A closer look: Loss of Hearing (Deafness or Hearing Impairment) in Cats
The inner ear is a complex organ responsible for translating sound waves into nerve impulses which are sent to the brain and interpreted as the sensation of hearing.
Hearing loss or deafness is usually related to
- Reduced or interrupted conduction of sound waves from the environment through the inner ear apparatus
- Nerve damage preventing sound waves from being translated from the ear to the brain
- A combination of both
Cats with suspected deafness benefit from veterinary attention.
Deafness varies in severity which makes diagnosis challenging as cats with deafness in one ear may appear normal.
Cats with hereditary deafness suffer complete hearing loss in the affected ear but may have normal hearing in the other ear.
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Deafness in cats can be thought of as either a hereditary or acquired condition.
Hereditary deafness: This is a genetic condition seen in white cats. The gene controlling a white haircoat is also expressed in the hair on the cochlea (a sensory organ in the inner part of the ear which converts sound waves into neurological signals that the brain can interpret as a noise). Cats with this gene experience degeneration of the hairs of the cochlea in one or both ears resulting in complete unilateral or bilateral deafness. Not all white cats with blue eyes are deaf.
Acquired deafness includes failure of conduction of sound waves into the inner ear as well as degeneration of the sensory organs in the ear.
Deafness is an uncommon condition but is more common in:
- White cats
- White cats with blue eyes
Not all white cats with blue eyes are deaf.
Deafness does not affect life expectancy and most cats live a normal life but are often kept as indoor cats due to the dangers of deafness such as:
- Car accidents
- Attack from predators
- Fighting with other cats
Cats with acquired failure of conduction are often deaf in one ear and the degree of severity varies. Cats with a nasopharyngeal polyp in one ear may be partially deaf in one ear but have normal hearing in the other ear whereas cats with bilateral chronic ear infections may have partially reduced hearing in both ears.
Testing and diagnosis
Investigation of hearing loss involves:
- Physical examination
- Blood work
- Microscopic examination and bacterial culture of ear contents
- Brainstem Auditory Evoked Response (BAER) test
- Diagnostic imaging such as head X-rays and CT scan
Treatment of acquired deafness involves:
- Topical or systemic medication of ear infections or inflammation
- Surgical removal of tumors and nasopharyngeal polyps
Resolution of hereditary deafness is not possible and treatment involves managing a safe environment for a deaf cat.
Management of cats with irreversible deafness include:
- Keeping indoors to remove risk of car accidents
- Use hand signals, or visible cues to communicate
Deafness is difficult to recognise if deafness is only in one ear, or if it is mild and progressive. Stubbornness is sometimes mistaken for deafness in cats
Deaf cats may have no other symptoms, but signs sometimes associated with deafness include:
- Not waking unless touched
- Overly aggressive play as audio cues are not heard, particularly in kittens
- Progressive ignoring of communication in older cats
- Overly loud yowling/meowing
- Absence of the Preyer’s reflex, where the ears move towards the source of a sound made outside the field of vision