Interexaminer variance of median nerve compound muscle action potential measurements in hand position with and without fixation in plaster.
OBJECTIVE
We examined how hand fixation affects interexaminer variance in measuring compound muscle action potential (CMAP) during nerve conduction studies of the median nerve.


METHODS
Subjects comprised 6 experienced examiners [1 woman and 5 men; mean (SD) age, 38.3 +/- 8.5 years; range, 28-46 years]. The standardized median nerve motor conduction setting was used for electromyography. The mean of 5 serial stimulations was taken as 1 examination for each subject. Distal latency, conduction velocity, and peak-to-peak amplitude of CMAP were measured as parameters. Subjects were examined without hand fixation and with hands fixed in prepared plaster molds.


RESULTS
Fixation yielded significantly decreased coefficient of variance for CMAP amplitude (5.0% +/- 3.4%) compared with measurement without fixation (8.4% +/- 3.7%; P = 0.028). No differences in distal latencies or conduction velocities were evident between fixation and nonfixation.


CONCLUSIONS
This study provides quantitative evidence for empirical observations that hand fixation might decrease CMAP variability in median nerve studies.
Higuchi
Keiichi
K
Clinical Neurophysiology Unit, Matsusaka Chuo Hospital, Matsusaka, Mie, Japan.
Narita
Yugo
Y
Kuzuhara
Shigeki
S
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D002370:Casts, Surgical; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006225:Hand / Q000294:innervation* / Q000502:physiology; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology*; D015588:Observer Variation; D011187:Posture / Q000502:physiology; D011237:Predictive Value of Tests; D016059:Range of Motion, Articular / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D015203:Reproducibility of Results; D012149:Restraint, Physical; D014955:Wrist Joint / Q000502:physiology