Testing for Carpal Tunnel Syndrome
Many people suffer from the painful symptoms, numbness, and tingling of carpal tunnel syndrome (CTS). Diagnosing the problem isn't always easy. There isn't one simple test that can be done to diagnose CTS.

In this article, various tests used to diagnose CTS are reviewed. The pros and cons of each test are discussed. These include nerve conduction tests, Semmes Weinstein monofilament tests, and somatosensory evoked potentials (SSEP). Imaging studies such as ultrasound or MRI can also be helpful.

In CTS, the median nerve to the wrist and hand is compressed most often. But in some patients, testing shows changes in the other nerves in the forearm and wrist. And sometimes the tests are normal until major damage is done to the median nerve.

Doctors rely most often on clinical tests. These are referred to as provocative maneuvers. The patient's hand and wrist are placed in a position that puts pressure on the nerve. In a positive test, the position brings on the symptoms.

Experts aren't even sure yet what causes CTS. The risk factors are well known. For example, obesity, diabetes, aging, and pregnancy increase the risk of CTS. But how do these things actually cause CTS? Some studies show increased pressure inside the canal where the nerve passes. Others suggest reduced blood flow to the nerve causes damage.

We are still far from finding the gold standard for diagnosing CTS. It may be that different tests will work for different patients based on the underlying cause(s) of the condition. For now, CTS is a clinical diagnosis based on the presentation of classic symptoms. The authors suggest this is unlikely to change until the exact mechanism of CTS is found.
Aaron M. Freilich and A. Bobby Chhabra, M.D. Diagnosis and Pathophysiology of Carpal Tunnel Syndrome. In Clinical Opinion in Orthopaedics. July 2007. Vol. 18. No. 4. Pp. 347-351.