EMG / NCT / NCS

What is a Nerve Conduction Study (NCS) or Nerve Conduction Test (NST) ?


  • A nerve conduction test —  measures how fast an electrical impulse moves through your nerve. It can identify nerve damage.
  • During the test, your nerve is stimulated, with electrode patches attached to your skin. Electrodes are placed on the skin over your nerve. One electrode stimulates your nerve with a very mild electrical impulse. The other electrode records it. The resulting electrical activity is recorded by another electrode. This is repeated for each nerve being tested.
  • The speed is then calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes.
  • The nerve conduction test helps find the presence, location, and extent of diseases that damage the nerves and muscles.
  • The voltage of the electrical pulses used during an NCS is considered very low.
  • Risks depend on your specific medical condition. Be sure to discuss any concerns with your healthcare provider before the procedure.
  • Certain factors or conditions may interfere with the results of NCS tests. This includes damage to the spinal cord, severe pain before the test, and body temperature.
  • Tell your healthcare provider if you have a cardiac defibrillator or pacemaker, as

precautions may need to be taken.

How do I get ready for an NCS?

  • You will be asked to sign this consent form
  • Dress in clothes that allow access to the area to be tested or that are easily removed.
  • Stop using lotions or oils on your skin for a few days before your procedure.

What happens during the NCS?

  1. You will be asked to remove any clothing, jewelry, hairpins, eyeglasses, hearing aids, or other metal objects that may interfere with the procedure.
  2. If you are asked to remove clothing, you will be given a gown to wear.
  3. You will be asked to lie down for the test.
  4.  Dr. Yong Tsai will locate the nerve(s) to be studied.
  5. Medical assistant will attach a recording electrode to the skin over your nerve, using a special paste. He or she will then place a stimulating electrode away from the recording electrode, at a known distance.
  6. A mild and brief electrical shock, given through the stimulating electrode, will stimulate your nerve.
  7. You may experience minor discomfort for a few seconds.
  8. The stimulation of the nerve and the response will be displayed on a monitor.

What happens after an NCS?

  1. The paste used to attach the electrodes will be removed from your skin.
  2. After the test, you may return to your previous activities, unless Dr. Tsai advises you differently. You may be instructed to avoid strenuous activities for the rest of the day.

Ask your doctor today to find out whether
EMG / NCT / NCS is right for you