Length dependence of variables associated with temporal dispersion in human motor nerves

Temporal dispersion in motor nerves is associated with changes of amplitude , area, duration, and Fourier spectra of compound muscle action potentials (CMAPs) when comparing responses to proximal and distal stimulation. These changes depend on the length of the nerve segment. To quantitatively assess this dependence, motor conduction studies of nerve segments of various len gths were performed in the median, ulnar, and tibial nerves of 86 test subj ects, aged 4 to 73 years. Amplitude, area, duration, and spectral energy ab ove 49 Hz of CMAPs were measured. Values after distal and proximal stimulat ion of each nerve segment were compared to determine amplitude decay, area decay, protraction, and high-frequency attenuation. A significant length de pendence of amplitude decay was found in the tibial and ulnar nerves, of ar ea decay in the median and ulnar nerves, and of CMAP duration in the ulnar and tibial nerves. The length dependence of the high-frequency attenuation was significant in all nerves studied. This report provides normative data for variables associated with temporal dispersion. (C) 2001 John Wiley & So ns, Inc.