For the new study, researchers, led by Dr. Shawn Marshall of the University of Ottawa in Canada, identified 12 published studies that tested corticosteroid injections for CTS. Overall, they found that a single steroid shot was more effective than a placebo at relieving patients' symptoms for one month.
There wasn't much evidence of a longer-term benefit, however. One study suggested that the symptom relief can last for 6 months, but another found that, over 8 weeks, the shots were no better than oral anti-inflammatory medications or wrist splints at improving CTS symptoms.
The findings appear in the Cochrane Library, which is published by the Cochrane Collaboration, an international organization that evaluates medical research.
"Our study conclusions suggest that benefit beyond 1 month is not assured," Marshall told Reuters Health. Nor is it clear which people with CTS are the best candidates for corticosteroid injections, according to the researcher.
For now, he said, people with moderate symptoms could try the therapy, as could those with severe symptoms who do not want surgery. People who are awaiting surgery could also try an injection for some temporary relief, Marshall added.
In the past, some doctors have balked at using corticosteroid injections for carpal tunnel because of concerns that it could cause nerve damage. The treatment is more accepted in Europe than in the U.S.
The new findings suggest that it can bring short-term relief to at least some CTS sufferers, according to Marshall's team. But if the first corticosteroid shot doesn't help, a second may not be worthwhile, the review found. There was no evidence that a second shot within a couple weeks of the first improved patients' responses.
The effects of the medication used in the injections should last for about 3 months, Marshall explained, and people who find no relief with the first shot may simply be "non-responders" to the therapy.
SOURCE: Cochrane Library, April 18, 2007.
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