist's rendering showing the technique for making a new bandeau, here harvested over the convexity. The new forehead is coming from the vertex, just behind the bandeau. Also shown in outline are the deformed skull sutures and anterior fontanelle. (B) An intraoperative view showing the frontal bandeau and new “Marchac” forehead. The orbital rims can be appreciated in the bandeau, which has been recontoured to make it more symmetrical. The forehead was harvested using a Marchac metal template (see Fig. 25–3). 10.1055/978-1-60406-039-1c025_f004
where the skin flaps have been folded over need particular attention, as a good deal of debris collects here. The pericranium is reelevated and tacked into position with several absorbable sutures. The temporalis muscles are reattached to the pericranium. This technique is an
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10.1055/978-1-60406-039-1c025_f005 Figure 25–5 Intraoperative photograph after the reconstruction (see Fig. 25–6). In this case we have used mostly absorbable sutures instead of wire and metal plates. We also now use only absorbable miniplates in cases where extra stabilization is needed, and they are placed inside of the craniotomy.
10.1055/978-1-60406-039-1c025_f006 Figure 25–6 The reconstruction completed with the tiara replaced. A strut unit of bone is placed from the top of the tiara to the skull; this is a key structural unit for stabilization. The lateral sides of the strut are then filled in with the remaining bone in a mosaic fashion. These bone units are held in position with absorbable sutures. In this illustration the plates are seen on the outside; we now place these plates on the inside with the exception of the tongue-and-groove fixation on the lateral sides.
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170 Pediatric Neurosurgery extremely important maneuver, for if this muscle is not adequately repositioned, bitemporal dimpling will result postoperatively providing an unacceptable “hourglass” configuration to the face. The skin flap is reapproximated with a subgaleal closure using an absorbable suture such as 3–0 Vicryl. We no longer place any form of subgaleal drain, as doing this has reduced postoperative infection and blood loss. Skin closure is done with a 4–0 Monocyrl suture in a subcuticular fashion. SteriStrips are applied to the skin edges. A snug but nonbinding fluffy dressing is placed over the entire calvaria.
Specialized Instrumentation The use of absorbable miniplates in craniofacial surgery has been quite helpful. These low-profile plates allow instantaneous fixation and stabilization. The use of a high-speed drill system (e.g., Midas Rex) that has small cutting bits, such as the C-1, helps immensely in the bone harvesting and splitting plus decreases the overall operating time. A reciprocating saw and thin-cutting osteotomes are helpful in splitting the calvarial bone.
Postoperative Management Including Possible Complications The child is cared for in the pediatric intensive care unit for a 24 hour postoperative period. Appropriate analgesia is provided to reduce stress for the child. After 24 hours the child is fed by mouth. The child is positioned by the nursing team to lie only on the back so that no undue pressure is applied to the forehead. Occasionally restraints are needed to assist in keeping the child appropriately positioned. On postoperative day 3 to 4 the child not uncommonly develops fever in the 38 to 39°C range. A routine fever workup is done but rarely is a source found, and it is thought these fevers are due to the blood resorption that occurs under the scalp flap. The child is typically discharged on day 4 or 5, assuming he or she is eating and has resumed normal behavior.
astating to the child, as all of the infected bone will need to be removed. Fortunately this complication is very low, <2% in most series. It cannot be emphasized enough the attention that must be paid to sterility, in particular the irrigation done at the end of the case to remove debris and bone dust that can be a source of potential infection. Risk of injury to the neural structures remains very low in all reported craniofacial series. It is the responsibility of the neurosurgical team that no direct injury occurs to the brain while the calvarial remodeling is underway. On our service a member of the neurosurgical team is present throughout the entire surgery and participates in the closure. Significant blood loss, despite careful attention to detail, is always a possibility because of the size of these children. We routinely request from the family donor-directed blood, which is obtained 1 week before surgery. Two units are more than adequate in 95% of cases. The single most common cause of excessive blood loss is a tear in the sagittal sinus. When recognized these tears have to be repaired by the neurosurgical team as quickly as possible. The team must also be prepared for air embolism if a major tear occurs though a clinically significant air embolism is very unusual. Cerebrospinal fluid (CSF) leakage and the potential meningitis can be devastating to the patient. For this reason we are extremely meticulous in the closure, always checking for CSF leaks. It is often helpful to have the anesthesiologist provide a sustained Valsalva maneuver prior to the craniofacial reconstruction to check for dura tears and potential leaks. Acknowledgment This chapter is a revision of the chapter, “Unilateral Coronal Synostosis” by James T. Goodrich, M.D., and Ravelo Argamaso, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 4, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Ravelo Argamaso, M.D., for his help and efforts on the original chapter published in the first edition of this work.
Complications The single most feared complication is infection, particularly infection to the harvested bone. Osteomyelitis is dev-
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26 Moyamoya Syndrome in Children with Pial Synangiosis R. Michael Scott and Edward R. Smith Moyamoya syndrome is a chronic cerebrovascular disorder of unknown etiology characterized by a progressive stenosis of the intracranial internal carotid arteries and their distal branches. There is a compensatory enlargement of the collateral vasculature to the brain, specifically, the small vessels near the carotid apex supplying the cavernous sinus, optic apparatus, etc.; the vessels on the cortical surface and in the leptomeninges; and the branches of the external carotid artery supplying the dura and skull base. The Japanese term moyamoya was coined by Suzuki and Takaku in 1969 and means “something hazy, like a puff of cigarette smoke drifting in the air,” referring to the characteristic angiographic appearance of the abnormally dilated collateral network of vessels that forms at the base of the brain in response to the carotid artery stenosis. This cerebrovascular syndrome is now more widely recognized and easily diagnosed because of the advent of magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), and moyamoya has been reported throughout the Western Hemisphere with increased frequency, usually in association with a wide spectrum of disorders including prior cranial radiation therapy, neurofibromatosis, optic glioma, and genetic disorders such as Down syndrome. The precise etiology of this vasculopathy remains unclear, but it has become apparent that the angiographic phenomenon is associated with a variety of congenital syndromes and diseases that are associated with acute or chronic structural changes or injury to cerebral arterial walls. For this reason, we use the term moyamoya syndrome when referring to the condition; however, about one-half of the patients in the large recently published Children’s Hospital, Boston series have no known cause or association. The incidence of moyamoya syndrome is said to have two age peaks: one in children <10 years of age, and the other in adults 30 to 40 years of age. In adults, the disease usually presents with acute subarachnoid, intraventricular, or intracerebral hemorrhage, although the majority of the adult patients in the senior author’s (RMS) series have ischemic symptoms such as stroke or transient ischemic attack (TIA). Most children present with recurrent TIAs, strokes, seizures, or headaches; ~3% of pediatric patients in The Children’s Hospital series had an intracerebral hemorrhage as their first symptom. The natural history of this disease is unpredictable.
There is no known effective medical therapy that will halt the progression of the arteriopathic process. Antiplatelet agents such as aspirin help prevent the formation of thrombus at areas of vessel narrowing and are an important mainstay of treatment in these patients; our patients remain on aspirin permanently. Calcium channel blockers afford certain patients relief from severe headaches and may reduce TIAs. Several surgical revascularization procedures have been devised to increase blood flow to the chronically ischemic hemispheres, including superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis, encephalomyosynangiosis (the placement of muscle on the exposed cerebral cortex), omental transposition and transplantation, various combinations of these techniques, and the procedure we utilize most frequently in children, pial synangiosis, a modification of Matsushima’s encephaloduroarteriosynangiosis (EDAS) procedure. The advantages of pial synangiosis are several-fold. The operative procedure is relatively short—~3 to 4 hours for one hemisphere, and it avoids the technical challenges of carrying out and maintaining the patency of a very narrowcaliber vessel anastomosis in a child, the diameter of whose superficial temporal artery is frequently <0.5 mm. Donor arteries are almost always available. Both hemispheres can be operated upon under the same anesthesia, avoiding the risks of repeated anesthetic induction in this population. The procedure can revascularize an entire hemisphere, not just a specific arterial territory. The clinical and angiographic follow-up results have been excellent.
Patient Selection Any child with a diagnosis of moyamoya syndrome should be considered for pial synangiosis. The condition is invariably progressive, both clinically and radiographically, and permanent deficits can occur while patients are being observed to verify the syndrome's progressive nature.
Preoperative Preparation The patients require no special preoperative medications, unless dictated otherwise by preexisting conditions such as prior radiation treatment for craniopharyngioma or hypoth-
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10.1055/978-1-60406-039-1c026_f001 Figure 26–1 Patient positioned for bilateral synangiosis, left side first. The head is turned away from the anesthesiologist and secured in a Mayfield head-holder (Schaerer Mayfield, Cincinnati, OH). The course of the parietal branch of the superficial temporal artery has been marked out on the scalp using a Doppler pencil-type probe. A roll has been placed under the left shoulder to avoid compression of the cervical vessels.
the initial side is operated on, surgery on the contralateral hemisphere is postponed. There is no evidence that one anesthetic agent or technique is superior in patients with moyamoya syndrome. Muscular blockade is established by a nondepolarizing muscle relaxant prior to intubation. Any fluid deficits are partially replaced by intravenous crystalloid without glucose (10 mL/kg) over 15 minutes after induction. Anesthesia is maintained with low-dose isoflurane and a balanced nitrous oxide/oxygen mixture with fentanyl. The rationale for the use of these agents is that isoflurane is a cerebral vasodilator and may even provide a protective effect against ischemia. However, any anesthetic technique that will maximize the balance between cerebral blood flow and oxygen consumption is probably reasonable. End-tidal CO2 is maintained between 36 and 42 mm Hg. We avoid the use of hyperventilation or any anesthetic technique that would cause cerebral vasoconstriction because hyperventilation in a child with compromised cerebral circulation could precipitate further ischemic sequelae. Normotension, appropriate for age, is maintained. Diuretics such as mannitol and Lasix (furosemide) are unnecessary and possibly risky in this patient population because of the possibility of dehydration leading to hypotension.
alamic glioma. Standard preoperative tests include routine laboratory tests such as complete blood count and coagulation studies, particularly if the patient has been taking antiplatelet agents preoperatively. Unless contraindicated by study results or other clinical indications, we now continue aspirin right up to the time of surgery in hopes of reducing intraoperative and postoperative thrombus formation in stenotic proximal vessels. All patients undergo selective internal and external carotid angiography prior to surgery. This study assists the surgeon in the identification of vascular anatomy and flow patterns, and demonstrates any preexisting collateral anastomoses from the external circulation that should be preserved during the craniotomy. Single photon emission computed tomography with and without Diamox (acetazolamide) administration have been used in the past on a routine basis to detect any cerebrovascular instability, but it is currently utilized only in unilateral disease or in patients with atypical arteriographic findings—when there is a question as to whether cerebral blood flow in unstable enough to merit surgery. We routinely admit patients the night before surgery for intravenous hydration. If the patient is taking anticonvulsants, the morning dose is administered prior to surgery. Patients receive one dose of prophylactic antibiotics, tailored for the specific hospital environment, 1 hour prior to the skin incision. Steroids, cerebral dehydrating agents such as mannitol, and anticonvulsants are not administered on a routine basis.
Operative Procedure
Anesthesia
Positioning
Premedication adequate to avoid hyperventilation and crying in children is essential, and patients undergo typical craniotomy monitoring, including arterial lines and bladder catheterization. Intraoperative electroencephalography (EEG) monitoring, with a full array of scalp electrodes (except directly at the operative site) is performed on all patients in whom bilateral surgery during the same anesthetic is contemplated. If any significant changes occur on EEG as
The patient is placed in the supine position with a roll under the shoulder opposite the side being operated. Care must be taken to ensure that the cervical vessels are not compressed by extreme head rotation. The head is placed in the lateral position parallel to the floor in skeletal fixation, with a single anterior pin placed in the high midline forehead to allow rotation of the head without new pin placement if the opposite side is to be operated on under the
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same anesthesia (Fig. 26–1). In a child under the age of 1 year, the head is positioned on a “doughnut” or cerebellar headrest if the skull does not appear sturdy enough for pin fixation. After completion of the first procedure, the head is turned (maintaining skeletal fixation) and the shoulder roll is placed under the opposite shoulder. If a circular or horseshoe headrest is used in the very young child, care should be taken to ensure that the new craniotomy site is not compressed by the device.
ous tissue is made directly over the vessel at its most distal marked point with a no. 15 scalpel. The artery is identified by scalp retraction with toothed forceps and dissected using a delicate curved pediatric hemostat. A linear incision following the course of the artery is then performed, using the hemostat to dissect and then protect the STA as the assistant incises the skin overlying it. The skin edges rarely require coagulation, and most scalp-edge bleeding will stop spontaneously.
Skin Incision
Synangiosis Procedure
The posterior (parietal) branch of the superficial temporal artery (STA) is identified by a pencil Doppler probe, and the artery is traced from its base above the zygomatic arch to the parietal convexity. Its course is accurately marked on the skin with an 18 or a 21 gauge needle. We attempt to mark out at least 10 cm of vessel in most patients, but in small children, often only 6 to 7 cm can be identified. Although the posterior branch of the STA is most frequently utilized because the skin incision can be kept behind the hairline and the majority of the MCA circulation lies beneath that branch of the artery, the frontal branch can be used if absolutely necessary. Standard skin prep and draping can then be performed. We utilize the microscope right from the beginning of the artery dissection, finding it particularly helpful in very small children because of the fragility and small size of STA, and in young adults because of the frequent tortuosity of the vessel and its branches. A small skin incision down to subcutane-
After the artery is exposed, we use a needle tip cautery (“Colorado needle”) at a low setting to separate the artery with its subjacent galea strip from the galea on either side. The artery pedicle is then encircled with a vessel loop distally and elevated and separated from the underlying periosteum and temporalis fascia using standard monopolar cautery, attempting to preserve as much adventitia and loose areolar tissue beneath the vessel as possible (Fig. 26–2). Anterior and posterior scalp flaps are then developed with electrocautery dissection to minimize bleeding, and disposable fishhook-type retractors are used to maintain scalp retraction. The artery pedicle is retracted out of the field as needed using the vessel loop, and the temporalis muscle is incised with the electrocautery into four equal quadrants, which are retracted widely using the previously placed skin hooks. Generous bur holes are drilled inferiorly and superiorly in the exposure, and as large a craniotomy as possible is performed using power equipment. The dura
10.1055/978-1-60406-039-1c026_f002 Figure 26–2 The superficial temporal artery dissection has been completed under the microscope with the aid of a needle electrocautery, and the vessel has been encircled with a vessel loop to aid in its displacement during the remainder of the procedure.
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10.1055/978-1-60406-039-1c026_f003 Figure 26–3 The craniotomy has been performed, and the scalp edges and temporalis muscle retracted with fishhook retractors (Lone Star retractor system; Lone Star Medical Products Inc., Stafford, TX). The dura is opened in multiple flaps secured with sutures.
is then opened vertically along the exposure and cut into six separate flaps that are retracted on sutures (Fig. 26–3); care is taken to preserve any significant middle meningeal collateral observed on the preoperative arteriogram and the dural opened around or between such vessels. Under high power of the microscope, the arachnoid is incised linearly over the exposed cortex using a disposable arachnoid knife and jeweler’s forceps, beginning inferiorly (temporally) in a sulcus and then opening the arachnoid linearly along the sulcus and when possible laterally toward the crown of adjacent gyri (Fig. 26–4). Vannas ophthalmic scissors are helpful in making long continuous arachnoid openings over MCA
branches in certain patients. The pial vasculature is profuse and tortuous in patients with advanced disease, and these areas of the pia should be avoided when the arachnoid is opened. Bleeding that occurs from the pial surface or from small vessels within the sulci usually stops after a few moments of irrigation with a microirrigator or the application of a minuscule pledget of Gelfoam soaked in thrombin solution. After completion of the arachnoid opening through as much of the length of the exposure as possible, the STA with its galea investiture is brought down onto the surface of the brain, placing the vessel over areas of opened arachnoid. Using jeweler’s forceps and a Castroviejo needle-
10.1055/978-1-60406-039-1c026_f004 Figure 26–4 The arachnoid is being opened over a sulcus adjacent to a cortical vein using jeweler’s forceps and a disposable
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Moyamoya Syndrome in Children with Pial Synangiosis 175 (Rapide) to approximate the skin edges. A sterile Telfaover-Xeroform gauze dressing is applied, but the head is not wrapped tightly to avoid compressing the scalp arteries. Patients are extubated and sent to the intensive care unit following the procedure.
Postoperative Management Including Possible Complications
Figure 26–5 The arachnoid has been opened in a roughly linear trajectory from temporal to frontal across the sylvian fissure using a disposable arachnoid knife, jeweler’s forceps, and ophthalmic (Vannas) scissors. The synangiosis has been accomplished with four interrupted sutures of 10-0 nylon passed through pia and superficial temporal artery adventitia, with the donor vessel kept in apposition to areas of opened arachnoid. The arrows point to parallel arachnoid openings made over middle cerebral artery branches anterior to the major arachnoid opening. A small focus of subpial hemorrhage can be seen to the left of the donor vessel, an unavoidable complication in many moyamoya patients with hypervascular cortical surfaces. 10.1055/978-1-60406-039-1c026_f005
holder, the vessel is fixed to the cortical surface by placing approximately four interrupted 10–0 nylon sutures through the vessel pedicle soft tissue and the outermost layer of the pial-cortical surface. This tight pial approximation leads to a more satisfactory postoperative result then simply placing the vessel on the brain or suturing the vessel into the dura (Fig. 26–5). The dura is then loosely laid on the brain surface and not sutured becasue collateralization of the underlying brain will also occur from the cut edges of the dura. A large piece of Gelfoam soaked in saline, or DuraGen (Integra LifeSciences, Plainsboro, NJ, trimmed to the size of the bony opening, is placed over the entire exposure, and the bone flap is repositioned using three to four miniplates. The bur hole openings at either end of the flap should be enlarged if necessary prior to its repositioning to ensure that the artery is not compressed when the flap is replaced. The temporalis muscle is approximated only from inferior to superior so that the superficial temporal artery is not compressed. The scalp is closed in two layers, using 3–0 or 4–0 Vicryl suture on the galea followed by 4–0 or 5–0 monofilament Vicryl
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There are very few special postoperative orders. The patient's head is slightly elevated to assist in venous return and avoid cerebrospinal fluid accumulations under the skin flaps. The patient is given sufficient pain medication so that there is a minimum of crying and hyperventilation. Antibiotics are given postoperatively for 24 hours. Patients are mobilized as tolerated and kept well hydrated. Blood loss with the procedure should be less than 100 cc, and transfusions should be avoided if at all possible because of the rheologic problems that can be created by a high hematocrit. Postoperative seizure medication is continued on an individualized basis, and aspirin is begun 24 hours after surgery. Postoperative hypertension is rarely treated unless significant elevations occur, and care must be taken if treatment is required to avoid rebound hypotension. The most significant postoperative complication in our series has been stroke, which in a consecutive series of 143 patients occurred at ~4% per operated hemisphere. Patients at greatest risk appear to be those with neurological instability around the time of surgery or those who have suffered a stroke within 2 months of the operation—although angiographic risk factors, such as involvement of the posterior circulation, must also play a role. There have been two perioperative deaths related to ischemic stroke: one in a 5-year-old child operated on in the midst of a flurry of strokes who developed additional strokes in the immediate postoperative period and died of brain edema and herniation, and one in a 15-year-old boy with progressing disease and a preoperative dominant hemisphere stroke and basilar artery disease whose internal carotid artery—the sole supply of his posterior circulation—thrombosed several hours following a unilateral operation. There have been several late subdural hematomas in this surgical series that have required evacuation, a complication probably related to preexisting brain atrophy and chronic antiplatelet therapy. A death 6 years following surgery occurred from the rupture of an aneurysm on a deep moyamoya collateral vessel.
Follow-up All patients in this series in the past had undergone arteriography 1 year following the procedure to document the efficacy of the procedure and to provide a new baseline, along with MRI and MRA studies, for future evaluation (Fig. 26–6). Because of the rapid improvements that are being made in MRA imaging, we have begun following patients with MRI studies alone because the formal arteriograms have confirmed the surgery’s effectiveness. Late angiographic studies have confirmed the durability of the collateral induced by
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176 Pediatric Neurosurgery pial synangiosis, with one patient’s arteriogram repeated out 9 years after synangiosis because of the development of a brain tumor demonstrating even more luxuriant collateral than the initial 1-year follow-up study. Acknowledgment This chapter is a revision of the chapter, “Treatment of Moyamoya Syndrome in Children with Pial Synangiosis” by R. Michael Scott, M.D., and Richard G. Ellenbogen, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 4, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Richard G. Ellenbogen, M.D., for his help and efforts on the original chapter published in the first edition of this work.
Figure 26–6 One-year postoperative magnetic resonance angiogram in a patient who has undergone bilateral pial synangioses. The arrowheads denote new collateral to the hemispheres via the superficial temporal and middle meningeal arteries. The intracranial internal carotid arteries are now totally occluded. 10.1055/978-1-60406-039-1c026_f006
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27 Selective Dorsal Rhizotomy for Spastic Cerebral Palsy Tae Sung Park and James M. Johnston Cerebral palsy (CP) is a major neurological problem in children; it occurs in 1 of 500 live births and inflicts lifelong disabilities on those with the disorder. Among several factors contributing to the disabilities of patients with CP is spasticity. Spasticity affects nearly 80% of patients with CP, and once fully developed, it never resolves spontaneously. It hinders motor activities in daily living and also causes muscle contractures and orthopaedic deformities in growing children. Selective dorsal rhizotomy (SDR) reduces spasticity in CP; this reduction facilitates patients’ motor performance and alleviates orthopaedic deformities. Several surgical techniques for SDR are currently used. The standard technique requires an L1-S1 laminectomy or laminoplasty for visualization of all dorsal nerve roots exiting at their respective foramina. The following is a description of an operation that includes an L-1 laminectomy, ultrasonographic localization of the conus medullaris, and partial deafferentation of L1S2 roots with electromyographic (EMG) testing under an operating microscope. Advantages of this technique include decreased operative time, reduced postoperative pain, as well as minimal risk of progressive lumbar instability. This procedure is both effective and well tolerated in appropriately selected children and adults. We have performed this SDR in more than 1500 children and young adults since 1991.
Patient Selection The primary beneficiaries of SDR are children with spastic diplegia, the most prevalent subtype of CP in which the lower extremities are affected with minimal or no involvement of the upper extremities (Table 27–1). Children with spastic quadriplegic CP, in whom all extremities and the trunk are involved, also benefit from SDR. In spastic hemiplegic CP, spasticity is not a predominant cause of motor impairments, and reduction of spasticity does not greatly improve motor functions. Some adults younger than 40 years of age who have relatively mild spastic diplegia and can walk independently are also able to benefit from SDR. When evaluating a patient, one should first be certain that a patient’s motor impairment dates back to infancy and has taken a course of steady improvement rather than progressive deterioration during the preschool years. A careful review of the patient’s perinatal history and medical his-
10.1055/978-1-60406-039-1c027_t001 Table 27–1 Indications for Selective Dorsal Rhizotomy for Spastic Cerebral Palsy Children Younger than 18 Years At least 2 years of age Diagnosis of spastic diplegia or spastic quadriplegia Some form of independent mobility (e.g., crawling or walking) with or without an assistive device History of premature birth; if born at term, child must have typical signs of spastic diplegia Patients exhibit potential for improvement in functional skills after dorsal rhizotomy Adults between Ages 19 and 40 Years Diagnosis of spastic diplegia History of premature birth Currently ambulates independently without assistive device Relatively mild fixed orthopaedic deformities Patients exhibit potential for functional gains after dorsal rhizotomy Patients exhibit motivation to perform home exercise program
tory provided by physicians and therapists is invaluable. A history of premature birth is considered a positive factor in the selection of candidates for SDR. Findings from a neurological examination determine whether spasticity is a major cause or the only cause of muscle hypertonia and significantly hinders motor activities (e.g., sitting, crawling, standing, and walking). In addition, the severity of orthopaedic deformities and their effects on a patient’s motor performance should be assessed in detail. A thorough understanding of orthopaedic problems by the neurosurgeons performing SDR is desirable, although orthopaedists and therapists can assist in evaluation. Radiological evaluation includes lumbosacral spine and hip radiographs. The spine radiographs may show the presence of lumbar hyperlordosis, scoliosis, spondylolisthesis, and congenital anomalies. Hip radiographs may reveal hip subluxation and dislocation, deformities that influence the timing of surgical interventions. In children who were delivered at term, head magnetic resonance imaging (MRI) is obtained because diverse abnormalities underlie the diagnosis of spastic diplegia or quadriplegia. In adults with back pain, spine MRI is obtained to rule out herniated disk and other intraspinal disorders. A gait analysis is not routinely obtained, but it helps to con-
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178 Pediatric Neurosurgery firm the presence of spasticity before SDR and also to assess changes in motor performance after SDR. SDR is not considered for children younger than 2 years because CP cannot be diagnosed with certainty in young children. Dystonia that is concomitant with spasticity is not a contraindication for rhizotomy. Dystonia is exceedingly rare in spastic diplegia but is common in nonambulatory children with whole body involvement. Dystonia becomes clinically evident by age 5 years. SDR in patients with dystonia can improve motor function, and this improvement does not worsen the dystonia. Rigidity is also rare in spastic diplegia, but rigidity cannot be ascertained in the presence of concomitant spasticity. Severe damage to the basal ganglia, as revealed with MRI, is considered a contraindication because of the possibility of concomitant rigidity. A history of multiple orthopaedic operations is generally a contraindication for rhizotomy, mainly because of severe muscle weakness and fixed deformities. Patients with severe fixed joint deformities are excluded from SDR because the deformities limit gains in motor function after rhizotomy. The best example is severe crouch knees due to overstretched or lengthened heel cords after heel cord release procedures. Severe scoliosis is only a relative contraindication for SDR through a single-level laminectomy. Children with increased muscle tone due to severe hydrocephalus, intrauterine and neonatal infections, and head trauma are not candidates for SDR. In general, neuronal migration disorders are contraindications for rhizotomy, but children with typical clinical features of spastic diplegia due to schizencephaly can benefit from rhizotomy.
Preoperative Preparation Oral midazolam is administered, if deemed necessary. Intubation is performed while the patient is under deep seroflurane anesthesia; sometimes intubation is facilitated by short-lasting muscle relaxants (e.g., atracurium or vecuronium). Anesthesia is induced with seroflurane, and nitrous oxide and is maintained with fentanyl (10 μg/kg), 2% seroflurane, and 70% nitrous oxide. Propofol is avoided because it alters EMG activities. The patient receives a dose of antibiotic before a skin incision. A bladder catheter is inserted.
Operative Procedure The patient is placed in a prone position on the operating table so that cerebrospinal fluid (CSF) is pooled rostrally and CSF loss from the intracranial compartment is minimized (Fig. 27–1). Needle electrodes are placed bilaterally in the adductor longus, vastus lateralis, anterior tibialis, medial hamstring, and medial gastrocnemius muscles in preparation for intraoperative EMG examinations.
Localization of the Conus Medullaris and a SingleLevel Laminectomy Normally, the conus medullaris terminates between the T-12 and L-3 spinal levels. For a laminectomy to be limited to a single level, the conus medullaris must be localized
10.1055/978-1-60406-039-1c027_f001 Figure 27–1 After electromyographic electrodes are inserted, the patient is placed prone in the Trendelenburg’s position to minimize cerebrospinal fluid loss during the operation.
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27 Selective Dorsal Rhizotomy for Spastic Cerebral Palsy 179 in several steps with ultrasound before a laminectomy is completed. In children younger than 10 years, the conus medullaris and cauda equina are localized with axial views of the spinal cord ultrasound through the skin and paraspinal muscles. An ultrasound probe is placed lateral to the spinous process to get axial views of intradural structures at a few levels (Fig. 27–2A). On axial views, the conus appears hypoechogenic and circular. The ventral and dorsal roots are attached to the lateral aspects of the conus. Pulsatile movements of the conus are always present. The cauda equina appears as a hyperechogenic mass. It also has pulsatile movements (Fig. 27–2B). In children younger than 10 years, the skin incision is made over the interlaminar space where the conus has been localized with ultrasound. The paraspinal muscles are injected bilaterally with saline solution that contains epinephrine in a concentration of 1:400,000. The interlaminar space is exposed, and the interspinous ligament and ligamentum flavum are removed. The conus is localized with axial and sagittal views of ultrasound. If, with ultrasound, the spinal cord is rostral to the conus or the cauda equina is caudal to the conus, then the skin incision is extended rostrally or caudally. The next interlaminar space is exposed. If the conus is clearly localized with axial and sagittal views of ultrasound, the next caudal interlaminar space is exposed. The cauda equina is localized with ultrasound (Fig. 27–2B). In older children (older than 10 years) and adults, ultrasound localization of the conus is impossible. Thus the spinous process of the L-1 vertebra is localized with a lateral radiograph of the lumbosacral spine and marked by ~0.2 ml of indigo carmine. First, the T12-L1 interlaminar space is exposed. The ligamentum flavum is removed to expose
the extradural fat tissue. Ultrasound examination of intradural structure is done through the interlaminar space (Fig. 27–2A). If the interlaminar space is tight for the ultrasound examination, it is enlarged with a Kerrison punch. Two levels of interlaminar space are examined to localize the conus and cauda equina. If the conus and cauda equina are localized, a single-level laminectomy is performed with a Midas Rex craniotome with a B5 attachment (Medtronic Powered Surgical Solutions, Fort Worth, Texas) (Fig. 27–3A). After the lamina is removed, ultrasound examination of the laminectomy site is obtained again to confirm that the conus and cauda equina are at the laminectomy site. On the ultrasound examination, the conus is distinguished from the cauda equina as follows (Fig. 27–2B): a sagittal examination reveals the conus as a hypodense triangle tapering caudally. The ventral and dorsal spinal roots appear hyperdense. When only a caudal end of the conus is in the laminectomy area, sagittal examination does not clearly delineate the conus, and an axial examination is required. A hypoechogenic circular structure on axial view is sought at the center of the dural tube; it is most reliable in localizing the conus. Also, on axial view, one can notice a small cleft between the dorsal and ventral spinal roots on the lateral aspect of the conus. This cleft is an important anatomical landmark because it guides the surgeon in separating the dorsal roots from the ventral roots. Sometimes the patent central canal appears hyperechogenic within the conus. Even in 2-year-old children, only a single-level laminectomy is needed for SDR. The laminectomy should cover at least 5 mm of the conus so that the dorsal roots are safely separated from the ventral roots at a later stage of operation. If it is needed for the adequate exposure of the conus,
A
B Figure 27–2 (A) Through an L1-2 interlaminar space or a keyhole laminotomy, the conus medullaris is identified with ultrasound. (B) The conus appears hypoechogenic (arrowhead) in contrast to the hyperecho-
genic cauda equina. If the conus is not identifiable through the interlaminar space, then an ultrasound examination is repeated through the L1-2 interlaminar space.
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A
B
C Figure 27–3 (A) After the conus is clearly identified, a single laminectomy is done entirely with a Midas Rex craniotome. At least 5 mm of the caudal conus should be exposed. The laminectomy extends laterally close to the facet joint. (B) After the dural incision, an operating microscope is brought into the field. The L-1 and L-2 spinal roots are identified at the corresponding intervertebral foramina, and the filum terminale in the midline is found. (C) The L-2 dorsal root and the dorsal roots medial to the L-2 root are retracted medially to separate the L2-S2 dorsal roots
D from the ventral roots. The thin S3-5 spinal roots exiting from the conus are identified. A cotton patty is placed over the ventral roots and lower sacral roots. (D) A 5 mm Silastic sheet is placed under the L2-S2 dorsal roots, after which the surgeon again inspects the L-2 dorsal root at the foraminal exit, the lateral surface of the conus between the dorsal and ventral roots, and the lower sacral roots near the filum terminale. The inspection ensures placement of only the L2-S2 dorsal roots on top of the Silastic sheet.
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one-third of the lamina that is immediately rostral to the laminectomy is removed. A wide laminectomy is necessary to expose the spinal nerve roots for EMG testing. Other neurosurgeons perform SDR through L2-S1 or L1-S1 laminectomy or laminoplasty. The multilevel laminectomy makes SDR easy. Nevertheless, the multilevel laminectomy
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or laminoplasty, when performed in children with spastic diplegia or quadriplegia, can lead to late spine deformities, including spondylolisthesis and increased lumbar lordosis or scoliosis. The multilevel laminectomy may carry a higher risk of spine deformities after SDR in older children and adults than in young children.
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27 Selective Dorsal Rhizotomy for Spastic Cerebral Palsy 181 Separation of Dorsal Roots from Ventral Roots After bleeding from the epidural veins and bone is controlled, a dural incision is made. Saline irrigation is not used after the dura is opened because it alters EMG responses. An operating microscope is then brought into the field and used during EMG testing and sectioning of dorsal root fascicles. The operating table may be slightly rotated away from the surgeon as the contralateral spinal roots are dissected. The arachnoid is removed, and the conus and filum terminale are identified. At this point, EMG activities are continuously monitored to determine if any movement of the nerve roots evokes EMG activities. Stretching and pressure on the ventral roots but not on the dorsal roots evoke EMG activities and often movement of the patient’s lower extremity. Next, the L-2 spinal roots are identified at the neural foramen, and the L-2 dorsal root is separated from the ventral root (Fig. 27–3B). The L-2 ventral and dorsal roots are traced back to the conus until the cleft between the ventral and dorsal roots is identified. Then the L-2 and adjacent dorsal roots are gently retracted medially, and a cotton patty is placed over the ventral roots (Fig. 27–3C). The L-1 root is left untouched at this point. Next, the conus and the filum terminale are examined, and the S2-5 sacral roots that exit the conus are identified. The S-2 dorsal root can be bulky, especially in patients with the postfixed lumbosacral plexus, but there is always an abrupt and marked decrease in size of the S-2 root. The individual S3-5 spinal roots appear as thin threads. The dorsal and ventral roots at this level are close together without intervening space between them, so all of the S3-5 spinal roots are left intact. The lower sacral roots can best be identified with a gentle lift at the dorsal roots from the entry zone on the dorsal aspect of the conus. Whenever the surgeon is unsure of the exact identification of the S3-5 spinal roots, then sparing the S-2 dorsal root would be prudent. Once the L2-S2 dorsal roots are identified, a 5 mm wide blue Silastic sheet (Dow Corning, Midland, Michigan) is placed around all of the dorsal roots and distant from the conus (Fig. 27–3D); the Silastic sheet keeps the L2-S2 dorsal roots safely separate from the ventral and lower sacral roots during the rest of operation. Before starting EMG testing, the surgeon reexamines three structures to ensure that no ventral root or lower sacral root is over the Silastic material: the L-2 foraminal exit, the cleft lateral to the conus between the ventral and dorsal roots, and the S3-5 roots.
Identification of Individual Dorsal Roots A shortcoming of this technique, as compared with alternative techniques, is difficulty in the identification of individual dorsal roots with certainty. Precise identification of the roots, however, is not critical for SDR because all major lower extremity muscles of children with spastic CP receive motor innervation from several segments. As is shown in animal experimental studies, significant somatotopic organization and sprouting may occur in the spinal cord and brain after deafferentation. The L-2 dorsal root is readily identified at the neural foramen. The L3-S2 dorsal roots below the conus are close
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together without a natural separation, so unequivocal identification of the individual dorsal root is difficult. Nevertheless, dorsal root fibers of individual segments are roughly identified as follows. First, the dorsal roots are spread on top of the Silastic sheet. The L-3 and L-4 dorsal roots, which are located medial to the L-2 root, are identified; each of the roots consists of two and three naturally separated rootlets. The L-5 and S-1 roots are medial to the L-4 root and largest of all the lumbosacral roots. The L-5 and S-1 dorsal roots consist of three or four rootlets with natural separation. The S-2 root has a single fascicle. Second, an innervation pattern of each root is examined with EMG testing. An individual dorsal root is placed over two hooks of the Peacock rhizotomy probes (Aesculap Instrument Co., Burlingame, California) (Fig. 27–4A), and responses to electrical stimulation with a threshold voltage are recorded from the lower extremity muscles. The entire dorsal root is tested at each level immediately before subdividing the dorsal root into rootlets.
EMG Examination and Sectioning of Dorsal Roots After the innervation of a dorsal root is determined, the root is sharply subdivided into three to five smaller rootlet fascicles of equal size with a Scheer needle (Storz Instruments, St. Louis, MO) (Fig. 27–4B). The rootlet fascicles are suspended over two hooks of the rhizotomy probes (Fig. 27–4C). Single constant square wave pulses of 0.1 milliseconds duration are applied to the rootlet at a rate of 0.5 Hz. The stimulus intensity is increased stepwise until a reflex response appears from the ipsilateral muscles. After the reflex threshold is determined, a 50 Hz train of tetanic stimulation is applied to the rootlet for 1 second. The reflex response is then graded according to the criteria detailed in Table 27–2. Our experience has been that most rootlets produce 1+ to 4+ responses. Thus we base our decision to section a given rootlet on the number of rootlets producing sustained responses at that level and the intensity of the responses. The rootlets that produce a response of 0 are left intact. The rootlets producing 3+ and 4+ responses are cut, and those producing 1+ and 2+ responses are sometimes spared. The dorsal rootlets spared from sectioning are placed behind the Silastic sheet and kept separated from rootlets yet to be tested (Fig. 27–4D). If only 1+ and 2+ responses are detected, then rootlets with the most active responses are cut (Fig. 27–4E). At least one rootlet is left irrespective of EMG responses to avoid postoperative sensory loss. The procedure is performed in sequence on the remaining L3-S2 dorsal roots (Fig. 27–4F). Using the criteria given in Table 27–2, we section 60 to 65% of the rootlets examined. Finally, the L-1 dorsal root is identified at the neural foramen, and half of the dorsal root is cut without EMG testing. In our experience EMG testing of the L-1 root is unreliable. The sectioning of the L-1 dorsal root is necessary to further reduce spasticity in hip flexors, especially in patients with a large L-1 root associated with prefixed lumbosacral plexus. The rhizotomy is repeated on the contralateral side. The intradural space is irrigated with saline solution. Bipolar cautery is seldom required for control of bleeding from the cut ends of fascicles. The dura is closed in a running fashion with 4–0 monofilament nylon. Clonidine (2 μg/kg up to 7 years of age and 1 μg/kg over 8 years of age) mixed with morphine at 15 μg/kg of body weight is injected intra-
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182 Pediatric Neurosurgery A
B
C
D
E
Figure 27–4 (A) The L-2 dorsal root is easily identified. In an attempt to identify the L3-S2 dorsal roots, all the dorsal roots are spread over the Silastic sheet and grouped into presumed individual dorsal roots. Then the innervation pattern of each dorsal root is examined with electromyographic (EMG) responses to electrical stimulation with a threshold voltage. (B) With a Scheer needle, each dorsal root is subdivided into three to five rootlet fascicles, which are subjected to EMG testing. (C) Stimula-
F
tion of an L-2 rootlet fascicle elicits an unsustained discharge to a train of tetanic stimuli. (D) The rootlet is thus spared from sectioning and placed behind the Silastic sheet. (E) Stimulation of a rootlet fascicle elicits sustained discharges from multiple muscles. The rootlet is thus sectioned. (F) The rootlets spared from sectioning are under the Silastic sheet, and the roots to be tested are on top of the Silastic sheet. Note that EMG testing and sectioning of the dorsal roots are performed caudal to the conus.
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27 Selective Dorsal Rhizotomy for Spastic Cerebral Palsy 183 Table 27–2 Criteria for Grading Electromyographic Responses in Selective Dorsal Rhizotomy for Spastic Cerebral Palsy Grade
Electromyographic Response
0 1+
Unsustained or single discharge to a train of stimuli Sustained discharges from muscles innervated through the segment stimulated in the ipsilateral lower extremity Sustained discharges from muscles innervated through the segment stimulated and immediately adjacent segments Sustained discharges from segmentally innervated muscles and muscles innervated through segments distant to the segment stimulated Sustained discharges from contralateral muscles with or without sustained discharges from the ipsilateral muscles
2+
3+
4+
10.1055/978-1-60406-039-1c027_t002 durally. The Trendelenburg’s position is reversed. A strip of Gelfoam is left over the laminectomy defect, and the wound is closed in layers.
Postoperative Management Including Possible Complications
Patients are transferred to the ward the next day, and the fentanyl drip is continued for another 24 to 48 hours. On the third postoperative day, patients are allowed to sit, and physical therapy is started. The patients are discharged to home on the fifth postoperative day and receive outpatient physical therapy from local therapists.
Postoperative Course and Complications With spastic diplegia the operation invariably reduces spasticity, whereas with spastic quadriplegia there is a small chance of recurrent spasticity. Most patients who were independent walkers preoperatively resume independent walking within 2 weeks after undergoing the SDR technique previously described. Patients who walked with assistance preoperatively take a slower postoperative course. Within 2 months, however, all patients show motor performance exceeding preoperative levels. The major complications of SDR include paraplegia, sensory loss, bladder and bowel incontinence, CSF leak, and infection. There has been one case of CSF leak requiring operative repair in more than 1500 children and adults who have undergone single-laminectomy SDR at our institution, clear evidence of the safety of the procedures. Also, no patients had late spine deformities that required medical or surgical intervention. Many patients, however, did experience hyperesthesia in the legs for several months.
Postoperative Care Patients stay overnight in the intensive care unit where they receive an intravenous infusion of fentanyl, at a dose of 1 to 3 μg/hour per kg of body weight, and diazepam, as needed.
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28 Treatment of Lambdoidal Synostosis with Calvarial Reconstructive Techniques David F. Jimenez, Constance M. Barone, and James Tait Goodrich Although premature closure of the lambdoid suture is the least common of all craniosynostosis, it produces a marked posterior deformity characterized by ipsilateral flattening of the occiput, skull base changes leading to cranial scoliosis, and inferior displacement of the temporal-mastoid region (Fig. 28–1, Fig. 28–2, and Fig. 28–3). These changes may be mild or severe depending on the time of onset of the synostosis, (in utero vs. early or late infancy) and extent of suture closure. Care must be taken not to confuse true lambdoidal craniosynostosis with deformational plagiocephaly, which may be due to torticollis and/or positional sleeping patterns. True lambdoidal synostosis will
give the cranium a trapezoidal appearance, when viewed from above, versus a parallelogram shape in the case of deformational plagiocephaly.
Figure 28–1 Three-month-old male with left lambdoidal synostosis. Prominent findings include ridging of the affected suture, inferolateral displacement of the ipsilateral posterior fossa, asymmetric skull base, and inferior displacement of temporomandibular complex.
Figure 28–2 Minimal asymmetry of the forehead is seen in lambdoid craniosynostosis when compared with deformational plagiocephaly. Sagittal calvarial scoliosis is evident with deviation of the parietal area toward the involved suture can be seen with stenoidal involvement.
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Patient Selection Patients presenting with severe deformation of the occiput, skull base, and calvaria who are older than 9 months of age are ideal candidates for extensive calvarial reconstructive techniques. Although every attempt should be made to diagnose and treat these infants at an earlier time, often referring pediatricians and primary care providers will watch and follow these patients expectantly hoping for selfcorrection. Parents should be advised that these are risky
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28 Treatment of Lambdoidal Synostosis with Calvarial Reconstructive Techniques 185
Preoperative Preparation
Figure 28–3 Patient with left lambdoid synostosis shows no evidence of vertical dystopia (vs. contralateral coronal synostosis); inferior displacement of ipsilateral mastoid complex and contralateral parietal bossing. 10.1055/978-1-60406-039c028_f003
procedures, and the surgical and anesthesia teams must be ready to deal with unexpected complications such as injury to the confluence of sinuses, or transverse or sigmoid sinus tears. Whenever possible, family should be encouraged to have donor-directed blood available for possible intra- and postoperative transfusions.
As these children are generally healthy, no specific preoperative preparations are needed besides baseline hematological studies. Generally, the anesthesia team requires only normal electrolytes and hematocrit levels. The patient should be given a single dose of anti-staphylococcal antibiotic (oxacillin 50 mg/kg intravenously) 1 hour prior to surgical incision. A Foley catheter is inserted to follow the intravascular volume status during the operative procedure. Many anesthesia teams prefer to place intra-arterial and central venous lines to closely monitor the patients during the surgery. To allow access for both plastic surgery and neurosurgical teams, the patient is placed prone, in the center of the room on an adequately padded horseshoe headholder. The patient’s head is placed at 180 degrees from the anesthesia team, and the scrub nursing team can be located to the patient’s left. A Mayo stand is placed over the patient’s back and holds the active surgical instruments. A second larger table is kept behind the main tray set-up of both surgical teams. A third sterile table, equipped with a complete drill and cranial fixation systems, is provided for the plastic surgery team. All cautery cords, suction tubes, and other lines are placed toward the feet of the patient so that there is no clutter on the floor within the operating circle. The patient is placed in the prone position with the forehead and face resting on the horseshoe-shaped headrest covered with a viscoelastic polymer pad. The eyes must be checked to ensure that no pressure is being applied by the headrest. The head is placed in a position level to the heart to reduce the risk of air embolism. Shaving is performed only in an area around the proposed incision line for a width of 2 cm (Fig. 28–4). In children with thin hair, no shaving is required. The entire occipitoparietal area, including the ears, is scrubbed with Betadine (providone-iodine) soap followed by Betadine solution and paint.
10.1055/978-1-60406-039c028_f004 Figure 28–4 Three-month-old female placed prone in padded horseshoe. A small area is shaved extending biparietally. The scalp flap is retracted posteriorly to expose the occiput for bilateral reconstruction.
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186 Pediatric Neurosurgery
Operative Procedure Skin Incision If desired, scalp hemostasis is enhanced prior to skin incision by infiltrating the dermis with 0.25% lidocaine and epinephrine (1:400,000). If not, a relatively bloodless scalp opening can be made using the monopolar electrocautery unit with a fine needle tip set at 15 W with a blend of 80% cut and 20% coagulation. The incision is made to extend from ear to ear and is carried just behind the ear helix. The scalp flap is elevated in the subgaleal plane and carried posteriorly to allow full exposure of the occiput. The pericranium is elevated as a separate layer and taken down to the nuchal musculature, which is elevated with the pericranium using the monopolar needle tip electrocautery. Once elevated, the pericranium and muscles are covered with a moist sponge to keep them from dehydrating and shrinking.
Craniotomy Correction of a severe lambdoidal malformation requires complete disassembly of the parieto-occipital region. Our plastic surgery team marks out the occipital site with methylene blue. First, a new bandeau is marked out (Fig. 28–5) that will provide an anchoring unit upon which reconstruction is based. A new “backhead” has to be identified, for
which we use a Marchac template to find an area of calvaria that is symmetrically close to normal. Depending on how far forward the symmetric reconstruction is carried, we mark out an osteotomy that is taken from each asterion up to just behind the anterior fontanelle. A “step-off” is marked out at the asterion; this will provide an anchoring point to which the new bandeau is placed in a tongue-and-groove fashion (Fig. 28–6). Another osteotomy is then carried around as long as possible under the inion pointing to the base of the skull. These osteotomies result in three units of harvested bone: (1) the new bandeau; (2) the new backhead; and (3) the remaining occipital unit. This third piece is then cut up into units of bone to be replaced in a mosaic fashion. Another technique is to cut the occipital bone into strips, which then can be radially placed to give a “sunrise” appearance to the new occipital complex (Figs. 28–7 and 28–8). The bur holes are made with a round drill bit (Medtronic–Midas Rex M33; Medtronic Inc., Ft. Worth, Texas) and a 0.5 cm bur hole is placed on either side just behind the asterion. Once the dura is cleared, a footplate attachment (Midas Rex B5) is used and a bone flap elevated. Elevation of the bone flap may be accomplished in several ways. The footplate attachment is used to create an osteotomy from the asterion to midline. If difficulties are encountered near the sagittal suture, then a second osteotomy is begun at the contralateral bur hole and united with the previous osteotomy. This can be done in sequential fashion until three to five
10.1055/978-1-60406-039c028_f005 Figure 28–5 Artistic reconstruction of the bandeau and “backhead” and sites from which these are harvested.
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28 Treatment of Lambdoidal Synostosis with Calvarial Reconstructive Techniques 187
Figure 28–6 Artist’s rendition of removal of posterior occipital bone plate. The reconstructed “tiara,” fixed with miniplates, is seen in the lower insert. 10.1055/978-1-60406-039c028_f006
segments are cut. The area where the backhead was elevated is used as an anatomical opening to dissect various sutures, whereas typically the dura is very adherent. If the dura is extremely adherent or the team feels the sinus may be injured, an additional osteotomy is made just lateral to the sagittal suture and carried parallel to and down over the occipital bone to the lower osteotomy. This cut allows easy exposure of the sagittal sinus along its length. Extra care must be taken with all of the major dural sinuses and their points of confluency. This is especially the case at the asterion. If the sinuses are interrupted here, the bleeding can be profuse and life-threatening. The asterion suture is often involved in lambdoidal synostosis and must be released, which can be done easily with careful dissection using a no. 1 Penfield dissector. This osseous area also has to be released, as a tongue-and-groove bandeau will be anchored here. The bone flap is now handed off to the plastic surgery team to complete the reconstruction at a separate table.
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The “tiara” (backhead and bandeau unit) is made using the three anchor miniplates, and this is the foundation on which the reconstruction will be based. The tiara unit is placed tongue-and-groove into the asterion region. A critical unit is the strut piece that is placed from the region of the anterior fontanelle to the most superior point of the tiara (Fig. 28–8). The rest of the calvaria is then reconstructed with the remaining bone pieces, taking care to maintain symmetry. We use the combination of two Nurolon or three Nurolon vicarial and titanium miniplates and screws to anchor the bone pieces. Once all bone flaps are reattached, the cylinder drill bit (Midas Rex M12) can be used to smooth all edges to give the new construct a rounded and symmetric contour. The pericranial flap is then reflected over the bone flaps and secured in place to the adjacent pericranium with absorbable sutures. The galea and skin are closed in a standard fashion. A 7 mm drain is left in the subgaleal space and tunneled to a separate exit. We do not routinely suture the drain in place.
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10.1055/978-1-60406-039c028_f007 Figure 28–7 Artistic reconstruction showing the “tiara” placed tongue and groove into the asterion. A strut piece is placed from the anterior fontanelle to the top of the tiara. The rest of the calvaria is reconstructed in a mosaic fashion.
A
B
Figure 28–8 (A) Lateral intraoperative photographs depicting the reconstructed occipital unit. (B) The “tiara” forms the new occiput along with radially placed strips of bone, resembling a sunrise. 10.1055/978-1-60406-039c028
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28 Treatment of Lambdoidal Synostosis with Calvarial Reconstructive Techniques 189
Postoperative Management Including Possible Complications All patients are placed in pediatric intensive care unit for at least 24 to 48 hours postoperatively. The drain is removed 24 hours postoperatively unless there is still significant drainage. Prophylactic antibiotics are not routinely used following surgery. The majority of the patients will have elevated temperatures (38–39°C) during the first 4 to 5 days postoperatively. We no longer culture patients on a routine basis unless there is evidence of an infection or the fever persists for more than 4 days. The procedure is generally well tolerated, but the patients usually require a strong analgesic regiment. Patients are kept prone or rotated from side to side to prevent reoccurring occipital asymmetry due to pressure from continuously lying on one side. Patients are usually discharged on the sixth to seventh postoperative day.
Complications The most serious complication is injury to the asterion region venous sinuses during elevation of one of the bone flaps. In most cases, an Avitene pledget (C.R. Bard, Inc., Murray Hill, New Jersey) and direct pressure to the bleeding area with a combination of Gelfoam, cottonoids, and, most recently, Surgiflo (Ethicon, Inc.; Somerville, New Jersey), will stop the majority of bleeding. Occasionally the sinus tear will need to be closed primarily with a small suture. Meticulous atten-
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tion has to be paid to any dural tears, which must be directly repaired. Any subsequent cerebrospinal fluid leak will lead to persistent subgaleal fluid collection and problems with proper bone healing. Prior to elevation of the skin flap, all of the bone, flap gutters, and surrounding areas are copiously irrigated. The removal of the remaining debris and collected bone dust markedly reduces postoperative infection. Subdural hematomas are a possible complication but are extremely rare. If they do occur, they most likely are due to improper repair of a venous sinus injury. Persistent subgaleal fluids in the postoperative period need to be tapped and tested for bacteria, if the child has a persistent fever. Results indicate that excellent long-term outcomes in older patients treated with these complex reconstructed techniques can be achieved if these surgical principles are closely followed. Acknowledgment This chapter is a revision of the chapter, “Lambdoidal Synostosis” by David F. Jimenez, M.D., Constance M. Barone, M.D., Ravelo Argamaso, M.D., and James T. Goodrich, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 4, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Ravelo Argamaso, M.D., for his help and efforts on the original chapter published in the first edition of this work.
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29 Early Treatment of Lambdoid Synostosis with Endoscopic Assisted Craniectomy David F. Jimenez and Constance M. Barone
Patient Selection When a patient presents with cranial vault deformational changes secondary to lambdoid synostosis at <6 months of age, our preferred method of treatment is to release the synostosed suture by performing a suturectomy and then placing the patient in a cranial orthosis postoperatively. The concept is based on utilization of the rapid brain growth that takes place during the first 18 months of life to correct the deformational skull changes associated with the synostosis. Invariably, the younger the patient at the time of the release, the better the results will be. Very young infants tolerate this surgery well, with minimal blood loss and without the need for blood transfusions.
Preoperative Preparation No special preparations are needed if the patient is found to have no significant medical problems or past medical history. A spun hematocrit is drawn following anesthetic induction, and no other serum laboratories are obtained. A single dose of anti-staphylococcal antibiotic (oxacillin 50 mg/kg) is given within 1 hour prior to incision. To help with postoperative pain management, an acetaminophen rectal suppository (10 mg/kg) is given prior to the start of the case. The scalp is minimally shaved and then prepped with Betadine (providone-iodine) paint, which is allowed to dry for maximal effectiveness.
Figure 29–1 Patient lies on a padded horseshoe headholder with the head parallel to the floor. This position allows access to the lambda and asterion regions of the affected suture. 10.1055/978-1-60406-039-1c029_f001
Operative Procedure The patient is induced under general anesthesia and placed supine with the head turned and parallel to the floor (Fig. 29–1). A shoulder roll is used to elevate the ipsilateral shoulder and to minimize cervical rotation, and one or two peripheral intravenous lines are inserted. There is no need for placement of arterial or central venous lines or urinary catheter. It is of paramount importance to radiographically identify the ipsilateral lambda and the asterion. This can be done using plain x-rays and metallic markers (Fig. 29–2). The extent of synostosis is correlated between the preoperative computed tomography (CT) scan and the intraoperative x-rays. The incisions are marked to include the full extent of the synostosed suture (Fig. 29–3).
Figure 29–2 Markers (Xspot®) are used intraoperatively to localize the medial and lateral ends of the stenosed lambdoid suture. A plain x-ray allows for proper placement of the incisions.
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29
Early Treatment of Lambdoid Synostosis with Endoscopic Assisted Craniectomy 191
Figure 29–3 Diagram showing the location of the medial and lateral incisions. These must be made directly over the stenosed suture. 10.1055/978-1-60406-039-1c029_f003
Operative Technique The incisions are placed lateral to the lambda along the stenosed lambdoid suture and medial to the ipsilateral asterion. Each incision is ~2 cm in length. The incision is made with the needle tip monopolar electrocautery set at 15 W, blend 1. Dissection is taken down below the galea but does not include the pericranium. Insulated malleable retractors are used to elevate the scalp and a zero degree rigid endoscope is used to perform a subgaleal dissection, with the monopo-
Figure 29–4 Dissection is undertaken under the galea and directed laterally toward the asterion. A needle tip electrocautery is used to develop a bloodless plane above the pericranium ~3 cm in width.
Figure 29–5 A 4 mm Kerrison rongeur is used to enlarge the bur hole. The endoscope and sectional dissector are inserted under the bone to separate the dura from the galea. 10.1055/978-1-60406-039-1c029_f005
lar laterally toward the asterion. Care is taken not to elevate the pericranium, as this maneuver will create unnecessary bleeding. A second incision is made medial to the asterion, and the subgaleal dissection is extended medially to join the previously described exposure (Fig. 29–4). A 7 mm (pediatric) craniotome is used to create a bur hole at each incision. The bur holes are enlarged longitudinally using a 4 mm Kerrison rongeur (Fig. 29–5). This maneuver allows the insertion of the rigid endoscope under the calvarial bone (Fig. 29–6). A no. 6 or 7 French malleable suction tube is inserted under the bone and advanced in front of the endoscope to visualize the osseous-dural interface. The endoscope and suction tips are advanced in tandem, visualizing the stenosed suture and the underlying dura. This dissection may be carried medially from either incision. Once the entire stenosed suture has been fully isolated from the overlying scalp and underlying dura, preparations are made for resection of the stenosed suture. The suturectomy is begun at the lambdoid incision and extended toward the asterion by cutting a small (2–3 cm) wedge of bone along the affected suture (Fig. 29–7). Further wedge sections can be removed until the asterion incision is reached. Care must be taken not to tear the dura, particularly near the asterion, as it can lead to an injury to the transverse or sigmoid sinus. Once the suturectomy is finished, the edges are smoothed with either the Mayo scissors or a small Leksell rongeur. Diploic homeostasis is obtained using a suction electrocautery unit (Valley Laboratory, Valley Forge, PA) set at 50 to 60 W. Coated malleable retractors must be used to protect the dura and scalp from being thermally injured. The wound is irrigated, further hemostasis is obtained as needed, and then the scalp incisions are closed using 4–0 Vicryl (Ethicon; Somerville, NJ) galeal sutures. Dermabond
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Figure 29–6 Artist’s diagram shows a 30° rigid endoscope being advanced under the stenosed (and ridged) suture and above the dura. A small malleable suction tip is used to dissect and keep the endoscopic field bloodless. 10.1055/978-1-60406-039-1c029_f006
(Ethicon; Somerville, NJ) is used for final dermal closure. The scalp is infiltrated with 0.25% marcaine (without epinephrine) at 1 ml/kg to help with postoperative pain. Following extubation, the patient is admitted overnight for observation and discharged the following morning. Any residual postoperative swelling is allowed to resolve over the next 2 to 3 days, and then the patient is scanned and properly fitted for a helmet, which is to be worn to help correct the associated cranial deformational changes (Fig. 29–8).
