Vestibulochochlear function/vestibular syndromes

Question 1

Objectives (5)

Answer 1

1. Recognize signs of vestibular dysfunction
2. Recognize signs of cerebellar dysfunction
3. List comp of Horner’s syndrome
4. Differentiate peripheral from central vestibular lesions
5. List differential diagnosis for central and peripheral vestibular disorders

Question 2

Vestibular fxn (4)

Answer 2

1. Maintenance of posture and balance: head and body
2. Fxns intimately with cerebellum
3. Peripheral or central
4. Neuroanatomic localization is critical to dx and px

Question 3

Vestibulocochlear neurons (4)

Answer 3

1. Purely sensory n.
2. Hair cells stereocilia that transform mechanical deformation into neural signals
3. Transduction in organ of corti
4. OoC houses hair cells for hearing

Question 4

Clinical eval precocial/altricial

Answer 4

Precocial
1. Chicken, sheep, cattle, horses
2. born with fully formed brains, functional hearing
Altricial
1. Humans, monkeys, dogs, cats
2. Ear canals dogs/cats open ~ 2nd week
3. Complete maturation ~6-8 weeks

Question 5

Conductive deafness (5)

Answer 5

1. Failure of conduction of sound waves from ear canal to inner ear
2. Occlusion, cong/acquired
3. Rupture of tympanic mem
4. Fluid exudate, for bod, mass
5. Age: presbucusis - ossicles

Question 6

Sensorial deafness (4)

Answer 6

1. Alterations of neural structures of aud path
2. Congenital - hair cells of OoC
3. Acquired - inf, IC dz
4. Baer test

Question 7

Congenital deafness

Answer 7

1. Don’t breed uni or bilat affected (heriditary)
2. White coat, blue eyes
3. dalmations

Question 8

Vestibular Labyrinth and semicircular ducts:

Receptor: macula (3)

Answer 8

1. Detect static or kinetic position
2. Gravity and linear acceleration
3. Otholitic membrane contains otoliths (statoconia)
   * gravity one with stones

Question 9

Vestibular Labyrinth and semicircular ducts:

Receptor: Crista ampullaris (3)

Answer 9

1. 3 in semicircular canal
2. 90 degrees to each other
3. Detect angular movements of the head
   * this is the one with water

Question 10

CN VIII entry into skull (3)

Answer 10

1. Axons enter cranial vault thru internal acoustic meatus at cerebellomedullary angel
   - rostral medulla oblongata
2. Most axons synapse on CN VIII nuclei
3. Few axons bypass CN VIII nuclei to enter the cerebellum

Question 11

Vestibular Nuclei (4)

Answer 11

1. HUGE
2. Four on each side of the brainstem: ventrolateral wall of 4th ventrical
3. Axonal projections spinal cord: vestibulospinal tracts
   - limb extensor tone (anti-gravity)
4. Axonal projections Rostrally: Medial Longitudinal Fasciculus (MLF)
   - Ocular movements (CNN III/IV/VI)
   - Head movements

Question 12

Vestibulospinal tracts (4)

Answer 12

1. Lateral vestibulospinal tract - ipsilateral ventral funiculus
2. Synapse on interneurons in spinal cord ventral gray
3. mediate facilitation of extensor muscles and inhibition of flexor muscles
4. IPSILATERAL SIDE

Question 13

Medial Longitudinal fasciculus (MLF)

Answer 13

1. Rostral projections
   - to nuclei of CN III, IV and VI
   - responsible for oculocephalic reflex
2. Caudal projections
   - medial vestibulospinal tract
   - maintain body and limb position relative to head

Question 14

Extra ocular muscle innervation (3)

Answer 14

1. CN III: oculomotor
   - dorsal, medial and ventral recti mm.
2. CN IV: Trochlear n.
   - dorsal oblique m.
   - On opposite side
3. CN VI: Abducent n.
   - Lateral rectus & retractor bulbi mm.

Question 15

Eye position: strabismus (5)

Answer 15

1. abnormal
2. ocular?
3. Vestibular? - usually
4. Congenital
5. Mechanical

Question 16

Physiologic nystagmus (4)

Answer 16

1. moves eye to hold images during head rotation or target motion
2. Receptor: ear and CN VIII
3. MLF connects VIII to III/IV/VI
4. Bilateral, opposite effects on CN III, IV, VI

Question 17

Physiologic Nystagmus can test integrity of

Answer 17

Brainstem

-WORKS BILATERALLY

Question 18

Vomiting Center (2)

Answer 18

1. In reticular formation of medulla (brainstem)

2. Receives afferent input from vestibular portion of vestibulocochlear nerve - motion sickness

Question 19

Cerebral projections (2)

Answer 19

1. Synapses in thalamus (tells you you’re off balance)

2. Provides conscious awareness of body’s position in space

Question 20

Vestibular inputs are…

-ipsilateral/contralateral facilitation

Answer 20

1. Bilateral and tonic
2. If you excite one side
   - Ipsilateral facilitation of extensors
   - contralateral facilitation of flexors

Question 21

Fall/or pushed towards

Answer 21

affected side by the normal side

Question 22

Clinical signs (7)

