Auditory brain stem evoked potentials: clinical promise of increasing stimulus rate

Auditory brain stem evoked potentials (ABEPs) were recorded from 10 adults and 10 children who where neurologically and audiometrically normal. ABEPs were recorded in response to 75 dB HL clicks presented at rates of 10/sec and 50/sec. Normative values were calculated for amplitude and latency, as well as for inter-peak amplitude ratio and a variety of inter-peak latency differences and interaural differences at the two stimulus presentation rates. Normative values of the effect of increasing stimulus rate were calculated as well. Measures of changes in ABEPs between stimulus rates of 50/sec and 10/sec were the only derived measures that were significantly different between our adult and child normal populations. In addition, 50 patients with various conditions affecting the brain stem were examined. Increasing stimulus presentation rate had a significant effect on detection of abnormality in ABEPs from the patients examined. Measures of changes in ABEPs between stimulus rates of 50/sec and 10/sec seemed to be sensitive to a subset of abnormalities in our patient population. The case histories of the patients indicate that the subset may be impaired synaptic function. Measures of the effect of rate on ABEPs may complement the traditional measures that are primarily sensitive to white matter lesions.