Neuroscience II: Cerebellum
CEREBELLUM • Comprises about 10-10.5% of the weight of the whole CNS • Considered as the coordinator and predictor of movement & cognition
disrupted, the effect of compression of the 4th ventricle by cerebellar mass lesions or edema can actually cause obstructive hydrocephalus which in turn can lead to increased intracranial pressure.
embryologically from the • Originated embryologically metencepaholon (rhombic ( rhombic lip) lip) 2 Major Functions • Coordinate skilled voluntary movements • Controls equilibrium posture and muscle tone (kung (kung bakit kayo may muscle tone ngyaon, nakakaupo ng straight ngayon, that’s how the cerebellum acts). • Cerebellum is also responsible in monitoring or modulating motor activities originating in the brain centers.
Signs and symptoms of increased intracranial pressure Headache/ Vomiting with a. Papilledema
• It also regulates muscle tone, posture and equilibrium. • It has automatic excitation of antagonistic muscles at the end of movement, with simultaneous simultaneous inhibition of agonist muscles that initiated movement.
b. Diplopia (double vision) with internal squint (lateral rectus palsy secondary to abducens nerve lesion)
So where is the location of your cerebellum?
c. Deterioration in the level of consciousness consciousness (naiipit ang activating reticular system which system which is located in the brainstem)
• It is located in the posterior fossa of the skull
d. Bulging fontanel, separation of sutures, rapid enlarging head size.
• Dorsal to the brainstem
2 Major parts of the cerebellum
• Roof of 4th ventricle • Separated from the occipital lobes by the tentorium cerebelli. comprised of highly convoluted convoluted • Also comprised extensively folded cortex which is known as your folia • It has a core of white matter which contains the nuclei Since the location of the cerebellum is located near the 4 th ventricle, when 4 th ventricle gets
• Vermis – midline • Hemisphere – lateral
Neuroscience II: Cerebellum
Primary fissure – divides cerebellum into anterior and posterior lobes Posterolateral fissure – separates flocculobodular lobe from corpus cerebelli •
• •
Anterior lobe – color red; (paleocerebellum) Posterior lobe (neocerebellum), Flocculonodular lobe –color green; (archicerebellum/ vestibulorcoerebellum)
On the other hand, if patient has ipsilateral limb ataxia – cerebellar hemisphere is affected Clinical manifestation: uncoordinated clumsy movement of the lower limb Neurological test (upper extremities) • Alternating pronation-supination test - dapat may sound and dahandahan if you demonstrate it to the patient • Finger to nose test – determine if may dysmetria (cerebellar problem) Neurological test (lower extremities) • Heel – shin test Cerebellar tonsils What if you have a problem in the vermis? Clinical manifestation: Truncal ataxia – leaning of the trunk from side to side or px stands on wide based gait.
Neuroscience II: Cerebellum
Why is it important? -
In times of cerebellar tonsillar herniation, there would be compression of the medulla which leads to you respiratory arrest.
Overview of afferent and efferent tracts from the cerebellum (very important)
Superior Cerebellar peduncle
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This is the most medial surface, inferior surface of the cerebellum that sits above the foramen magnum
Chiari Malformation -
Downward displacement of the cerebellum into the foramen magnum with resulting obstructive hydrocephalus.
Cerebellar Peduncles -
Connect cerebellum to the brainstem
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3 main structures • Superior Cerebellar Peduncle (Brachium Conjunctivum) – caudal to the exit of CN IV • Middle Cerebellar Peduncle (Brachium Pontis) – superior to the exit of CN V • Inferior Cerebellar Peduncle (Restiform body or Juxtarestiform) – located at the dorsolateral aspect of the medulla
Middle Cerebellar Peduncle
Inferior Cerebellar Peduncle
Afferent
Efferent
*Anterior Spinocerebellar tract Acoustic & Optic information
*Dentatorubro thalamic tract
*Pontocerebellar tract
None
*Vestibulocerebellar tract *Olivocerebellar tract *Posterior spinocerebellar tract
*Cerebellovest ibular tract *Cerebellooliv ary tract
*Dentatothala mic tract
Vestibulocerebellar connections •
Contains feed forward and feedback loops that provide continuous correction to and anticipation to changes in stability and balance.
