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The vestibular system and cerebellum
• Practical anatomy and physiology
• Symptoms and signs
• Clinical syndromes - diseases
Flocculonodular lobe
(Archicerebellum or Vestibulocerebellum)
VESTIBULAR SYSTEM
 A central role in the maintenance of
equilibrium and gaze stability.
 The vestibular system, by means of its
receptors for the perception of linear and
angular acceleration, plays a central role in
orientation.
Designed to answer two basic questions:
Which way is up?
Where am I going?
VESTIBULAR SYSTEM
Very elusive to test
Five peripheral “receptors” (three
semicircular canals, utricule, saccule)
Nerve (sub-divisions)
Central connections
Cortical area
The otoliths register linear acceleration
and static tilt
Vestibular system
Vestibular System
Vestibular Nuclei (VN)
 Vestibular signals originating in the two
labyrinths first interact with signals from
other sensory systems in the VN.
 Only one fraction of the neurons in the VN
receive direct vestibular input, and most
neurons receive afferent input from other
sensory systems (visual or proprioceptive)
or regions of the CNS (cerebellum, reticular
formation, spinal cord and contralateral VN).
 Consequently the output of neurons from the
VN reflect the interaction of many systems.
Vestibulo-ocular and vestibulo-spinal reflexes
Vestibulocerebellar and vestibulospinal pathways and
connections between vestibular and ocular motor nuclei
Vestibular-cerebellar connections
Some fibers of the vestibular nerve transmit impulses
directly via the juxtarestiform tract (next to the ICP)
and runs to the flocculonodular lobe of the
cerebellum.
Efferents from the fastigial nucleus turn through the
uncinate fasciculus of Russell back to the vestibular
nuclei and via the vestibular nerve to the hair cells of
the labyrinth (predominantly inhibitory)
The flocculonodular lobe of the cerebellum also receives
secondary fibers from the superior, medial and
inferior vestibular nuclei. It returns efferent stimuli
directly to the vestibular nuclei and spinal motor
neurons via cerebelloreticular and reticulospinal
connections.
Each side of the cerebellum exerts an influence on the
vestibular nuclei of both sides
Vestibular Cortex
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.
Vestibulo-Ocular Reflex (VOR)
To hold images of the seen world steady
on the retina during brief head rotations
Vestibular Palsy
“rapid horizontal head rotation toward the lesioned
side elicits compensatory refixation saccades”
CALORIC TESTING
Thermal convective
theory:
Heating or cooling
the external ear
canal causes
convection current
in the endolymph
and subsequent
movement of the
cupula.
Vestibular Reflexes:
• Vestibulospinal (VSR)
– Helps maintain equilibrium - center of gravity
Dizziness – Vertigo - Disequilibrium
an illusion of motion implying a disorder
of the vestibular system, either the
peripheral labyrinth or its central
connections
Acute Vestibular Syndrome
Severe vertigo
Nausea and vomiting
Nystagmus
Postural instability
Peripheral or central??
Hotson JR, Baloh RW, N Engl J Med 1998;339:680-5
Baloh RW, Otolaryngol Head Neck Surg 1998;119:55-9
Nystagmus due to Peripheral Acute
Vestibular Syndrome
• Mixed horizontal-torsional
• Beats away from the side of the lesion
• Increases with gaze to the quick phase
• Suppressed by visual fixation
• Exacerbated with affected ear down
• Increased with head-shaking
• Saccades and smooth pursuit preserved
Peripheral Nystagmus
Rt gaze
Primary position
Lt gaze
Grade I
Grade II
Grade III
Nystagmus due to Central Acute
Vestibular Syndrome
• Change direction
• Not altered by visual fixation
(Failure of suppression of the VOR by fixation)
• Impaired saccades and smooth
pursuit
Central Nystagmus
Rt gaze
Primary position
Lt gaze
Types of Nystagmus
Bilateral Peripheral
Vestibulopathy




Positive bilateral head thrust test
“Negative” Romberg test
“Vestibular ataxia”
Ototoxicity, idiopathic, presbistasis,
autoimmune disease of the inner ear
Treatment: Vestibular rehabilitation
Benign Paroxysmal Positional
Vertigo (BPPV)
Vertigo of sudden onset provoked by
certain changes in head position
Definite diagnosis with “positive” DixHallpike test:
– A mixed torsional and vertical
nystagmus
– Short latency
– Short duration
– Fatigability
Posterior canal BPPV
Semont’s Liberatory Maneuver
(Manoeuvre Liberatoire - 1988)
Epley’s maneuver - 1992
 based on canalolithiasis
 easy to perform
 short duration (5-7 min)
Additional measures:
 vibration
 vestibular suppressant
 head in upright position for 48 hs
Not necessary!!!
