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

Objectives: The aim of this study was to evaluate if the type of surface el ectrode (disposable/non-disposable, fixed/variable inter-electrode distance s, different surface structure and size of recording area) influences the c ompound 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 type s of electrodes in each muscle. Results: There was no significant difference of CMAP values between the ele ctrodes which had a variable inter-electrode distance. A significant differ ence of all CMAP values was observed when these electrodes were compared wi th a bar-electrode with a fixed interelectrode distance (P < 0.001). There was no correlation between recording area of the electrodes and the absolut e CMAP values. Only the differences of CMAP values between each electrode a nd a defined electrode in each subject revealed a significant correlation b etween the size of recording area and these differences of CMAP values. Conclusion: To avoid false results in motor neurography only electrodes wit h variable distances between the recording pairs should be used. Using thos e electrodes and following standardized measuring conditions, CMAP values c an be compared even if they are measured in different laboratories and at d ifferent occasions. (C) 1999 Elsevier Science Ireland Ltd. All rights reser ved.