Postoperative Management Including Possible Complications All patients are hospitalized overnight and discharged the following morning. Pain management is obtained by alternating use of acetaminophen (15 mg/kg every 3 hours) and ibuprofen (10 mg/kg weight every 3 hours). If stronger analgesic is
Figure 29–7 Diagram showing extent of the craniectomy, which should be 0.7 mm ± 0.2 mm in width. Care must be taken that the craniectomy extends from lambda to asterion. 10.1055/978-1-60406-039-1c029_f007
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needed, Nubain or morphine sulfate is used. The patient’s irritability is most evident during the first 8 hours following surgery and then fully recedes by the first postoperative morning. The patient is allowed to nurse as soon as possible following the surgery. Two days after surgery, the patient is scanned and molded for a cranial orthosis, which is worn during the first 10 to 12 months (Figs. 29–9 and 29–10).
Complications Possible complications include dural tears, dural sinus injury, embolism, and any of the complications associated with the infant cranial surgery. We have had no complications and overall are very satisfied with the results. None of the patients have required blood transfusions or further reoperations.
Figure 29–8 A custom-made Surlyn® helmet (Dupont, Wilmington, Delaware) is used postoperative to direct brain growth and achieve calvarial correction. 10.1055/978-1-60406-039-1c029_f008
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Figure 29–9 Preoperative view of a 5-month-old with lambdoidal synostosis and marked skull base asymmetry and cranial scoliosis. 10.1055/978-1-60406-039-1c029_f009
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Figure 29–10 Postoperative view at 2 years of age showing significant correction. Estimated blood loss was 15 cc, surgery time was 40 minutes, and helmet was worn for 7 months. 10.1055/978-1-60406-039-1c029_f010
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30 Posterior Plagiocephaly Richard G. Ellenbogen, Sudesh J. Ebenezer, and Richard Hopper
Patient Selection Diagnostic Criteria Posterior plagiocephaly is an abnormality of the posterior aspect of the skull where the ipsilateral occipital and parietal bones are flattened. Posterior plagiocephaly may result from fusion of a lambdoid suture. It can also occur in the absence of lambdoid suture synostosis. A child with posterior plagiocephaly, regardless of the etiology, will have flattening of the affected occipital-parietal region. In general, posterior plagiocephaly resulting from lambdoid suture synostosis can require surgical management. Deformational or nonsynostotic posterior plagiocephaly secondary to external compressive forces whether in utero, at delivery, or after birth generally does not require surgical treatment. Thus it is of paramount importance to distinguish the cause of the posterior plagiocephaly, as the treatment paradigms are different. Table 30–1 describes the morphology of unilambdoid synostosis versus nonsynostotic posterior plagiocephaly. Patients are seen in multiple visits in our craniofacial clinic. A thorough history and physical examination is important at each visit. The features in Table 30–1 are assessed at each visit, to determine whether the patient has positional posterior plagiocephaly or synostotic posterior
plagiocephaly. Fig. 30–1, Fig. 30–2, and Fig. 30–3 show the differences in morphology. Photographs are taken at each visit for comparison. Mild deformities can be observed. A child with a moderate to severe deformity undergoes a computed tomography (CT) of the brain along with three-dimensional (3-D) reconstructions. Bony windows are obtained and also reconstructed in the coronal plain. The underlying brain, skull base, and the regions undergoing compensatory change should be evaluated closely. Fig. 30–4 and Fig. 30–5 show pre- and postoperative 3-D CT scans.
Incidence It must be emphasized that isolated true lambdoid synostosis is extremely rare. In a series of 519 children with craniosynostosis at the Children’s Hospital, Boston reported by Shillito and Matson in 1968, the incidence of lambdoid synostosis was 2.3%. In 130 patients with craniosynostosis reported on by Huang et al, the incidence was 3.1%. A critical review of the literature in 1998 by Rekate revealed the incidence of lambdoid craniosynostosis ranges from 3 to 20%. Differences in diagnostic criteria accounted for the variability. We believe that the true incidence is closer to that reported by Shillito and Matson, 2 to 3%. In contrast to posterior plagiocephaly caused by lambdoid suture syn-
10.1055/978-1-60406-039-3c030_t001 Table 30–1 Features and Diagnosis of Posterior Plagiocephaly Feature
Posterior Plagiocephaly without Synostosis
Unilambdoid Synostosis
View from vertex Skull base Sutures
Parallelogram Horizontal 1. Open 2. No ridging Perpendicular to suture
Trapezoid Ipsilateral inferior tilt 1. Fusion 2. External ridging 1. Parallel to suture 2. Restricted perpendicular to suture Inferiorly or posteriorly 1. Ipsilateral occipital and mastoid 2. Contralateral occipital and parietal Ipsilateral constriction Flattened
Skull growth Displacement of ipsilateral ear Bossing Volume of posterior fossa Ipsilateral occipital and parietal bones
Anteriorly 1. Contralateral occipital 2. Ipsilateral frontal Normal Flattened
194
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A
B Figure 30–1 (A) Normal head shape from posterior view. Growth occurs perpendicular to suture. Skull base is horizontal. (B) Normal head shape from vertex view. 10.1055/978-1-60406-039-3c030_f001
Figure 30–2 Posterior view ([A] diagram and [B] photograph) of synostotic posterior plagiocephaly involving left lambdoid suture. Compensatory growth is parallel to fused lambdoid suture. Ipsilateral occipital
mastoid and contralateral parietal bossing results. Inferior displacement of ipsilateral ear and ipsilateral inferior tilt of skull base occurs.
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B
A Figure 30–3 Differences in head shape from vertex view. (A) Positional molding showing parallelogram-shaped head. (B) Right lambdoid synostosis showing trapezoid-shaped head. 10.1055/978-1-60406-039-3c030_f003
A Figure 30–4 (A) Preoperative three-dimensional (3-D) computed tomography (CT) of right lambdoid synostosis. Note fused right lambdoid suture, ipsilateral skull base tilt, ipsilateral occipital-mastoid bossing, and
B contralateral parietal bossing. (B) Immediate postoperative 3-D CT of right lambdoid synostosis. Note radial barrel-staven-like osteotomies.
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A Figure 30–5 (A) Preoperative three-dimensional (3-D) computed tomography (CT) of left lambdoid synostosis. Note fused left lambdoid suture, ipsilateral skull base tilt, ipsilateral occipital-mastoid bossing,
B and contralateral parietal bossing. (B) Two years postoperative 3-D CT of left lambdoid synostosis. Note symmetric contour of parietal-occipital area.
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ostosis, nonsynostotic plagiocephaly can occur commonly, and is seen in up to 48% of healthy neonates. Thus it is imperative that surgeons distinguish the etiology of the posterior plagiocephaly before contemplating surgical management.
Surgical Indications The most common cause of posterior plagiocephaly is a nonsynostotic deformation. This rarely requires surgery. The other major cause is premature closure of one or both of the lambdoid sutures. Many infants with lambdoid synostosis have a significant posterior cosmetic deformity that progresses. If the progressive nature is confirmed, and is severe, surgical management is offered. Progression should be documented over the 6 to 12 weeks that the patient is followed in the craniofacial clinic prior to surgery. Surgery is timed for when the child is 3 to 12 months old. Because this operation represents an expansion of the posterior cranial surface area, we inform parents to expect gaps in bone coverage, which will heal secondarily with time. As a result of these bone gaps, surgery should occur within the first year of life and ideally at ~6 months of age when bone growth is still very active from the immature dura. The parents may believe that the deformity will adversely affect the infant’s psychological development. They should understand that the deformity cannot be covered by hair. Parents must understand that surgery will not cause intellectual impairment or developmental delay. If a nonsynostotic deformity (deformational) progresses even with efforts to change the infant’s position, the patient should be reassessed for synostosis with repeat clinical examination and imaging.
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Contraindications to Surgery Posterior plagiocephaly caused by a nonsynostotic deformation very rarely requires surgery. Causes of nonsynostotic deformation include positional molding and torticollis. Positional molding is the most common type of nonsynostotic deformation. This can occur when an infant lies flat, or when one has intrauterine compression of the skull. Positional molding usually causes a mild deformity that generally does not progress. It generally improves as the infant grows, learns to roll, crawl, and walk. Posterior plagiocephaly caused by torticollis can often be corrected by regular stretching exercises.
Alternative Considerations to Surgery Most infants with posterior plagiocephaly will be nonsynostotic (deformational). Thus the majority will not require surgery. The parents must try to change the infant’s position while lying down. There is the risk of sudden infant death syndrome while in a prone position. The child can be in a lateral position, or supine with the head toward the unaffected occiput. Helmet and band therapy are other alternatives. A potential difficulty is that it is labor intensive. A dedicated orthotics team is required. Parents may not be compliant with helmets.
Preoperative Preparation Infants have routine laboratory studies. This includes a complete blood count (CBC) and coagulation studies. Parents can
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198 Pediatric Neurosurgery over the proposed incision, which makes for a more efficient closure. Lacri-Lube (Allergan, Irvine, CA) is applied to the eyes, which are then taped shut. The endotracheal tube is secured to the mandible with wire or suture for added stability. Three layers of foam are placed over bony prominences of the cheeks and forehead to avoid pressure on the globes (Fig. 30–6). The patient is then turned prone. The head is placed in a neutral position, face down, in a padded horseshoe headrest. Special care is taken to confirm there is no ocular compression. The chest and hips are supported by padded gel cushions. There should be no pressure on the abdomen. The lower legs are flexed 15 degrees using a pillow, to enhance venous return (Fig. 30–7).
Draping and Skin Incision
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choose parentologous blood donation. Two pediatric units of blood should be available in the operating suite. Some centers use a pediatric cell saver. The anesthesiologist administers one intravenous dose of cefazolin 30 minutes prior to skin incision. No specific anesthetic technique is used. All patients have a Foley catheter, a radial arterial line, pulse oximetry, and two intravenous lines. End tidal partial pressure of carbon dioxide PCO2 is monitored.
A biparietal zig-zag incision is drawn with a marking pen (Fig. 30–8). This is done in a coronal plane behind the external auditory meatus, ~2 to 3 cm posterior to the coronal sutures. This provides maximum exposure down to the insertion of the neck muscles into the posterior fossa, and also the affected parietal-temporal regions. The field is prepped in the standard fashion with alcohol and Betadine (providone-iodine). Draping is completed in a standard manner. We drape from the muscles of the neck to the coronal suture. This way the back of the head can be completely visualized. Five to 10 minutes prior to incision, a solution of 0.25% Marcaine (bupivacaine) with 1:200 000 dilution of epinephrine is injected into the subcutaneous tissue to decrease blood loss.
Operative Technique
Operative Procedure Patient Positioning We do not shave any hair unless the infant has a significant amount of hair. In this case a narrow strip of hair is shaved
The zig-zag incision is made in the subgaleal plane. Bipolar electrocautery is used to obtain hemostasis. Raney skin clips are not used to decrease trauma to the tissues and hair follicles. Subperiosteal dissection is done to a level below the torcula but above the foramen magnum. The neck muscles inserting into the occipital and posterior fossa regions are
Figure 30–7 The patient is positioned prone. 10.1055/978-1-60406-039-3c030_f007
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A
B Figure 30–8 (A) Biparietal zig-zag incision is marked. (B) Biparietal zig-zag incision. 10.1055/978-1-60406-039-3c030_f008
Figure 30–9 Skin flap retracted. 10.1055/978-1-60406-039-3c030_f009
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elevated using a sharp periosteal dissector. Inferiorly, the skin flap should be exposed to the occipitomastoid suture (Fig. 30–9). Bur holes are placed adjacent to the transverse sinus and on either side of the superior sagittal sinus (Fig. 30–10A). We use a Stryker Universal Drill (Stryker, Kalamazoo, MI) with a 6 mm round bur. It is set at 60,000 rotations per minute. A no. 3 Penfield dissector is used to bluntly dissect the dura from the bone flap. A biparietal-occipital craniotomy is performed. We use a Stryker 1.8 mm craniotome for this. The craniotomy is taken in two pieces (Fig. 30–10B). If the sagittal suture is excessively adherent to the sinus, we leave a strip of bone over the sinus, which is later used during the operation to reattach the two remolded cranial plates. The craniotomy should extend to the level just above the transverse sinus and far enough anterior to incorporate the entire flattened parietal, occipital, and temporal regions. The two parietal-occipital bones are reshaped to create a symmetrical contour using radial osteotomies and a Tessier bone bender (Lorenz Surgical, Jacksonville, FL). The contralateral bossed parietal bone is often rotated and used to create the cranial expansion on the affected side. With this technique, the two bone flaps are essentially switched. While we are reshaping, we often place the bone flaps back over the occipital region and reflect the scalp flap to its original position to ensure the reshaped bones are satisfactory.
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200 Pediatric Neurosurgery
A
B
C
D Figure 30–10 Left lambdoid synostosis. (A) Bur holes are placed adjacent to the transverse sinus and on either side of the superior sagittal sinus. (B) Biparietal-occipital craniotomy taken in two pieces. (C) Bar-
rel-staven-like osteotomies. (D) Bone plates are reattached after being switched.
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30 Posterior Plagiocephaly 201 Some centers plicate the contralateral dura with either suture or bipolar electrocautery to decrease the compensatory bossing on the “normal” occiput. The efficacy of plication is unknown. We then work on the infratentorial occipital and posterior fossa bones. The dura is stripped from the bone. Vertically directed barrel-stavenlike osteotomies are then created along the length of the craniotomy. The cuts are made from the level of the transverse sinus down to above the level of the foramen magnum. The osteotomies extend the length of the craniotomy flaps (Fig. 30–10C). While the osteotomies are made, the dura and underlying brain is protected with a malleable brain retractor. The barrel-stavened bone is remolded and bent posterior using a Tessier bone bender and mosquito snaps. The temporoparietal region on the flattened side may require osteotomies and remolding to create a symmetrical contour. The bone plates are reattached using resorbable microplates, and microscrews (Fig. 30–10D). This may require pulling down the scalp flap several times and viewing the remodeled bone work prior to actual fixation. Fig. 30–11A and Fig. 30–11B are intraoperative photographs of left lambdoid synostosis, shown from posterior. When there are only mild to moderate anterior fossa compensatory changes, we do not suggest surgery of the frontal region. We reassure the parents that with time, these changes become less noticeable as the hair grows and the posterior contour improves. However, in the rare patient who suffers extremely severe compensatory ipsilateral frontal bossing, we will alter our surgical approach. We have seen only two children with such severe cosmetic frontal changes that reshaping of their anterior fossa during the same anesthetic was required. Both were older children at the time of diagnosis; one was 11 months old and the other 22 months old. In these children, a more aggressive ap-
proach was required. Discussion of this is beyond the scope of this chapter. Throughout the case, bleeding is controlled with bipolar electrocautery along with injectible cellulose and thrombin (FloSeal; Baxter International Inc., Deerfield, IL). Half a liter of room temperature saline with bacitracin is used for final irrigation. A Jackson Pratt (JP) drain is placed in the subgaleal space and tunneled out through a separate small skin incision. The scalp flap is closed in two layers with all tension on the galeal closure and none on the skin. Using piercing towel clips on the skin edges can facilitate closure over a large expanded skull volume. Absorbable suture such as 3–0 or 4–0 Vicryl (Ethicon, Somerville, NJ) is used for the galea. The skin is approximated with interrupted absorbable suture that will not require removal, such as 5–0 Chromic Gut (CP Medical, Portland, OR). The incision is dressed with a light layer of bacitracin ointment. Five years ago we stopped using any external head dressing and found a decreased infection rate on internal quality review and no increase in hematoma rate.
Postoperative Management Including Possible Complications The patient is extubated in the operating room. A CT scan of the brain is obtained to rule out an intracranial hemorrhage. The patient is then admitted to the pediatric intensive care unit (PICU). While the patient is in the PICU, an arterial line is kept in place, along with good intravenous access. A CBC and coagulation studies (prothrombin time [PTT] and international normalized ratio [INR]) are obtained immediately when the patient arrives in the PICU. Heart rate, blood pressure, urine output, and JP drain output are monitored closely.
B
A Figure 30–11 Intraoperative posterior occipital view. (A) Markings are made for a biparietal-occipital craniotomy. A strip of bone along the sagittal sinus is left behind. (B) The bone plates have been switched
and rotated. Barrel-staven-like osteotomies have been made. Plates are reattached using absorbable microplates and microscrews.
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202 Pediatric Neurosurgery If the patient’s hematocrit is <22, blood will be transfused. Fresh frozen plasma will be given to maintain the INR <1.4. If the JP drain puts out >100 cc of blood over 2 consecutive hours, repeat CBC, PTT, and INR are obtained. The child usually stays in the PICU for 24 hours, after which the patient is transferred to the surgical ward and monitored in a routine manner. Immediately after surgery, the child may be active as tolerated, with the head at 30 degrees. Diet may also be as tolerated. While in the PICU pain is controlled with an intravenous (IV) morphine drip starting at 5 μg/kg/hour. As needed oral Tylenol (acetaminophen) along with oral oxycodone are also used. Odansetron and metaclopromide control postoperative nausea and emesis. After day 1 when the patient is on the ward, the morphine drip is rarely needed. The child receives 24 hours of postoperative IV cefazolin for staphylococcus prophylaxis. The JP drain is withdrawn by postoperative day 2 or 3. By this time it is usually draining <5 cc over 24 hours. The child is discharged by postoperative days 3 to 5, as long as the child is able to open his or her eyes.
Complication Avoidance The endotracheal tube is first secured by anesthesia. We then secure the tube to the mandible for added protection. Points on the forehead and face that will contact the gelcovered horseshoe headrest are well padded with foam. These points include the lateral supraorbital ridge, the malar eminences, and the zygomatic arch. This will prevent ischemia to the skin of the forehead and face. To avoid ocular ischemia, the orbital rims are padded with foam that has areas that are cut out for the eyeballs. Upon adequate foam protection as described, the infant is then carefully placed prone in a gel-covered horseshoe headrest. Finally, all pressure points in the extremities are padded with foam. A small pillow is placed under the feet to enhance venous return to the heart. The scalp opening should be done with minimum blood loss. Raney clips are not used to decrease injury to hair follicles and skin edges. While drilling the bone, saline is used to cool the heat that is generated. This will theoretically decrease the amount of bone resorption. Fluid and blood volume should be replaced timely. Waiting to transfuse as blood is slowly being lost can end in
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a sudden catastrophic intraoperative event. We transfuse blood when the bone is being cut. This is the period in which the infant loses the most volume. Injury to venous sinuses and dura must be avoided. Bur holes are placed above the transverse sinus, and on either side of the superior sagittal sinus. The dura is then carefully stripped from overlying bone. The occipital bone is then removed in two pieces. The dura and underlying brain must be protected with a malleable brain retractor when bone cuts are made. Dural tears are sutured watertight with 4–0 Nurolon (Ethicon, Somerville, NJ). Thrombin-soaked Gelfoam (Pfizer, New York, NY) and DuraSeal (Confluent Surgical, Waltham, MA) are then applied over the tear. The risk of venous embolism is minimized by maintaining the patient in a neutral position, maintaining meticulous hemostasis, and copiously irrigating during any osteotomies. The scalp must be closed without skin tension, which can be challenging given a newly expanded cranial vault. This can be facilitated with the use of piercing towel clips to achieve stress relaxation of the scalp within 10 minutes. All tension is then transferred to the galeal closure. Interrupted suture technique is less damaging to the skin than a running suture, which can strangulate the skin edges. Finally, microplates and microscrews can present as scalp irritation years after an operation due to screw pull-out. We currently use the minimum number of resorbable plates and screws to achieve stability of the expansion. Acknowledgments This chapter is a revision of the chapter, “Surgical Management of Posterior Plagiocephaly” by Richard G. Ellenbogen, M.D., and Michael H. Mayer, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 5, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Michael H. Mayer, M.D., for his help and efforts on the original chapter published in the first edition of this work. All illustrations in this chapter were drawn by Michaele Miller. Amy Cheney provided editorial assistance, and graphic design was done by Carrie Wachob.
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31 Sagittal Synostosis Larry A. Sargent and Timothy A. Strait
Sagittal synostosis is an abnormal condition of the skull involving premature closure of the sagittal suture. A suture represents the zone between two adjacent skull plates that has the capacity to form new bone in response to the underlying expansion of the brain. The growth of the brain is responsible for the enlargement of the skull and its subsequent shape. As the brain expands, new bone is formed perpendicular to the cranial sutures. However, if a suture prematurely closes, it loses the capacity to form new bone. Therefore, as the brain expands, the skull will not grow perpendicular to the suture. Premature closure of the sagittal suture will reduce the width of the skull, producing an abnormally elongated skull called scaphocephaly. The appearance of the “boat-shaped” skull is characterized by anteroposterior elongation and transverse narrowing. With the compensatory anteroposterior growth, there usually is increased bossing of the frontal and occipital regions. The abnormality of the forehead is exaggerated further by the narrowing that is present at the bitemporal level and by the loss of the squamous temporal convexity. Synostosis of the sagittal suture is the most frequent type of single-suture craniosynostosis. It accounts for 50 to 60% of all patients within North America with craniosynostosis. With sagittal synostosis, males are affected three to four times as frequently as females. Although an inherited tendency has been reported in the literature, most cases of isolated sagittal synostosis are sporadic in occurrence, with no known specific etiology. Because the normal lambdoid and coronal sutures permit compensatory growth in the anteroposterior axis, infants with sagittal synostosis rarely have restriction in brain growth, and neurological development is usually normal. The degree of the abnormality of the skull varies in sagittal synostosis. Complete fusion along the entire sagittal suture is the most severe form and usually produces a characteristic boat-shaped skull present at birth. The less severe forms range from fusion of the anterior portion of the sagittal suture with isolated frontal bossing, to fusion of the posterior portion of the sagittal suture with isolated occipital bulging. Despite the extent or magnitude of premature suture fusion, the goal of surgery is to release the fused area and normalize skull shape. It has been our policy to perform a total vault remodeling procedure with immediate correction of the scaphocephalic deformity.
Patient Selection All infants born with abnormal skull shapes are suspected of having craniosynostosis. However, abnormal skull shapes at birth may occur from either birth trauma or fetal head position. Generally, this positional type of deformity will correct itself in a few months. The typical child with complete sagittal synostosis has an elongated head with a palpable bony ridge along the sagittal suture, biparietal narrowing, occipital bulging, and frontal bossing. The diagnosis of sagittal synostosis can usually be made on clinical grounds and confirmed by skull radiographs. We routinely obtain computed tomography (CT) scans to confirm the diagnosis, to rule out other intracranial abnormalities, and to assess the full extent of the deformity. Threedimensional reconstruction imaging can also be helpful in delineating the abnormalities. In general, the decision to recommend surgical intervention is guided by the risk of potential psychological harm from having an abnormal and unsightly appearing head. Untreated sagittal synostosis is fully capable of producing increased intracranial pressure and subsequent brain damage in a small percentage of cases. Release of the fused suture with total skull remodeling not only virtually eliminates the risk of brain damage due to growth restriction, but it also restores the skull shape, creating the potential for normal growth and appearance. In our experience, the best results from reconstruction occurred when infants underwent surgical repair between 8 and 10 months of age. This time period has several advantages. First, their blood volumes are greater than in newborns. Second, remodeling is simpler (less operative time) because the bone is far more malleable and easier to contour. Third, bone defects or gaps left after skull remodeling are not a problem due to rapid bone healing. Finally, the rapid brain growth that occurs during the first 3 years of life benefits additional bone remodeling. Older patients will require modification of this plan due to the presence of more rigid bone and slower cranial growth patterns. In the patient >3 years of age, more extensive surgical maneuvers are required with definitive bone work, better fixation, and no bony gaps. Furthermore, older patients may require reconstruction of secondary facial deformities.
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204 Pediatric Neurosurgery
Preoperative Preparation Evaluation Patients with craniosynostosis should be evaluated and treated at a craniofacial center with a team approach. Our center has a multidisciplinary team to ensure that the patients and their families are evaluated and treated in a coordinated manner. The team combines the expertise of each specialist to provide a level of comprehensive care unmatched by a single physician. The pediatricians play a key role in early diagnosis and referral so that successful treatment is accomplished. A craniofacial surgeon, neurosurgeon, and pediatric anesthesiologist compose the operative team. Each of these specialists sees the patient in a preoperative evaluation. A pediatric intensivist is consulted when associated medical problems are present. The planned surgical procedure is fully explained to the parents by the craniofacial surgeon and the neurosurgeon in their office consultation. A CT scan is routinely performed on each patient who is clinically diagnosed as having craniosynostosis. This helps to fully assess the deformity as well as plan the operative procedure. Because blood transfusion is generally necessary, the parents are asked to provide designated-donor blood. Aspirin and other medications capable of prolonging the blood clotting time are avoided.
Anesthesia Nasotracheal general anesthesia is preferred, with the tube sutured to the caudal septum with 3–0 silk suture. An arterial line is placed in the radial artery to monitor blood pressure, with one to two peripheral intravenous lines inserted in the extremities. A central line silicone catheter is inserted into the femoral vein and sutured in place. A Foley catheter is inserted to monitor urine output. Plastic sterile drapes are
A Figure 31–1 (A) The patient is positioned prone with the neck slightly extended. This provides excellent exposure of the entire skull. A bean
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placed anteriorly and posteriorly from the shoulders down to minimize heat loss and to keep the infant dry. Broadspectrum intravenous antibiotics are administered at the induction of anesthesia.
Operative Procedure Positioning Proper positioning of the patient is very important in total vault remodeling (Fig. 31–1). Following administration of the anesthetic agent, the infant is placed in the modified prone position with the neck only slightly extended. The chin and neck are placed in a stable position by a molded, suctioned bean bag. Padded foam is placed beneath the chin to avoid pressure ulceration of the skin. All other joints are appropriately padded with foam.
Procedure The first stage of the procedure involves mobilization of the scalp flaps. To gain access to the entire calvaria, a zigzag bicoronal skin incision is designed from ear to ear and centered approximately between the anterior and posterior fontanelles. This type of incision yields a superior cosmetic result compared with the straight bicoronal incision. Only a small amount of scalp hair is cut, creating a 0.5 cm margin on either side of the incision. Prior to incising the scalp, 0.5% lidocaine with 1:200,000 epinephrine is injected intradermally to diminish bleeding. The scalp edges are compressed while the skin is incised with a scalpel. Hemostatic clips are applied to the scalp margins. The scalp flaps are elevated in the supraperiosteal plane using a Colorado microcautery tip to separate the scalp and its underlying areolar tissue from the periosteum. Scalp flaps are mobilized anteriorly to the supraorbital rims and posteriorly to slightly below the level of the external occipital protuberance. After the flaps have
B bag padded with foam is used to support the chin and jaw in this position. (B) The zig-zag bicoronal incision is outlined.
31 been mobilized, the temporalis muscle, with a 2 cm cuff of periosteum, is elevated off the squamous portion of the temporal bone with a periosteal elevator through a large semicircular incision. The temporalis muscle is taken down to the level of the floor of the middle fossa. With this exposure, total vault remodeling can be performed (Fig. 31–2). The neurosurgical portion of the procedure involves dismantling the skull in several pieces. Skull plates are removed with care so as not to tear the dural covering of the brain and the dural venous sinuses (Fig. 31–3). The vault is removed in four separate pieces, leaving intact bone overlying the sagittal suture. It is helpful to utilize the M-8 attachment of the Midas Rex drill (Medtronic Inc., Ft. Worth, TX) to make multiple bur holes for elevation of the individual bone plates. The bur holes are connected with the B-5 attachment of the Midas Rex drill, and the bone edges are
A
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waxed. Initially, bilateral parietal craniotomies are elevated. Multiple bur holes are made ~2 cm off the midline from the sagittal suture. Additional bur holes are made along the coronal suture anteriorly, slightly below the parietosquamosal suture inferiorly and at the parieto-occipital junction posteriorly. Through each individual bur hole, a ball-hook dissector is utilized to separate the underlying dura from the bone plate. Once the bone plate has been elevated, a single layer of Surgicel (Ethicon, Somerville, NJ) is placed overlying the dura and moistened with a liquid thrombin spray. Next, the biparieto-occipital craniotomy is elevated. Multiple bur holes again are placed along a line at the level of the external occipital protuberance. To facilitate elevation of this posterior bone plate, it is helpful to place bur holes on each side of the lambdoid sutures and connect them using the M-8 attachment. A ball-hook dissector is then used to
B
C Figure 31–2 Sagittal synostosis. (A) The design of the craniotomies is shown leaving a sagittal bone strut. The two parietal bone flaps are removed first, followed by the occiput and the frontal bone flaps. (B) Anteroposterior shortening is accomplished with posterior inclination of the frontal bone and anterior inclination of the occipital bone. This effectively results in biparietal widening. (C) Radial osteotomies are used 10.1055/978-1-60406-039-3c031_f002
to recontour the bone flaps with the help of bone-contouring forceps. Barrel-stave-like osteotomies are placed in the temporal bone and fractured laterally. The frontal and occipital bone plates are secured at their base with 28 gauge wires. Both of these bones are secured to the sagittal bone strut with 28 gauge wires.
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Figure 31–3 (A) Lateral intraoperative photograph of the scaphocephalic skull with the frontal bone on the left. The bone flaps to be removed are marked. The temporalis muscle with a cuff of periosteum has been 10.1055/978-1-60406-039-3c031_f003
separate the dense adhesion between the cranial suture and the overlying bone. This technique is repeated in the midline at the level of the torcula. Bur holes are made on each side of the sagittal sinus and connected using the M-8 attachment. Frequently, a keel of bone is present that requires careful separation of the dura while drilling away the small bridge of bone. Emissary veins from the sagittal sinus are readily controlled with bipolar coagulation. Finally, elevation of a single bifrontal bone plate is performed with the inferior margin placed 1 cm above the supraorbital rim. Again, it is useful to place bur holes close to the midline along the inferior saw cut. The two bur holes are then connected using the M-8 attachment to divide the small keel of bone that corresponds to the superior aspect of the crista galli. This maneuver facilitates elevation of the bifrontal bone plate. After the bone plates have been removed, the craniofacial surgeon recontours the plates at a side table. Simultaneously, the neurosurgeon makes vertically oriented barrel-stave-like osteotomies in the squamous portion of the temporal bone, which are outfractured at their base to increase the lateral projection or width of the skull base. For a child with marked bilateral frontal bossing, the bossing is lessened by plicating the dura in the frontal region from superolaterally to inferomedially with 4–0 Vicryl suture. Frequently, a similar effect is achieved with bipolar coagulation to the dura itself. Dural tears are repaired with 4–0 Vicryl suture. In the event of a dural tear or laceration overlying a venous sinus, compression with Gelfoam soaked in thrombin is maintained until a dural graft is sutured in place overlying the dural rent. Interruption of the venous connections between the bone plates and underlying dural sinuses accounts for the major source of bleeding. The cumulative effect of removing the entire skull produces a relatively substantial blood loss and mandates the need for routine blood transfusions. Generally, blood transfusions are initiated as the bone plates are being removed. The rate of transfusion varies according to the amount of bleeding encountered as
elevated off the skull (dashed line). (B) View from the top showing the four bone flaps to be removed and the sagittal bone strut that is left in place.
each bone plate is removed. Communication between the surgeons and the anesthesiologist is imperative during this portion of the procedure. The four bone plates are taken to a side table where the craniofacial surgeon begins recontouring (Fig. 31–4). The occipital bone flap is generally too convex, with a narrow transverse diameter. To create a more normal convex curvature of this bone, radial osteotomies are performed with bone-cutting scissors. The bone is flattened using Tessier (Lorenz Surgical, Jacksonville, Florida) bone-contouring forceps, creating a more gentle curvature with a wider transverse diameter. The frontal bone plate is remodeled next in a fashion similar to the occiput. The frontal bone is too narrow in the bitemporal plane, in addition to the frontal bossing. To correct this abnormal contour, radial osteotomies are performed with recontouring using the Tessier bone-contouring forceps to flatten and widen the forehead like the occipital bone. The two parietal bone flaps are abnormally flat, lacking the convexity needed to increase the transverse width. Radial osteotomies are performed on these two bone flaps, with inward bending to create a more normal curvature. The occipital bone flap is returned first. Prior to replacement, a strip of bone ~6 cm ⫻ 1 cm at the base of the skull is cut with a reciprocating saw, and it is infractured and secured with 28 gauge wire. The posterior bone plate is then anteriorly inclined with fixation to the base of the skull in the midline using two 28 gauge wires. A portion of the posterior end of the sagittal strut is resected to allow shortening of the anteroposterior length. The occipital bone is secured to the sagittal strip of bone with two 28 gauge wires that are slowly twisted down. The frontal bone flap is returned next. Two 28 gauge wires are used to secure the frontal bone to the supraorbital rims. The frontal bone flap is inclined posteriorly, resetting a small portion of the anterior end of the sagittal strut where it is secured to the frontal bone. Approximately 1 to 2 cm of anteroposterior length shortening of the skull is accomplished once the wires securing the frontal and occipital bones to the sagittal strut are secured down.
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Figure 31–4 (A) The four bone plates, frontal (bottom of photograph), biparietal, and occipital are taken to a side table. The abnormal elongation of the skull is shown in this intraoperative photograph. (B) Radial osteotomies are used to contour the bone flaps with the help of bone10.1055/978-1-60406-039-3c031_f004
Sagittal Synostosis 207
contouring forceps. This intraoperative photograph demonstrates how the bone flaps are replaced. Anteroposterior shortening is accomplished with biparietal widening.
Figure 31–5 Preoperative photographs (A–C) of infant with sagittal synostosis and postoperative results (D–F) several months after total vault remodeling. 10.1055/978-1-60406-039-3c031_f005
208 Pediatric Neurosurgery These wires are cinched down slowly and gradually to allow the brain and dura to compensate with lateral expansion. To facilitate the shortening of the anteroposterior length without creating undue intracranial pressure, a small dural incision is made in the temporal region to vent cerebrospinal fluid. This shortening due to the posterior inclination of the frontal bone and anterior inclination of the occiputs results in a transverse widening of the brain and thus, the parietal bones (Fig. 31–2). Due to the shortening of the skull, the anterior and posterior edges of the parietal bones will need to be trimmed using bone scissors. The parietal bones are next secured only to the sagittal strip of bone with 28 gauage wires. The lack of fixation on the remaining three sides of the parietal bones allows for lateral brain expansion and skull growth in this area. Once all four bone plates have been replaced as described, a dramatic improvement in overall skull shape can be seen. The temporalis muscles are replaced and secured to drill holes in the skull in multiple places with 4–0 Dexon. A subgaleal drain is left beneath the posterior scalp flap. The scalp is closed in layers using 4–0 Dexon to approximate the galea. A 5–0 plain catgut is used to close the coronal skin incision so as to avoid sutures that require removal. A bulky head dressing of Kerlix sponges and rolls is applied.
Postoperative Management Including Possible Complications At the completion of the operative procedure, infants are taken directly to the pediatric intensive care unit. They are
positioned in an infant car seat with the head elevated. Elbow restraints are used to avoid pulling on the subgaleal drain or the head dressing. In general, most infants remain intubated overnight and are then extubated on the first postoperative day. Both suction drain and bulky pressure head dressing are removed after 48 hours. Intravenous prophylactic antibiotics are continued for an additional 3 days. Transfer out of the intensive care unit to the floor is usually possible on the second or third postoperative day, with the total hospital stay usually 5 days.
Complications Operative risks include anesthetic risks, blood loss, infection, air embolus, dural/sinus tears, and cortical injuries. A total vault reconstruction requires longer operative time, with the potential for greater blood loss. However, this approach provides immediate normalization of the skull and virtually eliminates the chance of either recurrent synostosis or persistent skull deformities associated with strip craniotomies. Any potentially increased risks associated with total vault remodeling are lessened by the surgical team approach and meticulous attention to detail. The significant improvements in skull shape seem to justify this more aggressive and comprehensive approach to sagittal synostosis (Fig. 31–5).
32 The Separation of Craniopagus Twins Sami Khoshyomn and James T. Rutka
Patient Selection Craniopagus twins are the rarest form of conjoined twins in the human organism. They account for 2 to 6% of all conjoined twins, occurring in only 1 in 2.5 million live births. Conjoined twins are always genetically identical and share the same gender. Females are affected more commonly, and no association with race, age, parity, maternal age, heredity, or environmental factors has been found. Recently Spencer suggested that craniopagus twins are formed due to secondary fusion of two primitive neural folds of two dorsally oriented embryonic disks prior to the fourth week of gestation. O’Connell et al developed an extensive classification of craniopagus phenotypes, and Bucholz et al proposed four subclassifications for total craniopagus twins: frontal, parietal, temporoparietal, and occipital. Bucholz et al defined frontal craniopagus twins as facing each other with the axis of bodies forming an acute angle. Temporoparietal twins are joined above the external auditory meatus and occipital craniopagi are joined at or above the occipital protuberance. The parietal craniopagi, also referred to as vertical craniopagi by O’Connell, are fused at the vertex with varying degrees of rotations of one head as compared with the other. The classification of the morphology of fusion is important, as it directly relates to underlying abnormalities of the cortex and shared arterial or venous anatomy. A shared venous system, especially a common superior sagittal sinus, is believed to be the single most important factor affecting survival and long-term morbidity when separation of craniopagus twins is attempted. The main questions to be answered prior to considering separation are:
tated at 30 (Fig. 32–1). The twins were investigated using computer tomography (CT), magnetic resonance imaging (MRI), and angiography to determine whether they shared cerebral structures. Three-dimensional reconstructed CT scan showed the relationship of the cranial vaults of the twins (Fig. 32–2). MRI scan of the brain showed a common dural shelf separating the brains of the twins along half of the plane of attachment and interdigitation of the two brains across an undulating layer of leptomeninges for the other half (Fig. 32–3). They did not appear to share any brain tissue. Magnetic resonance venography (MRV) revealed as anticipated a common or shared superior sagittal sinus. Cerebral angiography as the next imaging study demonstrated, in addition to a common superior sagittal sinus, the passage of middle cerebral artery (MCA) branches from one twin to the other (Figs. 32–4 and 32–5). Utilizing interventional neuroradiological techniques, we embolized the distal branches of the MCA from twin A bridging to twin B. This achieved a partial separation of their cerebral arterial circulations. A preoperative endovascular cannulation and occlusion of the shared superior sagittal sinus was attempted but was unsuccessful. Other authors have advocated an open staged ligation of shared venous structures prior to separation, hoping that over time this would promote deep venous collaterals and drainage in the twin without a complete superior sagittal sinus.
1. Is there any shared brain tissue? 2. Are there any shared major arterial or venous channels? 3. Can the resulting skin and bony skull defect be closed? In this chapter, using our experience with separation of total craniopagus twins at the Hospital for Sick Children in Toronto, we provide an overview of the surgical considerations and steps undertaken for separation.
Preoperative Preparation Craniopagus twins referred to our neurosurgical service were 3 years old and were a total vertex craniopagus ro-
Figure 32–1 Preoperative photograph of craniopagus twins A (right) and B (left) playing.
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210 Pediatric Neurosurgery In addition to the key issues of shared neuronal tissue or arterial and venous anatomy, one important perioperative consideration is the complex problem of bony and soft tissue defect and reconstruction after separation. In this regard, we were aided by our craniofacial plastic surgeons, who inserted tissue expanders into the subcutaneous tissues of the scalp at least 2 months prior to the attempted separation so that the scalp wounds could be closed without using skin grafts. On the morning of the separation, the skin incisions were outlined by the plastic surgeons (Fig. 32–6). The craniofacial team also helped us with the harvesting of autogenous split-thickness bone grafts for rigid repair and fixation of the bony skull defects after the separation was completed.
Operative Procedure Figure 32–2 Computed tomography scan with three-dimensional reconstruction demonstrating the relationship of the cranial vaults of the twins. 10.1055/978-1-60406-039-3c032_f002
On the morning of surgery each craniopagus twin was placed on her own operating room table and own horseshoe headrest. Anesthesia was induced by two separate teams by techniques previously described. Arterial and venous lines and Foley catheters were placed. The scalps were shaved entirely to allow the craniofacial plastic surgeons to mark the skin flaps. The twins were prepped and draped separately so they could be rotated together and remain sterile for the closure of the wounds following the separation.
A
B Figure 32–3 T1-weighted magnetic resonance imaging (MRI) scans; sagittal (left) and coronal (right) views. A dural shelf separating the anterior half of the plane of attachment is appreciated. Interdigitation of 10.1055/978-1-60406-039-3c032_f003
the parietal lobes is also seen. MRI suggests a shared sagittal sinus but no shared cerebral tissue.
32 The Separation of Craniopagus Twins 211
Figure 32–4 Cerebral angiogram showing the sagittal sinus of one twin joining the sagittal sinus of the other twin. 10.1055/978-1-60406-039-3c032_f004 Figure 32–6 Artist’s illustration of the scalp incision markings and the 10.1055/978-1-60406-039-3c032_f006 tissue expanders.
Figure 32–5 Cerebral angiogram of the twins in early venous phase (left) and arterial phase (right). The images show branches of the middle cerebral artery of twin A traversing and supplying brain tissue of twin B. 10.1055/978-1-60406-039-3c032_f005
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Figure 32–7 The scalp is opened along the incision markings, and a craniotomy is performed. 10.1055/978-1-60406-039-3c032_f007
Figure 32–8 The sagittal sinus of one twin is divided just before it joins the sagittal sinus of the other twin. 10.1055/978-1-60406-039-3c032_f008
Next, the scalp incision was made and the tissue expanders were removed. Using intraoperative neuronavigation, we selected the site of the first craniotomy and dural opening so that the location of the shared sagittal sinus could be exposed first (Fig. 32–7). Following removal of a bone segment, we observed the superior sagittal sinus of one twin entering the sagittal sinus of the other twin. It was necessary to ligate the sinus of one twin and divide it just before it joined the normal sagittal sinus of the other twin (Fig. 32–8). The twins were then rotated together circumferentially under the supervision of the neuroanesthesiologists, exposing more skull so further craniotomies could be performed and the dura could be opened circumferentially. In this fashion, the underlying cerebral hemispheres of the twins were exposed along the plane of attachment. The preoperative embolization of the MCA branches bridging from twin A to B greatly facilitated the separation of the interdigitation between the twins where the dura was deficient. An ultrasonic aspirator (Cavitron; Dentsply International Inc., York, PA) was used to expedite the separation of two cerebral hemispheres in a subpial plane in this region. Division of one twin’s falx below the level of the other twin’s superior sagittal sinus represented the last step of the separation. Upon complete separation of the twins’ brains, the operating room tables were pulled apart allowing two neurosurgical teams to simultaneously repair the dural defects. Large dural grafts were used to repair the dural defects (Fig. 32–9). The harvested bone fragments from the craniotomies were split by the craniofacial plastic surgeons and utilized to repair the cranium of each twin using titanium plates and screws (Fig. 32–10). The final step in this complex procedure was the scalp closure over subcutaneous drains (Fig. 32–11).
Figure 32–9 A large dural graft is used to repair the dural defect. 10.1055/978-1-60406-039-3c032_f009
32 The Separation of Craniopagus Twins 213
Postoperative Management Including Possible Complications The management of craniopagus twins in the postoperative period requires close attention to several potential issues that may arise. Raised intracranial pressure (ICP) can develop postoperatively in one or both of the separated twins from venous congestion if one or more of the shared venous sinuses are sacrificed. Venous congestion may be complicated by an intracerebral hematoma that may require neurosurgical evacuation. Raised ICP may also arise from hydrocephalus, which can develop in the postoperative period. Symptomatic hydrocephalus may require the insertion of a ventriculoperitoneal (VP) shunt. Finally, care must be taken to ensure that the rotational scalp flaps and split-thickness cranioplasties heal without signs of infection, bone resorption, or vascular compromise.
Conclusion
Figure 32–10 The skull is reconstructed by the plastic surgeon using harvested bone fragments from the craniotomies utilizing titanium plates and screws. 10.1055/978-1-60406-039-3c032_f010
In summary, prior to undertaking the separation of craniopagus twins, a detailed neuroradiological map consisting of CT, MRI, and cerebral angiography must be obtained. In addition, the use of intaroperative neuronavigation can be invaluable in localizing shared anatomical structures, particularly a superior sagittal sinus. Lastly, endovascular techniques may be used as an alternative to staged surgery to detach the cerebral circulations joining the twins.
Figure 32–11 The scalp is closed, and a drain is placed. 10.1055/978-1-60406-039-3c032_f011
214 Pediatric Neurosurgery The separation of craniopagus twins must be considered one of the most challenging and difficult procedures in the repertoire of neurosurgical cases. Morbidity and mortality are high. In the case of the twins described here, both twins survived the separation. However, the twin whose superior sagittal sinus outflow was taken during the separation suffered a deep intracerebral hematoma that was managed conservatively, and developed hydrocephalus requiring a VP shunt. This twin died from a pulmonary complication ~1 month after surgery. The other twin whose superior sagittal sinus was maintained is alive and well, and leading a normal life in her home country of Pakistan (Fig. 32–12). Acknowledgment This chapter is a revision of the chapter, “The Separation of Craniopagus Twins” by Harold J. Hoffman, M.D., and James T. Rutka, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 6, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. The intellectual contributions and neurosurgical skills of Dr. Harold Hoffman who led the Toronto Hospital for Sick Children team in the separation are acknowledged here. Dr. Hoffman died November 14, 2004. The authors would also like to acknowledge the photographic art contributions by Mr. Robert Teteruck, senior photographer at the Hospital for Sick Children.
Figure 32–12 Postoperative photograph of the surviving twin (twin A) 1 year after separation. 10.1055/978-1-60406-039-3c032_f012
33 Endoscopic Approaches to the Ventricular System David F. Jimenez Utilization of endoscopic techniques to treat ventricular lesions has markedly increased in recent years, as evidenced by the large number of published articles with neuroendoscopic topics. Already commonplace in pediatric neurosurgery, increased training of graduating neurosurgical residents and many postresidency training courses have led to continued popularization of these techniques. With increased experience has come improved outcomes, less morbidity, and higher patient satisfaction. Corporate interest in the field by prominent endoscopic companies has also led to the development of several endoscopic systems dedicated to neurosurgery. Miniaturization of forceps, graspers, balloons, scissors, bipolar and monopolar units, lasers, and other instruments now contribute to an ever expanding array of endoscopic instrumentation. Because the use of such scopes and instruments creates a working environment that is inherently different from that for which we have classically trained, careful planning, preparation, and execution are paramount to avoid complications and poor outcomes. Described herein are practical pointers that relate to a variety of approaches to the ventricular system and the pathology that may affect it.
Prepoperative Preparation Careful and thoughtful preoperative planning is essential for a successful outcome when performing neuroendoscopic procedures. As such, magnetic resonance imaging (MRI) with adequate visualization of the ventricular system should be obtained for proper planning and execution. The exquisite detail given by the multiplanar MR images greatly enhances preoperative planning, preparation, and familiarization with pertinent surgical anatomy. Based on anatomical corridors, appropriate measurements can be made on the scans to plan bur hole placement and scope angle trajectories. In cases of multiloculated hydrocephalus, axial computed tomography (CT) scans with intraventricular contrast medium are needed to ascertain the level of compartmentalization. Based on these images, the best angle of approach and number of fenestrations can be planned and executed.
Surgical Suite Organization Appropriate setup and ergonomic organization of the operating room are of utmost importance to minimize surgeon
fatigue. The operating table should be reversed or placed in such a manner as to place its base away from the patient’s head. This maneuver allows the surgeon and assistant to sit comfortably without obstruction of the feet or legs by the table’s base. Accessories such as intravenous lines, electrical cords, laser fibers, and irrigation lines should exit the operative field toward the patient’s legs, which will diminish tangling of lines at the operative site. The anesthesia team can be placed toward the patient’s legs with the use of extended tubing, which allows full access to the patient’s head. Equipment such as video monitor, camera, and light source should be located on the side opposite and across from the surgeon (Fig. 33–1). Newer visualization systems such as the OR1 (Karl Storz, Germany) allow for strategic placement of multiple monitors so that the entire operating room team can see the procedure continuously. This setup is extremely important, as it allows the surgeon to sit comfortably and have direct and neutral visual access to the monitor during the procedure. This design will minimize cervical and upper back strain, as is commonly seen when the monitor is located lateral or behind the surgical team. Sitting also allows the surgeon to use both feet to control separate instruments (e.g., laser and irrigation) in addition to bilateral hand control. A craniotomy tray should be available (not opened) during all endoscopic procedures. Should a complication arise and should it suddenly become necessary to perform a craniotomy, little time will be spent by the staff looking for the appropriate instruments.
Ventricular Irrigation Paramount to excellent visualization is a clear fluid ventricular environment and as such, adequate irrigation is of utmost importance. Lactated Ringer’s solution is the irrigant of choice for neuroendoscopic procedures, as its pH and electrolyte composition are closest to cerebrospinal fluid (CSF). Normal saline should be avoided due to its low pH (≈5.1) and associated irritating effect. An irrigating system can easily be set up either using motorized units or with instrumentation available in most operating rooms. The components of such a system include a pressure bag, a fluid warmer and the Malis bipolar irrigator unit (Codman & Shurtleff, Inc., Raynham, MA). A 1 liter bag is placed in the pressure bag at 300 mm Hg. The fluid is then passed through a standard fluid warmer. The warmed fluid is then advanced
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Figure 33–1 Surgical setup. The surgeon should sit on a chair with armrests. Depending on the side of entrance, a monitor should be placed directly across for direct viewing. Anesthesia is placed at the foot of the table along with accessories such as suction bipolar and monopolar 10.1055/978-1-60406-039-3c033_f001
through the Malis irrigating bipolar unit and delivered to the endoscope’s irrigating port. The rate of delivery of irrigating fluid into the ventricular system can be adjusted and controlled with a foot pedal. Regardless of which unit or system is used, extreme care must be taken to ensure that the fluid inflow equals the outflow. Unattended fluid delivery without proper egress can lead to acute intracranial pressure elevations and tentorial herniation.
Operative Procedure General Principles General endotracheal anesthesia should be used for the majority of endoscopic procedures. Occasionally, an adult patient who has a high surgical risk can be operated upon under a conscious sedation protocol without problems. Two peripheral intravenous lines are sufficient, and no central venous access is necessary. A urinary catheter is needed for complex procedures but not for simple fenestrations. A single dose of an antibiotic of choice (nafcillin, oxacillin, or
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units. The laser (when used) is placed near the patient’s head due to the length of the laser fiber. Newer systems (OR1; Karl Storz, Germany) allow for the strategic placement of multiple monitors.
first-generation cephalosporin) is given ~30 minutes prior to surgery. Only a very thin strip of hair needs to be shaved over the proposed incision site. The head is prepped with povidone-iodine and then draped wide enough for a possible emergency craniotomy. An irrigating fluid collecting pouch should then be placed in the operative field. Prior to skin incision the endoscopic system should be assembled and appropriately tested to verify a fully functioning unit. When using a flexible endoscope, a self-retaining retractor should be used to hold the body of the scope. A simple Greenberg or Leyla self-retaining retractor can be adequately set up to hold the scope so that the flexible component can be easily manipulated. Newer pneumatic systems (Mitaka, Japan) offer greater flexibility and stability and can be used with either flexible or rigid endoscopes (Fig. 33–2). Following the skin incision, care is taken to preserve a pericranial flap that may be used at the end of the procedure to cover large dural defects from the cannulating units. After bur hole placement, a small dural opening is made and a standard ventricular catheter is inserted in the corresponding ventricle or cyst and the intracranial pressure is measured manometrically; CSF should be sent to the laboratory for the appropriate and indicated stud-
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33 Endoscopic Approaches to the Ventricular System 217 monitor, the same orientation is seen and the movements of the scope are correlated with visual images. If this important step is not done, disorientation and reverse sensing will occur, making the procedure very difficult to perform.
Foramen of Monro Access
Figure 33–2 A left parietal approach to an intraventricular meningioma. The pneumatic Mitaka arm is attached to the left side of the bed and positioned at an appropriate height to accommodate the endoscope. 10.1055/978-1-60406-039-3c033_f002
ies. Following removal of the ventricular catheter, a no. 14 French peel-away introducer is inserted into the ventricle. Some systems have rigid cannulas that may be used instead of the peel-away disposable introducer. The scope is then inserted into the cannula or introducer and the intraventricular anatomy is ascertained. Prior to insertion of the scope into the ventricular system, it is very important to align the camera’s view with the actual spatial orientation of the ventricle. An aerial view of the patient’s head and operative field will easily permit the surgeon to ascertain the correct orientation. The camera can be rotated in such a manner so that when looking at the
A Figure 33–3 (A) Intraoperative view of a large suprachiasmatic cyst extending into the third ventricle. A thick capsule is seen expanding the foramen of Monro. The junction of the choroid plexus, thalamostriate vein (inferiorly), and the septal vein (superiorly) is seen en-face. (B) Following yttrium-aluminum-garnet (YAG) laser fenestration, the deflated
Access to the foramen of Monro for lesions such as colloid cysts, suprachiasmatic cysts, or even septum pellucidotomies is best gained by placing the bur hole far more lateral than standard ventriculostomy access (Figs. 33–3). A coronal MRI should be used to measure the distance from the midline, and it is usually 6 to 7 cm lateral on the side with the greatest frontal horn dilation (Fig. 33–4). This maneuver will allow en-face visualization of the cyst and easier entrance into the third ventricle. Depending on anteroposterior extension of the lesion, the bur hole may be located more or less anteriorly to the foramen of Monro (Fig. 33–5).
Anterior Third Ventricular Access The patient should be placed supine with the head neutral to the midline and in slight extension (5 to 15 degrees). A bur hole is placed at or slightly behind the coronal suture and 3 cm lateral to the midline. Perpendicular access to the ventricle will place the scope slightly behind the foramen of Monro (Fig. 33–6). The choroid plexus, the thalamostriate vein, and the septal vein should be easily and clearly visualized. The scope is advanced through the foramen of Monro, being careful to avoid injury to the veins or the columns of the fornix. Once in the third ventricle, the mammillary bodies, tuber cinereum, and infundibular and suprachiasmatic recesses will be identified and seen (Fig. 33–7). A 30 degree angled scope will permit the visualization of the lamina terminalis, anterior commissure, and anterior third ventricular
B cyst wall can be seen inside the third ventricle. The top of the cyst can be seen attached to the undersurface of the anterior commissure. The ipsilateral fornix is seen superiorly (12 o’clock) and contralateral foramen of Monro at 9 o’clock.
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Figure 33–4 Access to a colloid cyst is best obtained by placing the bur hole much more laterally than standard Kocher’s point. Otherwise, attempts at removing the lesion may injure the fornix secondary to too much medial tension. 10.1055/978-1-60406-039-3c033_f004
roof (Fig. 33–8). A third ventriculocisternostomy can now be easily performed, choosing the site of fenestration anterior to the mammillary bodies and posterior to the infundibular recess. Care should be taken to avoid injury to the basilar artery. Lesions, masses, or cysts of the third ventricle can easily be reached with this approach. Exquisite visualization of the suprasellar cistern may be obtained when fenestrating suprachiasmatic cysts (Fig. 33–9).
Posterior Third Ventricular Access
Figure 33–5 Axial diagram shows entrance into the lateral tip of the frontal horn for better access to lesions at the foramen of Monro that extend into the posterior third ventricle. A second bur hole may be used for improved access and instrument manipulation.
The patient is placed supine, head neutral but with moderate extension of the neck (30 to 45 degrees). An incision is made in the forehead, 2 to 3 cm above the eyebrow, at or slightly lateral to the midpupillary line (Fig. 33–10). Care should be taken to avoid the supraorbital nerve. The incision should be placed in one of the forehead creases to conceal postoperative scars. A bur hole is made directly under the incision, and the dura is opened. A ventricular catheter can be inserted into the frontal horn and proper trajectory ascertained. Next, a peel-away introducer or scope cannula is then inserted into the tip of the frontal horn, using the same trajectory. Directly in front, the foramen of Monro and body of the lateral ventricle and occipital horn can be visualized (Fig. 33–11). Entrance into the third ventricle is gained by passing the scope medially through the foramen of Monro. At this point, the posterior third ventricle is now easily visualized. The massa intermedia, posterior commissure, pineal recess, pineal gland region, aqueduct, tela choroidea, and posterior third ventricular wall can also be easily seen (Fig. 33–12). This approach is ideal for rigid scopes. Careful review of sagittal MR images will help in choosing the proper location of the bur hole and the trajectory of the endoscope during these frontal approaches (Figs. 33–13 and
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Figure 33–6 For access to the anterior third ventricle, the access bur hole should be placed behind the coronal suture along the midpupillary line. Placement anterior to the coronal suture will make visualization of the floor difficult and can potentially injure the fornix. 10.1055/978-1-60406-039-3c033_f006
Figure 33–7 Endoscopic view of the floor of the third ventricle demonstrates the paired mamillary bodies and tuber cinereum. The basilar artery bifurcation is seen along with both proximal posterior cerebral arteries between the mammillary bodies. The pons is visualized behind the basilar artery.
