OBJECTIVE When the compound muscle action potential (CMAP) is recorded in motor nerve conduction studies, the reference (E2) electrode can make a significant contribution to the CMAP. This study investigates the E2 recorded signal and its effect on CMAP measurements when E2 electrode is placed at different sites. METHODS The CMAP was recorded using the active electrode on the muscle belly and 4 different E2 electrodes placed at distal and proximal sites. The signal recorded by each electrode was also measured using a reference electrode on the contralateral limb. Signals were recorded from the abductor pollicis brevis, abductor digiti minimi, tibialis anterior and biceps muscles. RESULTS The E2 recorded a smaller signal when it was placed near or off the proximal tendon or muscle origin. This affected CMAP latency, duration for tibialis anterior. Contrary to expectation, initial upward deflection was noted for E2 signal. CONCLUSION A proximal E2 position records a lower volume conducted signal and yields a CMAP that is more representative of the muscle over which the E1 (active) electrode is placed. SIGNIFICANCE The proposed 'Proximal E2' montage may be better suited to assess pathology.

中文翻译：

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参比电极位置对复合肌肉动作电位的影响

目标当复合肌肉动作电位 (CMAP) 在运动神经传导研究中被记录时，参考 (E2) 电极可以对 CMAP 做出重大贡献。本研究调查了当 E2 电极放置在不同位置时 E2 记录的信号及其对 CMAP 测量的影响。方法 使用肌肉腹部的有源电极和放置在远端和近端部位的 4 个不同的 E2 电极记录 CMAP。还使用对侧肢体上的参考电极测量每个电极记录的信号。从拇短外展肌、小指外展肌、胫前肌和二头肌记录信号。结果 当 E2 被放置在近端肌腱或肌肉起点附近或附近时，它记录到一个较小的信号。这影响了 CMAP 潜伏期，胫骨前肌的持续时间。与预期相反，注意到 E2 信号的初始向上偏转。结论 近端 E2 位置记录了较低体积的传导信号，并产生更能代表放置 E1（有源）电极的肌肉的 CMAP。意义 提议的“近端 E2”蒙太奇可能更适合评估病理。