The vestibular system and cerebellumThe vestibular system and cerebellum

• Practical anatomy and physiologyPractical anatomy and physiology• Symptoms and signsSymptoms and signs• Clinical syndromes - diseasesClinical syndromes - diseases

Flocculonodular lobe Flocculonodular lobe (Archicerebellum or Vestibulocerebellum)(Archicerebellum or Vestibulocerebellum)

VESTIBULAR SYSTEMVESTIBULAR SYSTEM A central role in the maintenance of equilibrium A central role in the maintenance of equilibrium

and gaze stability.and gaze stability. The vestibular system, by means of its receptors The vestibular system, by means of its receptors

for the perception of linear and angular for the perception of linear and angular acceleration, plays a central role in acceleration, plays a central role in orientationorientation..

Designed to answer two basic questions:Designed to answer two basic questions:

Which way is up?Which way is up? Where am I going?Where am I going?

VESTIBULAR SYSTEMVESTIBULAR SYSTEM

Very elusive to testVery elusive to test Five peripheral “receptors” (three Five peripheral “receptors” (three

semicircular canals, utricule, saccule)semicircular canals, utricule, saccule) Nerve (sub-divisions) Nerve (sub-divisions) Central connections Central connections Cortical areaCortical area

The otoliths register linear acceleration The otoliths register linear acceleration and static tiltand static tilt

Vestibular systemVestibular system

Vestibular System

Vestibular Nuclei (VN)Vestibular Nuclei (VN)

Vestibular signals originating in the two Vestibular signals originating in the two labyrinths first interact with signals from other labyrinths first interact with signals from other sensory systems in the VN.sensory systems in the VN.

Only one fraction of the neurons in the VN Only one fraction of the neurons in the VN receive direct vestibular input, and most receive direct vestibular input, and most neurons receive afferent input from other neurons receive afferent input from other sensory systems (visual or proprioceptive) or sensory systems (visual or proprioceptive) or regions of the CNS (cerebellum, reticular regions of the CNS (cerebellum, reticular formation, spinal cord and contralateral VN).formation, spinal cord and contralateral VN).

Consequently the output of neurons from the VN Consequently the output of neurons from the VN reflect the interaction of many systems.reflect the interaction of many systems.

Vestibulo-ocular and vestibulo-spinal reflexesVestibulo-ocular and vestibulo-spinal reflexes

Vestibulocerebellar and vestibulospinal pathways and Vestibulocerebellar and vestibulospinal pathways and connections between vestibular and ocular motor nucleiconnections between vestibular and ocular motor nuclei

Vestibular-cerebellar connectionsVestibular-cerebellar connectionsSome fibers of the vestibular nerve transmit impulses Some fibers of the vestibular nerve transmit impulses

directly via the juxtarestiform tract (next to the ICP) directly via the juxtarestiform tract (next to the ICP) and runs to the flocculonodular lobe of the cerebellum.and runs to the flocculonodular lobe of the cerebellum.

Efferents from the fastigial nucleus turn through the Efferents from the fastigial nucleus turn through the uncinate fasciculus of Russell back to the vestibular uncinate fasciculus of Russell back to the vestibular nuclei and via the vestibular nerve to the hair cells of nuclei and via the vestibular nerve to the hair cells of the labyrinth (predominantly inhibitory)the labyrinth (predominantly inhibitory)

The flocculonodular lobe of the cerebellum also receives The flocculonodular lobe of the cerebellum also receives secondary fibers from the superior, medial and inferior secondary fibers from the superior, medial and inferior vestibular nuclei. It returns efferent stimuli directly to vestibular nuclei. It returns efferent stimuli directly to the vestibular nuclei and spinal motor neurons via the vestibular nuclei and spinal motor neurons via cerebelloreticular and reticulospinal connections.cerebelloreticular and reticulospinal connections.

Each side of the cerebellum exerts an influence on the Each side of the cerebellum exerts an influence on the vestibular nuclei of both sidesvestibular nuclei of both sides

Schematic representation of the temporo-peri-Sylvian vestibular cortex (TPSVC). The vestibular sites located at the lateral aspect of the right or left hemispheres are projected on a lateral view of the right hemisphere normalized in the proportional stereotactic grid system of Talairach and Tournoux. BA = Brodmann area; CA-CP = anterior commissure-posterior commissure plane; VCA = vertical plane through CA; VCP = vertical plane through CP; SF = Sylvian fissure; STS = superior temporal sulcus; 1stTG = first (superior) temporal gyrus; 2dTG = second (mid) temporal gyrus. (red dots) Yaw plane illusions; (pink dots) pitch plane illusions; (blue dots) roll plane illusions; (green dots) translations; (black dots) indefinable sensations of body motion.

Vestibular CortexVestibular Cortex

Vestibulo-Ocular Reflex (VOR)Vestibulo-Ocular Reflex (VOR)

To hold images of the seen world steady To hold images of the seen world steady on the retina during brief head rotationson the retina during brief head rotations

Vestibular PalsyVestibular Palsy

“rapid horizontal head rotation toward the lesioned side elicits compensatory refixation saccades”

C A L O R I C T E S T I N GC A L O R I C T E S T I N G

Thermal convective Thermal convective theory:theory:

Heating or cooling Heating or cooling the external ear the external ear canal causes canal causes convection current convection current in the endolymph in the endolymph and subsequent and subsequent movement of the movement of the cupula.cupula.

