What Is Electromyography (EMG)?

An electromyography (EMG) test measures electrical activity within the muscles. Although it can be done independently, an EMG is usually performed alongside nerve conduction studies, which measure how electrical signals within the body travel down the nerves. EMG and nerve conduction studies may also be called electrodiagnostic studies, EMG tests, electromyograms, or nerve conduction velocity tests.

Specific symptoms, like constant muscle weakness or tingling in the hands or feet, should be evaluated by a healthcare provider. Depending on your medical history and physical assessment findings, a qualified healthcare provider might order an EMG and nerve conduction study to identify potential causes for the symptoms.

This article will review what you can expect during an electromyography test.

What Is the Purpose of Electromyography?

If you are experiencing any of the following symptoms, your healthcare provider may recommend an EMG test:

• Muscle weakness
• Tingling or numbness in extremities, like arms, hands, legs, or feet
• Tingling or numbness in the face
• Muscle cramps, spasms, or twitching
• Muscle paralysis

The EMG test helps healthcare providers identify whether you have a problem with how your muscles respond to nerve impulses. EMGs and nerve conduction studies can help healthcare providers determine whether there is nerve damage or nerve disease.

It can be challenging to determine if the symptoms are caused by electrical activity in a a nerve vs. a muscle, which is why these two tests are often done together.

Risks and Contraindications

Before scheduling an EMG and nerve conduction study, inform your healthcare provider if you have a pacemaker or cardiac defibrillator. You can still undergo testing; however, a provider will take extra steps to protect you (and the device) from injury or damage.

Other considerations to discuss with your provider before EMG testing include the following:

• Illness: It is challenging for healthcare providers to accurately assess muscle and nerve readings when you are ill. Also, to minimize the spread of your illness, it is better to reschedule EMG testing when the illness is absent.
• Risk of infection: Certain medications, like long-term steroids, or disease conditions, like cellulitis, increase the risk of infection.
• Blood-thinning medications: The risk of bruising or slight bleeding under the skin increases when taking blood thinners. Informing the healthcare professional before testing so they can consider different techniques to prevent complications.

Before the Test

A healthcare provider will do one or more of the following before ordering an EMG or nerve conduction test:

• Obtain your medical history
• Perform a physical examination
• Evaluate your heart's electrical system (electrophysiology study)

Once EMG tests or nerve conduction studies are ordered, there are other considerations to be aware of:

• EMG tests and nerve conduction studies are typically covered by insurance; however, it is important to verify coverage as well as any co-payments required.
• EMG tests can cause anxiety; when placed correctly on the muscles, the electrodes can be uncomfortable.
• If your provider prescribes you pain or anxiety medications, arrange for assistance with transportation home after the procedure.

Day of Testing

There is no special preparation for EMG testing; you can exercise, eat, drink, and do other typical daily activities. On the day of your test, wear loose-fitting clothing. Depending on the area being tested, you might be asked to change into a hospital gown. Ensure your skin is clean and free of lotions, creams, and perfumes since they can interfere with EMG testing.

Bring an official form of identification, such as a driver's license or passport, and if you have health insurance, bring your insurance card to ensure a smooth check-in.

Location

EMGs are done by a physician trained in needle EMG testing. EMG testing specialists often include neurologists and physiatrists, although any residency-trained physician can seek specialty training with EMG testing.

A trained technologist can do nerve conduction studies with an appropriately trained physician supervising the testing.

EMGs are typically done in a location where an EMG machine can be installed. Many healthcare providers have EMG testing available in their office but also may use a shared outpatient space at a larger healthcare organization, like a hospital.

During the Test

Testing will occur in an area with a table or bed to recline or lie on and usually takes between 20 and 90 minutes, depending on how many muscles are tested. Typical next steps include:

• Cleaning the skin: A qualified healthcare provider will clean the test site on your skin and apply an electrode to the muscle.
• Connecting electrodes: The electrode is connected to a machine, which sends a mild electrical current to the muscle to assess for any muscle dysfunction and record muscle activity while your muscle is relaxed.
• Engaging your muscle: You'll be asked to brace or tighten your muscle slowly, and the machine will record muscle activity when the muscle is active.

The machine will record your muscle activity as wavy and spiky lines. Some devices record muscle activity, so you may hear "popping" sounds made by active and resting muscles.

When the EMG test is complete, the healthcare provider removes the electrodes, which can cause soreness or bruising. This will fade within a few days. There are no long-term side effects associated with EMG testing.

After the Test

Depending on symptoms and EMG test results, a healthcare provider may recommend additional testing, including:

• Neuromuscular ultrasound: Using an ultrasound machine, an appropriately trained healthcare provider can see tendon or joint problems that could be causing symptoms.
• Muscle biopsy: A muscle biopsy involves removing a small piece of muscle via a hollow needle. The muscle sample is then sent to a laboratory to determine the presence of specific proteins associated with neuromuscular disorders and diseases.
• Laboratory testing: Some neuromuscular diseases and disorders are genetically inherited and can be identified through laboratory testing.

Managing Side Effects

Side effects from EMG testing include soreness or bruising where the electrodes were inserted into the muscles. These symptoms generally fade within a few days.

Although there are no long-term side effects associated with EMG testing, if any of these symptoms occur, discuss them with your healthcare provider:

• Soreness or pain that does not fade away in a few days
• Bruising that worsens or spreads
• Any signs of infection, such as reddened skin or drainage from the electrode insertion sites

Interpreting Results

If the healthcare provider performing the test does not review your results with you immediately, the provider will send the results to the ordering provider. In that situation, you may need to schedule a follow-up appointment with the ordering healthcare provider to review EMG test results.

EMG testing can indicate different neuromuscular diseases or disorders, such as:

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

Your healthcare provider will guide you toward further testing and specialist consultations based on your test results and symptoms.

Follow-Up

The American Association of Neuromuscular and Electrodiagnostic Medicine recommends testing only a minimal number of muscles needed to identify the clinical concern or determine a diagnosis. There is no standard recommendation for follow-up testing. Your provider will make recommendations based on your health history, symptoms, and progression of any related underlying diseases.