A nerve conduction study (NCS) is one part of a comprehensive nerve and muscle diagnostic test. Patients who have symptoms of persistent radiating pain from the neck or back, numbness, weakness or tingling in an arm or leg are possible candidates for a nerve conduction study.
Nerve conduction studies are usually done to help diagnose nerve and muscle disorders. They detect and evaluate damage to the peripheral nervous system and aide in evaluating the physiology and functioning of the peripheral nerves.
Surface patch-like electrodes are placed on the skin over the nerve at various locations. One electrode stimulates the nerve with a very mild electrical impulse. The other electrodes record the resulting electrical activity. The distance between electrodes and the time it takes for the electrical impulses to travel between electrodes are used to calculate the nerve conduction velocity.
Nerve conduction studies can help diagnose pinched, damaged or under-functioning nerves. Carpal tunnel syndrome, in which the medial nerve is pinched within the wrist, can produce numbness, weakness or pain in the hand. Nerve conduction studies are exquisitely sensitive in detecting this condition. Another study in the arm involves the ulnar nerve at the portion of the elbow often called the crazy bone.
Nerve conduction studies can also help diagnose numbness, weakness or pain in the legs. One such condition, in which the peroneal nerve is impaired near the knee, can cause a "foot drop." Another condition involving the tibial nerve at the ankle is called a tarsal tunnel syndrome.
In certain patients there is a more widespread pattern of dysfunction of nerve impairment. This can be seen in people with diabetes, excessive alcohol consumption and a number of other medical conditions.
There are no risks associated with nerve conduction studies. Nothing is inserted into the skin, so there is no risk of infection. The voltage of electrical pulses is not high enough to cause any injury or permanent damage.