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Merck Manual

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Quick Facts

Electromyography (EMG) and Nerve Conduction Studies


The Manual's Editorial Staff

Last full review/revision Sep 2020| Content last modified Sep 2020
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Your brain tells your muscles what to do by sending electrical signals to them. The signals travel down your spinal cord and then through different nerves to your muscles.

What are EMG and nerve conduction studies?

EMG and nerve conduction studies are tests to see if you have muscle weakness or loss of feeling from an injury to your spinal cord, muscles, or nerves.

  • To do an EMG, doctors insert small needles into a muscle to record your muscle’s electrical activity when it’s resting and when it’s active

  • To do nerve conduction studies, doctors use skin sensors or needles to send small electric shocks through different nerves to see how well your nerves work

Why would I need an EMG or nerve conduction study?

Doctors may do an EMG, nerve conduction study, or both if you have symptoms like tingling or muscle weakness. These symptoms can be caused by many problems in different parts of your body. An EMG or nerve conduction study can help your doctor tell if your symptoms are caused by nerve or muscle problems such as:

What happens during an EMG or nerve conduction study?

During an EMG:

  • Doctors put needles into your muscle

  • The needles are connected by wires to a machine that records your muscle's electrical activity while you move it and relax it

During a nerve conduction study:

  • Doctors put a sticky sensor on your skin over the nerve they are testing

  • They stimulate another part of the nerve with a small electric shock

  • A machine measures how fast the electrical signal travels down the nerve

What are the problems with an EMG or nerve conduction study?

The needles and electric shocks can be uncomfortable or hurt. You may have some bruises afterward.

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