The Cerebellum The Cerebellum and its and its

ConnectionsConnections

Dr. Shittu LAJDr. Shittu LAJ

Learning outlinesLearning outlines

Gross AppearanceGross Appearance StructureStructure Functional areasFunctional areas Intracerebellar nucleiIntracerebellar nuclei Cerebellar afferent fibersCerebellar afferent fibers Cerebellar efferent fibersCerebellar efferent fibers

Gross featuresGross features The cerebellum The cerebellum

or ‘small brain’ is or ‘small brain’ is the largest part the largest part of the hind brainof the hind brain

It lies posterior to It lies posterior to the fourth the fourth ventricle, the ventricle, the pons and the pons and the medulla medulla oblongataoblongata

cerebellumcerebellum The cerebellum is located in the posterior The cerebellum is located in the posterior

cranial fossa, cranial fossa, separated from the occipital lobes of separated from the occipital lobes of

cerebrum by a dural fold, the cerebrum by a dural fold, the tentorium tentorium cerebellicerebelli

The cerebellum is connected to the midbrain, The cerebellum is connected to the midbrain, pons and medulla oblongata by pons and medulla oblongata by three pairs three pairs of peduncles-of peduncles-

SCPSCP MCPMCP ICPICP

Gross features

Gross features

Lateral view of the brainLateral view of the brain

Lobes and SubdivisionsLobes and SubdivisionsAA Anatomic Anatomic

subdivisionssubdivisions Transverse planeTransverse plane Longitudinal Longitudinal planeplane

Anterior Anterior lobelobeVermisVermis

Posterior Posterior lobelobeParavermisParavermis

Flocculonodular Flocculonodular lobelobeHemisphereHemisphere

BB Functional Functional subdivisionssubdivisions SpinocerebelSpinocerebel

lumlumCerebrocerebCerebrocerebellumellum

VestibulocerebelluVestibulocerebellumm

CC Phylogenetic Phylogenetic subdivisionssubdivisions

PaleocerebelPaleocerebellumlum

NeocerebelluNeocerebellumm

ArchicerebellumArchicerebellum 8

Anatomic subdivisionsAnatomic subdivisions

Transverse plane

Longitudinal Plane: - Midline (Vermis)- Intermediate (Paravermal)- Lateral (Hemisphere)

Anatomic subdivisions

Functional subdivisionsFunctional subdivisions 1) The vestibulocerebellum:1) The vestibulocerebellum: Corresponds with the Corresponds with the

flocculonodular lobeflocculonodular lobe Reciprocal connections with Reciprocal connections with

vestibular and reticular nucleivestibular and reticular nuclei Plays a role in control of body Plays a role in control of body

equilibrium and eye movementequilibrium and eye movement

The spinocerebellum:The spinocerebellum:

Corresponds to the Corresponds to the anterior anterior lobelobe

Reciprocal connections with Reciprocal connections with the spinal cordthe spinal cord

Plays a role in control of Plays a role in control of muscle tonemuscle tone

The cerebrocerebellum:The cerebrocerebellum:

Corresponds to the Corresponds to the posterior posterior lobelobe

Reciprocal connections with the Reciprocal connections with the cerebral cortexcerebral cortex

Plays a role in planning and Plays a role in planning and initiation of movementsinitiation of movements

Phylogenetic subdivisionsPhylogenetic subdivisions

The archicerebellum The archicerebellum – oldest zone, – oldest zone, corresponds with the corresponds with the flocculonodular lobeflocculonodular lobe

The paleocerebellum The paleocerebellum – more recent than – more recent than archicerebellum, corresponds to the archicerebellum, corresponds to the anterioranterior lobelobe

The neocerebellum The neocerebellum – most recent – most recent phylogenetically, corresponds to the phylogenetically, corresponds to the posterior posterior lobelobe

Functional areasFunctional areas

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The The posterior lobeposterior lobe contains on its inferior surface, the contains on its inferior surface, the cerebellar tonsilscerebellar tonsils

In cases of In cases of ↑↑intracranial pressure, the cerebellar tonsils may intracranial pressure, the cerebellar tonsils may herniate through the foramen magnumherniate through the foramen magnum

This This tonsilar herniationtonsilar herniation is a is a life-threatening neurologic life-threatening neurologic emergencyemergency due to compromise of vital centers in the brain due to compromise of vital centers in the brain stemstem

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Structure-anatomicStructure-anatomic The cerebellum is composed of:The cerebellum is composed of: Gray matter Gray matter – outer covering, called cortex– outer covering, called cortex Gray matter of the cortex has a uniform structure Gray matter of the cortex has a uniform structure

and divided into three layers – and divided into three layers – molecular layer, molecular layer, Purkinje cell layer and granular layerPurkinje cell layer and granular layer

