A comparison between middle latency responses and late auditory evoked potentials for approximating frequency-specific hearing levels in medicolegal patients with occupational hearing loss.

To evaluate the medicolegal relevance of middle latency responses for objectively approximating frequency-specific hearing levels in subjects with occupational hearing loss, we compared the middle latency response with the cortical response in 22 reliable subjects who had noise-induced hearing loss and were submitting claims for compensation and 21 subjects who had noise-induced hearing loss but were exaggerating the level of this loss and also were submitting claims for compensation. Middle latency components of auditory evoked potentials, especially the time-saving 40-Hz response, seem efficient and reliable for evaluating the true pure-tone thresholds (1, 2, and 3 kHz). A good correlation exists between the 40-Hz response threshold and the slow vertex response (SVR) threshold (long latency). Both also show a fairly close correlation with behavioral thresholds in cooperating subjects. However, in most cases, the 40-Hz response is less sensitive (mode of difference, 10 dB) than is the SVR. As middle latency response audiometry is not actually a time-saving procedure in comparison with cortical evoked response audiometry and as it seems less sensitive than the SVR for approximating the true threshold, the use of middle latency response audiometry seems best limited to situations in which a control or a confirmation of the SVR is wanted. Further information about the sensitivity of middle latency response to drug effects and to subject wakefulness (specifically, whether the patient is more or less sleepy) is expected.