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Vestibulocerebellum o
o
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Oldest part Also called archicerebellum Main components are vestibular nuclei, flocculonodular lobe, inferior parts of paravermal area & fastigial nucleus
Neuroscience II: Cerebellum
Clinical application: Flocculonodular Lobe Syndrome • Result of a lesion of the flocculonodular lobe or its afferent/efferents. • Most commonly seen in children with medulloblastoma • Characterized by truncal ataxia due to inability to stabilize or balance the axial musculature • Results in a wide-based stance as well as swaying • Nystagmus is often diagnosed due to damage to the vestibuloocular pathways. Spinocerebellar connections •
Ensures the fluidity of limb movements while maintaining stability of trunk.
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Spinocerebellum
• Ethanol toxicity to Purkinje cells, particularly in the anterior lobe.
NEOCEREBELLUM • comprises the lateral aspects of the posterior lobes Input • pontine nuclei— fibers cross midline— enter contralateral neocerebellum (MCP) Additional afferents • contralateral olivary nuclear complex Reciprocal connections • Output from the neocerebellar cortex is mainly to the dentate nucleus, which in turn projects to the red nucleus and from there to the VL of the thalamus, called dentatorubrothalamic tract • there are also direct projections from the dentate nucleus to the thalamus, called dentatothalamic tract • from the thalamus, information projects
o
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Second oldest part Also called paleocerebellum Comprises anterior lobe, vermis w/o nodule, superior paravermal area
Clinical application: Anterior Lobe Syndrome • Characterized by gait ataxia due to inability to process proprioceptive information from the limbs • Friedrich ataxia • Autosomal recessive disorder • Lesion of the post. Columns of the spinal cord and the post. Spinocerebellar tracts • Afferents to the anterior lobe are affected, leads to degenerative changes in anterior lobe. • Ethanol induced gait ataxia
back to motor and sensory areas of the cortex • these reciprocal connections with the cerebral cortex put the cerebellum in a position to coordinate and streamline motor output from the cortex Functions • necessary for hand-eye coordination; uses visual input and calculates the trajectory of movement needed to reach or manipulate a target • involves both feedback and feedforward mechanisms that allow learning and experience to influence movement A. Sensory consequence • Neocerebellum also predicts the sensory consequence of movement through comparison with the past experience • E.g. why you cannot tickle yourself; the neocerebellum already predicted the sensory
Neuroscience II: Cerebellum
consequence of this selfgenerated motor command and has attenuated the response in the sensory cortex B. Voluntary movement • Neocerebellum is involved in the planning and automatisation of voluntary movements • Responsible for the fine-tuning of the motor patterns, such that with practice a new skill comes to be performed automatically • E.g. handwriting, playing the piano; we do not think about how individual letters should be written, but we think about concepts • This automatisation by the
Posterior Lobe Syndrome • result of a lesion of the posterior lobe of the cerebellar hemispheres or their afferents and efferents • most commonly seen in demyelinating diseases, such as multiple sclerosis, and midbrain infarctions affecting the dentatorubrothalamic tract (cerebellar efferent) or infarcts to the cerebellar hemispheres • characterised by deficits in hand-eye coordination, ability to calculate the trajectory to a target (dysmetria) and the inability to coordinate agonistantagonist movements of the extremities (dysdiadochokinesia). • may also have typical language
