Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. An EMG is performed using an instrument called an electromyograph, which produces a record called an electromyogram. This test is used to determine more about the functioning of peripheral nerves in the arms and legs. It can show if a nerve is pinched, and estimate the severity and location of the pinched nerve.
EMG tests for the electrical impulse coming from the brain and/or spinal cord to the affected area. If this impulse is blocked somewhere along the spinal pathway, it may be delayed or reduced en route to its final destination. Abnormal function may imply that there is nerve injury or muscle dysfunction.
During an EMG, small, thin needles are placed in the muscle to record the electrical signals from the various leg or arm muscles. If a muscle is not receiving adequate impulses from its nerve, it broadcasts signals that indicate the muscle is confused.
When the needles are inserted, you may feel some pain and discomfort. The doctor will ask you to relax the muscle and then to tense it slightly. The electrical signals generated by your muscle are broadcast on a TV-like screen. When the needles are removed, you may experience some soreness and bruising, but this will disappear in a few days. There are no long-term side effects. If you are taking blood-thinning medications, have lung disease or are at risk for infection, tell the physician who is conducting the test. On the day of the test, do not put any lotions or creams on the area to be tested and do not wear any jewelry. Usually, you can get the results immediately after the test.