EMG

** Please, DO NOT apply any oils, lotions, butter, perfumes or other products to your skin the day of the test. Doing so may interfere with proper application of the electrodes and alter the test results.

What are electromyography (EMG) and nerve conduction studies?

Electromyography (EMG) and nerve conduction studies are tests that measure the electrical activity of muscles and nerves. Nerves send out electrical signals to make your muscles react in certain ways. As your muscles react, they give off these signals, which can then be measured.

  • An EMG test looks at the electrical signals your muscles make when they are at rest and when they are being used.

  • A nerve conduction study measures how fast and how well the body's electrical signals travel down your nerves.

EMG tests and nerve conduction studies can both help find out if you have a disorder of your muscles, nerves, or both. These tests can be done separately, but they are usually done at the same time.

Other names: electrodiagnostic study, EMG test, electromyogram, NCS, nerve conduction velocity, NCV

The Electrodiagnostic evaluation is considered to be an extension of the neurological examination of the peripheral nervous system. At times it can reveal some dysfunction of the nerves and muscles, which was not detected in the physical exam. It is commonly used to diagnose entrapment neuropathies, plexopathies, radiculopathies, neuromuscular junction disorders, myopathies, anterior horn cell disease and can prognosticate functional recovery. It has a role in localization of the site of the lesion, and identifying the pathology.

What are they used for?

EMG and nerve conduction studies are used to help diagnose a variety of muscle and nerve disorders. An EMG test helps find out if muscles are responding the right way to nerve signals. Nerve conduction studies help diagnose nerve damage or disease. When EMG tests and nerve conduction studies are done together, it helps providers tell if your symptoms are caused by a muscle disorder or a nerve problem.

Why do I need an EMG test and a nerve conduction study?

You may need these tests if you have symptoms of a muscle or nerve disorder. These symptoms include:

  • Muscle weakness

  • Tingling or numbness in arms, legs, hands, feet, and/or face

  • Muscle cramps, spasms, and/or twitching

  • Paralysis of any muscles

Will I need to do anything to prepare for these test?

Tell your health care provider if you have a pacemaker or cardiac defibrillator. Special steps will need to be taken before the test if you have one of these devices.

Wear loose, comfortable clothing that allows easy access to the test area or can be easily removed if you need to change into a hospital gown.

Make sure your skin is clean. Don't use lotions, creams, or perfumes for a day or two before the test.

Are there any risks to the tests?

You may feel a little pain or cramping during an EMG test. You may have a tingly feeling, like a mild electric shock, during a nerve conduction study.

What do the results mean?

If your results were not normal, it can indicate a variety of different conditions. Depending on which muscles or nerves are affected, it may mean one of the following:

  • Carpal tunnel syndrome, a condition that affects nerves in the hand and arm. It's usually not serious, but can be painful.

  • Herniated disc, a condition that happens when a part of your spine, called a disc, is damaged. This puts pressure on the spine, causing pain and numbness

  • Guillain-Barré syndrome, an autoimmune disorder that affects the nerves. It can lead to numbness, tingling, and paralysis. Most people recover from the disorder after treatment

  • Myasthenia gravis, a rare disorder that causes muscle fatigue and weakness.

  • Muscular dystrophy, an inherited disease that seriously affects muscle structure and function.

  • Charcot-Marie-Tooth disease, an inherited disorder that causes nerve damage, mostly in the arms and legs.

  • Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. This is a progressive, ultimately fatal, disorder that attacks nerve cells in your brain and spinal cord. It affects all the muscles you use to move, speak, eat, and breathe.