Evidence For the Use of Steroid Injection in Carpal Tunnel Syndrome
What's the benefit of steroid injections for carpal tunnel syndrome? Is a single injection enough? If one works, would the patient benefit by another one? Does the injection improve the function of the nerve? These are the questions Dr. M. I. Boyer of the Washington University in St. Louis researched and reported on in this study.

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, a medical condition known as nerve entrapment. Any condition that decreases the size of the carpal tunnel or enlarges the tissues inside the tunnel can produce the symptoms of CTS.

Symptoms can include gradual tingling and numbness in the areas supplied by the median nerve. This is typically followed by dull, vague pain where the nerve gives sensation in the hand. The hand may begin to feel like it's asleep. Patients often report waking up at night and shaking the hands to wake them up.

Studies so far have not shown a benefit to the nerve after steroid injection treatment in terms of improved function. Although the injection may give the patient relief from the symptoms, it doesn't affect nerve function any more or any better than other treatment approaches.

And more is not necessarily better. In other words, increasing the dose (amount of steroid used or number of injections given) doesn't reduce the pain, numbness, or tingling any faster or better than a single dose. Likewise, injecting a specific area (above or below the wrist crease) doesn't provide different results.

Whether or not a particular type of steroid works best (e.g., methylprednisolone acetate, betamethasone, triamcinolone acetonide, dexamethasone) remains under investigation. The biggest predictor of results with steroid injection is the outcome of electrodiagnostic tests. Electrical impulses through the nerve are evaluated. Slow or absent messages from the nerve to the muscles are an indication of damage to the median nerve.

Electrodiagnostic tests showing that the median nerve is damaged are an indicator that surgery is advised. When there are positive objective findings on testing, steroid injection may provide symptom relief, but it's only temporary. On the other hand, patients who have normal electrodiagnostic tests are actually more likely to benefit from a steroid injection.

Patients with altered sensation and slow nerve impulses have the poorest response to injection. And they are more likely to have a relapse with return of symptoms. Once the electrodiagnostic tests show nerve impairment, chances are that conservative care with steroid injection won't help.

For now, it looks like a single steroid injection is safe and offers fast relief from symptoms. Results are short-term and the symptoms may come back if there is damage to the nerve. Steroid injection is one option for patients who want to avoid having surgery for as long as possible or for those who need immediate symptom relief.

There are still many factors around carpal tunnel syndrome left to study. The author points out that some studies show that symptoms go away naturally (without treatment) in one out of every three patients. Scientists need to find out how to predict which patients will get better on their own, which patients will benefit from conservative care, and who should just go ahead and have the surgery right away.

For now, anyone with normal electrodiagnostic test results should start with antiinflammatory drugs, splinting, and/or physical therapy. A steroid injection is advised if these conservative measures don't help, or if the patient needs fast relief of symptoms.
Martin I. Boyer, MD. Corticosteroid Injection for Carpal Tunnel Syndrome. In The Journal of Hand Surgery. October 2008. Vol. 33-A. No. 8. Pp. 1414-1416.