Electromyography (EMG) and nerve conduction velocity (NCV) studies are helpful when a nerve or muscle disorder is suspected. NCV is administered before EMG and measures the speed at which nerves transmit electrical signals.
During NCV, electrodes are placed on the skin over the nerve of a specific muscle or muscle group. A mild, brief electrical stimulus is delivered through the electrode, and the muscle response is detected, amplified, and displayed. The strength of the signal is also measured. Neurological conditions can cause the NCV to slow down or become slower on one side of the body.
EMG measures nerve impulses within the muscles. Tiny electrodes are placed in the arm and leg muscles. The electronic responses are observed using an oscilloscope. As muscles contract, they emit a weak electrical signal that can be detected, amplified, and tracked, providing information about how well they are working.