Answer 22

1. head tilt towrads
2. circling, leaning, falling, rolling towards
3. Unilateral or asymmetric ataxia towards
4. Strabismus
5. Nystagmus, FP away
6. nausea
7. +/- postural reaction deficits

Question 23

Pendular Nystagmus

Answer 23

weird siamese thing

Question 24

Peripheral lesions are in

Answer 24

Ear: Canal, bulla, CN VIII

Question 25

Central lesions are in

Answer 25

1. Brainstem or cerebellum 2. Paradoxical * Isolate clinical signs that involve only one

Question 26

Vestibular lesion loc. (6) | Peripheral CS

Answer 26

1. NO CP deficits 2. Normal mentation 3. Head tilt towards 4. Only deficits in CN VII or VIII 5. Strabismus 6. Nystagmus - any direction - fast phase away (I think)

Question 27

Vestibular lesion loc (6) | Central CS

Answer 27

1. CP deficits 2. Dullness/stupor 3. Head tilt 4. Other CN deficits possible 5. Strabismus 6. Nystagmus - any direction - positional, vertical - dysconjugate nystagmus - ALWAYS CENTRAL

Question 28

Vestibular lesion loc (3) | Pheripheral CS

Answer 28

1. Head tilt/ataxia, nystagmus 2. CN VII: facial n - innocent bystander 3. Horner's syndrome

Question 29

Horner's syndrome (2)

Answer 29

1. Sympathetic dysfunction | 2. Ptosis, enophthalmos, protruding nictitans

Question 30

Peripheral vestibular dzs/TX Idiopathic Otitis media/interna Neoplasia

Answer 30

Idiopathic 1. old dog (> 10yrs old, often large breed) 2. Severe head tilt and rapid nystagmus, non amb/gator rolling 3. anti-naus, anti-anx, IV fluids, +/- seds, Time, good px Otitis media/interna Otitis 1. Bacterial, polyp, PSOM (king charles thing) 2. long term Antibiotics (system), dermatologist, good px Neoplasia 1. Ear canal AdenoCA 2. SCC 3. PX gaurded

Question 31

Bilateral Peripheral Vestbular (5)

Answer 31

1. Lost BOTH left and right receptors 2. Loss of physiologic nystagmus 3. Symmetrical ataxia, truncal sway 4. Wide based and crouched 5. Usually bilateral otitis or polyps

Question 32

Central vestibular about (5)

Answer 32

1. CN deficits other than CN VII & VIII 2. Mentation changes - Ascending Reticular Activating System 3. Proprioceptive deficits - these pathways don't go thru peripheral system 4. Paresis - motor tracts transverse brainstem 5. Cerebellar and forebrain signs

Question 33

``` Central vestibular (2) Inflammatory ```

Answer 33

1. GME - likes caudal fossa 2. Variable prog - response to tx - immunosuppressive corticosteroids - immune modulation (be careful of little things that may aspirate) CsA, Cytosar, CCNU, procarbazine, leflonumide

Question 34

``` Central vestibular (3) Otogenic intracranial infection ```

Answer 34

1. OMI penetrates cranial vault 2. Central vestibular signs 3. good prog with teatment - sx: TECA/BO/VBO - long-term antibiotics - anti-Inflammatory corticosteroids

Question 35

Central vestibular dz (7) | Neoplasia

Answer 35

1. Not surgically accesible 2. RT 3. Meningioma 4. Choroid plexus tumors - other glial tumors 5. CN VIII tumor 6. Cerebellar tumors pushing down 7. Skull tumors

Question 36

Central Vestibular dz | Vascular

Answer 36

1. Vascular-esp cerebellum 2. Rostral cerebellar artery - supplies part of brainstem - So, CP deficits 3. Good prognosis - suportive care - ID and treat underlying dz

Question 37

Cerebellar syndrome

Answer 37

1. Cerebellum is inhibitory, modulatory 2. Defecits are spastic - hypermetria, ataxia, intention tremors 3. IPSILATERAL SIGNS

Question 38

White shaker syndrome

Answer 38

1. Idiopathic tremors 2. Acquired action-related repetitive myoclonus 3. Idiopathic cerebellitis 4. Steroid responsive tremor syndrome

Question 39

``` White shakes Breed CS NE CSF ```

Answer 39

``` Breed 1. young, often white, small breed dogs -maltese, westie CS 1. fine tremors in limbs, head, eyes NE 1. normal 2. menace 3. Opsoclonus (weird eye rhythms 4. ataxia 5. hypermetria CSF 1. Normal to mild lymphocytic pleocytosis ```

Question 40

White shakers DXs Therapy

Answer 40

1. MRI, progression - hyperthermia...?!?!?! 2. Therapy: Corticosteroids, Diazepam, Beta blockers 3. Good prognosis, some relapse

Question 41

Paradoxical vestibular syndrome (4)

Answer 41

1. LESION SAME SIDE AS CP DEFICITS 2. Head tilt away from lesion 3. Fast phase nystagmus may be towards 4. ALWAYS CENTRAL

Question 42

Paradoxical vestibular syndrome | DDX

Answer 42

1. Neoplasia - choroid plexus tumor at the CPA - meningioma 2. Inflammatory dz 3. Vascular event