Electromyogram (EMG)
What is an electromyogram (EMG)?
An electromyogram (EMG) is a test that measures muscle response or electrical activity in response to a nerve’s stimulation of the muscle. It is used to help determine muscle conditions that may be causing muscle weakness, including muscular dystrophy and nerve disorders. A nerve conduction study (NCS) measures how fast an electrical impulse moves through your nerve. NCS can identify nerve damage.
What are the benefits?
An EMG test may help diagnose or rule out a number of conditions such as:
- Muscle disorders
- Diseases affecting the connection between the nerve and the muscle
- Disorders that affect the motor neurons in the spinal cord
- Disorders that affect nerve roots
How do I prepare my child for the test?
Your child’s doctor may recommend taking a bath or shower before the test to help remove oils from the skin. After washing, do not apply lotions or creams before the test.
How long does the test take?
An EMG takes about 1 to 2 hours.
How is if performed?
Your child will be asked to lie down on an exam table or to sit in a reclined chair. Your child’s doctor may ask him or her to move into different positions during the test.
There are usually 2 parts to an EMG procedure: the nerve conduction study (NCS) and the needle EMG. A nerve conduction study assesses the function of the nerves that are responsible for muscle movement, while a needle EMG assesses the activity of the muscles.
The nerve conduction study is the first part of the procedure. It involves placing small sensors called surface electrodes on the skin to measure how fast this signal travels through a nerve.
During the NCS, 2 sets of electrodes are placed at distances over the nerve. One set releases a very small electrical signal while the second set records it.
The second part of the procedure, known as needle EMG, also uses sensors to evaluate electrical signals. These sensors are very thin needles that are inserted directly into the muscle to evaluate the function of the muscle at rest and during movement.
These electrodes will be removed after the test is over.
What are the risks?
An EMG is a very low-risk test. The needle EMG may be a little uncomfortable for your child. Your child may feel sore in the area that was tested. The soreness may last for a few days and can be relieved with an over-the-counter pain reliever, such as acetaminophen.
When will I get the results?
Results from your child’s EMG test will be shared with you at your child’s next appointment or earlier if there are any concerns.