Deafness (Hearing Loss) in Dogs
Overview of Deafness (Hearing Loss) in Dogs
Deafness is the inability to hear and can be caused by either conduction or neurologic abnormalities. In dogs, there are several causes which include:
- 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
- Not responding to spoken commands
- Responding only when the pet can see you
- Sleeping more than normal
- Not waking unless you physically touch them
- Turning in the wrong direction when you call them
- Shaking the head or pawing at the ears
Diagnosis of Deafness in Dogs
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 of Deafness in Dogs
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.
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 dogs need to be closely supervised especially around traffic since they cannot hear dangers such as cars.
In-depth Information on Deafness (Hearing Loss) in Dogs
Animals that are deaf tend to sleep soundly and do not respond promptly to calls for them. Sometimes, they will continue sleeping until they are awakened with a touch. Unilaterally deaf animals may sleep through calls to them if they are lying on their good (hearing) ear.
Hearing is important for pets because they depend on auditory cues for commands as well as alerting to dangers in the environment. However, deaf animals can make great pets once the deafness is recognized.
Causes of deafness can be divided into either conduction disturbances or sensorineural disturbances. Conduction deafness is caused by abnormalities of the pinna (external ear), ear canal, tympanic membrane (eardrum), auditory ossicles or middle ear. Sensorineural deafness is caused by abnormalities of the inner ear, auditory nerve, or in the brain itself. Some of the more common causes of deafness in cats are:
- Old age
- Congenital or inherited deafness
- Otitis externa, which is inflammation of the external ear
- Otitis media, or inflammation of the middle ear
- Otitis interna, or inflammation of the inner ear
- Loud noises such as gunfire
- Tumors in the ear or in the brain
- Diuretics such as ethacrynic acid, furosemide and bumetanide
- Ototoxic drugs, which are drugs that have a deleterious effect on the ear or the otic nerve, such as gentamycin, neomycin, streptomycin, amikacin, polymyxin B, minocycline, erythromycin and chloramphenicol
- Otic cleaning agents such as ethanol, iodine, chlorhexidine and benzalkonium that are infused into the middle ear through a perforated ear drum
- Other drugs such as salicylates, cetrimide and cisplatin that can cause temporary and permanent hearing loss
Deafness can be unilateral (affecting one ear) or bilateral (affecting both ears). Partial deafness is difficult to recognize but in some animals, partial hearing loss can be observed by some owners. Unilateral and partial deafness can be tested using a brainstem auditory evoked response (BAER) test. The BAER test requires specialized equipment that may only be available at veterinary referral centers. The BAER test is the only reliable and accurate way to assess deafness, particularly unilateral deafness. Animals as young as 5 weeks old can be tested for deafness using the BAER test. The BAER is absent in affected animals.
Dogs and cats born deaf usually inherit this problem from their parents. Inherited deafness is sensorineural deafness due to degeneration of the inner ear structures. You will typically notice the deafness at a young age. White, merle or piebald coats increase the chances that an animal has inherited deafness. Deafness has been linked to certain breed characteristics such as heterochromia iridis (incomplete iris pigmentation) although definite links have not been proven. A list of canine breeds with reported inherited deafness include:
- American pit bull terrier
- American Staffordshire terrier
- Australian heeler
- Australian shepherd
- Border collie
- Boston terrier
- Bull terrier
- Catahoula leopard dog
- Cocker spaniel
- Dappled dachshund
- Doberman pincher
- Dogo Argentino
- English bulldog
- English setter
- Fox terrier
- Great Dane
- Great Pyrenees
- Parson Russell terrier
- Miniature poodle
- Norwegian dunkerhound
- Old English sheepdog
- Rhodesian ridgeback
- Scottish terrier
- Sealyham terrier
- Shetland sheepdog
- Shropshire terrier
- Walker foxhound
- West Highland white terrier
In animals that have inherited deafness, all the breeding animals should be tested using the BAER test. If they are found to be deaf in one or both ears, they should be removed from the breeding programs. Inherited deafness cannot be treated with hearing aids or surgical treatment.
Diagnostic tests are performed to establish the diagnosis of deafness and help identify the cause. Some of the testing for bilateral and complete deafness can be done at home as frightened or uncooperative animals may be impossible to evaluate in the veterinary clinic. Your veterinarian can make recommendation for treatment and lifestyle modifications based on the findings of the examinations and tests.
Testing Your Dog For Deafness at Home
You can easily assess whether your dog is bilaterally and completely deaf. This testing method requires two people, the “observer” and the “noisemaker.” This method avoids some of the mistakes people can make in evaluating hearing. The first step is to wait until your pet is lying down either asleep or very quiet. The observer should be in the same room as your pet. The noisemaker should be in an adjoining room but out of sight from the pet. The noisemaker begins by making low decibel sounds such as clapping or whistling. The observer should watch for a reaction from the pet to the sound. Reactions are usually lifting of the head (alerting) and turning towards the sound. The noisemaker should increase the volume of the sound until a reaction is observed.
