EMG: incremental response of compound muscle action potential to repetitive nerve stimulation UMLS:C4022579 A compound muscle action potential (CMAP) is a type of electromyography (EMG). CMAP refers to a group of almost simultaneous action potentials from several muscle fibers in the same area evoked by stimulation of the supplying motor nerve and are recorded as one multipeaked summated action potential. This abnormality refers to an abnormal increase in the amplitude during the course of the investigation. This feature may be observed with Lambert-Eaton Myasthenic Ssyndrome. EMG: impaired neuromuscular transmission