Contribution of reference electrode to the compound muscle action potential. Muscle Nerve 2007 Jul;36(1):87-92
Date
04/25/2007Pubmed ID
17455266DOI
10.1002/mus.20798Scopus ID
2-s2.0-34347355432 (requires institutional sign-in at Scopus site) 57 CitationsAbstract
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.
Author List
Nandedkar SD, Barkhaus PEAuthor
Paul E. Barkhaus MD Professor in the Neurology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Action PotentialsElectric Stimulation
Electrodes
Humans
Median Nerve
Muscle, Skeletal
Neural Conduction
Reaction Time
Reference Values
Ulnar Nerve
