Stimulus-response curve of human motor nerves: multicenter assessment of various indexes.
The value of various indexes to characterize the stimulus-response curve of human motor nerves was assessed in 40 healthy subjects recruited from four European centers of investigation (Créteil, Lausanne, Liège, Marseille). Stimulus-response curves were established by stimulating the right median and ulnar motor nerves at the wrist, with stimulus durations of 0.05 and 0.5 ms. The following parameters were studied: the threshold intensity of stimulation to obtain 10% (I 10), 50% (I 50), and 90% (I 90) of the maximal compound muscle action potential, the ratios I 10/I 50, I 90/I 50, (I 90 - I 10)/I 10, (I 90-I 50)/I 50, and (I 50 - I 10)/I 10, and the slopes of the stimulus-response curves with or without normalization to I 50. For each parameter, within-center variability and reproducibility (in a test-retest study) were assessed and between-center comparisons were made. For most of the parameters, the results varied significantly within and between the centers. Within the centers, only the ratios I 10/I 50 and I 90/I 50 were found constant and reproducible. Between the centers, the absolute intensity thresholds (I 10, I 50, I 90) and the ratio I 90/I 50 did not show significant differences at stimulus duration of 0.5 ms, whatever the stimulated nerve. The reduced variability and good reproducibility of the ratios I 10/I 50 and I 90/I 50 open perspectives in neurophysiological practice for the use of these indexes of the stimulus-response curve, a rapid and noninvasive test.
Boërio
D
D
Service de physiologie-explorations fonctionnelles, hôpital Henri-Mondor, AP-HP, 94010 Créteil, France.
Hogrel
J-Y
JY
Lefaucheur
J-P
JP
Wang
F C
FC
Verschueren
A
A
Pouget
J
J
Carrera
E
E
Kuntzer
T
T
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000465:Algorithms; D004558:Electric Stimulation; D004568:Electrodiagnosis; D004576:Electromyography; D005060:Europe; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D010525:Peripheral Nerves / Q000502:physiology*; D015203:Reproducibility of Results; D012881:Skin Temperature / Q000502:physiology; D014459:Ulnar Nerve / Q000502:physiology