By testing this way, you avoid giving your pet visual cues and decrease the chance of misdiagnosing your pet’s deafness. The noisemaker should be aware that vibrations through air and surfaces can be felt by mechanoreceptors not associated with the ear. For example, an animal may alert to feeling a vibration from a slammed door rather than actually hearing the sound of the slamming door.
Testing for Deafness At the Veterinarian’s Office
Your veterinarian will take a complete medical history and perform a thorough general physical examination. Previous medications and any illness your pet has had should be brought to your veterinarian’s attention in the case of a youngster suspected of being deaf. It would be helpful to know the hearing status of the animal’s parents.
Other important information your veterinarian will need is the age at which you first noticed the deafness, what alerted you to the suspected deafness, and any signs associated with the problem such as head shaking, ear scratching or discharge from the ears.
Your veterinarian may repeat some of the hearing tests you have done. Remember, it can be difficult to assess frightened or uncooperative animals. After assessing for deafness in your dog, your veterinarian may perform the following tests:
- A thorough ear (otic) exam. The otic exam will consist of looking at the ear, ear canal and eardrum. This is done with an otoscope. It may be necessary to sedate or even anesthetize a painful animal in order to thoroughly evaluate the ear structures.
- Neurological assessment. Because it is important to determine if your pet’s deafness is related to other deficits in the brain or central nervous system, your veterinarian will want to perform a neurological exam.
- Radiographs of the skull may be indicated in the case of suspected ear infection or masses. Where available, a CT or MRI may be an alternative to skull radiographs. These test help assess the severity of the infection, as well as help establish the best treatment for the condition.
- Cultures of ear discharge may be taken to help determine the best antibiotic to use in cases of ear infections.
- If other neurologic deficits are detected with a neurologic examination, additional diagnostic tests such as cerebrospinal fluid (CSF) analysis, titers on blood and CSF, and computed tomography or magnetic resonance imaging of the head may need to be performed.
- Impedence audiometry and brainstem auditory-evoked response (BAER) testing may be recommended to determine the type (conduction versus sensorineural), degree (partial versus complete) and symmetry (unilateral versus bilateral) of the deafness. These tests require specialized equipment, which may require referral to neurologic specialty centers.
- Electrodiagnostic testing is generally available at specialty or university hospitals. Using electrodiagnostic testing, specialists can determine the type, degree, and symmetry of dysfunction. The equipment required is specialized and expensive (>$25,000). Depending on the equipment and the tests to be performed, the pet may need to be sedated or anesthetized. A brain stem auditory evoked response (BAER) test can determine if complete sensorineural deafness is present in either one ear or both. Potential breeding pairs and all puppies from dog breeds with a high incidence of deafness should be BAER tested.
Therapy In-depth for Canine Deafness
In the case of conduction deafness caused by ear infections and wax accumulation, treatment is aimed at removing the infection or blockage. Cleaning should be done only by well-trained people to prevent further hearing damage. In some cases of severe ear infections or presence of a large foreign body, your pet may need to be anesthetized by your veterinarian. Hearing can be restored as long as the damage is not too severe. Other treatments may include:
- Infections may be treated with topical medications placed in the ear canals and systemically with injectable or oral antibiotics. When a culture of the ear discharge is taken, your veterinarian may change the antibiotics you are giving your pet if the test indicates a more effective antibiotic.
- Sensorineural deafness is not treatable since it either involves the nerves or the organ of hearing. Future treatment for sensorineural deafness may include cochlear implants.
- Hearing aids that fit in the ear canal only amplify sound so partially deaf animals are helped by these devices. Complete hearing deficits such as seen with congenital sensorineural deafness are therefore not helped with these devices. Animals generally do not tolerate hearing aids; to test if your animals will accept a hearing aid in their ear canal, you can place a $2 foam earplug in your pet’s ear. If he can tolerate the presence of an earplug for several hours, he may be a candidate for a $1000 hearing aid.
Follow-up Care for Dogs with Hearing Loss
No matter what causes your pet’s deafness, special precautions are needed to accommodate deaf dogs. Deaf animals can be trained to obey hand signals. In general, it is easier to train animals that are born deaf than hearing pets that become suddenly deaf. There are resources on the web for teaching deaf dogs signals and most animal trainers are familiar with training hand signals.
Deaf animals cannot hear danger around them. For this reason, they must be protected and closely supervised around roads and traffic. Furthermore, animals that are unilaterally deaf will often have difficulty orienting to sound and may turn to the wrong direction, which is dangerous in some situations. If an animal is deaf, he should always be leashed to prevent tragedy.
In the case of a deaf animal wandering away from you, remember that he cannot hear you call. Placing a bell on his collar will help you locate him.