Deafness in Cavalier King Charles Spaniels
can be Congenital or Progressive
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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, 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 also has referred this disorder as abiotrophic sensorineural deafness and has described it as an inherited congenital sensorineural deafness which affects hair cells of the spiral organ. 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.
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. (The ruby cavalier at right is undergoing a BAER test.)
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. (Below is a BAER scan of a cavalier with hearing loss.)
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 60 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.
No cavalier suffering from an hereditary hearing deficiency should be bred. Dr. Michael Podell (right) recommends 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.
September 2012: UK Dr. Gert ter Haar heads RVC's new ear, nose, and throat clinic. UK's Royal Veterinary College has commenced an ear, nose, and throat referral clinic at the Queen Mother Hospital for Animals in London. Dr. Gert ter Haar heads the unit, which offers services including advanced diagnostics and treatment for PSOM in cavaliers, as well as CT and BAER diagnostics for deafness (plus hearing aid implants for selected patients), and diagnostics and treatment of cavaliers with brachycephalic airway obstruction syndrome (BAOS). Telephone 01707 666 365 for more information.
May 2012: OSU’s Dr. Cole needs normal hearing CKCSs for BAER tests, CT scans, and MRI scans. Dr. Lynette Cole (right) of Ohio State University’s Veterinary Dermatology and Otology Service needs cavaliers between the ages of 1 to 2 years old with no history of hearing loss for a two-day evaluation by BAER hearing tests, computed tomography (CT) scans, and MRI scans. The study pays for all testing. She writes:
“In the dog breed Cavalier King Charles Spaniel (CKCS), hearing disorders may be due to conductive hearing loss, which may occur with primary secretory otitis media (PSOM), or due to sensorineural hearing loss, which may occur when there is damage or an abnormality of the sensory cells in the cochlea or the auditory nerve.”
If you are interested in possibly enrolling your cavalier in the study, contact Dr. Cole at telephone number 614-292-3551 or email email@example.com. Click here for the OSU webpage. A pedigree is required for entry into the study, but will be kept confidential, as will all test results. Details of the study will be given individually on the phone or via email.
April 2011: Researchers seek DNA swabs to study hearing loss in cavaliers. The Canine Genetics Group at the Van Andel Research Institute and the Translational Genomics Research Institute is studying DNA patterns that contribute to hearing loss in the CKCS. Thus far, the group has identified such DNA patterns for four other breeds.
If you have a cavalier suspected of hearing loss, a saliva sample is all the group needs for the study. If you have an older cavalier with good hearing, the study needs DNA from those dogs, too, for "control" purposes. To obtain a free DNA kit, contact the Program for Canine Health and Performance at firstname.lastname@example.org Include your mailing address and tell them the number of kits you need for both affected cavaliers and healthy cavaliers. Blood samples from affected CKCSs, drawn by veterinarians, also are needed. Contact Elissa Boguslawski at email@example.com for blood sample submission instructions.
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).
Advances in assessing canine degenerative hearing loss. M. Podell. Proc Am Coll Vet Intern Med. 1999; 17:291-293.
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).
Veterinary Neuroanatomy and Clinical Neurology. Alexander de Lahunta, Eric N. Glass. Saunders 3d edit. July 2008; 438. Quote: "Congenital abiotrophic sensorineural deafness directly affects the hair cells in the spiral organ. ... The lesion is usually bilateral and occasionally also affects the hair cells of the vestibular system receptors. The inheritance usually involves an autosomal recessive gene. Although most of these abiotrophies cause deafness at a few weeks of age, occasionally the onset of deafness occurs later in life. In the cavalier King Charles spaniel, deafness may not be apparent until 3 or 4 years of age."
A Practical Guide to Canine and Feline Neurology. Curtis W. Dewey. John Wiley & Sons; 2008; 4-6. "Breed-associated neurologic abnormalities of dogs and cats. ... Cavalier King Charles Spaniels ... Congenital deafness."
Canine Inherited Disorders Database: http://www.upei.ca/~cidd/Diseases/nervous system disorders/deafness.htm
Deafness in Dogs & Cats. Strain, G.M. Nov. 2011. (Includes CKCSs).
Canine Deafness. George M. Strain. Vety.Clinics.Sm.Anim.Pract. Oct.2012. Quote: "Conductive deafness, caused by outer or middle ear obstruction, may be corrected, whereas sensorineural deafness cannot. Most deafness in dogs is congenital sensorineural hereditary deafness, associated with the genes for white pigment: piebald or merle. The genetic cause has not yet been identified. Dogs with blue eyes have a greater likelihood of deafness than brown-eyed dogs. Other common forms of sensorineural deafness include presbycusis, ototoxicity, noise-induced hearing loss, otitis interna, and anesthesia. Definitive diagnosis of deafness requires brainstem auditory evoked response testing."
Electrodiagnostic Evaluation of Auditory Function in the Dog. Peter M. Scheifele, John Greer Clark. Vet.Clinics of N.A.:Sm.Anim.Prac. Nov. 2012; 42(6):1241-1257. Quote: "Given the high incidence of deafness within several breeds of dogs, accurate hearing screening and assessment is essential. In addition to brainstem auditory evoked response (BAER) testing, 2 other electrophysiologic tests are now being examined as audiologic tools for use in veterinary medicine: otoacoustic emissions and the auditory steady state response (ASSR). To improve BAER testing of animals and ensure an accurate interpretation of test findings from one test site to another, the establishment of and adherence to clear protocols is essential. The ASSR holds promise as an objective test for rapid testing of multiple frequencies in both ears simultaneously."
Canine Brainstem Auditory Evoked Responses are not Clinically Impacted by Head size or Breed. Debra L. Kemper, Peter M. Scheifele, John Greer Clark. Physiology & Behavior. Feb. 2013. 110-111:190-197. Quote: "Accurate assessment of canine hearing is essential to decrease the incidence of hereditary deafness in predisposed breeds and to substantiate hearing acuity. The Brainstem Auditory Evoked Response (BAER) is a widely accepted, objective test used in humans and animals for estimation of hearing thresholds and deafness diagnosis. In contrast to humans, testing and recording parameters for determination of normal values for canine hearing are not available. Conflicting information concerning breed and head size effects on canine BAER tests are major contributors preventing this normalization. The present study utilized standard head measurement techniques coupled with BAER testing and recording parameters modeled from humans to examine the effect canine head size and breed have on BAER results. Forty-three adult dogs from fourteen different breeds [including the cavalier King Charles spaniel] had head size measurements and BAER tests performed. The mean latencies compared by breed for waves I, II, III, IV, and V were as follows: 1.46±0.49msec, 2.52±0.54msec, 3.45±0.41msec, 4.53±0.83msec and 5.53±0.43msec, respectively. The mean wave I-V latency interval for all breeds was 3.69msec. All dogs showed similar waveform morphology, structures, including the presence of five waves occurring within 11 milliseconds after stimulus presentation and a significant trough occurring after Wave V. All of the waveform morphology for our subjects occurred with consistent interpeak latencies as shown by statistical testing. All animals had diagnostic results within the expected ranges for each wave latency and interwave interval allowing diagnostic evaluation. Our results establish that neither differences in head size nor breed impact determination of canine BAER waveform morphology, latency, or hearing sensitivity for diagnostic purposes. The differences in canine head size do not have a relevant impact on canine BAERs and are not clinically pertinent to management or diagnostic decisions."