Deafness

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Deafness is very difficult to detect, apart from noting your dog’s behaviour and lack of response to noise. Sound is transmitted through the air in waves. These are directed by the ear flaps and pass through the air-filled ear canals where they strike the ear-drum causing it to vibrate. These vibrations are then transmitted by three small bones in the middle ear to a second membrane. Eventually the vibrations are converted to electrical impulses that are transmitted to the brain where they are interpreted as sounds.

Damage anywhere along this pathway may result in hearing loss. The outer ear canal can become filled with wax and debris. This can be visualised using a special instrument.

The middle ear is also part of the nervous system responsible for balance. Tumours of the brain may affect other functions as well as cause deafness.

What your veterinarian will want to know

Your veterinarian will want to know if the problem has occurred suddenly or has come on gradually. Is the dog shaking his head, or does the ear seem painful? Is there any problem with balance or coordination? Are there any other behavioural changes?

What your veterinarian may do

If the dog is shaking its head and is in pain your veterinarian may be suspicious of disease of the outer ear canal. This can be visualised and debris cleaned to allow examination of the ear drum. This may be painful to do and so may require an anaesthetic or sedation. This will also allow the removal of foreign bodies and sampling of material from the canal to identify the cause of any infection.

If the external canal is clear and the ear-drum intact, then the problem must be due to some damage along the rest of the pathway. Middle ear disease is often also associated with problems with balance. Your veterinarian may suggest an X-Ray as this may help to identify infection within the middle ear. Radical surgical drainage may be recommended.
 
A full clinical examination will check the eyes and other reflexes to provide an assessment of brain function. Because the brain is within a bony case, it requires an MRI to adequately check its structure. This equipment is rarely available in standard veterinary practices and so may require a referral.