Electromyography (EMG) for Carpal Tunnel Syndrome
Carpal tunnel syndrome (CTS) is a common neurological disorder that occurs when the median nerve, which runs from your forearm into the palm of your hand, becomes pressed or squeezed at the wrist. This can happen when the carpal tunnel, a narrow passageway of ligament and bones at the base of the hand, becomes narrowed or compressed.
The median nerve is responsible for providing feeling to the thumb, index finger, middle finger, and part of the ring finger. It also controls some small muscles at the base of the thumb. When the median nerve is compressed, it can cause a variety of symptoms, including:
- Numbness in the hand and fingers
- Weakness in the hand and wrist
- Pain in the hand and wrist
- Swelling in the fingers
Diagnosing CTS usually involves a combination of clinical evaluation and tests to measure how well the median nerve is functioning. Nerves send out electrical signals to control muscle movement. One test used to the help diagnose CTS is electromyography (EMG). EMG checks your muscles response to electrical signals and how much electrical activity is produced when the muscle is used. Normally, a resting muscle does not show electrical activity. A nerve conduction study is usually also done at the same time as the EMG test.
The doctor will take a medical and medication history before a electromyography test. The doctor will want to know if you have a heart condition or are taking blood thinners and may provide special instructions about your medications.
EMG tests may be conducted in a doctor’s office or clinic. The entire test may take about an hour. For the EMG:
- Wear comfortable clothing that allows the doctor easy access to your arm.
- Be sure your skin is clean. Don’t use lotions, creams or perfume on your arm because these may change the results of the test.
During the electromyography test:
- The doctor inserts a small needle into the muscles to be tested. You may feel a little pain or discomfort when the needle is inserted. The needle has a small device that records the electrical activity of the muscle.
- The doctor will ask you to relax your muscle and to move your muscle in specific ways (for example, flex your wrist). This allows the test to record how much electrical activity is happening. Each test of a muscle takes a couple of minutes.
- If more than one muscle is being tested, the doctor will remove the needle and repeat the needle insertion and muscle testing for other muscles.
- The doctor will analyze the recording to look for patterns that indicate a possible nerve conduction issue.
There usually are no activity limitations after an electromyography test. The muscles tested may feel a little sore for a few days. There also may be slight bruising where the needles were inserted.
The doctor will also let you know when to restart medications if you were asked to temporarily stop taking a medication.
Contact the doctor if:
- Bruising or bleeding at the needle insertion site doesn’t get better
- The area of the arm tested is painful beyond mild soreness
- The area of the arm tested become red, warm or swollen
- You develop a fever after the test