Figure 33–8 Endoscopic visualization of the undersurface of the anterior commissure using a 30 degree angled endoscope. The two columns of the fornix are seen extending posteriorly and forming the anterosuperior margins of the foramina of Monro.
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Figure 33–9 After fenestration of a suprachiasmatic cyst, the suprasellar contents are visualized. Notice a stretched infundibulum and the pituitary gland lobes located in the sella turcica. The carotid bifurcation is seen with the first portion of middle cerebral artery (left) and first portion of anterior cerebral artery (right) segments along with an elongated posterior communicating artery and its hypothalamic perforators. 10.1055/978-1-60406-039-3c033_f009
33–14). With this approach there is no injury to the foramen of Monro structures because no torquing is necessary, as is commonly done with a coronal approach. Resection of lesions, biopsies, and fenestrations can now be easily performed. Once the procedure is finished, a single bur hole titanium cover is placed over the bur hole and the galea is closed. A subcutaneous absorbable suture and Steri-Strips are used to close the skin. This approach not only gives excellent cosmetic results but also a superb, direct view to the posterior third ventricle.
Figure 33–10 For lesions of the posterior third ventricle, a direct frontal approach can be made through a forehead crease and slightly lateral to the supraorbital neurovascular bundle. The frontal horn is accessed through its frontal tip. 10.1055/978-1-60406-039-3c033_f010
A
B Figure 33–11 (A) The location and angle of the endoscope can be varied depending on the superior or inferior location of the lesion in the posterior third ventricle. An inappropriate trajectory can make the tar-
get area difficult to visualize. (B) The scope enters the tip of the frontal horn. Medial rotation allows passage into the third ventricle and access to lesions in the posterior wall of the third ventricle.
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A Figure 33–12 (A) Endoscopic view of the posterior third ventricle. A dilated aqueduct of Sylvius with a membrane is seen inferiorly. The posterior commissure is seen immediately superior to the aqueduct. The pineal gland is visible between the posterior commissure and the
B massa intermedia. (B) The roof of the third ventricle composed of the tela choroidea and choroid plexus is seen between the two thalami; the pineal gland and habenular commissure are seen above the massa intermedia.
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Figure 33–13 Preoperative axial T1-weighted magnetic resonance image for an 18-year-old patient with a history of papilledema and severe headaches. Note the large septum pellucidum cyst.
Figure 33–14 Postoperative T1-weighted magnetic resonance image of the same patient following endoscopic laser fenestration using a laterally placed coronal bur hole. Symptoms are fully resolved.
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10.1055/978-1-60406-039-3c033_f015 Figure 33–15 Supine position for access to the frontal horn and anterior third ventricles.
Frontal Horn Access As with approaches to the anterior third ventricle, the patient should be supine with slight neck flexion (Fig. 33–15). The bur hole should be at or 1 cm in front of the coronal suture. However, its lateral location may vary between 3 and 7 cm from the midline or medially located lesions (Fig. 33–16). An extreme lateral placement is of particular importance for lesions of the septum pellucidum (Fig. 33–17) or medial roof of the horn. Cysts, lipomas, or metastatic lesions
can occur in this area. The classic view of the foramen of Monro will be encountered (Fig. 33–18). The first structure to be identified is the choroid plexus, which, when followed, will lead to the foramen. In addition, the thalamostriate and septal veins should be easily identifiable. In cases of longstanding hydrocephalus, the septum pellucidum is not existent and the contralateral ventricle will be visualized with all of its neural structures (Fig. 33–19). Although not all colloid cysts are resectable using endoscopic techniques, many can easily and safely be removed with minimal injury to the patient. The author’s method of choice is the two-portal approach to the right frontal horn. Using the MR image as a guide, two ipsilateral bur holes are placed further laterally than normal to allow direct
Figure 33–16 To gain adequate access to the frontal horn, a standard coronal bur hole is used. By placing it progressively more lateral, medial pathology will be visualized and approached.
Figure 33–17 Diagrammatic fenestration of a lesion located in the medial wall of the frontal horn. A more laterally located bur hole will give better exposure to the inferior aspect of the lesion.
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33 Endoscopic Approaches to the Ventricular System 223 Temporal Horn Access For access to this area, the patient should be placed supine with an ipsilateral shoulder roll and extreme lateral rotation of the head. A 1 cm incision is made slightly above the top of the pinna. Entrance into the temporal horn is gained through a bur hole located over the middle temporal gyrus. The exact location of the bur hole is ascertained with MR images. In the majority of cases, the affected horn will be dilated and the pathology readily visualized (Fig. 33–20). By varying the angle of approach, access can be gained to the roof of the temporal horn, the floor, or the lateral wall (Fig. 33–21). The choroid plexus will be seen coursing along the medial superior aspect of the horn. Figure 33–18 The landmarks of the foramen of Monro and lateral ventricle as seen endoscopically. The fornix makes up the anterior and superior margins of foramen and the thalamus composes the inferior posterior margins. The choroid plexus is located posteriorly and the rostrum of the corpus collusum is seen anteriorly along with the head of the caudate. 10.1055/978-1-60406-039-3c033_f018
medial access to the cyst. One bur hole should be placed directly lateral to the foramen of Monro. Through this opening, an endoscope and its working channels can be inserted. The second bur hole, placed anteriorly, is used to insert a large bore slotted sucker through a no. 14 French peel-away sheath into the anterior horn. The sucker should be placed at high suction. Under direct visualization, the capsule may be opened using an Nd:YAG (neodymium:yttrium-aluminum-garnet) or KTP (potassium-titanyl-phosphate) laser fiber or a radiofrequency probe. As soon as the gelatinous cyst contents are visualized, the large sucker is placed next to the opening and the contents are rapidly aspirated. This maneuver will prevent the cyst contents from entering the ventricular system. The capsule can then be removed using other available endoscopic instruments.
Figure 33–19 The head and body of the caudate are visualized resting on top the thalamus. Above the caudate, the crossing fibers of the corpus collusum can be seen. 10.1055/978-1-60406-039-3c033_f019
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Occipital Horn Access The occipital horn may be approached with the patient positioned prone or lateral (Figs. 33–22 and 33–23). The exact position is the surgeon’s preference, although lateral positioning seems to provide less surgeon fatigue and makes ventricular flushing and irrigation easier. Similarly, there is less chance for debris to settle into the frontal horn and third ventricle with the aid of gravity. A bur hole is located in the classic position for occipital access: 3 cm lateral to the inion and 6 to 7 cm superiorly (Fig. 33–24). Again, the exact location and trajectory should be guided by preoperative MR images. This approach can be superior access to the anterior tip of the temporal horn, the occipital horn, the ventricular atrium, and even the frontal horn (Fig. 33–25). Familiarity with the anatomy in this area is crucial. Struc-
Figure 33–20 The circles demonstrate the locations of lesions easily accessible using an approach over the middle temporal gyrus. The roof of the temporal horn will be identified by choroid plexus running along the fissure. 10.1055/978-1-60406-039-3c033_f020
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Figure 33–22 Prone position for access to the posterior fossa lesions. Figure 33–21 Entrance into the temporal horn is achieved by placing a bur hole slightly superior to the pinna of the ear. The cortical incision is made on the middle temporal gyrus. 10.1055/978-1-60406-039-3c033_f021
tures such as the calcar avis, collateral trigone, and choroid plexus should be easily identifiable. Sometimes the occipital horn is not fully dilated, which makes a direct occipital approach much more difficult and risky. When the rest of the ipsilateral ventricular system is dilated and a small occipital horn is present, it is preferable to approach the lesion from a frontal approach as seen in Fig. 33–16.
Posterior Fossa Access
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heavily padded horseshoe (Fig. 33–22). The neck should be placed in maximal allowable flexion to aid in the exposure of this region. Generally, a paramedian incision is made and a bur hole is placed 2 to 3 cm from the midline (Fig. 33–26). This is particularly important in infants who may have large midline venous sinuses. The appropriate angle is chosen for a particular lesion, and access is easily obtained (Fig. 33–27). When placing a catheter in a trapped fourth ventricle, only a very small bur hole is needed and a 1.2 mm 10K scope can be inserted within the ventricular catheter and pushed forward through a previously made slit at the distal end of a catheter. In this way, difficult to reach and small
Several pathological conditions occur in the posterior fossa that may be accessible with endoscopic techniques. Such lesions include trapped fourth ventricles, arachnoid cysts, cystic tumors, and cerebral pontine angle lesions. For lesions at or near the midline, the patient should be placed in the prone position in either three-point rigid fixation or on a
Figure 33–23 Supine position with 90 degree cranial rotation may be used for entrance into the temporal horn or occipital horns. 10.1055/978-1-60406-039-3c033_f023
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Figure 33–24 To gain access to the posterior compartment of the lateral ventricles, the standard occipital bur hole is used. 10.1055/978-1-60406-039-3c033_f024
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Figure 33–25 The circles demonstrate the locations of lesions that can be reached using an occipital bur hole approach. 10.1055/978-1-60406-039-3c033_f025
midline cysts can be safely and accurately approached with endoscopic techniques. For lesions of the cerebellopontine angle, the patient should be placed in a lateral position with the affected side up. A spinal drain can be inserted into the lumbar cistern, and when sufficient spinal fluid is removed, the cerebellar hemisphere is allowed to fall away from the
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lateral aspect of the skull, thereby exposing the cerebellopontine angle in the superb fashion. In these cases, the incision is made more lateral and the bur hole is placed immediately medial to the mastoid tip. Closure of the dura should be done with a piece of pericranial flap, and if the mastoid air cells are entered, generous amounts of bone should be used to prevent postoperative CSF leaks.
Postoperative Management Including Possible Complications
Figure 33–27 Endoscopic localization and biopsy/removal of difficult to reach midline infratentorial lesions can be safely and easily done with paramedian bur hole placement.
Although relatively infrequent, complications can and do occur while approaching the ventricular system with endoscopic methods. Given the steep learning curve associated with these procedures, mishaps are more likely to occur early during training. Bleeding is probably the most common and bothersome complication. Even small amounts of blood within the CSF can rapidly obscure visualization within a few seconds. The risk of bleeding can be decreased by using the laser, which will obliterate small bleeders. By holding the laser fiber several millimeters away from the vessels, it will diffuse the energy and fully obliterate it. Most bleeding will be venous in nature, and time and irrigation will lead to clot formation and bleeding cessation. Even if the entire ventricular system is casted with clotted blood, the clot can then be safely removed with some diligence. Grasping forceps or suction can be used to accomplish clot evacuation. Arterial bleeding on the other hand, if uncontrollable, may require an open craniotomy. Fortunately, this is not a common occurrence.
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226 Pediatric Neurosurgery Acute increase of intracranial pressure can occur if the outflow of irrigant is not carefully matched with the inflow. This is particularly true when working inside the third ventricle. Sudden changes in vital signs should alert the surgeon to this possibility. Conversely, if too much fluid is removed from the ventricles, especially in a patient with thin cortical mantle, bilateral subdural hematomas can develop. Theoretically, the infection rate increases with the increased number of instruments used and with manipulation. However, this appears not to be the case because the infection rate in the surgical procedures is ~0.8%. Seizures can be problematic in some patients. However, prophylaxis has not been done routinely even for two portal procedures. Due to the large size of the dural opening, large subgaleal fluid collections can occasionally be found if dural closure is not properly done. A small piece of pericranium can be used to close the dura and prevent these complications. Endocrine disturbances have been described in third ventriculostomies by some authors who perform the opening of the floor of the ventricle with the tip of the endoscope. Perhaps this is due to mechanical injury to the hypothalamus. We have not seen any endocrine or hypothalamic dysfunction
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following third ventriculostomies. A dangerous complication that has been seen with increased frequency is injury to the tip of the basilar artery. Besides the acute intraoperative hemorrhage, a pseudoaneurysm commonly forms that must be immediately and adequately diagnosed and treated with endovascular techniques.
Conclusion Neuroendoscopic techniques provide the neurosurgeon with an increased array of techniques and alternatives for treating simple or complex intraventricular lesions or for restoring adequate CSF flow dynamics. The minimally invasive nature of these procedures leads to less neural tissue destruction/injury, less patient discomfort, decreased length of stays, and, ultimately, to decreased hospitalization costs. However, to achieve excellence results, adequate training, careful planning and execution, as well as proper patient selection are not only necessary but mandatory.
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34 Intraventricular Endoscopy Jonathan P. Miller and Alan R. Cohen
“Minimally invasive neurosurgery” sounds like an oxymoron because neurosurgical procedures are, by their very nature, highly invasive. However, located deep within the substance of the brain and filled with clear fluid, the cerebral ventricles are ideally suited for endoscopic navigation. Recent improvements in optics and miniaturization now make it possible to perform certain intracranial procedures through small exposures with minimal trauma to neural structures. Endoscopic techniques have been used to facilitate insertion of ventricular shunt catheters, to fenestrate loculated ventricular cysts, and to inspect, biopsy, and sometimes remove certain intraventricular cysts and tumors. In some cases of noncommunicating hydrocephalus, endoscopic fenestration of the floor of the third ventricle can eliminate the need for ventricular shunting altogether. The endoscope can also be introduced through small cranial exposures at the skull base to allow visualization of structures otherwise hidden from the operative microscope. In this chapter, the history of neuroendoscopy is briefly reviewed, followed by a discussion of the neurosurgical applications of endoscopy focusing on operations performed within the cerebral ventricles.
History of Neuroendoscopy The application of endoscopic techniques to neurosurgical conditions began with an effort to diagnose and treat hydrocephalus at the turn of the 20th century. The first recorded endoscopic neurosurgical procedure took place in 1910 when Victor Darwin Lespinasse (1878–1946), a urologist in Chicago, used a cystoscope to fulgurate the choroid plexus in two hydrocephalic infants. Eight years later, Walter Edward Dandy (1886–1946) used the instrument for the same purpose, and in 1922 was the first to use the term “ventriculoscope.” Both Lespinasse and Dandy reported discouraging results, and ventriculoscopy was all but abandoned at that time because of high surgical morbidity rates and the development of better indirect means of imaging intracranial contents. Ultimately, valved shunts were developed to effectively treat hydrocephalus, and ventricular endoscopy almost became a historical curiosity. As experience with ventricular shunts increased, however, it became apparent that ventricular shunts were not as safe and effective as initially thought. Ventricular shunts remain fraught with problems related to malfunction and infection, and shunt surgery is today associated with a higher rate of
complications than any other commonly performed neurosurgical procedure. The current resurrection of interest in neuroendoscopy was fueled initially by efforts to simplify or eliminate ventricular shunt systems. Recent technical breakthroughs in optical design have made it possible to approach even deep-seated ventricular tumors via the endoscope. A variety of neurosurgical endoscopic procedures have been developed, such as endoscopic third ventriculostomy, cyst fenestration, retrieval of adherent ventricular catheters, and biopsy or removal of ventricular tumors.
Instrumentation Several of the innovative contributions to the field of neuroendoscopy were pioneered by Harold H. Hopkins, a British physicist working at the University of Reading. In 1960, he improved on the conventional endoscope system initially developed in Vienna by Nitze in 1887. Instead of a train of biconvex lenses spaced out in an air-containing metal tube, which is optically inefficient, Hopkins used a solid rod lens system that results in a significantly smaller diameter instrument with a wider viewing angle, improved light transmission, improved image resolution, and reduced chromatic aberration. Hopkins also developed the coherent fiber-optic bundle system that serves as the basis for the flexible endoscope by wrapping a small quartz fiber many times around a drum and then making a single cut across all the fibers, thereby leaving them identical in length and location at each end. By ensuring that each fiber at one end was identical in position to its cut counterpart at the other end, Hopkins was able to create a coherent fiber-optic bundle that could transmit not only light but a clear image as well. Intracranial endoscopy can be performed using either rigid or flexible endoscope. The rigid system (Fig. 34–1) provides superior optics and superior working channel capabilities, whereas the flexible system (Fig. 34–2), which can be steered, provides better maneuverability. Because of its superior optics and working channels, the rigid endoscope is currently used more often for ventricular endoscopy. Rigid endoscopes are available in several angles based on the direction the camera is facing relative to the tip of the endoscope. A 0 degree straight telescope is best for viewing because it provides an image directly in front of the instrument, whereas a 30 degree forward-oblique endoscope is better for operating because it provides the operator better
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Figure 34–1 Rigid ventricular endoscope. The instrument has multiple working channels. Illumination is provided by a fiber-optic cable connected to a xenon light source, and the image is projected via a microchip camera to a television screen. 10.1055/978-1-60406-039-3c034_f001
Figure 34–2 Flexible ventricular endoscope, now seldom used for ventricular endoscopy because of its inferior optics and working channels. There is a flexible fiber-optic imaging catheter that can be steered via a thumb control. The base of the endoscope can be supported by a Greenberg retractor. 10.1055/978-1-60406-039-3c034_f002
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34 Intraventricular Endoscopy 229 visualization of instruments as they emerge from the adjacent working channels. When using the working channels with the 0 degree telescope, instruments must be advanced fairly far until they can be seen, which carries a risk of damage to important neurovascular structures. The operative field can be viewed by looking directly through the endoscope, but more often it is projected via a microchip camera to a television screen, enabling the operator and operating team to view the procedure while maintaining sterility. Illumination is provided by a fiber-optic cable connected to a xenon light source. The endoscope system can either be handheld or supported by a retractor system such as a Greenberg retractor, which uses a rack-and-pinion handle for controlled adjustments. Other endoscopes are available for use in conjunction with stereotactic equipment. Whether a rigid or a flexible endoscope is chosen for working within the cerebral ventricles, it is important to provide adequate irrigation. Because the diameter of the instrument is quite small, only a small area of the ventricle can be seen at any given time, and even minor venous bleeding can obscure the endoscopic view. Constant irrigation serves to keep the endoscopic window clean. To accomplish this, a slow infusion of lactated Ringer's solution from a pressurized bag is connected in a closed system to one of the working channels in the endoscope, and the fluid can be vented from another working channel. It is imperative that all fluid infused be allowed to escape; otherwise, progressive ventricular distension could result, leading to a dangerous elevation of intracranial pressure. An assortment of microinstruments can be introduced through small working channels in the endoscope, including bipolar coagulators, scissors, grasping forceps (Fig. 34–3), biopsy forceps, and suction and irrigation catheters. Endoscopic dissection can be performed by passing a small fiberoptic laser system through one of the working channels. The neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser, which emits a near-infrared beam with a wavelength of 1064 nm, is well suited for endoscopic use within the cerebral ventricles. The invisible laser beam, aimed using a visible (red) helium-neon pilot beam, is transmissible
Figure 34–3 Endoscopic grasping forceps.
through fluid and is absorbed preferentially by pigmented tissues, making it very effective for cutting and coagulating. However, poorly pigmented tissue, such as the septum pellucidum, requires higher power settings for fenestration. The carbon dioxide (CO2) laser has a wavelength 10 times longer than the Nd:YAG; although it is more effective for vaporizing tissue, it is not as useful for ventricular endoscopy because it does not transmit readily through fluid. Another laser, the potassium-titanyl-phosphate (KTP), emits green light in the visible spectrum with a wavelength of 532 nm. It is a useful dissecting tool and produces less thermal injury than the Nd:YAG laser.
Preoperative Preparation Endoscopic ventricular surgery is usually performed with the patient under general anesthesia, but local anesthesia can be used for cooperative adult patients or those whose medical condition precludes general anesthesia. A dose of antibiotics is administered intravenously prior to incision and continued every 6 hours for 1 day. Anticonvulsants are not generally used. A sterile craniotomy tray should be available in the event of an emergency, but it is very unlikely that it would need to be used.
Operative Procedure The patient is positioned supine with the brow up and the head elevated 20 to 30 degrees, supported by a “doughnut” cushion. A small amount of hair is shaved and the right frontal scalp is cleansed with povidone-iodine soap and solution, walled off with towels, and covered with an iodoform-soaked adhesive drape. If it is anticipated that the patient will require insertion of a ventricular shunt or drain, the preparation and draping are modified appropriately. The operation is performed through a right coronal bur hole unless the location of the pathological process dictates otherwise. The scalp is infiltrated with a solution of 0.25% lidocaine containing a 1:400,000 dilution of epinephrine. A small curvilinear incision is made in the right frontal scalp in the midpupillary line just anterior to the coronal suture, and a bur hole is placed at this site. The dura is incised with a no. 11 blade, and the arachnoid and pia are coagulated with a bipolar cautery and are incised. The endoscope is then inserted into the frontal horn of the right lateral ventricle. Most rigid endoscopes have their own introducer sheath and obturator for this purpose. Once the ventricle has been cannulated, normal anatomical structures are identified. The choroid plexus and the union of the septal and thalamostriate veins guide the operator to the foramen of Monro, which provides a constant anatomical landmark. When working within the third ventricle the operator becomes oriented by identifying several landmarks along the third ventricular floor, including the aqueduct of Sylvius posteriorly and the mammillary bodies and infundibular and optic recesses anteriorly. From a coronal approach the anterior third ventricle is usually seen clearly. A large massa intermedia may obstruct visualization of the posterior third ventricle.
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230 Pediatric Neurosurgery Third Ventriculostomy Some cases of noncommunicating hydrocephalus are associated with a functional cerebrospinal fluid (CSF)-reabsorption mechanism that is rendered ineffective due to a proximal block to CSF flow, most commonly at the cerebral aqueduct. If a new path for CSF flow can be created, normal re-absorption can be reestablished, thereby eliminating the need for a ventricular shunt. This is the philosophy behind endoscopic third ventriculostomy: A fenestration is produced in the floor of the third ventricle, allowing CSF proximal to the site of obstruction to escape into the basal cisterns. For third ventriculostomy to be successful, two conditions must be met. First, there has to be a significant obstruction to the flow of CSF between the ventricles and the subarachnoid space. Second, there must be preservation of communication between the subarachnoid space and venous system so that CSF absorption can proceed once the obstruction is bypassed. It is relatively easy to establish the first condition using modern imaging techniques, but the second is more problematic, as some patients (especially infants) may have a component of communicating hydrocephalus as well. Patients with aquired aqueductal stenosis are most likely to have a functioning communication between the subarachnoid space and the venous system, so they tend to be the best candidates for endoscopic third ventriculostomy. All patients undergoing endoscopic third ventriculostomy should undergo magnetic resonance imaging (MRI) scanning pre- and postoperatively. MRI provides a clear demonstration of the aqueductal anatomy as well as the location of the basilar artery. Gadolinium can be administered to exclude an enhancing neoplasm. Two-dimensional phase contrast cine MRI, a noninvasive technique gated to the cardiac cycle, is useful for looking at CSF flow; this study helps to confirm the diagnosis of aqueductal stenosis preoperatively and document patency of the third ventriculostomy postoperatively. When there is diagnostic uncertainty, iohexol ventriculography with computed tomography (CT) can be performed. To perform an endoscopic third ventriculostomy, the endoscope is introduced into the right lateral ventricle and the foramen of Monro is identified. The endoscope is guided through the foramen of Monro into the third ventricle, and the third ventricular floor is inspected (Fig. 34–4). The basilar artery apex can usually be identified through the translucent floor where it terminates just beneath the mammillary bodies. A site for fenestration is chosen in the attenuated tuber cinereum in the midline just anterior to the mammillary bodies, but behind the infundibular and optic recesses. A small hole is created at the fenestration site and enlarged by means of a Fogarty balloon catheter. The fenestration should be ~5 mm in diameter. Confirmation of a satisfactory fenestration is made by direct endoscopic visualization of the basilar artery in the interpeduncular cistern. The edges of the fenestration will be seen flapping up and down as CSF moves between the third ventricle and the basal cisterns. The edges of the fenestration may be coagulated further to widen the hole.
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Figure 34–4 Endoscopic third ventriculostomy. A rigid endoscope has been inserted through the foramen of Monro into the third ventricle. The floor of the third ventricle is fenestrated anterior to the mamillary bodies and behind the infundibular and optic recesses. The basilar artery will be just posterior to the fenestration. 10.1055/978-1-60406-039-3c034_f004
Treatment of Complex Hydrocephalus Endoscopic fenestration techniques can be used to simplify the management of hydrocephalus associated with loculated collections of CSF, including suprasellar arachnoid cysts, parenchymal or intraventricular cysts associated with germinal matrix hemorrhage or infection, trapped lateral ventricles due to obstruction at the foramen of Monro, and some cases of trapped third and fourth ventricles. Preoperative radiographic workup for these conditions should include MRI. Patients with suprasellar arachnoid cysts who present with hydrocephalus, visual loss, or endocrine dysfunction can be treated by ventriculocystostomy. The endoscope is inserted into the right lateral ventricle and the right foramen of Monro is identified. The arachnoid cyst will then be seen filling the foramen; its wall usually has a bluish tinge. The cyst wall, which can be quite thick, is dissected with the Nd: YAG laser. Grasping forceps are used to remove as much of the wall as possible because smaller fenestrations may scar over and close. After the cyst has been opened, the endoscope can be passed through the foramen of Monro to reveal
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34 Intraventricular Endoscopy 231 a spectacular view of the basal cisterns, including the entire length of the basilar artery, the brain stem and the cranial nerves, and the pituitary gland and stalk. Some surgeons manage this condition with cyst fenestration alone, but if it is determined that a ventricular shunt is required, it can be placed at the same sitting. Loculated ventricular cysts are dealt with in the same fashion. Rather than use multiple proximal shunt catheters to decompress loculated cavities, windows in the cyst walls can be created with an endoscope and laser. Using this technique, complex shunt systems can be simplified and a single shunt used to drain multiple compartments. As with most surgical procedures, it is best to identify normal anatomy first and work toward abnormal anatomy. Therefore, whenever possible the ventricle is initially approached with the endoscope, and the fenestration made toward the cyst. If the cyst is entered first, the normal ventricular anatomy may not be visualized through the cyst walls. Sometimes there are so many intraventricular septa that no recognizable anatomy can be seen. When this occurs in infants, intraoperative transfontanelle ultrasonography can be helpful in orienting the operator. The ventricular endoscope can also be used to unblock a trapped ventricle. If there is unilateral enlargement of a lateral ventricle due to an obstruction at the foramen of Monro, the endoscope and laser can be used to create a fenestration in the septum pellucidum. The septostomy should be positioned strategically to avoid injury to the fornices or corpus callosum. In some cases the endoscope can be used to open a third or fourth ventricle that has become isolated by adhesions.
Removal of Adherent Catheters Often, proximal shunt malfunctions develop because the ventricular catheter has become occluded by a choroid plexus. Sometimes these catheters become stuck in the choroid plexus, and dislodging them can lead to ventricular hemorrhage. Most adherent ventricular catheters can be removed by passing a stylet through the catheter and coagulating it briefly with monopolar current. If this is unsuccessful, the catheter can be dissected free under direct vision using the ventriculoscope. The scope is passed into the lateral ventricle through a second bur hole, and the shunt catheter is identified. The adherent choroid plexus is coagulated gently using either bipolar forceps or a laser fiber, and the freed catheter can then be pulled out. If a fragment of catheter has broken off within the ventricle, it can be snared with a grasping forceps. The shunt catheter is too large to be withdrawn through the endoscope’s working channel, so the endoscope, forceps, and shunt catheter are removed as a single unit. A new ventricular catheter can be inserted through the endoscope track. When necessary, a wandering distal catheter can be retrieved from the peritoneum using a similar technique. This procedure is easier than removing a ventricular catheter because the peritoneal cavity can be filled with carbon dioxide, and the shunt removed using standard laparoscopic techniques. It should be stressed, however, that not all adherent catheters need to be removed.
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Biopsy and Treatment of Ventricular Tumors Ventricular tumors can be biopsied endoscopically under direct vision and cystic tumors can be drained. When necessary, the septum pellucidum can be fenestrated at the same sitting, and a ventricular shunt inserted. Some ventricular tumors can be vaporized and removed totally through an endoscope. Ventriculoscopic surgery is particularly well suited for dealing with colloid cysts of the third ventricle. These benign lesions can produce symptomatic obstruction at the foramina of Monro. Standard surgical treatment has consisted of craniotomy and either transcallosal or transcortical-transventricular removal of the mass. Stereotactic cyst aspiration has been proposed and used effectively as a less invasive alternative to craniotomy. Problems associated with stereotactic cyst aspiration include (1) difficulty penetrating the thick cyst wall; (2) difficulty aspirating the viscous colloid material; and (3) the possibility of neural or vascular injury due to an inability to visualize the operation. Endoscopic techniques eliminate these problems and still allow the operator to deal effectively with colloid cysts without a large craniotomy. A bur hole is placed in the midpupillary line near the coronal suture, and the lateral ventricle is cannulated with a rigid endoscope (Fig. 34–5). Because of the necessary trajectory, the bur hole will be somewhat more anterior than the bur hole used for for endoscopic third ventriculostomy. The cyst wall is then opened widely using the Nd:YAG laser fiber, and the thick cyst contents are emptied under direct vision using a large catheter passed through one of the working channels. After the cyst has been emptied, the remaining capsule is coagulated and either vaporized or removed as
Figure 34–5 Endoscopic removal of colloid cyst. Note the bur hole is somewhat more anterior than for endoscopic third ventriculostomy (Fig. 34–4). The cyst wall is opened widely, and cyst contents are emptied under direct vision. 10.1055/978-1-60406-039-3c034_f005
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232 Pediatric Neurosurgery much as possible with grasping forceps. A septostomy can be created at the same sitting. The ventricle is irrigated copiously with lactated Ringer’s solution, the endoscope is removed, and a ventricular drain is inserted and continued for 48 hours postoperatively. Dexamethasone is administered perioperatively to minimize the risk of aseptic meningitis.
Postoperative Management Including Possible Complications Although endoscopic ventricular surgery allows for performance of highly complex cases with minimal surgical trauma when properly performed, its potential complications are just as serious as those associated with open exposures, if not more so because of the limited size of the operative corridor. The most serious risk of therapeutic neuroendoscopy is hemorrhage because even minor amounts of blood can obscure the surgeon’s view, and significant bleeding mandates that the procedure be aborted. Most venous bleeding, although troublesome, is usually self-limited and clears with irrigation. Sometimes the bleeding source can be identified through the endoscope and coagulated. Significant arterial bleeding cannot usually be controlled through the endoscope and may require an emergent craniotomy if it does not abate with ventricular irrigation and drainage. Endoscopic third ventriculostomy carries an inherent risk of injury to the basilar artery because it is situated adjacent to the site of ventricular fenestration. Therefore, endoscopic third ventriculostomy should not be performed unless the third ventricle is enlarged and the third ventricular floor is translucent. The size of the third ventricle and the position of the basilar artery should be checked on a preoperative MRI scan. Highly vascular lesions may produce too much hemorrhage to allow for continued visualization of the operative site, and may therefore be handled more safely via an open procedure.
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There are several unique challenges associated with colloid cysts. If a colloid cyst is simply drained without elimination of the cyst wall, it is likely to recur. After the colloid cyst is evacuated, the ventricles must be irrigated copiously to prevent chemical ventriculitis from exposure to the highly irritating colloid material. Any time a surgeon works near the foramina of Monro, great care must be taken to avoid injury to the fornices, which can have devastating neurological effects. Finally, it is important that the surgeon does not become disoriented during the case. Unique hand-eye coordination skills are required to carry out an operation while watching a television screen. The endoscopic picture, however clear, reveals only a small portion of the ventricular anatomy at any one time. Depth perception is lost and the operator must use three-dimensional anatomical knowledge to navigate. Furthermore, the region of interest is often eccentric or nonorthogonal when viewed through an angled lens scope or a steerable fiber scope. Hands-on experience with either cadaver dissections or practical courses and workshops is extremely helpful to learn effective use of the endoscope.
Conclusion As the field of neuroendoscopy continues to grow, new indications for its use are always being defined. At present, endoscopic ventricular surgery has a central role in the management of certain cases of hydrocephalus and ventricular neoplasms. Shunt systems can be simplified in some cases and eliminated in others. Ventricular neoplasms can be biopsied or dissected under direct vision using the endoscope. Continued improvements in endoscopic surgical technique and instrumentation should expand its usefulness and result in better outcomes for patients who suffer from these conditions.
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35 Infected Ventriculoperitoneal Shunts Keyne K. Thomas, Sohaib A. Kureshi, and Timothy M. George
Patient Selection Management of ventriculoperitoneal (VP) shunt infections continues to be an ongoing dilemma. Despite improved technique and advancement in antibiotic therapy, the reported incidence of shunt infections ranges from 2% to as high as 22%, making it the second leading cause of shunt complication after mechanical obstruction. Complications of shunt infections are both costly and devastating, with a mortality rate of 1.5 to 22%. Seizures, cognitive decline, and focal neurological deficits are some of the morbid consequences. Shunt infections are more likely to occur within the first 4 weeks postoperatively; however, it has been shown that 90% occur within the first 6 months. Various factors, such as prematurity, patient’s age, number of revisions, previous shunt infection, and associated myelomeningocele, have been shown to correlate with an increased incidence of infection. Shunt insertion in the premature infant has been shown to have a fivefold increase in the risk of infection. DiRocco et al showed an 80% infection rate in patients <6 months of age. Likewise, Pople et al showed a 15.7% incidence of infection in patients <6 months in comparison with a 5.6% infection rate in patients >6 months. After the first two shunting procedures, successive revisions can carry higher infection risk, from 10% after the second revision to 20% after the fourth revision. A fourfold increase in the risk of shunt infection was reported by McGirt et al in patients who had a previous shunt infection. Finally, some authors have also reported that the myelomeningocele population has a higher incidence of infection, ranging from 11.3 to 18%. Although these factors may be independent of the surgeon, others within the surgeon’s control have been shown to increase the risk of VP shunt infection. The key factor in the management of shunt infections is prevention. Use of prophylactic antibiotics showed a 4% decline in the rate of VP shunt infections. Choux et al showed a reduction in shunt infection from 7.75 to 0.17% with the use of aseptic technique. In addition, double gloving when compared with single gloving has a lower infection rate. Laine et al demonstrated an incidence of glove perforations of 18.3% when single gloving versus inner glove perforation of 6.82% when double gloving. Decreasing the length of surgery is also a key factor in the prevention of shunt infections. Kontny et al reported an infection rate of 13.6% for
surgeries >90 minutes and only 5.2% for those <90 minutes. One group was able to show a 0% infection rate for surgeries <46 minutes. Finally, more experienced surgeons have fewer infections. Cochrane et al found that surgeons with >147 shunt procedures had an infection rate of 7% in comparison with those surgeons with <147 shunt procedures, who had an infection rate of 9.4%. Infection of VP shunts has various presentations that range from colonization of the shunt tubing, ventriculitis, peritonitis and/or infected pseudocyst to isolated wound infections. This chapter will discuss the prevention, surgical management, and treatment of VP shunt infections.
Preoperative Preparation Operative Prevention of Ventriculoperitoneal Shunt Infections One hour prior to the skin incision, the patient should be given an antibiotic aimed principally to cover staphylococcal species, which happens to be the most common pathogen seen in VP shunt infections. This initial step has resulted in a three- to fivefold reduction in infection. We routinely use nafcillin unless the patient has a penicillin allergy, in which case we use vancomycin. We prefer a limited hair clipping to keep the hair out of the surgical field, as opposed to a substantial hair shave. A diligent skin preparation with Betadine (povidone-iodine) or Hibiclens (chlorhexidine topical) solution should be performed. After being allowed to dry, the surgical area should then be covered with iodine-impregnated sterile adhesive drapes. Appropriate incisions are then made, keeping in mind that gentle handling of tissues and meticulous hemostasis are critical when attempting to prevent infection. Following complete skin preparation and draping, shunt components should then be removed from the sterile packaging and kept in a bacitracin solution until used. While installing the shunt components, contact of the shunt tubing with the skin should be avoided, and tubing exposed to the surgical drapes should be wrapped in bacitracin-soaked sponges. Glove contact with skin and shunt components should also be minimized. Copious irrigation with antibiotic solution and a meticulous two-layered closure with precise approximation of skin edges are crucial
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234 Pediatric Neurosurgery for proper wound healing. Finally, operating room traffic should be kept to essential personnel only and surgical time should be kept to a minimum. In spite of strict adherence to these guidelines, the goal of a 0% infection rate is difficult to attain.
Diagnosis of Shunt Infection Patients with infections of a VP shunt typically present with a fever and/or with evidence of shunt malfunction. A multisystem fever evaluation should always be performed to rule out concurrent infections. This is especially true when it has been >1 year since the last shunt operation. Typically, the fever is <39°C, except that infants can have fever as high as 42°C. Headaches are nonspecific, given that headache is a common symptom in any illnesses that cause fever in shunted patients. Abdominal pain or tenderness suggests the presence of a pseudocyst. Local wound site inflammation along the shunt tract suggest that there may be a localized cellulitis or infected shunt tract. Diarrhea should automatically raise a red flag that this is likely not a shunt infection, given that this symptom is typically not associated with infection. The radiological workup includes a computed tomography (CT) scan. The CT will allow for quick evaluation of ventricular catheter location, ventricular size, and ventricular contents, such as loculations or even proteinaceous debris in the case of severe gram-negative ventriculitis. Lack of ventricular enlargement does not rule out infection. A shunt series can reveal many important findings. First, the continuity of the shunt tubing can be assessed and the location of the shunt reservoir found for tapping. Second, sources of shunt-related problems can be seen, such as subcutaneous air, a large abdominal cyst, or ileus bowel gas pattern. Third, other sources of infection such as pneumonia can be uncovered. Last, old retained shunt components can be identified for removal at surgery. An abdominal ultrasound is useful to evaluate for a pseudocyst, particularly in the patient who presents with only abdominal symptoms. Even though <1% of all shunted patients develop pseudocysts, this study is of particularly high yield when the patient is >9 months postoperative, because up to 62% of patients with infections >9 months postsurgery had associated abdominal pseudocysts. Furthermore, contrast-enhanced abdominal CT may be required for evaluation of an intra-abdominal collection and may be needed when ultrasound is unable to provide adequate visualization or identify other pathology.
The Shunt Tap When infection is suspected, a shunt tap should be performed to sample cerebrospinal fluid (CSF) and to test shunt function. This is done under sterile conditions to avoid contamination of the shunt by the patient’s own skin flora. A mask and sterile gloves should be worn and the area over the shunt reservoir shaved, prepped with Betadine or Hibiclens solution, and then draped with sterile adhesive paper drapes. A 23 gauge butterfly needle is passed percutaneously into the reservoir (Fig. 35–1). Testing shunt flow dy-
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Figure 35–1 The shunt tap. A 23 gauge butterfly needle is passed into the shunt reservoir. The intracranial pressure is measured using a manometer and cerebrospinal fluid samples are collected. 10.1055/978-1-60406-039-3c035_f001
namics will vary depending on the shunt system. The testing sequence begins with occlusion of the distal flow, which allows for measurement of the CSF flow from the ventricular catheter and of intracranial pressure, along with sampling of CSF. Next, the proximal flow should be occluded and distal valve function and peritoneal tubing patency tested using a fluid column. The obtunded febrile patient should also undergo a shunt tap to both relieve pressure and send CSF while preparing for emergency shunt removal and external ventricular drain placement. The diagnostic standard for infection is the isolation of bacteria in the CSF obtained from the shunt tap. CSF revealing a positive gram stain and/or recovery of organisms on aerobic or anaerobic cultures may demonstrate organisms and an inflammatory cellular reaction. This allows for preliminary identification of the offending organism and can direct further therapy. Fever, combined with leukocytosis, neutrophils >10%, low glucose level, and high protein, confirms shunt infection. A caveat when interpreting CSF profiles is that these parameters can display considerable variability and should be interpreted in the context of the clinical situation. In situations in which a distal shunt infec-
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35 tion is suspected (i.e., a cyst found on ultrasound), a shunt tap should still be performed and CSF obtained to determine if there is concurrent ventriculitis.
Pathogens The most common pathogens causing VP shunt infections are Staphylococcus aureus and coagulase-negative staphylococcus with percentages varying from 62 to 90%. Less common pathogens include gram-negative bacilli occurring in 6 to 20% of cases. Proteus, pseudomonas, and streptococcus occur a little less frequently, with a prevalence of 8 to 10%. Less common pathogens include H-flu, gram-negative rods, enteroccocus, and Candida, occurring in >5% of VP shunt infections. A common bacterial isolate, but when seen promotes some confusion with regards to treatment options, is Propionibacterium acnes. This anaerobic gram-positive rod is also commonly found in the skin, and in the majority of cases it represents a contamination. Broth-only isolates of propionibacterium rarely represent a true infection, but infection must be considered when cultured on media plates; it may take up to 9 days to grow. For culture-positive propionibacterium, we first repeat the CSF culture. The patient is sent home after 3 days if the culture shows no growth, but growth of the propionibacterium is followed for 14 days. If the culture turns positive, we call the patient immediately and schedule for shunt removal, external ventricular drain (EVD) placement, and appropriate antibiotic treatment.
Choice of Antibiotics/Length of Treatment Given that the staphylococcus species is the most common organism, if shunt infection is suspected, empiric treatment should include vancomycin and a third-generation cephalosporin. The final choice of antimicrobial therapy, however, should be directed against the isolated organism. Both the antibiotic sensitivity and the ability for the antibiotic
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to penetrate into the central nervous system are important considerations in choosing the correct drug. For optimal management of shunt infections, the concentration of administered antibiotics in CSF should be measured to ensure adequate penetration. Monitoring of serum and CSF antibiotic levels can be useful in guiding therapy. We do not routinely use intraventricular antibiotic therapy unless the infection is complicated by an extremely virulent organism, CSF loculations, frank intraventricular purulence, or CSF sterility has not been achieved after 2 weeks of therapy. Special attention should be made when gram-negative organisms are encountered. A very aggressive approach should be used that includes intravenous and intraventricular gentamicin or amikacin at times in conjunction with a continuous irrigation of the ventricular system. There has been no class I evidence for duration of treatment. For staphylococcal species the length varies from 5– 21 days to 5–24 days for gram-negative rod infections. Our length of treatment is at least 10 days for routine ventriculitis infected by staphylococcal species. Table 35–1 shows our treatment protocol for the most frequently encountered organisms, suggested treatment, and length of treatment. Again, it is important to remember that antibiotic therapy should ultimately be based on sensitivity results. The most effective length of treatment continues to be until CSF sterility is achieved. Monitoring of CSF during the treatment is necessary, and it should include at least three sequential CSF samples taken every other day showing no organisms cultured as well as resolution of the inflammatory component of the infection. Abdominal infections, not associated with ventriculitis can be treated for 10 days and monitored by resolution of pain, fever, and a cyst on ultrasound. If infection is limited to the wound and there is no evidence of ventriculitis, then a 7 day course of antibiotic is usually recommended. Complicated infections will require a prolonged individualized treatment program monitored by resolution of infection on imaging studies, CSF profiles, and clinical course.
10.1055/978-1-60406-039-3c035_t001 Table 35–1 Prevalence and Treatment of the Most Common Pathogens Causing Shunt Infections and Suggested Length of Therapy Pathogen
Prevalence
Treament
Length of Therapy
Staphyloccus epidermidis Staphyloccus ureus Gram-negative bacilli (Escherichia coli, Klebsiella) Proteus Pseudomonas Streptoccocus Haemophilus influenzae Gram-negative rods Enteroccocus Gram-positive anaerobes (propionibacterium) Candida albicans
47–64% 12–29% 6–20%
Vancomycin Vancomycin + rifampin empirically if not MRSA nafcillin Cefotaxime ± intraventricular gentamicin
10 days 10 days 10 days
8–10% 8–10% 8–10% 5% >1% >1% >1%
Tobramycin Ceftazidime + aminoglycoside PCN G Ceftriaxone + rifampin Ceftriaxone or cefotaxime Ampicillin + gentamicin Metronidazole, carbapenems, chloramphenicol, ticarcillin
10 days 10 days 10 days 10 days 14 days 10 days 14 days
Rare
Amphotericin B
14–21 days
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Operative Procedure Even though it has been shown that some infections have been managed successfully with antibiotics alone, the preferred strategy is to remove all of the contaminated hardware and treat the CSF with antibiotics. Surgical treatment of shunt infections is guided by three scenarios: (1) catheter contamination with a mild or fulminent ventriculitis; (2) superficial wound infection with or without CSF contamination; and (3) peritoneal infection manifested as a loculated cyst or frank peritonitis with or without CSF infection. Generally, we prefer to treat all infections by the prompt removal of the infected hardware, placement of a temporary EVD, and then delayed replacement of the shunt after
the infection is resolved. Specifically as in scenario I (Fig. 35–2A), the entire shunt hardware should be removed, an EVD placed for the duration of antibiotic therapy, and the shunt replaced. If there is a fulminate ventriculitis (i.e., intraventricular purulence or gram-negative infection), the EVD should be set up so that irrigation of the ventricular system can be performed. This will allow for intraventricular antibiotic therapy and/or continuous irrigation to debride purulent material or help wash out bacteria when CSF production is diminished in the face of gram-negative infection. This has resulted in decreased recovery time in our population. In scenario II (Fig. 35–2B), superficial wound infections should be treated by removal of the shunt hardware and placement of an EVD. If the final CSF cultures are
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Figure 35–2 Surgical strategies for the management of VP shunt infections. (A) Scenario I depicts the typical shunt contamination and associated ventriculitis. The shunt hardware is always removed and either left out or replaced by a temporary external ventricular drain (EVD). After completion of antibiotic course, the shunt is replaced. (B) Scenario II depicts a superficial wound infection. If the cerebrospinal fluid (CSF) shows no bacterial growth, early replacement of the shunt can be performed. If the CSF reveals bacterial growth, ventriculitis has occurred and the EVD should be left in for the duration of the antibiotic course. (C) Scenario III depicts patient with distal infection. If CSF cultures show no growth of bacteria, the shunt can be externalized for the antibiotic course. If the CSF reveals bacterial growth, an EVD is placed for the duration of the antibiotic course. 10.1055/978-1-60406-039-3c035_f002
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negative, the shunt can be replaced in a new location. However, if the CSF cultures are positive, then the usual 10 day antibiotic course is given, and the shunt replaced after the infection is resolved. If there is only a suture abscess, the suture can be removed and the wound treated locally with topical antibiotics. In scenario III (Fig. 35–2C), in the presence of an abdominal infection, the shunt can be removed from the abdomen and left with the distal end externalized when the CSF studies are negative. Once again, if the CSF studies are positive, removal of the entire shunt system and placement of an EVD is necessary.
Placement of External Ventricular Drain The placement of an EVD is performed with the patient under general anesthesia (Fig. 35–3). Induction is accomplished using intravenous thiopental, and anesthesia is maintained using opiates and inhalation agents such as Forane (isoflurane). Close monitoring of body temperature is maintained, and hypothermic measures are instituted to treat pyrexia; warming lights are used if hypothermia is present. The patient is positioned so that the total shunt system as well as a new site for the ventricular catheter is accessible. The key to the procedure is to remove all original hardware that can be safely removed. The site of the previous cranial incision is reopened and the shunt hardware exposed. The ventricular catheter should be disconnected from the distal tubing, and then the valve and peritoneal catheter are removed. When the distal system has been in place for several years, the tubing may become frail and prone to breakage, making necessary the use of one or two small additional incisions to remove the hardware. Next, the original ventricular catheter is removed. When ventricular catheters are adherent and difficult to remove, we use the 1.2 mm ventriculoscope to visualize the lumen of the tubing and cauterize the adherent choroid plexus to avoid intraventricular bleeding (Fig. 35–4). Usually, a soft passing technique can be utilized to place the new 25 cm ventricular drainage catheter when the old tract is used. If a new site is needed, the preferred ventricular catheter placement is via a frontal approach. The entry point on the skull should generally be 2 cm anterior to the coronal suture and 2 cm lateral to the midline. The catheter tip trajectory should be aimed at the ipsilateral medial canthus and anterior to the tragus. Typically, a depth of 4 to 6 cm will place the catheter in the frontal horn, just anterior to the foramen of Monro. CSF samples should be sent for routine studies, including cell count, glucose, protein, gram stain, and culture. The excess tubing is then tunneled subcutaneously at least 4 to 5 cm toward a frontal exit site for ease of nursing care and to avoid having the patient lie on the tubing. A sterile closed drainage system is connected. The wound should be irrigated with copious amounts of bacitracin solution and a meticulous two-layer closure performed with 3–0 or 4–0 Vicryl and 3–0 or 4–0 nylon. Finally, an adherent occlusive dressing is applied. Routinely an EVD should be exchanged at the first signs of infection. This entails a CSF pleocytosis with >11 WBC (white blood cell count)/mm3, which has been reported to be associated with positive CSF cultures. Paramor et al
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Figure 35–3 Placement of the external ventricular drain from a frontal or posterior approach. The tubing is tunneled to a separate exit site and connected to a closed drainage system. 10.1055/978-1-60406-039-3c035_f003
showed a 4.1% overall rate of EVD infection that increased to 10.3% by day 6. Sending CSF every other day is therefore critical to assess for any increase in the WBC. Recently, antibiotic-impregnated EVD catheters have been used with increased frequency. There has been class I evidence to suggest that EVD catheters impregnated with antimicrobials can significantly reduce the risk of catheterrelated infections. In the event that the drain becomes secondarily contaminated, a new EVD should then be placed as described above, preferably at a new site.
Role of Ventriculoscopy in Shunt Infections There are no established criteria by which ventriculoscopy has been shown to be advantageous in the management of infections related to VP shunts. However, we have used the
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238 Pediatric Neurosurgery
A
B
10.1055/978-1-60406-039-3c035_f004
Figure 35–4 The ventriculoscope. (A) The neuronavigational 1.2 mm ventriculoscope is shown with the camera, light source, and irrigation syringe attached. (B) Intraoperative photograph showing the ventriculoscope being used to visualize the lumen of an adherent ventricular catheter. (C) The view though the ventriculoscope revealing choroid plexus infiltrating the drainage ports of the ventricular catheter.
C
endoscope to help in the management of some complex infections. Loculations within the ventricular system as a result of severe ventriculitis can be fenestrated, ventricular catheters that are adherent to the ventricular wall or choroid plexus can be safely removed, focal intraventricular abscesses can be drained and debrided, and catheters that are difficult to place, such as in a child with slit ventricles, are more easily positioned.
Externalization of Distal Shunt Tubing The procedure can be performed in a clean treatment room or preferably in an operating room. Depending on the age of the patient, local anesthesia using 0.5 to 1% lidocaine/ epinephrine mixture with or without a standby sedation protocol is used. The area around the clavicle should be prepped with Betadine or Hibiclens and draped with a sterile adhesive drape. The shunt tubing is palpated as it courses over the clavicle (this is done easily in the vast majority of
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patients), and the skin is then infiltrated with the local anesthetic (Fig. 35–5A). A small 1 to 2 cm transverse incision is made down through the epidermis. The tubing is located again by palpation, and gentle blunt dissection is continued to fully expose the tubing. We prefer to use a Colorado needle monopolar cautery to perform dissection, because the shunt tubing is resistant to damage by the coagulation current. Approximately 3 or 4 cm of the distal portion of tubing is removed and then sectioned once exposed (Fig. 35–5B). Prior to removal of the distal tubing, aspiration of any peritoneal fluid or cyst fluid should be attempted by using a 10 or 20 cc syringe connected to a 16 or 19 gauge blunt needle; the aspirated fluid is sent for culture (Fig. 35–5C). This maneuver allows for a diagnostic sample to be attained while treating a cyst and removing the foreign body. The proximal tubing is connected to a Luer connector, which is then connected to a closed disposable external drainage system in which the level of drainage can be measured and drainage bags changed in a sterile fashion (Fig. 35–5D). Usu-
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B
D
C Figure 35–5 Externalizing a ventriculoperitoneal shunt. (A) Ultrasound of abdomen revealing an infected peritoneal pseudocyst at the distal tip of the peritoneal catheter and the site of externalization below the clavicle. (B) Dissection exposing the shunt tubing. (C) Sectioning of shunt
tubing and aspiration of peritoneal contents using the distal tubing. (D) The proximal shunt tubing is connected to a closed sterile drainage system.
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240 Pediatric Neurosurgery ally, a single-layer closure will suffice using an interrupted nylon suture.
Reinsertion of the Shunt As stated previously, the shunt should be reinserted after three consecutive negative cultures have been confirmed. Typically, with ventriculitis the shunt should be reinserted in a site different from the EVD site. If the infection involved a pseudocyst of peritonitis, the shunt may reinserted into the peritoneal cavity, preferably in a different quadrant. Contraindications include a recurrent cyst, failure of the peritoneum to absorb fluid, and extensive scarring and adhesions. Preliminary data suggest that antibiotic-impregnated shunt catheters may result in a decrease in the incidence of infection and may be of benefit in patients with previous shunt infections. It has been shown that shunt reinsertion is not the only solution. For some of these patients, endoscopic third ventriculostomy remains a successful option. Jones et al demonstrated a 60% shunt independence rate using neuroendoscopic third ventriculostomy in cases of noncommunicating hydrocephalus.
Specialized Instrumentation Ventriculoscope Several brands of ventriculoscopes are available. We use the semirigid 1.2 mm diameter, 15 cm length ventriculoscope (Fig. 35–4A), which allows for viewing the lumen of catheters while still allowing adequate visualization and
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irrigation of the ventricular system. Other ventriculoscope types and sizes include 2 to 5 mm diameter steerable-flexible or rigid ventriculoscopes, which have working channels that allow for the use of cautery wires, laser cables, biopsy forceps, and balloon dilators.
Custom Catheters and Drainage Systems Closed Drainage Systems These systems allow for continuous drainage of CSF that can be controlled via a graduated buret and sterile collection of CSF samples without contaminating the system. Ventricular Catheters The best type of catheter for an EVD is a single lumen ventricular catheter, 25 cm or longer, that has large drainage holes. This will allow for ease of drainage, especially if the CSF is proteinaceous, and the longest subcutaneous tunneling length. Other catheters used are dual lumen ventricular catheters in which there are a drainage port and an irrigation port.
Postoperative Management Including Possible Complications The main complication of the techniques outlined above is the persistence of the infection being treated or superinfection with a different organism. Using an external drain can place the patient at risk for colonization by more virulent nosocomial pathogens, which can result in a more severe infection. However, this risk is low and the use of an EVD is necessary for most patients who are shunt-dependent.
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36 Combined Fronto-Orbital and Occipital Advancement for Total Calvarial Reconstruction Ian F. Pollack
Patient Selection Children with bilateral coronal synostosis often present several challenging management problems that are distinct from those encountered in patients with single-suture synostosis. In many instances, their cosmetic deformities result not only from the effects of coronal synostosis with resultant fronto-orbital retrusion, but also from associated growth restriction of the posterior calvaria and compensatory changes of the surrounding cranial vault, which may be an expression of an underlying craniofacial syndrome. The combination of anterior and posterior calvarial growth restriction produces a markedly foreshortened skull, and because compensatory growth occurs laterally and upward, these children also characteristically exhibit a wide (brachycephalic) and tall (turricephalic) cranial shape. Although such patients have long been treated with fronto-orbital advancement techniques, the cosmetic results are sometimes suboptimal because these procedures deal only with the forehead anomalies without correcting the abnormal calvarial height or the severe occipital flattening. Accordingly, multiple operations may be needed to provide an acceptable cranial morphology and adequate cranial volume. In this context, the development of techniques for total calvarial reconstruction in a single operative procedure represents a major conceptual advance in the treatment of these patients. However, when applying this approach in infants or young children, the surgeon is confronted with opposing problems. On the one hand, sufficient stability must be provided for the reconstruction to avoid postoperative loss of correction and injury to the underlying brain. On the other hand, the construct must have enough potential mobility to permit future calvarial expansion. In an effort to address both of these goals, we developed a modified calvarial expansion procedure, which will be described here, that provides some element of rigidity to the reconstructed forehead and occiput, while at the same time preserves the potential for cranial expansion. It should be emphasized, however, that the management of patients with bilateral coronal synostosis must be individualized. Patients who are candidates for total calvarial reconstruction instead of conventional forehead advancement share several features: (1) severe brachycephaly (Fig. 36–1A) with a horizontal cephalic index (the ratio of the maximum width
to the maximum length of the skull ⫻ 100) or close to 100, far beyond the normal range of 72 to 88 (median ± 2 standard deviations); (2) severe turricephaly (Fig. 36–1B) with a vertical cephalic index (maximum height/maximum length ⫻ 100) that approximates 100, well above the normal range; and (3) evidence of true synostosis of the lambdoid as well as the coronal sutures on three-dimensional computed tomography (CT) reconstructions, with obvious foreshortening of both the anterior and posterior cranial fossae. Children who exhibit little or no brachyturricephaly may be adequately treated by fronto-orbital advancement alone. Conversely, children with synostosis of multiple sutures, particularly those with kleeblattschädel, may require urgent calvarial expansion during the neonatal period, rather than actual advancement, because of their severely abnormal cranial bones. In addition, patients who exhibit radiographic evidence of cervical hypermobility are not suitable candidates for the modified prone position used to perform the procedure outlined here because of the potential for intraoperative injury to the cervical spinal cord or stretching of the vertebral arteries. Such patients are better managed in a staged fashion using alternate positioning techniques. In view of the advantages and disadvantages of the various techniques available for calvarial reconstruction, decisions regarding the management of patients with complex craniosynostosis problems are best made by a multidisciplinary craniofacial team coordinated by both a plastic surgeon and a neurosurgeon. A final consideration concerns the timing of operation. We have generally performed total calvarial reconstruction in previously untreated patients at 6 to 12 months of age rather than during the neonatal period, based on the suppositions that the lengthy procedure is likely to be safer in an older infant with a larger blood volume and that the postoperative risk of either cosmetically or functionally significant recurrent synostosis is lessened. With follow-up periods now exceeding 10 years in the first 12 children that we have treated with this approach, none have required secondary cranial expansion procedures. The rationale for not deferring the operation even further is based on our concern that the calvarial growth restriction in these children might ultimately hamper brain growth and that with the development of progressively worsening brachyturricephaly, the chances of achieving a favorable cosmetic result would be diminished.
