CEREBELLUM

Dr PS Deb MD, DM (Neuro)

GNRC Hospitals Guwahati, Assam, India

SCHEMATIC REPRESENTATION OF THE MAJOR ANATOMICAL SUBDIVISIONS OF THE CEREBELLUM.

PHYLOGENETIC ORGANIZATION

Spinocerebellum

Pontocerebellum

Vestibulocerebellum

DEVELOPMENT OF CEREBELLUM

Archicerebellum (nodulus)

Archicerebellum (flocculus)

Paleocerebellum

Neocerebellum

FUNCTIONAL ORGANIZATION OF CEREBELLUM

FUNCTIONAL AND PHYLOGENETIC ROLE

Phylogenetic denomination

Anatomical parts Role

Vestibulocerebellum (Archicerebellum)

Flocculonodular lobe (+ adjacent vermis)

Regulates balance and eye movements.

Spinocerebellum (Paleocerebellum)

Vermis and intermediate parts of the hemispheres ("paravermis")

regulates body & limb movements.The spino cerebellum is able to elaborate proprioceptive input in order to anticipate the future position of a body part during the course of a movement.

Cerebrocerebellum (Neocerebellum)

Middle portion of the vermis & Lateral parts of the hemispheres

involved in planning & initiation of movement.It has purely cognitive functions as well.

CEREBELLAR NUCLEUS

Dentate n. Emboliform n.

Globose n. Fastigial n.

FUNCTION OF CEREBELLAR NUCLEUS The fastigial nucleus assists stance & gait &

controls muscles only in the modes of sitting,standing & walking.

The nucleus interposed assists segmental reflexes & speeds the initiation of movement triggered by somatosensory cues.

The dentate nucleus assists in tasks requiring fine dextirity.

MOTOR MODULATION BY THE CEREBELLUM

INPUT OF CEREBELLUM

CEREBELLAR OUTPUT

VESTIBULOCEREBELLUM

THE SPINOCEREBELLUM CONTAINS TWO SOMATOTOPIC NEURAL MAPS OF THE BODY

NEOCEREBELLUM

NEURONAL CITCUITS OF CEREBELLUM

CEREBELLAR PATHWAY

Peduncle Description

SUPERIOR some afferent fibers from the anterior spinocerebellar pass to the anterior cerebellar lobe via this peduncle. Thus, the superior cerebellar peduncle is the major output pathway of the cerebellum. Most of the efferent fibers originate within the dentate nu.which in turn project to various midbrain structures including the red nucleus, the ventral lat./ventral ant. nucleus of the thalamus, and the medulla. The dentatorubrothalamo cortical& cerebellothalamocortical pathways are two major pathways that pass through this peduncle and are important in motor planning.

MIDDLE This is composed entirely of afferent fibers originating within the pontine nuclei as part of the massive corticoponto cerebellar tract.These fibers descend from the sensory and motor areas of the cerebral neocortex and make the middle cerebellar peduncle the largest of the three cerebellar peduncles.

INFERIOR Proprioceptive information from the body is carried to the cerebellum via the dorsal spinocerebellar tract. This tract passes through the inferior cerebellar peduncle and synapses within the paleocerebellum. Vestibular information projects onto the archicerebellum.The climbing fibers of the inferior olive run through the inferior cerebellar peduncle.This peduncle also carries information from the Purkinje cells to the vestibular nuclei in the dorsal brainstem located at the junction between the pons and medulla

