Clinical value of electrodiagnostic studies in neuromuscular disorders

EMG and conduction studies provide the physician with a precise means of defining the multiple diseases affecting the peripheral motor-sensory unit. These studies frequently provide clues that may be useful in arriving at the appropriate therapeutic decisions and in determining prognosis. Normal results may also support a suspected clinical diagnosis of inorganic illness, providing no evidence of central nervous system disease can be defined. Like any other test, however, results of EMG may be false-negative in bona fide neuromuscular disorders. This is particularly true early in a disease process; in neuropathies restricted primarily to small, unmyelinated nerve fibers; and in certain of the less virulent diseases of muscle and muscle energy metabolism.