Why won't the electrical tests work for me for carpal tunnel?

Q: When I went to see a hand surgeon for my carpal tunnel symptoms, I had to have nerve testing before they would do surgery. I guess the tests showed I really did have a carpal tunnel problem because I passed the test and had the surgery. Now three years later, the same wrist is acting up again. I saw the same surgeon yesterday again. This time I was told the electrical tests won't work for me. Why not?

A: Carpal tunnel syndrome (CTS) is a fairly common problem in adults, affecting people of all ages from young to old. Symptoms of wrist and hand pain, weakness, numbness, and/or tingling can be annoying and even very disabling.

Many people are helped by conservative means with antiinflammatory medications, splinting, and hand therapy. But for those whose symptoms just don't go away, surgery is needed to release the soft tissues that cross over the carpal tunnel and put pressure on the nerve.

In up to 20 per cent of those patients, the symptoms are unchanged or only slightly less. A little more hand therapy combined with antiinflammatory meds and special exercises and the problem is solved -- for most of those patients. But in about five per cent of all cases, a second revision surgery is required.

Studies have found that whereas those electrodiagnostic tests are very useful to confirm the diagnosis of nerve compression, they are less helpful after surgery. The tests include nerve conduction velocity (measuring speed of signals along the nerve) and electromyography (checking to see if the nerve signals are reaching the muscles).

As your surgeon has pointed out, these tests are not useful with patients who have recurrent carpal tunnel syndrome. Studies show electrical changes can continue even after a successful primary carpal tunnel release. So the tests don't offer additional useful or valuable information when facing the decision of a second surgery.

There has been some suggestion of trying steroid injection into the carpal tunnel before doing a second surgery. The hope is to find a way to predict who will have a successful response to surgery before doing the procedure. At least one study showed the steroid injection can aid in screening patients for surgery. But by itself, it isn't completely reliable. The surgeon's evaluation combined with a test injection offers more valuable predictive information and may be used instead of repeating electrodiagnostic tests.

Reference: John D. Beck, MD, et al. Predicting the Outcome of Revision Carpal Tunnel Release. In The Journal of Hand Surgery. February 2012. Vol. 37A. No. 2. Pp. 282-287.