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Electromyography EMG - Myogram

Electromyography is a test that assesses the health of the muscles and the nerves controlling the muscles. EMG is most often used when people have symptoms of weakness and examination shows impaired muscle strength. It can help to differentiate primary muscle conditions from muscle weakness caused by neurologic disorders.

How the Test is Performed

For an EMG, a needle electrode is inserted through the skin into the muscle. The electrical activity detected by this electrode is displayed on an oscilloscope, and may be heard through a speaker. After placement of the electrodes, you may be asked to contract the muscle (for example, by bending your arm). The presence, size, and shape of the wave form -- the action potential -- produced on the oscilloscope provide information about the ability of the muscle to respond when the nerves are stimulated.

A nerve conduction velocity test is usually performed in conjunction with an EMG.

How to Prepare for the Test

No special preparation is usually necessary. To ensure accurate readings, avoid using any creams or lotions on the day of the test.

How the Test Will Feel

There may be some discomfort with insertion of the electrodes (similar to an intramuscular injection). Afterwards, you may have some soreness of the muscle.

What the Risks Are

  • Bleeding (minimal)
  • Infection at the electrode sites (minimal risk)

Special Considerations

Trauma to the muscle from EMG may cause false results on blood tests (such as creatine kinase), a muscle biopsy, or other tests.

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