Nerve conduction studies evaluate the function of the peripheral nerves. In the clinical practice, the function of the motor nerves is the most commonly evaluated. The measurement is done while the the patient is under general anesthesia. Two small needles are inserted near the nerve and the nerve is stimulated with low electrical current. The stimulation of the nerve initiates muscle contraction. Distance from the stimulation to the recording site is measured as well as time needed for impulse to arrive to the muscle. Changes in the nerve conduction velocity indicate damage to the axon of the nerve, to its myelin sheath or both. Nerve conduction velocity helps to confirm the presence of the peripheral nerve disease and to choose the right nerve for the further investigation such as nerve biopsy.