Electromyography (EMG) Test and Procedure
Overview
Electromyography (EMG) checks muscle health and studies the way nerves and muscles communicate. In this test, specialists look at the electrical activity in muscles using electrodes. There are two main kinds of electrodes: needle electrodes, which go into the muscle, and surface electrodes, which stick to the skin.
EMG focuses on the neuromuscular junction, where nerves connect to muscles. The data shows electrical signals as graphs or sounds. These help specialists spot nerve or muscle issues. A related test, called a nerve conduction study, measures how quickly and strongly signals move between points.
Common Uses for EMG:
- Identifying muscle disorders.
- Detecting nerve disorders.
- Evaluating problems at the neuromuscular junction.
Purpose of the Test
Doctors recommend electromyography (EMG) when people have symptoms that could be linked to nerve or muscle problems. These symptoms can include tingling, numbness, ongoing pain, muscle weakness, or frequent muscle cramps. EMG findings help pinpoint the underlying issue so that proper treatment can begin. Doctors use EMG to check for several conditions:
- Muscle problems, such as muscular dystrophy and polymyositis.
- Diseases at the connection between nerves and muscles, like myasthenia gravis.
- Damage to nerves outside the spinal cord; for example, carpal tunnel syndrome or peripheral neuropathy.
- Motor neuron disorders, such as ALS (amyotrophic lateral sclerosis).
- Nerve root injuries, including from a herniated spinal disk.
Doctors may choose EMG when they want to understand the cause of pain, weakness, muscle wasting, or nerve symptoms that don’t go away. By reviewing the EMG results, they can tell if there is a problem with the muscles, nerves, or the way nerves signal muscles.
Additional Details
Common reasons for this test include conditions such as back pain, diabetic neuropathy, and muscular dystrophy. Other related disorders are brachial plexus injuries, cervical dystonia, Bell’s palsy, Guillain-Barre syndrome, and foot drop. EMG also helps diagnose issues like pinched nerves, herniated disks, and myasthenia gravis.
Possible Side Effects
Electromyography (EMG) generally poses little risk. However, minor risks can occur. The needle electrode can cause bleeding, infection, and nerve damage. Rarely, the needle may let a small amount of air enter the space between the lungs and chest wall, which can lead to a collapsed lung (pneumothorax). Most side effects remain mild and usually get better without medical treatment.
Common Risks Table
| Risk | Description |
|---|---|
| Bleeding | Minor bleeding at the needle site |
| Infection | Slight chance of infection |
| Nerve Damage | Rare but possible nerve injury |
| Pneumothorax | Collapsed lung (very rare complication) |
Getting Ready for the Test
Eating and Medicine Guidelines
Check with your provider about which medications you can take before the test. For example, if you take medications that support nerve and muscle communication (such as those used in conditions like myasthenia gravis), confirm whether you should pause them. Some medicines, like blood thinners, might also require special instructions.
Washing Up Before Your Test
Take a bath or shower close to your appointment time. This removes any oils from your skin. Avoid using lotions, creams, or body oils after washing.
Safety Steps and Notifications
Let your test team know if you have any implants, such as a pacemaker or other electrical devices. Also mention any bleeding disorders, like hemophilia. Sharing these details helps keep you safe during the procedure.
What You Can Expect
Getting Ready for the Test
Before the test begins, you will usually change into a hospital gown and lie down on a table. The neurologist or a technician will place electrodes on your skin, possibly on your arms or legs, depending on where symptoms are. Sometimes, instead of surface electrodes, the doctor may use needle electrodes in different muscles. The spots for electrodes will depend on which areas need to be checked.
What Happens During the Test
During the procedure, small electrical pulses may pass through the surface electrodes. You might feel a quick twitch or mild spasm. If the doctor uses needle electrodes, you could feel brief pain or discomfort when the needle goes into the muscle, but this usually stops when the needle comes out.
The neurologist will watch how your muscles respond both when they are at rest and while you move them lightly. At certain times, the doctor may ask you to tighten or relax a muscle. The doctor might ask you to shift positions to check different muscles or nerves. If you feel discomfort, let the neurologist know. You can take short breaks if needed.
What to Know After the Test Is Done
You might notice slight bruising where the needle electrodes went in. This bruising is usually mild and should go away within a few days. If the area stays bruised or sore, talk to your main doctor for advice. Most people return to their usual activities soon after the procedure.
Findings
After testing, a neurologist reviews all available dataโincluding EMG, nerve conduction studies (NCS), MRI, and X-ray results. They prepare a summary report. The doctor who requested the evaluations covers these findings with the patient during a scheduled visit.
Key Steps
- Neurologist analyzes test results.
- Creates a clear report.
- Requesting doctor explains results to the patient at follow-up.