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Figure 36–1 (A) Axial computed tomography (CT) scan of a patient with syndromic bilateral coronal and lambdoid synostosis showing severe brachycephaly; the width of the skull is almost identical to the anteroposterior diameter. (B) Lateral surface view of a three-dimensional
CT scan of the head illustrating marked foreshortening of the skull and occipital flattening in association with severe turricephaly; the height of the skull exceeds the maximal anteroposterior diameter.
10.1055/978-1-60406-039-3c036
Preoperative Preparation Evaluation All patients with complex craniosynostosis are examined by a multidisciplinary craniofacial team. A general clinical examination is performed to identify stigmata of an underlying craniofacial syndrome as well as any associated medical problems that may complicate performance of a major craniofacial reconstruction. An ophthalmologic evaluation is also performed to identify papilledema and impairments of ocular motility. In patients with evidence of syndromic bilateral coronal synostosis, a skeletal survey is obtained to define associated bone anomalies. CT scans of the brain, calvarial vault, and cranial base, supplemented by three-dimensional reconstructions, are then performed. Cervical hypermobility, which is a contraindication to the use of the modified prone position for total calvarial reconstruction, is ruled out by performance of dynamic cervical spine radiographs.
Anesthesia Although we follow no rigid guidelines for the actual anesthetic regimen employed, the anesthesiologist’s contribution to the safety of the operation is substantial. Because the patient is placed in a modified prone position using a variety of bolsters (described below), the endotracheal tube must be well secured at the start of the operation; its repo-
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sitioning during the course of the procedure is exceedingly difficult. Use of a reinforced flexible tube to prevent kinking is also advisable. During the operation, several other anesthetic issues gain importance in ensuring patient safety. First, because blood loss often approaches one blood volume, intraoperative monitoring of the patient’s hemodynamic status with a central venous line and an arterial line is essential. An effort is made to keep the blood pressure in the low-normal range to minimize blood loss, although hypotension is avoided. Hematocrit, platelets, and clotting parameters are also measured frequently during the operation to guide replacement. Two units of cross-matched blood, which are often obtained from family members who wish to provide “directed” donation, are immediately available in a refrigerator outside the operating room. Other strategies that we often employ to minimize the need for transfusion include the administration of iron, and in some cases erythropoietin, for at least 4 weeks preoperatively to boost the patient’s preoperative hematocrit, and the use of a cell saver to facilitative intraoperative “autotransfusion.” Second, because of the possibility of air embolism, a precordial Doppler ultrasound probe is placed, end-tidal CO2 is measured, and hypovolemia is avoided during the operation. Third, because of the high potential for hypothermia in small children, which can lead to hemodynamic compromise, core body temperature is measured using a rectal probe; a circumferential heating blanket, maintained around the trunk and lower extremities, is used to facilitate thermoregulation.
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Operative Procedure Positioning The procedure is performed with the child in a modified prone position as illustrated in Fig. 36–2A. This provides simultaneous access to the orbits, forehead, vertex, and pos-
Figure 36–2 (A) Schematic illustration of the modified prone position demonstrating the use of a padded support for the neck and chest and the position of the endotracheal tube. (B) The operative plan is depicted
terior calvaria. Techniques for supporting the head include an inflatable bean bag or a well-padded horseshoe headrest. The bean bag has the advantage of conforming to the anatomy of the patient’s entire anterior chest, neck, and lower face, which minimizes the risk of pressure-induced injury to the skin. Care must be taken to avoid overextending the neck, which can risk spinal cord injury in these young patients.
on the skull, indicating the three major components of the reconstructive procedure: fronto-orbital advancement, occipital advancement, and height reduction.
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244 Pediatric Neurosurgery Because the goal of the operation is to provide one-stage correction of the entire calvaria (Fig. 36–2B), there are no simple alternatives to the positioning strategy outlined. Some surgeons prefer to reconstruct the anterior and posterior calvaria at separate operations, using more conventional supine and prone positioning techniques. Although such a staged approach can achieve anterior and posterior calvarial expansion, it is less effective in reducing the abnormal width and height of the skull. Therefore, we believe that the extra time and effort taken to achieve combined exposure of the front and back of the head are more than compensated for by the superior cosmetic results obtainable by this approach in carefully selected patients.
Draping To facilitate visualization of the entire cranial vault during the operation, it is essential to avoid overly restrictive draping of the head. Typically, the child receives an antibacterial shampoo on the evening before surgery and another in the operating room after positioning is achieved. The upper face, head, and posterior cervical region are then prepared with Betadine (povidone-iodine) scrub, alcohol, and Betadine solution. Corneal protection is achieved either with ointment, protective contact lenses, or a tarsorrhaphy; in patients with significant proptosis, a combination of approaches may be required to avoid intraoperative corneal injury. Towels are then draped around an area just above the tip of the nose, across the malar region and the middle of the ears, and around the upper cervical region (Fig. 36–3A). A second layer of adhesive drapes is then placed over the towels. During the reconstruction, the surgeon can then get direct feedback regarding the impact of intraoperative manipulations on the total calvarial appearance.
Skin Incision A bilateral incision is made extending from the vertex midway between the coronal and lambdoid sutures to just above the top of the ear. For cosmetic purposes, a zig-zag incision (Fig. 36–3A) leaves a less noticeable scar and is currently preferred, although a linear incision can also be used. Shaving the hair is not necessary, although clipping a small strip along the planned incision line may simplify subsequent closure. The above approach allows the most flexibility for anterior and posterior visualization and does not compromise exposure options for any future operations that may be required (e.g., a midfacial advancement later in childhood).
Exposure The skin is opened using a no. 15 blade, and the subcutaneous tissues and galea are incised using a fine needle-tip cautery. This achieves excellent hemostasis without the need for skin clips and minimizes blood loss. The skin flaps are dissected subperiosteally forward to expose the orbital region and backward to expose the foramen magnum region (Fig. 36–3B). Periorbita is reflected off the roof and the superior half of the medial and lateral walls of the orbits.
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Bilateral frontal and occipital craniotomy bone flaps are then marked. The position of the bone cuts is designed to allow removal of the frontal and occipital convexity while leaving a midline strut of bone to protect the sagittal sinus and torcular as well as biparietal struts, which are used in subsequent height adjustments. A 1 cm wide bilateral occipital bandeau with a lateral, inferiorly directed “tongue” is also removed for later use in the occipital advancement (Fig. 36–3C). The actual bone cuts are performed using a high-speed drill (Midas Rex; Fort Worth, TX); the M8 attachment is used to place strategically located bur holes and the B5 attachment is used to connect the bur holes. Because these children sometimes have increased intracranial pressure and areas where the dura has eroded through the bone, it is important to carefully dissect the dura from the undersurface of the bone before attempting to remove the bone flaps.
Orbital Advancement The dura is reflected off the anterior aspect of the frontal and temporal fossae. Using a broad malleable retractor to protect the dura and narrow malleable retractors to protect the periorbita, bilateral osteotomies are made through the orbital roof, beginning 5 to 10 mm posterior to the orbital margin and extending medially just anterior to the crista galli, above the frontonasal suture, and laterally just above the frontozygomatic suture inferiorly and through the sphenoid ridge superiorly. The bone cuts are begun with a highspeed drill and completed using a straight osteotome. The orbital bar osteotomies are continued posteriorly to incorporate a “tongue” of the squamosal portion of the temporal bone, which, as noted below, plays a role in the advancement (Fig. 36–3C). Because the lateral portion of the sphenoid bone is characteristically thickened and displaced anteriorly and superiorly, this abnormal bone is partially resected. The orbital bar is recontoured using wedge-shaped partial-thickness cuts through the posterior surface of the bone to facilitate remodeling (Fig. 36–4). The bar is then advanced forward and inclined downward slightly to correct the fronto-orbital elevation and retrusion and reduce the abnormally broad angulation of the lateral orbital margin. Because the entire anterior cranial base is small in these patients, the bones on both sides are advanced at least 10 mm medially and as much as 25 mm laterally (Fig. 36–4A). In these severely affected patients, an effort is made to achieve as much of an advancement as the bony geometry and soft tissues will allow. Bone grafts are secured to the posterior surface of the orbital bar in the midline and over each orbit to maintain the bar in its advanced position. The lateral aspect of the advanced orbital bar is also held forward using a tongue-and-groove technique (Fig. 36–4B). The tongue of the orbital bar is positioned in a groove that is fashioned within the temporal bone anterior to the synostotic coronal suture, to discourage posterior displacement of the bar while allowing further spontaneous advancement with brain growth. To keep the midline bone graft opposed to the posterior surface of the orbital bar and to maintain the contour of the lateral orbital angle, heat malleable absorbable miniplates are currently used. The use of absorbable fixation
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Figure 36–3 (A) The exposure obtained after draping and the planned incision are shown. (B) Skin flaps have been reflected anteriorly and posteriorly, exposing the superior orbits and foramen magnum regions,
respectively. (C) The frontal and parieto-occipital bone plates and the orbital and occipital bandeaus have been removed.
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246 Pediatric Neurosurgery priately positioning the bandeau, the occipital bone can be advanced by at least 15 mm. The bandeau is held in place using absorbable sutures except in the midline, where one or two of the barrel staves are held in opposition to the bone strut using absorbable miniplates. In older patients, miniplates may also be used to secure the tongue-andgroove construct.
Height Reduction
Figure 36–4 The orbital bar is recontoured by making a series of wedge-shaped partial-thickness osteotomies along the posterior cortex as indicated. (A) The bone is then advanced forward by at least 10 mm medially and up to 25 mm laterally as the lateral orbital angle is normalized. (B) The reconstructed and advanced orbital bar is then secured in position medially using bone grafts and laterally using a tongue-and-groove technique. 10.1055/978-1-60406-039-3c036
avoids the risk of transdural migration of metallic implants, which has been observed with wires and nonabsorbable miniplates that have been left in place for many years in the setting of ongoing brain growth. Elsewhere, absorbable (2–0 Vicryl) sutures or absorbable miniplates are used to secure the orbital bar in place.
Occipital Advancement Barrel-stave-like cuts are then made in the remaining occipital bone, extending down toward the foramen magnum region (Fig. 36–5A). In some cases, large bridging veins are encountered in the region of the torcular herophili, which should not be sacrificed. These may limit the inferior extent of the barrel-stave-like cuts in the midline, but using the advancement techniques outlined below, the residual bone does not hamper completion of the occipital expansion. The bones are first green-stick fractured outward using a bone bender to expand the skull posteriorly. The expansion is stabilized by bridging each of the barrel staves to the bandeau of occipital bone that has been excised, recontoured, and replaced in a tongue-and-groove fashion into the remaining occipital bone, posterior to the site of the lambdoid suture (Figs. 36–5B and 36–5C). By appro-
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Once the fronto-orbital and occipital advancements have been completed (Fig. 36–6A), a fiber-optic intracranial pressure monitor is placed through the right parietal bone into the brain parenchyma in preparation for the height reduction step. After the pressure stabilizes, which takes up to 20 minutes, the cranial height is reduced by resecting a rectangular wedge from each of the biparietal strips and gently tightening the bone edges together using 28 gauge wire or 2–0 suture (Fig. 36–6B). If indicated, the vertex of the skull is also shifted posteriorly by sliding the struts backward before repositioning. Because the combined frontal and occipital advancements have substantially increased the anteroposterior dimension of the calvaria before the height reduction is performed, intracranial pressure often remains in a normal range during the height reduction. However, in those patients in whom the pressure does increase significantly during this maneuver, great care is taken to avoid sustained elevations above 20 mm Hg. In such cases, the wires are released and then tightened down gradually during a period of up to 45 minutes. In all cases, the pressure after completion of the height reduction, which ranges from 1 to 1.5 cm, should be <15 mm Hg. The final position of the biparietal struts is then secured using absorbable miniplates.
Final Recontouring The frontal and occipital bones are next recontoured and often reoriented to correct the brachycephalic shape of the calvarial vault by narrowing the abnormally wide appearance of the frontal and parieto-occipital convexities (Fig. 36–6C). The recontoured frontal bone segments are connected to the orbital bar using a combination of absorbable miniplates and sutures. A solid connection in conjunction with continuous bony resurfacing is employed to avoid cosmetically unacceptable gaps or irregularities over the forehead. However, the bones are left free-floating toward the vertex so as not to restrict subsequent anterior skull growth. In the occipital region, the recontoured bone plates are sutured to the bandeau using 2–0 absorbable sutures and absorbable plates, and are left free-floating toward the vertex. Thus, no rigid fixation is employed in the vertex region to allow subsequent expansion of the cranial vault.
Closure Techniques Because a primary goal of the operation is to expand the volume of the calvarial vault, which is generally constricted pr-
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Figure 36–5 (A) Barrel-stave-like osteotomies are then made in the occipital bone. (B) After each of the barrel staves is green-stick fractured outward, the occipital bar (which has been removed separately and remodeled) is advanced and secured to each of the staves to immediately expand the skull posteriorly. (C) The advancement is also secured in place laterally using a tongue-and-groove technique. 10.1055/978-1-60406-039-3c036
eoperatively in patients with syndromic synostosis, the skin closure sometimes poses a challenge. The wound must be closed without excessive tension to avoid skin breakdown, wound dehiscence, and collapse of the construct. For cases in which the closure appears to be under tension, superficial relaxing cuts on the inner (galeal) side of the flap will often allow the flap to elongate several millimeters without compromising the integrity of the skin or its vascular supply, thus allowing for a largely tension-free closure. The skin flaps are approximated in two layers using absorbable sutures in the galea and skin. A Jackson-Pratt drain, left in the subgaleal space and brought out through a separate incision, is commonly kept in place for 1 to 3 days until the drainage has largely abated. After the swelling has subsided, the patient is fitted with and maintained in a soft padded helmet for approximately 1 month to encourage skull remodeling in an anteroposterior direction and to protect the construct in the event of a fall.
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Patient Monitoring As noted above in reference to the anesthetic considerations, close hemodynamic and temperature monitoring is essential for the safe performance of these extensive operations. During the height reduction step, monitoring of intracranial pressure is useful to avoid precipitous increases in pressure that can lead to venous infarction and brain injury. No other monitoring is routinely used during these procedures.
Specialized Instrumentation High-speed drills, such as the Midas Rex drill, greatly facilitate the extensive bone work employed in the procedures. High-speed oscillating and reciprocating saws are useful adjuncts in performing certain cuts of the orbital osteotomies, but much of this work can also be accomplished using the Midas drill. A variety of osteotomes, bone-holding forceps,
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248 Pediatric Neurosurgery
Figure 36–6 (A) The appearance of the skull after the fronto-orbital and occipital advancements but before the height reduction. At this stage, the brain is fairly slack and does not completely fill the space provided by the anteroposterior expansion. The planned area of bone removal from the biparietal struts is indicated by the arrows. (B) With an intracranial pressure monitor in place, the cranial height is reduced
by ~15 mm, which immediately expands the brain in an anteroposterior direction to fill in the increased volume provided by the prior frontal and occipital advancements. The struts are generally translated posteriorly to diminish the frontal prominence. (C) The frontal and occipital bone plates are recontoured and often repositioned to reduce the width of the skull.
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and bone-bending instruments are also essential for recontouring and reconstructing the various bone fragments.
Postoperative Management Including Possible Complications Median blood loss for the above operation is ~400 ml, approximately two to three times the typical blood loss of a fronto-orbital advancement; median operating time, including anesthesia induction, patient positioning, and skin preparation, is ~8 hours, which again is approximately twice the length of an average anterior calvarial reconstruction. In view of the proportionally greater magnitude of this procedure in comparison with a conventional forehead advancement, the potential for complications is correspondingly higher. Because we have been fortunate enough to avoid any significant complications in our institutional series of patients, it is difficult to state on a percentage basis the likelihood of various complications, but in our preoperative discussions, we stress each of the risks outlined below, which should theoretically be at least as likely in these patients as in children undergoing a more limited frontoorbital advancement. First, the potential for life-threatening bleeding is probably the greatest risk of the procedure. When superimposed on the expected blood loss from the skin flaps and bone edges, inadvertent injury to a major dural venous sinus or large bridging vein during bone dissection can rapidly produce hemodynamic compromise. Because many of the patients with syndromic synostosis have impaired cranial venous return as a result of jugular foramen stenosis, great care must be taken to avoid venous injury. Adequate amounts of blood products must be immediately accessible in the operating room in the event of excessive bleeding, and clotting factors should also be employed as the blood loss approaches one blood volume. Second, because free bone flaps are raised over virtually the entire skull, the consequences of a severe wound infection are potentially catastrophic. Fortunately, with meticulous attention to sterile technique, the use of intravenous antibiotics during the operation, and the avoidance of subgaleal hematoma collections by external drainage, serious infections have not been encountered in our series of total calvarial reconstructions. Minor wound infections or areas of dehiscence occur occasionally and are dealt with effectively using local measures and antibiotic therapy. Third, the risk of brain injury from the cranial bone manipulations is a potential concern, particularly during the height reduction step. During all portions of the reconstruction, attention should be directed to avoiding maneuvers that produce excessive compression of the intradural contents. This is critically important during the height reduction step, when careful monitoring of intracranial pressure is essential for detecting significant compression of the brain or dural venous sinuses and avoiding inadvertent neural injury. However, in our experience, major pressure elevations are rarely encountered with the height reduction because generous fronto-orbital and occipital advancements have been performed to increase the intracranial volume.
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Fourth, intraoperative cerebrospinal fluid (CSF) leakage may be encountered as a result of a dural tear during dissection or during the craniotomies or osteotomies. It is essential to repair these lacerations in a watertight fashion and to test the seal of the closure using a series of Valsalva maneuvers to prevent postoperative CSF leakage or pseudomeningocele formation. A final issue that is of importance in considering the outcome after a cranial reconstructive procedure is the quality of both the aesthetic and functional results. The techniques described in this report were developed as a result of our frustration with the suboptimal cosmetic results achieved with conventional anterior cranial vault remodeling for syndromic bilateral coronal synostosis associated with severe brachyturricephaly and the recognition that, with more limited approaches, a significant percentage of children manifest cranial volume restriction that results in intracranial hypertension during early childhood, which carries the potential for late functional deterioration. The approach outlined here represents a modification of previous techniques applied for brachyturricephaly. The notable alterations are in the way in which the frontal and occipital bones are advanced and held in position to maintain the cosmetic correction while still allowing for progressive calvarial expansion. In particular, the advanced frontal and occipital bars are stabilized using a combination of tongueand-groove osteotomies and absorbable miniplates and sutures. This avoids the “loss of correction” that can occur after free-floating or weakly buttressed forehead and occipital advancements. The fixation achieved is sturdy enough to resist the compressive forces applied by the weight of the child’s head, but not so rigid that it restricts further calvarial growth. We and the families of our patients have been extremely satisfied with the cosmetic results achieved in the immediate postoperative period as well as the long-term results that have been obtained. We have observed, during an extended period of follow-up, that postoperative head growth has tracked along normal percentile curves, and excellent cosmetic results in terms of calvarial shape have been maintained, which indicate that the degree of fixation provided does not severely limit further cranial growth.
Conclusion In summary, the technique of total calvarial reconstruction outlined here has provided gratifying results in carefully selected children with coronal synostosis and associated brachyturricephaly, with an acceptable increase in the overall complexity of the operation in comparison with conventional fronto-orbital advancement procedures. These technical modifications have enhanced the stability of the reconstruction without restricting future calvarial growth and have improved the quality of the postoperative aesthetic result. The issue of timing of the operation may be important for optimizing the cosmetic and functional outcome and minimizing morbidity. By delaying the operation until 6 to 12 months of age in children without evidence of increased intracranial pressure, we have been able to reconstruct the skull to nearly adult dimensions while allowing
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250 Pediatric Neurosurgery the potential for continued calvarial growth. At this age, with the aforementioned caveats, we have found the operation to be relatively safe and well tolerated. Acknowledgment This chapter is a revision of the chapter, “Combined FrontoOrbital and Occipital Advancement for Total Calvarial Reconstruction” by Ian F. Pollack, M.D., and H. Wolfgang Losken, M.D. The chapter appeared in the Neurosurgical Operative
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Atlas, Volume # 1, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank H. Wolfgang Losken, M.D, for his help and efforts on the original chapter published in the first edition of this work. Illustrations were provided by James A. Rosendale, M.S.
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37 Lumbosacral Meningoceles Ciaran J. Powers, Eric M. Gabriel, and Timothy M. George
Patient Selection Neural tube defects occur in ~2500 to 6000 children born in the United States each year and are thought to result from disturbed neurulation during the fourth week of gestation. Due to the prevalence of these conditions, an aggressive public health policy advocating the importance of prenatal maternal nutrition (especially the inclusion of folate and B12) have decreased the incidence of children born with neural tube defects in high-risk areas. Phenotypically, neural tube defects include a host of anomalies ranging from anencephaly to spina bifida occulta. A subtype, spina bifida cystica, refers to spinal dysraphisms including meningoceles and myelomeningoceles. A meningocele is a relatively uncommon form of spina bifida cystica composing <10% of all patients with open neural tube defects. It is defined as a cerebrospinal fluid (CSF)-filled, midline cystic mass that is covered by meningeal layers and often a thick epithelialized membrane. Gross surgical specimens of resected tissue usually appear free of neural elements, but histological examination can reveal evidence of ganglion cells, aberrant peripheral nerve, and tissue suggestive of spinal cord. Unlike the pathogenesis of the myelomeningocele, the embryopathy of meningoceles is poorly understood. In addition, the role of folate in prevention of meningoceles has yet to be defined. As with other neural tube defects, a multifactorial etiology may be postulated that involves either a defect in a genetically determined intrinsic pathway or abnormal effects of an environmental factor that disturb the intrinsic developmental program. Either process likely leads to a spinal developmental defect that occurs late during the process of neurulation or in the immediate postneurulation period resulting in the formation of a meningocele. The presence of limited dorsal myeloschisis with meningoceles may allude to this being a form of defective primary neurulation, although ventral meningoceles may arise or be patterned embryologically earlier (i.e., during gastrulation, not neurulation). Meningoceles usually are incidental findings at birth, although they can be diagnosed by ultrasound in the prenatal period as cystic spinal lesions that may be associated with hydrocephalus. Meningoceles can be found anywhere along the neuraxis, but occur more commonly in the lumbosacral region and less often in the cervicothoracic area. Meningoceles of the cervical spine are very rare entities character-
ized by mirror movements, spinal cord tethering, and good neurological outcome with appropriate surgical management. Cervical meningoceles have a rare association with neurofibromatosis type 1 (NF-1) and Klippel-Feil syndrome. Lateral thoracic meningoceles have also been described. These lesions may present as mediastinal masses and seem to have an association with NF-1. Ventral sacral meningoceles may also occur and are associated with the so-called radiographic scimitar sign and Currarino’s triad (a presacral mass, sacral bony abnormalities, and an anorectal malformation). Meningoceles can be associated with other lesions elsewhere along the neuraxis. Dandy-Walker malformations and lesions that produce the tethered cord syndrome such as fibrous dorsal bands, a thickened or lipomatous filum terminale, myelocystocele, and split cord malformations may be associated with meningoceles. Unlike the more common myelomeningocele, the prognosis for future ambulatory development in a child with a meningocele is excellent. The primary goals of the surgical repair of meningoceles are to prevent infection by providing a definitive closure of the defect and to release any tethering lesions that may lead to late neurological compromise. Because meningoceles often have a thick epithelial membrane covering, they often do not present the same surgical urgency as do myelomeningoceles. Nonetheless, early surgical therapy should be considered the standard of care. Nonoperative treatment or prolonged delays in surgery may place the patient at risk for delayed neurological deterioration or breakdown of the covering meninges and/ or epithelia with ensuing infection. Another benefit of early surgery is to minimize the parents’ psychological trauma of having an “abnormal” child while promoting the parent-child bonding necessary for healthy early childhood development. The exact timing of surgery should be individualized for each patient based upon any coexisting morbidity, but once again the repair should be performed as early as possible. Here we will consider dorsal meningoceles of the lumbosacral spine and their clinical and operative management.
Prenatal Evaluation and Care Prenatal screening tests may have limitations because meningoceles can be covered by a thick epithelia and the mother often will not demonstrate elevated serum-fetoprotein or acetylcholine-esterase levels as with myelomeningoceles. However, with the current specificity of in utero
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252 Pediatric Neurosurgery ultrasonography, meningoceles can be diagnosed prenatally. Associated in utero hydrocephalus can also be detected by ultrasound. Many meningoceles go undetected prenatally, and these infants can still undergo a safe vaginal delivery. If a meningocele or hydrocephalus is detected prior to birth, the high-risk obstetrics team usually prefers to carry the pregnancy to term and deliver the child via cesarean section to avoid damage to the meningocele sac, fetal distress, and to avert maternal complications. Counseling for the parents should be started to explain the significance of the spectrum of potential spinal anomalies while exposing them early to the myelodysplasia support systems. Most parents exhibit well-adapted coping strategies and understand how to better care for their children when counseling is begun early.
Postnatal Evaluation and Care After delivery, a meningocele will be noted on physical examination if it had not been diagnosed in utero. A thorough multisystem evaluation should be performed by the neonatologist to assess the overall condition, specifically the function of the cardiopulmonary and gastrointestinal systems. The neurological examination is best performed with the infant at rest. Careful assessment noting the size, composition, and location of the meningocele, along with measurement of the head circumference, palpation of the spine, and inspection for other cutaneous manifestations of dysraphism should be noted. The sensory examination is done by stimulation of distal dermatomes and by proceeding rostrally while watching the upper extremities and/or face for a reaction. The motor examination consists of manual muscle testing to assess for tone and strength. Sharp stimulation of the arms or torso may be used to evaluate lower extremity movements and coordination. Bowel and bladder dysfunctions are difficult to assess at initial examination except for the absence or presence of an anal wink. Evaluations by a pediatric orthopaedist and a urologist should be conducted to further assess the skeletal and genitourinary systems.
Preoperative Preparation Prior to closure of the meningocele, the sac should be protected with moistened sterile dressings and the infant is best nursed in the prone or lateral decubitus position. If the lesion is covered with skin, antibiotics are not necessary until the time of operation. If the lesion is open, prophylactic antibiotics consisting of a combination of intravenous ampicillin/ gentamicin should be started in the intensive care nursery. It is important to have an accurate radiographic assessment of the sac and the remainder of the spinal cord to identify any other anomalies, such as split-cord malformations, dermoids, lipomas, or other tethering lesions. Magnetic resonance imaging (MRI) is currently the gold standard for providing detailed images and should ideally be performed preoperatively to enable proficient operative planning. If an MRI is unobtainable, ultrasound or myelography with computed tomography will suffice.
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Anesthesia The anesthetic care of patients with meningoceles is ideally performed by a pediatric anesthesiologist. Specific anesthetic considerations include the possibility of coexisting disease, airway management, positioning during induction, volume status, and the potential for hypothermia. Although meningocele patients do not usually have hydrocephalus, they may have other anomalies such as congenital heart disease or renal abnormalities that are of importance to the anesthesiologist. Airway management may be more difficult if the meningocele is located in the cervical region, thus precluding a supine intubation. In this instance, a left lateral decubitus position would suffice. Care must be taken to protect the meningocele during supine intubations. Utilizing a cushioned, sterile ring around the abnormality and a towel roll beneath the shoulders, intubation may proceed safely. As with all newborns, keen attention to the volume status must be displayed. Third-space fluid losses from open body surface areas are usually not problematic in the surgery. However, if skin mobilization techniques are necessary to close a defect, then these losses may be encountered. Routine use of two intravenous lines is recommended for volume supplementation. Meticulous hemostasis is an absolute must, and blood loss should be minimal with this operation (<5 cc). Conservation of heat is very important for newborns, as their temperature regulating mechanisms will not maintain a stable core body temperature. The infant must be transported in a heated incubator, and the operating room should be warmed to 27°C prior to surgery. Radiant heat lamps are used during induction and emergence of anesthesia to warm the patient. Routine monitoring of blood pressure, pulse oximetry, and temperature is necessary. A general anesthetic regimen consisting of N2O in O2, fentanyl, and low-dose Forane (isoflurane) is used for the procedure. If the infant is term and healthy, immediate postoperative extubation should be considered. Basic postoperative anesthetic management is utilized.
Operative Procedure Instrumentation Standard neurosurgical and microsurgical instrumentation is used for this procedure. Bipolar cautery is essential for hemostasis, and it avoids any current flow through adjacent neural structures. Although surgical loupes may be used, an operating microscope has the distinct advantage of higher magnifications and a directed light source, which allows for better delineation of the surgical planes. A carbon dioxide laser with superpulse capability should also be available in the event a tethering lesion is present that requires gentle dissection of tissue that merges with the spinal cord. Intraoperative electrophysiological monitoring is not necessary, but can be of some benefit in certain instances.
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Figure 37–1 Positioning of the child in the prone position. Towel rolls are placed across the chest and pelvis and the head is placed in a gel or foam “doughnut.” 10.1055/978-1-60406-039-3c037_f001
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padded with 0.5 in. Reston® foam (3M, Reston, St. Paul, Minnesota), and the arms are kept in a position for easy access by the anesthesiologist. The skin surrounding the defect is prepared with Betadine (povidone-iodine) scrub, and DuraPrep® (3M. Reston, St. Paul, Minnesota) solution, whereas a standard Betadine solution is used to gently coat the exposed sac covering. No neurotoxic antibiotics or antiseptics are used. The surgical field is defined by clear, sterile adhesive plastic drapes. Lightweight adhesive paper surgical drapes that are water impermeable are then placed to cover the table and separate the anesthesia team from the exposed field. The goal of this draping regimen is to minimize weight and keep the unexposed areas dry. Preoperative antibiotics, usually nafcillin, are given prior to making the skin incision.
Patient Positioning and Draping The patient is carefully positioned prone with rolled towels placed transversely beneath the chest and pelvis so that the abdomen is freely suspended and the femoral vessels are kept patent (Fig. 37–1). All pressure points must be carefully
Surgical Approach The initial skin incision is made along the circumferential line around the meningocele where the normal skin meets the dysplastic sac coverings (Figs. 37–2A and 37–2B). Linear
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Figure 37–2 (A) Intraoperative photograph of a lumbosacral meningocele. (B) Illustration depicting the initial incision at the edge of the dysplastic skin and incision line if more exposure is necessary. (C) Transverse view of meningocele showing the arachnoid and dural herniation. The arrows depict the plane of dissection. A dorsal tethering band is shown attached to the spinal cord.
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Figure 37–3 The meningocele sac is dissected free from the subcutaneous tissue and lumbodorsal muscle and fascia. The bifid lamina is exposed and a laminectomy is done for better exposure. The incision line for opening the arachnoid is shown.
extensions are made along the midline in both cephalad and caudad directions if necessary. It is essential to preserve anatomical planes to aid in the dissection of the meningocele stalk. Upon entrance into the subcutaneous tissues, the deeper thoracolumbar fascia should be identified in the plane outside of the meningocele sac. Blunt dissection is continued to define the point where the stalk protrudes through the bifid lamina (Fig. 37–3). A subtotal laminectomy of the bifid lamina should be performed to provide greater access to the stalk. This can be easily accomplished using a small 2 or 3 mm single action ronguer.
The meningocele stalk, composed of arachnoid and dura, is dissected free circumferentially (Fig. 37–3). Utmost care must be exhibited to avoid inadvertent opening of the sac prematurely, as the sac may contain nerve roots or a dorsal tethering band that should be fully visualized prior to ligation. With the sac defined, the arachnoid should be opened near the junction with the dura, and the contents of the sac should be inspected. Dural retraction by placing 4–0 Nurolon or Vicryl sutures aids with inspection of the sac (Fig. 37–4). At times a partial laminectomy of the next rostral or caudal lamina is needed to provide better intradural exposure.
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Figure 37–4 The contents of the sac are exposed. Dural retraction sutures are in place. A thickened filum terminale is sectioned away from the conus medullaris, and a dorsal band is sectioned near the spinal cord.
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37 The operating microscope is used to help with the intradural inspection. Any tethering bands should be cut close to the spinal cord (Fig. 37–4). Sectioning of the filum terminale should be performed to avoid any delayed neurological deterioration. The filum is most easily identified by its dorsal midline position, a pale yellow appearance with vertiginous surface vessels, and it is often thickened. The filum is divided after bipolar cauterization at the most caudal distance from the conus medullaris. Care must be taken to ensure hemostasis of the filum, because after sectioning the cut ends will retract out of the field of view and make control of bleeding difficult. If other tethering lesions are present such as lipomas and dermoids, they should be repaired. Prior to closure, the excess sac covering is excised, which is primarily arachnoid. This should leave a dural layer that can be sutured in a watertight fashion.
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Postoperative Management Including Possible Complications Postoperatively the patient is brought to an intensive care nursery in a heated incubator. A flat position is maintained for 3 to 5 days to facilitate healing of the dural and fascial closures and to prevent a CSF leak. Maintenance of a horizontal position should not preclude parent-infant bonding, and the parents are encouraged to hold the child as often as is feasible. The infant may resume oral feedings, and continuation of antibiotics beyond the perioperative period is not necessary. Transfer to a regular ward may occur when the medical issues have been fully addressed. Although the incidence of hydrocephalus is lower than in children with myelomeningoceles, head circumference measurements should be performed daily.
Closure Meticulous closure of the defect is critical to prevent postoperative complications. Primary closure can often be achieved; however, if the defect is >8% of the thoracolumbar area, mobilization of a muscle flap may be necessary. A standard four-layer closure is performed by first utilizing a fine absorbent monofilament suture (e.g., 6–0 PDS) for the dura (Fig. 37–5), interrupted 3–0 Vicryl sutures for the thoracolumbar fascia, interrupted and inverted 4–0 Vicryl sutures for the subcutaneous tissues, and a running 5–0 absorbable suture for the skin. The incision is then covered with an antibiotic ointment and a sterile dressing.
Complications The operative mortality for repair of a meningocele approaches zero, and the major morbidities associated with this operation are wound infections and CSF leaks. Attention to the details of skin preparation, the use of perioperative antibiotics, and wound closure will minimize these risks. Blood loss should never be a problem as long as attention to hemostasis is paid during each step of the procedure.
Follow-up The outcome of patients with meningoceles is very good in terms of normal neurological development and intelligence. To facilitate the best possible future for these patients, it is important for them to be followed by a myelodysplasia clinic. The multidisciplinary approach utilized by such as clinic enables early detection and treatment of possible multisystem disorders.
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Figure 37–5 After excess meningocele dura and arachnoid are removed, the dura is closed with a running 6–0 monofilament suture for a watertight closure.
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38 Surgical Correction of Unilateral and Bilateral Coronal Synostoses Jack Chungkai Yu and Ann Marie Flannery Synostosis of one or both of the coronal sutures results in substantial deformity of the developing skull. Unilateral coronal synostosis is a commonly occurring, generally nonsyndromic premature fusion of the coronal suture. It presents as calvarial asymmetry varying from mild to severe. Usually detected on physical examination between the ages of 3 months and 1 year, the affected child has flattening of the supraorbital ridge, retrusion of the forehead, and ridging of the coronal suture on the affected side. Compensatory growth may result in bulging of the forehead on the contralateral side as well as the parietal region on the affected side. The ear is moved forward compared with the contralateral side. In extremely severe cases, the entire basicranium may be affected, resulting in pointing of the nose to the affected side and extension of the asymmetrical growth to the base of the skull, which, in turn, results in cranial scoliosis. Differential diagnosis includes positional molding that results in a relatively posterior positioning of the ear on the affected side, compared with the unaffected side, and a lack of ridging of the suture. Occasionally, atypical presentation of anterior plagiocephaly resistant to nonsurgical therapy has underlying frontosphenoid synostosis. Bilateral coronal synostosis may be isolated or may be associated with craniofacial syndromes and the maldevelopment of the basicranium and/or synostosis of other sutures. Isolated bilateral coronal synostosis presents as brachyturricephaly (i.e., “towering head”). The direction of growth is predominantly superior. The anterior fossa is foreshortened and, in more severe cases, exorbitism may occur because of deficiencies in the effective orbital volume. Bilateral coronal synostosis is commonly associated with craniofacial anomalies, and children seen with this disorder should be carefully screened for other anomalies that may give information regarding their syndromes. Recent advances in molecular genetics have identified mutations in six genes, belonging to three categories, that are frequently associated with coronal craniosynostosis. The six genes are: FRFR1, FGFR2, FGFR3, TWIST, MSX2, and FBN1. The mutations in fibroblast growth factor receptor interfere with normal cell signaling and often are gain-of-function mutations. MSX2 and TWIST are transcription factors and FBN1 codes for fibrillin 1, a structural protein. Commonly associated syndromes include (1) Crouzon syndrome, associated with FGFR2 and FGFR3 mutation, characterized by midface hypoplasia as well as bi-
lateral coronal synostosis; (2) Pfeiffer syndrome, associated with FGFR1 and FGFR2 mutations, characterized by the presence of broad thumbs plus midface hypoplasia and bilateral coronal synostosis; (3) Saethre-Chotzen syndrome, associated with TWIST mutation, resulting in haploinsufficiency, characterized by low hairlines, partial cutaneous syndactly, flat, angulated thumbs, and persistent wide-open fontanelle associated with bilateral coronal synostosis (the midface anomalies in this disorder can be less prominent); and (4) Apert syndrome, associated with FGFR2 mutation, characterized by polysyndactylies, severe acne, and cleft palate. Children with syndromic craniofacial anomalies often require more than a single fronto-orbital advancement, although this surgery is frequently a first step in the complete reconstruction. The fronto-orbital advancement described in this chapter will be followed by midface surgeries timed to accommodate facial skeletal growth but delayed as long as possible to allow for maximum effectiveness. The use of distraction osteogenesis has significantly improved our ability to achieve a more normal morphology and function for these patients.
Patient Selection In our experience, children commonly need early surgery at the age of 3 to 6 months in severe syndromic bilateral coronal synostosis. In less severely affected patients and nonsyndromic patients, operative intervention often can be delayed until an optimal age (which is between 6 and 12 months) to allow for maximum correction and minimum morbidity. It remains unclear at this time what the proper role should be for endoscopic craniotomies with postoperative cranial molding in treating coronal synostosis. Children with both unilateral coronal and bilateral coronal synostoses can be adequately evaluated using computed tomography (CT) with three-dimensional reconstruction. In unilateral coronal synostosis, the CT shows closure of the suture on the affected side, compared with the unaffected side, as well as the asymmetrical calvarium. In bilateral coronal synostosis, sutural closure, foreshortening of the anterior fossa, deficiencies of the orbital roof and rims, and possible abnormalities in the midface structures are demonstrated. It is also important to evaluate the cerebrospinal (CSF) production and resorption to exclude
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38 Surgical Correction of Unilateral and Bilateral Coronal Synostoses 257 the possibility of hydrocephalus. Chiari malformation can also develop in individuals with syndromic bilateral coronal synostosis. Bilateral fronto-orbital advancement is our surgery of choice for both unilateral and bilateral coronal synostoses. Surgery is indicated in patients who have a moderate to severe deformity as a result of coronal synostosis and is probably best done after 6 months of age. If done sooner, there is a possibility of relapse due to malleable infant bones. After 12 months of age, although surgery can be done, the soft tissue envelope may be somewhat constricted and the bone is more rigid, which may result in a less than ideal correction; in addition, due to the reduced osteogenic ability of the dura, more extensive bone grafting is required. Technical modifications described below can improve the outcome in such late-presenting cases. Only patients with the most severe positional plagiocephaly should be treated by the same procedure used for correction of coronal synostosis. In children <9 months of age, the dynamic headband can be used in an effort to promote correction during active skull growth. Bands are most effective when used early in positional molding in conjunction with physical therapy to normalize cervical range of motion. The ideal age is probably around 3 to 4 months to take advantage of the substantial brain and calvarial growth that takes place in the first 6 months of life. We offer surgery to the child diagnosed at >12 months of age with a severe positional plagiocephaly deformity and to the child who does not respond to a course of molding helmet therapy with a severe deformity by 9 to 12 months of age. In such cases, high-resolution CT scans are done to rule out synostosis of skull base sutures such as frontosphenoid suture. Risks of the surgery include blood loss, bone loss from infection or re-absorption, infections, dura lacerations, CSF leak, damage to the orbital contents, deformities of the forehead, failure to correct or recurrence of the dysmorphology, and, on very rare occasions (0.1 to 1%), operative mortality. We have found complications to be rare. Generally, this surgery is well tolerated in healthy young children and infants at high-volume craniofacial centers.
Preoperative Preparation Infants and children who require the surgery are generally in good health and neither steroids nor anticonvulsants are required. We have treated patients using intravenously administered antibiotics (usually Ancef [cephazolin ]) started the morning of surgery to lessen the risks of postoperative infection. During surgery, there is a small chance of entry into the nasal ethmoid region. It is therefore necessary to cover for the common microbial flora of the upper airway.
Anesthetic Technique After the induction of general anesthesia, two large-bore intravenous lines are established, as well as an arterial line, and usually a central venous line. The central venous line is
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used to monitor central venous pressure as well as to withdraw air, as there is a small chance of air embolism during any craniofacial procedures. Agents and techniques used to control intracranial pressure or withdraw CSF are generally not necessary. At one time, Doppler ultrasound monitoring was not done, as the reported incidence of significant air embolism has been low. Despite the low incidence, we now use the precordial Doppler ultrasound on every transcranial case for craniosynostosis at the Medical College of Georgia. The Doppler probe is placed near the sternal angle at the left second intercostal space to monitor the outflow in the pulmonary trunk. Once the signals are acquired, the Doppler probe is securely tapped in position and padded. Special considerations during the postinduction, preoperative phase include careful maintenance of the patient’s body temperature during placement of lines and preparation. Because of the small size of the child and relatively large body surface area, hypothermia can occur easily. We therefore keep a warming blanket on the bed beneath the patient and use heating lamps above the patient. The ambient temperature of the room is set at a level best suited to maintain normal temperature of the patient rather than to suit the comfort of the staff in the room. Radiant heat loss is reduced once the patient is draped, and room temperature can be readjusted to accommodate staff; however, if the patient has become hypothermic during the period of preparation and positioning, it will take some time for the child to rewarm. During surgery, an additional heating blanket over the chest and legs of the patient can be used, if necessary. Avoidance of hypothermia averts associated complications such as myocardial depression, coagulopathy, and slow metabolism of anesthetic agents, which leads to a prolonged recovery from anesthesia. Maintenance of adequate blood supply during the craniofacial procedure is critical, as the two leading causes, of operative mortality are hypovolemia and venous air embolism. The circulating blood volume of the average infant or young child is only ~70 to 75 cc/kg. Hemostasis may be difficult during the course of the procedure, and a continuous steady loss of blood can be expected once the bone removal has begun. The surgeon should be constantly aware of blood loss during the operation and should communicate estimates relatively frequently to the anesthesiologist, who often cannot completely visualize the operative field and whose estimate of blood loss may be affected by the amount of irrigation used and other factors. We do not make any osteotomies until blood is in the operating room. In general, it is prudent to replace estimated blood volume lost at ~1 cc per cc on an ongoing basis throughout the procedure rather than waiting for the patient to develop obvious signs of a deficit. This replacement allows for a cushion of safety should unexpected heavy blood loss occur. Coagulation factors, platelets, and calcium may be required in cases where several total blood volumes are transfused. It is often prudent in older children to wire the endotracheal tube to the mandible prior to the start of the operation. Preoperative recombinate erythropoietin and the use of cell savers have reduced, but not eliminated, the need for transfusion.
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Operative Procedure Patient Positioning The patient is positioned supine, and the operating table should be rotated 110 degrees away from the anesthesia team to allow maximum access to the cranium and face. An alternative position would be to turn the table to 90 degrees away from the anesthesia team, which would allow access to most of the calvaria, with some limitations on the side closest to the anesthesia team. This limitation is compensated for by a somewhat better access to the airway and the left arm for the anesthesia team; optimal positioning is generally chosen after discussion between surgeons and the anesthesiologist. A 180 degree turn of the operating table with anesthesia at the foot of the table is not recommended.
Surgical Technique The entire face is prepared using a Betadine (povidoneiodine) scrub and paint, down to the submental area. Often, the tape securing the endotracheal tube is prepped. Because the reconstruction includes devitalized bone and metal implants, we shave the patient’s hair along the proposed incision line generously; usually, a 2 cm wide strip is shaved. Once the prep and scrub are completed, the head is elevated on a folded half sheet or two surgical towels. The towels are wrapped around the remaining hair inferior to the chosen incision and sewn or stapled into place. A split sheet is then used to complete the draping and is wrapped underneath the head. The bilateral coronal incision is marked by holding 2–0 Vicryl suture tightly against the scalp to make a straight indentation. We make a sinusoidal pattern in the parietal region and then a continuous straight line across the midline and down to the other side where the incision line again becomes sinusoidal (Fig. 38–1). This “stealth” incision helps
create a more normal hairline for improved appearance pattern (especially in patients with straight hair and especially when the hair is wet, later in life). This incision can sometimes terminate at a point 2 to 4 cm above the ear to further improve the postoperative appearance. Two techniques are used for hemostasis of the scalp. One technique includes infiltration of the scalp incision with lidocaine and epinephrine. For children weighing >10 kg, 0.5% lidocaine with 1:200,000 epinephrine is used. For children weighing <10 kg, this standard preparation is diluted with normal saline 1:1 to yield a 0.25% lidocaine with 1:400,000 epinephrine. An alternative is to infiltrate with 0.25% bupivacaine with 1:200,000 epinephrine, which is longer acting and may provide better postoperative pain relief at the incision site. Usually 1 cc/kg of 0.25% local anesthetic solution can be used. It is instilled prior to prep to allow the epinephrine sufficient time to work. Raney clips are used on the skin edges as the scalp flap is created. The second hemostatic technique uses a running and locking stitch with 2–0 Prolene sutures ~1 cm on either side of the incision. These locking stitches are not removed until just before skin closure. Fronto-orbital advancement starts with an incision through the skin and subcutaneous tissue and galea. The subgaleal space is then dissected anteriorly in a blunt fashion, using wide periosteal elevators augmented by monopolar cautery. The preference is to use the needle electrocautery and obtain meticulous hemostasis from the very beginning of the operation. The pericranium is left intact. The temporalis muscle is identified bilaterally. An attempt is made to keep a cuff of pericranium attached to the temporalis muscle as it is dissected off of the skull. In a very young child, it is not uncommon for the small temporalis muscle to be dissected as part of the scalp flap. Approximately 2 cm above the superior orbital ridge the pericranium is incised and is dissected off the bone with the scalp flap. The scalp flap is folded anteriorly and protected with wet laparotomy pads.
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38 Surgical Correction of Unilateral and Bilateral Coronal Synostoses 259 The bilateral coronal craniotomy is then outlined using methylene blue. The pericranium is incised using electrocautery. The pericranium is dissected away from the area of the proposed saw cuts. A Hudson brace hand drill (Aesculap, Center Valley, Pennsylvania) is used to make the bur holes as shown. The Hudson brace is effective on the thin infant skull and yields viable fragments of bone, which are useful when filling holes remaining in the calvaria. This “bone dust” is stored in normal saline until the end of the procedure. The calvarial flaps are then undermined using a periosteal elevator. A Midas Rex Legend F1-B5 drill (Medtronic, Minneapolis, Minnesota) or Anspach drill (Anspach Effort, Inc., Palm Beach, Florida) is used to create a bicoronal bone flap. In older children, a larger bit is used. This bone is removed and given to the plastic surgery team to begin the reconstruction. After completion of the frontal craniotomy, the dura mater is dissected off the endocranial surface of the anterior orbital roof, the squama of the temporal bone, and the sphenofrontal suture (Fig. 38–2A). A series of osteotomies is then made for the removal of the supraorbital bar (supraorbital bandeau) to allow contour correction ex vivo to achieve the desired symmetry prior to its advancement. The power instruments used for this portion of the operation should have thin saw blades with lightweight hand pieces for the delicate precision bone cuts. We prefer the air-driven Micro 100 system or the electric Micro E system by Hall (ConMed Linvatec, Largo, FL), or the TPS by Stryker (Stryker Corp., Kalamazoo, MI). With the brain well protected by malleable retractors, the tenon portion (the rectangular posterior extension) of the supraorbital bar is cut using the reciprocating saw (0.6 mm blade thickness). The osteotomy proceeds from posterior to anterior, paralleling the zygomatic arch; it is carried across the posterior edge of the floor of the anterior cranial fossa in the region of the frontosphenoid suture. Great care must be taken to ensure adequate protection of anterior and lateral aspects of the temporal lobe at this point, as the foreshortening of the anterior cranial base is associated with a more anterior extension of the middle cranial fossa (Fig. 38–2B).
Before the bone cut extends to the orbital roof, in addition to protection of the temporal lobe, the frontal lobe must be retracted and the globe protected. The lateral orbital wall osteotomy is then made with an oscillating saw (20 degree offset angle, 5.5 mm blade width, 0.4 mm blade thickness). This cut is connected to an oblique osteotomy of the lateral orbital rim. A thin 10 mm wide osteotome is then introduced intracranially, cutting across the frontosphenoid, frontozygomatic, and sphenozygomatic sutures, to complete the lateral orbital mobilization. The orbital roof cuts join in the midline anterior to the foramen cecum and cribriform plate. With the supraorbital bar completely mobilized and removed, the deformity is corrected on the back table. There is usually bony thickening in the lateral aspect of the greater and lesser wings of the sphenoid (near the sphenosquamosal suture). This hyperostotic area is reduced with a contour bur to allow molding into the desired shape. The bony half Z-plasty stabilizes the supraorbital bar anteriorly, allowing for the anterior placement with good bone contact while maintaining a smooth lateral orbital rim contour. However, this limits the maximum amount of anterior advancement to the width of the lateral orbital rim. This is secured with 3–0 PDS sutures. The posterior aspect of the tenon is stabilized with a single absorbable plate, if needed; otherwise, the fronto-orbital bandeau is tilted slightly to achieve good frontal takeoff angle and also some overlapping posteriorly that can allow locking of the osteotomies, providing excellent stability without the need for plates and screws (Fig. 38–3). With the supraorbital bar fixed in the advanced position, the symmetry and contour of the frontal bone constructs are corrected. This typically requires several maneuvers, including left and right bone flap switching, rotating the bone flaps, kerf cuts, simple contour reduction by burring, and molding with bone-bending forceps. Once the desired forehead shape is achieved, the frontal bone pieces are ligated in place with 3–0 monofilament absorbable sutures. Although a lateral canthopexy is not essential, its use prevents rounding and downward drifting of the lateral canthus
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Figure 38–3 (A) The orbital bandeau has been secured in position by a 3–0 PDS. Advancement is generally 15 mm. (B) The bandeau reshaping is notable by the distance from the brain on the patient’s left. (C) Multiple 3–0 PDS secure the bandeau.
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and improves the overall appearance of the patient’s face after surgery. Using a 1.5 mm wire-passing bur, two holes are made in the superior lateral orbital rim. The lateral canthal ligament is grasped with a single hemostat from the tissue side of the coronal flap; two stainless steel no. 10 wires (30 gauge) are then passed through canthal tissue. These wires are then passed through holes on the reconstructed orbit in the superior lateral aspect ~2 to 3 mm cranial to the medial canthal attachment. These wires are secured tightly by twisting down. In patients <12 months of age, the calvarial defects resulting from the advancement are allowed to reossify. In older patients, either demineralized bone or split-thickness calvarial bone grafts are used to fill in the defects. Bone dust and chips produced during instrumentation earlier in the operation are saved and mixed with blood into bone paste and placed into bur holes and other minor defects (Fig. 38–4). The wound is irrigated with gentamicin containing warm saline (80 mg/l), and the coronal flap is closed in two layers.
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Closure should begin with the resuspension of the temporalis muscle. Depending on the age of the child and size of the tissues, a 2–0 or 3–0 absorbable suture, such as Vicryl, should be used to pull the temporalis muscle back to the galeal cuff preserved during the initial dissection or to wires or plates in the reconstruction. Alternatively, a pair of drill holes 1 cm apart with a loop of 3–0 Vicryl suture placed prior to replacing the frontal or parietal bone allow for good anchorage of the muscle. This covers the defect in bone that occurs with the orbital recontouring and improves the appearance and functional outcome. The temporalis muscles are anteriorly transposed by making back-cuts posteriorly. This is important to avoid a postoperative temporal hollow. If it is not possible to suspend the temporalis muscle to the galeal cuff wires, plates, or screws, and no Vicryl loops as described are available, it can be connected over the top of the calvaria to the contralateral temporalis muscle using a 2–0 or 3–0 Vicryl suture. Closure continues with several interrupted sutures of 2–0 Vicryl in the galea to hold the galea in position. Repair of
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38 Surgical Correction of Unilateral and Bilateral Coronal Synostoses 261 reasonably rigid fixation. Absorbable plates and screws have almost completely replaced metal fixation systems, especially in the young infant and in infants with craniofacial syndromes in whom the passive internal translocation of plates and screws has been observed in the past decade. As described in the procedure, the Midas Rex, Anspach, or other high-speed drill is used for calvarial removal. The Micro E drill by Hall, running on electrical power or compressed air, works well for the creation of the orbital bandeau; this drill needs to have a straight, a 90 degree, and a reciprocating oscillator blade and bur. The TPS power tools by Stryker with 75,000 rpm are also quite acceptable.
Postoperative Management Including Possible Complications Figure 38–4 The forehead is reshaped and held in place with 5–0 suture or, as in this case, absorbable mesh and screws. 10.1055/978-1-60406-039-3c038_f004
the galea is then continued with 4–0 Vicryl sutures. The skin is closed with a running continuous lock stitch of either 4–0 nylon (which is stronger) or 4–0 Prolene (which has a color that is easier to locate). Polysporin ointment is applied. A compression dressing is used, and the patient is usually awakened, extubated, and taken to the intensive care unit. We occasionally drain serous sanguinous effusion with round 7 mm drains to grenade-type suction bulbs for 48 to 72 hours, depending on the output.
Special Instrumentation Numerous types of plates and screws are now available for intraoperative use. We have used the Luhr microfixation system, which has the smallest screws and plates (0. 8 mm); however, their metal composition (vitalium) creates slightly more artifact on postoperative CT. We have also used the Synthes 1.0 mm screw system (Synthes, Inc., West Chester, PA) that combines the appropriately small size with less artifact from the titanium alloy. We avoid using hardware as much as possible, but the immediate stability afforded by microfixation is very desirable in some reconstructions. We now achieve that by using the absorbable plates and screws. These products are absorbed in 6 to 12 months and provide
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The most commonly feared postoperative complication is infection of the bone. Osteomyelitis or, more accurately, osteitis, because there is very little real marrow, will result in subsequent loss of orbital and cranial bone. Fortunately, this is rare and is avoided by preoperative antibiotics, meticulous technique, intraoperative irrigation, and reduced operating time. Other concerns include CSF leakage, which may occur because of dural lacerations during removal of the cranial bone or resection of the orbital bar, especially across the nasion. We now find that it is not necessary to dissect the falx away from the foramen cecum. This substantially lessens the risk of dural laceration and of subsequent CSF leak. As reported in very young children or those with craniofacial syndromes, remodeling of the bone can result in intracranial migration of the microscrews and plates. We avoid this risk by using as few screws as possible and by performing the operation when the child is 6 months or older whenever possible. Screw migration, loosening, and the need for subsequent screw removal is always a possibility and should be discussed with the patient’s parents and family. A failure to correct or a relapse of the calvarial and orbital asymmetry is an uncommon risk. Parents should be made aware of this. This risk is best avoided by operating on the slightly older child whenever possible. The patients with underlying FGFR or TWIST mutations are more likely to have a less ideal longterm outcome. Parents should also be aware that the head will always feel somewhat “lumpy” or “bumpy” as a result of the surgery, even though this improves with time.
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39 Myelomeningoceles, Split Cord Malformations, and Filum Terminale Dysgenesis Robert F. Keating Despite significant advances in detecting and evaluating a tethered spinal cord, considerable challenges remain with respect to the surgical management of this clinical entity, regardless of the etiological origin. Numerous conditions may account for the source of tethering in the spinal canal, especially in those individuals predisposed to spina bifida aperta and occulta. In particular, postrepair myelomeningocele fibrosis, split cord malformations (SCMs), and filum terminale dysgenesis have all demonstrated the propensity to inhibit normal physiological movement of the spinal cord. Although the surgical objective remains liberating the spinal cord and roots, a targeted approach will depend upon the type and involvement of tethering. In this chapter, the surgical management for each clinical entity (i.e., myelomeningocele, SCM, filum dysgenesis) will be reviewed with particular attention directed to associated surgical pearls and pitfalls.
Patient Selection The clinical presentation of a tethered cord will be dependent upon the age of the patient as well as the presence of spina bifida. The majority of patients will exhibit their first symptomatology during accelerated growth periods. The manifestation of symptoms will be related to the patients’ preexisting neurological baseline. Although patients with previously repaired myelomeningoceles have universally been demonstrated to have radiological evidence for cord tethering, it has been estimated that 30 to 50% of these children will eventually become symptomatic. Individuals with incomplete lesions with good functional capacity unfortunately are at the greatest risk for further neurological compromise, and it thus remains imperative to follow these patients closely in a multidisciplinary fashion. Should these patients develop low back or lower extremity pain/discomfort, or changes in their neurological exams, gait, or bowel/ bladder habits, serious consideration must be given to the likelihood of tethering. Progression of scoliosis or positional changes in the lower extremities may also herald neurological deterioration secondary to tethering. Delay in diagnosis as well as treatment may jeopardize an already precarious neurological balance.
