Vestibular Disease Flashcards
function of the vestibular system
maintains steady visual image and body position for balance and equilibrium
components of the vestibular system
- inner ear
- CN VIII
- RAS
- cerebellum
- long tracts
middle ear is not part of vestibular system but disease can extend locally into the brainstem
lateral vestibulospinal tract
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
clinical signs of vestibular disease
- nystagmus
- head tilt (leaning and rolling)
- tight circling
- strabismus
- ataxia
- nausea, vomiting
nystagmus
involuntary rhythmic movements of the eyeballs
can be physiologic or pathologic
pendular nystagmus
equal side to side motions
congenital lesion
jerk nystagmus
slow phase with a fast recovery phase to the opposite side
can be normal or pathologic
fast phase = away from lesion
pathologic jerk nystagmus
classified by:
1. direction: horizontal, rotary, vertical
2. head position: positional vs non-positional
3. eye coordination: conjugate vs dysconjugate
head tilt
named for the most ventral side
leads to tight circling, leaning, falling, rolling
NOTE: if circling without a head tilt –> likely NOT vestibular
strabismus
ventral or ventrolateral deviation of the eyeball
can be positional or non-positional, conjugate or dysconjugate
lesion is IPSILATERAL to affected eye
ataxia
lack of coordination of voluntary movements
typically an asymmetrical ataxia that is NOT associated with weakness
are vestibular signs ipsilateral or contralateral to the side of the lesion
ipsilateral
are concurrent CN deficits ipsilateral or contralateral to the vestibular lesion
ipsilateral
signs of peripheral vestibular disease
- nystagmus: horizontal or rotary, non-positional, conjugate, fast phase contralateral to lesion
- head tilt: toward the lesion
- strabismus: ventral or ventrolateral, dysconjugate ipsilateral to lesion
- ataxia
- 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
signs of bilateral peripheral vestibular disease
- crawling/crouching posture
- symmetrical ataxia
- wide head excursions from side to side
- absent physiologic nystagmus (no afferent input)
signs of central vestibular disease
- head tilt toward lesion
- strabismus: ventrolateral dysconjugate ipsilateral to lesion
- ataxia - asymmetrical without weakness
- nystagmus: vertical, positional, dysconjugate
- can be any of the other - altered mentation
- CN V and VII deficits
- long tract signs (CP deficits, paresis/paralysis) ipsilateral to lesion in TL and PL
- cerebellar signs: hypermetria, intention tremor, absent menace ipsilateral to lesion
paradoxical vestibular disease
form of CENTRAL vestibular disease where vestibular signs are contralateral to lesion
ipsilateral: CN deficits, CP deficits, hemiparesis
contralateral: vestibular signs (head tilt, circling)
auditory disease
impairment of hearing +/- apparent behavioral problems
peripheral deafness
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
what test is used to diagnose peripheral deafness
BAER
brainstem auditory evoked response
central deafness
rare
caused by bilateral temporal lobe or brainstem lesions
difficult to localize
diagnostics for peripheral vestibular disease
PE, neuro exam, minimum database, otoscopic exam
CT: evaluate skull and bulla
MRI: soft tissue structures
diagnostics for central vestibular disease
PE, neuro exam, minimum database, otoscopic exam
MRI is gold standard - evaluates ST structures (brain)
DDX for peripheral vestibular disease
- 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
canine idiopathic vestibular disease
“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
feline idiopathic vestibular disease
unilateral or bilateral disease with unknown cause
similar to canine
DDX for central vestibular disease
- neoplasia
- nutritional –> thiamine deficiency
- infectious –> extension of bacterial otitis media/interna into the brainstem OR FIP*
- inflammatory –> MUE (GME, NE, NME)
- toxic –> metronidazole
peripheral vestibular localizations
- mentation: normal
- CNs: CN VIII, CN VII signs +/- Horner’s
- nystagmus: horizontal or rotary, non-positional, conjugate
- seizures: none
- long tract signs: none
central vestibular localizations
- 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)
