What is a Nerve Conduction Study (NCS)?
A Nerve Conduction Study, or NCS, is a test designed to measure the function of a nerve. There are 3 major types of nerves: motor, sensory, and autonomic. Motor nerves carry information from the spinal cord to the muscle. Sensory nerves carry information from a sensory organ such as the skin or the eye to the spinal cord or brainstem. Autonomic nerves carry information from the spinal cord to an internal organ such as the heart, a blood vessel, or a sweat gland. Nerves are also described based on size and amount of insulation. Fast conducting fibers tend to be large and heavily insulated by a fatty material called “myelin”. Slow conducting fibers tend to be narrow and minimally insulated. Routine Nerve Conduction studies test large diameter motor and sensory fibers only. There are no well standardized tests, at this time, for smaller diameter fibers such as autonomic fibers and “c-fibers”, which are the most important fibers for pain and temperature sensation.
