The vestibular system and cerebellum

1. The vestibular system and cerebellum Practical anatomy and physiology Symptoms and signs Clinical syndromes - diseases Flocculonodular lobe (Archicerebellum or Vestibulocerebellum)

2. 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?

3. VESTIBULAR SYSTEM Very elusive to test Five peripheral �receptors� (three semicircular canals, utricule, saccule) Nerve (sub-divisions) Central connections Cortical area

5. The otoliths register linear acceleration and static tilt

6. Vestibular system

8. Vestibular System

9. 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.

10. Vestibulo-ocular and vestibulo-spinal reflexes

11. Vestibulocerebellar and vestibulospinal pathways and connections between vestibular and ocular motor nuclei

12. 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

15. Vestibulo-Ocular Reflex (VOR)

16. Vestibular Palsy

17. C A L O R I C T E S T I N G

18. Vestibular Reflexes: Vestibulospinal (VSR) Helps maintain equilibrium - center of gravity

19. Dizziness � Vertigo - Disequilibrium

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

22. 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

23. 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

25. 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

27. Types of Nystagmus

28. 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

29. Benign Paroxysmal Positional Vertigo (BPPV) Vertigo of sudden onset provoked by certain changes in head position Definite diagnosis with �positive� Dix-Hallpike test: A mixed torsional and vertical nystagmus Short latency Short duration Fatigability

30. Posterior canal BPPV

33. Divisions of the Cerebellum

34. 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.

35. 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).

36. 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.

37. Cerebellar examination Clinical examination for arm ataxia� 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 agonist-antagonist muscles. Such an error is called dysmetria.� The rapid alternating movements tests (for dysdiadochokinesia)

38. 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

39. 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

40. 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).