cerebellum affectively frees up the cerebrum for higher order cognitive
disorders characterised by linguistic incoordination, which refers to the
activity
inability to use grammar and syntax
C. Coordination of motor activity and cognition • Input to the cerebellum is not only from motor area but also from cortical
appropriately FUNCTIONAL ANATOMY OF THE CEREBELLUM
areas related to cognitive and sensory function • Therefore can automatise not only motor but also sensory and cognitive skills
Layers of the Cerebellar Cortex 1. Molecular 2. Purkinje 3. Granular
• The neocerebellum modulates but does not generate language and cognition
Cells of the Cerebellum
• With its connections, it is an interface between cognition and motor output • E.g. Language, which requires both mental and motor activity • Responsible for linguistic coordination, fluidity of language, automatisation of syntax and grammar, as well as prediction of sentence structure and flow 1. Granule cell • very abundant at the granular layer
Neuroscience II: Cerebellum
• receives afferent input from mossy fibres within the cerebellar glomerulus • axons travel to molecular layer where they branch in a T junction to form the
• receive mossy fibre rosettes via their dendrioles - which are excitatory to the cell type in these cortical neurons
parallel fibres 2. Golgi cell • located in the granule cell layer • radiate into all other layers • inhibitory interneurons that synapse in the cerebellar glomerulus as well as parallel, mossy and climbing fibers 3. Purkinje cell • largest cell in the cerebellar cortex • receives input from granule cells and climbing fibres • axon is the only efferent pathway of the cortex • projects via deep cerebellar nuclei • located at the Purkinje cell layer • dendrites fan out in one plane into the molecular layer where they form excitatory synapses with climbing fibres and parallel fibres (from granule cells) • activity is modulated through inhibitory synapses with the basket and stellate cells • GABA (inhibit cerebellar nuclei and vestibular area) 4. Basket and Stellate cells • inhibitory GABAergic neurons • located in the molecular layer • branching is perpendicular to the Purkinje cell dendritic tree • receive input from mossy and climbing fivers and synapse with the Purkinje cells • one basket cells synapses with about 70 Purkinje (1:70) Neurons of the Cerebellar Cortex Unipolar brush cells • within granular layer of vermis and flocculonodular lobe
Fibers of the Cerebellar Cortex 1. Mossy fibres • all cerebellar afferents originating from all sources except inferior olivary nuclear complex • spinal cord, posterior column nuclei, trigeminal, pons, vestibular nuclei • synapse with golgi cells and granule cell dendrites in the glomerulus 2. Climbing fibres • origin: inferior olivary nuclear complex • forms excitatory synapse with one specific Purkinje cell (1:1) • 1 neuron gives rise to 10 climbing fibres • constitute a sensory feeback loop indicating any motor error in current movement • key in motor learning 3. Parallel fibres • synapse with Purkinje cell dendrites • run perpendicular to the plane of the Purkinje dendritic tree Cerebellar Glomerulus
Neuroscience II: Cerebellum
• first processing station for cerebellar afferents • mossy fibre afferents terminate here and synapse with Golgi cell and granule cell
Synaptic Circuitry of Cerebellum
dendrites • synapse with granule cell is under inhibitory control of Golgi cell axons Wiring of the Cerebellar Cortex • Mossy fibre afferents project to the cerebellar glomerulus in the granular layer • In the glomerulus, the mossy fibre afferents
Cerebellar Nuclei
synapse with granule cell and Golgi cell dendrites • The Golgi cell exerts an inhibitory influence on the synapse between the mossy fibre and granule cell. • After this first processing stage, the granule cell conveys this afferent information to the Purkinje cell
1. 2. 3. 4.
