Clinical neurophysiology is an area of medical practice focused primarily on measuring function in the central and peripheral nervous systems, the autonomic nervous system, and muscles. The specialty identifies and characterizes diseases of these areas, understands their pathophysiology, and, to a limited extent, treats them. Clinical neurophysiology relies entirely on the measurement of ongoing function—either spontaneous or in response to a defined stimulus—in a patient. Each of the clinical neurophysiology methods measures function by recording alterations in physiology as manifested by changes in electrical waveforms, electromagnetic.