The Range of Conduction Velocity in Normal Motor Nerve Fibres to the Small Muscles of the Hand and Foot

Abstract

Although measurements of nerve conduction velocity in man were first made nearly a hundred years ago, the procedure was not used clinically until 1948 when Hodes, Larrabee, and German reported reduced conduction velocity in regenerating motor nerves. Later, Hodes (1949) described slow conduction in surviving nerve fibres after poliomyelitis, and more recently it has been shown that conduction may also be slow in certain localized peripheral nerve lesions (Simpson, 1956), in polyneuritis, and in peroneal muscular atrophy (Henriksen, 1956;Lambert, 1956; Gilliatt and Thomas, 1957;Gilliatt and Sears, 1958).The use of conduction velocity measurement as a diagnostic procedure in neurology requires a knowledge of the range of values encountered in healthy individuals. Normal values for maximum conduction velocity in human peripheral nerves have already been described by Norris, Shock, and Wagman (1953) and by Henriksen (1956), but in order to obtain a control series for our own laboratory, we have estimated maximum conduction velocity in 180 normal nerves supplying the small muscles of the hands and feet. Our own results, which are in good agreement with those of previous writers, are contained in the first part of this paper.In estimating conduction velocity, the motor nerve trunk is stimulated at two levels and the time interval between the stimulus and the onset of the muscle action potential recorded in both instances. This interval represents conduction time in the largest and most rapidly conducting motor nerve fibres stimulated, together with a further delay at the neuromuscular junction and in the muscle itself. Provided that both stimuli are supramaximal, the difference in latency of the two muscle responses is a valid estimate of conduction time in the most rapidly conducting fibres in the nerve trunk between the two points stimulated. However, conduction time in the smaller and more slowly conducting fibres of a motor nerve cannot be measured in this way as the time of onset of their muscle action potentials is obscured by the discharge of earlier units.This point is of some clinical importance, as it is not uncommon for patients to show values for maximum conduction velocity that are slightly below the accepted normal range; in such a case the question arises as to whether this represents conduction in abnormal fibres or whether it could be due to conduction in slow normal fibres uncovered by the loss of the larger and more rapidly conducting ones.In order to obtain some evidence on this question, we have attempted to compare the conduction times of different nerve fibres supplying a single muscle; the results of this investigation are presented in the second part of the paper. MethodsAll tests were performed in a warm room with the subject lying on a couch and covered with blankets. In a few subjects with cold hands or feet, the limbs to be tested were immersed in hot water for five or 10 minutes before the session, but no other method of controlling temperature was attempted.In measurements of maximum co...

Normal sensory conduction in the nerves of the leg in man

“…The maximum sensory conduction velocity along the superficial peroneal, sural, and posterior tibial nerve was the same. In contrast with Thomas, Sears, and Gilliatt (1959) In the nerves of the leg, as of the arm, the maximum sensory velocity along the distal segments was slower than the proximal velocity, slowing being most pronounced along the terminal branches. As in the median and ulnar nerves the maximum velocity in the nerves of the leg was lower at 40 to 65 years of age than at 15 to 30 years, slowing with age being equally pronounced along distal as along proximal segments.…”

Selective recruitment of high‐threshold human motor units during voluntary isotonic lengthening of active muscles.

“…This suggests that these motor units are made up of a high number of large muscle fibres (Olson, Carpenter & Henneman, 1968). (4) The conduction velocity of the two motor axons, which could be measured through stimulation of the gastrocnemius medialis nerve in two points, falls in the upper range of conduction velocities measured for the motor nerves of the leg in humans (Thomas, Sears & Gilliatt, 1959;Mayer, 1963;Mavor & Atcheson, 1966;Behse & Buchthal, 1971;Ingram, Davis & Swash, 1987). The parent axon of ten more motor units in this group was also excited by the very low stimulus strengths in either stimulating site, indicating a large diameter of the fibre.…”

Health hazard evaluation report: HETA-80-111-861, Lear Seigler Company, Marblehead, Massachusetts.

“…Electrophysiologic evaluations included electromyography of the anal sphincter and measurement of sacral latency time using ring electrodes around the penis (11). Standard nerve conduction studies (1,5,12) of the right peroneal and right sural nerves were performed. F-wave latencies in the peroneal were also determined.…”