An electromyogram (E.M.G.) is a test where needles are inserted into muscles in the spine area and into the extremities and then the electrical response of muscle is recorded on a special machine. The response of the muscle is a clue to the function of the nerves.

A nerve conduction velocity test (NCV) is performed by placing needles into specific nerve sites hooked up to a special machine that records the nerve's electrical conduction.