Contribution of high click stimulus repetition rate in auditory evoked potentials in multiple sclerosis patients with normal mri
Abstract
The purpose of this work was to evaluate if a stimulus reptition rate that is higher than 30 clicks/sec increases the sensitivity of the absolute latencies of waves I, III and V and interpeak intervals I-III, III-V and I-V in the Auditory Brainstem Responses.(ABR) of Multiple Sclerosis (MS) patients.
Method: The ABR results of 20 female and 9 male MS patients (according to Poser’s Classification, but normal brainstem magnetic resonance imaging ) were compared to the results of 20 female and 20 male controls. 2000clicks of 100ms and at 60dBSPL above psychoacoustic threshold for clicks were delivered monoaurally with a TDH-39 supra-aural transducer, and white noise counter-lateral masking, at 11clicks/sec. Rarified polarity, 100Hz and 2500Hz filters and a 12ms window were used. All subjects were submitted do a progressively higher repetition of the stimulus, i.e. 31,51, 61 clicks/sec in subsequent ABR exams of the right ear followed by the left ear. Results: There was a statistically significant difference in the absolute latency of wave III in the MS group using 51 and 61 clicks/sec, wave V using 51 and 61 clicks/sec in the male MS group and I-III interval using 51 and 61clicks/sec in the male MS group. Conclusion: ABR using a stimulus rate of 51 and 61 clicks/sec should be included in the diagnosis of patients with a hypothisis of a demyeliating disease such as MS.