Children without overt spina bifida often present in a more insidious fashion. Diagnosis is often delayed until significant neurological changes are underway. Nevertheless, detailed historical review will frequently demonstrate symptoms of pain/cramping as well as lower extremity asymmetry (e.g., difficulty fitting shoes). Enuresis, frequent urinary tract infections, and progressive scoliosis in addition to internal/ external ankle rotation may also be present. In addition, neurocutaneous markings such as hypertrichosis, dermal sinus tracts/dimples, and gluteal fold asymmetry may also help to direct the clinician’s suspicion. Nevertheless, the goals remain early diagnosis and expeditious release of the cord and affected roots.
Preoperative Preparation Individuals with spina bifida should be followed by a dedicated, multidisciplinary team on a regular basis. This team should consist of pediatric specialists in neurosurgery, orthopaedics, urology, and neurology, as well as experienced pediatricians, rehabilitation specialists, social workers, child life specialists, and a dedicated nursing staff. Each individual will bring his or her own expertise to the evaluation and should help to provide a comprehensive overview of the patient’s condition as well as clinical needs. Children with spina bifida occulta should also be evaluated by the same team when their initial presentation demonstrates the likelihood of a tethered cord. Clinical suspicion is followed by a detailed magnetic resonance imaging (MRI) evaluation of the total spinal cord, (as well as plain spine films) to assess the level of presumed tethering as well as to exclude other concomitant dysraphism. Although the majority of patients with preexisting spina bifida will manifest continued presence of the cord at the site of prior repair, the diagnosis may be more difficult in the child with borderline tethering (e.g., cord at L2-3). In addition, there have been reported examples of patients with a normally positioned conus who present with classic symptomatology and who have been seen to have abnormal motion on dynamic studies as well as in the operating room during open exploration. Nevertheless,
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the diagnosis is usually obvious with routine MRI. At this point, the patient should be examined by all involved parties, especially urology for baseline urodynamics as well as orthopaedics to follow any scoliosis. Any other associated systemic problems should be resolved prior to surgical intervention. After a complete workup by all individuals, electrophysiological baseline studies (somatosensory evoked potentials, MEP, electromyography) are undertaken. This is done either as an outpatient or more commonly in the operating theater prior to skin incision. Patients undergo surgical release in an expeditious fashion, particularly if manifesting progressive neurological deterioration. Patients seen to have evidence for tethering, after workup of associated neurocutaneous lesions, routinely undergo operative intervention in a prophylactic fashion. Today the majority of pediatric neurosurgeons believe that prophylactic surgery is warranted in view of low morbidity and the inherent danger of permanent damage in the setting of neurological deterioration. For the infants diagnosed before the development of any symptoms, it is best to wait till the child is 6 months old, to allow for greater total blood volume as well as ease of repair (technical considerations). Evidence of progressive neurological change should indicate an earlier surgical date. The surgery is characteristically bloodless, and the need for autologous or directed donation of blood is usually minimal. However, in older individuals with an expectation of difficulty closing the dura in a watertight fashion (e.g., lipomyelomeningocele), it may be helpful to have an autologous donation of cryoprecipitate for the manufacture of fibrin glue intraoperatively. Cell savers (Electromedic) have the capability of plasmaphoresis and can produce plateletfibrin gel in patients >18 kg. This has been demonstrated to reduce the likelihood of postoperative cerebrospinal fluid (CSF) leaks in patients with insufficient dura for closure. Preoperative medical clearance is completed by the patient’s primary pediatrician, being careful to ensure that the patient is free from any urinary tract infections (confirmed by urinalysis) as well as pulmonary problems. Routine bloods include a complete blood count in addition to a type and hold. We do not routinely perform any coagulation studies. Exposure to other children (and their ubiquitous viruses) is minimized during the week prior to surgery and nonsteroidal anti-inflammatory drugs are avoided in the older children for a period of at least 2 weeks prior to surgery.
Operative Procedure
Anesthesia
The majority of myelomeningoceles tether at the previous site of repair, although it is not infrequent that other areas of attachment may also be present. Occasionally, coexisting concomitant dysraphism involving SCMs or canal stenosis just cephalad to the initial repair may also contribute to the overall setting of tethering, and thus remain important to discern prior to any surgical intervention. Nevertheless, the clear majority of myelomeningoceles will demonstrate considerable fibrosis on the dorsal and lateral surfaces. It is not uncommon to find one side more involved than the other, and the lysis of adhesions here is best left until the surgical conclusion.
Patients are usually brought into the hospital the day of surgery, unless preexisting medical conditions warrant an overnight stay. At the time of surgery, they are started on nafcillin 50 mg/kg loading dose (1 g maximum dose) with 25 mg/kg iv q 6 hour for a period of 48 hours. Vancomycin is substituted for the patient with penicillin/cepahalosporin allergies. In addition, steroids may be administered prior to skin incision and continued for a 48 hour period postoperatively. Large bore intravenous lines, an arterial line, and a Foley catheter are all placed prior to commencement of the surgery.
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Positioning Positioning of the patient involves a prone station with the patient supported by foam bolsters under the chest, which will prevent any abdominal compression. The head is supported by a “doughnut” or well-padded cerebellar headrest. Meticulous attention is directed to areas of potential pressure sores (e.g., chest, pelvis, knees, ankles, elbows) with abundant padding and care to avoid any stretching of the brachial plexus as well as potential ulnar and peroneal nerve palsies. In addition, it is imperative to avoid any direct pressure from underlying catheters (e.g., Foley), electrocardiogram leads, or even wrinkles in the surface material. This type of surgery has the potential to proceed for extended periods and proper positioning will be crucial in preventing unnecessary morbidity. Mayo stands are placed over both the head and feet to offer further protection. The surgeons will work on either side of the patient either in a sitting or standing position with anesthesia at the head of the table and the operating nurse at the feet.
Myelomeningocele The majority of myelomeningocele repairs inevitably present later with radiological tethering; in addition, a significant number of children eventually demonstrate clinical evidence of neurological deterioration. Reasons for tethering remain variable, although a majority of patients manifest significant spinal canal stenosis with subsequent development of local as well as diffuse fibrosis. In addition, inadequate cephalad exposure at the time of initial repair may also predispose the patient to subsequent adhesions at this level. Nevertheless, any physiological tethering in a patient with an incomplete spinal cord lesion will invariably lead to the unacceptable loss of additional neurological function. The inherent principle goals remain identification of any associated tethering agents (i.e., fibrous adhesions, dermal vestiges, components of the prior repair, etc.) as well as ensuring an adequate thecal decompression and release of the affected spinal cord and roots.
Anatomy
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264 Pediatric Neurosurgery Skin Incision After careful positioning (see positioning in section operative procedure, above) the patient’s previous skin incision is infiltrated with 0.5% lidocaine with 1:200,000 parts epinephrine (0.25% lidocaine with 1:400,000 parts epinephrine for infants <20 kg). This will depend upon the prior skin incision and may involve a vertical or horizontal incision. Vertical incisions allow potential future orthopaedic procedures with instrumentation to be undertaken easily. The initial incision is superficial over the prior repair, with this being carried down to the level of the fascia cephalad and caudal to the site of the original placode. At the level of normal anatomy, exposure of the dorsal spinal elements is undertaken with electrocautery utilizing a fine-needle point tip. It is imperative to identify normal spinal elements before opening the dural tube. Identification of normal anatomical landmarks will facilitate exposure of the previously tubulated neural placode within its bed of fibrotic adhesions. Dissection is carried caudally from normal and recognizable anatomical landmarks to the level of the neural placode. Utilizing preoperative MRI studies, it is often helpful to initially dissect on the opposite side relative to the area of greatest localized adhesions. Dissection is completed dorsally as well as laterally, exposing remnants of atretic roots as well as probable evidence of the prior neural tubulation repair. This may be done with the assistance of evoked potentials for preservation of cephalad function in addition to microscopic or loupe magnification. The utilization of the yttrium-aluminum-garnet (YAG) laser greatly simplifies lysis of dense adhesions, and its contact tip effortlessly permits the development of an anatomical plane between the cord and epiarachnoid adhesions while at the same time allowing for delicate tactile feedback. A diamond knife may also be used to facilitate release of arachnoidal adhesions. As expected, it is vital to remain in the plane between nervous tissue and surrounding fibrotic adhesions. This is facilitated by starting at a point of normal tissue interface (roots or normal functioning cord). Any bleeding encountered is handled by the placement of small pieces of Gelfoam or occasionally by microcoagulation. Normothermic saline irrigation will also help considerably. When the placode and cord have been adequately released, the cord will now lie on the ventral surface within the canal (versus the previous dorsal presentation). Roots initially seen to exit in a cephalad direction will also appear to be under less tension. It is rare to see any cephalad movement of the cord, especially in the setting of prior myelomeningocele repairs, and thus it should not be used as an end point for adequate untethering of the cord.
Closure With all intraspinal surgery it is important to obtain as close to a watertight closure as possible. This often remains a significant challenge in children with deficient dura and overlying soft tissue. Nevertheless, if care is taken during the initial takedown to preserve viable tissue planes, the closure will be greatly simplified. It must also be remembered that an adequate thecal sac (to allow for sufficient
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CSF space) must be left behind to help minimize postoperative retethering. If the thecal sac is not capacious, it may be necessary to construct a fascial patch from nearby lumbosacral fascia or even fascia lata. The use of foreign materials is strongly discouraged due to the strong probability of an associated fibrotic reaction and subsequent retethering. The closure of this layer is performed with 4–0 nylon with subsequent muscle and subcutaneous layers employing 2–0 and 3–0 Vicryl. The skin is closed with a running, locking 4–0 Monocryl suture to ensure proper tension throughout the length of the incision. The monofilament nature of the suture will minimize any local tissue reaction, and the suture will absorb over 3 to 4 weeks without the need for removal. Vaseline gauze and sponge dressings or cyanoacrylic material (e.g., Dermabond; Ethicon, Somerville, New Jersey) as an air-occlusive barrier are applied at the end.
Postoperative Management The patients are maintained on steroids and antibiotics for a 48 hour period and are nursed in a prone, head-down/ buttocks-up position for the initial 48 hours, taking care to observe for any possible CSF leak. During this period it is helpful to maintain aggressive sedation as well as analgesia (Valium [diazepam] and narcotics). By the third postoperative day, the patients are permitted to lie in any position provided it is flat. On the fourth postoperative day the head of the bed is elevated to 30 to 45 degrees with the patient being allowed to stand or sit the same day. Henceforth physical therapy is started and the patients are mobilized by the fifth day. Patients are transferred to an inpatient rehabilitation facility if warranted. While confined to bed, the patients are maintained on a Foley catheter to prevent retention as well as wound breakdown. It is also important to prevent any accidental wound contamination with urine or stool. The use of Dermabond may help while providing an occlusive barrier. Frequently, the diaper is left unattached on the back surface to minimize contact with the underlying skin.
Complications CSF leaks are undoubtedly the most problematic complication for this type of surgery. With excellent tissue closure and conservative postoperative positioning, this infrequently poses any significant challenge. Nevertheless, in those instances it may be necessary to reinforce the incision with an additional suture. A pseudomeningocele will be easier to manage than an open CSF fistula. In addition, it will often be necessary to prolong the prone position in these individuals. For the problematic patient, it may be necessary to return to the operating theater for a new tissue closure utilizing fibrin glue, vascularized tissue flaps, or a lumbar drain. It is also imperative to exclude the possibility of raised intracranial pressure/hydrocephalus (i.e., shunt malfunction). Fortunately, this is uncommon, particularly if the patient’s shunt function has been evaluated preoperatively. The difficulties with feeding while lying in a minimal Trendelenberg’s position are considerable for some individuals, although it is remarkable how well the majority of children are able to eat in this position. In any event, this
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position is a short-term inconvenience (48 hours) and generally poses few nutritional risks for the patient. Pulmonary secretions may also pose significant difficulty for the patient and nursing staff. Frequent suctioning and aggressive pulmonary physical therapy will help considerably. These patients are prone to pneumonia and need to be watched closely. Wound infections rarely present before the fifth postoperative day and can be visualized early with subsequent treatment directed locally in conjunction with systemic antibiotics.
Pearls ●
Identify normal anatomical landmarks (cephalad). Preserve as many layers of tissue when initially dissecting. ● Start with the easiest site of tethering first and work from both directions as needed. ● A careful, multilayer closure will minimize CSF leaks as will preoperative confirmation of shunt function. ● Ensure conservative postoperative positioning. ●
Pitfalls ●
Exercise great caution with initial dissection over the placode. ● Maintain a tissue plane between neural tissue and fibrosis. ● If this is lost, return to normal anatomy. ● Ensure that a capacious CSF space is present at conclusion. ● Minimize cord coagulation; use hemostatic agents.
Split Cord Malformation The presence of a SCM (type I) predisposes the patient to eventual tethering at the site of the bony, fibrotic, or cartilaginous spur. In the case of type II SCMs the patient may be tethered by ubiquitous arachnoidal adhesions. Most often found at the thoracic level, SCMs may also occur at the cervical or lumbar level. Onset of symptoms characteristically occurs during growth spurts and occasionally will present at a later age (adulthood). Symptomatology remains similar for other etiologies of a tethered cord, and treatment is directed toward removal of the offending tethering agent.
Anatomy Type I SCMs are defined by a split in the spinal cord, usually at the thoracic or lumbar level, involving a bony, cartilaginous, or fibrotic spur originating from the ventral, dorsal, or both surfaces of the spinal canal. The cord is most often split into two hemicords (right and left side), but on rare occasions may actually present with true diplomyelia (two separate and distinct cords) (Fig. 39–1A). Plain spine films will often demonstrate bony defects, but may be less helpful with fibrotic or cartilaginous adhesions as seen in type II SCMs. An MRI will fortunately manifest the various types of lesions and is extremely important in localizing the site of tethering as well as in demonstrating any other associated lesions over
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the entire spinal canal. Midline defects separate the cord as well as act as a site of tethering. The central island of bone, fibrotic, or cartilagenous tissue is invariably surrounded by an associated dural sleeve, and it is important to remove not only the central component but the dural tube as well. When the origination of the SCM lies on the ventral surface of the spinal canal, after the spur is removed it will be necessary to repair the ventral dura as well as the posterior dural tube.
Skin Incision After routine prone positioning with bolsters as well as administration of intraoperative electrophysiological monitoring (see preoperative preparation section, above), an incision (knife or Colorado needle) is made in the midline extending one level above and below the level of the SCM (x-ray confirmation may help). This is infiltrated with 0.5% lidocaine with 1:200,000 parts epinephrine to minimize incisional bleeding. Electrocautery with a fine needle point is then employed to extend this to the level of the posterior elements, with care being taken in the event of spina bifida occulta and the possibility of open posterior elements. After x-ray confirmation of the appropriate level, the posterior elements are removed to expose the dural tube. Frequently it is possible to appreciate the SCM on the dorsal surface with its associated dural sleeve (Fig. 39–1B). In certain individuals the defect will remain within the thecal sac and require opening the dural tube. In this setting, intraoperative ultrasound may facilitate accurate localization of the SCM. Removal of the spur is done by rongeur or drill for difficult bony lesions (Fig. 39–1C). Following obliteration of the diastematomyelic spur, if any defect exists on the ventral dura, primary closure will be necessary, if possible (Fig. 39–1D). If this proves impossible, fibrin glue may offer considerable assistance. The remains of the dural sleeve must then be excised to remove any likelihood of further tethering. The spinal cord is left untouched but now resides within a singular dural tube. Any posterior defects in the dura are correspondingly closed with 4–0 Nurolon (Ethicon; Somerville, New Jersey) sutures (as done for the ventral repair).
Closure Following successful watertight closure of the dural tube, the paraspinal musculature is closed in two layers with 2–0 absorbable suture (e.g., Vicryl). The subcutaneous layer is closed with similar material utilizing 3–0 suture. The skin is closed with 4–0 Monocryl in a running, locking fashion to ensure even tension throughout and minimize the likelihood of any CSF leak. Subsequently, the sutures will absorb over 3 to 4 weeks without the need for removal. Standard dressings or Dermabond is applied.
Postoperative Management Patients are nursed in a prone position for 24 to 48 hours depending upon the integrity of the dural closure. It may also be helpful to have the patient in a mild Trendelenberg’s position (3–5 degrees) with the buttocks raised. Great care is taken to prevent any contamination of the wound dress-
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266 Pediatric Neurosurgery
A
B
C
D
Figure 39–1 (A) Axial cross-section of lumbar split cord malformation demonstrating ventral origination of an ossified spur splitting the cord into two hemicords. (B) Removal of the posterior elements exposing the dural tube with the split cord malformation spur giving rise to two hemicords that rejoin distally. (C) The ventral spur may be bone, carti10.1055/978-1-60406-039-6c039_f001
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lage, or fibrous tissue. Successful untethering requires removal to the level of the vertebral body. (D) After resection of the spur, the anterior dural defect is closed primarily if possible. This is facilitated in the lumbar region but may be difficult in the thoracic area. In this setting fibrin glue may offer considerable assistance.
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ing. The patients are maintained on steroids and postoperative antibiotics for 48 hours (i.e., nafcillin 25 mg/kg q 6 hour). It is also beneficial to have a Foley catheter in place until the patient is able to use a bedpan or bathroom. During this period aggressive use of sedation (Valium) as well as analgesics is strongly encouraged. By the second or third day the patient is allowed to be completely flat with the head of the bed being raised to 45 degrees the following morning. Successful toleration leads to sitting by the third/fourth postoperative day and standing/walking by the fourth/fifth day. Physical therapy is commenced when the patient is able to tolerate a sitting position, and patients are transferred to an inpatient rehabilitation facility if warranted. Adherence to this conservative regimen invariably leads to a successful recovery with the development of CSF leaks an unusual event (<2%). Complications are uncommon and are discussed in the preceding section on myelomeningoceles.
Pearls
an appropriate anatomical level, in the setting of restrained normal physiological motion, who also may benefit from the sectioning of the hypertrophic filum terminale.
Anatomy The origin of tethering lies in the abnormally large and developed filum terminale (frequently with associated lipoma), which in turn may limit the normal motion experienced by a spinal cord with routine flexion and extension of the spine. This may ultimately promote ischemic areas within the cord and lead to eventual symptomatology. Nevertheless, the presence of a filum dysgenesis may be demonstrated by either computed tomography (CT) or MRI as well as myelography. This commonly is accompanied by a small terminal lipoma and makes identification easy on both CT and MRI. Enlarged vessels may also be visualized on radiological workup. Nevertheless, it remains a simple matter to identify such structures intraoperatively. The filum routinely is dorsal as well as caudal and lies in the midline to the level of the coccygeal border. Visual confirmation is corroborated by intraoperative electrophysiological testing.
●
When exposing the level of SCM, exercise caution with the takedown of the posterior elements. ● Removal of the spur may be undertaken with rongeur or drill. ● It is necessary to remove the internal dural sleeve to remove the focus of tethering. ● Ventral repair of the dural defect may be difficult in the thoracic level and may be facilitated by fibrin glue.
Pitfalls ●
Use caution with the electrocautery when dissecting the posterior elements, especially with possible spina bifida occulta. ● Manipulation of the thoracic cord must be minimized when removing the spur, especially in patients symptomatic preoperatively. Evoked potentials may be helpful here. ● Care must also be taken to avoid bleeding from any ventral blood supply at the midline spur as these vessels may retract making control potentially difficult. ● A thorough multilayer closure is crucial to prevent CSF leaks, especially in patients with inadequately closed ventral defects.
Filum Dysgenesis A less common form of spinal cord tethering (although the incidence appears to be increasing), the presence of a filum terminale dysgenesis represents a real threat to the normal physiological motion of the cord. It is often straightforward with radiological studies (MRI) to identify an enlarged filum with caudal retraction of the cord. After intraoperative neurophysiological confirmation, the filum is transected with occasional cephalad movement noted in the free cord. In addition, there have been recent reports of patients with prominent filum terminales (i.e., lipomas) with the conus terminating at
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Skin Incision A midline incision from the lower level of tethering extending two levels caudal is made after infiltrating the skin with 0.5% lidocaine with 1:200,000 parts epinephrine. This should provide adequate exposure to identify the conus and origin of the filum terminale dysgenesis as well as offer excellent visualization of the distal filum. The incision is taken down to the level of the fascia and beyond with the electrocautery, utilizing a fine-needle point electrode. After exposure of the spinous process and lamina of the most caudal posterior elements (relative to the level of tethering), these are in turn removed to provide at least two level exposure of dura. This may be undertaken by standard laminectomy utilizing hand tools or a high-speed drill if one wishes to consider a laminoplasty. X-ray confirmation of the involved level at the start may expedite the limited opening. Following removal of the involved posterior elements, intraoperative ultrasound may facilitate the localization of the tethered conus in addition to the filum dysgenesis. The dura is carefully incised with a no. 15 scalpel blade, taking care to preserve the arachnoid plane if possible. Once an adequate window has been established, one should be able to appreciate the level of the conus as well as origin of the filum (Fig. 39–2A). Exposure remains limited to this window with intraoperative electrophysiological testing of the filum performed to confirm anatomical accuracy (Fig. 39–2B). Following corroboration, the filum is coagulated and transected in two places to minimize the likelihood of retethering and provide pathological confirmation. In rare instances, actual movement of the cord in a cephalad direction may be witnessed.
Closure After irrigation of the thecal sac with normal saline, the dura is closed with 4–0 polyfilament nylon (e.g., Nurolon) in a
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268 Pediatric Neurosurgery
A
B Figure 39–2 (A) Isolation of the filum terminale is facilitated by placement of a narrow cottonoid beneath. Care must be taken in the dissection to remove any adherent nerve roots (particularly small sacral roots), and the filum is tested electrophysiologically to confirm the absence of any neural elements before transection. (B) The filum has been 10.1055/978-1-60406-039-6c039_f002
running and locking fashion. This will act to provide even tension throughout the closure and is done in a watertight fashion. A piece of Gelfoam (or other hemostatic material) is placed over the dural defect. The muscle is subsequently closed in two layers with an absorbable 2–0 suture (e.g., Vicryl) and the subcutaneous layer with 3–0 material. The skin is closed with 4–0 monofilament (e.g., Monocryl) in a running, locking fashion. Subcuticular stitches are avoided in the setting of any dural opening and the possibility of a postoperative CSF leak. Standard dressings are applied, then removed after 48 hours.
transected in two locations and the cut end of the mobilized filum is now visualized at the left end of the photograph. Prior to the cut, it is imperative to coagulate any draining veins (often on the ventral surface) or significant bleeding can occur, which may be difficult to control, especially if the filum has retracted out of the surgical field.
the next 2 to 3 days to ambulation and eventual rehabilitation. Complications are uncommon and are discussed in the preceding section on myelomeningocele.
Pearls ●
Accurate preoperative localization of the tethered conus will allow minimal exposure to identify the filum terminale. ● The presence of the filum should always be confirmed with intraoperative electrophysiological testing.
Postoperative Management
Pitfalls
Nursing considerations are similar to those utilized for any tethered cord repair (see prior sections), with the only difference being a more aggressive approach to mobilization with simple dural repairs. The patients are kept prone for the initial 24 hours and then mobilized over the course of
●
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Care must be taken to dissect any adherent roots away from the filum prior to transection. ● Minimal mobilization of the tethered conus must be undertaken in addition to the use of evoked potentials.
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40 Lipomyelomeningoceles James Tait Goodrich
The surgical treatment of lipomyelomeningocele remains one of the most complex surgical treatments performed by a pediatric neurosurgeon. These lesions are notorious for their difficulty in determining the anatomy for resection and ultimate removal without worsening the neurological sequelae to the patient.
Patient Selection The diagnosis of a lipomyelomeningocele is usually made shortly after birth when the child is noted to have a lipomatous mass on the back (Fig. 40–1), typically in the lumbosacral region. In some cases, however, the clinical findings can be considerably more subtle. Clinical findings that might suggest a dysraphic state include skin tags, hemangiomatous nevi, patchy hypertrichosis (hairy skin tufts), and dimpling above the gluteal cleft. In the older child, clinical symptoms that are suggestive of a progressive tethered spinal cord syndrome include changes in gait, weakness, foot deformity (e.g., varus, valgus, and cavus changes in the feet) and pain. Increasing spasticity, progressive scoliosis, and wide-based gait are also worrisome signs. Changes in sensation, often quite vague at first, can be good predicators of spinal cord
tethering. One of the most subtle but extremely useful indicators for tethering is urological dysfunction. Initially this might be only a large bladder detected on magnetic resonance imaging (MRI). Changes in bladder function are often quite subtle, but clues that will help the clinician include an increasing number of bladder infections, stress incontinence, and enuresis. The surgical treatment of a tethered cord requires a release of the tethered spinal cord and placement of the spinal cord in the most anatomically normal milieu possible. To do this requires the removal of the tethering lesion (i.e., lipoma) and reconstruction of the spinal canal with the spinal cord placed within a cerebrospinal fluid (CSF) circulating space.
Timing of the Surgery Recently there has been some controversy as to the timing of the surgery for a lipomyelomeningocele. One end of the spectrum is to do nothing until the child becomes symptomatic; this option is favored by a minority. The present philosophy of the majority of U.S. pediatric neurosurgeons is to recommend surgery early on, before the child shows progressive evidence of neurological dysfunction. When the
A
B Figure 40–1 (A) A lipoma can be appreciated just above the gluteal cleft. In addition, there is a skin capillary hemiangioma overlying the lipoma—a not uncommon finding in these cases. (B) A young child is po10.1055/978-1-60406-039-3c040_f001
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sitioned for surgery, demonstrating a typical eccentrically placed large lipomyelomeningocele in the lumbosacral region.
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270 Pediatric Neurosurgery diagnosis is made shortly after birth, we like to postpone the surgery until the child is 4 to 6 months of age. The philosophy behind this timing is this additional period allows for a more mature hematological system plus a larger blood volume for the anesthesiologist. The initial 4 to 6 months of life are used for a thorough workup of the physiological and neurological status of the child. A diagnostic workup includes several helpful studies to assist the surgical team in working out the anatomy. Plain lumbosacral x-rays still remain quite useful for visualizing the nature of the dysraphic spine and in particular in forming a preoperative appreciation of any hemilamina or lack of lamina. In the past a myelogram with contrast-enhanced computed tomography was the most popular technique, but this has been now replaced with the MRI using both axial and sagittal cuts. If available, patients are monitored intraoperatively with somatosensory and motor evoked potentials plus motor nerve stimulation of the lower extremities, sacral, and rectal regions.
Preoperative Preparation Evaluation The preoperative evaluation of these children requires several studies to assist the spina bifida team in deciding the best course and sequence of surgery necessary. As part of the preoperative evaluation, the patient and family are seen by all members of the spina bifida team, which includes the following: neurosurgeon, orthopaedic surgeon, pediatrician, pediatric urologist, physiotherapist, social worker, and the child life specialist. After each team member has seen the patient and family, a conference is held and the surgical recommendations for the family are planned.
Preparation Children with a spina dysraphism not uncommonly have other system anomalies. As part of the preoperative workup we have cardiac and renal systems evaluated to rule out any unusual anomalies. The family pediatrician routinely does a well-baby checkup (including urinalysis) a day or two before the child is to be admitted. In addition, many of these children, because of a normally immature immune system, easily acquire viral and bacterial infections. If the child comes in with a fever and the workup shows no active bacterial infection (normal white blood cell count with no shift), we proceed with surgery. If the child has an upper respiratory infection but no signs of congestion, we will also proceed. However, if the child appears septic or an active bacterial source is identified, then the surgery is canceled and rescheduled. Before we instituted this protocol, nearly a quarter of our patients were canceled on the day of surgery because of an unknown fever source. With the above workup we have reduced this figure to <5%. Blood loss in these patients is usually minimal, as lipomyelomeningoceles are not typically vascular lesions. It is rare that a child needs a transfusion unless the child starts
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with a low blood count. Our anesthesiology team usually places a large-bore intravenous line of 20 gauge or larger. Arterial lines are placed for monitoring blood gases, hematocrit, electrolytes, etc., during the procedure. A Foley catheter is placed to monitor urine output. We do not routinely use steroids. Antibiotics are used (oxacillin 25 mg/kg), beginning with a preoperative dose and performed for 24 hours.
Operative Procedure Positioning The patient is placed in a prone position with the head resting on a “doughnut” headrest. Foam rubber bolsters are placed under the chest and abdomen so the abdomen is hanging free without compression, thereby reducing airway pressures. The anesthesia team is placed at the head of the patient, with a small Mayo stand over the head of the patient. The nursing team is placed on the opposite end at the foot of the patient. A small Mayo stand is placed over the patient’s legs. A second mobile stand is placed off to the side for surgical trays.
Skin Incision Typically the lipomyelomeningocele is eccentrically placed on the back (Fig. 40–1). We use either a long midline incision following the spinous processes or a horizontal incision placed over the center of the mass. One of the critical components of this surgery is being able to circumferentially isolate the lipoma as it ruptures out through the lumbodorsal fascia. A common error made early in a surgery is to attempt to go through the lipomatous mass looking for the spinal cord—this is a most hazardous approach. It is better to start with the first normal lamina (this will help the surgeon locate the dural margins) and then go out in a circumferential fashion and encompass the lipoma and follow it down to the lumbodorsal fascia (Fig. 40–2). This is a safe approach for all three types of lipomyelomeningoceles (to be discussed further). Resection of the lipoma off the spinal cord is determined by its position and relationship to the spinal cord and conus medullaris. For purposes of discussion we have broken these lesions down into three types, and each will be discussed separately with its own unique anatomy.
Anatomy of the Lipomyelomeningocele Preoperative radiological studies are critical in providing the surgeon an anatomical outline of the relation of the lipoma to the spinal cord. There typically occurs one of three anatomical types of lipomyelomeningocele, and each will be dealt with separately. Those anatomical situations include dorsal, caudal, and transitional lipomyelomeningoceles. For purposes of discussion, we describe the surgical exposure and resection for each type, as each has its own idiosyncrasies encountered while resecting.
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A
B Figure 40–2 (A) Intraoperative view of a dorsally placed lipomyelomeningocele after dissection of the lipoma from the surrounding structures. The relationship of the lipoma to the cord and roots can be appreciated in this view. The normal cord is to the right, and the lipoma arises out of the cord to the left. The distal end of the lipoma has been 10.1055/978-1-60406-039-3c040_f002
Dorsal Lipomyelomeningocele The dorsally placed lipomyelomeningocele is technically the easiest to deal with, as the nervous structures are all heading in an anterior direction toward the canal. In the true dorsally placed lipomyelomeningocele, it is important to determine where the lipoma intersects with the spinal cord (see Figs. 40–2 and 40–3). As previously discussed, it is important to reveal anatomically the circumferential margins of the lipoma as it erupts through the lumbodorsal fascia and muscle. The first normal lamina is identified and below it is the normal dura plane. The dura is opened and the intersection of the lipoma and spinal cord is identified: At this point the microscope (or loupe) is brought in for magnification. Using either a fine diamond knife or ophthalmic cataract knives, dissection is performed, with the lateral margins of the lipoma dissected free from the surrounding fascia. One side of the canal is usually more difficult than the other, and it is best to start with the easier side. The spinal roots are extremely helpful in determining where one is in relationship to the cord. In cases where there is a loss of anatomy, we stimulate with a nerve probe into the lipomatous tissue to sort out any nerve structures. Once the lipoma has been circumferentially exposed, it is then dissected off the spinal cord. The margin between the lipoma and the cord is never distinct, but often there is a fibrous plane between the lipoma and the cord. It is always safe to err on the conservative side and leave too much lipoma behind rather than risk injury to the spinal cord. Once the interface has been achieved, the CO2 laser is helpful in vaporizing any residual fat, and this technique reduces any undue physical manipulation of the conus or cord. Recently we have also been using the radiofrequency type of cautery (e.g., Ellman system), as this equipment generates much lower heat with less tissue necrosis, thereby potentially
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resected; the forceps holds the residual lipoma. (B) The appearance of the spinal cord after the resection of the lipoma. The spinal roots are now exposed under the removed lipoma on the left. Sutures are holding the residual margins of the lipoma as it erupts from the conus medullaris. The normal spinal cord can be seen to the right side.
reducing the risk of injury to the normal neural structures. Once the lipoma is resected, we take the plial margins and with a fine suture (typically a 6–0 Prolene) sew them together to entubulate the cord. This technique appears to be helpful in reducing retethering and also assists in determining anatomical planes for future surgeries. Closure techniques will be discussed at the end, as they are similar in all three types.
Caudal Lipomyelomeningocele The caudal lipomyelomeningocele presents its own challenges, as the anatomy is such that a portion of the lipoma will incorporate normal spinal roots. The exposure is the same as described for the dorsal lipomyelomeningocele, and the difficulty is the exposure of the terminus and distal end of the lipoma. As illustrated in Fig. 40–4, there is a notorious lack of anatomical planes between the lipoma and the spinal cord and roots. In this case, the surgeon must determine where the roots start and where to make an artificial dissection plane in the lipoma. Intraoperative nerve stimulation is extremely helpful in trying to sort out where the roots are traveling through the lipoma versus fibrous bands. To preserve neurological functions, it is key to identify the normal roots (i.e., functioning roots) and leave them in the residual lipoma. Reducing the dorsal bulk of the lipoma and freeing it up will help reduce the tether and continue to preserve function. Nothing is accomplished by cutting normal functioning nerve roots. Figs. 40–4A and 40–4B show a cross section in which the artist has reconstructed the anatomy and the total lack of normal anatomical planes that typically occur in these lesions. The plane to be dissected is determined by the surgeon and follows a plane that is the least disruptive of nerve structures. In these types of operations patience and a good deal of elec-
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Figure 40–3 (A) Artistic rendition of a dorsally placed lipomyelomeningocele. The relationship of the lipoma to the spinal cord and roots, here plus the surgical plane that needs to be developed, can be seen. (B) Axial view of the spinal cord and the relationship of the lipoma to the cord. Note the lack of discrete margins between the cord and the lipoma. In addition, the roots are rarely at the same level with one side, one typically being higher than the other; this is usually due to the lipoma being anatomically eccentric within the spinal canal. (C) Artistic depiction of a surgical resection of a dorsally placed lipoma. The normal dural margins are identified, the lipoma dissected circumferentially from surrounding tissue, and the surgeon is now dissecting the lipoma off the dorsal aspect of the spinal cord. 10.1055/978-1-60406-039-3c040_f003
trical stimulation of the nerve roots are key to reducing morbidity.
an alternative. The most common dissection is a continuation of the one shown in Fig. 40–5A, where the dissection is performed above the plane of the nerve roots.
Transitional Lipomyelomeningocele Transitional lipomyelomeningocele is one of the most treacherous lesions we deal with in pediatric neurosurgery. In this dysraphic lesion (Fig. 40–5) there are no anatomical planes anywhere near normal. Nerve roots course through the lipoma and are notoriously difficult to dissect out. These spinal roots do not maintain a symmetrical horizontal plane that is even close to normal, as demonstrated in Fig. 40–5B. One side of the spinal cord is typically higher than the other, and if not appreciated roots can be transected in the dissection. Fig. 40–5C shows rather simplistically the development of a surgical plane. We start at the interface of the spinal cord and lipoma proximally. The dissection typically goes well until the terminus of the cord (i.e., conus medullaris) is reached; here the roots and lipoma merge. In Fig. 40–5C the artist has shown the horizontal dissection along the cord; an alternate cut is made down through the roots only if these are found to be not functioning and the tether is a very tight one. This cut is very rarely made and is shown here only as
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Closure Technique The technique for closure of a lipomyelomeningocele is one that requires a good deal of care and clear appreciation of the anatomy. The single largest postoperative complication in this group of patients is a CSF leak that persists and leads to infection and meningitis. This added morbidity is detrimental to a patient and should be avoided at all cost. An additional morbidity is a retether of the spinal cord that has occurred in a child because of a lack of appreciation of reconstructing a CSF space around the detethered cord. In all three types of lipomas we attempt to reapproximate the plial ends of the cord. This makes for a tubular structure that provides less surface area to adhere to the overlying fascial and dural repairs. This technique is not always possible in the transitional-type lipoma, but should at least be considered. A true dural closure is rarely possible due to the anatomy of these lesions (i.e., there is no dura present because of nature of the lesion). However, space has
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Figure 40–5 In (A) the surgical dissection of a transitional lipomyelomeningocele has been started. In (B) the axial cross-section of the cord is shown. The eccentricity of the lipoma to the spinal cord is easily appreciated, as is the total lack of normal anatomical planes. In (C) is shown the final resection with an alternate line of dissection used to untether the cord—this can only be done if the roots are found to be nonfunctional by stimulation. This last scenario is rarely done because of the potential loss of neural function. Figure 40–4 Artistic rendition of a caudal-type lipomyelomeningocele. (A,B) A typical cross-section and the total lack of demarcation between roots and lipoma that is so typical. (C) An artificial plane has been developed between the lipoma, cord, and roots. Residual lipoma is left where it incorporates normal functioning roots. (D) Artist’s depiction of a caudal lipoma incorporates the roots and spinal cord. This image demonstrates how difficult it can be to develop surgical planes without injuring the spinal cord. 10.1055/978-1-60406-039-3c040_f004
to be created in which CSF can flow and bathe the repaired structures; this in an effort to reduce retethering. To do this requires positioning of the cord within the spinal canal and the release of any surrounding arachnoid adhesions. A capacious dural sac is constructed with fascia or dural substitute. If done correctly, CSF should freely circulate around the cord and roots. A multilayer closure is done to eliminates any dead space in which CSF can pool. On rare occasions, we will also rotate over the canal the lateral muscle fascia as an additional layer of closure. This is a technically more difficult procedure, but nevertheless a useful one in preventing CSF leaks.
Specialized Instrumentation In this type of surgery, the use of evoked potentials (both motor and sensory) and motor stimulation is helpful in in
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assisting the surgical team in locating nervous structures. The use of loupes and magnification is extremely helpful in differentiating normal from abnormal structures and planes. We frequently borrow cataract knives from our ophthalmic colleagues for microdissection. These knives come in several different shapes and styles and are always very sharp. We have recently begun using the radio frequency current (e.g., Ellman system) for cauterizing tissue. This type of current significantly reduces heat transmitted and hence potential thermal injury and increased necrosis to the normal neural structures.
Postoperative Management Including Possible Complications The child is cared for in the pediatric intensive care unit for a 24 hour postoperative period in a buttocks-up position (i.e., the buttocks higher than the head). Appropriate analgesia is provided to reduce the stress for the child and in particular reduce any undue postoperative movement and Valsalva pressures that might put stress on the repair site. After 24 hours the child is fed by mouth. The child is positioned by the nursing team to lie only on the abdomen for the first 48
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274 Pediatric Neurosurgery hours. Then the patient is allowed to lie on his or her side but not on the back for the next two to three days. We then allow the child to increase his or her gatch so that by day 5 to 6 the child is upright and walking for short periods. No pressure is allowed on the back for the first two weeks after surgery. Restraints and sedation are sometimes needed in the young child to assist in keeping the child appropriately positioned.
Complications The single most dreaded complication is CSF leak and infection. Fortunately this complication is not common, occurring in <15% of cases in most series. It cannot be emphasized enough the attention that must be paid to the closure and
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postoperative positioning of the patient; these are critical in reducing these problems. Risk of injury to the neural structures remains very real in these operations and should be explained in detail to the family. Probably the most common complication seen postoperatively (excluding leak and infection) is a change in bladder patterns. These changes need close monitoring by the urological team, and typically the patient will return to the preoperative status within several weeks, assuming no critical neurological structures have been injured. With careful attention to detail, significant blood loss is rarely a problem in these children. We do, however, routinely offer the family the option of donor-directed blood in the rare case in which a transfusion might be required.
4/11/08 11:32:52 AM
41 Brain Stem Gliomas Darlene A. Lobel and Mark R. Lee
Brain stem gliomas represent ~10 to 20% of pediatric brain tumors, but they are rare in adults. As a group, these tumors have a poor prognosis; they are associated with a 30% 5 year survival rate. However, it has become clear that brain stem gliomas are a heterogeneous group of tumors in regard to biological behavior and surgical accessibility. Certainly, some categories of brain stem gliomas possess a low-grade pathology and have a better prognosis. In general, there are four categories of brain stem tumors including diffuse brain stem gliomas, focal tumors, exophytic tumors, and cervicomedullary tumors. In light of modern imaging and technical advances, many of these tumors, with the exception of diffuse brain stem gliomas, represent surgical challenges that can be overcome. A very important tool in the surgical management of brain stem gliomas is magnetic resonance imaging (MRI). This makes it possible to identify the precise anatomical location of the neoplasm. In conjunction with the clinical picture, MRI allows one to know the pathology of the tumor with
some degree of certainty. Thus, therapeutic decisions, including those regarding the surgical management of brain stem gliomas, can be made based on characteristic MRI. Advances in image-guided surgical techniques and use of intraoperative neurophysiological mapping permit more aggressive tumor resection than had been considered feasible in the past.
Patient Selection Patient selection is vital to the successful surgical treatment of brain stem gliomas. The most rewarding surgical outcomes will be in patients who harbor low-grade tumors that displace rather than infiltrate normal brain stem structures (Fig. 41–1); these include focal or exophytic tumors, and occasionally cervicomedullary tumors. In addition to the tumor classification, patients who are most able to withstand the surgical manipulation of brain stem structures are
Figure 41–1 Pontine tumor causing displacement of normal brain stem structures. 10.1055/978-1-60406-039-3c041_f001
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276 Pediatric Neurosurgery those who have not yet been injured by their tumors; thus, surgery early in the disease course is preferable to surgery late in the disease course. In the subgroup of patients with diffuse brain stem gliomas, surgical intervention plays no role. These patients typically present with a very short history (a duration of weeks) of progressive cranial nerve palsies, gait ataxia, and longtract signs. MRI reveals an expanded brain stem throughout, with diffuse infiltration by neoplastic cells as evidenced by a marked increase in signal on T2-weighted images of the pons and the medulla. Because these tumors diffusely infiltrate normal brain stem structures, resection of any portion of the tumor also involves removal of functional brain stem tissue. These tumors behave quite aggressively, and the patient’s prognosis is dismal. The histology typically is anaplastic astrocytoma or glioblastoma multiforme. Focal brain stem tumors, on the other hand, are amenable to surgical resection, especially those with an exophytic component. Because these tumors are very slow growing, patients typically present with a long history (years) of a mild cranial nerve palsy and occasionally with long-tract signs. MRI reveals a focal tumor that frequently enhances with gadolinium contrast. As noted above, the tumor often has a large exophytic component. The growth pattern of these tumors suggests that they respect anatomical boundaries, and they remain restricted to the “compartment” of the brain stem from which they originated (e.g., in the medulla). These tumors behave in a fairly indolent manner until they reach a critical mass, at which time the clinical course may accelerate. The histology typically is low-grade astrocytoma, juvenile pilocytic astrocytoma, or more rarely ganglioglioma. Focal or exophytic brain stem gliomas typically displace and compress normal brain stem structures. This characteristic, coupled with their low-grade pathology and slow growth, can make these lesions amenable to complete surgical resection and possible cure.
Preoperative Preparation All patients should undergo preoperative MRI scanning with contrast enhancement. Not only does this provide for anatomical localization of the tumor and its relationship with normal structures, it also provides for a baseline study in which to judge the efficacy of the operation. Use of an intraoperative image-guided system should be considered, particularly for resection of tumors that are not exophytic. Furthermore, these frameless stereotactic techniques facilitate more complete tumor resection and aid in avoiding injury to brain stem nuclei. Unless they are located in the midbrain, it is uncommon for patients with brain stem gliomas to suffer from hydrocephalus, and therefore cerebrospinal fluid (CSF) diversion is rarely an issue. Routine laboratory studies including a complete blood count with differential, prothrombin time, and partial thromboplastin time are obtained. The patient is typed and cross-matched for two units of packed red blood cells. The patient’s hair is shampooed with antiseptic soap the night before surgery. Patients receive 10 mg of dexamethasone intravenously immediately prior to surgery. Prophylactic anti-
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biotics (usually a first-generation cephalosporin) are given the morning of surgery, early enough to obtain a therapeutic tissue level at the time of incision.
Anesthesia The patient is induced with intravenous Pentothal (thiopental) and intubated in the supine position. As mentioned above, intraoperative neurophysiological mapping and monitoring is a useful adjunct in these procedures. Volatile inhalation anesthetics cause depression of evoked potentials and prolonged latencies. Therefore, patients are generally maintained with inhalation anesthesia consisting of isofluorane at 0.3 to 0.5 MAC; this is occasionally supplemented with nitrous oxide. Supplemental intravenous remifentanyl, a short-acting narcotic, is also administered. An intra-arterial line is placed to monitor blood pressure and blood gas levels. There is no need for hyperventilation because early in the course of the procedure, the cisterna magna is opened with release of CSF and resulting relaxation of the posterior fossa. Patients undergoing brain stem surgery require strict hemodynamic monitoring. It is not unusual to note wide fluctuations in blood pressure and heart rate during tumor dissection and removal. Typically, the patient will become either hypertensive or bradycardic, and it is essential that the anesthesiologist be prepared for pharmacological intervention if necessary. If hemodynamic changes are encountered, tumor dissection and manipulation should be halted temporarily. The hemodynamic instability usually selfcorrects, allowing for the procedure to continue.
Operative Procedure Patient Positioning The patient is placed in a pinned headholder (either Mayfield [Schaerer Mayfield, Cincinatti, Ohio] or Sugita) and is turned to the prone position onto two gel chest rolls. The arms are tucked on the sides under the sheets. The headholder is attached to the operative table with the neck moderately flexed and the chin pulled posteriorly. This gives excellent exposure of the suboccipital region (Fig. 41–2A). The operating table is placed in reverse Trendelenburg’s position until the posterior neck and inion are parallel to the ground. In children <3 years of age, a horseshoe-shaped headholder is used instead of a pinned headholder. In this case, care is taken to protect the eyes. Unfortunately, optimal exposure of the suboccipital region is difficult without a pinned headholder. An alternative method of positioning patients for this operation is the sitting position. However, not only is there a risk for air embolism, there are also major concerns regarding adequate cerebral perfusion during times of hemodynamic instability brought on during the tumor surgery. Therefore, we do not advise the sitting position for brain stem glioma surgery.
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Figure 41–2 (A) Patient positioning in Mayfield headholder. (B) Dotted lines indicate skin incision extending from above the inion to the C-2 spinous process. (C) Paramedian bur holes and heart-shaped craniotomy extending to the foramen magnum. 10.1055/978-1-60406-039-3c041_f002
Incision and Opening We typically do not shave the patient’s hair but plan for the incision in a midline part. If a patient’s hair is too short to comb, we will shave a small strip. The incision line is infiltrated with 0.25% Marcaine (bupivacaine ) with 1:100,000 epinephrine. After the usual preparation and draping, an incision is made from several centimeters above the inion to the palpated spinous process of C-2 or C-3, and it is taken down to the pericranium of the occiput and the fascia of the nuchal muscles (Fig. 41–2B). The fascia is cut in the midline with Bovie current and taken down to the cranium, the arch of C-1, and the spinous process of C-2. Care must be taken when cutting down on the midline of the arch of C-1 because this can be cartilaginous, especially in younger children. The nuchal muscles are dissected in a subperiosteal manner utilizing Bovie current on the suboccipital cranium and a combination of blunt and sharp dissection on the foramen magnum and the arch of C-1. There is no need to perform further muscle dissection on C-2 unless a laminectomy is required for resection of the cervical portion of some brain stem gliomas. Two bur holes are fashioned on either side of the midline just below the level of the inion. Typically, an air-powered drill with an “acorn-shaped” bit is utilized. The bone between the two bur holes is then drilled down, again with the acorn bit, to create one larger oval-shaped bur hole. It should be remembered that a “keel” of bone very commonly exists on the midline in the posterior fossa. Therefore, when drilling between these two bur holes, one must be aware that the thickness of bone will vary widely, and violation of the dura could occur if care is not taken. After exposure of the dura, the bur hole is enlarged with a curette and the dura is widely stripped with a no. 3 Penfield. Attention is
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then turned to the foramen magnum where the periosteum, which melds into the outer leaf of dura of the posterior fossa, is cut widely utilizing a curette. A small amount of bleeding may be encountered at this point from the marginal sinus, which can be easily controlled with Gelfoam soaked in thrombin. The dura is again widely stripped at the foramen magnum with a no. 3 Penfield. A bone flap is then created utilizing a craniotome. Bone cuts are made from the midline bur holes, bringing them laterally and then inferiorly and diagonally toward the foramen magnum to make a heart-shaped craniotomy (Fig. 41–2C). The bone flap is elevated with a no. 3 Penfield. There is no need to expose the transverse sinus. The lateral edges of the posterior rim of the foramen magnum are removed using rongeurs. The posterior arch of C-1 is not removed except in cases where the brain stem tumor extends into the cervical spinal cord. After epidural hemostasis is obtained, attention is turned to the dural opening. A small dural opening is made with a no. 11 blade at one of the upper corners of the craniotomy. Using Metzenbaum scissors, the dural opening is continued diagonally to the midline at the craniocervical junction. Care is taken not to cross the midline occipital sinus or the usually present marginal sinus. This is repeated on the opposite side. Two LigaClips (Ethicon, Somerville, NJ) are placed across the occipital sinus, and the sinus is divided at the base of the two diagonals. If the marginal sinus is significant, two LigaClips are placed across it on the midline. The dural opening is then completed, bringing a final limb inferiorly on the midline in the upper cervical region. The dural opening appears as a “Y” (Fig. 41–3). The three corners are sutured and tacked laterally and superiorly (Fig. 41–4A). If not already violated during the dural opening, the cisterna magna should be opened at this time to allow for release of CSF and relaxation of the posterior fossa.
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Figure 41–3 Dotted lines indicate dural incision in a Y-shaped fashion. 10.1055/978-1-60406-039-3c041_f003
The degree and method of magnification during the remainder of the operation depend upon the individual surgeon. We elect to bring in the operating microscope at this time and perform the remainder of the operation under microscopic illumination.
as the vermis is split (Fig. 41–4B). With dorsally exophytic brain stem tumors, the tumor is usually encountered first, and the floor of the fourth ventricle will not be identified until the superior pole of the tumor has been breached.
Tumor Resection Tumor Exposure To provide adequate exposure of the fourth ventricle, the inferior half of the cerebellar vermis is split. Initially, the retractors from the system of choice (we use either the Sugita or the Greenberg system [Codman & Shurtleff, Inc., Rayham, Massachusetts]) are placed to split the tonsils and provide good exposure of the inferior vermis. The bipolar cautery is then utilized to coagulate the pia and veins on the surface of the vermis. The coagulated surface is then cut with microscissors. The corticectomy is created using bipolar coagulation and suction. Care is taken to avoid excess dissection of the vermis to avoid the potential postoperative complication of cerebellar mutism. With completely intrinsic brain stem tumors, the floor of the fourth ventricle is frequently elevated with partial or complete obliteration of the fourth ventricle. Therefore, care must be taken when removing tissue of the inferior vermis because the floor of the fourth ventricle can be inadvertently violated. To help guard against this, we typically split the vermis from a caudal to a cranial direction after retracting the cerebellar tonsils. This allows direct visualization of the dorsal surface of the upper cervical spinal cord, which can be followed to the obex and the floor of the fourth ventricle
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Focal intrinsic brain stem tumors are completely intra-axial; however, a portion of the tumor will usually have an abnormal-appearing layer of ependyma over it where it broaches the floor of the fourth ventricle. This can be readily identified. This area can be coagulated utilizing bipolarity and entered using suction, after which tissue is removed for pathological examination. An ultrasonic aspirator is then used for the majority of the tumor removal. These tumors are typically quite soft and suckable; therefore, it is advisable that the aspirator settings of low amplitude and suction (50%) be used. Alternatively, an Nd:YAG (neodymium:yttrium-aluminum-garnet) contact laser, which provides precise cutting and coagulation, may be used for tumor resection, and is particularly useful at the tumor margins. Typically, these lesions will displace brain stem nuclei superiorly, laterally, or inferiorly. Although displaced, the important nuclei will be intimately associated with the tumor margins, and therefore, it is vitally important that tumor resection proceed from the inside out (internal resection). Tumor margins are recognized by a change in the way the tumor tissue responds to suction. The area where there is little residual tumor becomes “floppy,” as if there remains a fragile capsule. The difference in tissue consistency between
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Figure 41–4 (A) Dural leaflets reflected with tenting sutures. (B) Divided inferior cerebellar vermis exposing tumor; retractors on cerebellar tonsils. 10.1055/978-1-60406-039-3c041_f004
tumor and brain stem causes tumor tissue to pull away from brain stem tissue under light suction when there is little tumor bulk left at a specific margin. When this is encountered, the remainder of the tumor removal should be accomplished with light suction and bipolar coagulation. Once white matter is encountered, tumor removal is completed at this margin (Fig. 41–5). Significant bleeding is uncommon and is usually easily controlled. One should be loath to use bipolar coagulation in the tumor bed unless a specific bleeding vessel can be identified, because this can easily injure normal brain stem tissue. Usually, hemostasis is obtained with gentle, warm saline irrigation, and if necessary with application of microfibrillary collagen and thrombin. With dorsally exophytic brain stem tumors, the tumor bulk is outside the brain stem. In fact, when first reviewing imaging studies, it is common to believe that one is dealing with a cerebellar tumor until invasion of the brain stem via the floor of the fourth ventricle or the inferior and middle cerebellar peduncles is recognized. After opening the posterior fossa as described above, we usually perform a corticectomy of the inferior vermis or over the dome of the mass of exophytic tumor coming closest to the cerebellar cortex as defined by intraoperative ultrasound or image guidance. Upon encountering the tumor, we take several specimens for pathological examination and then proceed with surgically defining the tumor. Lateral, inferior, and superior margins of the tumor must be identified and dissected from the surrounding cerebellar tissue prior to tumor debulking with the aspirator. Continuously alternating between defining tumor borders and removing tumor tissue allows
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one to safely proceed with tumor resection without making inadvertent entry into the brain stem. Neurophysiological monitoring allows one to proceed more aggressively with tumor resection while avoiding injury to vital brain stem structures. Although these tumors can be very large, with adequate debulking, the superior pole of the tumor can be identified and the floor of the fourth ventricle visualized. At this point, it is prudent to place a cottonoid patty over the floor of the upper fourth ventricle to guard against injury to the facial colliculi and to block any blood from entering the aqueduct. Working over the dome of the debulked and more mobile tumor, the tumor can begin to be amputated at the level of the floor of the fourth ventricle, bringing this dissection inferiorly until the tumor has been completely mobilized and removed. This allows removal of the tumor tissue while maintaining the orientation of the normal brain stem tissue. It is extremely important that the small amount of residual tumor tissue that may invade the brain stem is not chased below the level of the floor of the fourth ventricle, as this can lead to permanent injury of the motor nuclei of the lower cranial nerves.
Closure At completion of the tumor resection, the tumor bed is irrigated with warm saline, and hemostasis is ensured. The dura is closed with running, locking 4–0 nylon sutures, and the bone flap is secured with cranial miniplates or 2–0 silk sutures. A few 2–0 Vicryl sutures are placed in the muscle to decrease the amount of “dead” space, followed with in-
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Figure 41–5 View of brain stem after tumor resection is complete. 10.1055/978-1-60406-039-3c041_f005
terrupted 3–0 Vicryl sutures for the fascia and the galea or subcutaneous tissue. The skin is closed with a running 3–0 nylon suture. No drains are placed.
Postoperative Management Including Possible Complications Patients with lesions restricted to the pons are extubated in the operating room. They are usually managed in the intensive care unit for ~24 hours. This is primarily for close observation and monitoring. At this point, they are most often fully responsive and able to assist in their own care; they are then transferred to the regular ward. Physical and occupational therapy is often begun on the third postoperative day to assist in their recovery. Dexamethasone is usually tapered over 7 to 10 days. Patients with lesions involving the medulla remain intubated for 72 hours. Sedation may be necessary to keep them comfortable. Continued intubation and ventilation are precautions against the loss of respiratory drive suffered by some patients 24 to 48 hours postoperatively. This is probably related to edema of the medulla and leads to hypoventiliation, hypoxia, and hypercarbia. Patients who do well are usually transferred to the regular ward 24 hours after extubation. Physical and occupational therapy is begun at
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this time. If they have an adequate gag reflex, they are fed orally. If not, a nasal feeding tube is placed temporarily until it is no longer needed. Most patients recover their ability to swallow quickly and do not require a percutaneous gastrostomy tube. Patients are maintained on high-dose steroids (6 to 10 mg dexamethasone every 6 hours depending on their weight) for 3 days, and then steroids are tapered over 7 to 10 days. Skin sutures are usually removed 7 to 10 days after surgery, and most patients are discharged at this time. Some patients may require inpatient rehabilitation and are usually transferred to an appropriate facility at that time. Acknowledgments This chapter is a revision of the chapter, “Surgical Treatment of Brainstem Gliomas” by Mark R. Lee, M.D., and Michael Cowan, M.D. The chapter appeared in the Neurosurgical Operative Atlas, Volume # 1, edited by Setti S. Rengachary and Robert H. Wilkins. The Neurosurgical Operative Atlas was published by the American Association of Neurological Surgeons (AANS) from 1991 to 2000. We would like to acknowledge and thank Michael Cowan, M.D., for his help and efforts on the original chapter published in the first edition of this work. We also gratefully acknowledge the contribution of Andy Rekito, M.S., for providing the illustrations in this chapter.
