SENSORY AND MOTOR NERVE CONDUCTION IN THE MEDIAN NERVE IN NORMAL SUBJECTS

Abstract. The normal nerve conduction in sensory and motor fibres of the median nerve has been studied in 20 females and 28 males, 16–62 years of age. There was no significant sex difference in conduction velocity. The intraindividual variation in repeated measurements was 0.9–1.8 m/sec. The conduction velocity decreased with age in all segments, and the interindividual variation was 3.4 to 4.5 m/sec (Syx). Sensory fibres conducted faster than motor fibres of the same segment, but the difference became gradually eliminated with age. The sensory conduction velocity in the proximal segment (wrist‐elbow) decreased more rapidly with age than in the distal segment (digit‐wrist). Fast and more slowly conducting fibres were almost equally affected by age, resulting in an increase in the temporal dispersion of the sensory action potential. The amplitude of the sensory potential (log10 μV) was a function of the temporal dispersion and of the distance of the near nerve electrode from the nerve. With these corrections the amplitude was independent of age, i.e. there was no evidence of a reduction in the number of fibres. The sensory threshold to electrical stimuli increased with age and—independent of age—with the slowing of the sensory conduction velocity between wrist and elbow.