Electromyography and Nerve Conduction Tests are ordered to learn more about the health of peripheral nerves. These tests can establish if a nerve is pinched, and give a numeric value to how severely it is pinched and often where it is pinched. The test can last anywhere from a half an hour to an hour. The quality of the results is quite dependent on the skill of the person administering the test.
During the Nerve Conduction portion of the test, electrodes much like EKG patches are placed along the known course of the nerve. The nerve is stimulated with a tiny electrical current at one point. The nerve must then transmit the signal along its course, and an electrode placed further down the arm or leg captures the signal as it passes it. A healthy nerve will transmit the signal faster and stronger than a sick nerve.
The EMG portion of the test measures the electrical activity in muscles. Muscles normally receive constant electrical signals from healthy nerves, and in return "broadcast" their own healthy electrical signals. During the EMG portion of the test, the doctor places acupuncture like needles into the muscles to record the electrical signal from the various muscles in the arm or leg. If a muscle doesn't receive adequate signals from a sick nerve, it broadcasts signals, which show the muscle is confused.
From the Nerve Conduction Test and the EMG's, the doctor can correlate which nerves are pinched and the seriousness of the condition. This information can then be used to help formulate further treatment plans.