Pathogenesis
Etiology
- Autosomal inheritance in congenital peripheral vestibular disease.
- Immune-mediated disease.
- Transitory labyrinthitis.
- Endolymphatic fluid dynamic abnormality within labyrinthine organ.
- Neuritis of the vestibular portion of facial nerve VIII.
- Metabolic, ie hypothyroidism.
- Foreign body related.
- Secondary to nasopharyngeal polyps.
- Extension of opportunistic infection byStaphylococcusspp,Streptococcusspp,P. canis,Clostridium welchiiand especiallyPseudomonas aeruginosa.
- Neoplasia.
- Head trauma (rare).
Geriatric vestibular disease
- Results from abnormal flow of endolymphatic fluid in the semicircular canals of the inner ear secondary to either:
- Disturbance in production, circulation or absorption of the fluid.
- Intoxication of vestibular receptors and inflammation of the vestibular nerve.
Iatrogenic damage during the treatment of middle ear disease
- Trauma from excessive pressure from overzealous irrigation.
- Use of ototoxic compounds in irrigation of middle ear.
Sudden onset idiopathic otitis interna
- Extension of an infection of the external ear through either the tympanic membrane or the oral and nasopharyngeal cavities via the eustachian tubes.
- Hematogenous spread of infectious agent, possibly a virus.
- Hematogenous spread of a systemic infection.
- See under otitis interna Otitis interna , canine geriatric vestibular disease, metronidazole toxicity, aminoglycoside toxicity, neoplasia, trauma (especially iatrogenic) and congenital peripheral vestibular disease.
Predisposing factors
General
- Old dogs.
- Dogs which are prone to otitis externa, ie the German Shepherd dog, dogs with pendulous or hairy ears, dogs with generalized skin conditions (especially atopy).
- Inhalant anesthesia may change the pressure of the middle ear and predispose to infection.
Specific
- Otitis media.
- Bulla irrigation or bulla osteotomy.
Pathophysiology
- See under otitis interna Otitis interna , canine geriatric vestibular disease, metronidazole toxicity, aminoglycoside toxicity.
Neoplasia
- Space occupying lesion → pressure on surrounding nervous tissue → compromised blood supply and anoxia of nervous tissue or direct pressure trauma to nervous tissue → loss of function.
Congenital peripheral vestibular disease in Dobermann, Japanese Akita and Beagle
- Autosomal recessive inheritance → non-inflammatory neuroepithelial degeneration of the cochlea with a progressive loss of auditory sensory hair cells → almost complete loss of organ of Corti by 11 weeks of age → bilateral, severe, permanent deafness and vestibular signs which improve as dog learns to compensate.
Congenital peripheral vestibular disease in Dobermann/lymphocytic labyrinthitis
- Lymphocytic labyrinthitis (otitis interna) → multiple lymphocytic aggregates in the lamina.
- Multiple lymphocytic aggregates in the lamina propria underneath the ciliated columnar epithelium of the inner ear → loss of function, deafness and vestibular signs.
Timecourse
- Usually acute onset - may occur over several hours.
Diagnosis
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Treatment
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Prevention
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Outcomes
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