Optimal E2 (reference) electrode placement in fibular motor nerve conduction studies recording from the tibialis anterior muscle.

Introduction: In this study we aimed to determine the contribution of the E2 (reference electrode) to the compound muscle action potential (CMAP) amplitude during fibular motor recording to the tibialis anterior (TA) when E2 is placed over routine referential vs. alternative sites.

Methods: The CMAP was obtained from 10 healthy subjects, using the active electrode (E1) over sites routinely used as E2 for the TA, whereas the E2 was over the contralateral knee. The same procedure was performed with the E1 over alternative E2 sites.

Results: Significant electrical signal was captured over routine E2 placement sites. Among the tested alternative E2 sites, the ipsilateral patella (especially its medial aspect) was the most electrically silent.

Discussion: Using alternative E2 sites with near isoelectric recordings can optimize near-field potential measurement in the fibular motor recording to the TA and represents a more accurate way of measuring nerve and muscle function. Muscle Nerve 59:249-253, 2019.