Testing and Management of Deafness in Dogs
Summary:
"Deafness in dogs can be due to an inherited condition or a disease
such as an untreated infection. Hearing loss can also be
brought on by noise, medications or is age-related (ARHL or presbycusis).
Signs of deafness include being unresponsive to sounds such as a toy
that makes noise, or if a dog doesn't awaken after a loud noise. Dogs
with hearing loss in one ear can have trouble in localizing a sound
source. Some causes of deafness result in a permanent hearing loss
while others could be temporary. It is often difficult for an owner to
detect the slow progression of deafness in dogs since a pet will try
and compensate for the hearing loss.
Diagnosis includes a physical examination and
neurological examination. Advanced imaging tests (MRI or CT scan) are
needed for a full evaluation of the inner and middle ear. Other methods
such as a test of the nerve impulses generated by the cochlea is
conducted using a
BAER test. Treatment starts with the elimination of any disease or
debris. Genetic disorders cannot be treated. Use of dog hearing
aids and advanced methods such as cochlear implants are not commonly
recommended or used. Puppy deafness requires special training.
Hearing loss can affect the relationship between the owner and dog
since a dog cannot respond to sounds. If your dog is deaf this
can be overcome with counseling and special training. Being deaf is not linked to other
health congenital health problems or concerns. Deaf dogs are also
not more aggressive."
Dog BERA Test for Hearing Loss
A BERA test is used to test
hearing loss in dogs. The patient
receives light anesthesia. Electrodes are used to detect sounds such as
clicks.
Overview
Deafness in dogs is either an inherited condition or is a result of
disease such as an untreated chronic ear infection (otitis externa).
Deafness is characterized as being permanent or temporary, partial
or complete. Dogs can be born deaf, a condition that cannot be
corrected (congenital deafness). There are several breeds that have
this genetic condition such as Dalmatians, which is why responsible
breeding is critical. Sudden hearing loss in dogs is rare, with
most cases developing over time as a condition develops. Correction of
the problem, such as the removal of excessive wax often restores
hearing, assuming the issue did not breach the eardrum.
Deafness in puppies is detected in dogs that learn slowly and that do
not respond to an owner's voice of commands. In an older dog,
signs include a lack of response to verbal cues and a dog that does not
respond or wake up when an owner returns from work.
Home tests for deafness include seeing if a dog responds to a rattling
of your keys or a toy that squeaks. Try clapping your hands behind the
dog or whistling to see if it evokes a response.
Predisposing and Perpetuating Factors
Certain breeds are predisposed to
developing deafness. This includes dogs withe white in their coats and
Dalmatians (30% incidence of deafness). The Cavalier King Charles
Spaniel has what is called progressive hereditary deafness, with the
first signs at age 3 to 4 years of age. Other dogs show signs of
deafness as a puppy.
Cocker Spaniels are prone to excessive ear wax production which can
cause some hearing loss or create an environment for infection.
Breeds with an above average incidence of deafness at birth (dogs
with white in their coats):
- Collies
- Shetland Sheepdogs
- Dappled Dachshunds
- Harlequin Great Danes
- American Foxhounds
- Old English Sheepdogs
- Norwegian dunkerhounds
- Bull Terriers
- Samoyeds
- Greyhounds
- Great Pyrenees
- Sealyham Terriers
- Beagles
- Bulldogs
- Dalmatians
- English Setters
- Australian Shepherds
- Welsh Corgis
Common Causes
Infection is an external ear canal disease (otitis externa) that can
cause deafness in dogs. When it is not treated, the infection can
progress to the middle and inner ear. When a dog's ears fill with wax,
mite debris and pus, sound waves are blocked from reaching the eardrum.
This blockage can be partial or complete, causing varying degrees of
hearing loss. Factors that lead to frequent dog ear infections include
moisture from swimming, living in a humid environment or excessive wax
production.
Ear Infections
Dog ear infections that are left untreated can breach the eardrum,
resulting in impaired or permanent hearing loss. This type of hearing
loss is called acquired conductive hearing loss.
