Congenital deafness can be inherited or obtained. It is either cochleosaccular or neuroepithelial. Cochleosaccular congenital deafness is the most common, as it refers to dogs that a deaf genetically due to having the white, merle, or piebald gene.
Dogs with any light-colored or white pigmentation of the skin or coat can be predisposed to deafness. The condition usually develops 1 to 3 weeks after birth when the stria vascularis in a dog's inner ear begins to deteriorate. This deterioration is caused by the dog's pigment gene suppressing melanocytes, a skin cell that contains the melanin pigment.
Neuroepithelial deafness usually affects both ears and is less common than cochleosaccular deafness. Neuroepithelial deafness doesn't relate to pigmentation and instead is caused by hair cell loss that isn't related to the stria vascularis. Neuroepithelial deafness develops over a similar time period to cochleosaccular deafness.
It's also possible for dogs to acquire congenital deafness. This form of congenital deafness is usually due to exposure to drug toxicity in utero. Many drugs can cause damage to the ear, including diuretics like furosemide and aminoglycoside antibiotics like gentamicin. Other conditions which can cause congenital deafness to puppies in utero include uterus infections, meningitis, and liver damage.