New role for insulin injection in the treatment of idiopathic carpal tunnel syndrome

Objective Local insulin injection for the median nerve was administered in patients with mild to moderate idiopathic carpal tunnel syndrome (CTS) to evaluate its effectiveness on the median nerve regeneration as it has been suggested that insulin has an effect on nerve regeneration, similar to that of nerve growth factor. Patients and methods This study included 82 patients (130 hands) with clinical and electrophysiologic evidence of mild to moderate idiopathic CTS (grade 3 or less according to Bland’s classification). The 130 hands were randomly assigned to two groups: group I received insulin injection of 10 IU Neutral Protamine Hagedorn known as humulin N (NPH) insulin locally into the affected carpal tunnel at the first visit and a similar dose of insulin after 2 weeks; and group II received a single injection of 40 mg triamcinolone acetonide injection into the carpal tunnel. Clinical and electrophysiologic evaluations were carried out at the start of the study and at 1 month after treatment. Patients were evaluated on the basis of the mean score on the Symptom Severity Scale and Functional Status Scale of the Boston Carpal Tunnel Questionnaire. Results All patients showed a symptomatic and functional improvement. Distal motor latency and distal sensory latency were decreased for both groups (4.84±0.74 vs. 4.61±0.72 and 2.88±0.27 vs. 2.55±0.19, respectively), with a significant decrease in the mean of Functional Status Scale score and Symptom Severity Scale score for patients treated with the insulin injection (2.5±0.6 vs. 2.07±0.55 and 3.13±0.47 vs. 2.23±0.5, respectively). Conclusion Local insulin injection effectively reduced the symptoms of CTS and improved electrophysiological findings in the present study. Our findings suggest that local insulin injection may be of great benefit in improving nerve functions in patients with mild to moderate idiopathic CTS. Further controlled studies are needed to confirm our preliminary findings and to compare local insulin injection with conventional approaches for the treatment of CTS.