Influence of different types of surface electrodes on amplitude, area and duration of the compound muscle action potential

Abstract

Objectives: The aim of this study was to evaluate if the type of surface electrode (disposable/non-disposable, fixed/variable inter-electrode distances, different surface structure and size of recording area) influences the compound muscle action potential (CMAP) values of baseline-to-peak and peak-to-peak amplitude and corresponding areas and duration. Methods: We investigated a total of 72 CMAPs of the abductor digiti minimi and the tibial anterior muscle of 18 healthy persons using 7 different types of electrodes in each muscle. Results: There was no significant difference of CMAP values between the electrodes which had a variable inter-electrode distance. A significant difference of all CMAP values was observed when these electrodes were compared with a bar-electrode with a fixed inter-electrode distance ( P<0.001). There was no correlation between recording area of the electrodes and the absolute CMAP values. Only the differences of CMAP values between each electrode and a defined electrode in each subject revealed a significant correlation between the size of recording area and these differences of CMAP values. Conclusion: To avoid false results in motor neurography only electrodes with variable distances between the recording pairs should be used. Using those electrodes and following standardized measuring conditions, CMAP values can be compared even if they are measured in different laboratories and at different occasions.