Best Way to Diagnose Carpal Tunnel Syndrome

Dr. Brent Graham at the Toronto Western Hospital (Canada) has been working on finding the best way to diagnose carpal tunnel syndrome (CTS). Currently, there isn’t a clear consensus on the best clinical tests to use in making this diagnosis.

Carpal tunnel syndrome is a common problem affecting the hand and wrist. Symptoms begin when the median nerve gets squeezed inside the carpal tunnel of the wrist. Carpal tunnel syndrome is also known as nerve entrapment or compressive neuropathy. Any condition that decreases the size of the carpal tunnel or enlarges the tissues inside the tunnel can produce the symptoms of carpal tunnel syndrome.

In the past, Dr. Graham tested and validated a new clinical tool called the CTS-6. This instrument is a diagnostic scale for carpal tunnel syndrome. It includes six tests from the history and physical exam to estimate the likelihood that carpal tunnel syndrome is present. The CTS-6 has been tested and validated as a reliable instrument.

Now, in this study, Dr. Graham compared the results of the CTS-6 with electrodiagnostic testing. Electrodiagnostic testing consisted of sensory nerve conduction velocity (NCV). A segment of the median nerve was tested from the wrist to the middle finger.

There were several steps in this study. First, a hand therapist tested all new patients referred to the center for possible upper extremity peripheral nerve problem. The CTS-6 test was used to determine the pre-test chances the patient had carpal tunnel syndrome. Then these same patients were tested using a standard nerve conduction velocity test.

With the CTS-6 scale, each of the six items is given a point value. The six items include 1) numbness in the hand and fingers supplied by the median nerve, 2) muscle atrophy and/or weakness, 3) a positive Phalen test (standard clinical test used to diagnose carpal tunnel syndrome), 4) loss of two-point discrimination (feeling two separate points touched on the skin), 5) numbness at night that wakes the patient up, and 6) a positive Tinel sign (another standard clinical test used to diagnose carpal tunnel syndrome).

A total score of 12 or more suggests a strong probability (80 per cent chance) that the patient has carpal tunnel syndrome. A total score less than five indicates a very small chance (25 per cent) that the patient has carpal tunnel syndrome.

Comparing the results of the CTS-6 test with the results of the nerve conduction velocity test, the authors report the added information from the electrodiagnostic test was not enough to change the diagnosis or warrant the expense. A low probability of carpal tunnel syndrome (judged by the CTS-6) in a patient whose nerve conduction velocity was negative only lowered the chances of the diagnosis being carpal tunnel syndrome. There wasn’t much value added by the electrodiagnostic test — not enough to support the cost and discomfort to the patient.

With the availability of the CTS-6, there is much less need to use electrodiagnostic studies. The goal in making any diagnosis is to do so in the least amount of time,with minimal discomfort to the patient, and at the lowest cost. The right diagnosis is important in planning treatment that will bring the most successful results.

The authors conclude that a plan of care can be established for carpal tunnel patients just using the CTS-6 test. Adding electrodiagnostic tests may be helpful when the CTS-6 results give the patient a 60 to 80 per cent probability of having carpal tunnel syndrome. But for the most part, the value added by electrodiagnostic testing is minimal when the CTS-6 score predicts carpal tunnel syndrome.

The next step in this process is to independently validate the CTS-6 test in a clinical setting. This means some other group(s) of researchers must use the CTS-6 and come up with the same results as the Graham group. This step is necessary before the CTS-6 can be adopted for use in the clinic as a standard diagnostic tool for carpal tunnel syndrome.