Vestibular ReflexesVestibular Reflexes::• Vestibulospinal (VSR)Vestibulospinal (VSR)

– Helps maintain equilibrium - center of gravityHelps maintain equilibrium - center of gravity

Dizziness – Vertigo - DisequilibriumDizziness – Vertigo - Disequilibrium

an illusion of motion implying a disorder an illusion of motion implying a disorder of the vestibular system, either the of the vestibular system, either the peripheral labyrinth or its central peripheral labyrinth or its central connectionsconnections

Acute Vestibular SyndromeAcute Vestibular Syndrome

Severe vertigoSevere vertigo Nausea and vomitingNausea and vomiting NystagmusNystagmus Postural instabilityPostural instability

Peripheral or central??Peripheral or central??

Hotson JR, Baloh RW, N Engl J Med 1998;339:680-5Hotson JR, Baloh RW, N Engl J Med 1998;339:680-5Baloh RW, Otolaryngol Head Neck Surg 1998;119:55-9Baloh RW, Otolaryngol Head Neck Surg 1998;119:55-9

Nystagmus due to Nystagmus due to PeripheralPeripheral Acute Acute Vestibular Syndrome Vestibular Syndrome

• Mixed horizontal-torsionalMixed horizontal-torsional

• Beats away from the side of the lesionBeats away from the side of the lesion

• Increases with gaze to the quick phaseIncreases with gaze to the quick phase

• Suppressed by visual fixationSuppressed by visual fixation

• Exacerbated with affected ear downExacerbated with affected ear down

• Increased with head-shakingIncreased with head-shaking

• Saccades and smooth pursuit preservedSaccades and smooth pursuit preserved

Rt gazeRt gaze Lt gazeLt gaze

Peripheral NystagmusPeripheral Nystagmus

Grade IGrade I

Grade IIIGrade III

Grade IIGrade II

Primary positionPrimary position

Nystagmus due to Nystagmus due to Central Central Acute Acute Vestibular Syndrome Vestibular Syndrome

• Change directionChange direction

• Not altered by visual fixation Not altered by visual fixation (Failure of suppression of the VOR by fixation)(Failure of suppression of the VOR by fixation)

• Impaired saccades and smooth Impaired saccades and smooth pursuitpursuit

Rt gazeRt gaze Lt gazeLt gaze

Central NystagmusCentral Nystagmus

Primary positionPrimary position

Types of NystagmusTypes of Nystagmus

Bilateral Peripheral Bilateral Peripheral VestibulopathyVestibulopathy

Positive bilateral head thrust testPositive bilateral head thrust test ““Negative” Romberg testNegative” Romberg test ““Vestibular ataxia”Vestibular ataxia” Ototoxicity, idiopathic, presbistasis, Ototoxicity, idiopathic, presbistasis,

autoimmune disease of the inner earautoimmune disease of the inner ear

Treatment: Vestibular rehabilitationTreatment: Vestibular rehabilitation

Benign Paroxysmal Positional Benign Paroxysmal Positional Vertigo (BPPV)Vertigo (BPPV)

Vertigo of sudden onset provoked by Vertigo of sudden onset provoked by certain changes in head positioncertain changes in head position

Definite diagnosis with “positive” Dix-Definite diagnosis with “positive” Dix-Hallpike test: Hallpike test: – A mixed torsional and vertical A mixed torsional and vertical

nystagmusnystagmus– Short latencyShort latency– Short durationShort duration– FatigabilityFatigability

Posterior canal BPPVPosterior canal BPPV

Semont’s Liberatory Maneuver Semont’s Liberatory Maneuver

(Manoeuvre Liberatoire - 1988)(Manoeuvre Liberatoire - 1988)

Epley’s maneuver - 1992Epley’s maneuver - 1992

based on canalolithiasisbased on canalolithiasis easy to performeasy to perform short duration (5-7 min)short duration (5-7 min)

Additional measures:Additional measures: vibrationvibration vestibular suppressantvestibular suppressant head in upright position for 48 hshead in upright position for 48 hs

Not necessary!!!Not necessary!!!

Divisions of the CerebellumDivisions of the Cerebellum

nodulus

flocculus

Ant LobeAnt Lobe

Ant LobeAnt Lobe

Ant LobeAnt Lobe

Post Lobe

Post LobePost Lobe

Post Lobe

Post LobePost Lobe

nodulus

nodulus

Ventral View Superior Surface

flocculus

Midsagital View Schematic

Cerebellar examinationCerebellar examination

The main role of the cerebellum is to The main role of the cerebellum is to coordinatecoordinate voluntary muscular contractions. voluntary muscular contractions.

The cerebellum adjusts the The cerebellum adjusts the rate, regularity, and rate, regularity, and forceforce of willed movements and regulates muscle of willed movements and regulates muscle tone. tone.

