EMG: decremental response of compound muscle action potential to repetitive nerve stimulation HP:0003430 EMG: decrement at repetitive stimulation HP:0003403 HP:0003478 UMLS:C4020841 The result of this test is abnormal if progressively fewer muscle fibers respond to nerve stimulation during a train of stimuli, thereby yielding a decrementing pattern in the CMAP. EMG: decremental response of CMAP to repetitive nerve stimulation UMLS:C4021728 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 a greater than normal decrease in the amplitude during the course of the investigation. EMG: impaired neuromuscular transmission