Deafness can be present at birth (congenital) or develop later from infection, injury, or changes to the cochlea.
Congenital deafness can be inherited or caused by damage before birth from a poisonous substance or a virus. Some dogs with grayish-blue and white coat patterns are deaf. Breeds commonly affected include the Dalmatian, Bull Terrier, Australian Heeler, Catahoula, English Cocker Spaniel, Parson Russell Terrier, and Boston Terrier, but the list changes over time.
Acquired deafness develops later and can result from blockage of the external ear canal due to chronic inflammation (called otitis externa) or a buildup of earwax. It can also occur with a ruptured (torn or punctured) eardrum or inflammation of the middle or inner ear. Hearing often returns after these problems are resolved.
Permanent acquired deafness most often arises from age-related changes to the cochlea. Other causes include inner ear trauma, very loud noises, diseases, drugs (like certain antibiotics), anesthesia, and tumors.
To diagnose deafness, vets closely watch how the dog responds to sounds. Young animals, or those in a group, can copy others, making deafness hard to detect. It's easier to notice deafness in dogs once they're about 3–4 weeks old, especially if they can be seen alone, away from other dogs.
The main sign of deafness is failure to respond to sounds (for example, failure to awake or alert to a noise). Other signs include unusual behavior, like increased barking, voice changes, hyperactivity, confusion with voice commands, and lack of ear movement. Gradual hearing loss in older dogs sometimes leads to not responding or refusing to come when called.
Hearing loss can be partial or total and affect one or both ears. Partial deafness or deafness affecting only one ear is hard to detect, often requiring careful observation or electronic tests.
A vet may perform an otoscope exam, x-rays, CT scan, MRI testing, and other exams to reveal causes of deafness, especially acquired deafness. In dog breeds more likely to have congenital deafness, electronic testing helps assess puppies' hearing.
Deafness from ear canal blockage often improves with medical or surgical treatment. Bacterial infections of the middle and inner ear may respond to antibiotics. Deafness from exposure to severe noise, trauma, or certain drugs is unlikely to improve.
Dogs with congenital deafness should generally not be used in breeding programs.
Deaf dogs don't feel pain from being deaf, but they do need more care and attention. Deaf dogs are more easily startled, which can increase the risk of biting, and they are less protected from dangers like vehicles.
