To the Editor.
—We wish to disagree with the negative conclusions reached by Anderson et al1 in their report on the usefulness of evoked potentials (EPs) to test a treatment of chronic multiple sclerosis (MS). We think that they have erred in their methodology and interpretation.Some tests may have been carried out in ways that differ with usual recommendations,2 in ways that can reduce EP quality: eg, the visual repetition rate was faster (3/s) and sometimes the auditory stimulus intensity may have been too soft (60 dB). The latter intensity was specified ambiguously. Common clinical experience with EPs should have forewarned these investigators about the difficulty and ambiguity in finding N14 or N20 in MS; a much better strategy would have been to study middlelatency somatosensory EPs where the peaks are unambiguous and reproducible in almost all MS patients. Several important technical parameters were unspecified: the filter
Nuwer MR, Ellison GW, Myers LW. Evoked Potentials During Multiple Sclerosis Therapeutic Trials. Arch Neurol. 1989;46(1):11–12. doi:10.1001/archneur.1989.00520370013005
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