Deafness is quite common in cats. Around three in every four white cats are deaf because of a defective gene that causes the inner ear to fail to develop normally. Some of these cats are deaf in only one ear and their owners will often not realise that there is a problem.
Deafness is also common in older cats, probably due to age-related degeneration in the inner ear, as seen in older people.
Other reasons for deafness are less common in cats than in people or dogs. Long-term ear infections, growths in the middle ear or external ear canal and medications given by veterinary surgeons to treat these conditions are probably all important causes. Head trauma and brain tumours are possible causes. However, deafness can result from anything that damages the conduction of sound waves from the ear hole through the ear canal and ear drum to the bones of the middle ear or which affects the conduction of impulses through the nerves to the brain.
Deafness in one ear is not usually detected and actually causes few problems. If the cat is lying curled up with her good ear buried and the deaf one exposed then her hearing would be impaired and an owner may notice a lack of response to noises. However, cats who are deaf in one ear probably take care to avoid lying in such a position and generally keep their good ear pointing in the right direction, even when relaxed at home.
Being deaf in both ears causes more significant problems and most owners notice that their cat does not respond to noises – the opening of doors, the fridge, food packages, calling their name etc. and fail to respond to noisy people, animals and machinery. Deaf cats tend to ‘sleep well’. Many cats will wake to some extent when someone enters a room, even if it’s just a slight opening of an eye or a twitch of the ear; deaf cats will tend to remain sleeping. This is something that owners of older cats may notice as their pet’s hearing deteriorates with age.
A common finding is that deaf cats do not mind vacuum cleaners and it is quite unusual for cats to be completely comfortable when hoovering is going on near them. Some deaf cats even enjoy the sensation of actually being groomed by a hand-held vacuum cleaner. Of course there are some hearing cats that tolerate these sorts of things and this may be more common in some breeds – for example Ragdolls. Owners of old cats may notice that they now tolerate the noise of a vacuum cleaner when previously they did not – this may be the most obvious sign of growing deafness.
Similarly, deaf cats may make odd noises because they can’t hear what they are saying. One of the reasons for older cats starting to howl and yell around the house may be deafness or an owner may just notice that their older cat is making a different cry than they did when they were younger – but there are other possible causes for this besides deafness.
Hearing can be tested by observing the reaction the cat makes to a sudden, unexpected loud noise. A hearing cat is expected to turn its ears towards the noise, and may also move their whole head and possibly move their body into a more alert position.
There are problems with this test. It cannot detect deafness in a single ear, only a totally deaf cat will fail to react. It is also possible to think that a deaf cat can hear if, for example, it reacts to a visual clue if it sees an object being dropped or hands being clapped or it may be able to feel vibrations when something hits the floor. The opposite might also happen – a well-adjusted, non-fearful and relaxed cat may react to a first noise but will quickly react less and less obviously to subsequent noises.
This test will be easier to interpret in a cat well known to the owner in its normal environment and is more difficult to interpret in, for example, a kitten amongst its littermates or a kitten newly introduced into a house or a cat being examined in an unfamiliar veterinary practice.
The only truly reliable test is one similar to that used for the testing of hearing in humans and involves sophisticated equipment available only in a few centres. Your veterinary surgeon would be able to advise you of a centre that offers testing if necessary.
The test is well tolerated by most cats but involves playing noises into each ear in turn and then detecting the nervous impulses invoked by these noises in the brain. It is called BAER (Brainstem Auditory Evoked Response) testing. This test will not be necessary for the vast majority of cats with a suspected hearing problem as testing will not usually make any difference to the cat or how they are helped and managed.
Cats with normal hearing use the sounds detected by both ears to accurately pinpoint sounds. They use this skill in hunting to detect prey when it is out of sight, for example in long grass. Hunting ability may be reduced in cats with impaired hearing but there are many other factors that will affect this success (time dedicated to hunting and the number of available prey, for example).
When a cat is deaf in both ears it is much more significantly handicapped. Vocalization is an important way of communication between cats and deaf cats may be less good at communicating. Of course, visual clues of ‘body language’ and olfactory clues from pheromones and scent marking are important in cats so this miscommunication may not be obvious. But deaf cats might get into fights more often or be socially ostracized within a group. They may find it more difficult when young kittens and are more likely to be rejected by their mother.
The reduced ability to recognize danger is probably the most serious handicap faced by totally deaf cats especially if they have to face the hazards of the outdoor environment. Apart from other cats, which have been mentioned above, road vehicles and dogs are probably the greatest dangers. Both cars and dogs are usually noisy and being able to hear this danger is an important clue for normal cats. Further examples of dangerous noisy items are farm and garden machinery, household appliances and trains.
As mentioned above, hunting is a natural feline behaviour and one which will be significantly affected by being totally deaf. However, being deaf will not totally stop hunting success and cats that enjoy hunting will not be put off by their failures.
It is unlikely that there will be a treatment to help deafness in your cat. The most common causes – a genetic defect or age-related degeneration – have no appropriate treatment. It is only some of the unusual causes such as disease blocking the passage of sound through the external ear canal from infection, or a resectable mass that can be helped by treatment.
Cats with these conditions will usually have other obvious signs of disease rather than deafness being the major problem noticed by owners. They will have ears that are dirty, smelly and irritating. The cat may scratch and shake its head or might also have a head tilt, usually to the side with the greatest problem. Other signs of underlying disease include wobbliness, from damage to the balance organs, which are also found in the inner ear.
Cats that are deaf in just one ear can be treated just as normal but totally deaf cats should have some special care. The main difference is that deaf cats cannot go outside without running greater risks from common problems and so should be kept indoors for life. Most cats can live happily indoors, although a few cats that are used to being outside much of the time can be significantly stressed by being confined.
Some cats are more likely to be deaf, so avoid obtaining a totally white kitten from a breeder. Buying this kitten may just encourage irresponsible breeding. If there is a rescued or stray cat that may be deaf and you think that you can offer a suitable safe environment for her then that is different.
Any white cat should be checked for deafness prior to breeding. This is where BAER testing is important because only cats with normal hearing in both ears should be bred and BAER testing is the only reliable way to check for deafness in one ear. Cats that are deaf in just one ear are significantly more likely to have deaf kittens than cats with normal hearing.
Deafness causes significant welfare problems and breeders should aim to avoid producing kittens likely to be deaf. However, individual deaf cats can be given a reasonable quality of life by thinking about their special needs. Deafness is also quite common in older cats and considering this is one aspect of providing a good home for a geriatric companion.