Any deafness caused by disease tends to develop over time.
Ototoxicity
Ototoxicity is a term that describes dog ear poisoning, which is a
result from being exposed to chemicals or drugs that damage the nerve
that communicates hearing and balance information to the brain from the
inner ear, or that damages the inner ear. Hearing loss occurs
when toxins are ingested or enter into the inner ear via a perforated
eardrum. Some conditions are reversible while others are not. The key is to
detect and treat the problem as early as possible.
Causes of ototoxicity include:
- antibiotics (certain medications)
- ear cleaners
- household chemicals
- chemotherapy drugs
NIHL
Hearing loss can also be noise-induced (NIHL).
Age Related Hearing loss
Age related hearing loss in dogs is common (also called ARHL or
presbycusis). It is also the most common form in people. With age
there is some degeneration in the inner ear. This can occur with or
without signs of infection. Researchers believe that is it caused
by the life-long effects of noise, ototoxic agents (medications,
chemicals), heredity and disease.
In dogs researchers have seen age related hearing loss start between 8
to 10 years of age in the middle to high frequencies. The mean age was
12 years.
Audiogram of Dog Hearing Loss At Different Ages
Audiogram of hearing in dogs at
varying ages. The mean age of solid
lines (1.9 years mean age), dashed lines (5.7 years) and dotted lines
(12.7 years) show the response at various sound frequencies. The
"x" represents that left ear and "o" right ear.
Source:
Gert ter Haar Veterinary Sciences
Tomorrow
Symptoms
Look for signs and symptoms of hearing loss or
dog ear
illnesses. These include:
- head shaking
- ear scratching
- ear odor
- exaggerated barking
- sleeping through sounds, no response to sound
- being startled when touched
- not responding to an owner's voice or when called
- no response when returning home from work
- confusion to commands that were previously understood
- reduced levels of activity
- difficulty waking the dog
- excessive barking
- disorientation, confusion
- agitation in familiar places
Diagnosis
Diagnosis of deafness in dogs is relatively easy. First the
veterinarian will conduct a physical examination while looking for
signs of external or middle ear disease. Brain related problems can be
detected with tests such as a MRI, CT scan or a BAER test (brain stem
auditory evoked response).
How Dog BAER Tests Work
The BAER test evaluates how the brain stem reacts to an auditory
stimulus. A neurologist conducts that test using a 10-minute procedure.
First headphones or ear plugs are placed on the dog. Tones or clicks
are then played through the headphones. Electrodes inserted under the
skin measure electrical response in the brain to the sounds.
Treatment
If hearing loss is genetic, there is no treatment available. When
the
hearing loss is acquired, which means it is the result of disease,
medications can be used to treat the canine ear problem. If the disease
progresses to the point where the eardrum becomes ruptured, the hearing
loss will be permanent and complete.
No matter the degree of hearing loss, from partial to complete, dogs
are good at adapting. Dogs that are deaf tend to pay added
attention to their surroundings, making them easy to train. They will
rely on other senses and live a happy life.
Dog Hearing Aid
Dog hearing aid training is required to help a dog adapt to
amplification and the importance of the sounds. This dog, once trained,
would seek out the hearing aids each day (would wear them for 10 hours
or more each day)
Photo Credit:
FetchLab
Dog Hearing Aids
There is a dog hearing aid option for some dogs. They are not commonly
used, but are actively being researched. Hearing aids for dogs are
expensive and many dogs do not tolerate the devices. Using
amplification
of sound, which is what a hearing aid accomplishes hasn't achieved high
levels of clinical success and there are no reports available on their
effectiveness.
If hearing aids are being considered, a dog will be examined to see
if he or she is a good candidate. Dogs need to pass a minimum
threshold for hearing in order to effectively use the devices.
This level can be determine with the BAER response test described above.
In the laboratory dogs with hearing aids had to be trained to recognize
sounds as being meaningful.
