Deafness in cats may be congenital (present at birth) or acquired as a result of infection, trauma, toxins (including certain drugs), or degeneration of the ear.
Deafness present at birth can be inherited or result from toxic or viral damage to the developing unborn kitten. A certain gene in cats causes white fur, blue eyes, and deafness; however, not all blue-eyed white cats are deaf. Deafness in this instance is due to degenerative changes that occur in the first week of life.
Diagnosis of congenital deafness requires careful observation of the cat’s response to sound. In young kittens or in cats kept in groups, deafness may be difficult to detect, because the suspect individual will follow the response of others in the group. If the cat is observed as an individual after an age when responses to sound are predictable (about 3 to 4 weeks), then the deafness may be detected. Cats that are deaf in one ear are especially hard to diagnose without specialized testing.
Acquired deafness may result from blockage of the external ear canal. This occurs in longterm inflammation of the external ear canal (otitis externa), infection of the middle or inner ear, excessive earwax, or damage to the small bones within the ears. Inflammatory polyps can sometimes cause deafness in cats. Deafness in one ear or partial hearing loss, or both, is possible in some of these instances. Removing the blockage or healing the damaged tissue usually restores hearing.
Other causes of acquired deafness result in the loss of the nerve cells necessary for hearing. These types of deafness are permanent. Causes include trauma to the inner ear, infections in the middle or inner ear, loud noises, conditions in which there is a loss or destruction of myelin (the fatty material that surrounds some nerve cells), drugs toxic to the ear (for example, certain antibiotics or aspirin), anesthesia, old age, and tumors involving the ear or brain stem.
Cats with deafness due to bacterial infection may recover hearing after antibiotic treatment. Recovery from other causes varies with the particular disease. There is no effective treatment for congenital deafness. Many cats with partial or complete deafness adapt very well to their condition. However, deaf cats should not be let outdoors except on a leash.
Also see professional content regarding deafness.