It is estimated that about 20-25% of the white Boxer population is
either unilaterally or bilaterally deaf. White puppies that are going to be deaf will be by around 3-4 wks of age. Up
until this age, the puppies can hear. If a white puppy is hearing by the time it's ready to leave its dam and littermates,
it is not going to become deaf later in life due to color.
The cochlear (receptor organ of hearing) develops normally
up until around 3 wks of age. Around this time the hair cells of the cochlea die due to degeneration of the vascular supply
to the cochlea. This degeneration tends to be a result of the lack of pigment cells in the inner ear.
Hair cells are the sensory receptors of the inner ear that convert
sound information into electrical signals. The electrical signals are then sent on to higher brain centers. Without these
hair cells, hearing is not possible. (Research in inner ear hair cell regeneration is being done although the research seems to be focused on hair cell damage and death due to noise trauma, aging,
and exposure to certain therapeutic drugs.)
It can be difficult to determine if a white puppy is indeed
bilaterally deaf if the one trying to make this decision is not careful. Deaf puppies will follow their littermates,
can feel vibrations from loud noises and can of course see movement. A unilaterally deaf puppy can be
near impossible to detect without the help of BAER testing.
The hearing test known as the brainstem auditory evoked
response (BAER) is the most accurate way to determine if a puppy is unilaterally or bilaterally deaf. This test
detects electrical activity in the cochlea and auditory pathways in the brain. Tiny electrodes are placed under the skin of
the scalp; the electrodes are connected to a computer which collects the response of clicks produced by the computer. The
clicks are directed into the ear with an earphone with each ear being tested individually. Testing is
normally complete in 10-15 mins.