Dentate Emboliform Globose Fastigial
*globose and emboliform= INTERPOSED NUCLEUS Functional Zones of the Cerebellum 1. Vermal 2. Paravermal (intermediate) 3. Lateral
Neuroscience II: Cerebellum
- cells in the spinal cord that give rise to ventral spinocerebellar tract
Functional Divisions of the Cerebellum
receive primary sensory inputs and descending reticulospinal and corticospinal fibres - provides afferent signals and feedback to the cerebellum regarding motor circuits in the spinal cord
Functional Regions of the Cerebellum (Memorise!) Regions
Functions
Motor planning for extremities
Lateral corticospinal tract
Intermediate hemispheres
Distal limb coordination
Lateral corticospinal tract, rubrospinal tract
Proximal limb and trunk coordination
Flocculonodular lobe
Balance and vestibulo-ocular reflexes
• Vestibulocerebellar - fibres convey information concerning the position of head
Motor Pathways influenced
Lateral hemispheres
Vermis
2. From Lower Brainstem • Olivopontocerebellar • Reticulocerebellar
Anterior corticospinal tract, reticulospinal tract, vestibulospinal tract, medial longitudinal spinal tract
and body in space - as well as information useful in orienting eyes during movement 3. From Cerebral Cortex • Corticopontocerebellar tract Cerebrocerebellar Tract •
In planning movement, sensory and motor CORTICOPONTINE projections provide the spinocerebellar and pontocerebellar via PONTOCEREBELLAR connections with feed forward information about an intended movement
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This plan can be evaluated in relation to current activity and correction formulated and relayed back to motor cortex via thalamus
Medial longitudinal fasciculus
Cerebrocerebellar Pathway
Cerebellar Inputs 1. From Spinal Cord • Dorsal Spinocerebellar tract - inform the cerebellum of limb position and movement - after processing in the cerebellum and their connections with motor cortex, they influence movement of the extremities and muscle tone • Ventral Spinocerebellar tract
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Via Middle Cerebellar Peduncle (Signals from the frontal and parietal lobes & temporal lobe -> crosses the midline going to the cerebellum -> planned movement)
Neuroscience II: Cerebellum
molecular and granular layers -> modulate output in the crebellum Excitatory Inputs from: • Granule cells (Parallel fibers) • Mossy fibers • Climbing fibers • Aminergic fibers Inhibitory inputs from: CEREBELLAR CIRCUITS Mossy Fibers: -
Formed by the afferent axons from
• Purkinje cells • Stellate and basket cells • Golgi cells
• Pontine Nuclei • Vestibular Nuclei • Spinal Cord
CEREBELLAR OUTPUT Dentate Nucleus
• Reticular Formation -
Synapse with granule cell dendrites
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Nuerotransmitter: GLUTAMATE
Climbing Fibers: -
Formed by afferent axons from Inferior Olivary Nucleus
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Synapse with purkinje cells dendrites
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Neurotransmitter: ASPARTATE
*BOTH FIBERS ARE EXCITATORY!
*The multilayered fibers are derived from the locus ceruleus raphei nuclei -> terminate in the
Thalamic Nuclei
Neuroscience II: Cerebellum
Cerebellar Output (FLOCCULONODULAR LOBE)
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Majority from the pontine nuclei
Superior Cerebellar Peduncle •
Flocculonodular Lobe Purkinje Cells
Main pathway for efferent cerebellar fibers to brainsem, red nucleus, thalamus
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0.8 milion fibers
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Some afferent fibers o
Lateral Vestibular Nuclei (Brainstem)
Spinal cord (ventral spinicrebellar)
Vascular Supply of the Cerebellum
Vestibulospinal Tract (Spinal Cord)
Axial and Proximal Muscles
Artery
Region Supplied
Anterior Inferior Cerebellar Artery (AICA)
-All cerebellar peduncles -Flocculus -All deep cerebellar nuclei
Posterior Inferior Cerebellar Artery (PICA)
-Inferior two thirds of the posterior lobe -Tonsils -Nodulus
Superior Cerebellar Artery (SCA)
-Anterior lobe -Superior third of the posterior lobe -Vermis
Cerebellar Input and Output Inferior Cerebellar Peduncle •
0.5 million fibers
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Two Divisions
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Restiform body
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Juxtarestiform body
Mostly afferent -
Inferior Olive
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Spinal Cord (dorsal spinocerebellar)
Some efferent
Middle Cerebellar Peduncle •
Most massive
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Only afferent fibers to the cerebellum
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20 million fibers
*dentate nucleus-AICA *interposed nucleus-AICA *A 43 yr old male presented with truncal ataxia. Diagnosis: Stroke of the Cerebellum. What artery is affected? SCA because vermis is affected Cerebellar Vascular Supply
Neuroscience II: Cerebellum
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Rebound - overshooting
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Tongue movement
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Eye movement
TANDEM GAIT
Part of the Nervous System Tested in Neurological Examination •
Mental Status – cerebroponocerebellar tract (voluntary movement)- if a patient is obtunded the pt cannot properly perform any movement
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Cranial Nerves – o
