Carpal tunnel syndrome: Do corticosteroid injections work?

Corticosteroids injected directly into the wrist can temporarily relieve carpal tunnel syndrome symptoms. This local injection has a longer effect than taking corticosteroid tablets or injecting corticosteroids into a blood vessel or muscle. A second injection might not add benefit.

Carpal tunnel syndrome occurs when a nerve in the "carpal tunnel" of the wrist is compressed or squashed. It causes pain, numbness and prickling sensations in the affected hand. Carpal tunnel syndrome often goes away by itself, but it can sometimes be severe and long-lasting.

A common treatment for relieving carpal tunnel pain is to inject corticosteroids (often simply called "steroids") directly into the carpal tunnel. Corticosteroids are types of synthetic hormones that reduce swelling. We call this a local injection, because the injection is made into the affected area. This kind of treatment is normally given if the symptoms are not too serious.

How do corticosteroid injections compare?

To find out how effective local corticosteroid injections are, researchers from the Cochrane Collaboration looked at the results of clinical trials comparing local corticosteroid injections either with other non-surgical treatments, or with an injection that had no medication (placebo). The researchers wanted to see how often the injections worked and how long the pain-relieving effects lasted. They were also interested in how the injections compared to other treatments.

The researchers found 12 studies involving more than 650 participants altogether. Two trials showed that, after four weeks, corticosteroid injections had reduced symptoms more than a placebo injection. Another trial showed that two injections (given eight weeks apart) had the same effect as one injection.

A further trial found that local injections were similar to oral corticosteroids in the short term but were more effective in the long term (up to 12 weeks). One of the trials showed that a local injection was better than a "systemic" injection. A systemic injection is injected into a vein rather than directly into the carpal tunnel. Two trials showed no difference between local corticosteroid injections and other treatments, including anti-inflammatory drugs with wrist splints. More research is needed to be sure about whether other treatments relieve symptoms better or for longer than local injections do.

Long-term effects not clear

A few trials compared the long-term effects of local injections with placebo, but they were of poor quality and had conflicting results. The long-term effects of carpal tunnel syndrome treatments are difficult to test in a trial - researchers are reluctant to use placebo treatments in long-term trials. For this reason, there are good, long-term trials on corticosteroids comparing two treatments against each other (such as the trial about corticosteroid tablets mentioned above), but no good, long-term trials comparing a treatment with a placebo.

Although several good-quality trials show that local corticosteroid injections can relieve carpal tunnel syndrome pain in the short term, more research is needed to find out whether other treatments could be more effective at reducing pain or providing long-lasting relief. A Cochrane Collaboration review will also be done in the near future to assess adverse effects of local corticosteroid injections. We will add those results or new information about other treatments when they become available.

© IQWiG (Institute for Quality and Efficiency in Health Care)