Auditory-evoked responses of dogs with different hearing abilities

Sixteen dogs were separated into three groups, based on clinical impressions of their abilities to hear and historical information pertaining to their hearing loss: group I (n = 7) had normal hearing, group II (n = 4) had reduced hearing and group III (n = 5) were deaf. Monaural clicks of alternating polarities were used to elicit brainstem auditory-evoked responses. The responses of the normal group and of the reduced hearing group consistently had four major peaks (I, II, III-IV, V) with latencies similar to those previously reported in dogs with normal hearing. No difference (p greater than or equal to 0.05) was found in mean latencies of the four major waveforms when comparing the normal group with the reduced hearing group. Significant reductions in mean amplitudes of waves I (p less than 0.01) and II (p less than 0.025) were found in the reduced hearing group. No recognizable waves could be recorded from the deaf group, indicating a lack of peripheral auditory function.