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What Is an Electrodiagnostic Study?

To treat and diagnose neuromuscular disorders, many patients will have a type of testing called an electrodiagnostic study.

An electrodiagnostic study has two parts: 

  1. Nerve Conduction Study (NCS)
  2. Electromyography (EMG)

What Does a Nerve Conduction Study (NCS) Show?

Nerve conduction studies show how well the body’s electrical signals travel down your nerves. During a nerve conduction study test, providers apply small electrical shocks to your nerve and record how your nerve works.

These shocks cause a quick, mild tingling feeling that feels like a static or “carpet” shock. The doctor or technician usually tests several nerves.

What Happens During a Needle Electromyography (EMG)?

For this test, your doctor will insert a small, thin needle (about the size of an acupuncture needle) into several of your muscles to see if there are any problems. Needles are used once for each patient and are then thrown away after the test. 

You may have a small amount of pain or cramping during this part of the examination. Your doctor will only test the muscles that are necessary to decide what is wrong. 

During your EMG test, your doctor will be able to hear and see how your muscles and nerves are working by looking at the electrical signals your muscles make. Your doctor will then use this information to figure out what may be causing your problem.

What Conditions Do EMGs Test For?

Electromyographies are completed to diagnose the following conditions (which include but are not limited to): 

  • neuropathy,
  • carpal tunnel syndrome,
  • ulnar neuropathy,
  • radial nerve injuries,
  • brachial plexus injuries,
  • cervical radiculopathy,
  • lumbar radiculopathy,
  • CIDO (Chronic Inflammatory Demyelinating Polyradiculoneuropathy),
  • AIDP (Acute Inflammatory Demyelinating Polyradiculoneurpathy or Guillian Barre Syndrome),
  • facial nerve injuries,
  • peroneal nerve injuries,
  • motor neuron diseases such as ALS,
  • myopathy, and
  • mononeuritis multiplex.

How Long Will These Tests Take?

The tests usually take 20 to 90 minutes. Before your test, you can do any of your normal activities, including:

  • eating,
  • driving,
  • and exercising.

You also can do your normal activities after the tests. There are no lasting side effects.

How Should I Prepare for the Test?

Tell your EMG care team if you are:

  • taking aspirin,
  • taking blood thinners (like Coumadin),
  • have a pacemaker,
  • or have hemophilia

Take a bath or shower to remove oil from your skin. Do not use body lotion on the day of the test.

If you are being evaluated for myasthenia gravis and are currently taking mestinon or pyridostigmine, ask your physician if it is safe for you to not take this medication on the day of your test.

When Will I Know My Test Results?

After your test is complete, your provider will briefly discuss your test results with you. Your doctor will then send your test results to your referring doctor right away. After your exam, check with the doctor who sent you to the lab to find out the next step in your care.