Electromyography (EMG) and Nerve Conduction Velocity (NCV)

All of our nerves and muscles use electricity to get things done. In fact, you can think of your body as a machine with incredibly intricate wiring. To be sure, it’s more complex than any wiring system that an electrician would design. But—just as an electrician would do if some part of a machine wasn’t working as it usually does—a doctor can test how your child’s nerves and muscles are conducting electricity.

Nerve conduction studies (NCS) and electromyography (EMG) are specific tests that help your child’s doctor see how his nerves and muscles are working. NCS measures how electrical signals travel through the nerves, and EMG records the signals moving through the muscles. Together, these tests are often called “EMG testing.”

The nerves tested in nerve conduction studies are called “peripheral nerves.” They’re the nerves outside of the brain and spinal cord carrying messages throughout your child’s body. They allow your child to receive sensory information (like how an object feels when he touches it) and control his muscles.

EMG testing can help your child’s doctor diagnose many different neuromuscular and muscular disorders. It’s also used to check on how your child’s nerves and muscles are functioning later on, after he’s already been diagnosed and gotten treatment.

Here is some basic information about how the test works:

• In nerve conduction studies (NCS), a doctor places three electrodes (stickers) on the part of your child’s body being tested, then sends small amounts of electrical current through your child’s nerves. These feel like static electricity that you experience in the winter. This part of the test usually takes 30 to 45 minutes.
• In electromyography (EMG), a doctor places a very thin needle electrode (similar in size to the needles used in acupuncture) into one or more of your child’s muscles, and then takes recordings of the electrical activity in the muscle. This part of the test usually takes no more than 15 minutes.
• EMG is sometimes uncomfortable, but children are usually able to tolerate it well.
• On rare occasions, the test is done with general anesthesia.
• Most children are able to go back to school the same day.

How Children’s Hospital Boston approaches EMG studies

Our EMG laboratory is just for kids. That means that all of our physicians and technologists are experienced in working with children, making them as comfortable as possible and putting them at ease during what can otherwise seem like a scary test. The lab is staffed by neurologists in our Neuromuscular Program.

Founded it 1979, our EMG lab continues to offer the most sophisticated testing possible for our young patients. One of our special capabilities is single-fiber EMG, a specific test that’s useful for diagnosing myasthenia gravis but that’s rarely performed by pediatric specialists.

Nerve conduction studies and electromyography (EMG studies): Reviewed by Peter Kang, MD

© Children’s Hospital Boston, 2010