Injection with methylprednisolone proximal to the carpal tunnel: randomised double blind trial

Abstract Objective: To assess the effect of a 40 mg methylprednisolone injection proximal to the carpal tunnel in patients with the carpal tunnel syndrome. Design: Randomised double blind placebo controlled trial. Setting: Outpatient neurology clinic in a district general hospital. Participants: Patients with symptoms of the carpal tunnel syndrome for more than 3 months, confirmed by electrophysiological tests and aged over 18 years. Intervention: Injection with 10 mg lignocaine (lidocaine) or 10 mg lignocaine and 40 mg methylprednisolone Non-responders who had received lignocaine received 40 mg methylprednisolone and 10 mg lignocaine and were followed in an open study. Main outcome measures: Participants were scored as having improved or not improved. Improved was defined as no symptoms or minor symptoms requiring no further treatment. Results: At 1 month 6 (20%) of 30 patients in the control group had improved compared with 23 (77%) of 30 patients the intervention group (difference 57% (95% confidence interval 36% to 77%)). After 1 year, 2 of 6 improved patients in the control group did not need a second treatment, compared with 15 of 23 improved patients in the intervention group (difference 43% (23% to 63%). Of the 28 non-responders in the control group, 24 (86%) improved after methylprednisolone. Of these 24 patients, 12 needed surgical treatment within one year. Conclusion: A single injection with steroids close to the carpal tunnel may result in long term improvement and should be considered before surgical decompression. Key messages Corticosteroid injections into the carpal tunnel may damage the nerve, and any treatment benefits may be of short duration A single injection with steroids proximal to the carpal tunnel improves 77% of patients with the carpal tunnel syndrome at one month after treatment This single injection is still effective at one year in half of the patients Injections proximal to the carpal tunnel have no side effects and are easier to carry out than injections into the carpal tunnel