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Electrodiagnostic Testing: Patient Information

 

What is Electrodiagnostic Testing?

Electrodiagnostic testing involves nerve conduction studies (NCS) and needle electromyography (EMG). Electrodiagnostic medicine is a part of neuromuscular medicine. Specially trained doctors will use tests that look at the electrical impulses between muscles and nerves.  They will use the results from these tests, along with your health history and a physical exam, to diagnose and treat neuromuscular, musculoskeletal, and nervous system disorders. Your doctor has decided that electrodiagnostic testing will help diagnose your condition.

 

Electrodiagnostic testing includes the following:

  • Discussing your health history and medical problems
  • Neurological exam,
  • Nerve Conduction Study (NCS)
  • Needle Electromyography (EMG)

 

Nerve Conduction Studies

A Nerve Conduction Study (NCS) is performed by an EMG Assistant or a doctor. NCS shows how well your body’s electrical signals are traveling to a nerve. This is done by applying surface electrodes. These electrodes transmit small electrical shocks to the nerve and record how the nerve works. These shocks cause a quick, mild, tingling feeling. The doctor may test several nerves.

Being stimulated by electricity can feel like a small electric shock (as a pinch or tingling). Patients almost always handle this test well, with no issues. 

Needle Electromyography (EMG)

Needle electromyography is performed by a doctor. During this test, they will place a very small disposable needle electrode (smaller than the needle used for a blood draw) in one or more of your muscles. The electrode sends the electrical activity of the muscle back through the electrode to the EMG machine. The doctor analyzes the electrical responses from your muscles in real time. They will look at the responses both when the muscle is at rest and when you move it.  

There may be a small amount of pain during this part of the exam. The doctor tests only the muscles necessary to decide what is wrong. 

How long will these tests take?

Everyone is different, but these tests should take about 2 hours. There are no lasting side effects. You also can do your normal activities after the tests.
 

How should I prepare for the tests?

Tell the EMG doctor if you are taking aspirin, blood thinners (like Coumadin®), have a pacemaker, or have hemophilia. (Note: If you have myasthenia gravis, ask your EMG doctor if you should stop any medications before the test.)

 

You can do any of your normal activities, like eating, driving, and exercising, before your tests. Take a bath or shower to remove oil and sweat from your skin. Do not use body lotion on the day of the test.

 

Test Results

At the end of your electrodiagnostic testing, the results of the neurologic exam, the NCS and EMG are all looked at together. These results will be used to diagnose problems with nerves and muscles, and connections between them as well as areas in the brain that control these nerves and muscles.

 

The EMG doctor will discuss your test results with you and send them to your regular doctor as well. After the tests, you need to check with the doctor who sent you to the lab for the next step in your care.

 

Are there any possible risks?

Electrodiagnostic testing involves inserting disposable needle electrodes into skin and muscles then stimulating these muscles with electricity. This testing may cause discomfort or pain. After the tests, the muscle (or several muscles) may feel tender and bruised for a day. Since every patient handles discomfort and pain differently, we cannot predict how much discomfort and/or pain you will have from this test. Most patients describe the discomfort as mild. You may have slight bleeding during or after the test where the needle electrodes were inserted. Therefore, it is vital for you to tell your doctor if you have a bleeding problem, or if you have been taking blood-thinning medication such as Coumadin or Heparin.   

 

NCS and EMG studies are safe for patients with implanted electrical devices such as pacemakers, defibrillators, cochlear implants or spinal cord stimulators. You must let your doctor know if you have an implanted device.  

 

EMG is a low risk procedure. Complications are very rare. 

  

©2023 NYU Langone Health. All rights reserved. Reviewed for health literacy. This information is not intended as a substitute for professional medical care. Always follow your health care provider's instructions.