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42 Posterior Fossa Decompression without Dural Opening for the Treatment of Chiari I Malformation Jonathan D. Sherman, Jeffrey J. Larson, and Kerry R. Crone The treatment of patients with Chiari I malformation traditionally consists of posterior fossa decompression, with or without cervical laminectomy, combined with duraplasty. Posterior fossa decompression has been developed to relieve impaction created by tonsillar herniation and to ameliorate regression of symptoms. Modifications of this treatment include fourth-ventricle-to-subarachnoid shunting to maintain free egress of cerebrospinal fluid (CSF), as well as plugging of the obex to prevent syrinx expansion. However, it is unclear whether the syrinx is in direct communication with the subarachnoid space. We have adopted the use of intraoperative ultrasound to evaluate decompression of the foramen magnum and the need for duraplasty in children with Chiari I malformation. Our treatment for patients with Chiari I malformation is based on the theory that posterior fossa decompression without duraplasty is adequate if CSF flow can be established.
Patient Selection Children with Chiari I malformation are candidates for posterior fossa decompression. Contraindications to this treatment include the presence of any intradural pathology that requires dural opening, such as arachnoid scarring or sequestrations. Ultrasound may be performed in such patients; however, intradural exploration is still required. In patients with medical conditions that preclude surgery (e.g., bleeding disorders or cardiac anomalies), this procedure would be contraindicated until treatment is initiated.
Preoperative Preparation Magnetic resonance imaging (MRI) of the craniocervical junction is obtained preoperatively to determine the extent of the Chiari I malformation. Sagittal and axial T2-weighted images are important to visualize the CSF spaces ventral and dorsal to the cervicomedullary junction. MRI of the spine is helpful to demonstrate the presence and extent of a syrinx, especially in patients with signs and symptoms suggestive of a syrinx. Preoperative evaluation should include complete
blood cell count, electrolyte profile, coagulation studies, and blood type and crossmatch. Prior to being placed on the operating table, the patient is intubated, an inhalation anesthetic is administered, and intravenous antibiotics are completely infused. Prior to patient positioning, cardiac monitor leads, intravenous access, pulse oximetry, and an arterial line or a blood pressure cuff are placed.
Special Equipment In addition to the standard surgical instrumentation needed for posterior fossa decompression, intraoperative ultrasound equipment is necessary. Sagittal and axial imaging of the cervicomedullary junction is obtained intraoperatively to evaluate the adequacy of decompression. A 7 MHz transducer (actual head size 1.2 ⫻ 2.2 cm) is introduced into the surgical bed, which has been irrigated with 0.9% sodium chloride.
Operative Procedure In the surgical suite (Fig. 42–1) the patient is positioned prone, with the neck slightly flexed. The head is placed on a Mayfield headrest (Integra, Plaisboro, New Jersey) or in three-point fixation. The shoulders are pulled down to expose the suboccipital region and the posterior cervical spine from C-1 to C-6. A midline skin incision is made from the inion to the level of C-3. The paraspinous fascia is dissected at the avascular linea albae and is retracted laterally to expose the occiput and the upper cervical laminae. Using a high-speed drill, the surgeon thins the suboccipital bone. Bone rongeurs are used to expose the posterior fossa and spinal dura. Bony decompression, which is carried laterally to the occipital condyles, provides lateral decompression of the cervicomedullary junction. An upper cervical laminectomy is performed to accommodate the extent of the descended cerebellar tonsils. Laminectomy is carried to the lateral aspect of the canal (Fig. 42–2A). After completing the bony decompression of the suboccipital and cervical canal, the surgeon identifies a transverse
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Figure 42–1 Superior view of the operating room layout during posterior fossa decompression. The surgeon stands at the patient’s left side, and the patient is prone. The assistant and the scrub nurse are on the patient’s
right side. The ultrasound equipment is behind the assistant, allowing the surgeon a clear view of the image while ultrasonography is performed. (Printed with permission from Mayfield Clinic, Cincinnati, OH)
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dural band at the level of the cervicomedullary junction. This dural band, which consists of thickened dura and periosteum of the bony foramen magnum, must be incised to achieve decompression (Fig. 42–2B). The band is divided with a no. 15 blade, being careful that the underlying dura is not incised. The thickened band is then peeled away from the dura using forceps (Fig. 42–2C). Ultrasound images are obtained to reveal the level of tonsillar herniation. Sufficient decompression has been achieved if CSF can be identified dorsal to the tonsils and cervicomedullary junction by ultrasound on sagittal and axial views and if tonsillar “pistoning” (i.e., pulsatile rostral-caudal movement of the tonsils with little anteroposterior pulsation (Fig. 42–3A) is absent. Ultrasonography is used to determine whether there is adequate CSF dorsal to the cervicomedullary junction and tonsils. Movement of the tonsils is also assessed. If the CSF spaces are small (i.e., less than 2 mm between the tonsils and dura (Fig. 42–3B) or if there is pistoning, then duraplasty is performed using a graft of periosteum or dural
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substitute (Fig. 42–3C). An incision is made in the dura from the top of the bony decompression to the bottom. The dural opening is made lateral to the midline on one side, above the level of the foramen magnum to avoid opening the occipital sinus. To allow sufficient space inside the dura for adequate decompression, a graft is sewn in place using 5–0 Prolene sutures, running a simple suture to obtain a watertight closure. Intradural exploration and coagulation of the cerebellar tonsils elevate the tonsils above the level of the foramen magnum. Release of an arachnoid membrane, which is frequently found overlying the fourth ventricle and foramen of Magendie, is also performed. After adequate decompression is obtained, a Valsalva maneuver is performed to ensure, via ultrasonography, that foramen magnum obstruction by further tonsillar descent does not occur and to verify that no holes or defects were created in the dura. The paraspinous musculature is reapproximated using widely spaced, simple, interrupted 3–0
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A
B
C Figure 42–2 (A) The posterior fossa and spinal dura are exposed following a suboccipital craniectomy and C-1 laminectomy. Note the thickened transverse fibrous band at the level of the foramen magnum, still compressing the dura and underlying tonsils and brain stem. (B) A right-angle dissector is inserted between the fibrous band and the dura. 10.1055/978-1-60406-039-3c042_f002
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The fibrous band is then incised to prevent cutting the dura or marginal sinus. (C) The fibrous band is peeled from the dura after incision, thus providing further decompression of the foramen magnum. (Reprinted with permission from Mayfield Clinic, Cincinnati, OH)
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B
A
C
Figure 42–3 (A) Illustration of tonsillar pistoning (arrow) or the rostral-caudal movement of the tonsils that occurs in Chiari malformation during systole-diastole pulsations. Loss of this pistoning movement, combined with adequate cerebrospinal fluid (CSF) space between the tonsils and the dura, indicates sufficient decompression of the foramen magnum. (B) Ultrasonic image demonstrating adequate decompression
of the foramen magnum. Note the 2 mm of CSF space between the cerebellar tonsils and the dura posteriorly. (C) In cases in which adequate decompression cannot be obtained without dural opening, a midline dural incision, placement of a dural graft, and duraplasty are used to widen the foramen magnum. (Reprinted with permission from Mayfield Clinic, Cincinnati, OH)
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Vicryl sutures. The overlying cervical fascia is tightly closed, using simple, interrupted 3–0 Vicryl sutures. The skin is closed in the usual fashion.
Postoperative Management Including Possible Complications The patient remains in a high-acuity care setting for 24 hours following surgery. Activity is increased progressively. The patient is discharged when dietary intake is adequate and he or she is ambulating well.
Follow-up Care Approximately 6 weeks after the operation, MRI is performed to evaluate the CSF space around the tonsils and cervicomedullary junction. We have used cine-MRI to assess CSF flow. If the patient has an associated syrinx, repeat MRI at the appropriate spinal level is performed to monitor the size. In our experience, a decrease in the size of the syrinx can be observed by 4 to 6 months postoperatively.
Complications Most postoperative complications in posterior fossa decompression are a result of duraplasty. Frequently encountered complications such as CSF leakage, meningitis, hemor-
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rhage, and arachnoiditis can be prevented when duraplasty is avoided. In one patient, a portion of the cerebellar tonsil herniated through a small hole that occurred in the dura during dural thinning. This caused infarction of the herniated portion of tonsil. After presenting with recurrent, intractable posterior headaches, the patient underwent duraplasty. Her symptoms resolved following this second procedure. We have subsequently discontinued the practice of dural thinning and release the fibrous band only at the level of the foramen magnum, as described.
Conclusion We have found that posterior fossa decompression without duraplasty can adequately treat patients with Chiari I malformation. Intraoperative ultrasound is a useful adjunct to evaluate adequate decompression by assessing the amount of CSF around the descended tonsils in the obstructed foramen magnum. Avoiding duraplasty has decreased the incidence of postoperative complications. The use of this procedure without duraplasty has been limited to the pediatric population, but it may also prove effective in adults. Further studies are needed to assess the amount of CSF necessary for adequate decompression, as well as to determine the long-term outcomes in patients in whom decompression is performed with and without dural opening.
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43 Metopic Synostosis Kant Y. K. Lin, John A. Jane Jr., and John A. Jane Sr.
Metopic craniosynostosis is defined as the premature fusion and subsequent arrest of growth at the metopic cranial suture. It is one of the less common forms of craniosynostosis, accounting for an estimated 5 to 10% of isolated nonsyndromic craniosynostoses. Depending on the timing and extent of the premature sutural closure, metopic synostosis can present along a spectrum of mild to severe manifestations. In a child with late closure, when the majority of skull growth has already occurred, this can appear as an isolated midline forehead ridge that is often more palpable than visible in an otherwise normal-shaped head. Earlier closure, however, can result in a child having a grossly triangularshaped skull, termed trigonocephaly, with a keel-shaped frontal bone protuberance often accompanied by orbital hypotelorbitism, ethmoidal hypoplasia, and severe bitemporal narrowing. Compensatory posterior growth at the coronal and lambdoid sutures, as well as lateral growth at the sagittal suture, leads to widening in the parietal regions, which serves to accentuate the overall triangular or pear shape of the skull. Metopic craniosynostosis, like other forms of premature suture closure, may be associated with elevated generalized intracranial pressure (ICP). The exact incidence of this occurring is not clear; it is thought to be ~10% by some estimates, but it is known that the likelihood of this occurring is significantly increased if other sutures are concomitantly involved, as in kleeblattschädel. The phenomenon of a localized elevated ICP of the anterior cranial fossa affecting primarily the frontal lobes of the brain is also of concern. The incidence of cognitive impairment and behavioral disturbance has been noted to be increased in a significant percentage of patients with metopic synostosis and may be either the result of increased pressure on the frontal lobes or the result of associated underlying midline brain abnormalities such as holoprosencephaly or agenesis of the corpus callosum.
Patient Selection Diagnosis is based on the characteristic medical history and physical examination. Additional confirmation can be obtained from computed tomography (CT) of the skull, whereby individual image slices can be used to quantify the degree of head-shape abnormalities by comparing key
measurements to age-matched skull images of nonaffected children. Hypotelorbitism can be defined by measuring the intercanthal distance and is also confirmed by CT. A thorough ophthalmologic examination is indicated, and funduscopic evaluation can often detect, albeit late, manifestations of elevated ICP. In addition, these children should be evaluated by a geneticist, looking for other associated congenital anomalies as well as familial patterns of inheritance of this condition. A pediatric developmentalist should examine the patient to document for evidence of neuroor psychodevelopmental delay. It has been recognized that mental impairment in children with metopic synostosis is much more likely when the condition is associated with other intracranial anomalies.
Indications and Timing of Surgery The main indications for the surgical correction of this condition are to improve the overall appearance of the skull, to improve any associated facial deformities, and to potentially relieve possible intracranial hypertension or any localized pressure on the frontal lobes of the brain. The goal of cranial vault surgery is to provide adequate skull volume to relieve the elevated ICP and to accommodate future brain growth and expansion. Diagnosis of intracranial hypertension can be difficult and is based on “soft” findings such as cerebral markings seen on the inner table of the calvaria (copperbeaten appearance) by x-ray, or late funduscopic changes seen by slit lamp examination. On occasion, a monitoring bolt can be utilized to accurately record pressures intracranially, but this is generally reserved for those cases in which the child has symptoms suggestive of intracranial hypertension and a decision to operate to relieve that pressure must be made urgently. Although subject to some controversy as to the exact timing, most surgeons would agree that surgery is best performed before the child has reached the age of 1 year, and some would argue as early as 2 months of age. The authors’ preferred age for surgery is 6 months. Because the volume of the brain almost triples in the first year of life, it would seem prudent to allow the intracranial cavity to accommodate this rapid growth through early surgery. This correction should certainly be performed before brain damage has occurred; often, subsequent growth of the brain can be utilized as an additional factor to help maintain the improved skull shape
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43 following surgical release of the fused suture. Early correction also spares the child emotional or psychological trauma over his/her appearance, before the child reaches the age of self-awareness (5 years old or younger).
Preoperative Preparation Once the decision has been made to proceed with surgery, a preoperative workup consisting of routine blood tests, including a complete blood cell count, electrolyte panel, and a partial thromboplastin time and prothrombin time, are performed. Because of the potential for significant blood loss, a type and screen are obtained and compatible donors among relatives are encouraged to donate for donor-directed intraand perioperative transfusions. The child is brought to the hospital on the day of surgery having been kept nil per os for 4 hours prior to the anticipated start time for surgery. At least two large-bore (≥20 gauge) intravenous lines are required for access due to the potential for significant blood loss or fluid shifts during surgery. An arterial and a central line are also helpful to monitor the total body intravascular volume for both operative and postoperative fluid management. A Foley catheter is useful to record urinary output, and a thermistor is used to record core body temperature. A Doppler monitor is placed over the heart to monitor blood flow and is used to detect the possibility of unanticipated intraoperative air embolism. Steroids and anticonvulsants are not routinely used. Prophylactic antibiotics are given just prior to the incision. In young children, the hair is clipped to allow the surgeon full visualization of the degree of the skull deformity, in order that the surgical correction can be tailored accordingly. This also helps facilitate the scalp closure and postoperative wound care by the nursing staff and the parents. Once the intraoral endotracheal intubation has been performed, we have found it helpful to secure the tube with either a circummandibular or a circumdental wire, thus obviating the need for taping and allowing full access to the face during surgery. Temporary tarsorrhaphy sutures are also placed for intraoperative corneal protection.
Operative Procedure Positioning The patient is placed in a supine position on the operating table with the head resting in slight extension in a Mayfield headring (Schaerer Mayfield, Cincinatti, Ohio). The ring is reinforced with additional soft padding to prevent excessive pressure over bony prominences during the lengthy procedure. The scalp and face are prepped with Betadine (povidone-iodine) solution, with emphasis placed on scrubbing the external auditory canals, which tend to colonize with bacteria. The head, face, and neck are then draped to the clavicles, and skin staples are used to secure the drapes. A 180 degree access to the head and facial region is required, and the surgical table is rotated so that the anesthesiologist is positioned at the patient’s side at the foot level. The nurs-
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ing staff and all instrumentation, which has been placed on a single large table, is positioned opposite the anesthesiologist. A smaller Mayo stand is positioned over the patient’s abdomen, and only those instruments most currently in use are kept for ready access.
Skin Incision and Flap Elevation A bicoronal incision in the form of a gentle wavy line is performed, extending from just behind one ear across to the opposite side. Care is taken to make the incision posterior to the anterior hairline, yet forward enough to allow for access to the orbital region once the scalp flap is dissected. The scalp flap is elevated anteriorly down to the level of the supraorbital rim. The supraorbital neurovascular bundle is preserved and is left attached to the anterior scalp flap. Dissection is then extended laterally down each lateral orbital rim detaching the lateral canthi to the junction with the inferior orbital rim, and medially up to, but not detaching, the insertion of the medial canthal tendons. The nasolacrimal apparati are also carefully preserved. The nasion is exposed during this part of the dissection as well. Inferolaterally, the anterior aspect of the maxilla, the malar eminence, and the anterior aspect of the zygomatic arch are also exposed. The temporalis muscles are elevated off their insertions and are also left attached to the undersurface of the scalp flap, thus allowing access to the infratemporal hollow. The temporal and sphenoid bones are exposed from the lateral orbital rim close to the junction where the zygomatic arch meets the posterior temporal bone. This area will allow for the formation of a tenon extension on the temporal bone, once the orbital osteotomies are performed.
Craniotomy and Craniofacial Reconstruction A bifrontal craniotomy is performed, and the entire length of the involved suture, from nasion to vertex, is included in the removed bone segment (Fig. 43–1). Retraction of the frontal and temporal lobes of the brain is then performed, taking care to remain anterior to each olfactory bulb. Threequarter orbital osteotomies are completed, extending across the orbital roof (Fig. 43–2), superior aspect of the medial orbital wall, lateral orbital wall, and the lateral aspect of the orbital floor into the inferior orbital fissure. Tenon extensions are made, extending laterally into the sphenoid and temporal bones (Fig. 43–3). This forms a single orbital unit that is removed in its entirety and reshaped. Typically, the underside of the fused suture will have formed a thickened bone crest that is burred down to allow for reshaping. A new bend is made at the junction of the lateral orbital rim and the tenon extensions into the temporal bone using Tessier bone benders (Lorenz Surgical, Jacksonville, Florida) (Fig. 43–3). Preliminary burring of the inner cortex of the bone in these areas will facilitate the bending of the bone. This results in an advancement laterally that ameliorates the temporal narrowing seen in trigonocephaly. As part of the reshaping, the orbital unit is frequently split vertically in the midline to help correct the hypotelorbitism. A gap is created and filled with a full-thickness interposi-
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Figure 43–1 Metopic craniosynostosis. Characteristic skull morphology seen in patients with metopic craniosynostosis leading to trigonocephaly. Early metopic fusion causes restricted growth of the forehead with varying degrees of hypotelorism, recession of the lateral orbital rims, and bitemporal narrowing. Compensatory growth also occurs at the coronal and sagittal sutures (arrows indicate locations of compensatory growth), which accentuate the narrow appearance of the forehead. 10.1055/978-1-60406-039c043_f001
tional cranial bone graft harvested from the frontal bone (Fig. 43–4). Additionally, in more severe cases, an attempt to further correct the facial deformity is made by performing an osteotomy in the midline at the level of the frontonasal junction, which is extended inferiorly ~1.5 to 2 cm into the nasal bone. An additional cranial bone graft is then wedged into the superior aspect of this osteotomy site, which further increases the bony intercanthal distance. The recontoured orbital bony unit is then returned to its orthotopic position; it is secured at the lateral orbital rims with interosseous wires just below the level of the zygomaticofrontal suture to the intact inferior orbital rim, and at the tenon extensions (where the majority of the advancement was performed) with absorbable microplate and screw fixation. A thicker (2.0 mm) plate is recommended in this area to support the greatest amount of advancement that is located in this area, to prevent any future tendency for relapse. Once this is accomplished, additional craniotomies of the squamosal portion of the temporal bones are performed in a barrel-stave-like fashion and outfractured to further increase the bitemporal width. The previously removed anterior cranial vault piece is reshaped using a combination of Tessier bone benders and burring of the inner table as well as the protuberant outer table keel at the site of the fused suture. This then creates an appropriate anterior cranial vault volume and forehead shape. These bone segments are secured in place using only absorbable
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Figure 43–2 Craniotomy and orbital osteotomies. The bifrontal craniotomy is turned 180 degrees as part of the correction (as indicated by arrows). Dotted lines indicate the location of the orbital osteotomies. 10.1055/978-1-60406-039c043_f002
sutures such as 2–0 Vicryl. To prevent early relapse of the deformity, we believe that plate-and-screw fixation should be used judiciously and only in those areas where significant postoperative pressure can be expected. We have found that lateral canthopexies are not necessary prior to the final closure.
Closure Technique The operative field is copiously irrigated to remove all nonviable debris and bone dust that could act as a nidus for future infection. Because the temporalis muscles were never detached from the overlying scalp flap, there is no need to reattach the muscle to its insertion, as it will naturally return to its proper position as the scalp flap is brought posteriorly. The scalp flap is reapproximated and closed in a two-layer fashion with buried absorbable sutures in the subgaleal plane, and absorbable sutures (4–0 Monocryl or 5–0 fast absorbing plain gut) on the skin. A subgaleal drain is not placed to prevent a siphoning effect of any occult cerebrospinal fluid (CSF) leak that may occur via small rents in the dura that may have occurred during the craniotomies. Our impression is also that the drains increased our postoperative transfusion rates. The trade-off is a greater degree of postoperative swelling. A snug but nonconstricting dressing using a sterile surgical towel wrapped as a turban is placed
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Figure 43–4 Cranial vault reconstruction. The bifrontal craniotomy is reshaped to create a more rounded forehead prior to reattachment to the parietal bone and supraorbital rims with absorbable sutures. The reshaped orbital visor is advanced and reattached to the parietal bone using absorbable miniplates. Absorbable sutures are placed elsewhere to bolster the reconstruction. Barrel-stave-like osteotomies are performed in the parietal and squamous portions of the temporal bone to provide further recontouring. 10.1055/978-1-60406-039c043_f004
Figure 43–3 Orbital rim reconstruction. The orbital visor piece is burred and sectioned at the fused suture, an interpositional bone graft is added, and the entire piece is reconstructed with absorbable fixation plates and screws. The lateral section of the visor (arrow) is recurved using Tessier bone benders. 10.1055/978-1-60406-039c043_f003
over the entire head, and the head is kept elevated at all times. The tarsorrhaphy sutures and the wire around the endotracheal tube are then removed.
Specialized Instrumentation A significant advance in instrumentation for pediatric craniofacial surgery occurred with the introduction of absorbable plate-and-screw fixation hardware. These new biomaterials consisting of polymers of polylactic acids are designed to be totally absorbed within 9 to 15 months following implantation. Studies have confirmed that they have tensile strength properties comparable to previously used metallic hardware at the time of their initial use, which allows for the same
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adaptability when used in three-dimensional calvarial reconstruction. Due to the relatively long retention lifespan of the fixation hardware, the reconfigured and repositioned bone segments can heal with additional support from the plates and screws. Any concern about future translocation of the hardware or restriction of further craniofacial growth is obviated because of predictable absorption of the hardware. High-speed drill and saw systems have made the surgery technically easier.
Postoperative Management Including Possible Complications Immediate postoperative care is given in the pediatric intensive care unit. Vital signs and central venous pressures are monitored and laboratory values are obtained for review of evidence of hypovolemia and blood loss. Depending on the degree of blood deficit, blood transfusions are frequently necessary and the concomitant replacement of coagulation factors may be required. Appropriate dosages of analgesia with morphine sulfate are given intravenously to keep the patient comfortable. The child is positioned on his/her back in bed to keep pressure off the forehead and orbits, and the head is elevated at 30 degrees to prevent excessive postoperative swelling. As a result of the periorbital manipulations, the eyelids commonly swell shut within 24 hours following
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290 Pediatric Neurosurgery surgery. This can cause anxiety for both the parents and the child, and reassurance must be given that the majority of the swelling will resolve in 3 to 4 days. In most instances, the child is ready for transfer to the regular ward within 24 to 48 hours. Usually, the child will run a slightly elevated temperature between 38°C and 39°C at day 3 or 4 following surgery. A routine fever workup is performed, but only rarely is the fever caused by infection. The child is considered stable for discharge from the hospital once he or she is tolerating a regular diet and eyelid swelling has resolved enough to permit eye opening. A follow-up visit is arranged for 1 week after hospital discharge.
Complications Early postoperative complications arise from intraoperative or perioperative blood loss, which can be compounded by inadequate blood replacement. Tears in the sagittal sinus during the craniotomy can have immediately devastating consequences and must undergo repair quickly. Meticulous attention must be directed when looking for possible tears
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in the dura mater, which can lead to a persistent CSF leak. Once recognized, the tear can be easily repaired with a single absorbable suture of 4–0 Nurolon. An air embolism is also a possibility, particularly if the patient is slightly volume depleted and a sinus is inadvertently entered. This can be detected by the precordial Doppler ultrasound, as well as by the end-tidal volume gas spectrometer. Treatment includes placing the patient in a Trendelenburg’s position and flooding the field with saline to prevent further intake of air into the circulation. A small amount of air is usually tolerated with minimal deleterious effect. Injury to the brain itself, as well as the globes, can occur if proper precautionary measures are not taken during the osteotomies, although this risk remains low with an experienced craniofacial surgical team. Pressure sores must be avoided by attention to and protection of the areas where the skull rests during the procedure. The most frequent late complications include infection and recurrence or relapse of the original defect due to suture restenosis. To prevent infection postoperatively, strict sterile technique must be adhered to and prophylactic antibiotics used up to the time of removal of the drain. If osteomyelitis occurs, there is a high risk of loss of the bone grafts.
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44 Total Cranial Vault Repair for Sagittal Craniosynostosis John A. Jane Jr., Kant Y. K. Lin, Tord D. Alden, and John A. Jane Sr. Sagittal craniosynostosis is the most commonly encountered form of craniosynostosis, accounting for an estimated 50 to 60% of isolated nonsyndromic craniosynostoses. It results from the premature fusion and subsequent growth arrest at the sagittal cranial suture. The general appearance of the cranium is one that is disproportionately long and narrow. This condition is termed scaphocepahly or dolichocephaly. Depending on the timing, location, and extent of the pre-
mature sutural closure, infants can present with a variety of skull shapes and forms. Normal skull growth during the first year of life is marked by a tendency toward roundness, where the skull width grows at a greater rate than the skull length. By contrast, in sagittal synostosis, the ratio of skull width to skull length remains constant. This is an important consideration when recommending surgery to patients. It can be stated that, in fact, untreated sagittal synostosis appears to get “worse” with age. This occurs first because the natural tendency to roundness is prevented and second because in absolute terms the head is longer than normal. In addition to the elongated and narrow skull shape, there is often an accompanied occipital knob if posterior sagittal fusion predominates or significant frontal bossing is seen when anterior closure is most prominent. Complete early closure of the sagittal suture leads to both occipital and frontal compensations (Fig. 44–1). In most cases, the orbit and midface are unaffected in this process. Most patients with sagittal craniosynostosis do not have generalized elevated intracranial pressure (ICP). The reported incidence of intracranial hypertension (ICH) ranges from 13.8 to 25% based on preoperative ICP monitoring. Preoperative single photon emission computed tomography studies have shown abnormal cerebral perfusion underlying the fused suture in over two-thirds of patients and positron emission tomography scans demonstrate diminished cerebral glucose metabolism. Children with sagittal synostosis also have an increased incidence of language and learning deficits. Although there is no definitive proof that surgical correction improves cognitive outcome, children in whom surgical intervention was performed >1 year of age experienced an increased incidence of cognitive delay compared with those undergoing surgery at <1 year.
Patient Selection
Figure 44–1 Sagittal craniosynostosis. The deformity includes a disproportionately long and narrow skull. Compensatory growth can occur at the coronal and metopic sutures, causing frontal bossing or at the lambdoid sutures, resulting in an occipital knob. 10.1055/978-1-60406-039-3c044_f001
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Diagnosis is based on the characteristic physical appearance of an infant with a disproportionately long and narrow skull. Premature fusion leads to a palpable ridging along the length of the fused portion of the suture, and this finding can also be helpful. Plain skull films provide useful information regarding the suture patency, but confirmation is most readily obtained using three-dimensional computed tomography of the skull.
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292 Pediatric Neurosurgery Indications and Timing The surgical goals are to improve the overall appearance of the skull and to provide adequate skull volume to relieve possible elevated ICP. Simply put, because sagittal synostosis is characterized by a long and narrow skull, the skull must be made shorter and wider. In addition, compensatory changes in the frontal and/or occipital regions, when present, should also be addressed. Although subject to debate as to the exact timing, age at operation depends on the surgical technique. Craniofacial procedures such as the strip craniectomy or the endoscopic cranial release procedures that use a postoperative molding helmet to effect the change in skull shape are more often performed prior to 6 months. Our opinion is that the total cranial vault technique provides superior surgical control over the cosmetic result. We have found that at 6 months, infants are able to tolerate the volume loss of this more invasive technique well and the bone remains supple enough to manipulate during the reconstruction. Because the volume of the brain almost triples in the first year of life, subsequent growth of the brain can be utilized as an additional factor to help maintain the improved skull shape following surgical release of the fused suture. Early correction also spares the child emotional or psychological trauma over his/her appearance, before the child reaches the age of self-awareness at 5 years old (or younger). An exception to our standard practice of performing surgery at 6 months is in the setting of ICH. In infants who appear to have elevated ICP, surgical correction is performed at the earliest possible date. The diagnosis of ICH based on clinical and radiographic examination can be difficult. The presence of papilledema on funduscopic examination is an excellent clinical marker for ICH. However, its absence does not exclude elevated ICP. Suture diastasis and sellar erosion as evident on plain skull radiographs are more sensitive indicators of raised ICP than the findings of cerebral digital markings seen on the inner table of the calvaria (beatencopper markings). There are no definitive CT findings that correlate with ICP, but obliteration of the basal cisterns are a concerning finding. On occasion, an intracranial monitor is needed to accurately record pressures; however, this is generally reserved for those instances where the child has symptoms suggestive of ICH or where early correction has not been done and a decision to operate would be influenced by the presence of increased ICP.
Preoperative Preparation Once the decision has been reached to proceed with surgery, a preoperative workup consisting of routine blood tests including a complete blood cell count, electrolyte panel, and a prothrombin time and a partial thromboplastin time are performed. Due to the potential for significant blood loss, a type and screen are obtained, and compatible donors among relatives are encouraged to donate for donor-directed intra- and perioperative transfusions. There is some evidence that pre- and postoperative treatment with recombinant erythropoietin may help reduce the need for
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postoperative blood transfusion, but this is not part of our routine practice. At least two large-bore (≥20 gauge) intravenous lines are required for access due to the potential for significant blood loss or fluid shifts during surgery. An arterial line is placed as well as a central line to monitor the total body intravascular volume for both operative and postoperative fluid management. The central line also obviates peripheral venous access issues postoperatively on the ward and significantly impacts postoperative comfort and the ease of care. A Foley catheter is useful to record urinary output, and a thermistor is used to record core body temperatures. A Doppler monitor is placed over the heart to monitor blood flow and is used to detect the possibility of unanticipated intraoperative air embolism. Steroids and anticonvulsants are not routinely used. Prophylactic antibiotics are given just prior to the incision but are not continued postoperatively. In young children, the hair is clipped to allow the surgeon full visualization of the degree of the skull deformity, in order that the surgical correction can be tailored accordingly. This also helps facilitate the scalp closure and postoperative wound care by the nursing staff and the parents.
Operative Procedure Positioning Patient positioning depends on the specific deformity encountered; whether there are both frontal and occipital abnormalities, primarily frontal, or primarily occipital. The vast majority of patients are placed either in a modified prone (“sphinx”) or supine position. The sphinx position is used for patients who have significant occipital as well as frontal compensatory changes in whom we plan to remove both an occipital and frontal flap. This position can give access from the supraorbital rims (although an orbital rim advancement would be difficult) to the foramen magnum. It also allows the surgeon excellent visualization of the complete cosmetic correction, a view not afforded if the surgery is performed in staged supine and prone positions. The supine position is used for scaphocephalic patients who primarily have frontal bossing without significant occipital deformity. This provides access from the supraorbital rims to just posterior to the lambdoid sutures. Access to the occipital bone is limited and requires lifting the infant’s head, a maneuver that must be performed with care and close interaction with the anesthesiologist. On rare occasions in which the forehead appearance is normal and the deformity is mainly occipital, we will use a prone positioning. This generally allows access from the foramen magnum to several centimeters anterior to the coronal suture. In the prone and sphinx positions great care must be taken to ensure that the face is well padded to prevent pressure ulceration. Bilateral tarsorrhaphies are performed, and the scalp and upper face are prepped with Betadine (povidone-iodine) solution and draped. The surgical table is rotated so that the anesthesiologist is positioned along the patient’s side at the foot level. The nursing staff and all instrumentation, which have been placed on a single large table, are positioned op-
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44 Total Cranial Vault Repair for Sagittal Craniosynostosis 293 posite the anesthesiologist, who is also at the foot of the bed. A smaller Mayo stand is positioned over the patient’s abdomen, and only those instruments most currently in use are kept for ready access.
Skin Incision and Flap Elevation A wavy bicoronal incision is performed extending from just behind one ear across to the opposite side. The scalp flap is elevated anteriorly to expose the supraorbital rims. The full extent of the supraorbital rims with elevation of the periorbita is not necessary. Posteriorly the scalp is elevated past the lambdoid sutures and inferior to the occipital knob, if present. The temporalis muscles are left attached to the scalp flap and are elevated off the underlying bone during the subperiosteal dissection.
Craniotomy and Cranioplasty There are several variations of our cranial vault reconstructions for sagittal craniosynostosis. In all, however, the operation begins with removal of a midline biparietal flap that includes the sagittal suture (Fig. 44–2). When the anterior fontanelle is still open, this can be used to dissect the dura from the overlying bone along the sagittal, coronal, and metopic sutures. When not present, the bur holes are fashioned on either side of the sagittal suture just posterior to bregma and anterior to lambda. The width of the biparietal flap varies, but is not taken further lateral than the horizontal portion of the parietal bone. After the midline biparietal craniotomy is performed, a more complete elevation of the dura can be performed at the coronal and lambdoid sutures. Using the craniotome, parallel cuts are made on either side of the coronal and
lambdoid sutures, and these sutures are removed at a width of approximately 1 to 2 cm (Fig. 44–2). The width of the coronal and lambdoid suturectomies varies depending on how much reduction is felt necessary in the anteroposterior dimension. The two lateral temporoparietal segments of the skull are reshaped through a combination of barrel-stavelike osteotomies and a Tessier bone bender (Lorenz Surgical, Jacksonville, Florida). The bones are still attached inferiorly, but they are outfractured to widen the skull appropriately. The removed midline biparietal flap is tailored and then turned 90 degrees to act as a strut maintaining the newly widened skull (Fig. 44–3). The variations of the operation differ according to whether the frontal bone, the occipital bone, both, or neither is removed and reshaped. Patients who have neither frontal bossing nor a significant occipital knob can be managed by simply reapproximating the frontal and occipital bones with the temporoparietal segment that is still attached to the skull base. The amount of shortening is dependent on the width of the lambdoid and coronal suturectomies. The majority of patients, however, require removal of either or both frontal and occipital bones. Patients who have significant deformities in both the frontal and occipital regions undergo bifrontal and bioccipital craniotomies (Fig. 44–3). It is should be emphasized that the occipital craniotomy should be taken inferior to the occipital knob into the suboccipital region. If this is not done, a shelf of bone remains that detracts from the apparent shortening of the skull. Tremendous care must be taken to protect the torcula and transverse sinuses during removal of this bone. If a bioccipital flap has been removed, the occipital knob is reshaped by a series of radially oriented bone cuts, allowing the bone to be flattened yet still kept intact. Once reshaped, the bone is gently squeezed toward the temporoparietal segments to simultaneously shorten the skull and cause a bulging of the dura and brain laterally to reinforce the outfractured segments. This squeeze is maintained by rigidly fixing the bones in place using absorbable plates and screws. If forehead correction is also necessary (as it is in the majority of cases) the bifrontal craniotomy is reshaped in a fashion similar to that used for the occipital knob. The skull length is further reduced by a bringing the frontal bone in proximity to the attached temporoparietal segments and fixing the flap using absorbable miniplates. The frontal bone is reattached to the supraorbital rims using either absorbable suture or miniplates. The remaining bone segments from the removed coronal, lambdoid, and sagittal sutures are then loosely attached to adjoining skull segments to fill any gaps with absorbable Vicryl suture. Rigid fixation is used only in areas under stress to maintain the anteroposterior squeeze and the transverse widening.
Closure Technique
Figure 44–2 Bone removal. All variations of our cranial vault reconstructions remove a midline biparietal flap and include coronal and lambdoid suturectomies. Depending on the deformity, the frontal and occipital bones are also removed.
The operative field is copiously irrigated to remove all nonviable debris and bone dust that could act as a nidus for future infection. Because the temporalis muscles were left attached to the scalp flaps, there is no need to reattach them along the lateral temporal ridges. They will naturally return to their orthotopic positions as the scalp flap is closed.
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Figure 44–3 Cranial vault repair. The skull is widened and held in place by bone struts from the removed midline biparietal craniotomy. The occipital and frontal bones are reshaped and brought into proximity to the fixed temporoparietal bone. This shortens the skull and addresses both
frontal and occipital compensatory deformities. The amount of shortening is dependent on the width of the coronal and lambdoid suturectomies. Absorbable miniplates and sutures are used to maintain the correction. At major stress points, sturdier miniplates are necessary.
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The scalp flap is reapproximated and closed in a two-layer fashion, with buried absorbable sutures in the subgaleal plane, and the skin is closed either using a 4–0 subcuticular absorbable suture or an external running 5–0 fast-absorbing plain gut suture. We have previously placed a subgaleal drain but have abandoned this practice. Although we do believe that it reduces the amount of postoperative swelling, our impression is that it also increases the need for postoperative transfusion. Instead, a snug but nonconstricting dressing is then wrapped in turban fashion over the entire head, and the head is kept elevated at all times to reduce postoperative swelling. Extubation is performed as soon as medically possible.
surance must be given that the majority of the swelling will resolve in 3 to 4 days. In most instances, the child is ready for transfer to the regular ward within 24 to 48 hours. A routine CT scan is not performed. Usually, the child will run a slightly elevated temperature between 38°C and 39°C at day 3 or 4 following surgery. A routine fever workup is performed, but only rarely is the fever caused by infection. The child is considered stable for discharge from the hospital once he or she is tolerating a regular diet and eyelid swelling has resolved enough to permit eye opening. A follow-up visit is arranged for 1 week after hospital discharge.
Complication Avoidance
Postoperative Management Including Possible Complications Immediate postoperative care occurs in the pediatric intensive care unit. Vital signs and arterial and central venous pressures are monitored. Laboratory values are obtained for review of evidence of hypovolemia and blood loss. Depending on the degree of blood deficit, blood transfusions are frequently necessary and the concomitant replacement of coagulation factors may be required. Appropriate dosages of intravenous analgesia are given to keep the patient as comfortable as possible while maintaining a neurological examination. On the ward we alternate acetaminophen and ibuprofen in scheduled doses for the first few days. The child is positioned such that the head is elevated at 30 degrees to reduce swelling as much as possible. Commonly, the eyelids will swell shut within 24 hours following surgery. This can cause anxiety for both the parents and the child, and reas-
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Close communication with anesthesia cannot be overemphasized. Concerns of excess bleeding should be addressed expeditiously. Care should be taken during the scalp incision and reflection to stop bleeding from the skin edges and the pericranium. During the craniotomy the sources of ongoing blood loss must be recognized and controlled both from bone edges and from the dura. Our tendency is to minimize the amount of bone wax onto bone, as this may hinder osseous growth postoperatively. We have found FloSeal (Baxter Corp., Freemont, California) to be effective in controlling most low-flow bleeding along the bone edges. Particular attention must be paid to emissary veins leading from the sagittal sinus. As the major venous sinuses are exposed, patties should be immediately placed over the sinuses to control bleeding. Bipolar cautery generally controls dural bleeders quite easily. Nevertheless, blood loss occurs during our technique and it has become our practice to transfuse at the onset of the operation, and often we will transfuse a unit of fresh frozen plasma for every unit of packed red
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44 Total Cranial Vault Repair for Sagittal Craniosynostosis 295 blood cells. Platelet transfusion should also be considered after significant blood loss has occurred but is not necessary in every operation. The lack of bleeding does not obviate placing patties over exposed sinuses because of the risk of air embolus. Air embolism is a more significant risk in the sphinx position, particularly if the patient is slightly volume depleted. This can be detected by the precordial Doppler ultrasound, as well as by the end-tidal volume gas spectrometer. Treatment includes placing the patient in a Trendelenburg’s position and flooding the field with saline to prevent further intake of air into the circulation. A small amount of air is usually tolerated with minimal deleterious effect. Meticulous attention must be directed in looking for possible tears in the dura mater, which can lead to a persistent cerebrospinal fluid leak, postoperative meningitis, and bone resorption. Dural lacerations can be avoided by careful dissection of the dura from the bone prior to elevation of the flaps. The dura interdigitates with the open coronal, lambdoid, and metopic sutures and should be dissected free prior to attempted elevation of the craniotomies. If recognized, the tear can be easily repaired with a single absorbable suture of 4–0 Nurolon.
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The most frequent late complications include infection, resorption of the bone flap or bone grafts, and relapse of the original defect. To prevent infection postoperatively, strict sterile technique must be adhered to and prophylactic antibiotics are used. If osteomyelitis occurs, there is a high risk of loss of the bone grafts. Patients should be followed on an annual basis through adolescence to monitor future growth of the skull and to document any relapse of the original condition, which could require further surgical intervention.
Conclusion Cranial vault reconstruction must address the specific deformities encountered in the individual patient. Sagittal craniosynostosis is characterized by a disproportionately long and narrow skull. In addition, compensatory growth can result in frontal bossing and/or an occipital knob. Although all require an operation that shortens and widens the skull, variations are performed to address the patient’s specific frontal or occipital deformity.
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45 Metopic Craniosynostosis Paul C. Francel and Jayesh Panchal
The metopic suture is the margin between two adjacent frontal skull plates in which new bone formation occurs secondary to underlying expansion of the brain (the frontal lobe). Although the metopic suture was believed to close physiologically between 1 and 2 years of life, the widespread use of computed tomography (CT) in early childhood has confirmed that the suture closes physiologically late in the first year of postnatal life. This delay enables the anterior cranial fossa and the frontal bone calvarial plates to develop more fully prior to the time of fusion. The premature fusion of the metopic suture is referred to as metopic craniosynostosis. Any premature fusion will result in a calvarial and an orbital change secondary to brain expansion constrained by the metopic sutural fusion. There may be effects in the base of the skull as well. Cranial vault abnormalities occurring secondary to craniosynostosis have two phases: (1) cranial restriction secondary to sutural fusion; and (2) compensatory deformational change in the remaining portion of the calvaria secondary to underlying brain growth.
Patient Selection In most patients, the etiology of metopic craniosynostosis is unclear; however, it often appears to relate to the underlying brain anatomy. For example, the frontal lobes may be hypoplastic in some form. In fact, early neuroradiological evaluation may not reveal brain compression but rather a collection of cerebrospinal fluid (CSF) beneath the dura, with premature fusion potentially occurring secondary to the lack of external pressure from frontal lobe hypoplasia. Once sutural fusion has occurred, continued brain growth and other forces will cause deformational changes in the surrounding bone. In the patient with metopic craniosynostosis, the result of such fusion is the characteristic trigonocephalic head shape in which a bifrontal bone plate is created that is shortened significantly in its width anteriorly (near its junction with the orbits) and that often produces an almost keel-like midline sutural ridge (Fig. 45–1). This abnormality occurs because bone growth continues at the coronal but not at the metopic suture. Orbital changes also occur due to the intimate association of the frontal bone with the orbit itself and the frontal calvarial bone making up a portion of the orbit. These changes usually involve
Figure 45–1 Cranial three-dimensional computed tomography, superior view, of a patient with metopic craniosynostosis. Note the trigonocephalic head shape with the apex located near the anterior nasal portion of the patient and the lack of a visualized metopic suture. A minor amount of ridging is also noted along the metopic suture. 10.1055/978-1-60406-039-3c045_f001
the creation of some element of orbital rim hypoplasia and hypotelorism (Fig. 45–2). The diagnosis is suggested by visual inspection (Figs. 45– 3 and 45–4). Frequently, the abnormality is noted by the patient’s parents because the dysmorphology is in a visible location, namely the frontal area or forehead and the orbits. The lateral canthal angles and, therefore, the eyebrows may also appear elevated, and there is often a significant lack of any orbital rim prominence. The repair of trigonocephaly secondary to metopic craniosynostosis involves a bilateral procedure. The procedure must address the trigonocephalic head shape of the calvaria, the recession of the orbits, orbital hypoplasia, and often some element of hypotelorism. Although correction is sometimes believed to be purely cosmetic, recent evidence suggests that this repair also helps with vision and eye-movement problems frequently seen in patients with metopic craniosynostosis and, as has been seen using single photon emission computed tomography, may result in
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Figure 45–2 Three-dimensional computed tomography, frontal projection. Note that the patient had some element of hypotelorism. Although difficult to discern here, there is also a lack of projection of the orbital rims. 10.1055/978-1-60406-039-3c045_f002
improved perfusion to the frontal brain parenchyma as well. Occasionally, this sutural fusion may be associated with increased intracranial pressure, which is then relieved by reconstruction. Ultimately, the family and the surgeon must realize that the goals of the cranial vault and orbital surgery are to release the fused suture and to secondarily correct the compensatory deformational changes that have occurred in the orbits and in the frontal bone. The procedure outlined below gives an immediate correction of the trigonocephalic head shape with a new cranial shape that is maintained over the long term and is normal in appearance. This preservation of appearance is documented by photographic analysis, frequent evaluations of the child
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Figure 45–4 Intraoperative positioning of the patient, superior view. Note the head shape with marked prominence in the region of the metopic suture anteriorly toward the nasion. The head shows a clear trigonocephalic shape created particularly by the recession of the orbital rims. 10.1055/978-1-60406-039-3c045_f004
by our multidisciplinary craniofacial team, and by cranial vault and orbital measurements obtained on the threedimensional (3-D) CT. The actual corrections made are based on complex cephalometric measurements determined using 3-D CT to ensure that the appropriate correction is obtained. Analysis by an unbiased, independent multidisciplinary craniofacial team is based on objective measures; their results help to improve or modify the operative procedure. In addition to cosmetic benefits, early evidence suggests benefits in neuropsychological functioning and, occasionally, benefits in vision and extraocular movement.
Preoperative Preparation Evaluation
Figure 45–3 Artist’s rendition of the patient, submental vertex view. Note the trigonocephalic head shape, hypotelorism, and metopic ridging.
All children with a craniofacial deformity at birth should be evaluated by a craniofacial multidisciplinary team. This team ensures that the patient is treated in a comprehensive coordinated fashion not possible by a single physician alone. The primary team members include a neurosurgeon, a craniofacial plastic and reconstructive surgeon, and an oral maxillofacial surgeon. Oral maxillofacial involvement in patients with metopic craniosynostosis is limited because the craniofacial abnormality is predominantly related to the cranial vault and the orbit, except in rare instances of metopic craniosynostosis associated with other congenital malformations (e.g., malocclusion). The patient is also evaluated by a pediatric neurophthalmologist because of orbital involvement. All surgical procedures require a pedi-
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298 Pediatric Neurosurgery atric anesthesiology team and pediatric intensivists, who manage the patient postoperatively in a pediatric intensive care unit (ICU). Our team also includes several other specialists. A very integral part of the team includes neuroradiologists who perform 3-D CT and 3-D magnetic resonance imaging (MRI) on all patients pre- and postoperatively. We have found that 3-D CT is critical for preoperative planning and for objective follow-up; it also provides details of analysis not provided by plain x-rays or standard CT. 3-D MRI allows an evaluation of the potential etiology of these conditions or other underlying disorders not previously possible. A preoperative neuropsychological evaluation has also been found useful in assessment of postoperative outcome. Unlike previously believed, the procedure is not simply cosmetic and improvements have been observed in several children after surgical correction; we have noted that some baseline neuropsychological functioning disorders, particularly frontal lobe–based, are not improved following surgical treatment. This suggests that one potential etiology of metopic craniosynostosis, namely frontal lobe hypoplasia, may also be the etiology of some abnormalities in neuropsychological functioning noted in these children rather than the craniosynostosis itself causing the dysfunction. Critical to the functioning of the craniofacial team is the referring pediatrician or the family medicine/internal medicine physician who maintains a link between the patient/ family and the team. The link also acts in a reverse direction, with education of the referring physician allowing more timely referral, patient selection, and timing of surgery. The diagnosis of trigonocephaly and potential metopic craniosynostosis is usually not difficult in the moderate and severe forms of the disorder, but may be difficult in milder cases. As mentioned earlier, physical examination often reveals a palpable bony ridge along the metopic suture and visible abnormalities in the head shape involving the forehead, face, and especially the orbits. However, we use 3-D CT to objectively document suture fusion, especially in children scheduled to undergo surgery. Infants are ideally treated before the age of 1 year and preferably before the age of 5 to 6 months. Some centers recommend correction around 4 to 8 months, which is the time of greatest blood volume, but in our experience, we have found that the sooner the patient is treated after diagnosis the more likely that correction will be effective. The preference for earlier surgery is guided by the bone characteristics. The cranial and the orbital bones become brittle at 1 year of age, and remodeling requires different techniques than used in children <1 year. When surgery is performed in the younger age group, there is a significant decrease in operative time, less blood loss, and a more successful recontouring because of the softer nature of the bone and its positive response to microfracturing craniofacial techniques compared with the brittle bone of an older child. Occasionally, a child with metopic craniosynostosis will not present before the age of 1 year, in which case other techniques are utilized. Children presenting between the ages of 1 and 3 years require a more distinct combination of treatments because their bones cannot be remodeled easily due to their more brittle nature, and yet fixation at that
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age is not desired because of continued significant brain expansion. After the age of 3 years, the techniques devised for softer infant bone can no longer be used, and more rigid fixation is necessary. The brain acquires ~75% of its adult volume by the age of 3 years and 90% of the adult volume by the age of 4 years so that remodeling techniques that provide long-term rigid fixation should be avoided in children <3 years of age.
Planning Preoperative planning with 3-D CT is critical in obtaining an optimum result with long-term improvement. First in this planning is measurement of the degree of anterior advancement required of the supraorbital bar. In metopic craniosynostosis, the supraorbital rim is recessed. A two-dimensional long axis view along the apex of the orbit and the center of the cornea demonstrates the extent of this recession. Normograms reveal that the supraorbital rim should be ~2 to 3 mm anterior to the vertical plane of the cornea. The extent of ventral movement of the supraorbital rim required at this 3 mm position is then determined. Depending on the severity of the involvement, this advancement usually varies between 7 and 15 mm. It is also common to find that the advancement is similar on both sides. Because of the frequent presence of orbital hypotelorism, an interposition bone graft is often required. This is placed in position in the midline of the orbit through the metopic suture in its continuation to the frontal nasal suture. We utilize a tenon-inmortise bone graft technique that is described below and secure the new hypotelorism correction construct with absorbable plates and screws. The degree of narrowing at the sphenoid wings is also measured and is corrected in line with normograms noted for the age of the child. We frequently perform barrel-staving through the remaining temporal bone and sphenoid wing margins to provide a gentle outfracturing of these areas. Prior to the final reattachment with absorbable plates and screws, the cranial vault is recontoured to precisely fit this shape.
Preparation Prior to surgery, the patient undergoes 3-D CT and 3-D MRI. Data from the 3-D CT are used to determine preoperatively the exact amount of orbital advancement on each side and to make calculations for the frontal bone recontouring. In cases where hypotelorism is present, an orbital interposition graft is necessary. We routinely have the patient typed and crossmatched in case of significant bleeding intraoperatively, particularly from the sagittal sinus. This is done as a safeguard but is made available prior to skin incision. In most instances, the blood is donated by a parent or a close relative, but occasionally, blood-banked blood is utilized. Usually, the blood loss is small (~50 mL), mainly from oozing around the bone edge, but it is still of great risk to the patient undergoing craniofacial reconstruction, as this volume is a significant percentage of the patient’s total blood volume. All patients are given intraoperative antibiotics at the time of skin prepping so that adequate blood concentrations
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will have been obtained at the time of skin incision. The patient is positioned supine, usually with a roll underneath the shoulder and the neck slightly extended. An arterial line, one or two peripheral venous lines, and a Foley catheter are routinely placed.
Operative Procedure Scalp Incision and Dissection Because of the very short nature of an infant’s hair, we usually do not shave or clip it prior to surgery. The scalp, including the ears and facial region, is scrubbed with Betadine (povidone-iodine) solution. We never place alcohol near the eyes, and Betadine soap solution is avoided near the eyes. The skin is infiltrated with a 0.5% lidocaine with epinephrine (1:200,000) along a zig-zag-shaped scalp incision. We prefer a zig-zag incision because it provides a cosmetically acceptable incision that heals with less scarring due to a repeated change in the direction of the force vectors. The incision line is also less noticeable as the patient ages, for the hair will not part along a zig-zag incision as it will along a straight bicoronal incision. The head and the face to the tip of the nose are prepped and draped. This allows access to the calvaria and orbits. We begin the incision at the vertex utilizing a no. 15 blade. Further dissection is performed in the subgaleal plane, utilizing a coagulating small cautery tip. Laterally, the temporalis fascia is divided close to its insertion; the temporalis muscle is elevated from the temporal, frontal, and parietal bones until the lateral orbital wall is exposed. Dissection is continued in the subgaleal plane up to the line 10 mm above the supraorbital rim followed by a subperiosteal dissection up to the supraorbital rim. We tease the supraorbital neurovascular bundle out of its notch, which at this age is frequently closed and must be opened prior to anterior displacement of the scalp flap. Further dissection is continued in the subperiosteal plane to expose the roof of the orbit. Care should be taken to avoid injury to the periorbital contents. The dissection is continued along the orbital roof from the lacrimal crest medially to the frontozygomatic suture laterally and often down to the infraorbital nerve exit.
Craniotomy and Osteotomy At this point, the neurosurgeon and the craniofacial surgeon plan the osteotomies. This is begun by performing a bifrontal craniotomy (Fig. 45–5). To provide maximum safety, two small bur holes are created on either side of the sagittal suture 1 to 2 cm behind the coronal suture. After gently freeing up over the sinus, a craniotomy flap can be elevated. Initially, the osteotomies reach the pterion and extend inferiorly and ventrally to span the lateral orbital wall to then reach the frontozygomatic suture. Once the frontal osteotomies are performed, the dura is separated from the bone using a Penfield dissector. Care is taken to prevent dural perforation. Any laceration detected is repaired immediately. The frontal bones are elevated and delivered to a separate table where radial osteotomies are performed.
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Figure 45–5 Artist’s rendition of the bifrontoparietotemporal craniotomy flap. Note the placement of bur holes on either side of the sagittal suture to provide for a safe exposure of the sagittal sinus. After elevation of this large bifrontal bone flap, exposure is provided to elevate the dura from the orbital roof via an extradural dissection. 10.1055/978-1-60406-039-3c045_f005
The dura from the anterior cranial fossa is dissected from pterion to pterion. It is then carried down to the subtemporal region and into the cranial base. Dissection in the midline is carried up to the level of the cribriform plate. Malleable retractors are used to gently retract the frontal lobes, with most of the retraction being provided by the positioning of the patient, with some extension of the head so that the frontal lobes actually displace posteriorly by gravity. An osteotomy is made in the roof of the orbit using an osteotome (Fig. 45–6). The osteotomy in the anterior cranial fossa is extended medially to reach the crista galli and laterally to reach the pterion. Dissection is carried through the sphenoid wing at that point at approximately a 45 degree angle and is continued with orbital protection to ensure that the sphenoid ridge has been completely opened. A reciprocating saw is used to complete the osteotomy from the sphenoid ridge to the frontozygomatic suture and from the ipsilateral lacrimal crest to the contralateral lacrimal crest across the nasofrontal suture. A 3 mm osteotome is then utilized to complete the osteotomy by gently tapping with a mallet. The supraorbital bar as a bilateral complex is then excised and delivered to a separate table where reconstruction can be performed. At this point, we divide the supraorbital bar in two by cutting it in the midline. Each half is split at the highest point and is widened or narrowed depending on the preoperative measurements obtained from the CT (Fig. 45–7). We recently utilized a T-shaped LactoSorb (Biomet Microfixation, Jackson-
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Figure 45–6 (A) Artist’s rendition of the orbital anterior cranial fossa and sphenoid wing osteotomies. An osteotomy is made across the anterior cranial fossa beginning centrally in the orbital roof about halfway between its anterior border, with the orbital rim and its posterior border at the optic canal. It is carried medially just anterior to the crista galli and laterally toward the pterion. Dissection is continued through the middle fossa skull base, through the subtemporal region, and finally joining the frontozygomatic suture anteriorly. In the process, an osteotomy is made through the sphenoid wing at approximately a 45 degree angle. This osteotomy through the sphenoid wing is usually performed using a 3 mm osteotome. (B,C) Three-dimensional computed tomography, superior view, of the cranial base (B) prior to and (C) following anterior cranial fossa, orbital, and sphenoid wing osteotomies. 10.1055/978-1-60406-039-3c045_f006
ville, Florida) absorbable plate to rigidly fix the halves of the supraorbital bar (Fig. 45–8). Frequently, we use an 8 ⫻ 2 hole absorbable plate fixed at the most lateral end of the supraorbital bar to then secure it in an advanced position. The supraorbital bar is advanced bilaterally by 7 to 15 mm, depending on the preoperative 3-D CT measurements. We employ a tenon-in-mortise technique utilizing bone from the calvaria removed further posteriorly from the parietal bone; this is inserted into the interval at the site of advancement (Fig. 45–9). The posterior or dorsal end of the absorbable plate is then rigidly fixed using an absorbable 1.5 mm screw. By utilizing such a technique, symmetric orbits can be obtained. Because of significant narrowing noted in trigonocephaly at the sphenoid ridge in the pterion, a barrel-stave-like osteotomy is made and outfracturing is created to provide its correction.