White matter White matter – inner layer. White matter of each – inner layer. White matter of each hemisphere contains three masses of gray hemisphere contains three masses of gray matter, called the matter, called the intracerebellar nucleiintracerebellar nuclei

StructureStructure

Structure Structure White matterWhite matter There is small amount of white matter in the There is small amount of white matter in the

vermis and it closely resembles the trunk and vermis and it closely resembles the trunk and branches of a tree – branches of a tree – the arbor vitaethe arbor vitae

The white matter is made up of three groups The white matter is made up of three groups of fibers: (1) of fibers: (1) intrinsic, (2) afferent, and (3) intrinsic, (2) afferent, and (3) efferentefferent

The intrinsic fibersThe intrinsic fibers do not leave the do not leave the cerebellum but connect different regions of the cerebellum but connect different regions of the organorgan

The intracerebellar nucleiThe intracerebellar nuclei

A commonly used mnemonic to recall the deep cerebeller nuclei from “lateral to medial” is:

“Don’t Eat Greasy Food”

Functional areasFunctional areas

Cerebellar afferent fibersCerebellar afferent fibers The afferent fibers form the greater part of The afferent fibers form the greater part of

the white matterthe white matter They enter the cerebellum mainly through They enter the cerebellum mainly through

the inferior and middle cerebellar the inferior and middle cerebellar pedunclespeduncles

Afferent fibers from cerebral cortex:Afferent fibers from cerebral cortex:1.1. Corticopontocerebellar pathwayCorticopontocerebellar pathway2.2. Cerebro-olivocerebellar pathwayCerebro-olivocerebellar pathway3.3. Cerebroreticulocerebellar pathwayCerebroreticulocerebellar pathway

Cerebellar afferent fibersCerebellar afferent fibers Afferent fibers from spinal cord:Afferent fibers from spinal cord:1.1. Anterior spinocerebellar tractAnterior spinocerebellar tract2.2. Posterior spinocerebellar tractPosterior spinocerebellar tract3.3. Cuneocerebellar tractCuneocerebellar tract

Afferent fibers from the vestibular nerveAfferent fibers from the vestibular nerve1.1. Vestibulocerebellar tractVestibulocerebellar tract

Cerebellar efferent fibersCerebellar efferent fibers

The entire output of the cerebellar cortex is through The entire output of the cerebellar cortex is through the axons of the Purkinje cellsthe axons of the Purkinje cells

The efferent fibers from the The efferent fibers from the cerebellumcerebellum connect with connect with the the red nucleus, thalamus, vestibular complex, and red nucleus, thalamus, vestibular complex, and reticular formationreticular formation

The efferent pathways are:The efferent pathways are:

1.1. Globose-Emboliform-Rubral PathwayGlobose-Emboliform-Rubral Pathway2.2. Dentothalamic PathwayDentothalamic Pathway3.3. Fastigial Vestibular PathwayFastigial Vestibular Pathway4.4. Fastigial Reticular PathwayFastigial Reticular Pathway

Through superior cerebellar peduncle

Through inferior cerebellar peduncle

KEY CONCEPTSKEY CONCEPTS The major inputs to the cerebellum are from three The major inputs to the cerebellum are from three

sources: spinal cord, vestibular system, and sources: spinal cord, vestibular system, and cerebral cortexcerebral cortex

Deep cerebellar nuclei provide cerebellar output to Deep cerebellar nuclei provide cerebellar output to extracerebellar targetsextracerebellar targets

Extracerebellar targets include the vestibular and Extracerebellar targets include the vestibular and reticular nuclei, red nucleus, and thalamusreticular nuclei, red nucleus, and thalamus

Key conceptsKey concepts Signs of cerebellar disorders include asynergia, dysarthria, Signs of cerebellar disorders include asynergia, dysarthria,

adiadochokinesis, dysmetria, tremor, muscular hypotonia, adiadochokinesis, dysmetria, tremor, muscular hypotonia, ataxia and nystagmusataxia and nystagmus

Signs of cerebellar disease are ipsilateral to the side of Signs of cerebellar disease are ipsilateral to the side of cerebellar lesioncerebellar lesion

Lesions of the vermis are manifest by abnormalities in Lesions of the vermis are manifest by abnormalities in trunk movement trunk movement

Lesions of cerebellar hemispheres are manifested by Lesions of cerebellar hemispheres are manifested by abnormalities of movement in the extremities abnormalities of movement in the extremities