Longitudinal study of brainstem auditory evoked responses in 87 normal human subjects.

We evaluated the reproducibility of brainstem auditory evoked responses (BAERs) in 87 normal individuals in a longitudinal study by estimating the correlation coefficients and variability of the interpeak intervals and the V/I amplitude ratio between trials on the same day and between sessions spaced 2 years apart. The highest correlation coefficients occur for the I-V interpeak interval between trials on the same day. The coefficients for the I-III and III-V intervals are lower, due to the variability of wave III. The correlations between ears done on the same day are lower still and are similar to measures obtained from the same ear at a 2-year interval. BAERs are more variable than previously believed between ears and over time, but not in a manner that is clinically significant and can be used longitudinally as a measure of neurologic disease. Finally, we provide the sample size required to detect a significant change in interpeak intervals.