The effects of ABR stimulus repetition rate in multiple sclerosis.

The purpose of this study was to monitor the effects of auditory brain stem response (ABR) repetition rate in previously confirmed multiple sclerosis (MS) patients. Ten definite MS patients (20 ears) presenting neurological evidence of brain stem involvement were tested. All patients had hearing thresholds of 20 dB HL or better between 250 and 4000 Hz. ABRs were recorded with four click stimulus repetition rates at 70 dB SL. An analysis of variance (ANOVA: Group X Rate X Ear) resulted in significant group (normal versus MS) and rate (10, 33, 67, and 80/sec) effects. Increasing the repetition rate significantly improved the detection of abnormal latency measures (Duncan's multiple range test). Absent or prolonged wave I response latencies were recorded in 25 to 40% of all MS patients tested and were rate dependent. The findings of this study encourage the inclusion of faster repetition rates when using ABR as a supportive measure in the diagnosis of suspected MS patients.