Divisions of the Cerebellum
Ventral View
Superior Surface
Ant Lobe
flocculus
nodulus
Ant Lobe
Post Lobe
Post Lobe
Midsagital View
Schematic
Ant Lobe
nodulus
Ant Lobe
Post Lobe
Post Lobe
flocculus
nodulus
Cerebellar examination
 The main role of the cerebellum is to coordinate
voluntary muscular contractions.
 The cerebellum adjusts the rate, regularity, and
force of willed movements and regulates muscle
tone.
 Coordination of movement is not an isolated
function and is obviously influenced by the whole
functioning of the nervous system.
 The cerebellum receives many sensory afferents as
well the “brain command” of what to move.
Cerebellar examination
 From this information the cerebellum coordinates
the range, velocity and strength of contractions to
produce steady volitional movements and steady
volitional postures.
 Incoordination (ataxia) is the main feature of
cerebellar dysfunction. An easy way to remember a
cerebellar syndrome is to imagine a drunken
person who cannot coordinate any volitional
movement. He sways when standing, reels when
walking, slurs words when talking and has jerky
eye movements when looking.
 In addition, the muscles are loose and floppy
(hypotonia).
Cerebellar examination
 The incoordination of limb and trunk movements is
called ataxia (from “taxis”= ordering or arranging).
 The incoordinated speech is called dysatrhia.
 The oscillations eye movements are called
nystagmus.
 The floppiness of the extremities is called
hypotonia.
 Thus, ataxia, dysarthria, nystagmus and hypotonia
are the four major clinical signs of the cerebellar
syndrome.
 It will be recognize that the abnormalities of speech
and eye movement are of much the same nature of
those of volitional movements of the limbs.
Cerebellar examination
 Clinical examination for arm ataxia
1. Finger-to-nose test: Inspect for intention or
ataxic tremor and for the accuracy to reach
the nose. The cerebellar patient frequently
undershoots or overshoots the target
because of incoordination of agonistantagonist muscles. Such an error is called
dysmetria.
2. The rapid alternating movements tests (for
dysdiadochokinesia)
Cerebellar examination
 Clinical examination for leg ataxia
The heel to shin test
The heel-tapping test
 Clinical examination for hypotonia
Pendulous or hypotonic muscle stretch reflexes
“Titubation”: a rhythmic “nodding” tremor of the
head
 Clinical examination for postural or position
“overshooting”
The arm-pulling test
Cerebellar examination
 Clinical examination for “cerebellar” eye
movements’ abnormalities
 Incoordination of different eye movements that
include: jerky or saccadic rather than smooth
pursuit, slowness in initiating eye movements and
ocular dysmetria
 Different types of nystagmus reflecting
vestibulocerebellum dysfunction: “Gaze evoked
nystagmus” (change direction in accordance to
gaze direction). Other type of cerebellar nystagmus
is the “rebound nystagmus”
 Downbeat nystagmus, opsoclonus and ocular
flutter are also eye abnormalities seen in cerebellar
disorders
Cerebellar examination
 Clinical examination for cerebellar
dysarthria
 Cerebellar speech is slurred and scanning
(words are broken up into syllables),
occasionally delivered with sudden
unexpected force (explosive speech).