Auditory evoked response test strategies to reduce cost and increase efficiency: The postauricular muscle response revisited

We describe a number of techniques in auditory evoked response (AER) testin g for hearing loss which should decrease its cost and increase its efficien cy, making its use in infant hearing screening more viable. We demon strate the use of bit-stream averaging of the electrical signals from the head as a cheap alternative to analogue averaging and show that the average wavefo rms obtained are similar with both techniques. We demonstrate how the posta uricular muscle response (PAMR) can be potentiated by lateral rotation of t he eyes and argue that uncontrolled eye movements in previous studies have led to an unfounded belief that the PAMR is not stable. When eye rotation i s used to potentiate the PAMR, the response becomes very stable and so larg e in most subjects that it is clearly visible in the raw traces. We also de monstrate that when the PAMR is potentiated by eye rotation, stable PAMR wa veforms can be reliably obtained with tone bursts with frequencies up to an d above 8 kHz and with sound levels within 30 dB of the subjective detectio n threshold. As a result the PAMR can be used to rapidly determine an objec tive audiogram in most subjects within minutes. Finally, we demonstrate a c orrelation technique for detecting the PAMR without waveform averaging and the need for an expensive computer. We are sure that a combination of these techniques can be used to increase the efficiency of AER screening for inf ant deafness and lower its cost dramatically, Copyright (C) 2000 S. Karger AG. Basel.