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As mentioned earlier, the frontal bone is reshaped after performing multiple radial osteotomies (see Fig. 45–6). We frequently utilize various-sized Tessier bone benders (Lorenz Surgical, Jacksonville, Florida) to provide the appropriate correction. It is important to make every attempt to remove the trigonocephalic head shape, and we frequently excise the midline metopic ridge with the craniotome to remove its prominence. Once both the frontal bones are symmetrical and reconstruction is made, measured, and compared with the preoperative plan based on the 3-D CT, the frontal bone is secured to the advanced supraorbital bar with 1.5 mm absorbable plates and screws (Fig. 45–10). Because of the defect created between the advanced orbital rim and the base of the skull, temporalis muscle advancement is performed next. Frequently, the temporalis muscle is sectioned posteriorly just anterior to the external
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Figure 45–7 Correction of hypotelorism. In many patients with metopic craniosynostosis an interposition bone graft is required at the site of excision of the metopic suture. This corrects for the hypotelorism created as a part of the disease. The degree of correction is based on the abnormalities, and measurement is based on the threedimensional computed tomography compared with normative tables for age. Correction is usually on the order of 5 to 7 mm but is determined precisely in each patient. This utilizes a tenon-in-mortise setup that is locked in place with the LactoSorb absorbable plate-and-screw system. Note the resultant advancement of the lateral portions of the supraorbital bar. 10.1055/978-1-60406-039-3c045_f007
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Figure 45–9 Superior view of the calvaria following reconstruction. Note the radial osteotomies made within the frontal bone with recontouring. Also note the parietal bone defect where the graft was taken to use as the interposition graft between the two halves of the orbital bar. The harvesting of this bone graft is well enough posterior to avoid creating a cosmetic abnormality and lies close to the region where an anterior fontanelle would normally have been. 10.1055/978-1-60406-039-3c045_f009
Figure 45–8 Operative specimen of the orbital bar in corrected hypotelorism. Note the interposition bone graft, the securing with the absorbable plates and screws, and the new contour of the orbit after its reconstruction and remodeling. 10.1055/978-1-60406-039-3c045_f008
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Figure 45–10 Three-dimensional computed tomography (3-D CT), submental vertex view, of the skull (A) prior to and (B) following cranial reconstruction and orbital advancement and correction of hypotelorism. Note the significant advancing of the orbit and the sphenoid wing bilaterally, the correction of hypotelorism with more lateral displacement of the orbits, an interposed bone graft between the orbital bar halves, and complete removal of the trigonocephalic head shape. 10.1055/978-1-60406-039-3c045_f010
ear and then advanced so that the muscle completely covers the enlarged keyhole site created by the advancement. By using absorbable sutures, such as Vicryl, through the contour of the orbital rim, we are able to secure the temporalis muscle in this advanced position to prevent an “hourglass” deformity of the calvaria. We rely on a tenon-in-mortise securing of the advanced orbital bar as opposed to a tongueand-groove or other design because these other techniques utilize an area of calvaria for the tongue-and-groove that must undergo cranial remodeling. By utilizing a more rigid structure, namely the sphenoid ridge within the anterior cranial fossa, rigid procuring of the reconstruction can thereby be obtained. This technique also avoids creating significant cranial defects within the calvarial bone because the actual procuring of the advancement occurs through the cranial base, which will not be visualized on the exterior surface.
Repairs in older children require slightly different bone remodeling techniques. In this population, we frequently remove the bone and perform kerfing on the endocranial side of the frontal bone to remodel it appropriately. Subsequent procedures can be used after the kerfing, which creates numerous microfractures within the bone so that remodeling can take place. The other portions of the technique remain essentially the same. It is interesting to note that despite the sectioning at the frontozygomatic suture, no unpleasant cosmetic deformity occurs at the lateral orbital wall. From a cosmetic standpoint, orbits appear more advanced and with better contour, even though the lower orbit itself has not been advanced in this process (Fig. 45–11). In patients where the metopic craniosynostosis is associated with other facial abnormalities, the zygoma and portions of the midface may also be advanced in combination with the orbital bar advancement.
Closure At this point, the scalp flap is replaced and symmetry is confirmed. A single, 7 mm suction drain is placed underneath the scalp flap, and the wound is closed in layers using interrupted 4–0 Vicryl sutures for the galea and continuous 4–0 Vicryl Rapide (rapidly absorbing Vicryl) for the skin closure. A light dressing and head bandage are used to complete the procedure. We use absorbable plates and screws (LactoSorb). The plates provide rigid fixation for 2 to 3 months, rigid support for 3 to 6 months, and biodegrade at 9 to 12 months, eliminating the possibility of intracranial migration. This cannot occur when titanium plates are used unless the patient undergoes a subsequent surgery for removal of the plates. Interosseous wires have the risk of perforation through the overlying skin. Because of the use of the absorbable plates, extensive rigid fixation can be done without the concern of deleterious results from rigid fixation, even in children <3 years of age. Fortunately, absorbable plate fixation also appears to work in children >3 years of age.
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Postoperative Management Including Possible Complications Following extubation in the operating room, the child is transferred to the pediatric ICU for a 24-hour observation period. We use this mainly for monitoring the level of consciousness and hemodynamic evaluation. The parents are advised that there can be considerable swelling of the scalp and periorbital ecchymosis, but that this will probably regress after 2 to 3 days. Postoperative pyrexia is not uncommon and is most probably secondary to subgaleal blood and the bony osteotomies performed. We maintain the hematocrit well above 20. A perioperative 3-D CT is obtained on the third to fifth postoperative day. This is used for documentation of the reconstruction, evaluation of appropriate symmetry, and advancement in all the sites of osteotomy. Following this, the child is discharged and is then assessed by frequent monitoring. Regular follow-up with the craniofacial team is done at 3 weeks, 6 weeks, 3 months, 6 months, and 1 year.
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Figure 45–11 Three-dimensional computed tomography (3-D CT), lateral view, of the skull (A) prior to and (B) following cranial and orbital remodeling. (C) 3-D CT, frontal view, following orbital and cranial remodeling. Despite sectioning to the frontozygomatic suture, the orbital advancement does not create an unpleasant cosmetic deformity at the orbital rim. By using a tenon-in-mortise setup (incorporating the advancement through the sphenoid wing and the cranial base), advancement of the orbit is obtained without disrupting the cranial
Annual visits are scheduled until the age of 6 years and every 3 years thereafter. Postoperatively, 3-D CT is performed immediately, at 6 months, and at 1 year. Longitudinal follow-up allows assessment of disease and the procedure, not only on the cosmetic deformity but also in terms of neuropsychological development and further craniofacial growth. We recently added 3-D MRI at the 1-year follow-up. This enables an evaluation of the soft-tissue content and the effects on the underlying brain. As part of the experimental protocol, we occasionally perform positron emission tomography pre- and postoperatively to evaluate changes in metabolism of the cortex underlying the fused suture. In older children, there is concern about failure of reossification between the advanced frontal bone posterior margin and the remaining parietal bone of the calvaria. In these instances, repair of this large defect can be brought about by a tongue-and-groove pattern posteriorly. Unlike the tongue-and-groove pattern used by some to advance the orbits, the pattern provides an interlocking between the posterior portion of the advanced frontoparietal bone and the anterior portion of the remaining parietal bone. This pattern breaks up what would be a long bicoronal defect into multiple smaller areas of cranial defect that are smaller than critical-sized defects and more likely to reossify spontaneously. This advancement can be maintained using absorbable plates and screws.
Complications The most serious complication during these surgeries is exorbitant blood loss. Blood loss must be minimized and replaced quickly. We employ techniques that minimize blood loss to a manageable level. The blood loss that occurs is an almost necessary loss from the bone osteotomies. In no
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reconstruction in the temporal region. A comparison of (A) and (B) reveals advancement of the orbit in the lateral position. Note the almost notch-like appearance of the advanced orbital rim laterally at the frontozygomatic suture and the barrel-stave-like osteotomies made in the temporal region (to outwardly bow the temporal area for the necessary reconstruction). A tongue-and-groove pattern would not have been able to provide a capability for temporal cranial reconstruction as well. 10.1055/978-1-60406-039-3c045_f011
patient we have treated has significant blood loss occurred from a major venous sinus. We believe that this occurs secondary to our technique of freeing the dura completely prior to the actual bone osteotomies that can be performed quite easily in children 1 year of age. Surgery should always be performed in a designated children’s hospital with pediatric anesthesiologists trained in techniques of craniofacial surgical anesthesia. We also utilize pediatric ICU facilities. Although it is tempting to avoid this because the patients do not show neurological deficits, the extensive degree of reconstruction that has occurred and the need for close hemodynamic monitoring necessitate the ICU stay. Although it appears logical that the bone graft would be a source of infection, we have not noted this in any of our patients. The incidence of wound infection and dehiscence is also extremely low. There have not been any instances of CSF leakage, although, if a dural tear does occur, prompt attention must be rendered or complex pseudomeningocele formation will occur. Long-term follow-up may reveal minor asymmetries of the orbital bar or forehead. Most commonly, these may show as small defects that if particularly unsightly can be fixed using hydroxyapatite, which is commercially available. This is usually necessary only in instances where incomplete ossification occurs in which the defect is 1 to 2 cm or larger. In no patient we have treated has a revision osteotomy or readvancement of the supraorbital bar been needed. It is imperative to avoid any injury to the frontal lobes or the eye itself. A near-perfect or perfect cosmetic result should be expected. This can be obtained if preoperative measurements are made to provide for the necessary correction. In instances of marked abnormality, we have overcorrected slightly so that the final long-term result will be maximal.
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46 Unicoronal Synostosis Jayesh Panchal and Paul C. Francel
Patient Selection Unicoronal synostosis occurs due to premature closure of the coronal suture. Proposed theories for premature closure include abnormalities in the cranial base and abnormalities of the underlying dura and of the underlying brain. The theory of abnormal morphology of the cranial base is not currently in favor. Research on the underlying dura has demonstrated high levels of mRNA and transforming growth factor-β in sutures, which close prematurely, and suggests that the underlying dura is the predictor for closure of the overlying suture. The reason that this dura behaves in an abnormal fashion is as yet undetermined. One isolated study demonstrated abnormal morphology of the sulci and gyri of the cortex underlying the abnormal dura and suture. Premature closure of the coronal suture restricts growth of the calvaria on the ipsilateral side and is associated with compensatory growth on the contralateral side. The deforming vector results in retraction of the forehead, the anterior cranial fossa, the roof, and the lateral wall of the orbit. Unicoronal synostosis manifests early in infancy by the presence of an asymmetrical forehead and orbit. The ipsilateral forehead is recessed, the ipsilateral eyebrow higher, and
the palpebral fissure wider compared with the contralateral side. Orbital dystopia is usually present, with the ipsilateral globe at a higher level. If uncorrected in early infancy, the deforming forces result in an asymmetrical face and tilted occlusal cant. In contrast, the contralateral side demonstrates frontal bossing with ventral advancement of the lateral orbital wall (Figs. 46–1A, 46–2A, 46–3, and 46–4). Unicoronal synostosis may be nonsyndromic or could be associated with syndromes (e.g., craniofrontonasal dystopia) and extracranial manifestations, which involve the cardiovascular, genitourinary, and skeletal systems. Unicoronal synostosis is sometimes associated with hypertelorism (increased interpupillary distance).
Timing of Surgery There is an increasing consensus among craniofacial surgeons and neurosurgeons that surgery should be performed in early infancy for the following reasons: 1. The majority of the growth of the brain takes place in the first year of life. The deforming vectors of the continually growing brain result in progression of the deformity with increasing age.
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Figure 46–1 (A) A 4-month-old female infant with left unicoronal synostosis. Note dystopia with the left pupil and left eyebrow higher than the right. The left palpebral fissure is wider than the right side, and the left fronto-orbital bar is recessed compared with the right. There is asymmetry of the face. (B) One-year postoperative follow-up demonstrating both pupils at same level. The fronto-orbital bar and both sides of the face are symmetrical.
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10.1055/978-1-60406-039-3c046_f002 Figure 46–2 (A) Superior view of the same child as in Fig. 46–1 demonstrating recession of the left frontoorbital bar. (B) One-year postoperative follow-up demonstrating symmetry between the right and the left fronto-orbital bars.
The asymmetry of the calvaria and orbits leads to a diagnosis of unicoronal synostosis in early infancy. Most frequently, the pediatrician refers the infant to a craniofacial team. A
preoperative evaluation should include a geneticist to rule out associated syndromes and a neuropsychologist to perform a quantitative assessment of the motor and cognitive skills of the child. Few studies have revealed that there is a significantly higher incidence of minor learning disorders in children with nonsyndromic single suture synostosis. Although the diagnosis of unicoronal synostosis can be confirmed utilizing skull x-ray series, the wide availability of three-dimensional computed tomography (3-D CT) often supersedes performing an x-ray of the skull. 3-D CT should include a scale (ruler) alongside the images to enable the surgeon to plan the surgery by taking measurements from the image. Standardization of the images also allows comparison of pre, peri-, and postoperative images. The following views should be included in the protocol: frontal, right lateral, left lateral, superior, inferior (ectocranial), posterior, superior view without the calvaria to demonstrate the cranial base (endocranial), and axial view along the long axis of the apex of the orbit and the center of the cornea. These views allow quantification of the severity of the deformity, enabling the surgeon to plan the site of the osteotomy and the extent of movement necessary to correct the deformity. The 3-D CT demonstrates fused coronal suture, ipsilateral
Figure 46–3 Preoperative lateral view on the contralateral side demonstrating a normal relationship between the fronto-orbital bar and the plane of the cornea.
Figure 46–4 Preoperative lateral view on the ipsilateral side demonstrating an abnormal relationship between the fronto-orbital bar and the plane of the cornea.
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2. Few studies have demonstrated an increase in the intracranial pressure in nonsyndromic single suture synostosis. 3. Single photon emission computed tomography positron emission tomography (PET) scans have demonstrated a decrease in the cortical blood supply underlying the premature suture, which was normalized following surgery. 4. Osseous defects following surgery undergo reossification more completely in patients <1 year of age compared with older children. Delay in surgery beyond the first few years of life leads to progressive deformity of the cranial base, which results in abnormal facial growth and asymmetry of the maxilla and the mandible. 5. Surgery performed in early infancy reverts the abnormalities in the cranial base.
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Figure 46–5 (A) Three-dimensional computed tomography demonstrating inequality of the orbits. The left supraorbital rim is higher compared with the right and the left orbit is narrower compared with the
elevated superior orbital rim, deviated anterior cranial base, and recessed ipsilateral frontal bone (Figs. 46–5A, 46–6A, 46–7A, 46–8A, 46–9A, and 46–10A).
Planning
right. (B) One-year postoperative scan demonstrating equality of the orbits. Both orbits are symmetrical. 10.1055/978-1-60406-039-3c046_f005
The extent of ventral movement of the supraorbital rim is measured so as to position it 3 mm ventral to the vertical plane of the cornea. The amount of movement varies between 7 and 15 mm, depending on the severity of the unicoronal synostosis.
Correction of the Asymmetry of the Orbits Ventral Advancement of the Supraorbital Bar The ipsilateral supraorbital rim is recessed. A two-dimensional long axis view along the apex of the orbit and the center of the cornea demonstrates the extent of recession. The ipsilateral supraorbital rim is dorsal to the plane of the cornea. Normograms have revealed that the supraorbital rim is ~2 to 3 mm ventral to the vertical plane of the cornea.
The ipsilateral roof of the orbit is higher than the contralateral orbit, although the contralateral orbit is wider than normal. The height and width of the orbit are determined utilizing normograms. The extent of correction is determined. The height of the ipsilateral orbit is reduced by excising bone at the frontozygomatic and nasomaxillary sutures, and its width is increased by inserting a cranial bone graft into
Figure 46–6 (A) Three-dimensional computed tomography demonstrating recession of the left fronto-orbital bar. (B) One-year postoperative scan demonstrating symmetry of the left and right fronto-orbital bars. 10.1055/978-1-60406-039-3c046_f006
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Figure 46–7 (A) Three-dimensional computed tomography lateral view, on the contralateral side demonstrating a normal relationship between the fronto-orbital bar and the plane of the cornea.
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(B) One-year postoperative scan demonstrating maintenance of a normal relationship between the fronto-orbital bar and the plane of the cornea. 10.1055/978-1-60406-039-3c046_f007
Figure 46–8 (A) Three-dimensional computed tomography, lateral view, on the ipsilateral side demonstrating an abnormal relationship between the fronto-orbital bar and the plane of the cornea.
(B) One-year postoperative scan demonstrating a normal relationship between the fronto-orbital bar and the plane of the cornea.
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Figure 46–9 (A) Three-dimensional computed tomography, endocranial view, demonstrating recession of the ipsilateral fronto-orbital bar and deviation of the anterior cranial base to the ipsilateral side. (B) One-year postoperative scan demonstrating symmetry of the fronto-orbital bar and improvement in deviation of the anterior cranial base. 10.1055/978-1-60406-039-3c046_f009
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Figure 46–10 (A) Three-dimensional computed tomography, ectocranial view, demonstrating recession of the ipsilateral fronto-orbital bar deviation of the anterior cranial base to the ipsilateral side and asymmetry of the mandible. (B) One-year postoperative scan demonstrating symmetry of the fronto-orbital bar and improvement in deviation of the anterior cranial base and of the mandible. 10.1055/978-1-60406-039-3c046_f010
the supraorbital rim. Similarly, the height of the contralateral orbit is increased by elevating the supraorbital bar and its width is reduced by excising a bone segment from the supraorbital bar.
Preparation Careful examination is essential to rule out other congenital anomalies. Preoperative workup includes determination of the child’s blood group. A parent or relative is requested to donate 2 units of blood prior to surgery. Cell savers are used intraoperatively to aid autotransfusion. A complete blood count and crossmatch are obtained intraoperatively. Surgery should be performed with a wide-bore intravenous access, intra-arterial pressure monitoring, and per urethral catheterization. Intraoperative antibiotics include gentamicin and nafcillin.
Operative Procedure After endotracheal intubation, the child is positioned supine on the operating table with the head on horseshoe-shaped padding. Depending on the preference of the parents, either all the patient’s hair or only that along the planned incision is shaved. The head and face to the tip of the nose are prepped and draped. This allows access to the calvaria and orbits. A zig-zag-shaped bicoronal incision is marked at midvertex (Figs. 46–11A and 46–11B). This incision prevents the hair from parting along a straight line, thereby concealing the incision. The skin is divided utilizing a no. 15 scalpel. Further dissection is performed in the subgaleal plane utilizing coagulating cautery (Fig. 46–11C). Laterally, the temporalis fascia is divided close to its insertion and the temporalis muscle is elevated from the parietal bone until the lateral orbital wall is exposed. Dissection continues in the subgaleal plane until a point 10 mm above the supraorbital rim. The periosteum is divided with a cautery and stripped to expose the supraorbital rim. The supraorbital neurovascular bundle is gently teased out of the notch. In rare cases, a narrow osteotome is necessary to relieve the neurovascular bundle. Further dissection is continued in the subperiosteal
plane to expose the roof of the orbit. Care should be taken not to violate the periorbital contents. The orbital roof from the lacrimal crest medially to the frontozygomatic suture laterally is exposed. The neurosurgeon and craniofacial surgeon plan the osteotomies. Anteriorly, an osteotomy is planned 12 to 15 mm above the supraorbital rim. Laterally, the osteotomies reach the pterion and extend inferiorly and ventrally to span the lateral orbital wall to the frontozygomatic suture. Posteriorly, osteotomies are planned to reach 20 to 25 mm dorsal to the coronal sutures. When the osteotomies are marked, the neurosurgeon performs a bur hole at the intersection of the proposed osteotomy sites. The osteotomies are performed utilizing a Midas Rex osteotome (Medtronic Inc., Ft. Worth, Texas) with a shoe. Once the frontal osteotomies are performed, the dura is separated from the bone using a Penfield dissector. Care is taken to prevent dural perforation. Any lacerations detected are immediately repaired. The frontal bones are excised and delivered to the craniofacial surgeon (Fig. 46–11D). The dura from the anterior cranial fossa is dissected from pterion to pterion. Malleable retractors are used to retract the frontal lobes and the periorbital contents. An osteotomy is made in the roof of the orbit using a Midas Rex osteotome. The osteotomy in the anterior cranial fossa is extended medially to reach the crista galli and laterally to reach the pterion. A reciprocating saw is used to complete the osteotomy from the pterion to the frontozygomatic suture and from the ipsilateral lacrimal crest to the contralateral lacrimal crest across the nasofrontal suture. A 3 mm osteotome is utilized to complete the osteotomy by gently tapping with a mallet. The supraorbital bar is excised and delivered to the side assembly table (Fig. 46–12). The craniofacial surgeon divides the supraorbital bar by splitting it in the midline. Each superior orbital bar is split at the highest point and is widened or narrowed depending on the preoperative measurements obtained from the 3-D CT. Similarly, the supraorbital bar is located either inferiorly or superiorly to reduce or increase the height of the orbit (Figs. 46–11E and 46–13). A T-shaped LactoSorb (Biomet Microfixation, Jacksonville, FL) absorbable plate is utilized to rigidly fix the halves of the supraorbital bar. An 8-hole absorbable plate is fixed at the most lateral end of the supraorbital bar
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Figure 46–11 (A) Intraoperative photographs demonstrating the zigzag bicoronal incision at mid-vertex, (B) lateral view of the zig-zag bicoronal incision at mid-vertex, (C) the fused left coronal suture, (D) fol-
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lowing craniotomy and removal of the frontal bones, and (E) following removal of the fronto-orbital bar and remodeling of the frontal bones.
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Figure 46–12 Proposed sites of the osteotomy. 10.1055/978-1-60406-039-3c046_f012
(Fig. 46–14A). The supraorbital bar is advanced by 7 to 15 mm, depending on the preoperative 3-D-CT measurements. A tenon-and-mortise calvarial bone graft is inserted in the interval at the site of advancement. The posterior (dorsal) end of the absorbable plate is rigidly fixed using absorbable 1.5 mm screws (Fig. 46–14B). This method allows achievement of symmetrical orbits and supraorbital bar irrespective of the severity of the synostosis. Any narrowing present preoperatively at the pterion is corrected by radial osteotomy at the pterion and outfractures of the pterion. Each frontal bone is shaped by performing multiple radial osteotomies along the inferior and posterior borders (Fig. 46–12). Tessier bone benders (Lorenz Surgical, Jacksonville, FL) are used to correct the frontal bossing by either increasing or decreasing the convexity of the frontal bones. Once both frontal bones appear symmetrical in shape, they are placed over the supraorbital bar and rigidly fixed using absorbable 1.5 mm plates and screws (Fig. 46–14C). The temporalis muscle is advanced and reattached to the temporal bone utilizing absorbable sutures through holes created in the calvaria. This is essential to prevent an “hourglass” deformity of the calvaria. The scalp flap is replaced and symmetry is confirmed. A single 7 mm suction drain is placed underneath the scalp flap, and the wound is closed in layers using interrupted sutures of 4–0 Vicryl for the galea and continuous percutaneous rapidly absorbing Vicryl for the skin. A lightweight dressing and a head bandage complete the procedure. Traditionally, titanium plates or interosseus wires have been used to obtain rigid fixation. Recent studies have demonstrated that, as the calvaria continues to grow, the plates and wires migrate to come in close apposition with the dura and the brain. Absorbable plates provide rigid support for 3 to 6 months. The plates are reabsorbed in 9 to 12 months, eliminating the possibility of intracranial migration.
Figure 46–13 Method of correcting asymmetry of the orbits. (A) Preoperatively the left orbit is narrow and the left supraorbital rim is higher than the right. (B) The width of the left orbit is increased by insertion of a bone graft and its height is reduced by excision of bone at the left frontozygomatic suture. The right orbit is narrowed by excising a segment of bone. (C) Following remodeling, rigid fixation is achieved with absorbable plates. 10.1055/978-1-60406-039-3c046_f013
Postoperative Management Including Possible Complications Following extubation, the child is transferred to the pediatric intensive care unit for 24 to 48 hours. This allows close monitoring for level of consciousness and hemodynamic stability. Parents are warned that there will be considerable swelling of the scalp and periorbital contents that regresses within 3 days. It is not unusual for the child to develop pyrexia of 38°C for the first 72 hours. Continuing pyrexia and persistent swelling and cellulitis should be a source of concern and investigated. The hematocrit is maintained above 20. A perioperative 3-D CT is performed on the fifth postoperative day. This is used to accurately document the sites of osteotomy and allows the surgeons to confirm whether appropriate symmetry and ventral advancement were achieved intraoperatively. Following the CT, the child is discharged. Further follow-up is performed at 3 weeks, 6 weeks, 3 months, 6 months, and 1 year. Annual visits are scheduled until the age of 6 and every 2 to 3 years thereafter. Longi-
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Figure 46–14 (A) Intraoperative photographs with a detailed view of the fronto-orbital bar following remodeling and fixation with LactoSorb absorbable plates, (B) the fronto-orbital bar following its replacement
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and fixation with absorbable plates, and (C) following remodeling and replacement of the frontal bones. Note change in contour compared with the view in Fig. 46–11C.
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tudinal follow-up by a craniofacial team allows assessment of the disease and the procedure on the neuropsychological development and craniofacial growth of the child. MRI and 3-D CT are obtained 1 year following surgery to help document the ventral movement and symmetry of the orbits (Figs. 46–1B, 46–2B, 46–5B, 46–6B, 46–7B, 46–8B, 46–9B, and 46–10B).
Complications To reduce the incidence of mortality and morbidity, surgery should be performed in a children’s hospital with a pediatric anesthesiologist and pediatric intensive care facilities. Recent series have demonstrated only isolated cases of mortality. The common cause of mortality is insufficient intraoperative blood replacement. Blood loss should be minimized and replaced quickly.
The incidence of wound infection and dehiscence is extremely low. Cranial bone graft infection can be minimized significantly by administering a 48 hour prophylactic antibiotic regimen consisting of nafcillin and gentamicin. Continuing cerebrospinal fluid leakage is extremely rare if adequate precautions are taken to ensure proper closure of dural tears intraoperatively. Long-term follow-up may reveal asymmetries of the supraorbital bar and forehead. If these are minor, they can be addressed by using BoneSource (Leibinger Corp., Dallas, TX)/ Embark (Lorenz), a hydroxyapatite paste, by elevating the scalp flap and applying the paste to the surface of the calvaria. Persistent areas of incomplete ossification, which are larger than a centimeter in diameter, are similarly treated with the hydroxyapatite paste. Major asymmetries may necessitate a revision osteotomy and readvancement of the supraorbital bar.
Index
Page numbers followed by f or t denote material in figures or tables, respectively.
A Adherent catheters endoscopy for, 231, 237, 238f in shunt infection, 237, 238f AIDS, brain abscess in, 157, 159 Air embolism coronal synostosis and, 242, 257 metopic synostosis and, 290 total calvarial reconstruction and, 242 ventriculoatrial shunt and, 34 Amblyopia, orbital malposition and, 27 Aminoglycosides, for shunt infection, 235t Amphotericin B, for shunt infection, 235t Ampicillin, for shunt infection, 235t Anencephaly, 251 Angiography of anterior cranial base encephalocele, 71 of craniopagus twins, 209, 211f, 213 of craniovertebral junction abnormalities, 20, 21f, 26 of moyamoya syndrome, 171, 175–176, 176f Anorectal atresia, tethered spinal cord with, 62 Anterior cranial base encephaloceles, 69–75 differential diagnosis of, 70–71 postoperative management of, 73–74 radiologic findings of, 71 surgery for closure in, 72–73 complications of, 73–74 craniotomy in, 71–72, 71f extradural approach in, 71–73, 72f–73f intradural approach in, 71, 73, 75f isolation, ligation, and transection in, 72, 73f–74f outcome of, 74 patient positioning for, 71, 71f preoperative preparation for, 70–71 procedure for, 71–73 skin incision in, 71, 71f transcranial approach in, 71 transnasal approach in, 71 transnasal removal in, 72, 75f Anterior longitudinal ligament, in transoral surgery, 22 Anteroposterior dystopia, 27 Antibiotics, postoperative in brain abscess, 162 in coronal synostosis, 311 in craniovertebral junction abnormalities, 25 in exorbitism, 81 in fibrous dysplasia, 6 in hypertelorism, 93 in metopic synostosis, 290 in orbital dystopia, 93 Antibiotics, preoperative in anterior cranial base encephaloceles, 71 in brain abscess, 159 in Chiari I malformations, 7 in coronal synostosis, 257, 308 in hypertelorism, 89
in lambdoid synostosis, 185, 190 in meningocele, 253 in metopic synostosis, 298–299 in myelomeningocele, 96 in orbital dystopia, 89 in orbital malposition, 27, 89 in pansynostosis, 51, 57 in plagiocephaly, 166 in split cord malformations, 142 in ventricular endoscopy, 216, 229 in ventriculoperitoneal shunting, 104–105 Antibiotic therapy, for shunt infection, 233, 235, 235t Anticonvulsants in anterior cranial base encephaloceles, 71 in brain abscess, 159, 162 in occipital encephaloceles, 43 in orbital malposition, 27 in pansynostosis, 50 Antiplatelet agents, for moyamoya syndrome, 171–172 Apert’s syndrome, 13, 76, 256 Apnea Chiari II malformation and, 10 craniovertebral junction abnormalities and, 20 Arachnoid cyst endoscopy for, 224, 230–231 growing skull fracture and, 41 ventriculoatrial shunt for, 34 Arachnoiditis with myelomeningocele, 97, 99f with posterior fossa decompression, 285 Aspergillus, and brain abscess, 158 Aspirin, for moyamoya syndrome, 171–172 Astrocytoma, 276 Atlas, in transoral surgery, 22, 23f–24f
B Backhead, in calvarial reconstruction, 186–187, 186f Bacteroides, and brain abscess, 158 Bandeaus for coronal synostosis, 259–261, 260f–261f for lambdoid synostosis, 186–187, 186f–188f for pansynostosis, 52f–56f, 53–57, 58f–60f for plagiocephaly, 165, 167–168, 167f–169f for total calvarial reconstruction, 244–246, 245f Band therapy, for lambdoid synostosis, 197 Basal encephaloceles, 69–75, 70f clinical presentation of, 70 operative procedure for, 71–73 Basilar artery, in third ventriculostomy, 232 “Beaten metal” appearance, of pansynostosis, 50 Bladder dysfunction lipomyelomeningocele and, 65, 68, 147, 269, 274 split cord malformations and, 128 tethered spinal cord and, 62–64, 136–137 Bladder emptying, for ventriculoperitoneal shunting, 105 Blindness, fibrous dysplasia and, 1 “Boat-shaped” skull, 203
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Index
Bowel function lipomyelomeningocele and, 68 tethered spinal cord and, 62, 136–137 Brachycephaly, 13, 241, 242f, 249, 256 Brain abscess clinical presentation of, 158–159 contiguous spread of, 157, 158f CSF analysis in, 159 definition of, 157 epidemiology of, 157 excision of, 159–161, 163f hematogenous spread of, 157, 158f laboratory evaluation of, 159 needle aspiration of, 159–161, 161f, 163f pathogens causing, 158 postoperative management of, 162–164 radiologic findings of, 159, 160f, 162 risk factors for, 157 stages of, 157, 159, 164 surgical management of, 157–164 corticectomy in, 161, 162f–163f cottonoid use in, 161, 163f vs. medical treatment, 159 outcomes of, 162–164 patient positioning for, 161 patient selection for, 158–159 preoperative preparation for, 159 procedure of, 159–161 ultrasound guidance in, 161, 161f–162f traumatic/iatrogenic, 157–158, 158f vectors for, 157, 158f Brain injury metopic synostosis surgery and, 290 total calvarial reconstruction and, 249 Brain stem glioma(s) clinical presentation of, 276 displacement by, 275, 275f exophytic, 275–276, 279 focal, 275–276, 278–279 laboratory workup for, 276 magnetic resonance imaging of, 275–276 postoperative management of, 280 prognosis of, 275 surgical treatment of, 275–280 anesthesia for, 276 cerebellar vermis splitting in, 278, 279f closure in, 279–280 complications of, 280 craniotomy for, 277, 277f dural opening in, 277, 278f–279f hemodynamic monitoring in, 276 laser use in, 278 magnification in, 278 neurophysiological monitoring in, 279 patient positioning for, 276, 277f patient selection for, 275–276 preoperative preparation for, 276 procedure for, 276–280 skin incision for, 277, 277f tumor exposure in, 278, 279f tumor resection in, 278–279, 280f
C Calcium channel blockers, for moyamoya syndrome, 171 Caldwell-Luc incision, in hypercanthorum, 28, 29f Calvarial bone graft for coronal synostosis, 260 for exorbitism, 76, 78, 80f for fibrous dysplasia, 1–2, 5, 5f–6f for hypercanthorum, 28, 31f for telorbitism, 32 Calvarial reconstruction for lambdoid synostosis, 184–189 blood loss in, 185 complications of, 189
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craniotomy in, 186–187, 186f–188f operating room setup for, 185 patient positioning for, 185, 185f patient selection for, 184–185 postoperative management of, 189 preoperative preparation for, 185, 185f procedure for, 186–188 skin incision for, 186 “sunrise” appearance in, 186, 188f tiara in, 187, 187f–188f total, for coronal synostosis, 241–250 anesthesia for, 242 blood loss in, 249 closure in, 246–247 complications of, 249 draping in, 244, 245f exposure in, 244, 245f final recontouring in, 246, 248f height reduction in, 246, 248f intraoperative monitoring in, 242, 247 occipital advancement in, 246, 247f orbital advancement in, 244–246, 246f outcome of, 249 patient positioning for, 243–244, 243f patient selection for, 241 postoperative management of, 249 preoperative preparation for, 242 skin incision in, 244, 245f specialized instrumentation for, 247–249 timing of, 241, 249–250 Candida, and shunt infection, 235, 235t Canthopexy in coronal synostosis, 256–260 in hypercanthorum, 28 in hypertelorism, 94 in orbital dystopia, 91, 93f, 94 in telorbitism, 32, 91, 93f Carbon dioxide laser, in endoscopy, 229 Cardiac rupture, ventriculoatrial shunt and, 34 Cardiac tamponade, ventriculoatrial shunt and, 34 Carotid arteries, in moyamoya syndrome, 171 Cauda equina, in selective dorsal rhizotomy, 179, 179f Cefotaxime, for shunt infection, 235t Ceftazidime, for shunt infection, 235t Ceftriaxone, for shunt infection, 235t Cephalosporins, for shunt infection, 235, 235t Cerebellar abscess, 157 Cerebellar tonsils, in Chiari I malformation, 7–10 Cerebellar vermis, splitting in glioma surgery, 278, 279f Cerebral abscess. See Brain abscess Cerebral edema growing skull fracture and, 40 orbital malposition and, 32 Cerebral palsy, spastic radiologic findings of, 177 selective dorsal rhizotomy for, 177–183 cauda equina localization in, 179, 179f complications of, 183 conus medullaris localization in, 177–180, 179f dorsal root identification in, 181 dorsal root sectioning in, 181–183, 182f dorsal root separation in, 180f, 181 electromyography in, 177–178, 178f, 180–183, 182f, 183t indications for, 177t laminectomy in, 177–180, 180f patient positioning for, 178, 178f patient selection for, 177–178 postoperative management of, 183 preoperative preparation for, 178 procedure for, 178–183 skin incision in, 179 standard technique for, 177 ultrasound guidance in, 179, 179f Cerebral pontine angle, endoscopic approach to, 224 Cerebritis, and brain abscess, 157, 159
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Index 315 Cerebromeningeal cicatrix, with growing skull fracture, 40–41, 42f Cerebrospinal fistula, encephalocele surgery and, 73–74 Cerebrospinal fluid analysis in brain abscess, 159 in shunt infection, 234–235, 234f, 237 in ventricular endoscopy, 216–217 Cerebrospinal fluid buildup. See Hydrocephalus Cerebrospinal fluid leaks with brain abscess, 157 with Chiari I malformations, 8 with coronal synostosis, 19, 170, 249, 261 with craniovertebral junction abnormalities, 25–26 with exorbitism, 80 with fibrous dysplasia, 6 with filum terminale sectioning, 141 with hypertelorism, 90, 92–93 with lambdoid synostosis, 189 with lipomyelomeningocele, 147, 273–274 with lumbosacral meningoceles, 255 with metopic synostosis, 288, 303 with orbital dystopia, 90, 92–93 with orbital malposition, 27, 32, 90 with pansynostosis, 53, 61 with plagiocephaly, 170 with posterior fossa decompression, 285 with sagittal synostosis, 295 with split cord malformations, 128, 267 with tethered spinal cord, 152–154, 264, 267 with ventriculoperitoneal shunting, 110 Cervical meningocele, 251 Cervical traction, in craniovertebral junction surgery, 21–22, 25–26 Cervicomedullary tumors, 275 Chiari malformations, 7–12 Chiari 0, 7 Chiari I, 7–10 difficult cases of, 112–114, 114f lipomyelomeningocele with, 64 neurologic signs of, 111 posterior fossa decompression for, without duraplasty, 281–285 closure in, 282–285 complications of, 285 contraindications to, 281 craniotomy in, 281, 283f dural band incision in, 281–282, 283f follow-up care in, 285 intraoperative ultrasound in, 281–282, 284f, 285 patient positioning for, 281 patient selection for, 281 postoperative management of, 285 preoperative preparation for, 281 procedure for, 281–285 skin incision in, 281 special equipment for, 281 surgical suite setup for, 281, 282f tonsillar pistoning in, 282, 284f postoperative management of, 9–10, 112–114 radiologic findings of, 7, 9, 111, 114, 114f, 285 secondary decompression for, 9–10 surgery for, 111–115. See also specific procedures anesthesia for, 7 closure in, 8 complications of, 9–10 laminectomy in, 112, 115 patient positioning for, 7, 8f patient selection for, 7, 111 preoperative preparation for, 7, 111 procedure for, 7–8, 9f, 111–112 skin incision for, 7–8, 9f, 111, 112f syringoperitoneal shunting for, 112, 113f, 114–115 syringosubarachnoid shunting for, 112, 113f Chiari II, 7 age-specific symptoms and signs of, 10
14535IDX.indd 315
postoperative management of, 12 risk-benefit ratio in, 12 surgery for complications of, 12 controversy over, 10 incision and exposure in, 10, 11f patient positioning for, 10 patient selection for, 10–12 preoperative preparation for, 10 procedure for, 11–12, 11f with coronal synostosis, 257 with pansynostosis, 50 Chloramphenicol, for shunt infection, 235t Choroid plexus, in Chiari II malformation, 11 Cleft cord, 116 Clivus, in transoral surgery, 22–26, 23f–24f Cloverleaf deformity, 52f Colloid cyst aspiration of, 231 endoscopy for, 217, 218f, 222–223, 231–232, 231f standard surgical treatment of, 231 Common facial vein, open access for ventriculoatrial shunt, 36–37, 37f Computed tomography of anterior cranial base encephalocele, 71 of brain abscess, 159, 162 of Chiari I malformation, 111 of coronal synostosis, 165, 241–242, 242f, 256–257, 305–306, 305f–308f, 310–311 of craniopagus twins, 209, 210f, 213 of craniovertebral junction abnormalities, 20 of Dandy-Walker malformation, 104 of exorbitism, 77 of fibrous dysplasia, 2 of filum dysgenesis, 267 of growing skull fracture, 40–41 of hemimyelomeningocele, 100f of hypertelorism, 88, 88f, 94f, 95 of lambdoid synostosis, 190, 194, 196f–197f, 201 of lipomyelomeningocele, 64–65, 147 of metopic synostosis, 296–297, 296f–297f, 298, 302, 302f of occipital encephaloceles, 43 of orbital dystopia, 88, 88f of pansynostosis, 50, 52f, 53, 61 of plagiocephaly, 165, 194, 196f–197f, 201 of sagittal synostosis, 203–204, 291, 294 of split cord malformations, 142 of tethered spinal cord, 62, 152, 267 in ventricular endoscopy, 215 of ventriculoatrial shunt, 39 of ventriculoperitoneal shunt, 153–154, 234 Computed tomography myelogram of meningocele, 252 of myelomeningocele, 102f of split cord malformations, 119, 124f, 142 Congenital cyanotic heart disease (CCHD), brain abscess with, 157, 159 Conjoined twins epidemiology of, 209 separation of, 209–214 Conus medullaris in selective dorsal rhizotomy, 177–180, 179f tethered spinal cord and, 62–63 “Copper-beaten” appearance, in intracranial hypertension, 13 Coronal synostosis, 13–19, 165–170, 256–261 artist’s rendering of, 166f bilateral, 13, 15f, 256 challenges of, 241 craniofacial reconstruction in, 17–18, 18f, 241–250, 259–261 craniotomy in, 17–18, 18f brachycephaly with, 13, 241, 242f, 249, 256 compensatory growth in, 13, 14f–15f, 165, 166f, 241, 256, 304 definition of, 13 diagnosis of, 305 differential diagnosis of, 256
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Coronal synostosis, (continued) etiology of, 304 genetics of, 13, 256, 261, 305 individualized treatment for, 241 multidisciplinary approach to, 241–242 ophthalmologic exam in, 13 plate-and-screw fixation in, 17, 17f, 19, 167–170, 167f, 169f, 261, 308–310 postoperative management of, 19, 170, 261, 310–311 radiologic findings of, 165, 241–242, 242f, 256–257, 305–306, 305f–308f, 310–311 recurrence or relapse of, 17, 19 surgery for, 13–19, 165–170, 256–261, 304–311. See also specific procedures blood loss in, 13–14, 19, 166, 170, 249, 257–258, 308 closure in, 19, 168–170, 260–261 complications of, 19, 170, 261, 310–311 craniotomy in, 167–168, 167f–168f, 259, 259f flap elevation in, 14–15, 166–167 follow-up in, 311 indications for, 13 osteotomies in, 15–16, 16f, 167, 168f, 259, 308, 309f–310f outcome of, 307f patient positioning for, 14, 17, 17f, 166, 258, 308 patient selection for, 13, 165, 256–257, 304 preoperative preparation for, 13–14, 165–166, 257 procedure for, 14–19, 166–170, 258–261, 308–310 risks of, 257 skin incision in, 14–15, 166–167, 258, 258f, 308 specialized instrumentation in, 19, 170, 261 supraorbital bar advancement in, 306, 308–310, 311f timing of, 13, 165, 241, 249–250, 304–305 syndromic vs. nonsyndromic, 13, 304 total calvarial reconstruction for, 241–250 anesthesia for, 242 blood loss in, 249 closure in, 246–247 complications of, 249 draping in, 244, 245f exposure in, 244, 245f final recontouring in, 246, 248f height reduction in, 246, 248f intraoperative monitoring in, 242, 247 occipital advancement in, 246, 247f orbital advancement in, 244–246, 246f outcome of, 249 patient positioning for, 243–244, 243f patient selection for, 241 postoperative management of, 249 preoperative preparation for, 242 skin incision in, 244, 245f specialized instrumentation for, 247–249 timing of, 241, 249–250 turricephaly with, 13, 241, 242f, 249, 256 unilateral, 13, 14f, 165–170, 256, 304–311, 304f–305f craniofacial reconstruction in, 15–16, 16f, 167–168, 167f– 169f, 259–261, 306–310 craniotomy in, 15–17, 16f, 167–168, 167f–168f Corticectomy, for brain abscess, 161, 162f–163f Costochondral bone graft, for hypercanthorum, 28, 31f Cranial base encephaloceles, 69 anterior, 69–75 differential diagnosis of, 70–71 postoperative management of, 73–74 radiologic findings of, 71 surgery for closure in, 72–73 complications of, 73–74 craniotomy in, 71–72, 71f extradural approach in, 71–73, 72f–73f intradural approach in, 71, 73, 75f isolation, ligation, and transection in, 72, 73f–74f outcome of, 74 patient positioning for, 71, 71f preoperative preparation for, 70–71
14535IDX.indd 316
procedure for, 71–73 skin incision in, 71, 71f transcranial approach in, 71 transnasal approach in, 71 transnasal removal in, 72, 75f Cranial vault encephaloceles, 69 Cranial vault reconstruction, total, 204–208, 291–295 anesthesia for, 204 blood loss in, 204, 206, 208, 292, 294–295 bone plate recontouring in, 206, 207f closure in, 293–294 complications of, 208, 294–295 craniofacial reconstruction in, 204–208, 207f, 293, 293f–294f craniotomy in, 204–205, 205f, 293, 293f–294f draping for, 204 flap elevation in, 293 indications for, 292 outcome of, 207f, 208 patient positioning for, 204, 204f, 292–293 patient selection for, 203, 291–292 preoperative preparation for, 204, 292 procedure for, 204–208, 292–294 skin incision for, 204, 204f, 293 surgical setup for, 292–293 timing of, 203, 292 Craniectomy, endoscopic-assisted, for lambdoid synostosis, 190–192 closure in, 191–192 complications of, 192 helmet use after, 192, 192f metallic markers for, 190, 190f operative technique for, 191–192, 191f–192f outcome of, 193f patient positioning for, 190, 190f patient selection for, 190 postoperative management of, 192 preoperative preparation for, 190 procedure for, 190–192 skin incision for, 190–191, 191f Craniofacial complex, fibrous dysplasia of, 1–6 Craniofacial reconstruction. See also specific procedures in coronal synostosis bilateral, 17–18, 18f, 241–250, 259–261 unilateral, 15–16, 16f, 167–168, 167f–169f, 259–261, 306–310 in craniopagus twins, 210, 211f, 212, 213f in fibrous dysplasia, 5, 5f–6f in metopic synostosis, 287–288, 288f, 299–302, 301f–303f in pansynostosis, 52f, 53–57, 54f–56f, 58f–60f in plagiocephaly, 167–168, 167f–169f in sagittal synostosis, 204–208, 207f, 293, 293f–294f Craniopagus twins classification of, 209 epidemiology of, 209 frontal, 209 occipital, 209 parietal, 209 photograph of, 209f radiologic studies of, 209, 210f–211f separation of, 209–214 challenge of, 214 closure in, 212, 213f complications of, 213 craniofacial reconstruction in, 210, 211f, 212, 213f craniotomy in, 212, 212f dural graft in, 212, 212f dural opening in, 212 main questions in, 209 mortality and morbidity in, 209, 214 outcome of, 214, 214f patient positioning for, 210 patient selection for, 209 plate-and-screw fixation in, 212, 213f postoperative management of, 213 preoperative embolization for, 209 preoperative preparation for, 209–210
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Index 317 preoperative tissue expanders for, 210, 211f procedure for, 210–212 skin incision for, 210, 211f–212f shared sagittal sinus in, 209, 210f– 212f, 212–214 shared vascular anatomy of, 209–210, 210f–211f temporoparietal, 209 vertical, 209 Craniosynostosis. See also specific types coronal, 13–19, 165–170, 256–261, 304–311 artist’s rendering of, 166f bilateral, 13, 15f, 256 brachycephaly with, 13, 241, 242f, 249, 256 compensatory growth in, 13, 14f–15f, 165, 166f, 241, 256, 304 definition of, 13 diagnosis of, 305 differential diagnosis of, 256 etiology of, 304 genetics of, 13, 256, 261, 305 genetic testing in, 13 individualized treatment for, 241 multidisciplinary approach to, 241–242 ophthalmologic exam in, 13 plate-and-screw fixation in, 17, 17f, 19, 167–170, 167f, 169f, 261, 308–310 postoperative management of, 19, 170, 261, 310–311 radiologic findings of, 165, 241–242, 242f, 256–257, 305–306, 305f–308f, 310–311 recurrence or relapse of, 17, 19 surgery for, 13–19, 165–170, 256–261 syndromic vs. nonsyndromic, 13, 304 total calvarial reconstruction for, 241–250 turricephaly with, 13, 241, 242f, 249, 256 unilateral, 13, 14f, 165–170, 256, 304–311, 304f–305f lambdoid calvarial reconstruction for, 184–189 deformity with, 184, 184f–185f endoscopic assisted craniectomy for, 190–192 vs. nonsynostotic plagiocephaly, 184, 194, 197 posterior plagiocephaly with, 194–202 metopic, 286–290, 296–303 cognitive impairment with, 286 compensatory growth in, 286, 288f, 296 definition of, 286 diagnosis of, 286, 296–297, 297f etiology of, 296, 298 multidisciplinary approach to, 297–298 ophthalmologic exam in, 286, 297–298 postoperative management of, 289–290, 302–303 radiologic findings of, 286, 296–297, 296f–297f, 298, 302, 302f referring pediatrician and, 298 relapse or recurrence of, 290 skull deformity in, 286, 288f, 296–297, 296f–297f multiple suture (pansynostosis), 50–61 clinical signs of, 50 hydrocephalus with, 50, 61 postoperative management of, 57–61 radiologic findings in, 50 “thumbprinting” appearance of, 50, 52f, 53, 54f sagittal, 203–208, 291–295 compensatory growth in, 291, 291f, 292, 295 definition of, 203 diagnosis of, 291 intracranial hypertension with, 291–292 intraoperative photograph of, 206f in males vs. females, 203 multidisciplinary approach in, 204 vs. positional deformity, 203 postoperative management of, 208, 294–295 radiologic findings of, 203–204, 291 relapse of, 295 skull deformity in, 203, 291, 291f, 295 Craniotomy. See also specific procedures and disorders for anterior cranial base encephalocele, 71–72, 71f
14535IDX.indd 317
for brain stem glioma, 277, 277f for coronal synostosis, 167–168, 167f–168f bilateral, 17–18, 18f unilateral, 15–17, 16f for craniopagus twin separation, 212, 212f for exorbitism, 78, 79f for fibrous dysplasia, 3–5, 4f for growing skull fracture, 41, 41f for hypertelorism, 28, 29f, 90–91, 91f–93f for lambdoid synostosis, 186–187, 186f–188f for metopic synostosis, 287, 288f, 299, 299f for orbital dystopia, 90–91, 91f–93f for orbital malposition, 28, 29f for plagiocephaly, 167–168, 167f–168f, 199–201, 200f for posterior fossa decompression, 281, 283f for sagittal synostosis, 204–205, 205f, 293, 293f–294f for telorbitism, 32, 33f Craniovertebral junction abnormalities cerebrospinal fluid leak with, 25 co-morbidity assessment in, 20–21 direction of encroachment in, 20 intradural extension of tumor with, 25 magnetic resonance imaging of, 20, 21f, 26 postoperative management of, 25–26 radiologic findings of, 20 reducible vs. irreducible, 20 transoral surgery for, 20–26, 22f cervical traction for, 21–22, 25–26 delayed complications of, 26 dental hygiene and, 20 endotracheal intubation in, 21–22, 25 nasogastric feeding tube in, 24–25, 25f nutritional status and, 20 oral cavity entrance and, 21 oropharyngeal/nasal cultures before, 21 patient positioning for, 21–22 patient selection for, 20 perioperative complications of, 26 preoperative preparation for, 20 procedure for, 21–25 special circumstances in, 24–25 tracheostomy in, 20–21 transpalatal route in, 24–25 C-reactive protein, brain abscess and, 159 Credé maneuver, for ventriculoperitoneal shunting, 105 Crouzon’s syndrome, 13, 76, 81f, 82, 256 Cruciate ligament, in transoral surgery, 24, 24f CT. See Computed tomography Currarino’s triad, 251 Cystolipomyelomeningocele, 68f
D Dandy, Walter Edward, 227 Dandy-Walker malformation, 104–110 artist’s depiction of, 105f characteristics of, 104 meningocele with, 251 radiologic findings of, 104, 106f shunt for vs. reestablishment of patency, 104 ventriculoatrial, 104 ventriculoperitoneal, 104–110 complications of, 109–110 connections of, 107, 108f CSF leakage around, 110 intra-abdominal injury with, 110 operative procedure for, 105–109 patient positioning for, 105, 107f patient selection for, 104 peritoneal catheter placement in, 108–109 positioning of, 106f postoperative management of, 109–110 preoperative preparation for, 104–105 selection of equipment, 104 skin closure in, 109
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318
Index
Dandy-Walker malformation, (continued) skin incision for, 106, 107f surgical isolation bubble for, 106–107, 107f surgical technique for, 106–109 ventricular catheter placement in, 106–108, 109f Dead space, pansynostosis surgery and, 61 Dental abscess, brain abscess with, 157, 160f Dental guards, in transoral surgery, 22, 25 Dental hygiene, and transoral approach, 20 Depressed skull fractures, in infants, 83–87 conservative approach to, 83 vs. in older age groups, 83 “Ping-Pong” appearance of, 83, 84f postoperative management of, 87 surgery for anesthetic considerations in, 83 patient positioning for, 83, 84f patient selection for, 83 periosteal elevator use in, 83, 85f–86f preoperative preparation for, 83 procedure for, 83–85 risks of, 83, 87 skin incision for, 83, 85f Depth perception, orbital malposition and, 27 Dermal sinus tract, with split cord malformation, 126, 127f Dermoid cyst, with split cord malformation, 126, 127f Dermoid tumor, inclusion, with myelomeningocele, 97, 99f, 100 Diastematomyelia, 97, 100f, 116. See also Split cord malformations Diffusion-weighted imaging (DWI), of brain abscess, 159 Dingman mouth retractor, in transoral surgery, 22, 23f–24f Diplomyelia, 116. See also Split cord malformations Diplopia fibrous dysplasia and, 1 orbital malposition and, 27 Distraction osteogenesis, for exorbitism, 81–82, 81f Dorsal rhizotomy, selective, 177–183 cauda equina localization in, 179, 179f complications of, 183 conus medullaris localization in, 177–180, 179f dorsal root identification in, 181 dorsal root sectioning in, 181–183, 182f dorsal root separation in, 180f, 181 electromyography in, 177–178, 178f, 180–183, 182f, 183t indications for, 177t laminectomy in, 177–180, 180f patient positioning for, 178, 178f patient selection for, 177–178 postoperative management of, 183 preoperative preparation for, 178 procedure for, 178–183 skin incision in, 179 standard technique for, 177 ultrasound guidance in, 179, 179f Dystopia, orbital, 88–95, 89f anteroposterior, 27 definition of, 88 postoperative management of, 93–94 radiologic findings of, 88, 88f rotatory, 27 surgery for, 88–95 blood loss in, 89 closure in, 92 complications of, 93–94 craniofacial osteotomies in, 90–91, 91f–93f draping for, 89 flap elevation in, 89–90, 90f patient positioning for, 89 preoperative evaluation for, 88–89 preoperative preparation for, 89 procedure for, 89–95 skin incisions for, 89 vertical, 27