Tracts or fiber bundles Distribution

Inferior cerebellar peduncle

Afferent paths Olivocerebellar tract

Lateral hemispheres and

cerebellar nucleus

Paraolivocerebellar tract Vermis, paravermis. and

cerebellar nucleus

Vestibulocerebellar tract

Fastigial nucleus, flocculonodular lobe, and uvula

Reticulocerebellar tract Spinal region of cerebellar

vermis

Posterior spinocerebellar tract Hind limb region of cerebellar

cortex

Trigeminocerebellar tract Dentate and emboliform

nucleus

Cuneocerebellar tract Forelimb and upper trunk region of cerebellar cortex

Anterior exterior arcuate fibers Flocculus

Arcuatocerebellar fibers  (striae

medullares) Flocculus

Efferent paths Cerebellovestibular tract Vestibular nucleus

Cerebelloreticular tract Pontine and medullary

reticular nucleus

CEREBELLAR CONNECTIONS--

Middle cerebellar peduncle

Afferent paths Pontocerebellar tract Neocerebellar cortex

Superior cerebellar peduncle

Afferent paths

Anterior spinocerebellar tract Hind limb region of cerebellar

cortex

Tectocerebellar tract Intermediate vermis and

lobulus simplex

Trigeminocerebellar tract

Efferent paths

Dentatorubral fibers Red nucleus

Dentatothalamic fibers

Ventral intermediate (VI) and

ventral anterior (VA) nucleus

of thalamus

Fastigioreticular fibers Reticular nucleus of midbrain,

pons, and medulla oblongata

CONT.

Afferent connection

MAIN CONNECTIONS OF THE VESTIBULOCEREBELLUM

Floculonodular

Lobe

Vermis

FASTIGIAL NUCLEUS

VESTIBULAR NUCLEUS

Vestibular Organ

lower motor neuron LMN

ARCHICEREBELLUM

vestibulospinal tract

MLF

RED NUCLEUS

MAIN CONNECTIONS OF THE PALEOCEREBELLUM

RED NUCLEUSNUCLEUS

INTERPOSITUS

ANTERIOR LOBE

PARAVERMAL ZONE

PALEOCEREBELLUM

Inferior OlivryNucleus

Lower motor neuronSPINAL CORD

Rubrospinal tract

spinocerebellar tract

MAIN CONNECTIONS OF THE NEOCEREBELLUM

CEREBRAL CORTEX THALAMUS

PontineNucleus

Lower motor neuron

LMN

DENTATENUCLEUS

POSTERIOR LOBE

CEREBELLAR HEMISPHERE

NEOCEREBELLUM

Pyramidal tract

CEREBELLUM AND AUTOMATIC MOTOR CONTROL

CEREBELLUM

MOTOR CORTEX

RED NUCLEUS

VESTIBULAR

NUCLEUS

RETICULAR FORMATION

LOWER MOTOR NEURONProprioceptor

s

Corticonuclear Connections

A zone ---------- fastigial nucleus medial vestibular nucleus B zone ---------- lateral vestibular nucleus

C1, C3 zone --- emboliform nucleus C2 ---------------- globose nucleus

D1 ---------------- parvocellular portion of dentate nucleus D2 ---------------- magnocellular portion of dentate

nucleus

VOOGD ORIGINALLY DESCRIBED 4 ZONES, FROM MEDIAL TO LATERAL--

1. vermis

2. paravermal region

3. cerebella hemisphere

4. nodulus

5. flocculus

6. fastigial nucleus

7. globose nucleus

8. emboliform nucleus

9. dentate nucleus

10. medial vestibular

nucleus

11. lateral vestibular

nucleus

The inferior olivary nucleus or inferior olive comprises 3 major divisions –

the principal olive (PO), the dorsal accessory olive (DAO) and the medial accessory olive (MAO). Different divisions of the olive project to

different cortical zones. The inferior olive is the only source of climbing fibre inputs to the cerebellum. Inputs from all other sources are as mossy fibres.

Olivocerebellar Connections

Caudal portion of medial and dorsal accessory olivary nucleus ----------------- vermis of cerebellar cortex (A and B) fastigial nucleus vestibular nucleus

Rostral portion of medial and dorsal accessory olivary nucleus ----------------- paravermal region (C1, C2, C3) nucleus interpositus

Principal Inferior Olivary Nucleus ----------------- cerebellar hemisphere (D1, D2) dentate nucleus

Caudal portion

Rostral portion

Principal inferior olivary nucleusmedial and dorsal accessory olivary nucleus

The posterior inferior cerebellar artery (PICA): supplies-

Lat.medullary tegmentum, inferior cerebellar peduncle The ipsilat.portion of the inferior vermis & the inferior surface of the cerebellar

hemisphere. The medial br. of the PICA supplies the

medial cerebellum & the dorsolat. Medulla oblongata.

The lateral br.supplies the inferoposterolat. aspect of the cerebellum.

