Cavalier King Charles Spaniels may be predisposed to a form of congenital deafness, which is present at birth, due to a lack of formation or early degeneration of receptors in the inner ear, although this is relatively rare. In addition, more recent studies have found Cavaliers that develop a progressive hearing loss, which usually begins during puppy-hood and progresses until the dog is completely deaf, usually between the ages of three and five years. The progressive nature of this form of deafness in Cavaliers is believed to be caused by degeneration of the hearing nerve rather than the lack of formation or early degeneration of the inner ear receptors.