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*MCP located near the exit of CN 5- if affected – manifestations: loss of sensation in the tongue, or in the face (ophthalmic or V1, maxillary or V2 and mandibular or V3) *SCP located near the CN 4 – manifestations would be related to extraocular muscles Cerebellar manifestations with CN manifestations
Motor – Corticospinal tract – manifestations: plegia (weakness) or paresis (paralysis)
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Coordination – function of the cerebellum
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Reflexes
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Sensory
Cerebellar Examination •
Stance and gait – *wide based gait— with cerebellar dysfunction
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Finger to nose test and heel to shin test
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DYSMETRIA
Alternating movements
REBOUND TEST
Neuroscience II: Cerebellum
HEEL TO SHIN TEST
1. Ipsilateral signs with lateralized lesions -
Double decussation of efferent cerebellar pathways
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e.g. Right cerebellar hemisphere lesion – right limb ataxia
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e.g. Midline lesion in the Vermis – truncal ataxia
2. All deficits are motor -
Are superimposed on normal motor movements (no paralysis) -> incoordination
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No loss of sensory perception
FINGER TO NOSE TEST
3. Gradual but definite recovery in time -
If disturbances are due to non progressive pathology
4. Somatotopy of deficits
Clinical Manifestations of Cerebellar Disease
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Laterally placed lesions – limbs are affected
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Medially placed lesions – trunk affected
5. Severity of deficits -
A. Hypotonia – function of the spinocerebellar tract is for muscle tone B. Ataxia
Considerably increased if lesions involved the superior cerebellar peduncle or deep cerebellar nuclei
Cerebellar Lesion
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Dysmetria
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Intention tremors->”pag may ginagawa ka dun lumalabas”
!
Cerebellar hemisphere lesions result in IPSILATERAL LIMB ATAXIA
Midbrain Lesion - CLAUDE SYDROME
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Decomposition of movement
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Dsydiadochokinesia
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Diplopia with external squint
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Rebound
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Ptosis
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Speech disturbance – scanning dysarthria (“para silang galit na nagiging explosive”)
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Nystagmus – figure of H
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Oculomotor Nerve (Ipsilateral)
o
!
Red Nucleus o
General Principles of Cerebellar Syndrome
Dilated pupil, non reactive to light
Contralateral cerebellar signs
Neuroscience II: Cerebellum
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Ataxia, intention tremor, dysmetria, dysdiadochokinesia Contralateral cerebellar signs
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Vestibular Nucleus o
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Nucleus Ambiguus o
Lateral Medullary Lesion •
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o
Chronic smoker with hyperlipidemia
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On waking up today o
o
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Sudden vertigo, vomiting Numbness of left face, right UE, right LE
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Difficulty swallowing
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PE: BP
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150/90 mmHg, CR/PR 80/min regular
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Conscious, left ptosis
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Left pupil 2 mm RTL, right pupil 5 mm RTL
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o
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Cerebellar hemisphere lesion
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Uvula deviated to right: Absent left gag reflex
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LEFT LIMB ATAXIA with normal strength
MEDULLA •
Lesion at dorsolateral medulla affecting: 1. VESTIBULAR NUCLEUS 2. Nucleus ambiguous 3. Spinal Trigeminal Nucleus/Tract 4. Lateral Spinothalamic 5. INFERIOR CEREBELLAR PEDUNCLE 6. Cervical Sympathetic
Wallenberg Syndrome
Clinical manifestations are referable to LIMB ATAXIA
Cerebellar peduncle lesion o
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Horner’s Syndrome
Clinical Differentiation
EOM intact Absent pain and temperature over left face, right UE, right LE
Ipsilateral limb ataxia
Cervical Sympathetic
o •
Contralateral loss of pain and temperature in the face
Inferior Cerebellar Peduncle o
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Ipsilateral loss of pain and temperature in the face
Lateral Spinothalamic Tract o
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Dysphagia, dysphonia
Spinal Trigeminal Nucleus
50-year old male
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Vertigo with nystagmus
Clinical manifestations are referable to limb ataxia PLUS BRAISTEM MANIFESTATION (Cranial nerve deficits, long sensory tract signs)
