Diseases of the middle and inner ear in small animals

Diseases of the middle and inner ear in small animals are a common challenge for veterinary practitioners. Detailed knowledge of the anatomy and function of the middle and inner ear structures is essential to localize a lesion responsible for symptoms. Inflammation of the middle ear is commonly covered by symptoms of an otitis externa or develops late in the course of the growth of a middle ear mass. Therapy is often long term and relapses are common. Primary diseases like atopy or food allergy should be considered. Feline inflammatory polyps result from ascending infection through the Eustachian tube and extend into the pharynx or through the tympanic membrane into the external ear canal. Surgical intervention at the bulla is often a successful cornerstone, supporting conservative therapy of chronic disease, although the complications (neurological deficits, infection, bleeding) are well known. Careful handling of the structures adjacent to the middle ear is essential to avoid severe complications. The peripheral vestibular syndrome has a good prognosis in dogs and cats; however, the central vestibular syndrome has to be ruled out as a differential. Hereditary and congenital deafness is a well-known problem in small animal breeding. White coat and blue eyes are a highly correlated factor; other gene defects like the Merle factor are known to cause congenital deafness, too. Other reasons for impaired hearing are the exposition to ototoxic drugs or geriatric degeneration in old animals. The possible occurrence of tinnitus has been assumed in small animals but never been proven under clinical conditions. Otoacoustic emissions are a rare finding in dogs, though impressive for the examiner.