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Contribution of reference electrode to the compound muscle action potential
Author(s) -
Nandedkar Sanjeev D.,
Barkhaus Paul E.
Publication year - 2007
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.20798
Subject(s) - compound muscle action potential , reference electrode , electrode , electrophysiology , anatomy , electromyography , biomedical engineering , medicine , materials science , chemistry , physical medicine and rehabilitation , electrolyte
In compound muscle action potential (CMAP) recording, the contribution by the reference electrode is considered to be much smaller than that of the active electrode. We tested this assumption by making quantitative measurements of the signals recorded individually by the active and reference electrodes. In the thenar (median nerve) and extensor digitorum brevis (peroneal nerve) muscles, the reference electrode did contribute less. In the hypothenar muscle (ulnar nerve), however, the signals recorded by active and reference electrodes were of similar amplitude. In tibial nerve conduction studies (NCS), the CMAP from the abductor hallucis (AH) muscle was recorded mainly by the reference electrode; the large‐amplitude signal recorded by the reference electrode is attributed to volume‐conducted activity from other muscles stimulated during the study. The onset latency of the potential recorded by the active and reference electrodes was similar despite significantly different distances from the stimulating site. Hence, the merits of using anatomic landmarks for defining the distal stimulation site are assessed. When the reference electrode makes a large contribution, the CMAP amplitude may not decrease commensurate with any wasting of the muscle under the active recording electrode, and the need to use another muscle for recording the CMAP for that nerve should be considered. Muscle Nerve, 2007