May
13
2009

Testing for canine deafness is a desirable diagnostic for dog owners and breeders, but the cost for veterinary clinics can be prohibitive. A study on a different, less costly test could pave the way for practices to perform this test in-house.

The currently accepted method for diagnosing deafness in dogs is the brainstem auditory evoked response (BAER) test, which detects electrical activity in the cochlea and auditory pathways. However, the equipment required for the test is expensive and testing sites are limited.

George Strain, PhD, professor of neuroscience at Louisiana State University School of Veterinary Medicine is an expert in the field of animal deafness. Strain recently completed a study on a cheaper, more readily available hearing test using a handheld device that measures distortion product otoacoustic emission (DPOAE).

“For the DPOAE test, two tones are projected into the ear, which generates and produces a response tone, (the distortion product). The amplitude of this tone is then measured, and frequencies are assessed along the range of hearing,” Strain explained. “The strength of the response tone indicates whether the animal can hear at the tested frequency. The same test is often used to screen human babies for hearing ability.”

Strain’s study compared DPOAE and BAER in anesthetized adult dogs, awake adult dogs, and awake puppy litters. Strain said he is currently working on a manuscript to submit for publication, but admits that the process could take up to a year after the manuscript is accepted. Strain said there would be benefits to veterinary practices if the DPOAE test is validated.

“There is a significant demand for hearing testing by dog breeders and owners, and to a lesser extent by cat owners, to identify deaf (one or both ears) animals before breeding or to confirm hearing status in animals that appear to have hearing loss,” Strain said. “The handheld DPOAE device, at about $6K, is affordable, while most cannot justify the $25K of a BAER machine. This can potentially generate several thousand dollars in fees per year, depending on local demand.”

Although the handheld DPOAE test is currently available, it won’t be accepted until it is validated in comparison to the BAER test, Strain said.

“There will also be some time before the hearing registries and breed organizations of affected breeds accept the test,” he said.

While the study won’t appear in print for some time, Strain said his initial findings were intriguing.

“For most simple cases it appears to provide equivalent findings [to BAER],” Strain said. “More extensive testing will be required to clarify this.”

However, he said the BAER test will not become obsolete anytime soon.

“If DPOAE testing does become available, there will always be a need for referral of animals with equivocal or abnormal DPOAE results for BAER testing,” he said.

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