By John Gilpatrick
Hearing loss in dogs can happen gradually and doesn’t manifest itself with other physical symptoms. Dr. Kathryn Winger, an assistant professor of veterinary neurology at the Michigan State University College of Veterinary Medicine, says the most common signs of hearing loss include a lack of response to being called; no reaction to loud noises like the doorbell or other animals or people; being easily startled or harder to arouse; not interacting normally with littermates (for puppies); and being extra rambunctious or vocal. However, this doesn’t account for unilateral deafness, or hearing loss only affecting one ear, which Winger says often goes unnoticed.
If your suspect your dog is deaf or experiencing hearing loss, approach him slowly during rest or sleep to avoid scaring him. Deaf dogs should always wear identification tags, and, for similar reasons, microchipping is very important, Winger says. “They should always be kept on a leash or in a fenced yard, as they may not sense threats, and they will have limited recall. You also need to train them using visual cues, rather than verbal ones,” she adds.
But to best care for a deaf dog, it’s helpful to understand the causes of hearing loss. Some of them are treatable, while others are sadly irreversible.
Congenital hearing loss is related to degenerative changes within the hearing part of the inner ear, also known as the cochlea, explains Dr. Rod Rosychuk, professor and head of dermatology and otology services at Colorado State University. “In the cochlea, sound waves are converted into nerve impulses that are subsequently transmitted to the brain and sensed as ‘sounds,’” Rosychuk says.
Congenital hearing loss is permanent and often hereditary. It’s most commonly associated with certain coat colors—specifically white or merle (a sort of multi-colored splotchy or swirling coat), Winger says. The abnormality is present at birth, she says, but it usually makes itself known between 4 and 6 weeks of age.
Presbycusis is the most common form of acquired hearing loss in dogs, Rosychuk says. Like congenital hearing loss, it affects the receptors in the cochlea and their ability to transmit sound to the brain, but it’s specific to older dogs and generally comes from the degenerative effects of a lifetime of accumulated noise. Like congenital hearing loss, presbycusis is irreversible.
Moving outward from the inner ear, middle ear infections often arise due to a hole in the ear drum, Rosychuk says. This may happen because of a foreign body or waxy buildup in the ear canal.
Unlike congenital hearing loss or presbycusis, Winger says deafness that may result from an ear infection like this is reversible through treatment. “If they suspect an ear infection, owners should consult with their veterinarian for an otoscopic examination,” she says. “Deep-seated infection in the middle ear may only be detectable with advanced imaging such as a CT scan. If infection or debris is found, oral and/or topical therapy may be needed.”
If ear infections recur regularly, it may be a sign of an allergy in your dog’s environment. A full workup should be done to identify the allergen, Winger says.
“Deafness in dogs can also be associated with drugs that have a deleterious effect on the cochlea,” Rosychuk says. “This effect is referred to as ototoxicity.”
It occurs with drugs that are used to treat infections or inflammation in the ear. If there is a hole in the eardrum (which Rosychuk says is rare) and the drug reaches the inner ear through this hole, the dog may experience deafness. “Drugs that are more frequently incriminated include neomycin, propylene glycol, and tobramycin, but many other drugs have been incriminated,” he says.
After the drug has worn off, the dog may return to normal hearing, but ototoxicity can also lead to permanent deafness. This is one reason why it’s critically important not to put anything in your dog’s ears without a thorough examination.
While rare, Rosychuk says blunt trauma to the head, whether there are fractures present or not, may result in blood getting into the dog’s inner ear, which can lead to deafness. The trauma may also lead to direct damage to the inner ear. This deafness may be either temporary or permanent.
If you own a dog, you know pretty much anything is possible. One fairly common, and thankfully temporary, cause of deafness is the presence of a foreign object in the ear canal. Winger calls this conductive deafness. It doesn’t affect the transmitters, but rather it simply blocks the transmitters from the environment in which sounds are generated.
Some foreign objects may lead to perforation of the eardrum, which can open your dog up to an infection. Even if you’re able to remove the object yourself, you should consider a checkup with the vet to make sure there’s no further damage.