Neuromuscular response in man to repetitive nerve stimulation

Abstract
Paired stimulation has been used extensively in clinical neuropathysiology. We studies change in the sizes of compound muscle action potencial (CNAPs) in humans after a single electrical stimulus to the peripheral nerve. When the interstimulus intervals were varied, the second potentials underwent refractoriness and then were facilitated up to 20–30 ms, thereafter being depressed for 160–200 ms. When intensities were graded at fixed intervals for motor fibers the maximal effects was obtained with liminal stimulation, but was no longer observed at supramaximal stimulation. When the intrensity used to obtain M‐resposes was half the maximum, maximal facilitations were 35% (CNAP) and 17% (CMAP) of the first potential, the respective maximal depressions being 13% and 42%. When the sizes of the two CNARs were equalized by adjusting the second stimuli, the CMAP was facilitated (26%) up to 65 ms, thereafter being depressed (13%). These results must be taken into account when making clinical examinations that use paired stimulation. © 1993 John Wiley & Sons, Inc.