What is an Electromyography (EMG) Test?

Frequently Asked Questions:

What is Electromyography (EMG) Test used for?

Electromyography (EMG) and nerve conduction studies diagnose muscle and nerve disorders. EMG tests help determine whether muscles are responding to nerve signals. Nerve conduction studies help diagnose nerve damage. Combining EMG tests and nerve conduction studies helps doctors determine whether your symptoms are related to a muscle disorder or a nerve issue.

Understanding the test results of Electromyography (EMG) Test

Results that are not normal can indicate a variety of conditions. It may mean one of the following based on the muscles or nerves affected:

• Dystrophies or polymyositis of the muscles
• Nerve root disorders, such as a herniated disk in the spine
• Neuromuscular diseases, such as myasthenia gravis
• Nervous system disorders outside the spinal cord (peripheral nerves), such as carpal tunnel syndrome or peripheral neuropathy
• Motor neuron disorders affecting the brain or spinal cord, such as amyotrophic lateral sclerosis or polio

Why do I need an Electromyography (EMG) Test?

Doctors recommend an electromyography (EMG) test for muscle or nerve disorder symptoms. The symptoms include:

• Weakness of the muscles
• Muscle paralysis of any kind
• Twitching, cramps, or muscle spasms
• Numbness or tingling in your arms, legs, hands, feet, or face

What happens during Electromyography (EMG) Test?

• You will sit or lie down
• A provider will clean the skin over the muscle being tested
• A needle electrode will be inserted into the muscle by your provider
• A needle electrode is a special wire through which a mild electrical current flows
• It may cause some discomfort when it is inserted
• During rest, the machine will record the muscle activity
• After that, you will be asked to slowly and steadily tighten (contract) the muscle, and a recording will be taken
• You can move the electrode to record activity in different muscles
• Video screens are used to display electrical activity
• The activity appears as wavy and spiky lines
• An audio speaker may also be used to playback the activity
• Your muscles may pop when you contract them

Is an EMG test painful?

An electromyography test may cause some pain or cramping. You may feel tingly during the EMG test, like receiving a mild electric shock.

What diseases can EMG diagnose?

• Herniated disc
• Myasthenia gravis
• Muscular dystrophy
• Carpal tunnel syndrome
• Guillain-Barré syndrome
• Charcot-Marie-Tooth disease
• Amyotrophic lateral sclerosis (ALS)

What are the signs of nerve damage?

• Hands and feet numb or tingling
• Dropping objects you hold regularly
• Discomfort in your hands, arms, legs, or feet
• An electrical shock-like buzzing sensation
• Weak muscles, especially in the arms or legs
• You feel like you are wearing a tight glove or sock

What should you not do before an EMG?

You should inform your doctor if you use any over-the-counter or prescription medications, or have a pacemaker or implantable defibrillator. 

Before having an EMG, take  care of the following:

• Don't apply lotion or cream after washing
• Take a bath or a shower to remove any oils from your skin
• Smoking should be avoided for at least three hours before the procedure
• Don't wear clothing that obstructs your doctor's view of the area being evaluated

Can an EMG detect multiple sclerosis?

Electromyography (EMG) test measures the response of muscles to stimulation and is used to assess their health. When a patient has unexplained muscle weakness, doctors can use this test to diagnose multiple sclerosis and other conditions when a patient has unexplained muscle weakness.

Can EMG detect fibromyalgia?

In fibromyalgia, malfunctioning muscle contractions were associated with a specific EMG pattern. For this reason, maximal voluntary muscle contraction tests may not be enough to measure function in people with fibromyalgia.

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