Q. My doctor thinks I have a pinched nerve in my neck and wants to do an EMG test. What does EMG stand for, and how will this test help my doctor diagnose my condition?

A. EMG is short for electromyogram (elec-tro-my-oh-gram). This is a test that looks at the function of the nerve roots leaving your spine. Tiny electrodes are inserted into the muscles of your arm. If a nerve is irritated from pressure as it leaves your neck, the EMG will show abnormal signals in the muscle. Think of how you test the wiring on a lamp. If you place a working bulb into the lamp and the bulb lights up, you assume that the wiring is OK. But when the bulb does not light up, you can assume that something is probably wrong with the wiring. Either the lamp is unplugged, or there is a short circuit.

Like the light bulb in the lamp, the EMG checks your muscles to make sure the nerves that supply the muscles are working. If the EMG shows abnormal signals in your arm muscles (the light bulb) your doctor may assume that the nerves (the wiring) may be irritated or "pinched" somewhere between your neck and the muscles that were tested.