Deafness in Pets
We all know that our bodies start to lose some biological functions we take for granted in our earlier years with growing age. One example of this is the ability to hear. In humans, hearing loss is often associated with environmental exposure to loud sounds. Like us, pets can also suffer from hearing loss. There are many possible causes for hearing loss in dogs and cats, ranging from genetic conditions and infections to nerve damage and even cancer. In the following article, we will discuss some of the causes of hearing loss in pets.
Causes of Deafness in Dogs and Cats
By about two weeks of age, the ear canals of puppies and kittens begin to open, and they can start to hear for the first time. By about eight weeks of age, the hearing mechanism matures. When a genetic abnormality results in incomplete development of these structures, deafness can result. Congenital deafness has been linked to certain breeds and coat colors of dogs and cats:
1) Dominant Merle or Dapple Genes of the Collie, Dachshund, Great Dane, and Shetland Sheepdog. It is important to note that Merle or Dapple does not refer to a specific color but rather a coat pattern described as mottled or patchy. Blue or odd-colored eyes are also a feature of Merle of Dapple Colored dogs.
(Radlinksy MC, Mason DE: Diseases of the Ear. Ettinger SJ, Feldman EC (eds): Textbook of Veterinary Internal Medicine, 6th ed. St. Louis, Elsevier Saunders 2005 pp. 1184-1185)
2) Jack Russell Terriers with a white coating
Famula TR Cargill EJ Strain GM: Heritability and complex segregation analysis of deafness in Jack Russell Terriers. BMC Vet Res 2007 Vol 3 (1) pp. 31.)
3) Dogs of any breed can be affected by deafness. For a complete list, follow this link to the Louisiana State Veterinary School’s website: https://www.lsu.edu/deafness/breeds.htm
4) Cats – An increased risk of deafness is associated with white-coated cats and even more commonly in white-coated cats with blue irises.
There are many reasons why our pets may become deaf over time. Some of these causes include severe Ear Infections, which affect the middle or inner ear, substances toxic to the ear canal, traumatic injury to the ear, and cancer. In some cases, a benign (not cancerous) growth or polyp inside of an ear may cause temporary hearing loss, although hearing may return once the tumor is removed. Also, foreign bodies inside the ear canal may cause temporary or permanent deafness.
As a pet owner, there are several physical symptoms that your pet may display if they are suffering from hearing loss. These include:
• Unresponsiveness to name/ everyday sounds
• Unresponsiveness to squeaky toys
• Being a loud sleeper
• Meowing or barking loudly
• Not hearing your footsteps when you come in close
• Puppies or kittens playing more aggressively (because they cannot hear their littermates cry if in pain)
• Being formerly afraid of thunderstorms, but no longer is so, as a dog or cat gets older
Hearing loss itself is often not a life-threatening condition. However, it can result in life-threatening scenarios, which is why it is important to bring him or her in for a physical examination. When you first come in for an appointment, one of our Veterinarians will ask for a brief history of when you started to notice the onset of symptoms followed by any possible causes you may have noted at home. Our veterinarians will then perform a complete physical examination, look inside your pet’s ears with an otoscope, and if an infection is suspected, get a sample from your pet’s ears for evaluation under a microscope. If an advanced infection is suspected, a culture and sensitivity may be recommended to find the correct antibiotics needed.
Congenital deafness, unfortunately, is irreversible however, if our vet diagnosis the hearing damage due to an active ear infection or a growth in the ear, medications or surgical procedures can help resolve the deafness.
Hearing Loss in Dogs and Cats
Fortunately, dogs and cats with hearing loss can still live wonderful, happy lives, albeit with a few restrictions. Dogs with hearing loss may be more reactive to other dogs or stimuli since they may not hear them approach without warning if they come from the side.
Hearing Loss - pets
Drug toxicity ( ototoxicity ) results from administration or application of a drug or chemical which either directly or indirectly destroys cochlear hair cells, resulting in hearing loss or even total deafness. Many of the same agents are vestibulotoxic, disrupting the sense of balance so that the animal has a head tilt and may walk in circles. The most common cause of ototoxicity is the group of drugs known as the aminoglycoside antibiotics, which includes gentamicin, kanamycin, neomycin, tobramycin, and others. At times these drugs are the only treatment for a life-threatening infection, but they must be used with caution. Also, no-longer-available ear cleaning solutions containing chlorhexidine and a variety of less common chemicals can cause deafness (see G.M. Strain: "Aetiology, prevalence and diagnosis of deafness in dogs and cats." British Veterinary Journal 152:17-36, 1996). Concurrent conditions, such as an on-going infection or topical steroids, may increase penetration of a topical agent into the inner ear, increasing its toxicity. Recovery after hearing loss does not occur.
