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Number and relative size of thenar motor units estimated by an adapted multiple point stimulation method
Author(s) -
Wang FrançoisCharles,
Delwaide Paul J.
Publication year - 1995
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880180908
Subject(s) - stimulation , physical medicine and rehabilitation , point (geometry) , medicine , psychology , neuroscience , mathematics , geometry
An adapted multiple point stimulation (AMPS) method is described for estimating the number and relative size of thenar motor units. With this method, the median nerve was stimulated at various sites from the wrist to the elbow. To avoid alternation, only two or three clearly identifiable surface‐recorded motor unit action potentials (S‐MUAPs) were recruited at each point by incremental stimulation. A total of 10 S‐MUAPs, eleicited from four to five distinct stimulatin points, was used to calculate the average S‐MUAP size. By dividing the maximum M‐potential size by that value, a motor unit number estimate (MUNE) was derived. In 59 healthy volunteers, from 19 to 87 years old, the mean average S‐MUAP size was 87 ± 27.6 μV. ms and the mean MUNE was 278 ± 113 motor units. When performed repeatedly, the results were reproducible. The number of motor units declined exponenetially with age while average S‐MUAP sized increased only moderately. To assess the validity of the AMPS method, its results were correlated with those obtained using the F‐response technique. The correlation coefficient was 0.83 ( P < 0.001). © 1995 John Wiley & Sons, Inc.