Compression of the median nerve at the wrist often results in carpal tunnel syndrome, which is a common condition, particularly in women. Injection of corticosteroids into the carpal tunnel has been a standard treatment for many years; however, it carries the risk of damage to the nerves and associated structures. Dammers and colleagues evaluated the short- and long-term effects of injecting corticosteroids at a site proximal to the carpal tunnel.

The authors studied 60 patients who had been referred to an outpatient neurology clinic with symptoms of carpal tunnel syndrome lasting more than three months. In all cases, the diagnosis was confirmed by electrophysiologic testing. The patients were randomly assigned to receive lidocaine (10 mg) plus methylprednisolone (40 mg) or lidocaine (10 mg) alone. A single injection was given 4 cm proximal to the wrist crease between the tendons of the radial flexor and the long palmar muscles on the lateral side of the forearm. All injections were administered by the same neurologist. Patients were assessed by a second neurologist one month after the injection. Follow-up visits were available to patients every three months thereafter for one year. Patients, staff and both neurologists were unaware of the treatment assignments.

The 30 patients receiving combination treatment were similar in all significant respects to the 30 patients receiving lidocaine alone. At the one-month assessment, 23 (77 percent) of the patients receiving the steroids reported no or minor symptoms compared with six (20 percent) of the patients treated with lidocaine. The difference in relief of symptoms between the groups persisted over time. In the control group, 28 of the patients with persistent symptoms were subsequently treated with corticosteroid injection; improvement was achieved in 24 (86 percent) of these patients.

The authors conclude that injection of methylprednisolone proximal to the carpal tunnel resulted in lasting relief of symptoms in the majority of patients. The authors advocate the use of the proximal injection site because this area is frequently swollen in patients with carpal tunnel syndrome, and the steroid injection may have a pronounced local effect on hypertrophied tissue.