Electromyography and Nerve Conduction Studies

Electromyography (EMG) and nerve conduction studies (NCS) involve stimulating nerves with a small electrical current (NCS) and inserting a thin needle into the muscle (EMG) to measure electrical activity and uncover any neuromuscular abnormalities.


Why should I learn about electromyography (EMG) and nerve conduction studies (NCS)?

These tests are important diagnostic tools, because they can provide vital information about the health of your muscles and nerves. They can help detect the cause of problems, such as muscle weakness, numbness, spasms, paralysis or pain, and determine if the problem involves the nerves and/or muscles, or how nerves connect to the muscles.

How do EMG and NCS work?

Nerve and muscle cells produce tiny electrical currents. Nerves send electrical signals to muscles telling them to contract when needed, and muscles produce electrical activity when they move. Sick muscles or nerves may have changes in those electrical activities that are detected with these techniques.

How do EMG and NCS equipment detect changes?

Electrodes may be placed over the skin to detect electrical changes during NCS. During EMG, the needle is an electrode that is inserted inside the muscle for the same purpose. These electrical activities are recorded and displayed on a computer monitor and compared to normal data to detect dysfunction. We frequently use a speaker that allows us to listen to the signals for the same purpose.

What are the major uses of EMG and NCS?

Among others, these tests can help diagnose:

How do I prepare for these tests?

In general, no special preparation is necessary. However, the following advice may facilitate the experience and allow better recordings:

  • It is a good idea to bathe or shower on the day of the test, and wash arms and legs well to remove body oils and avoid the use of lotions or creams.
  • Since the test frequently involves examination of the hip area, it is a good idea to come prepared with a pair of SHORTS to change, or wear LOOSEFITTING clothes.
  • Tell your health care provider about all medications, especially if you:
    • Are taking any BLOOD THINNERS.
    • Have any implanted electronic device such as a PACEMAKER.
    • Have an area of SKIN INFECTION.
  • Eat your normal meals. Do not skip breakfast.
  • Allow plenty of time to come relaxed to the test.

Does EMG hurt?

Most people do feel some temporary pain or discomfort. However, most people tolerate this minor level of pain quite well. We will try adjusting the test to your level of tolerance and you would be able to stop it any time if you feel the discomfort is excessive. Using anesthesia is not recommended because we will need your cooperation.

Is the stimulus given during NCS painful?

Most people feel an unusual tingling sensation. Some may also experience slight temporary pain or discomfort.

Are there any risks involved with these tests?

Risks are usually very minor. People with certain medical conditions may face increased risks.

How long does the test last?

It depends a lot on the reason for the test but on average most tests would last between 30 minutes to one hour.

Are sterile needle electrodes used for EMG?

Yes! To prevent infection, needles are discarded once used.

How effective are these tests?

Very. These tests can help your health care provider to make an accurate diagnosis and develop an effective care plan for you.

Who performs EMG and NCS?

A specialist performs or supervises the testing and interprets their results. At Tufts Medical Center, these are fully trained neuromuscular specialists. Our technologist will perform part of the test, the NCS.

Don’t forget to ask questions before the procedure if you have any.