An intrasubject comparison of electric and acoustic middle latency responses

The middle components of the auditory evoked response (middle latency response, MLR) were evoked by acoustic clicks from the normal-hearing ear and by charge-balanced biphasic current pulses from the severe-to-profoundly hearing-impaired ears of patients undergoing labyrinthectomy for the management of intractable vertigo. A vertex-positive peak with a latency ranging from 27 msec to 38 msec (Pa) was characteristic of both the electric and the acoustic MLR. In subjects, the electric Pa always preceded the acoustic Pa in latency. In addition, the electric Pa had a sharper appearance than did the acoustic Pa. The electric MLRs were elicited by a range of stimulus intensities and persisted after the completion of labyrinthectomy.