Vestibular disease Flashcards
What does the vestibular apparatus coordinate?
- Allows for maintenance of posture and balance relative to the head, body and limbs
- Detects acceleration and deceleration
- Coordinates eye movement
Where does the vestibular apparatus lie?
Directly above the middle ear
What are the 3 portions of the vestibular apparatus?
Utricle, Saccule, Ampula
Which portion of the peripheral vestibular apparatus can detect rotational movement in any direction?
Ampulla
Which two structures form the central vestibular apparatus?
The vestibular nucleus (in medulla oblongata) and the floculonodular lobe
What does the vestibular apparatus allow for in terms of the eyes?
Physiologic nystagmus and the oculocephalic reflex
Why can you get facial nerve paralysis with vestibular disease?
Facial nerve is in very close proximity to the vestibular nucleus and vestibulocochlear nerve
What are the 4 main clinical signs associated with horners syndrome?
Miosis, Ptosis, enopthalmos, 3rd eyelid protrusion
What are the main clinical signs associated with dysfunction of the vestibular system?
Abnormal posture, vestibular ataxia, strabismus, nystagmus
How can dysfunction of the vestibular system lead to nausea?
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
What type of receptors lie on the vestibular nucleus?
Muscarinic and histamine
What type of receptors lie on chemoreceptor trigger zone?
serotonin, dopamine, nk1
What type of receptors lie on vomiting center?
NK-1, muscarinic
Where does dramamine act to prevent vomiting?
It is an antihistamine that acts on the histamine receptors on the vestibular nucleus
How does maropitant prevent vomiting?
It acts on the neurokinin 1 receptors in the CTZ and vomiting center
How does ondansetron prevent vomiting?
It is a serotonin inhibitor which acts on the serotonin receptors in the CTZ
How does metaclopramide prevent vomiting?
It acts on the dopamine receptors in the CTZ
How do central vs peripheral vestibular diseases affect conciousness?
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
What abnormal postures/gaits are often associated with vestibular disease?
Asymmetric input, head tilt (towards side of lesion), circling rolling and leaning towards lesion, vestibular ataxia
How will the gait be different if the central vs peripheral vestibular system is affected?
Peripheral: vestibular ataxia but good strength. No postural deficits
Central: vestibular ataxia, tetra or hemiparesis, proprioceptive deficits (ipsilateral), hemi/tetraparesis
What does vestibular strabismus look like?
Abnormal eye position (vetrolateral)- can be resting or positionally induced
Compare and contrast central and peripheral vestibular nystagmus
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
What other cranial nerves are affected in peripheral vs central vestibular disease?
Peripheral: facial nerve
Central: multiple cranial nerves (V-XII)
Describe the common causes of peripheral vestibular disease using DAMNITV scheme
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
Describe the diagnostic approach for peripheral vestibular disease.
Start with otoscopic exam, then bulla radiography (DV, open-mouth), BAER test, myringotomy with cytology and culture
What are the main infectious agents that lead to otitis media/interna?
Pseudomonas aeruginosa, staph pseudintermedius, ecoli, klepsiella
How do you best treat otitis media/interna?
oral antibiotics (based on C/S). Can start empirically on clavamox or baytril, myringotomy, or TECA-BO for recurrent episodes
Where do you enter for a myringotomy?
Caudoventral region of pars tensa
What are the indications for a myringotomy?
Chronic infection, intact tympanum, fluid and bulging membrane
Describe inflammatory polyps
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
What are the common aural neoplasias?
Fibrosarcoma, chondrosarcoma, osteosarcoma, ceruminous gland adenocarcinomas, SCC
Who is most affected by idiopathic vestibular disease?
Older cats and dogs-acute onset
-can undergo spontaneous remission over 1-2 weeks
-may be due to cuterebral larval migran
What are the main toxins that can lead to vestibular signs?
Aminoglycosides mainly, fursemide, some NSAIDs, cisplatin
What are the main causes of central vestibular disease?
Arachnoid cysts, COMS, hydrocephalus, hypothyroidism, primary intracranial neoplasia, metastatic disease, thiamine deficiency, infectious causes, brainstem disease, metronidazole, cerebrovascular accident
Describe the diagnostic approach for central vestibular disease
Cross sectional imaging, CSF analysis, referral
Describe the potential pathogenesis of peripheral and central vestibular signs due to hypothyroidism
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
What are the common intracranial neoplasias leading to vestibular signs?
Meningioma, choroid plexus tumor, ependymoma, lymphoma
What diet can lead to a thiamine deficiency in cats?
Fish only
What is the anectote for metronidazole toxicity?
Diazepam