VASCULAR SUPPLY OF THE CEREBELLUM:

CEREBELLAR CIRCULATION

Maintenance of Equilibrium - balance, posture, eye movement

Coordination of half-automatic movement of walking and posture maintenace - posture, gait

Adjustment of Muscle Tone

Motor Leaning – Motor Skills

Cognitive Function

CEREBELLUM:FUNCTIONS

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ARCHICEREBELUM

Floculonodular lobe- Vestibulocerebelum Function:

Maintenance of equilibrium Suppress Vestibulo Ocular Reflex Muscle tone in relation to head posture

Animal ablation Disorder of equilibrium Positional nystagmus

Human: Meduloblastoma Trunkal ataxia Vestibular nystagmus (fast component towards the

side of lesion) Positional nystagmus does not fatigue Vertigo

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PALLEO-CEREBELUM Anterior lobe + Vermis Afferent:

Spinocerebellar tract Spino-> olivo->cerebellar Spino -> reticulo ->

cerebellar Efferent

Festigio -> vestibulo -> spinal

Festigio -> Reticulo -> Spinal

Function Tone control Posture of axial muscle Equilibrium and locomotion

Animal ablation Increased lengthening

and shortening Increased tendon reflex Exagerated postural

reflex (positive supporting reflex)

Human Alcoholic degeneration Cerebellar degeneration Gait ataxia Rarely mild hypotonia,

dysmetria and dysarthria

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NEOCEREBELUM

Ablation in Dog and Cat inconstant result Monkey ablation

Hypotonia Clumsiness of ipsilateral limb Dentate nucleus ablation -> more enduring

effect intension tremor

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CEREBELLAR ZONES

1. Vermis zone: control posture, tone, locomotion, equilibrium

i. Vestibular connection project to festigial nucleusii. Control position of the head in relation to trunk and

extraocular movments

2. Intermediate zonei. Affrent-

a. proprioceptive from limbb. Sensorimotor cortexc. Collateral from corticospinal tract

ii. Efferent globos and embodiform nucleus ->VL thalamus to motor cortex

iii. Function: Regulation of movment via sensory feedback from the corticospinal muscle

a. Control velocity, force, pattern of movement

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CEREBELLAR ZONES: LATERAL Afferent: motor and sensory association cortex Efferent: Dantate -> thalamus -> motor cortex

(open loop) Function: Programing of movement before initiation Animal: coordination of ipsilateral movment Human: Hypotonia- flabby muscle, abnormal

posture (slopping of shoulder) increased excursion of outstretched hand tapping. Hyperflexibility of joint, pendular reflex knee

Cerebellum control separately the activity of alpha and gamma motor neuron

Reduced fusimotor activity from abnormal long loop reflex through precentral cortex

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CEREBELLAR DYSFUNCTION

1. Ataxia: Limb, gait and speech2. Speech: Scanning3. Tremor: Postural, intention, limb, trunk and

head4. Tone: Hypotonia -> Hyperextensibility, pendular

knee jerk, rebound phenomenon5. Voluntary movement: Dysmetria, dysynergia,

disdidokokinesia6. Gait: ataxic, truncal ataxia7. Head tilt8. Postural abnormality: due to unequal hypotonia

of truncal muscle -> scoliosis, elevation or depression of shoulder, pelvic tilt

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VOLUNTARY MOVEMENT ABNORMALITY

Gorden Holms : Rate, range and force Dyssynergia: Disruption of the normal smooth control

of movement provided by gradual contraction of synergic muscle and relaxation of their antagonist

Voluntary movement- longer to start and longer to stop

Prolongation of interval between the command and triphasic agonist- antagonist and motor sequence

Agonist burst may be too long or short or continue into the antagonist burst -> dysmetria and dysenergia

Rebound phenomenon (abnormal check reflex) Dysdiadokokinesia Decomposition of movement

Scanning speech Cogwheel eye moevment

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VOLUNTARY MOVEMENT ABNORMALITY

Dysmetria Inability of the sensorimotor apparatus to measure

distance in the course of movement Hypometria and hypermetria of the limb and eye Tremor : Postural and intention Ataxia of gait: falling towards the side of lesion Nystagmus:

Gaze paretic (evoked) deviation Downbeat Rebound Sustained horizontal Opsoclonus Skew deviation

Weakness, faitibability and loss of associted movement

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