Local insulin injection improves median nerve regeneration in NIDDM patients with carpal tunnel syndrome.

It has been suggested that insulin has an effect on nerve regeneration similar to that of nerve growth factor (NGF). Therefore, we aimed to evaluate the effectiveness of local insulin injection on median nerve in patients with non-insulin-dependent diabetes (NIDDM) mellitus who have mild-to-moderate carpal tunnel syndrome (TS). We carried out a prospective, randomized, double-blind, placebo-controlled study in these patients. At the baseline, 20 mg methylprednisolone was injected directly into the carpal tunnel in all patients [n=43 (62 hands)]. A week after prednisolone, the placebo or NPH insulin (12 U) was injected into the carpal tunnel weekly for 7 weeks. The patients were followed up for 23 weeks. A significant improvement in mean median nerve motor distal latency (MNMDL), median nerve sensory velocity (MNSV), and global symptom score (GSS) occurred in both groups (with the exception of mean MNMDL in the placebo group). A more significant improvement in the mean MNMDL, MNSV, and GSS was observed in the insulin group when compared with the placebo group. This study suggests that local insulin treatment may be of great potential benefit in the improvement of nerve functions in NIDDM patients with mild-to-moderate CTS who opt for conservative treatment.