Coordination Coordination of movement is not an isolated of movement is not an isolated function and is obviously influenced by the whole function and is obviously influenced by the whole functioning of the nervous system. functioning of the nervous system.

The cerebellum receives many sensory afferents as The cerebellum receives many sensory afferents as well the “brain command” of what to move. well the “brain command” of what to move.

Cerebellar examinationCerebellar examination

From this information the cerebellum From this information the cerebellum coordinates the coordinates the range, velocity and strength of contractionsrange, velocity and strength of contractions to produce to produce steady volitional movements and steady volitional steady volitional movements and steady volitional postures. postures.

Incoordination (ataxia)Incoordination (ataxia) is the main feature of cerebellar is the main feature of cerebellar dysfunction. An easy way to remember a dysfunction. An easy way to remember a cerebellar cerebellar syndromesyndrome is to imagine a drunken person who cannot is to imagine a drunken person who cannot coordinatecoordinate any volitional movement. He sways when any volitional movement. He sways when standing, reels when walking, slurs words when talking standing, reels when walking, slurs words when talking and has jerky eye movements when looking. and has jerky eye movements when looking.

In addition, the muscles are loose and floppy In addition, the muscles are loose and floppy ((hypotoniahypotonia))..

Cerebellar examinationCerebellar examination

The The incoordinationincoordination of limb and trunk movements is of limb and trunk movements is called called ataxia ataxia (from “taxis”= ordering or arranging).(from “taxis”= ordering or arranging).

The The incoordinatedincoordinated speech is called speech is called dysatrhia.dysatrhia. The oscillations eye movements are called The oscillations eye movements are called

nystagmus.nystagmus. The floppiness of the extremities is called The floppiness of the extremities is called hypotoniahypotonia. . Thus, Thus, ataxia, dysarthria, nystagmus and hypotoniaataxia, dysarthria, nystagmus and hypotonia

are the four major clinical signs of the cerebellar are the four major clinical signs of the cerebellar syndrome. syndrome.

It will be recognize that the abnormalities of speech It will be recognize that the abnormalities of speech and eye movement are of much the same nature of and eye movement are of much the same nature of those of volitional movements of the limbs.those of volitional movements of the limbs.

Cerebellar examinationCerebellar examination

Clinical examination for arm ataxia Clinical examination for arm ataxia 1.1. Finger-to-nose test: Inspect for Finger-to-nose test: Inspect for intention or intention or

ataxic tremorataxic tremor and for the accuracy to reach and for the accuracy to reach the nose. The cerebellar patient frequently the nose. The cerebellar patient frequently undershoots or overshootsundershoots or overshoots the target the target because of because of incoordinationincoordination of agonist- of agonist-antagonist muscles. Such an error is called antagonist muscles. Such an error is called ddysmetria.ysmetria.  

2.2. The rapid alternating movements tests (for The rapid alternating movements tests (for dysdiadochokinesiadysdiadochokinesia))

Cerebellar examinationCerebellar examination

Clinical examination for leg ataxiaClinical examination for leg ataxiaThe heel to shin test The heel to shin test The heel-tapping testThe heel-tapping test

Clinical examination for hypotoniaClinical examination for hypotonia Pendulous or hypotonic muscle stretch reflexes Pendulous or hypotonic muscle stretch reflexes  “ “Titubation”: a rhythmic “nodding” tremor of the head Titubation”: a rhythmic “nodding” tremor of the head

Clinical examination for postural or position Clinical examination for postural or position “overshooting”“overshooting”

    The arm-pulling testThe arm-pulling test

Cerebellar examinationCerebellar examination Clinical examination for “cerebellar” eye movements’ Clinical examination for “cerebellar” eye movements’

abnormalitiesabnormalities

IncoordinationIncoordination of different eye movements that include: of different eye movements that include: jerky or saccadic rather than smooth pursuit, slowness in jerky or saccadic rather than smooth pursuit, slowness in initiating eye movements and ocular dysmetria initiating eye movements and ocular dysmetria

Different types of Different types of nystagmusnystagmus reflecting reflecting vestibulocerebellum dysfunction: “Gaze evoked vestibulocerebellum dysfunction: “Gaze evoked nystagmus” (change direction in accordance to gaze nystagmus” (change direction in accordance to gaze direction). Other type of cerebellar nystagmus is the direction). Other type of cerebellar nystagmus is the “rebound nystagmus”“rebound nystagmus”

Downbeat nystagmus, opsoclonus and ocular flutter are Downbeat nystagmus, opsoclonus and ocular flutter are also eye abnormalities seen in cerebellar disordersalso eye abnormalities seen in cerebellar disorders

Cerebellar examinationCerebellar examination

Clinical examination for cerebellar Clinical examination for cerebellar dysarthriadysarthria

Cerebellar speech is Cerebellar speech is slurredslurred and and scanning scanning (words are broken up into syllables), (words are broken up into syllables), occasionally delivered with sudden occasionally delivered with sudden unexpected force (unexpected force (explosive speech)explosive speech)..