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 hereditary 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.
Related Links
Questions for Breeders
Primary Secretory Otitis Media
(PSOM)
Board Certified Veterinary
Neurologists
Veterinary Resources
Investigation of hearing impairment in Cavalier King Charles spaniels, using auditory brainstem response audiometry. Munro, K.J., Cox, C.L. J. Small Animal Prac.1997,38:2-5. Quote: "Auditory brainstem response audiometry was used to investigate nine Cavalier King Charles spaniels with a history of hearing impairment. Successful recordings were made in all cases. In eight of the dogs, the hearing impairment was between 40 and 85 decibels re normal hearing level. In addition to confirming the degree of impairment in each ear, information was obtained concerning the site of the lesion. The auditory brainstem technique may have an important role to play in assessing treatment outcome. Other applications include screening animals used in breeding programmes as well as working dogs requiring good binaural hearing."
Hearing Assessment in Cavaliers. Podell, M. CKCSC,USA Bulletin, Fall 1998; p. 21. Quote: "Deafness is an increasingly recognized problem of a number of pure-bred dogs, and more recently, has been documented as a congenital problem in the Cavalier King Charles Spaniel. Hearing loss may be due to a problem conducting sound waves through the middle ear (conductive loss) or to a problem related to the hearing receptors or nerve in the inner ear (sensorineural hearing loss). Conductive hearing loss usually is a problem related to ear infection(s) or aging. Sensorineural hearing loss occurs most commonly as a congenital disease; that is, the condition is present from birth. The loss can be complete, leading to deafness, or partial, leading to abnormal hearing function. ... Recently, a new finding has emerged in studying congenital deafness in Cavaliers. Rather than present with complete hearing loss in one or both ears, a particular line of dogs has developed a progressive hearing loss as they matured over first few years of life. These dogs were documented to have a normal BAER test as young puppies, using standard testing. However, over time, the dogs developed significant hearing loss, even to the point of being deaf. This type of hearing loss may be quite different from that of other breeds, in that the hearing nerve may be degenerating, rather than failure of formation or early degeneration of the inner ear receptors. This type of hearing loss may be similar to that seen in progressive nerve degeneration in young children and adolescents. This condition presents a unique problem in that puppies may test completely normal, and then be found to develop later onset hearing nerve degeneration after already passing on a potentially inherited disorder."
Congenital Deafness and Its Recognition. Strain, G.M. Veterinary Clinics of N.A.: Small Animal Practice - Spec.Iss., Pediatrics - July, 1999. (Includes CKCSs).
Pet Care in the New Century: Cutting-Edge Medicine for Dogs and Cats. Shojai, AD. 2001, New Amer Library, p.185. Quote: "Dr. Michael Podell ... reports that a particular line of CKCSs seems to present a new type of deafness. Instead of the more typical complete hearing loss in one or both ears from birth, puppies have normal hearing at birth and develop a progressive hearing loss over the first few years of life, even to the point of becoming deaf. Dr. Podell suspects this type of hearing loss is caused by degeneration of the hearing nerve. The new condition poses a problem in screening such dogs to keep potential breeders from passing on the tendency to their offspring. Further studies are underway to identify tests that may be useful in predicting which dogs may develop such a hearing problem."
Deafness prevalence and pigmentation and gender associations in dog breeds at risk. George M. Strain. Vet. J. 2004; 167:23–32. (Includes CKCSs).
Canine Inherited Disorders Database: http://www.upei.ca/~cidd/Diseases/nervous system disorders/deafness.htm
Deafness in Dogs & Cats. Strain, G.M. http://www.lsu.edu/deafness/deaf.htm (Includes CKCSs).
