Test to confirm Carpal Tunnel Syndrome
Electrodiagnostic tests analyze the electric waves of nerves and muscles. These tests can help detect median nerve compression in the carpal tunnel.
Electrodiagnostic tests are the best methods for confirming a diagnosis of CTS at this time. Doctors who perform these tests should be certified by the American Board of Electrodiagnostic Medicine, which uses rigorous standards in qualifying doctors. Specific electrodiagnostic tests, called nerve conduction studies and electromyography, are the most common ones performed: Nerve conduction tests can also detect causes of symptoms that mimic CTS but are caused by other problems, such as pinched nerves in the neck or elbow, or thoracic outlet syndrome.
- Nerve Conduction Studies. To perform nerve conduction studies, surface electrodes are first fastened to the hand and wrist. Small electric shocks are then applied to the nerves in the fingers, wrist, and forearm to measure how fast a signal travels through the nerves that control movement and sensation. Nerve conduction tests are fairly accurate when done on patients with more clear-cut symptoms of carpal tunnel syndrome. They are less accurate in identifying mild CTS, however. Patients should be sure their practitioners perform tests that compare a number of internal responses, not just routine testing that records only the responses of muscles located in the palm at the base of the thumb. They should also make sure the tests measure responses on the second or third fingers.
- Electromyography. To perform electromyography, a fine, sterile, wire electrode is inserted briefly into a muscle, and the electrical activity is displayed on a viewing screen. Electromyography can be painful and is less accurate than nerve conduction. Some experts question, in fact, whether it adds any valuable diagnostic information. They suggest it be limited to unusual cases or when other tests indicate that the condition is aggressive and may increase the risk for rapid, significant injury.
While electrodiagnostic studies are frequently done to confirm the diagnosis of carpal tunnel syndrome in patients with classic symptoms, they are also performed on patients with symptoms that do not point to carpal tunnel syndrome as clearly. Doctors must interpret test results in these patients more carefully.
