Ear Disorders

Deafness—the absence of perception of sound—and reduced hearing are common in dogs and cats, and to a lesser extent in other species. Deafness can be hereditary or acquired, congenital or later onset, and sensorineural or conductive. The most common cause of deafness in dogs and cats is congenital and hereditary, associated with white pigmentation. Adult and geriatric animals are most likely to be affected by otitis, drug toxicity, noise trauma, and presbycusis.

A variety of dermatologic conditions affect the pinna. Rarely, a disease affects the pinna alone or the pinna is the initial site affected. As with all dermatologic conditions, a diagnosis is best made with the results of a thorough history, a complete physical and dermatologic examination, and with careful selection and evaluation of specific diagnostic tests. This overview is not all inclusive but discusses diseases that solely or commonly affect the pinna of domestic animals.

Otitis externa is inflammation of the external ear canal distal to the tympanic membrane; the ear pinna may or may not be involved. It may be acute or chronic and unilateral or bilateral. It is one of the most common reasons for small animals to be presented to the veterinarian. Clinical signs can include any combination of headshaking, odor, pain on manipulation of the ear, exudate, and erythema. It can be seen in rabbits (in which it is usually due to the mite Psoroptes cuniculi) and is uncommon in large animals.

Otitis media, inflammation of the middle ear structures, is seen in small and large domestic animals, including dogs, cats, rabbits, ruminants, horses, pigs, and camelids. It can be unilateral or bilateral and can affect animals of all ages. Although typically sporadic, outbreaks are possible in herds. Otitis media usually results from extension of infection from the external ear canal through the tympanic membrane or from migration of pharyngeal microorganisms through the auditory tube. Occasionally, infection extends from the inner ear to the middle ear, or reaches the middle ear by the hematogenous route. Primary otitis media has been reported in certain breeds of dogs, particularly Cavalier King Charles Spaniels. Untreated otitis media can lead to otitis interna (inflammation of the inner ear structures) or to rupture of an intact tympanic membrane with subsequent otorrhea or otitis externa.

Ear canal tumors may arise from any of the tissues lining or supporting the ear canal, including the squamous epithelium, the ceruminous or sebaceous glands, or the mesenchymal tissues. Malignant tumors arising from the external ear canal and pinna are more common in cats than in dogs.