Quantitative Compound Muscle Action Potential: Summary

The CMAP (compound muscle action potential) represents the recorded sum of all the individual muscle eber action potentials when the motor nerve to that muscle receives a supramaximal square-wave electrical stimulus, and a ‘belly-tendon’ electrode montage is used and there is standardized grounding. The CMAP, which is customarily a biphasic potential with erst a negative and then a positive phase, is used to obtain conduction velocity of motor nerves, and changes in CMAP wave forms, such as amplitude of the negative phase, area, duration, and morphological alterations (dispersion), are used to gather evidence of abnormal innervation or loss of activated muscle ebers. CMAPs can be obtained from any muscle, but the cellular organization and innervation of the muscle must be known and recording techniques standardized. 1