white boxers - they're born with hearing, right?

[liamsmom]

i just read this posted by gmacleod here on boxerworld (so glad i found the EXACT info i've been looking for...in writing - gotta love BW! Deaf puppy?

"A dog that is deaf due to lack of pigment (ie. being white) is not born deaf. Hearing is progressively lost, due to lack of melanocytes leading to suppression of blood supply to the cochlea, over the 3-6 week period. Thus, if the pup is going to be deaf due to being white, it will be by about 6 weeks of age - certainly by the 8 week point at which it's ready to be rehomed."

when people find out about them being deaf and ask us if our two white Boxers were born deaf or "went" deaf after they were born.......i am correct in saying that they went deaf by 8 weeks, right? for some reason i never felt right about it but kind of know i'm right does that make sense??????
with some people it is definately easier for us to say that they were born deaf (to avoid getting onto a genetics conversation) but for other people that are genuinely interested....i usually like to explain a little bit more. and i'm just having a brain freeze...doubting myself. i hate when this happens.
can white boxers be born deaf?
or are they always born with 'hearing' that is gradually lost?

[Caney Creek]

Honestly, I thought they were born deaf, so I learned something!
After reading gmacleod's post, it sounds to me like deafness due to the white gene only occurs after birth. I don't know what other conditions might cause a dog to be born deaf, but if one IS born deaf, it's due to some cause other than being white. That's just what I gathered.

I found this website, very interesting info on the subject.
http://www.*****************/whites.htm

[Biff]

Mmmmmmm, I had thought they were born deaf too

[gmacleod]

No, they're not strictly born deaf (though since the ear canal doesn't open for 10 days or so after birth, and deafness may be starting by about 3 weeks, the period during which they can hear is rather brief!).

Here is an article that explains in more scientific terms what is going on there. In the case of boxers, the gene they carry and which is responsible for both white markings and deafness is the same one as in Dalmations (sw) - not the si gene of bullterriers et al. The relevant heading here is Congenital Hereditary Sensorineural Deafness: http://www.lsu.edu/deafness/VetClinNA.htm

From the linked article:

In breeds of dogs carrying the piebald or merle genes and breeds of cats carrying the white gene, the hair cell loss is secondary to degeneration of the cochlear blood supply. Figure 1 shows a cross section of one turn of the cochlea, demonstrating the separation of the cochlea into three parallel ducts: the scala vestibuli, the scala media (or cochlear duct), and the scala tympani which joins at the apex of the cochlea with the scala vestibuli. The outer margin of the scala media is covered by a vascular bed, the stria vascularis. The stria is responsible for secretion of endocochlear fluid and maintenance of its high K+ concentration which is essential to sound transduction by the sensory hair cells. In pigment-associated hereditary deafness, this vascular bed degenerates, resulting in secondary loss of hair cells and deafness. The cause for the strial degeneration is unknown, but histologic studies have demonstrated an absence of strial melanocytes, whose presence or postnatal development is suppressed by the piebald or merle genes. The function of melanocytes in the stria is unknown, but they appear to be critical to maintenance of elevated K+ levels in the scala media and survival of the stria. Whether hair cell death is from primary or secondary mechanisms, the loss is permanent, as mammals are unable to regenerate cochlear neuronal tissue.

In the Dalmatian, postnatal auditory function development has been shown to proceed normally up until 3 weeks of age, at which point the strial degeneration produces rapid loss of hair cell function.6 A similar time course is likely in other breeds of dogs and cats with pigment-associated deafness, but it has not been studied. Likewise, the time course of congenital deafness in canine breeds not associated with white pigmentation has not been documented, but it is likely that deafness is present at birth or shortly thereafter. As a consequence of the documented 3 to 4 weeks of age at which time deafness appears, hearing testing, as described below, is typically not performed until an animal reaches at least 5 weeks of age.