B. Small animals: Usually bacterial extension from otitis externa/media.

C. Treatment consists of long term antibiotic therapy, preferably based on culture and sensitivity. A minimum of 6 weeks therapy is usually required. Refractory otitis may require surgical intervention (bulla osteotomy/canal ablation).

2. Aural cholesteatoma: A form of epidermoid cyst that may be associated with otitis-media. Surgery may be required.

Idiopathic

1. Canine idiopathic vestibular disease: "Old dog vestibular disease". Often misdiagnosed as a "stroke". Usually an acute or peracute onset that may be preceded by nausea and/or vomiting. The cause is unknown and diagnosis is by exclusion of other causes of peripheral vestibular disease. Treatment is supportive and prognosis is good with improvement seen in 72 hours and recovery usually in 10-14 days. A residual head tilt may be present. NB there should be no CN VII or sympathetic signs.

2. Feline idiopathic vestibular disease. There is no breed, age or sex predisposition, and disease may be unilateral or bilateral. Incidence is higher in July and August in the NE USA. Cause is unknown, and diagnosis, treatment and prognosis is similar to the canine disease.

Trauma

Involving petrous temporal bone. Signs can be very severe with marked circling/rolling, often requiring sedation. Sympathetic and CN VII signs may be seen. There may be otoscopic and radiographic/CT evidence of fractures and hemorrhage. Treatment is mainly supportive, and prognosis can be good if there is no central involvement.

Toxic

Ototoxicity may cause hearing loss, vestibular dysfunction or both. Topical therapy is the most common cause, however oral and parenteral toxicity is possible. Many drugs/agents are potentially toxic; the most common ones include the aminoglycoside antibiotics that can affect the hair cells, flocculonodular lobe and fastigial nucleus. Streptomycin tends to have vestibular effects, whereas neomycin, gentamycin, kanamycin, vankomycin tend to have more effect on the auditory system. Loop diuretics, cisplatin, propylene glycol and chlorhexidine have also been implicated in ototoxic disease. Treatment is to discontinue the use of the drug. Most hearing loss is permanent, however vestibular dysfunction if present may resolve. It is important to avoid application of topical agents into the external ear if the tympanic membrane is not intact, is inflamed or cannot be visualized. Use the safest drugs at appropriate doses. Most toxicity is associated with overdosage and prolonged exposure.

Note. Ototoxicity from topical agents may occur even if the tympanic membrane is intact!

Vascular

"Stroke" is a misnomer when used to refer to peripheral vestibular disease in dogs. The term refers to human cerebrovascular disease associated with chronic vascular disease leading to the acute blockage of a cerebral blood vessel or its rupture and subsequent hemorrhage. It occurs uncommonly in animals and signs should be referable to a central lesion (brainstem or cerebrum).

Diseases Causing Central Vestibular Dysfunction

Degenerative

Storage diseases. Inherited diseases of dogs and cats due to deficiency of a lysosomal enzyme. Slowly progressive onset usually before 1 year of age. Progressive disease with no treatment. Extremely RARE.