General anesthesia may cause bilateral deafness from unknown causes. In rare cases, animals awaken from anesthesia deaf in both ears, often following ear cleaning or teeth cleaning. It may be the case that the body shunts blood away from the cochlea during anesthesia to protect other critical organs, or that pressure or jaw positioning compresses the arterial supply to the cochlea. A similar outcome is noted in humans with ischemia of the vertebrobasilar artery. The inner ear is especially vulnerable to reduced blood flow because it has no collateral circulation and the tissues have very high energy metabolism. None of the cases I have seen or had reported to me have recovered hearing except for two cases that may have been conductive deafness. This reinforces the need for a good otic examination to rule out ear canal obstruction or middle ear infections. It is not known if unrecognized cases of unilateral deafness result from anesthesia, since this condition is usually not recognized by owners.
Noise trauma , depending on the loudness, can produce temporary or permanent hearing loss. Tiny muscles in the middle ear reflexly contract to reduce sound transmission into the inner ear in response to loud sounds (and prior to vocalization), which helps in sustained or continuous noise. However, percussive noise, such as occurs with gun fire and explosions, occurs too rapidly for the reflex to provide protection. Shoulder-supported rifles and shotguns used for hunting and target shooting produce a peak sound pressure level in excess of 140 dB, and fireworks and other explosives can be even louder. The noise actually disrupts the hair cells and their support cells. Since noise-induced trama has limited recovery, repeated exposure produces cumulative hearing loss, a serious problem for hunting dogs where the gun is fired over the dog's head. If there is a ringing sensation in the owners's ears after loud noise (gun fire, loud music, etc), damage is occurring in both the owner's ears and his/her pet's ears. Click here to go to a site at the web page of the National Institute on Deafness and Other Communication Disorders of the NIH on noise-induced hearing loss, and here for the National Institute for Occupational Safety and Health Noise and Hearing Loss Prevention web page.
Otitis . Infections of the middle ear (otitis media) or inner ear (otitis interna) can produce transient or permanent deafness. Otitis media may leave behind "crud" after the infection ends that blocks sound transmission to the inner ear (conduction deafness). It may take several weeks, but the body will eventually clear this out and the hearing will gradually improve in parallel. Otitis interna, if not quickly treated, will produce permanent nerve deafness.
The animal's hearing may in fact have been diminishing over time, but the owner may have been unaware because the animal compensated until it reached a point where it could no longer hear adequately to get by. To the owner the onset appears sudden, but it has been progressive. This is common in older animals with presbycusis (age-related hearing loss), which is progressive with time and cannot be prevented or reversed. Click here to go to a site at the web page of the National Institute on Deafness and Other Communication Disorders of the NIH on presbycusis.
One ear may have been deaf since birth (usually in animals with some white fur) but the owner was unaware because the only deficit of unilateral deafness is difficulty localizing a sound's source. Animals often quickly adapt to this deficit, so there is no overt behavioral manifestation. Any impairment of hearing in the opposite ear then is expressed as total deafness.
Sudden sensorineural hearing loss (SSHL) in humans can be caused by over 100 mechanisms, but the cause is seldom identified. Click here to go to a site at the web page of the National Institute on Deafness and Other Communication Disorders of the NIH on SSHL.
Dr. George M. Strain
Louisiana State University
Comparative Biomedical Sciences
School of Veterinary Medicine
Baton Rouge, Louisiana 70803
E-mail: [email protected]
June 7, 2006 Return to Deafness in Dogs & Cats
While sudden hearing loss is rare, there are a couple of exceptions. If your dog experiences some sort of head trauma, it could lead to damage to the bone surrounding the ear canal, which can then result in acute loss of hearing. Certain medicines can also have adverse effects on canine hearing – check with your vet if you have any questions about applying medicine in your dog’s ears.
You may be wondering how to tell if your dog is deaf at home, but if there is any question, you should head to your veterinary provider with your concerns. They will likely suggest a Brainstem Auditory Evoked Response (BAER) test for your pet. It detects electrical activity in the cochlea along with checking the auditory routes in the brain. The test involves placing electrodes on your dog’s head and then sending a slight stimulus through earpieces. It is the best way to determine the hearing capacity of your pet.
Deaf dogs can function normally, as long as owners take certain steps to keep them safe. You will have to train your dog to understand hand signals. They shouldn’t be left unleashed or placed in unfamiliar situations, since sudden touches or movements may startle them. With some adjustments, your dog can continue to live a happy life even with hearing difficulties.
If you’re beginning to notice that your four-legged friend isn’t responding to your calls or is slow to react to commands, connect with us. Knowing how to tell if a dog is deaf for certain is nearly impossible without taking a trip to your experienced veterinary provider.