Issue N# 3 - 2004
High click stimulus repetition rate in the auditory evoked potentials in multiple sclerosis patients with normal MRI. Does it improve diagnosis?
Authors : M. A. Rocha Santos, M. S. Lei Munhoz, M. A. Lana Peixoto, C. Santos Silva (Belo Horizonte)
Ref. : Rev Laryngol Otol Rhinol. 2004;125,3:151-155.
Article published in english
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Objective: The purpose of this study was to evaluate whether auditory brainstem responses (ABR) in multiple sclerosis (MS) patients were qualitatively different from a normal population. Material and method: This study analysed 69 subjects, separated into two groups; a control group composed of 20 females and 20 males; and an MS group composed of 20 females and 9 males. The controls had no history of neurological or otorhinolaryngological disorders. All MS patients presented a normal magnetic resonance imaging of the brainstem. A definite diagnosis of MS was given according to Poser’s criteria for MS research protocols (1983). The following parameters were used in the sutdy of the ABR of each subject: 2000 clicks of 100 ms at 60 dB equivalent peak of sou nd pressure level (pe SPL) above the psycho-acoustic threshold, obtained with the subject’s response to clicks. Both ears were initially stimulated at 11 clicks/s, and then with clicks of same intensity, but with a progressive increase of the stimulus rate to 31, 51, 61 and 71 clicks/s. The analysis of variance with independent factors and repeated measures was used in the statistical analysis of the comparison between group results. Results: The absolute latency of wave III was statistically greater, with a stimulus rate of 51 and 61 clicks/s, in the MS group. The males in the MS group presented a statistically greater absolute latency of wave V with the use of 51 and 61 clicks/s. With stimulus rates above 30 clicks/s, the absolute latency of wave V was also greater for MS females. There were statistically significant differences in the interpeak interval I - III of the control group compared to the MS group, for stimulus rates of 51 and 61 clicks/s, in females and for the stimulus rate of 61 clicks/s in males. This interval was higher in the MS group with these stimulus rates. Conclusion: The results suggest the inclusion of stimulus rates of 51 and 61 clicks/s in the ABR tests of subjects with clinical suspicion of demyelinating diseases like MS.
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