As we mentioned in our last post about deafness in our poochy pals, there is conduction deafness where the sound wave is impaired by some form of obstruction. There is also a type of deafness that happens when there is a sensor/nerve issue. This latter type of deafness is called Sensorineural deafness. Interestingly, it can be congenital or acquired throughout life.
Congenital sensorineural deafness means you are born with a problem that will cause deafness. What’s interesting is that studies have shown hearing is often present in affected dogs in the first few weeks of life but is gone by the age of about 60 days! This form of deafness affects the cochlear duct (the part in the inner ear where the fluid meets the hairs that are attached to the nerve endings).
There are two known forms of congenital sensorineural deafness:
Albinotic form – can occur in animals that are partially or completely albino, the deafness can be one side or both sides.
Abiotrophic form – means degeneration or loss of function of the hair cells deep inside the inner ear that are supposed to translate the message from fluid wave movement to nerve impulses. Usually both sides are affected. Although normally deaf by 8 wks of age, there is the rare occasion where this may occur later in life.
Acquired sensorineural deafness – occurs most commonly secondary to infections that cause inflammation of the middle ear and inner ear. Cancers can cause this problem but it is rarely seen. Meningitis can also be a component. Some drugs can cause problems if they get direct access to the middle ear via a ruptured ear drum, even some ear cleaners cause this if the ear drum is ruptured. There are also some chemotherapy drugs that may cause deafness. We can also see age related degeneration of the hair cells deep within the ear that will cause deafness.
Currently our diagnostic ability with regards to deafness is limited in New Zealand. If you feel your dog is going deaf, take them to your vet to have their ears checked. Remember that because dogs have two ears, you won’t notice deafness until it is affecting both sides and usually not until it’s advanced. Your dog may not be being naughty, maybe they can't hear you .... of course you may have one of those dogs with selective hearing - you know the one's that can't hear their name but they do hear the food container opening! ... that sort of 'hearing loss' you will have to work on at home or with a dog trainer ...;)