A nerve conduction study (NCS) is commonly conducted together with electromyography in order to evaluate muscle disorders. For the NCS, dermal electrodes are placed at intervals over the nerve to be examined, and a low-intensity current is introducted to generate action potentials. The velocity of the action potential is related to the diameter of the nerve fiber and the presence of a myelin sheath. Diseases of the myelin sheath characteristically reduce the nerve conduction velocity (NCV). The amplitude of the response is also measured.