Extended High Frequency Brainstem Auditory Evoked Testing in Aging Canines

Presbycusis, or age-related hearing loss, has a common pattern of high frequency hearing loss that progresses as humans age. It is thought that canines experience a similar pattern of hearing loss as they age. Currently, there is little research on how aging impacts canine hearing acuity. This study was conducted to obtain data to determine if thresholds for the brainstem auditory evoked response (BAER) were different for two types of acoustic stimuli in older dogs. Ten dogs age nine or older were tested but data from two dogs were removed after the initial analysis. Threshold estimations were performed using clicks and 12kHz tonebursts. Stimuli were initially presented at a high intensity level of 92 dB peSPL. Wave V peaks were marked as the intensity decreased until peaks could no longer be identified; this was determined to be threshold. If no response was found at the initial presentation level of 92 dB peSPL, then intensity was increased to 102 dB peSPL. If no peak was identified at 102 dB peSPL, then testing was terminated and a no-response finding was recorded. For data analysis, 112 dB peSPL was used as threshold for the dogs with no responses. The results showed a statistically significant difference in the average thresholds for the click and 12kHz toneburst. The average threshold using clicks was 65.75 dB peSPL while the average threshold using 12kHz tonebursts was 92 dB peSPL. Since responses to clicks are thought to represent hearing sensitivity in the 2- 4kHz range and responses to 12kHz tonebursts represent higher frequency responses, the difference in hearing thresholds for a group of older canines might be an indication of a decline iv in auditory responses in higher frequency regions of the cochlea as canines age. It is possible hearing loss might be occurring within frequency regions above those assessed by click stimuli, and clinicians might want to consider incorporating high frequency toneburst testing into diagnostic BAER protocols in aging canines. More data on younger canines are needed before conclusions can be made about age-related hearing loss in canines