A nerve conduction velocity (NCV) test is used to assess nerve damage and dysfunction. Also known as a nerve conduction study, the procedure measures how quickly electrical signals move through your peripheral nerves. Peripheral nerves start where the nerve root takes off from the spinal cord. These nerves help control your muscles and experience the senses. Healthy nerves send electrical signals more quickly and with greater strength than damaged nerves. The NCV test helps doctor differentiate between an injury to the nerve fiber and an injury to the myelin sheath, the protective covering surrounding the nerve. It can also help doctor tell the difference between a nerve disorder and a condition where a nerve injury has affected the muscles. Making these distinctions is important for proper diagnosis and determining course of treatment.