By Dr. Laura Hady
Pets can hear about four times better than humans because they hear a much wider range of frequencies than we do. They use their hearing to help them hunt, stay safe and communicate emotions. So, healthy hearing plays a vital role in daily life.
However, hearing loss can affect 5%-10% of dogs and about 17%-20% of cats, with increasing frequency as they age. Factors that increase the likelihood of hearing loss include older age, genetics (white-coated and/or blue-eyed dogs and cats), chronic ear infections, trauma, foreign bodies, or toxins.
Ear infections with inflammation, bacteria and yeast are the most common contributors to hearing problems that I see in my patients. The sooner a vet can examine a dog or cat and get them on a regular treatment regimen, the better the outcome will be. The following is information about each of the more common hearing issues in pets:
1) Age-related hearing changes are mainly due to degeneration of the cochlea. The pet’s outer ear (pinna) is funnel-shaped, and animals have several muscles to help capture and direct sounds into the inner ear. These sound waves vibrate the eardrum and then are transmitted to three tiny bones that amplify the signal. The inner ear has tiny hairs in the snail-shaped cochlea. The vibrations move the fluid so that the hair cells can convert the mechanical motion into electrical signals. The electrical signals move down the auditory nerve, into the brain, where they are interpreted for the animal to have appropriate reactions to their environment. Your veterinarian can do an ear exam with an otoscope at your pet’s annual visit.
2) Genetics play a role in hearing, especially in white-coated pets with blue eyes because of the close location of the pigment and hearing genes on the chromosome. Absolute diagnosis can be obtained with Brainstem Auditory Evoked Response (BAER) testing with a veterinary neurologist. These patients don’t respond to loud noises or to their name and may startle with sudden movements when approached from behind or while sleeping. The good news is that you can train these pets with hand signals. My blue merle (patchwork coat) Australian shepherd with blue eyes was both deaf and mostly blind. We trained him with touch signals and smell cues.
3) Ear infections can be painful. If left untreated, they can cause rupture of the eardrum (tympanic membrane) and can settle into the inner ear, which is difficult to treat. Dogs tend to have more ear infections due to allergies, while cats can get ear mites. A veterinary staff may take a swab sample, roll it on a slide, stain it, and look at it under a microscope. The most common causes of ear infections are the bacteria Staphylococcus psuedointermedius along with an overgrowth of yeast. I usually have owners clean their pet’s ears three times a week with a solution that does not overly dry or irritate the ears. I will use saline on gauze for very irritated ears. Ear medications are often solutions that contain an anti-inflammatory (steroid), antibiotic, and an anti-fungal drug. Newer medications can be put in the ear once and last up to a month. In pets with allergies, I often try to treat the underlying cause with wipes, baths, oral steroids, and oral or injectable anti-itch medications. An ear canal ablation surgery may be required for dogs with severe, long-term, recurring ear infections. For cats with the extremely itchy ear mites, I thoroughly clean the ears and have the owner use a topical anti-tick and flea product. It is important to take your pet to follow-up appointments in case further medication or cleaning under sedation or anesthesia is necessary.
4) Trauma to the ear drum can be caused by a migrating foreign body such as a grass awn, seed or ear tick. Dogs with migrating grass awns may tilt their head to the affected side. Treatment requires sedation and removal of the object as well as treatment with oral medications if the ear drum is ruptured. It is not advised to use ear solutions in these pets until full healing occurs, which is about two weeks for most. Follow-up appointments are often necessary to monitor hearing and healing.
5) Toxins that cause hearing loss include drugs such as gentamicin, diuretics, chemotherapy drugs such as cisplatin, and more commonly chlorhexidine in ear cleaners. These substances can destroy the delicate sensory hair cells in the cochlea or affect the auditory nerve.
Ear issues in pets often require immediate attention to prevent long-term hearing loss. I often have owners check the ears of their dogs after a walk, especially in the late spring. I also recommend that owners clean their dog’s ears after a swim. Please do not probe the ear with a cotton swab or any metal plyer/hemostat. Be aware, too, that pets scratching their ears can spread mites and yeast to other parts of the skin. Finally, know that ear issues may take monthly exams and treatments to resolve completely.