Dog Cochlear Implants and Prostheses
Like hearing aids, there are dog cochlear implants and prostheses. The
devices address shortcomings of traditional hearing aids by providing
acoustic amplification and transmission of sound energy along with a
vibratory element called a transducer directly to the middle ear.
Middle Ear Implant
The Vibrant Soundbridge (VSB) middle ear implant is the only middle ear
implantable hearing device available in the United States. While
studies in humans have shown some success, there are not studies on the
use of the device in dogs. However, it has been shown that the
device can be successfully implanted in dogs.
Dog VSB Implant
VSB implant using an External
Audio
Processor. The Device Is Held in
Position Using an Implanted Magnet
Photo Credit:
Veterinary Sciences Tomorrow
The cost is high, $20,000 to $25,000 (U.S. Dollars) plus the cost of
surgery and post-surgery training. Cochlear implants in dogs are not
consider to be a practical option.
Taking Care of a Deaf Dog
Dogs can use other senses to compensate for any hearing loss and can
lead a good quality of life. That said, steps need to be taken to
improve the safety of a deaf dog. These include:
- Training a deaf dog on how to recognize hand gestures or other
visual types of communication. Like all training consistency is
critical such as touching a dog in a specific place in order to
indicate a desired behavior. Use food rewards or a vibration
collar to reinforce commands. Food should be paired with the
vibration so that the vibration becomes a positive experience.
- Attach a bell to the dog's collar to make it easier for a pet
parent (you) to find your dog
- Try and avoid startling a deaf dog. Alert your dog to your
presence by creating vibrations through stomping of the fee or clapping
the hands. Best to approach from the front and not the rear.
- Keep your dog indoors to protect them from threats that are
usually detected via sound such as a car.
- Protect your dog when walking in the park. Your pet cannot hear
other dogs or understand potential threats. They can also have
trouble understanding the actions of small children and should be
watched carefully since they can be a biting risk. Children are
difficult for dogs to interpret without the help of sound.
- Physical fencing can protect a dog outdoors.
Dog Sign Language
Some trainers have developed a dog sign language to help train a deaf
dog. Signs include:
- Sit Command: Use a flat hand with the palm up. For training
hold a treat between the index finger and thumb, holding other 3
fingers
out. Move your hand slowly from the front of the face to over the head
and back. The dog will follow the treat, with many dogs automatically
assuming a sitting position. Provide a treat immediately at that point.
- Down Command: Hold the hand flat and your palm down. Also place
the treat between the index finger and thumb. Move your hand from
the front of the nose to angle with the floor. Start by touching the
floor, with the nose following the treat. Use your other hand to gently
press on the back end of the dog. Repeat again and back your and away.
Create your own signs for meal times, walks, going to the bathroom etc.
Deaf dogs will learn from facial expressions and other cues.
For more suggestions see the ebook below on training a deaf dog.
Prevention
Keeping dog ears free from debris, mites and infection is the first
step in preventing ear disease in dogs. Start by examining the ears
regularly, and look for signs such as inflammation, discharge and
swelling. Look for symptoms such as constant ear scratching. A
dog might also benefit from additional support with a product like Ear
Dr. that is formulated to naturally support ear health.
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Brochures and References:
Brochures on deafness in dogs (free!):
For additional reading on Deafness
in Dogs:
Books:
Websites on deafness in dogs:
Deaf Dogs
Owner Group
on Yahoo
Reference Materials on deafness in dogs:
Brain stem Evoked Response Audiometry for Hearing Assessment in Dogs
Gert Ter Haar, DVM, DECVS
Department of Clinical Sciences
of Companion Animals
Faculty of Veterinary Medicine
PO Box 80 154
3508 TD Utrecht
The Netherlands
Strain GM. Aetiology, prevalence and diagnosis of deafness
in dogs and cats. Br Vet J 1996;152:17-36.
Treatment of Hearing Losses
G. Ter Haar
The Queen Mother Hospital for Animals
Royal Veterinary College
North Mymms, Hatfield, Hertfordshire, UK
