Carpal Tunnel Syndrome - Diagnosis

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.
Anxiety can slow the speed.
Women and the elderly normally have slower conduction times than younger adult men.
Temperature also affects nerve conduction speed. Room temperature should be strictly controlled and doctors should take into consideration any climatic conditions that might affect outcome.

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Ruling out other causes is extremely important in order to avoid unnecessary surgery for CTS. Modifications and improvements of these tests are continually being made.

Note: People with abnormal results but who have no CTS symptoms are at no higher risk for CTS than those with normal results and no symptoms.

A diagnosis of carpal tunnel syndrome may follow testing the affected hand for numbness, tingling, weakness and/or pain in specific areas. Muscle and nerve conduction tests may also help affirm or rule out carpal tunnel syndrome.

Imaging Techniques

Ultrasound. Ultrasound imaging, a relatively inexpensive technique that uses sound waves, is showing promise. Studies indicate that it can identify up to 85% of CTS cases, and some suggest it is as effective as electrodiagnostic tests. It may be effective for ruling out other causes of hand pain, such as tendon injuries, tenosynovitis (swelling of the tendon lining), cysts, and blood clots in the median artery (a rare complication that can cause the sudden onset of CTS symptoms). However, results are mixed on its accuracy. Newer color Doppler ultrasound and other technological advances are improving the results achieved with this technique. A 2005 study comparing high-resolution ultrasonography with electromyography found that ultrasonography may be helpful for estimating the symptom severity and problems with nerve conduction.

MRI. Magnetic resonance imaging (MRI), an advanced imaging technique, is being adapted to distinguish weak nerve signals from surrounding tissue, so that eventually it may be able to precisely diagnose CTS. However, studies in 2002 note that it requires special expertise, has limited diagnostic accuracy, and is still too expensive at present for routine use. Currently, MRI is accurate in diagnosing carpal tunnel syndrome about 80% of the time, compared to about 85% using electrodiagnostic tests, which remains the gold standard. MRI may be most effective for detecting any internal injuries, tumors, or arthritis or joint damage that might be causing the problem. It may also be valuable in selecting surgical candidates when electrodiagnostic tests produce unusual results or indicate more severe disease than expected or for evaluating patients if surgery fails to bring relief.