Definition and Causes of Deafness in Cats
Deafness is defined as the lack or loss of the ability to hear. It can be partial or complete and can affect one or both ears. Cats have a much different range of hearing than humans. People can hear sounds between about 20 Hz (low sounds) and 20 kHz (high sounds). By comparison, cats can hear sounds ranging from somewhere around 48 Hz (on the low end) and 85 kHz (on the high end), which is a larger span on the high end of the sound spectrum. Deafness can be genetic and runs in families in many cat breeds. Some animals are born partially or completely deaf in one or both of their ears because of developmental defects in their ear structures and/or in the associated nerves that are responsible for normal hearing. Cats with white coats and blue eyes are predisposed to being deaf from birth, although not all of them are. Long-haired blue-eyed white cats seem to have an especially higher chance of being born with hearing impairments than their shorter-haired counterparts.
Cats with normal hearing can develop partial or complete hearing loss in one or both ears later in life, for a number of different reasons. These may include:
- Ear infections
- Ruptured eardrums
- Traumatic head injuries
- Ingestion of certain drugs or poisons
- Accumulation of ear wax, fluid, dirt and/or other debris in the ear canals
- Abnormalities in or damage to one or more of the nerves involved with processing and transmitting sound
- Structural defects in or damage to one or more of the structures of the outer, middle or inner ear
- The normal process of aging. While geriatric cats often gradually lose their ability to hear many sounds, they tend to retain their ability to hear high-pitched sounds that even people can’t appreciate.
Symptoms and Signs of Deafness in Cats
Feline deafness can be categorized as either conductive or sensorineural. If sounds can’t travel or be processed properly in the outer or middle ear, the problem is said to be conductive. Cats with conductive deafness usually only have partial hearing loss, which may be able to be managed or even corrected medically or surgically. When the inner ear is affected, most cats either are deaf from birth or lose all of their ability to hear over time. This is called sensorineural deafness. Cats born without any ability to hear won’t react to sounds. However, they may still react to vibrations caused by sounds movement, such as when a person stomps on the floor or drops something heavy near the cat while it is resting or sleeping. Cats that born with normal (or largely normal) hearing but later become hearing-impaired usually lose their hearing slowly over months to years. Cats with full hearing usually flick or twitch their ears involuntarily in response to sound (this is called "Pryor's reflex”). Deaf cats won’t swivel their ears toward the source of sounds. Cats with hearing loss are sound sleepers. Soft, medium or even loud noises might not wake them, and they won’t come to their owners when called. Cats that only wake up when they are touched may be developing hearing problems.
Diagnosing Deafness in Cats
Deafness can be difficult to assess accurately in companion cats. It is particularly hard to evaluate hearing loss in a cat that only is deaf in one ear, or is only partially deaf in both ears. A cat’s failure to obey normal commands (such as “Here, Kitty Kitty…) and respond to noises strongly suggests that it has or is developing some sort of hearing problem. Some veterinary teaching hospitals and specialized veterinary referral centers have the ability to evaluate a cat’s hearing using a highly sensitive procedure known as the Brainstem Auditory Evoked Response (BAER) test. This involves using an electroencephalogram (EEG) to measure and record the cat’s brain waves that are produced in response to a variety of clicking sounds made at different frequencies and directed through earphones or a foam-like insert into the cat’s ears. If the cat’s brain waves don’t change when these assorted sounds are made, then it isn’t hearing them. BAER testing can also reveal partial hearing loss in one or both of a cat’s ears. The procedure is relatively painless and only takes 15 to 30 minutes to administer. However, it can be expensive. Many owners choose to rely on a presumptive observational diagnosis of deafness, but BAER testing is available for those who would like to be more certain.
Owners who think that their cat has a hearing problem should consult with its veterinarian. Only a skilled professional can thoroughly evaluate whether a cat has lost some or all of its ability to hear and, if so, to recommend what can be done about it. Hearing loss is not normally life-threatening, but it is important to rule out other underlying medical problems. It’s also important to keep deaf cats indoors, well-contained or well-restrained. If left to wander the neighborhood freely, they can easily be hit by cars or fall victim to animal attacks because they simply can’t hear the danger approaching.
Treatment and Prognosis
Cats are gifted with a fairly unique ability to rely on their other senses to make up for ones they have lost. Many cats that have been diagnosed with hearing loss live full, happy lives. They can be taught to respond to hand signals, facial expressions or even flashlights. Owners will need to change some of the ways in which they handle and interact with their deaf cat, but there are more success stories than failures.