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SA Optho/Neuro > Vestibular disease > Flashcards

Vestibular disease Flashcards

1
Q

What does the vestibular apparatus coordinate?

A
  1. Allows for maintenance of posture and balance relative to the head, body and limbs
  2. Detects acceleration and deceleration
  3. Coordinates eye movement
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2
Q

Where does the vestibular apparatus lie?

A

Directly above the middle ear

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3
Q

What are the 3 portions of the vestibular apparatus?

A

Utricle, Saccule, Ampula

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4
Q

Which portion of the peripheral vestibular apparatus can detect rotational movement in any direction?

A

Ampulla

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5
Q

Which two structures form the central vestibular apparatus?

A

The vestibular nucleus (in medulla oblongata) and the floculonodular lobe

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6
Q

What does the vestibular apparatus allow for in terms of the eyes?

A

Physiologic nystagmus and the oculocephalic reflex

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7
Q

Why can you get facial nerve paralysis with vestibular disease?

A

Facial nerve is in very close proximity to the vestibular nucleus and vestibulocochlear nerve

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8
Q

What are the 4 main clinical signs associated with horners syndrome?

A

Miosis, Ptosis, enopthalmos, 3rd eyelid protrusion

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9
Q

What are the main clinical signs associated with dysfunction of the vestibular system?

A

Abnormal posture, vestibular ataxia, strabismus, nystagmus

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10
Q

How can dysfunction of the vestibular system lead to nausea?

A

The vestibular nucleus, chemoreceptor trigger zone and vomiting center all live within the medulla oblongata
-activation of vestibular nucleus can stimulate CTZ which then stimulates vomiting center

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11
Q

What type of receptors lie on the vestibular nucleus?

A

Muscarinic and histamine

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12
Q

What type of receptors lie on chemoreceptor trigger zone?

A

serotonin, dopamine, nk1

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13
Q

What type of receptors lie on vomiting center?

A

NK-1, muscarinic

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14
Q

Where does dramamine act to prevent vomiting?

A

It is an antihistamine that acts on the histamine receptors on the vestibular nucleus

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15
Q

How does maropitant prevent vomiting?

A

It acts on the neurokinin 1 receptors in the CTZ and vomiting center

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16
Q

How does ondansetron prevent vomiting?

A

It is a serotonin inhibitor which acts on the serotonin receptors in the CTZ

17
Q

How does metaclopramide prevent vomiting?

A

It acts on the dopamine receptors in the CTZ

18
Q

How do central vs peripheral vestibular diseases affect conciousness?

A

Patients with central vestibular disease can be alert, disoriented, obtunded, stuporous or comatose (AKA altered conciousness=central)

Patients with peripheral are alert, but may be slightly disoriented

19
Q

What abnormal postures/gaits are often associated with vestibular disease?

A

Asymmetric input, head tilt (towards side of lesion), circling rolling and leaning towards lesion, vestibular ataxia

20
Q

How will the gait be different if the central vs peripheral vestibular system is affected?

A

Peripheral: vestibular ataxia but good strength. No postural deficits

Central: vestibular ataxia, tetra or hemiparesis, proprioceptive deficits (ipsilateral), hemi/tetraparesis

21
Q

What does vestibular strabismus look like?

A

Abnormal eye position (vetrolateral)- can be resting or positionally induced

22
Q

Compare and contrast central and peripheral vestibular nystagmus

A

Peripheral: horizontal/rotary with fast phase away from the lesion

Central: horizontal/rotary/vertical. Changes in the direction of movement change with head position, though fast phase often away from head tilt

23
Q

What other cranial nerves are affected in peripheral vs central vestibular disease?

A

Peripheral: facial nerve

Central: multiple cranial nerves (V-XII)

24
Q

Describe the common causes of peripheral vestibular disease using DAMNITV scheme

A

A- congenital vestibular disease
M-hypothyroidism
N-aural neoplasia, malignant nerve sheath tumor
I: otitis media/interna, nasopharyngeal polyp, PSOM
I: idiopathic
T: inner ear trauma
T- ototoxic drugs

25
Q

Describe the diagnostic approach for peripheral vestibular disease.

A

Start with otoscopic exam, then bulla radiography (DV, open-mouth), BAER test, myringotomy with cytology and culture

26
Q

What are the main infectious agents that lead to otitis media/interna?

A

Pseudomonas aeruginosa, staph pseudintermedius, ecoli, klepsiella

27
Q

How do you best treat otitis media/interna?

A

oral antibiotics (based on C/S). Can start empirically on clavamox or baytril, myringotomy, or TECA-BO for recurrent episodes

28
Q

Where do you enter for a myringotomy?

A

Caudoventral region of pars tensa

29
Q

What are the indications for a myringotomy?

A

Chronic infection, intact tympanum, fluid and bulging membrane

30
Q

Describe inflammatory polyps

A

They often originate in the middle ear, nasopharynx or combo
-lead to upper airway signs and otitis externa
-removed with traction or bulla osteotomy but may recur

31
Q

What are the common aural neoplasias?

A

Fibrosarcoma, chondrosarcoma, osteosarcoma, ceruminous gland adenocarcinomas, SCC

32
Q

Who is most affected by idiopathic vestibular disease?

A

Older cats and dogs-acute onset
-can undergo spontaneous remission over 1-2 weeks
-may be due to cuterebral larval migran

33
Q

What are the main toxins that can lead to vestibular signs?

A

Aminoglycosides mainly, fursemide, some NSAIDs, cisplatin

34
Q

What are the main causes of central vestibular disease?

A

Arachnoid cysts, COMS, hydrocephalus, hypothyroidism, primary intracranial neoplasia, metastatic disease, thiamine deficiency, infectious causes, brainstem disease, metronidazole, cerebrovascular accident

35
Q

Describe the diagnostic approach for central vestibular disease

A

Cross sectional imaging, CSF analysis, referral

36
Q

Describe the potential pathogenesis of peripheral and central vestibular signs due to hypothyroidism

A

Peripheral: myxomatous compression of cranial nerves at foraminal level (may have signs of polyneuropathy or facial paralysis)

Central: ischemic infarction secondary to atherosclerosis disease, CNS demyelination

37
Q

What are the common intracranial neoplasias leading to vestibular signs?

A

Meningioma, choroid plexus tumor, ependymoma, lymphoma

38
Q

What diet can lead to a thiamine deficiency in cats?

A

Fish only

39
Q

What is the anectote for metronidazole toxicity?

A

Diazepam

SA Optho/Neuro (8 decks)

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