Deafness is the inability to hear and can be caused by either conduction or neurologic abnormalities.
Conduction deafness is caused by abnormalities of the pinna (external ear), ear canal, tympanic membrane (eardrum), auditory ossicles or middle ear. Waxy debris occluding the ear canal, tympanic membrane, and severe ear infections are all examples of diseases causing conduction deafness.
Neurologic or sensorineural deafness is caused by abnormalities of the inner ear, auditory nerve or in the brain itself. Inherited deafness, drug toxicity and age-related deafness are diseases causing sensorineural deafness.
Deafness can be unilateral (affecting one ear) or bilateral (affecting both ears). Unilateral deafness is difficult to recognize without specialized equipment. Because of the cost of the equipment, testing is generally limited to veterinary referral hospitals, specialists and university clinics.
There are over 35 breeds of dogs reported to have hereditary sensorineural deafness. Breeding dogs should be tested for deafness. Animals found to have inherited deafness in one or both ears should be removed from breeding programs.
White-haired, blue-eyed cats have a higher incidence of deafness than the general feline population.
What to Watch For
Shaking the head or pawing at the ears
Diagnosis
Diagnostic tests are needed to determine the ability to hear and the presence of an underlying disease or cause of the deafness.
Deafness can be assessed by observing the animal's behavioral response, such as lifting or turning the head, after making a noise out of the animal's view. Dogs suspected of being bilaterally deaf can be challenged with sounds of increasing intensity from different directions. Be careful not to make sounds that can be "felt" through vibrations.
Animals suspected of having hearing deficits should have a thorough otic (ear) and neurologic examination performed. The ear canal and tympanic membrane can be examined with an otoscope for ear wax accumulation, foreign bodies, infections or inflammation.
Other diagnostic tests may be recommended based on the results of the history and physical examination.
Treatment
Results of the history, physical examination and initial tests will determine the need for further diagnostic tests and will help determine the appropriate treatment for your pet's deafness.
Conduction deafness can be corrected if the cause, such as wax accumulation or infection, can be eliminated. Cleaning the ears should be done with care to prevent damage to the eardrum. Only well-trained and knowledgeable people should use cotton-tipped applicators such as Q-tips to clean the ears. Caution should be used. Dogs with severely dirty ears may need to be cleaned under anesthesia by a veterinarian.
Infection may need to be treated locally (in the ear canal) and systemically with antibiotics.
Sensorineural deafness cannot be reversed with medications, surgery, or hearing aids. Hearing aids have been used in dogs and cats but the majority of the animals do not tolerate the presence of the hearing aid in the ear canal.
Home Care
Testing can be done at home to assess hearing. Remember that your pet may "feel" sounds such as a door slamming or steps across a hardwood floor.
Treatment prescribed by your veterinarian should be performed as directed. Medications should be given as directed until finished.
Dogs that are born deaf can be trained to respond hand signals. A bell can be attached to a deaf animal's collar so that if he gets away he can be found.
Deaf animals need to be closely supervised especially around traffic since they cannot hear dangers such as cars.
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