Vestibular Disease

Question 1

what are the 3 components of the peripheral vestibular system?

Answer 1

ampulla
utricle
saccule

Question 2

What is the function of the vestibular system? (3)

Answer 2

• maintain posture and balance relative to the head, body, and limbs
• detect acceleration and deceleration
• coordinate eye movements

Question 3

What type of movement does the utricle detect?

Answer 3

horizontal acceleration and deceleration

Question 4

what type of movement does the saccule detect?

Answer 4

vertical movement

Question 5

what type of movement does the ampulla detect?

Answer 5

rotational

Question 6

what is different between the utricle, saccule, and ampulla?

Answer 6

the utricle and saccule both have otoliths that weigh down on the gel surrounding the hair cells.
When acceleration, deceleration, or vertical movement is detected, the otoliths drag the gel and the hair cells move.
This changes the basal rate of information from the hair cells traveling to CN 8 and subsequently to the antigravity muscles.

Question 7

what 2 clinical signs can you see with middle ear disease due to the close proximity of CN 7 and sympathetic innervation of the eye to the middle ear?

Answer 7

facial nerve paralysis (lip drooping, etc.)
and horners syndrome (miosis, ptosis, enopthalmos, and 3rd eyelid protrusion)

Question 8

where does the information received by the utricle, saccule, and ampullae travel to?

Answer 8

travels through CN 8 to the vestibular nuclei within the medulla oblongata and flocculonodular lobe.
From there, it travels to 3 different places – to CN 3, 4, and 6 nuclei to control ocular reflexes; to the cerebellum for fine tuning of vestibular reflexes; and to the spinal cord to the antigravity muscles to make postural adjustments.

Question 9

what are clinical signs of vestibular disease?

Answer 9

• abnormal posture
• vestibular ataxia
• strabismus
• nystagmus
• nausea

Question 10

why is consciousness altered with CENTRAL vestibular disease and not PERIPHERAL vestibular disease?

Answer 10

the central vestibular system is located in close proximity to the RAS.
Any lesion that affects the RAS will change mentation.

Question 11

why is their loss of balance with vestibular disease?

Answer 11

when a lesion is present in the vestibular system, there is LOSS of excitation from one side, meaning LESS tone to antigravity muscles which causes falling/leaning/rolling.

Question 11

what 2 exam findings are most important in differentiating between peripheral and central vestibular disease?

Answer 11

1. Postural rxns – normal in peripheral with good strength; deficits ipsilateral to lesion and paresis with central
2. Consciousness – normal in peripheral, normal-comatose in central

Question 12

what is the most common type of strabismus seen with vestibular disease?

Answer 12

ventrolateral

Question 13

What is the difference in nystagmus between a peripheral vestibular lesion versus a central vestibular lesion?

Answer 13

Peripheral – nystagmus can be rotary or horizontal and the fast phase is AWAY from the lesion

Central – nystagmus is usually vertical, but can change with head position, the phase phase can also be in any direction and can change.

Question 14

what is the best imaging option if you suspect a central vestibular lesion?

Answer 14

MRI

Question 15

when performing a myringtomy on a patient that has has chronic recurrent otitis interna, why do e insert the needle into the pars tensa rather than any other portion of the typanum?

Answer 15

the pars tensa has less vasculature.

Question 16

what 2 organisms are most commonly involved in otitis media/interna?

Answer 16

pseudomonas aeruginosa and staph pseudintermedius are most common.

others include: E. coli and klebsiella

Question 17

what is the non-infectious form of otitis media/interna called?

Answer 17

primary secretory otitis media (PSOM) / otitis media with effusion / glue ear

Question 18

what is the difference in treatment for non-infectious and infectious otitis media/interna?

Answer 18

Both are given oral antibiotics. Non-infectious causes may require a myringotomy, and if either causes are recurrent, a TECA + BO may be indicated.

Empirical tx is usually with clavamox or baytril, but it is best to base it on culture.

Question 19

Why do inflammatory polyps cause peripheral vestibular signs?

Answer 19

the polyp blocks drainage of fluid, the fluid accumualtes and causes infection. If severe enough, it can cause meningitis.

Question 20

what is the treatment for inflammatory polyps causing peripheral vestibular signs?

Answer 20

remove with traction or bulla osteotomy.

Add antibiotics if otitis media is present and add in prednisolone to decrease the recurrence chances.

Question 21

what is the BEST treatment option for aural neoplasia causing peripheral vestibular signs?

Answer 21

radiation

sx resection is not the best option

Question 22

A 9 yo dog presents to your clinic with acute onset of vestibular signs. After many diagnostics, you diagnose this dog with idiopathic vestibular disease. What is the treatment and what should you tell the owners about in regards to his prognosis?

Answer 22

tx = symptomatic for nausea +/- epileen maneuver

you should tell the owners that most patients have spontaneous remission in 1-2 weeks, but may have a residual head tilt or mild ataxia.

Question 23

T/F: toxicities (aminoglycosides, diuretics, NSAIDs, chemo, chlorhexidine, etc.) can cause damage to the hair cell receptors of the peripheral vestibular system and this damage is permanent.

Answer 23

true

Question 24

what is the MOST common cause of central vestibular disease?

Answer 24

infectious causes creating inflammation (ie meningitis)

Question 25

what is the most common intracranial tumor that can lead to central vestibular signs?

Answer 25

meningioma

Question 26

what is the pathophysiology of thiamine deficiency causing central vestibular signs in cats?

Answer 26

diets high in thiaminases (fish diets) or diets excessively heated or processed in sulfites cause CENTRAL NECROSIS OF VESTIBULAR NUCLEI.

Question 27

what drug, at high doses, can cause central vestibular signs?

Answer 27

metronidazole

Question 28

what is the treatment for metronidazole toxicity?

Answer 28

diazepam for 3 days (diazepam binds to the receptors metronidazole is binding to and reverses the clinical signs)

treatment is rewarding and prognosis is good. there is not usually any permanent damage.

Question 29

T/F: vascular causes of central vestibular disease have an acute onset

Answer 29

true