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[Brainstem auditory evoked potentials in patients with multiple sclerosis--use of 2 stimulation frequencies]
Abstract:
The authors examined Brainstem acoustic evoked potentials at different frequencies of repeated clicks (10, 15, 20, 30 and 50 Hz) in 30 healthy subjects (18 men, 12 women, age 12-50 years) and in a group of 89 patients with the diagnosis of multiple sclerosis (28 men, 61 women, age 16-55 years). Examination of the control group revealed that an increase of the stimulation frequency from 10 to 50 Hz leads to a significant prolongation of the absolute latencies of BAEP waves (in particular V wave), as well as inter-peak latencies (in particular I-V) and to a reduction of the amplitude of waves I and V, which was, however, significant only in wave I. The differentiability of some waves, in particular late ones was reduced. For these changes a zone of normal values was assessed. In patients with multiple sclerosis at a stimulation frequency of 10 Hz the most frequent abnormality of BAEP was a prolongation of the latency of the V wave and of I-V resp. At a stimulation frequency of 50 Hz the ratio of responses with undifferentiable waves V or III and V increased. The increase of the stimulation frequency from 10 Hz to 50 Hz led to a higher detection rate of abnormal BAEP findings in the whole group from 31% to 51% (p less than 0.001), in the sub-group of patients with a clinical lesion of the stem from 43% to 65% (p less than 0.01), in the sub-group without a clinically obvious lesion from 23% to 40% (p less than 0.01). In the sub-group of patients with a suspect diagnosis of multiple sclerosis, but without a clinically obvious symptomatology of the stem the detection rate of abnormal findings increased from 27% to 35% (NS). Based on their results, the authors are in favour of those views reported in the literature which consider the application of two stimulation frequencies during BAEP examinations useful for diagnostic purposes and recommend its inclusion in routine BAEP examinations of patients with multiple sclerosis, or suspect multiple sclerosis.