Effect of Local Corticosteroid Injection in the Non-Injected Hand Following Unilateral Injection in Patients With Bilateral Carpal Tunnel Syndrome: A Prospective Cohort Study.

INTRODUCTION/AIMS: Local corticosteroid injection (LCI) improves symptoms in the injected hand of carpal tunnel syndrome (CTS). Whether it affects the non-injected hand is unknown. This study assesses the effect of unilateral LCI on the non-injected hand in mild to moderate bilateral CTS.

METHODS

Sixty patients with bilateral CTS were recruited from December 2021 to August 2024 and received a unilateral injection of 1 mL (40 mg) depo-methylprednisolone with 0.5 mL (10 mg) lidocaine in the more severely affected or dominant hand if symptoms were comparable. The primary outcome was the change in Symptom Severity Scale (SSS) score of the non-injected hand at 1 and 3 months. Secondary outcomes were the comparison of response rates and the change in the median nerve electrophysiology at 3 months in both hands. A significant response was defined as ≥ 0.8 reduction in SSS.

RESULTS

The median age of patients was 45 (range 20-81) years. Seven patients were lost to follow-up at 1 month and 15 at 3 months. Mean SSS change was significantly greater in the injected than in the non-injected hands at 1 month (-1.25 ± 0.64 vs. -0.89 ± 0.67; p < 0.01) and 3 months (-1.23 ± 0.72 vs. -0.77 ± 0.64; p < 0.01). Taking patients lost to follow-up as treatment failures, response rates at 3 months were 65% in injected hands and 57% in non-injected hands (p = 0.45). Median nerve conduction improved bilaterally at 3 months.

DISCUSSION: Unilateral LCI in bilateral mild to moderate CTS results in significant symptomatic improvement in the contralateral hand, underscoring the need to routinely assess the non-injected hand in treatment assessment.