Vestibular Disease

Question 1

function of the vestibular system

Answer 1

maintains steady visual image and body position for balance and equilibrium

Question 2

components of the vestibular system

Answer 2

• inner ear
• CN VIII
• RAS
• cerebellum
• long tracts

middle ear is not part of vestibular system but disease can extend locally into the brainstem

Question 3

lateral vestibulospinal tract

Answer 3

maintains posture on the IPSILATERAL side
- facilitates ipsilateral extensors
- inhibits contralateral extensors

disease on the R side will cause loss of R extension and over-extension on L side

Question 4

clinical signs of vestibular disease

Answer 4

1. nystagmus
2. head tilt (leaning and rolling)
3. tight circling
4. strabismus
5. ataxia
6. nausea, vomiting

Question 5

nystagmus

Answer 5

involuntary rhythmic movements of the eyeballs

can be physiologic or pathologic

Question 6

pendular nystagmus

Answer 6

equal side to side motions

congenital lesion

Question 7

jerk nystagmus

Answer 7

slow phase with a fast recovery phase to the opposite side

can be normal or pathologic

fast phase = away from lesion

Question 8

pathologic jerk nystagmus

Answer 8

classified by:
1. direction: horizontal, rotary, vertical
2. head position: positional vs non-positional
3. eye coordination: conjugate vs dysconjugate

Question 9

head tilt

Answer 9

named for the most ventral side

leads to tight circling, leaning, falling, rolling

NOTE: if circling without a head tilt –> likely NOT vestibular

Question 10

strabismus

Answer 10

ventral or ventrolateral deviation of the eyeball

can be positional or non-positional, conjugate or dysconjugate

lesion is IPSILATERAL to affected eye

Question 11

ataxia

Answer 11

lack of coordination of voluntary movements

typically an asymmetrical ataxia that is NOT associated with weakness

Question 12

are vestibular signs ipsilateral or contralateral to the side of the lesion

Answer 12

ipsilateral

Question 13

are concurrent CN deficits ipsilateral or contralateral to the vestibular lesion

Answer 13

ipsilateral

Question 14

signs of peripheral vestibular disease

Answer 14

1. nystagmus: horizontal or rotary, non-positional, conjugate, fast phase contralateral to lesion
2. head tilt: toward the lesion
3. strabismus: ventral or ventrolateral, dysconjugate ipsilateral to lesion
4. ataxia
5. vomiting if acute onset

possible associated signs: facial nerve paralysis from inflammation/compression, Horner’s syndrome, pain on palpation of bulla or TMJ, otitis externa/media/interna

Question 15

signs of bilateral peripheral vestibular disease

Answer 15

• crawling/crouching posture
• symmetrical ataxia
• wide head excursions from side to side
• absent physiologic nystagmus (no afferent input)

Question 16

signs of central vestibular disease

Answer 16

1. head tilt toward lesion
2. strabismus: ventrolateral dysconjugate ipsilateral to lesion
3. ataxia - asymmetrical without weakness
4. nystagmus: vertical, positional, dysconjugate
   - can be any of the other
5. altered mentation
6. CN V and VII deficits
7. long tract signs (CP deficits, paresis/paralysis) ipsilateral to lesion in TL and PL
8. cerebellar signs: hypermetria, intention tremor, absent menace ipsilateral to lesion

Question 17

paradoxical vestibular disease

Answer 17

form of CENTRAL vestibular disease where vestibular signs are contralateral to lesion

ipsilateral: CN deficits, CP deficits, hemiparesis
contralateral: vestibular signs (head tilt, circling)

Question 18

auditory disease

Answer 18

impairment of hearing +/- apparent behavioral problems

Question 19

peripheral deafness

Answer 19

conductive vs sensorineural vs toxic

conductive: external or middle ear problems that prevent sound transmission to the inner ear (ex. senile degeneration)

sensorineural: failure of sound transduction by organ of corti/cochlear nerve (ex. anomalous degeneration of organ of corti)

toxic: ototoxic drugs

Question 20

what test is used to diagnose peripheral deafness

Answer 20

BAER
brainstem auditory evoked response

Question 21

central deafness

Answer 21

rare

caused by bilateral temporal lobe or brainstem lesions

difficult to localize

Question 22

diagnostics for peripheral vestibular disease

Answer 22

PE, neuro exam, minimum database, otoscopic exam

CT: evaluate skull and bulla
MRI: soft tissue structures

Question 23

diagnostics for central vestibular disease

Answer 23

PE, neuro exam, minimum database, otoscopic exam

MRI is gold standard - evaluates ST structures (brain)

Question 24

DDX for peripheral vestibular disease

Answer 24

• anomalous (congenital)
• metabolic
• neoplasia
• infection –> otitis media or interna
• inflammatory –> middle ear polyp
• idiopathic –> canine and feline idiopathic vestibular
• trauma –> petrous temporal bone
• toxicity –> ototoxic drugs

Question 25

canine idiopathic vestibular disease

Answer 25

“old dog vestibular”

acute or peracute onset of vestibular signs
- NO CN VII or sympathetic signs

Dx: diagnosis of exclusion
Tx: supportive care; self limiting

Question 26

feline idiopathic vestibular disease

Answer 26

unilateral or bilateral disease with unknown cause

similar to canine

Question 27

DDX for central vestibular disease

Answer 27

• neoplasia
• nutritional –> thiamine deficiency
• infectious –> extension of bacterial otitis media/interna into the brainstem OR FIP*
• inflammatory –> MUE (GME, NE, NME)
• toxic –> metronidazole

Question 28

peripheral vestibular localizations

Answer 28

• mentation: normal
• CNs: CN VIII, CN VII signs +/- Horner’s
• nystagmus: horizontal or rotary, non-positional, conjugate
• seizures: none
• long tract signs: none

Question 29

central vestibular localizations

Answer 29

• mentation: normal or abnormal
• CNs: CN V, CN VII
• nystagmus: vertical, positional, dysconjugate (can still be horizontal, rotary, non-positional, conjugate)
• seizures: present if lesion is multifocal in cerebrum
• long tract signs: CP deficits and hemiparesis (ipsilateral)