Deafness and the Cavalier King Charles Spaniel

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Deafness in Cavalier King Charles Spaniels

can be Congenital or Progressive

Cavalier King Charles Spaniels are predisposed to a form of congenital deafness, although it is not as common in Cavaliers as it is in a few other breeds. Congenital deafness is present at birth, due to a lack of formation or early degeneration of receptors in the inner ear.

In addition, more recent studies by Dr. Michael Podell have found Cavaliers which develop a progressive hearing loss, which usually begins during puppyhood and worsens, or 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 CKCSs is believed to be due to degeneration of the hearing nerve, rather than the lack of formation or early degeneration of the inner ear receptors. Dr. Podell is an ACVIM board certified veterinary neurologist and was an associate professor of neuroscience and veterinary medicine at the Ohio State University at the time of his studies.

Another ear disorder becoming more common in Cavaliers is Primary Secretory Otitis Media (PSOM), also called "glue ear", which is discussed on its own webpage.

Diagnosis

The conventional manner of testing a dog's hearing is the BAER (for Brainstem Auditory Evoked Response) test. The BAER test provides an objective assessment of auditory function in canines and other animals. The BAER test objectively examines a dog's hearing by bypassing the need to rely subjectively on the patient's response.

BAER measures the timing of electrical waves from the brain stem in response to a click, as a sound stimulus, in the ear. Within milliseconds of each click being made in a hearing dog's ear, a series of standard electrical waves appear on the BAER instrument's screen. The first wave comes from a nerve which transmits sound information to the brain. Then three or four other waves come from the areas of the brain stem which generate the hearing signal to the front of the brain and then to the cerebrum where the signal is interpreted as a sound. If the dog cannot hear the clicks, the waves will not appear on the screen.

However, conventional BAER testing usually does not adequately identify Cavaliers with progressive hearing deficiencies, because most BAER sites test only from a sound intensity threshold of 70 to 90 decibels, which is about the level of the sound of a vacuum cleaner next to the ear. The human voice normally is at the 40 dB intensity level, so even a Cavalier which passes the conventional BAER test could be deaf to human voices and levels of normal daily sounds. Therefore, BAER tests of Cavaliers should be at as low a decibel intensity threshold as possible – no higher than 30 dB.

CKCSs may be tested as early as eight weeks of age for congenital deafness, once the puppies’ ear canals are completely open. However, the condition of progressive hearing loss – due to degeneration of the hearing nerve – has a later onset and cannot be detected in young puppies.

Breeders' Responsibilities

No Cavalier suffering from an hereditary hearing deficiency should be bred. Dr. Podell and the Canine Inherited Disorders Database (www.upei.ca/~cidd/intro.htm) recommend that CKCS breeding stock be tested for hearing deficiencies prior to being bred. BAER testing should be conducted at no younger than age 2.5 years, and at the low decibel intensity threshold of 30 dB, to assure that the Cavaliers do not suffer from the hereditary disease of deafness which they would pass along to their litters.