Vestibular Diseases

Question 1

What is the main function of the vestibular system?

Answer 1

1. maintain balance
2. maintain position of the eyes, neck, limbs and trunk relative to the position or motion of the head

deviations in the vestibular system will affect these functions

Question 2

What bone is the peripheral vestibular system in?

Answer 2

petrous temporal bone

Question 3

What is bony labyrinth filled with?

Answer 3

Perilymph

Question 4

What is the membranous labyrinth filled with?

Answer 4

Endolymph

Question 5

Nystagmus fast phase is toward the Normal or Diseased side?

Answer 5

Fast Phase toward NORMAL side

Question 6

Crista ampullaris is important for what kind of equilibrium?

Answer 6

Dynamic

Question 7

Maculae and saccule are important for what kind of equilibrium?

Answer 7

Static

Question 8

Peripheral Vestib. head tilt

Answer 8

side of lesion

Question 9

Central vestib head tilt

Answer 9

usually toward side of lesion but can be paradoxical and go other side

Question 10

Peripheral vestib nystagmus

Answer 10

horizontal or rotary

Question 11

Central vestib nystagmus

Answer 11

• vertical* is always central

* positional* and changing from any of them

Question 12

Peripheral vestib postural reactions

Answer 12

no deficits

Question 13

Central vestib postural reactions

Answer 13

on side of lesion

Question 14

CN Deficits peripheral vestib

Answer 14

ipsilateral +/- CN 7 since they run together peripherally

Question 15

CN deficits central vestib

Answer 15

ispsilateral CN 5-8

Question 16

Can Horner’s be present in either peripheral or central?

Answer 16

yes

Question 17

Consciousness affected by peripheral or central vestib?

Answer 17

not peripheral

central can be normal to comatose

Question 18

If an animal looks funky and is making WIDE HEAD movements what does that indicate?

Answer 18

they cannot move their eyes, can be two things

1. bilateral peripheral vestib dz
2. blind

CANNOT BE CENTRAL, animal would be comatose if there was a bilateral central lesion in the medulla

Question 19

With Paradoxical Central Vestib. Dz, what side is the lesion on?

Answer 19

side of the postural reaction deficits

Question 20

How can you tell from a distance if disease is central or peripheral?

Answer 20

Head tilt, nystagmus, or vestibular ataxia

Question 21

How do you pursue diagnostics once you discern the lesion is central?

Answer 21

CBC/Chem/UA/T4/BP then follow up with MRI if that’s not definitive enough

Question 22

How do you pursue diagnostics once you discern the lesion is peripheral?

Answer 22

straight to the Otoscopic exam**
if normal –> Tympanic Bullae imaging Rads/US/CT/MRI
if abnormal –> Fluid cytology or mass aspirate

If normal and imaging normal –> Thyroid profile

Question 23

Peripheral vestibular diseases DDX

Answer 23

Anomalous: congenital disease
Metabolic: Hypothyroid dog
Neoplastic: 1˚ Aural, Nerve Sheath or Osteosarcoma
Inflammatory: Otitis Media Interna, nasopharyngeal polyp, idiopathic
Toxic: drugs, almost everything is toxic but don’t realy get that bad of responses to most things

Question 24

What would make you think Anomalous peripheral vestib. dz?

Answer 24

Age: young
Malformation or early onset abiotrophy

No therapy

Question 25

What would make you think Metabolic peripheral vestib. dz?

Answer 25

Other clinical signs of hypothyroidism: - alopecia, loss of hair, obtunded and dull look/mentation Pathophys: Myxomatous compression of nerves, dec. inner ear perfusion, axonal transport defects Dx: T4 fT4, TSH Tx: Levothyroxine supplement (give thyroid hormone/analog) - Will improve in days to months

Question 26

What would make you think of Neoplastic peripheral vestib. dz?

Answer 26

Mass in the ear DX: mass in ear and evidence of bony lysis/infiltration on imaging TX: Sx is primary therapy; +/- radiotherapy; if lymphoma chemo +/- radio

Question 27

Cat or dog more concerning to have aural tumor?

Answer 27

Cats are 85% malignant - SCC | Dogs only 60% malignant - carcinoma

Question 28

What would make you think inflammatory cause of peripheral vestib. dz?

Answer 28

Head-shaking, pawing at ear, exudate, redness, pain at ear bulging, opaque tympanic membrane concurrent facial paresis TX: Anesthesia, deep cleaning and Systemic antibiotics based on C/S - get all underlying factors under control

Question 29

What would make you think idiopathic cause of peripheral vestib. dz?

Answer 29

Old dog - 12y and up, rarely in dogs < 5yo Any age of cats can be affected though, more common in outdoor and late summer, early fall DX: rule out other causes TX: supportive care and physical therapy, clinical improvement in 2 weeks, head tilt may remain

Question 30

What are the main culprits of Central Vestib Dz?

Answer 30

Meningoencephalitis, neoplasia and Stroke account for 80% of central vestib dz. in Adult Dogs recognition of central dz is grounds for *immediate advanced imaging*

Question 31

How many peripheral vestib cases have OMI?

Answer 31

50%

Question 32

How many chronic cases of otitis Externa have OMI?

Answer 32

50%

Question 33

How many OMI cases have otitis Externa?

Answer 33

80%

Question 34

DDX of central vestib dz:

Answer 34

Metabolic: Hypothyroidism Neoplastic: Meningioma, Choroid plexus tumor, glioma Inflammatory: Meningoencephalitis (Distemper, FIP, Protozoal, RMSF); otogenic infections, Granulomatous Meningoencephalitis Toxic: Metronidazole Vascular: Infarcts, Transient ischemic attacks

Question 35

What would make you think metabolic cause of central vestib?

Answer 35

accompanying signs of hypothyroidism

Question 36

What would make you think neoplastic cause of central vestib?

Answer 36

focal central lesion neurolocalization and evidence on CT/MRI

Question 37

What would make you suspect toxic cause of central vestib?

Answer 37

History of metronidazole TX: stop drug (improve 4-12 days); give antidote if necessary Diazepam (improvement 12-48 hr) Rule out metronidazole tox by *giving diazepam* and seeing if central vestib signs go away

Question 38

What is a transient ischemic attack?

Answer 38

Lasts less than 24 hours by definition. caused by vasospasm or stenosis To rule out screen for strokes: hypertension, atherosclerosis, and coagulopathies

Question 39

What is pathophys of hypothyroidism causing central/peripheral acute/chronic vestib signs?

Answer 39

- atherosclerotic cerebrovascular disease -- predisposes to stroke - dec. axonal transport in brainstem white matter