Electromyogram: What EMG Is For and What to Expect

Medically Reviewed By Heidi Moawad, M.D.
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An electromyogram (EMG) evaluates electrical activity within the nerves and muscles. An EMG may help diagnose muscle weakness, muscular dystrophy, and other neuromuscular conditions. An EMG test involves inserting tiny needles into the muscles to record electrical activity. Your doctor may order an EMG alongside a nerve conduction study. A nerve conduction study can also be useful in diagnosing conditions affecting your muscles or nerves.

This article explains when you might need an EMG and what conditions it can assist in diagnosing. This article also looks at what to expect before, during, and after an EMG.

When do I need an EMG?

A person is getting an EMG.
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Your doctor may request an EMG if you have symptoms that suggest a nerve or muscle condition. Symptoms can include:

  • muscle weakness
  • tingling or numbness, particularly in your:
    • hands
    • arms
    • feet
    • legs
    • face
  • muscle spasms, cramps, or twitching
  • muscle paralysis

What is an EMG test used to diagnose?

An EMG can help doctors diagnose conditions that affect your muscles or nerves. Conditions that an EMG can help to detect include:

  • amyotrophic lateral sclerosis, also known as ALS or Lou Gehrig’s disease, a severe neuromuscular disease that causes muscle weakness and disability
  • carpal tunnel syndrome, which occurs as a result of compression of the median nerve in the wrist
  • Charcot-Marie-Tooth disease, a neurological disorder causing damage and weakness to nerves in the arms and legs
  • Guillain-Barré syndrome, an autoimmune disorder that can cause tingling, numbness, and paralysis
  • herniated disc, which happens when there is severe damage or injury to a disc in the spine
  • muscular dystrophy, an inherited disorder that causes a progressive loss of muscle tissue and muscle weakness
  • myasthenia gravis, a rare autoimmune neuromuscular disorder that causes muscle weakness and fatigue
  • polymyositis, a type of muscle inflammation that causes decreased muscle power
  • sciatica, inflammation of the sciatic nerve that causes burning or shooting pain running from the buttocks down the back of the leg

Learn more about conditions an EMG can help to diagnose.

Who performs an EMG?

A neurologist or pediatric neurologist performs an EMG. A neurologist specializes in diagnosing and treating diseases of the brain and nervous system.

A technologist may assist your neurologist during the procedure.

Learn more about the role of the neurologist.

How do I prepare for an EMG?

Your doctor will advise you on necessary preparation for your EMG. In particular, you may need to take certain steps if you have a pacemaker or cardiac defibrillator.

Some medications, such as muscle relaxants and some pain relief medications, can interfere with EMG results. Tell your doctor beforehand about any medications you currently take. They will advise on whether you need to stop taking them before the test.

Your doctor may ask that you refrain from using lotions or oils on your skin for 1–2 days before the test.

Your doctor may also specify that you wear loose, comfortable clothing. They will tell you if you need to wear a hospital gown or if you can wear your own clothing.

You can also prepare for an EMG by asking your doctor any questions you may have. Being as informed as possible about what to expect can help you to feel more at ease.

What happens during an EMG?

Your EMG will be performed in a hospital or outpatient setting.

During the test you will either sit or lie down. Your neurologist will clean the needle insertion points on your skin with an antiseptic cleanser. Then they will insert the needles containing electrodes into your skin.

The number and placement location of the needles depend on the condition that your doctor is testing. You may feel a pinch or discomfort as each needle goes into your skin.

You will relax and contract certain muscles while a special machine records the electrical activity of the muscles. You may hear sounds when you contract your muscles if your doctor is using an audio device during the procedure.

The test typically takes 30–60 minutes.

What happens after an EMG?

You should be able to carry out your usual activities after an EMG. You should not experience any lasting side effects.

However, it is important to let your neurologist know if you feel any pain or discomfort afterward.

What do my EMG results mean?

After the EMG, your neurologist will evaluate your EMG test results. They will send a report to your doctor who will discuss the results with you.

Your doctor will view these test results in conjunction with your neurological examination.

Are there any risks of an EMG?

The risks of an EMG are generally minor, with temporary side effects. 

You may experience pain or cramping during the test. Your muscles may also feel sore or tender afterward, but you should not experience any lasting effects.

Contact your doctor if you do experience ongoing pain or discomfort after your test.

When should I contact a doctor?

Contact your doctor if you are booked for an EMG and you have questions about the test. They will provide you with information about what to expect. This can help you feel more prepared.

Also contact your doctor if you experience pain or discomfort after your EMG. Your neurologist will be able to advise on what you can expect afterward. You should not experience any lasting effects after the EMG.

What is a nerve conduction study?

A nerve conduction study is another test doctors order to assist with diagnosing conditions that affect muscles and nerves. This study measures how quickly electrical signals travel down your nerves.

Your doctor may order a nerve conduction study either alongside or instead of an EMG.

Learn more about nerve conduction study.

Other frequently asked questions

Here are questions people also ask about EMGs.

Is an EMG test painful?

You may feel some pain or discomfort during an EMG test, particularly when your neurologist inserts the needles. However, this should only be temporary.

What happens if an EMG is abnormal?

Your doctor will discuss the findings of your EMG with you. If the EMG test indicates that you may have a condition affecting your nerves or muscles, your doctor may order other tests to assist with reaching an accurate diagnosis. They may also be able to discuss your treatment options at this stage.

What are the signs of nerve damage?

Signs of nerve damage can include twitching, numbness, and weakness. Contact your doctor if you have symptoms of nerve damage. They may order various tests, including EMG.

Summary

EMG is a test designed to measure the electrical activity in your muscles and nerves. Your doctor may order the test if you experience symptoms of nerve damage or muscle weakness.

EMG can assist with diagnosing a range of conditions affecting the nerves and muscles. If the EMG does show signs of damage to the nerves or muscles, your doctor may order other tests to assist with reaching an accurate diagnosis.

Contact your doctor if you are booked for an EMG and have concerns. They will answer your questions and provide you with information about what to expect.

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Medical Reviewer: Heidi Moawad, M.D.
Last Review Date: 2022 Oct 27
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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