Clinical Application of Auditory Evoked Brain Stem Responses elicited by Bone-Conducted Stimuli

Auditory evoked brain stem responses elicited by air and bone-conducted sinusoidal one wave stimuli (0.5, 1, 2 and 4kHz) were studied in patients affecteed by conductive, neurosensory or mixed type hearing disorders. We set 0dBNSL as the mean sensation level of six normal hearing adults. As the maximum bone-conducted stimuli producible be our equipment is 45dBNSL, no responses may by elicited by bone-conducted stimuli when the patient's sensation level is more than 35dBNSL.The A-B gaps obtained by ABR were compared with the ones by pure-tone audiometry.The A-B gaps obtained by these two methods were approximately equal, but in some cases showed some differences varying from-20dB to+20dB.The bone-conducted ABR thresholds were compared with the puretone auditory thresholds for bone conduction. The ABR thresholds elicitied by low frequency stimuli were influenced by hearing level in high frequencies. But the thresholds by both methods were similar in all frequencies (0.5, 1, 2 and 4kHz). As regards frequency specificity, we also found the usefulness of the bone-conducted ABR thresholds in clinical cases.