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Effect of reference electrode position on the compound muscle action potential (CMAP) onset latency
Author(s) -
Phongsamart Gulapar,
Wertsch Jacqueline J.,
Ferdjallah Mohammed,
King John C.,
Foster D. Terrence
Publication year - 2002
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.10119
Subject(s) - compound muscle action potential , latency (audio) , electrophysiology , ulnar nerve , medicine , anatomy , computer science , telecommunications , elbow
Abstract Compound muscle action potential (CMAP) onset latency is interpreted to reflect the arrival time at the muscle of impulses in the fastest‐conducting motor nerve fiber. However, we have observed that the position of the reference or indifferent electrode (E2) affects CMAP onset latency. Motor nerve conduction studies (NCS) of the median, ulnar, and deep ulnar motor (DUM) nerves on 20 normal hands were performed using both traditional bipolar and experimental monopolar (referenced to the contralateral hand) montages. As the position of E2 was altered, the CMAP onset latency varied 0.1–0.5 ms for the median NCS, 0.1–0.3 ms for the ulnar NCS, and 0.1–1.5 ms for the DUM NCS. This study demonstrates that E2 recorded potentials are significant and vary with positioning, affecting motor onset latency. This has implications both for reference values and the physiologic interpretation of the CMAP waveform. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002