E Electrocardiogram (EKG), in ventriculoatrial shunting, 35, 37–39
14535IDX.indd 318
Electromyography (EMG) in selective dorsal rhizotomy, 177–178, 178f, 180–183, 182f, 183t in split cord malformations, 119, 148 in tethered cord surgery, 263 Encephaloceles basal, 69–75, 70f clinical presentation of, 70 operative procedure for, 71–73 contents of sac, 69 cranial base, 69 cranial base, anterior, 69–75 differential diagnosis of, 70–71 postoperative management of, 73–74 radiologic findings of, 71 surgery for closure in, 72–73 complications of, 73–74 craniotomy in, 71–72, 71f extradural approach in, 71–73, 72f–73f intradural approach in, 71, 73, 75f isolation, ligation, and transection in, 72, 73f–74f outcome of, 74 patient positioning for, 71, 71f preoperative preparation for, 70–71 procedure for, 71–73 skin incision in, 71, 71f transcranial approach in, 71 transnasal approach in, 71 transnasal removal in, 72, 75f cranial vault, 69 definition of, 69 derivation of term, 69 frontoethmoidal, 69–75, 70f clinical presentation of, 70 operative procedure for, 71––73 types of, 69 nasoethmoidal, 69, 70f nasofrontal, 69, 70f naso-orbital, 69, 70f occipital, 43–49, 69 location of, 43 postoperative management of, 48–49 size range of, 43 skin coverage of, 43 surgery for anesthetic technique for, 43 complications of, 48–49 draping in, 44 dural/periosteal closure in, 45–46, 47f forceps use in, 44, 45f neural tissue management in, 44–45, 46f orbit protection in, 43, 44f patient positioning for, 43, 44f patient selection for, 43 preoperative preparation for, 43 procedure for, 43–48 scissor use in, 44, 45f skin closure in, 46–47, 48f–49f timing of, 43 sphenoethmoidal, 69 sphenomaxillary, 69 spheno-orbital, 69 sphenopharyngeal, 69 terminology describing, 69 transethmoidal, 69 Encephaloduroarteriosynangiosis (EDAS), 171 Encephalomalacia, with growing skull fracture, 40–41 Endocarditis, brain abscess with, 157 Endoscopic-assisted craniectomy, for lambdoid synostosis, 190–192 closure in, 191–192 complications of, 192 helmet use after, 192, 192f metallic markers for, 190, 190f
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Index 319 operative technique for, 191–192, 191f–192f outcome of, 193f patient positioning for, 190, 190f patient selection for, 190 postoperative management of, 192 preoperative preparation for, 190 procedure for, 190–192 skin incision for, 190–191, 191f Endoscopic third ventriculostomy, 230, 230f, 232 Endoscopy, ventricular, 227–232 for adherent catheters, 231, 237, 238f anesthesia for, 216, 229 approaches in, 215–226 to anterior third ventricle, 217–218, 219f–220f to foramen of Monro, 217, 217f–218f to frontal horn, 222–223, 222f–223f to occipital horn, 223–224, 224f–225f to posterior fossa, 224–225, 225f to posterior third ventricle, 218–220, 220f–221f to temporal horn, 223, 223f–224f for biopsy and treatment of tumors, 231–232 bleeding in, 225 for colloid cyst, 217, 218f, 222–223, 231–232, 231f complications of, 225–226, 232 corporate interest in, 215 CSF analysis in, 216–217 flexible, 216, 227–229, 228f general principles of, 216–217 history of, 227 for hydrocephalus, 215, 230–231, 230f imaging studies for, 215, 230 instrumentation for, 215, 227–229, 228f–229f irrigation for, 215–216, 229 lasers used in, 223, 229 learning curve for, 225 patient positioning for, 217, 222f, 223, 224f, 229 pneumatic systems in, 216, 217f postoperative management in, 225–226, 232 preoperative preparation for, 215–216, 229 procedure for, 216–225, 229–232 rigid, 216, 227–229, 228f for shunt infection, 237–238, 238f, 240 skin incision for, 216, 229 for suprachiasmatic cyst, 217, 217f, 218, 220f surgeon disorientation in, 232 surgical suite organization for, 215 training for, 215, 225, 232 Enophthalmos, orbital malposition and, 27, 32 Enterococcus, and shunt infection, 235, 235t Epidermoid tumor, inclusion, with myelomeningocele, 97, 99f, 100 Erythrocyte sedimentation rate (ESR), brain abscess and, 159 Escherichia coli, and shunt infection, 235t Exophthalmos. See Proptosis Exorbitism postoperative management of, 81–82 radiologic findings of, 77 surgical correction of, 32, 76–82 blood loss in, 77, 81 calvarial bone graft for, 76, 78, 80f closure in, 80–81 complications of, 81 craniofacial osteotomies in, 78, 79f distraction osteogenesis with, 81–82, 81f draping for, 77 flap elevation in, 77–78 fronto-orbital advancement for, 76 midface advancement for, 76 monoblock advancement for, 76 patient positioning for, 77 patient selection for, 76–77 preoperative evaluation for, 76–77 preoperative preparation for, 77 procedure for, 77–81 results of, 81, 81f
14535IDX.indd 319
rib graft for, 78, 80f skin incisions in, 77–78 views of patient with, 76f External ventricular drain (EVD), in shunt infection, 235–238, 236f–237f, 240 Extraocular muscles, orbital malposition and, 27, 32 Eyeballs, displacement of. See Exorbitism; Proptosis Eyelid swelling with coronal synostosis surgery, 19 with sagittal synostosis surgery, 294
F Facial vein, common, open access for ventriculoatrial shunt, 36–37, 37f False aneurysm, postoperative, in craniovertebral junction abnormalities, 26 FBN mutations, 256 FGFR mutations, 256, 261 Fibrous dysplasia, of craniofacial complex, 1–6 clinical presentation of, 1, 1f monostotic, 1 pathology of, 1 polyostotic, 1 postoperative management of, 6 radiologic findings of, 1–2 surgery for blood loss in, 2 calvarial bone graft in, 1–2, 5, 5f–6f closure in, 6 complications of, 6 craniofacial reconstruction in, 5, 5f–6f craniotomy in, 3–5, 4f draping in, 3 dysplastic bone removal in, 1, 3–4, 4f dysplastic bone reuse in, 6 flap elevation in, 3 frontal sinus repair in, 5–6 helpful hints for, 4–5 implant avoidance in, 1 optic nerve decompression in, 1 patient evaluation for, 1 patient positioning for, 2–3, 2f pericranial tissue repair in, 5–6 preoperative preparation for, 2 principles of, 1 procedure for, 2–6 skin incision in, 3 temporalis muscle in, 3, 6 visual testing in, 2 “worst case scenario,” 1 Filum terminale dysgenesis of, 262, 267–268 sectioning of, 136–141, 254f, 255, 267–268 anatomy in, 267 anesthetic considerations in, 137 bipolar coagulation in, 138–141, 140f closure in, 140f, 141, 267–268 complications of, 141 dural opening in, 138, 139f laminectomy in, 138, 138f patient positioning for, 137, 137f patient selection for, 136–137 pearls and pitfalls in, 268 postoperative management of, 141, 268 preoperative preparation for, 137 procedure for, 137–141, 267–268 prognosis in, 141 skin incision for, 138, 138f, 267, 268f technique of, 138–141, 138f–140f thickened with meningocele, 251, 254f with myelomeningocele, 97, 98f, 100f with split cord malformations, 122f, 125 with tethered spinal cord, 62–63, 64f, 136–141, 262, 267–268
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320
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Flat capillary hemangioma, with tethered spinal cord, 62 Flexible endoscopes, 216, 227–229, 228f Fluoroscopy, intraoperative, in ventriculoatrial shunting, 35–39 Folate, and neural tube defects, 251 Foramen of Monro, endoscopic approach to, 217, 217f–218f Forceps, endoscopic, 215, 229, 229f FRFR mutations, 256 Frontal horn, endoscopic approach to, 222–223, 222f–223f Frontal sinus repair, in fibrous dysplasia, 5–6 Frontoethmoidal encephaloceles, 69–75, 70f clinical presentation of, 70 operative procedure for, 71–73 types of, 69 Fronto-orbital advancement for coronal synostosis, 241–250, 256–261 for exorbitism, 76 for total calvarial reconstruction, 241–250, 243f Fungal infection brain abscess with, 158 shunt infection with, 235, 235t “Funnel-like” appearance, of distal conus, 62 Furstenberg test, 70
G Ganglioglioma, 276 Gentamicin, for shunt infection, 235t Glioma(s) brain stem clinical presentation of, 276 displacement by, 275, 275f exophytic, 275–276, 279 focal, 275–276, 278–279 laboratory workup for, 276 magnetic resonance imaging of, 275–276 postoperative management of, 280 prognosis of, 275 surgical treatment of, 275–280 anesthesia for, 276 cerebellar vermis splitting in, 278, 279f closure in, 279–280 complications of, 280 craniotomy for, 277, 277f dural opening in, 277, 278f–279f hemodynamic monitoring in, 276 laser use in, 278 magnification in, 278 neurophysiological monitoring in, 279 patient positioning for, 276, 277f patient selection for, 275–276 preoperative preparation for, 276 procedure for, 276–280 skin incision for, 277, 277f tumor exposure in, 278, 279f tumor resection in, 278–279, 280f nasal, vs. encephalocele, 70–71 Glomerulonephritis, immune complex, ventriculoatrial shunt and, 34, 39 Glossopharyngeal nerve, craniovertebral junction abnormalities and, 20 Grasping forceps, endoscopic, 215, 229, 229f “Ground glass” appearance, of fibrous dysplasia, 1 Growing skull fracture, 40–42 clinical presentation of, 40 common sites for, 40 incidence of, 40 postoperative management of, 42 radiological studies of, 40–41 risk factors for, 40 surgery for bipolar cautery in, 41, 42f complications of, 42 dural closure in, 41–42, 42f goal of, 41 indications for, 41
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procedure for, 41–42, 41f–42f venous sinuses in, 42
H Haemophilus influenzae, and shunt infection, 235t Hard palate, in transoral surgery, 22–26, 23f–24f “Harlequin eyes,” 53, 166f Headache brain abscess and, 158 Chiari I malformation and, 111 fibrous dysplasia and, 1 moyamoya syndrome and, 171 tethered cord surgery and, 135 Height reduction, for total calvarial reconstruction, 243f, 246, 248f Helmet use for coronal synostosis, 257 for lambdoid synostosis, 192, 192f, 197 for posterior plagiocephaly, 197 for sagittal synostosis, 292 Hemangioma, flat capillary, with tethered spinal cord, 62 Hemimyelocele, split cord malformations with, 126 Hemimyelomeningocele, 97, 100f Hiccups, postoperative, in Chiari malformations, 9, 12 Hindbrain hernias. See Chiari malformations Hoarseness, postoperative, in craniovertebral junction abnormalities, 26 Hopkins, Harold H., 227 Hourglass deformity fibrous dysplasia and, 6 telorbitism and, 32 Hydrocephalus with Chiari I malformation, 7, 111 with coronal synostosis, 256–257 with craniopagus twin separation, 213–214 with Dandy-Walker malformation, 104–110 with growing skull fracture, 40–42 with lipomyelomeningocele, 64 with myelomeningocele, 102 with occipital encephaloceles, 43 with pansynostosis, 50, 61 ventricular endoscopy for, 215, 230–231, 230f ventriculoatrial shunt for, 34–39 ventriculoperitoneal shunt for, 34, 104–110 Hygroma, subdural, ventriculoatrial shunt for, 34 Hypercanthorum, 27–32 postoperative management of, 32 surgery for calvarial bone graft for, 28, 31f complications of, 32 patient positioning for, 27 patient selection for, 27 preoperative preparation for, 27 procedure for, 27–32, 29f–31f risks of, 27 timing of, 27 Hypertelorism (telorbitism), 27–28, 88–95, 89f clinical case of, 94–95, 94f definition of, 88 postoperative management of, 32, 93–94 radiologic findings of, 88, 88f, 94f, 95 surgery for, 27–28, 88–95 blood loss in, 89 closure in, 92 complications of, 32, 93–94 craniofacial osteotomies in, 28, 29f, 90–91, 91f–93f draping for, 27, 89 flap elevation in, 89–90, 90f patient positioning for, 27, 32, 89 patient selection for, 27 preoperative evaluation for, 88–89 preoperative preparation for, 27, 89 procedure for, 27–28, 32, 33f, 89–95 results of, 94–95, 94f risks of, 27 skin incisions for, 28, 89
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Index 321 timing of, 27 Hypertension, intracranial. See Intracranial pressure Hypertension, pulmonary, ventriculoatrial shunt and, 34 Hypertensive hydrocephalus, with Chiari I malformation, 7 Hypoglossal nerve, craniovertebral junction abnormalities and, 20, 26 Hypotelorism, with metopic synostosis, 286–288, 298–302, 301f Hypothalamus injury, in endoscopy, 226 Hypothermia, 257
I Immune complex glomerulonephritis, ventriculoatrial shunt and, 34, 39 Inclusion dermoid tumor, with myelomeningocele, 97, 99f, 100 Incontinence, tethered spinal cord and, 62, 136–137 Infected shunt, 233–240 Infection, postoperative in coronal synostosis, 19, 170, 249, 261, 311 in craniovertebral junction abnormalities, 26 in fibrous dysplasia, 6 in filum terminale sectioning, 141 in lipomyelomeningocele, 274 in lumbosacral meningocele, 255 in metopic synostosis, 290 in orbital malposition, 32 in pansynostosis, 57–61 in plagiocephaly, 170 in sagittal synostosis, 295 in tethered spinal cord, 265 in ventricular endoscopy, 226 in ventriculoatrial shunting, 34, 39 in ventriculoperitoneal shunting, 109–110 Internal carotid arteries, in moyamoya syndrome, 171 Internal jugular vein, percutaneous access for ventriculoatrial shunt, 36, 36f Intracranial hemorrhage orbital malposition and, 32 ventriculoatrial shunt and, 34 Intracranial pressure brain abscess and, 158 coronal synostosis and, 13 craniopagus twin separation and, 213 growing skull fracture and, 40 metopic synostosis and, 286 orbital malposition and, 32 pansynostosis and, 50–51, 61 sagittal synostosis and, 291–292 total calvarial reconstruction and, 247 ventricular endoscopy and, 226 ventriculoatrial shunt and, 34 Intramedullary spinal lipomas, 62, 64 operative procedure for, 64 surgical candidates for, 64 Isolation bubble, surgical, 106–107, 107f
J Jugular vein, internal, percutaneous access for ventriculoatrial shunt, 36, 36f Juvenile pilocytic astrocytoma, 276
K Klebsiella, and shunt infection, 235t Kleeblattschädel, 241 Klippel-Feil syndrome, 251 KTP laser, in endoscopy, 223, 229
L Lambdoid synostosis calvarial reconstruction for, 184–189 blood loss in, 185 complications of, 189 craniotomy in, 186–187, 186f–188f operating room setup for, 185 patient positioning for, 185, 185f patient selection for, 184–185
14535IDX.indd 321
postoperative management of, 189 preoperative preparation for, 185, 185f procedure for, 186–188 skin incision for, 186 “sunrise” appearance in, 186, 188f tiara in, 187, 187f–188f deformity with, 184, 184f–185f endoscopic-assisted craniectomy for, 190–192 closure in, 191–192 complications of, 192 metallic markers for, 190, 190f operative technique for, 191–192, 191f–192f outcome of, 193f patient positioning for, 190, 190f patient selection for, 190 postoperative management of, 192 preoperative preparation for, 190 procedure for, 190–192 skin incision for, 190–191, 191f helmet use in, 192, 192f, 197 incidence of, 194–195 intraoperative photographs of, 201, 201f vs. nonsynostotic plagiocephaly, 184, 194, 197 posterior plagiocephaly with, 194–202 diagnostic criteria for, 194 features and diagnosis of, 194t morphology of, 194, 195f–196f postoperative management of, 201–202 surgical management of, 194–202 alternatives to, 197 blood loss in, 197–198, 201 complications of, 201–202 contraindications to, 197 craniotomy in, 199–201, 200f draping in, 198 eye protection in, 198, 198f indications for, 197 patient positioning for, 198, 198f patient selection for, 194–195 preoperative preparation for, 197–198 procedure for, 198–201 skin flap in, 198–199, 199f skin incision in, 198, 199f technique in, 198–201 radiologic findings of, 190, 194, 196f–197f, 201 Laminectomy for Chiari I malformation, 112, 115 for filum terminale sectioning, 138, 138f for lipomyelomeningocele, 148 for lumbosacral meningocele, 254, 254f for posterior fossa decompression, 281, 283f in selective dorsal rhizotomy, 177–180, 180f for split cord malformations, 119–120, 120f, 122, 143, 144f for tethered spinal cord, 132f, 138, 138f Lasers for brain stem glioma, 278 for endoscopy, 223, 229 for lipomyelomeningocele, 149, 150f for tethered spinal cord, 153, 264 Latex precautions, 129, 152 Leptomeningeal cyst, 40. See also Growing skull fracture Lespinasse, Victor Darwin, 227 Lingual swelling, postoperative, in craniovertebral junction abnormalities, 26 Lipomas. See also Lipomyelomeningocele dorsal, 148 intramedullary spinal, 62, 64 operative procedure for, 64 surgical candidates for, 64 terminal, 148 transitional, 151 Lipomyelomeningocele(s), 62, 64–68, 147–151, 269–274 anatomical variations of, 68, 270–272 caudal, 64, 270–272, 273f clinical presentation of, 64, 147, 269
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Lipomyelomeningocele(s), (continued) definition of, 147 diagnosis of, 269–270, 270f dorsal, 64, 148, 270–271, 271f–272f multidisciplinary approach to, 270 natural history of, 65 postoperative management of, 151, 273–274 radiologic findings of, 64–65, 147, 269–270 surgery for, 269–274 anesthesia considerations in, 147 blood loss in, 270, 274 closure in, 151, 272–273 complications of, 151, 273–274 conservative approach in, 149, 150f dorsal roots in, 66–67, 66f dural closure in, 67, 67f dura-lipoma complex in, 66–67, 66f exposure in, 65–66, 65f, 147–148 laminectomy in, 148 laser use in, 149, 150f long-term results of, 67–68 neural tube reconstitution in, 66, 67f patient positioning for, 147, 270 patient selection for, 64–65, 269–270 preoperative preparation for, 65, 147, 270 procedure for, 65–67, 65f–67f, 147–151, 270–273 skin incision in, 65, 65f, 147, 148f, 270 specialized instrumentation for, 273 technique of, 147–151, 148f–149f, 151f timing of, 65, 147, 269–270 syringohydromyelia with, 64, 66, 68f terminal, 148 tethered cord with, 64, 269 transitional, 151, 270, 272, 273f Longus capitis muscle, in transoral surgery, 24 Longus colli muscles, in transoral surgery, 22, 23f–24f, 24 Lumbar puncture, in brain abscess, 159 Lumbosacral meningoceles postoperative management of, 255 surgical repair of, 251–255 anesthesia for, 252 approach in, 253–255 closure in, 255, 255f complications of, 255 draping in, 253 filum terminale sectioning in, 254f, 255 follow-up of, 255 goals of, 251 instrumentation for, 252 laminectomy in, 254, 254f patient positioning for, 253, 253f patient selection for, 251–252 preoperative preparation for, 252 procedure for, 252–255 skin incision in, 253–254, 253f Lung disease, brain abscess with, 157–158
M Magnetic resonance angiography of craniopagus twins, 209, 211f of craniovertebral junction abnormalities, 20, 21f, 26 of moyamoya syndrome, 171, 175–176, 176f Magnetic resonance imaging of anterior cranial base encephalocele, 71 of brain abscess, 159, 160f of brain stem gliomas, 275–276 of Chiari II malformation, 10, 12 of Chiari I malformation, 7, 9, 111, 114, 114f, 285 of coronal synostosis, 311 of craniopagus twins, 209, 210f, 213 of craniovertebral junction abnormalities, 20, 26 of Dandy-Walker malformation, 104, 106f of filum dysgenesis, 267 of growing skull fracture, 40–41 of lipomyelomeningocele, 64–65, 147, 269–270
14535IDX.indd 322
of meningocele, 252 of metopic synostosis, 298 of moyamoya syndrome, 171, 175–176 of myelomeningocele, 102, 103f of occipital encephaloceles, 43 of pansynostosis, 50, 61 of spastic cerebral palsy, 177 of split cord malformations, 119, 142 of syringomyelia, 111, 114, 114f of tethered spinal cord, 62–63, 129, 130f, 136–137, 136f, 141, 152–153, 262–263, 267 in ventricular endoscopy, 215, 230 Magnetic resonance venography, of craniopagus twins, 209, 211f Marchac forehead templates, 57, 167, 168f, 186 Mastoiditis, brain abscess with, 157–158, 158f Meningitis brain abscess with, 157–158 postoperative in colloid cyst removal, 232 in craniovertebral junction abnormalities, 26 in hypertelorism, 93 in orbital dystopia, 93 in orbital malposition, 32 with posterior fossa decompression, 285 Meningocele(s) cervical, 251 definition of, 251 diagnosis of, 251–252 embryopathy of, 251 lumbosacral postoperative management of, 255 surgical repair of, 251–255 anesthesia for, 252 approach in, 253–255 closure in, 255, 255f complications of, 255 draping in, 253 filum terminale sectioning in, 254f, 255 follow-up of, 255 goals of, 251 instrumentation for, 252 laminectomy in, 254, 254f patient positioning for, 253, 253f patient selection for, 251–252 preoperative preparation for, 252 procedure for, 252–255 skin incision in, 253–254, 253f postnatal evaluation and care of, 252 prenatal evaluation and care of, 251–252 prognosis of, 251 radiographic findings of, 251–252 thoracic, 251 ventral sacral, 251 Methylene blue markings in coronal synostosis, 259 in pansynostosis, 53, 56f Metopic synostosis, 286–290, 296–303 cognitive impairment with, 286 compensatory growth in, 286, 288f, 296 definition of, 286 diagnosis of, 286, 296–297, 297f etiology of, 296, 298 multidisciplinary approach to, 297–298 ophthalmologic exam in, 286, 297–298 postoperative management of, 289–290, 302–303 radiologic findings of, 286, 296–297, 296f–297f, 298, 302, 302f referring pediatrician and, 298 relapse or recurrence of, 290 skull deformity in, 286, 288f, 296–297, 296f–297f surgery for blood loss in, 290, 298, 303 closure in, 288–289 complications of, 289–290, 302–303 craniofacial reconstruction in, 287–288, 288f, 299–302, 301f–303f
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Index 323 craniotomy in, 287, 288f, 299, 299f dural opening in, 299 flap elevation in, 287 indications for, 286 osteotomies in, 287, 288f, 299, 300f outcome of, 303 patient positioning for, 287 patient selection for, 286–287, 296–297 plate-and-screw fixation in, 288–289, 298–302 preoperative preparation for, 287, 297–299 procedure for, 287–289, 299–302 skin incision in, 287, 299 specialized instrumentation for, 289 timing of, 286–287, 298 Metronidazole, for shunt infection, 235t Microcephaly, pansynostosis with, 50 Middle cerebral artery, in craniopagus twins, 209, 211f, 212 Minimally invasive neurosurgery, 227. See also Endoscopy, ventricular Miniplates for exorbitism, 78 for fibrous dysplasia, 5, 6f for lambdoid synostosis, 187f, 201–202 for pansynostosis, 61 for plagiocephaly, 167–168, 167f, 169f, 170, 201–202 for sagittal synostosis, 293 Monro, foramen of, endoscopic approach to, 217, 217f–218f Moyamoya syndrome, 171–176 angiographic appearance of, 171 clinical presentation of, 171 congenital syndromes associated with, 171 definition of, 171 incidence of, 171 medical treatment of, 171 origin of term, 171 pial synangiosis for, 171–176 advantages of, 171 anesthesia in, 172 arachnoid opening in, 174, 174f–175f closure in, 175 complications of, 175 dural opening in, 173–174, 174f follow-up of, 175–176, 176f patient positioning for, 172–173, 172f patient selection for, 171 postoperative management of, 175–176 preoperative preparation for, 171–172 procedure of, 172–175, 173f–175f skin incision in, 173 radiologic findings of, 171–172, 175–176, 176f MRA. See Magnetic resonance angiography MRI. See Magnetic resonance imaging MSX mutations, 256 Mucocele, postoperative, 93 Mycobacterium tuberculosis, and brain abscess, 158 Myelomeningocele(s) Chiari II malformations with, 7, 10–12 coexisting anomalies with, 96 hydrocephalus with, 102 inclusion dermoid tumor with, 97, 99f, 100 placode protection in, 96 postoperative management of, 103 closure site care, 103 patient care, 103 prenatal diagnosis of, 96 size of sac, 97 split cord malformations with, 97, 100f, 116, 123f, 124, 126 surgical closure of, 96–103 anatomical reconstruction in, 97–102, 102f–103f dural closure in, 101f, 102 goals of, 96 missed abnormalities in, 97 patient selection for, 96 preoperative preparation for, 96 preservation of neural tissue in, 97
14535IDX.indd 323
preservation of neurologic function in, 96–97 preservation of vascular supply in, 97, 98f procedure for, 97–102 separation of normal from abnormal skin in, 97, 99f skin closure in, 102 timing of, 96 tethered spinal cord with repair of, 97, 100, 102f, 129–135, 152–156, 262–265 postoperative management of, 135, 153–156, 264 shunt evaluation in, 152–154 surgery for, 263–265 anatomy in, 263 anesthesia for, 129 arachnoid opening in, 132f, 133–134, 133f closure in, 134–135, 134f, 153, 155f, 264 complications of, 135, 153–156, 264–265 draping for, 130 dural opening in, 132f, 133, 152, 154f exposure in, 130–134 goal of, 129 laminectomy in, 132f laser use in, 153, 264 microinstruments for, 152–153, 154f nerve roots in, 133, 133f operating room setup for, 129–130 patient positioning for, 129–130, 131f, 152 patient selection for, 129, 152 pearls and pitfalls in, 265 placode dissection in, 152–153, 154f–155f precautions in, 129 preoperative preparation for, 129 principle of, 129 procedure for, 129–135, 152–153 skin incision in, 130, 131f, 152, 153f, 264 timing of, 152 thickened filum terminale with, 97, 98f, 100f thoracolumbar, 101f, 102 types of, 97 unrepaired, natural history of, 96
N Nafcillin, for shunt infection, 235t Nasal glioma, vs. encephalocele, 70–71 Nasal profile, in hypercanthorum, 28–32, 29f–31f Nasoethmoidal encephaloceles, 69, 70f Nasofrontal encephaloceles, 69, 70f Nasogastric feeding tube, in transoral surgery, 24–25, 25f Naso-orbital encephaloceles, 69, 70f Nausea brain abscess and, 158 postoperative, in Chiari malformations, 9, 12 Nd:YAG laser for brain stem glioma, 278 in endoscopy, 223, 229 Needle aspiration, of brain abscess, 159–161, 161f, 163f Neodymium:yttrium-aluminum-garnet (Nd:YAG) laser for brain stem glioma, 278 in endoscopy, 223, 229 Neural tube defects, 7, 10–12, 96–103. See also Lipomyelomeningocele(s); Meningocele(s); Myelomeningocele(s) Neural tube reconstruction, 66, 67f, 97–102, 102f–103f Neurofibromatosis type 1, 251 Neurogenic bladder, tethered spinal cord and, 62 Nocardia, and brain abscess, 158, 161 Nutritional status, and transoral approach, 20
O Occipital advancement, for total calvarial reconstruction, 241–250, 243f Occipital encephaloceles, 43–49, 69 location of, 43 postoperative management of, 48–49 size range of, 43 skin coverage of, 43
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324
Index
Occipital encephaloceles, (continued) surgery for anesthetic technique for, 43 complications of, 48–49 draping in, 44 dural/periosteal closure in, 45–46, 47f forceps use in, 44, 45f neural tissue management in, 44–45, 46f orbit protection in, 43, 44f patient positioning for, 43, 44f patient selection for, 43 preoperative preparation for, 43 procedure for, 43–48 scissor use in, 44, 45f skin closure in, 46–47, 48f–49f timing of, 43 Occipital horn, endoscopic approach to, 223–224, 224f–225f Occipital ligaments, in transoral surgery, 22 Occult spinal dysraphism, 62, 64 Odontoid process, in transoral surgery, 23f–24f, 24 Omental transposition and transplantation, 171 Optic nerve fibrous dysplasia and, 1 orbital malposition and, 27, 32 Orbital dystopia, 88–95, 89f anteroposterior, 27 definition of, 88 postoperative management of, 93–94 radiologic findings of, 88, 88f rotatory, 27 surgery for, 88–95 blood loss in, 89 closure in, 92 complications of, 93–94 craniofacial osteotomies in, 90–91, 91f–93f draping for, 89 flap elevation in, 89–90, 90f patient positioning for, 89 preoperative evaluation for, 88–89 preoperative preparation for, 89 procedure for, 89–95 skin incisions for, 89 vertical, 27 Orbital malposition, 27–33. See also Hypercanthorum; Hypertelorism; Hypotelorism postoperative management of, 32 recurrence of, 27, 32 surgery for anesthesia for, 27 calvarial bone graft for, 28, 31f complications of, 32 costochondral bone graft for, 28, 31f goal of, 27 patient positioning for, 27, 32 patient selection for, 27 preoperative preparation for, 27 procedure for, 27–32, 29f–31f, 33f risks of, 27 timing of, 27 types of, 27 Orbital nerve, in fibrous dysplasia, 4 Orbital reconstruction in coronal synostosis, 15–18, 16f–17f, 244–246, 246f, 306–310 in metopic synostosis, 287–288, 288f, 299–302, 301f–303f Osteomyelitis brain abscess with, 157 postoperative in coronal synostosis, 19, 170, 261 in craniovertebral junction abnormalities, 26 in fibrous dysplasia, 6 in metopic synostosis, 290 in orbital malposition, 32 in plagiocephaly, 170
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Otitis media, brain abscess with, 157–158, 158f
P Palatal dehiscence, 26 Palate, in transoral surgery, 22–26, 23f–24f Pansynostosis, 50–61 clinical signs of, 50 hydrocephalus with, 50, 61 postoperative management of, 57–61 radiologic findings in, 50 surgery for anesthetic considerations in, 51 bioethics review for, 50 blood loss/hemorrhage in, 50–51, 57 cerebrospinal fluid leaks in, 53, 61 closure in, 57 complications of, 57–61 craniofacial reconstruction in, 52f, 53–57, 54f–56f, 58f–60f dead space in, 61 draping in, 51 dressing in, 57 infection in, 57–61 methylene blue markings in, 53, 56f miniplate fixation in, 61 monitoring in, 51 operating room setup in, 51, 60f patient positioning for, 51, 52f, 53, 60f, 61 patient selection for, 50 preoperative preparation for, 50–51 procedure for, 51–57 risks of, 50 skin incision in, 51–53 specialized instrumentation in, 57 technique for, 53–57 timing of, 50 “thumbprinting” appearance of, 50, 52f, 53, 54f Papilledema, with brain abscess, 158 Pericranial tissue repair, in fibrous dysplasia, 5–6 Pfeiffer syndrome, 256 Pharyngeal dehiscence, 26 Pharynx, in transoral surgery, 22–26, 23f–24f Phonation, Chiari II malformation and, 10 Pial synangiosis, 171–176 advantages of, 171 anesthesia in, 172 arachnoid opening in, 174, 174f–175f closure in, 175 complications of, 175 dural opening in, 173–174, 174f follow-up of, 175–176, 176f patient positioning for, 172–173, 172f patient selection for, 171 postoperative management of, 175–176 preoperative preparation for, 171–172 procedure of, 172–175, 173f–175f skin incision in, 173 “Ping-pong” fractures, 83, 84f Plagiocephaly, 165–170 artist’s rendering of, 166f nonsynostotic, 184, 194, 197 posterior computed tomography of, 194, 196f–197f, 201 diagnostic criteria for, 194 features and diagnosis of, 194t incidence of, 194–195 morphology of, 194, 195f–196f postoperative management of, 201–202 surgical management of, 194–202 alternatives to, 197 blood loss in, 197–198, 201 complications of, 201–202 contraindications to, 197 craniotomy in, 199–201, 200f draping in, 198 eye protection in, 198, 198f
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Index 325 indications for, 197 patient positioning for, 198, 198f patient selection for, 194–195 preoperative preparation for, 197–198 procedure for, 198–201 skin flap in, 198–199, 199f skin incision in, 198, 199f technique in, 198–201 postoperative management of, 170 surgery for blood loss in, 166, 170 closure in, 168–170 complications of, 170 craniofacial reconstruction in, 167–168, 167f–169f craniotomy in, 167–168, 167f–168f flap elevation in, 166–167 patient positioning for, 166 patient selection for, 165 preoperative preparation for, 165–166 procedure for, 166–170 radiologic findings of, 165 skin incision in, 166–167 specialized instrumentation in, 170 timing of, 165 Plain films. See X-rays Plate fixation in coronal synostosis, 17, 17f, 19, 167–168, 167f, 169f, 170, 261, 308–310 in craniopagus twin separation, 212, 213f in exorbitism, 78 in fibrous dysplasia, 5, 6f in hypertelorism, 91 in lambdoid synostosis, 187f, 201–202 in metopic synostosis, 288–289, 298–302 in orbital dystopia, 91 in pansynostosis, 61 in plagiocephaly, 167–168, 167f, 169f, 170, 201–202 in sagittal synostosis, 293 Pneumatic systems, for endoscopy, 216, 217f Posterior fossa, endoscopic approach to, 224–225, 225f Posterior fossa decompression, without duraplasty, 281–285 closure in, 282–285 complications of, 285 contraindications to, 281 craniotomy in, 281, 283f dural band incision in, 281–282, 283f follow-up care in, 285 intraoperative ultrasound in, 281–282, 284f, 285 patient positioning for, 281 patient selection for, 281 postoperative management of, 285 preoperative preparation for, 281 procedure for, 281–285 skin incision in, 281 special equipment for, 281 surgical suite setup for, 281, 282f tonsillar pistoning in, 282, 284f Potassium-titanyl-phosphate laser, in endoscopy, 223, 229 Premature infant, shunt infection in, 233 Propionibacterium acnes, and shunt infection, 235, 235t Proptosis. See also Exorbitism fibrous dysplasia and, 1, 1f, 3 Proteus and brain abscess, 158 and shunt infection, 235, 235t Pseudocyst, with shunt infection, 234, 239f Pseudomonas, and shunt infection, 235, 235t Pseudotumor cerebri, ventriculoatrial shunt for, 34 Ptosis, coronal synostosis and, 13 Pudendal nerve monitoring, with split cord malformations, 148 Pulmonary disease, brain abscess with, 157–158 Pulmonary hypertension, ventriculoatrial shunt and, 34, 39
R Radiology. See specific modalities
14535IDX.indd 325
Rectal incontinence, tethered spinal cord and, 62 Rectal sphincter electromyography, with split cord malformations, 148 Rendu-Osler-Weber syndrome, brain abscess with, 157 Retropharyngeal abscess, 26 Rhizotomy, selective dorsal, 177–183 cauda equina localization in, 179, 179f complications of, 183 conus medullaris localization in, 177–180, 179f dorsal root identification in, 181 dorsal root sectioning in, 181–183, 182f dorsal root separation in, 180f, 181 electromyography in, 177–178, 178f, 180–183, 182f, 183t indications for, 177t laminectomy in, 177–180, 180f patient positioning for, 178, 178f patient selection for, 177–178 postoperative management of, 183 preoperative preparation for, 178 procedure for, 178–183 skin incision in, 179 standard technique for, 177 ultrasound guidance in, 179, 179f Rib grafts for exorbitism, 78, 80f for fibrous dysplasia, 2 for hypercanthorum, 28, 31f Rifampin, for shunt infection, 235t Rigid endoscopes, 216, 227–229, 228f Rotatory dystopia, 27
S Saethre-Chotzen syndrome, 256 Sagittal sinus common, in craniopagus twins, 209, 210f–212f, 212–214 in coronal synostosis, 19 in growing skull fracture, 42 in metopic synostosis, 290 Sagittal synostosis, 203–208, 291–295 compensatory growth in, 291, 291f, 292, 295 definition of, 203 diagnosis of, 291 intracranial hypertension with, 291–292 intraoperative photograph of, 206f in males vs. females, 203 multidisciplinary approach in, 204 vs. positional deformity, 203 postoperative management of, 208, 294–295 radiologic findings of, 203–204, 291 relapse of, 295 skull deformity in, 203, 291, 291f, 295 surgery for, 204–208, 291–295 anesthesia for, 204 blood loss in, 204, 206, 208, 292, 294–295 bone plate recontouring in, 206, 207f closure in, 293–294 complications of, 208, 294–295 craniofacial reconstruction in, 204–208, 207f, 293, 293f– 294f craniotomy in, 204–205, 205f, 293, 293f–294f draping for, 204 flap elevation in, 293 indications for, 292 outcome of, 207f, 208 patient positioning for, 204, 204f, 292–293 patient selection for, 203, 291–292 preoperative preparation for, 204, 292 procedure for, 204–208, 292–294 skin incision for, 204, 204f, 293 surgical setup for, 292–293 timing of, 203, 292 Scaphocephaly, 203, 206f Scimitar sign, 251 Scintigraphy, of brain abscess, 159
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Scissors, endoscopic, 215, 229 SCMs. See Split cord malformations Scoliosis Chiari I malformation and, 9 split cord malformations and, 142, 146 tethered spinal cord and, 136, 262 Screw fixation in craniopagus twin separation, 212, 213f in craniosynostosis, 16–17, 16f–17f, 19, 167–170, 201–202, 288–289 SDR. See Selective dorsal rhizotomy Seizures brain abscess and, 158–159 growing skull fracture and, 41 moyamoya syndrome and, 171 occipital encephaloceles and, 43 pansynostosis and, 50 shunt infection and, 233 Selective dorsal rhizotomy (SDR), 177–183 cauda equina localization in, 179, 179f complications of, 183 conus medullaris localization in, 177–180, 179f dorsal root identification in, 181 dorsal root sectioning in, 181–183, 182f dorsal root separation in, 180f, 181 electromyography in, 177–178, 178f, 180–183, 182f, 183t indications for, 177t laminectomy in, 177–180, 180f patient positioning for, 178, 178f patient selection for, 177–178 postoperative management of, 183 preoperative preparation for, 178 procedure for, 178–183 skin incision in, 179 standard technique for, 177 ultrasound guidance in, 179, 179f Septum pellucidum, endoscopic approach to, 217, 221f, 231 Shunt. See also specific types adherent catheters in, endoscopy for, 231 infected, surgical management of, 233–240 nonfunctioning, vs. tethered cord, 152–154 syringoperitoneal, 112, 113f, 114–115 syringosubarachnoid, 112, 113f ventriculoatrial, 34–39 ventriculoperitoneal, 34, 104–110, 152, 213–214, 233–240 Shunt tap, 234–235, 234f Sincipital encephaloceles. See Frontoethmoidal encephaloceles Single photon emission computed tomography (SPECT) of coronal synostosis, 305 of metopic synostosis, 296–297 of moyamoya syndrome, 172 Sinusitis, brain abscess with, 157, 158f Skull fractures depressed, in infants, 83–87 conservative approach to, 83 vs. in older age groups, 83 “ping-pong” appearance of, 83, 84f postoperative management of, 87 surgery for anesthetic considerations in, 83 patient positioning for, 83, 84f patient selection for, 83 periosteal elevator use in, 83, 85f–86f preoperative preparation for, 83 procedure for, 83–85 risks of, 83, 87 skin incision for, 83, 85f growing, 40–42 clinical presentation of, 40 common sites for, 40 incidence of, 40 postoperative management of, 42 radiological studies of, 40–41 risk factors for, 40 surgery for
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bipolar cautery in, 41, 42f complications of, 42 dural closure in, 41–42, 42f goal of, 41 indications for, 41 procedure for, 41–42, 41f–42f venous sinuses in, 42 open, brain abscess with, 157 Soft palate, in transoral surgery, 22–26, 23f–24f Somatosensory evoked potentials (SEPs), intraoperative in split cord malformations, 119 in tethered cord, 263 Spastic cerebral palsy radiologic findings of, 177 selective dorsal rhizotomy for, 177–183 cauda equina localization in, 179, 179f complications of, 183 conus medullaris localization in, 177–180, 179f dorsal root identification in, 181 dorsal root sectioning in, 181–183, 182f dorsal root separation in, 180f, 181 electromyography in, 177–178, 178f, 180–183, 182f, 183t indications for, 177t laminectomy in, 177–180, 180f patient positioning for, 178, 178f patient selection for, 177–178 postoperative management of, 183 preoperative preparation for, 178 procedure for, 178–183 skin incision in, 179 standard technique for, 177 ultrasound guidance in, 179, 179f SPECT. See Single photon emission computed tomography Sphenoethmoidal encephaloceles, 69 Sphenomaxillary encephaloceles, 69 Spheno-orbital encephaloceles, 69 Sphenopharyngeal encephaloceles, 69 Sphinx position, in coronal synostosis, 17, 17f Spina bifida. See also Lipomyelomeningocele(s); Meningocele(s); Myelomeningocele(s) Chiari II malformations in, 7, 10–12 Spina bifida cystica, 251 Spina bifida occulta, 251 Spinal cord. See also specific disorders of progressive dysfunction of, 62–68 Spinal dysraphism, occult, 62, 64 Spinal lipomas, intramedullary, 62, 64 operative procedure for, 64 surgical candidates for, 64 Split cord malformations (SCMs), 116–128, 142–146 composite, 124f, 125–126 dermal sinus tract with, 126, 127f dermoid cyst with, 126, 127f diagnosis of, 142 embryogenesis of, 116, 142 hemicords in, dural arrangements of, 116–118 meningocele with, 251 midline septum in, nature of, 116–118 multiple, 125–126 myelomeningocele with, 97, 100f, 116, 123f, 124, 126 natural history of, 142 neuroimaging studies of, 119, 124f, 142 postoperative management of, 127–128, 146 surgery for, 116–128, 142–146 anesthesia considerations in, 142 bladder dysfunction after, 128 cerebrospinal fluid leakage in, 128 closure in, 144, 145f complications of, 127–128, 146 dural opening in, 120, 121f, 122–123, 122f–123f, 126, 143–144, 145f laminectomy in, 119–120, 120f, 122, 143, 144f neurological injury in, 127–128 neurophysiological monitoring in, 119, 148 patient positioning for, 119, 143
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Index 327 patient selection for, 118–119, 142 pitfall in, 121 preoperative preparation for, 119, 142–143 procedure for, 119–126, 143–146 skin incisions in, 119, 143, 143f special circumstances in, 125–126 technique of, 119–124, 143–146 tethered cord with, 118–119, 122f, 125, 262 type I, 116–118, 117f, 119–121, 120f–122f, 142 type II, 116–118, 118f, 121–124, 123f, 142 centromedian blood vessels with, 123f, 124 median septum in, patterns of, 121–122 septum shape in, 123–124, 123f vertebral anomalies with, 116 Staphylococcus aureus and brain abscess, 158 and shunt infection, 235, 235t Staphylococcus epidermidis, and shunt infection, 235t Stealth incision, in coronal synostosis, 258, 258f Steroids for brain abscess, 159, 161 postoperative, for brain stem glioma, 280 Strabismus, postoperative, 93 Streptococcus and brain abscess, 158 and shunt infection, 235, 235t Stroke, moyamoya syndrome and, 171, 175 Subciliary incision, in exorbitism, 78 Subclavian vein, ventriculoatrial shunting via, 36 Subdural hygroma, ventriculoatrial shunt for, 34 “Sunrise” appearance, in calvarial reconstruction, 186, 188f Superficial temporal artery, as donor vessel for moyamoya syndrome, 171, 172f, 173–176, 173f, 175f–176f Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis, 171 Superior sagittal sinus, common, in craniopagus twins, 209, 210f–212f, 212–214 Superior vena cava (SVC), in ventriculoatrial shunting, 34 Suprachiasmatic cyst, endoscopic approach to, 217, 217f, 218, 220f Supraorbital artery, in fibrous dysplasia, 3 Supraorbital nerve, in fibrous dysplasia, 3 Surgical isolation bubble, 106–107, 107f Swallowing, Chiari II malformation and, 10 Synostosis. See also specific types coronal, 13–19, 165–170, 256–261, 304–311 artist’s rendering of, 166f bilateral, 13, 15f, 256 brachycephaly with, 13, 241, 242f, 249, 256 compensatory growth in, 13, 14f–15f, 165, 166f, 241, 256, 304 definition of, 13 diagnosis of, 305 differential diagnosis of, 256 etiology of, 304 genetics of, 13, 256, 261, 305 genetic testing in, 13 individualized treatment for, 241 multidisciplinary approach to, 241–242 ophthalmologic exam in, 13 plate-and-screw fixation in, 17, 17f, 19, 167–170, 167f, 169f, 261, 308–310 postoperative management of, 19, 170, 261, 310–311 radiologic findings of, 165, 241–242, 242f, 256–257, 305–306, 305f–308f, 310–311 recurrence or relapse of, 17, 19 syndromic vs. nonsyndromic, 13, 304 total calvarial reconstruction for, 241–250 turricephaly with, 13, 241, 242f, 249, 256 unilateral, 13, 14f, 165–170, 256, 304–311, 304f–305f lambdoid calvarial reconstruction for, 184–189 deformity with, 184, 184f–185f endoscopic assisted craniectomy for, 190–192 vs. nonsynostotic plagiocephaly, 184, 194, 197 posterior plagiocephaly with, 194–202
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metopic, 286–290, 296–303 cognitive impairment with, 286 compensatory growth in, 286, 288f, 296 definition of, 286 diagnosis of, 286, 296–297, 297f etiology of, 296, 298 multidisciplinary approach to, 297–298 ophthalmologic exam in, 286, 297–298 postoperative management of, 289–290, 302–303 radiologic findings of, 286, 296–297, 296f–297f, 298, 302, 302f referring pediatrician and, 298 relapse or recurrence of, 290 skull deformity in, 286, 288f, 296–297, 296f–297f multiple suture (pansynostosis), 50–61 clinical signs of, 50 hydrocephalus with, 50, 61 postoperative management of, 57–61 radiologic findings in, 50 “thumbprinting” appearance of, 50, 52f, 53, 54f sagittal, 203–208, 291–295 compensatory growth in, 291, 291f, 292, 295 definition of, 203 diagnosis of, 291 intracranial hypertension with, 291–292 intraoperative photograph of, 206f in males vs. females, 203 multidisciplinary approach in, 204 vs. positional deformity, 203 postoperative management of, 208, 294–295 radiologic findings of, 203–204, 291 relapse of, 295 skull deformity in, 203, 291, 291f, 295 Syringohydromyelia Chiari II malformation and, 12 Chiari I malformation and, 9 lipomyelomeningocele and, 64, 66, 68f tethered spinal cord and, 129 Syringomyelia in Chiari II malformation, 7 in Chiari I malformation, 7, 9f, 111–115 difficult cases of, 112–114, 114f postoperative management of, 112–114 radiologic findings of, 111, 114, 114f in split cord malformations, 142 surgery for, 111–115 patient positioning for, 112, 113f patient selection for, 111 preoperative preparation for, 111 procedure for, 112 syringoperitoneal shunting for, 112, 113f, 114–115 syringosubarachnoid shunting for, 112, 113f Syringoperitoneal shunt, 112, 113f, 114–115 Syringosubarachnoid shunt, 112, 113f
T Tarsorrhaphy in coronal synostosis, 14 in exorbitism, 77, 80–81 in fibrous dysplasia, 3, 6 in pansynostosis, 51 in sagittal synostosis, 292 Technetium scan, of brain abscess, 159 Telorbitism (hypertelorism), 27–28, 88–95, 89f clinical case of, 94–95, 94f definition of, 88 postoperative management of, 32, 93–94 radiologic findings of, 88, 88f, 94f, 95 surgery for, 27–28, 88–95 blood loss in, 89 closure in, 92 complications of, 32, 93–94 craniofacial osteotomies in, 28, 29f, 90–91, 91f–93f draping for, 27, 89 flap elevation in, 89–90, 90f
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Telorbitism (hypertelorism), (continued) patient positioning for, 27, 32, 89 patient selection for, 27 preoperative evaluation for, 88–89 preoperative preparation for, 27, 89 procedure for, 27–28, 32, 33f, 89–95 results of, 94–95, 94f risks of, 27 skin incisions for, 28, 89 timing of, 27 Temporal horn, endoscopic approach to, 223, 223f–224f Temporalis muscles in coronal synostosis, 15, 167, 258, 310 in exorbitism, 77–78, 80 in fibrous dysplasia, 3, 6 in metopic synostosis, 300–302 in orbital dystopia, 91 in pansynostosis, 57 in plagiocephaly, 167 in sagittal synostosis, 204–205, 206f, 208 in telorbitism, 32, 33f, 90–91 Temporal lobe abscess, 157 Tethered spinal cord, 62–64 challenges of, 262 clinical presentation of, 62, 136, 262 computed tomography myelogram of, 62 embryology of, 136 filum terminale dysgenesis and, 262, 267–268 filum terminale sectioning for, 136–141, 267–268 anatomy in, 267 anesthetic considerations in, 137 bipolar coagulation in, 138–141, 140f closure in, 140f, 141, 267–268 complications of, 141 dural opening in, 138, 139f laminectomy in, 138, 138f patient positioning for, 137, 137f patient selection for, 136–137 pearls and pitfalls in, 268 postoperative management of, 141, 268 preoperative preparation for, 137 procedure for, 137–141, 267–268 prognosis in, 141 skin incision for, 138, 138f, 267, 268f technique of, 138–141, 138f–140f filum terminale thickening in, 62–63, 64f, 136–141, 262, 267–268 with lipomyelomeningocele, 64, 269 magnetic resonance imaging of, 62–63, 129, 130f, 136–137, 136f, 141, 152–153, 262–263, 267 multidisciplinary approach to, 152, 262 after myelomeningocele repair, 97, 100, 102f, 129–135, 152–156, 262–265 postoperative management of, 135, 153–156, 264 shunt evaluation in, 152–154 surgery for, 263–265 anatomy in, 263 anesthesia for, 129 arachnoid opening in, 132f, 133–134, 133f closure in, 134–135, 134f, 153, 155f, 264 complications of, 135, 153–156, 264–265 draping for, 130 dural opening in, 132f, 133, 152, 154f exposure in, 130–134 goal of, 129 laminectomy in, 132f laser use in, 153, 264 microinstruments for, 152–153, 154f nerve roots in, 133, 133f operating room setup for, 129–130 patient positioning for, 129–130, 131f, 152 patient selection for, 129, 152 pearls and pitfalls in, 265 placode dissection in, 152–153, 154f–155f precautions in, 129
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preoperative preparation for, 129 principle of, 129 procedure for, 129–135, 152–153 skin incision in, 130, 131f, 152, 153f, 264 timing of, 152 natural history of, 63, 137 postoperative management of, 63–64 with split cord malformations, 118–119, 122f, 125, 262, 265–267 postoperative management of, 265–267 surgery for anatomy in, 265 closure in, 265 patient positioning for, 265 pearls and pitfalls in, 267 procedure for, 265, 266f skin incision in, 265 surgery for, 262–268. See also specific procedures anesthesia for, 263 blood loss in, 263 medical clearance for, 263 patient positioning for, 63, 63f, 263 patient selection for, 62, 262 preoperative preparation for, 63, 152, 262–263 procedure for, 63, 63f–64f, 263–268 skin incision for, 63, 63f x-rays of, 137, 262 Tetralogy of Fallot, brain abscess with, 157 Third ventricle anterior, endoscopic approach to, 217–218, 219f–220f posterior, endoscopic approach to, 218–220, 220f–221f Third ventriculostomy, endoscopic, 230, 230f, 232 Thoracic meningocele, 251 “Thumbprinting” appearance, of pansynostosis, 50, 52f, 53, 54f Tiara reconstruction, 167–168, 167f, 169f, 187, 187f–188f Ticarcillin, for shunt infection, 235t Tissue expanders, in craniopagus twins, 210, 211f Tobramycin, for shunt infection, 235t Tongue-and-groove reconstruction, 186–187, 186f–188f, 244–246, 247f Tonsillar pistoning, in posterior fossa decompression, 282, 284f Tooth buds, exorbitism and, 76 Total calvarial reconstruction, 241–250 anesthesia for, 242 blood loss in, 249 closure in, 246–247 complications of, 249 draping in, 244, 245f exposure in, 244, 245f final recontouring in, 246, 248f height reduction in, 246, 248f intraoperative monitoring in, 242, 247 occipital advancement in, 246, 247f orbital advancement in, 244–246, 246f outcome of, 249 patient positioning for, 243–244, 243f patient selection for, 241 postoperative management of, 249 preoperative preparation for, 242 skin incision in, 244, 245f specialized instrumentation for, 247–249 timing of, 241, 249–250 Total cranial vault reconstruction, 204–208, 291–295 anesthesia for, 204 blood loss in, 204, 206, 208, 292, 294–295 bone plate recontouring in, 206, 207f closure in, 293–294 complications of, 208, 294–295 craniofacial reconstruction in, 204–208, 207f, 293, 293f–294f craniotomy in, 204–205, 205f, 293, 293f–294f draping for, 204 flap elevation in, 293 indications for, 292 outcome of, 207f, 208
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Index 329 patient positioning for, 204, 204f, 292–293 patient selection for, 203, 291–292 preoperative preparation for, 204, 292 procedure for, 204–208, 292–294 skin incision for, 204, 204f, 293 surgical setup for, 292–293 timing of, 203, 292 “Tower-shaped” appearance, in coronal synostosis, 13, 15f, 256 Toxoplasma gondii, and brain abscess, 158–159 Tracheostomy, in transoral surgery, 20–21 Traction, cervical, in transoral surgery, 21–22, 25–26 Transbuccal incision, in exorbitism, 78 Transethmoidal encephaloceles, 69 Transient ischemic attacks (TIAs), moyamoya syndrome and, 171 Transoral surgery, for craniovertebral junction abnormalities, 20–26, 22f Transpalatal route, to craniovertebral junction abnormalities, 24–25 Trapped ventricles, endoscopy for, 224, 230–231 Trigonocephaly, 286, 288f, 296–297, 296f–297f Tube exchanger, in transoral surgery, 25 Turricephaly, 13, 241, 242f, 249, 256 Twins, craniopagus classification of, 209 epidemiology of, 209 frontal, 209 occipital, 209 parietal, 209 photograph of, 209f radiologic studies of, 209, 210f–211f separation of, 209–214 challenge of, 214 closure in, 212, 213f complications of, 213 craniofacial reconstruction in, 210, 212, 213f craniotomy in, 212, 212f dural graft in, 212, 212f dural opening in, 212 main questions in, 209 mortality and morbidity in, 209, 214 outcome of, 214, 214f patient positioning for, 210 patient selection for, 209 plate-and-screw fixation in, 212, 213f postoperative management of, 213 preoperative embolization for, 209 preoperative preparation for, 209–210 preoperative tissue expanders for, 210, 211f procedure for, 210–212 skin incision for, 210, 211f–212f shared sagittal sinus in, 209, 210f–212f, 212–214 shared vascular anatomy of, 209–210, 210f–211f temporoparietal, 209 vertical, 209 TWIST mutations, 256, 261
U Ultrasound of Dandy-Walker malformation, 104 intraoperative in brain abscess, 161, 161f–162f in Chiari II malformation, 11 in posterior fossa decompression, 281–282, 284f, 285 in selective dorsal rhizotomy, 179, 179f in total calvarial reconstruction, 242 in ventriculoatrial shunting, 35–36, 38 of lipomyelomeningocele, 147 of meningoceles, 251–252 of myelomeningocele, 96 of split cord malformations, 142 of tethered spinal cord, 136 of ventriculoperitoneal shunt, 234–235 Urinary dysfunction lipomyelomeningocele and, 65, 68, 147, 269, 274
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split cord malformations and, 128 tethered spinal cord and, 62–64, 136–137
V Vagus nerve, craniovertebral junction abnormalities and, 20 Vancomycin, for shunt infection, 235, 235t Velopalatine incompetence, 26 Ventricular endoscopy, 227–232 for adherent catheters, 231, 237, 238f anesthesia for, 216, 229 approaches in, 215–226 to anterior third ventricle, 217–218, 219f–220f to foramen of Monro, 217, 217f–218f to frontal horn, 222–223, 222f–223f to occipital horn, 223–224, 224f–225f to posterior fossa, 224–225, 225f to posterior third ventricle, 218–220, 220f–221f to temporal horn, 223, 223f–224f for biopsy and treatment of tumors, 231–232 bleeding in, 225 for colloid cyst, 217, 218f, 222–223, 231–232, 231f complications of, 225–226, 232 corporate interest in, 215 CSF analysis in, 216–217 flexible, 216, 227–229, 228f general principles of, 216–217 history of, 227 for hydrocephalus, 215, 230–231, 230f imaging studies for, 215, 230 instrumentation for, 215, 227–229, 228f–229f irrigation for, 215–216, 229 lasers used in, 223, 229 learning curve for, 225 patient positioning for, 217, 222f, 223, 224f, 229 pneumatic systems in, 216, 217f postoperative management in, 225–226, 232 preoperative preparation for, 215–216, 229 procedure for, 216–225, 229–232 rigid, 216, 227–229, 228f for shunt infection, 237–238, 238f, 240 skin incision for, 216, 229 for suprachiasmatic cyst, 217, 217f, 218, 220f surgeon disorientation in, 232 surgical suite organization for, 215 training for, 215, 225, 232 Ventriculoatrial shunts, 34–39 anesthetic considerations for, 34 atrial catheter for advancing, pressure wave forms with, 37, 38f difficulty passing in patient with abnormal vascular anatomy, 39 in patient with normal vascular anatomy, 39 difficulty positioning, 39 placement of, 36, 36f, 37–38 complications of, 39 contraindications to, 34 cranial bur hole placement for, 37 EKG monitoring with, 35, 37–39 elective revision of, 39 growth-related migration of, 34, 39 imaging guidance for, 35–39 indications for, 34 intraoperative problems with, 38–39 landmarks for, 35, 35f locating ventricles in, difficulty with, 38–39 open access of common facial vein for, 36–37, 37f operative procedure for, 35–39 patient positioning for, 35–36, 35f patient selection for, 34 percutaneous access of internal jugular vein for, 36, 36f postoperative management of, 39 preoperative preparation for, 34–35 risks of, 34 special equipment for, 35 surgical steps for, 36–38
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Ventriculoatrial shunts, (continued) valve system for placement of, 37 selection of, 36 ventricular catheter for manometer attached to, 38 placement of, 37–38 Ventriculoperitoneal shunts, 34, 104–110 complications of, 109–110 connections of, 107, 108f in craniopagus twin separation, 213–214 CSF leakage around, 110 for Dandy-Walker malformation, 104–110 infection of adherent catheter in, 237, 238f antibiotic therapy for, 235, 235t clinical presentation of, 233–234 complications of, 233 custom catheters and drainage systems for, 240 diagnosis of, 234–235 externalization of shunt in, 238–240, 239f external ventricular drain in, 235–238, 236f–237f, 240 incidence of, 233 mortality and morbidity with, 233 pathogens causing, 235, 235t postoperative management of, 240 prevention of, 233–234 radiologic findings of, 234 risk factors for, 233 shunt replacement in, 236, 236f, 240 shunt tap in, 234–235, 234f surgical management of, 233–240 complications of, 240 patient selection for, 233 procedure for, 236–240 scenarios in, 236–237, 236f specialized equipment for, 240 ventriculoscopy in, 237–238, 238f, 240 intra-abdominal injury with, 110 nonfunctioning, vs. tethered cord, 152–154 operative procedure for, 105–109 patient positioning for, 105, 107f patient selection for, 104 peritoneal catheter placement in, 108–109 positioning of, 106f postoperative management of, 109–110
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preoperative preparation for, 104–105 selection of equipment, 104 skin closure in, 109 skin incision for, 106, 107f surgical isolation bubble for, 106–107, 107f surgical technique for, 106–109 ventricular catheter placement in, 106–108, 109f Ventriculoscope, 227. See also Ventricular endoscopy Vertebral artery erosion, 26 Vertical dystopia, 27 “Vest-over-pants” sutures, in occipital encephalocele closure, 45–46, 47f Visual acuity, fibrous dysplasia and, 2 Visual field, fibrous dysplasia and, 2 Vomiting brain abscess and, 158 postoperative, in Chiari malformations, 9, 12 V-Y correction, in orbital malposition, 90, 90f, 92
W “Washboard” appearance, rib grafts and, 2 White blood cell count (WBC), brain abscess and, 159
X X-rays of coronal synostosis, 305 of craniovertebral junction abnormalities, 20 of exorbitism, 77 of fibrous dysplasia, 1 of growing skull fracture, 40 of hypertelorism, 88 of lambdoid synostosis, 190 of lipomyelomeningocele, 64–65, 147, 270 of orbital dystopia, 88 of plagiocephaly, 165 of sagittal synostosis, 203, 291 of split cord malformations, 142, 146 of tethered spinal cord, 137, 262 of ventriculoatrial shunt, 39 of ventriculoperitoneal shunt, 109
Y Yttrium-aluminum-garnet (YAG) laser for lipomyelomeningocele, 149 for tethered spinal cord, 153, 264
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