Carpal Tunnel Syndrome - Diagnosis

(Page 4)

• 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 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 thin, 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 whether it adds any valuable diagnostic information. They suggest that its use be limited to unusual cases, or when other tests indicate that the condition is aggressive and may increase the risk for rapid, significant injury.

---

---

Although 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.

Portable electrodiagnostic testing. Portable electronic devices are being evaluated for measuring nerve conductivity. They are relatively quick and easy to use on a large scale in an industrial facility. However, these devices have not been not well studied in clinical trials.

Limitations. Electrodiagnostic studies are not well standardized, and certain conditions can skew the results of either test:

• Obesity can slow the speed of electrical conduction.
• Women and the elderly normally have slower conduction times than younger adult men.

Review Date: 02/17/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).