Usefulness of Ultrasonography to Predict Response to Injection Therapy in Carpal Tunnel Syndrome

OBJECTIVE To verify the feasibility of initial parameters of ultrasonography or electromyography for the prediction of effect after steroid injection therapy in a carpal tunnel syndrome (CTS) patient. METHOD We recruited individuals with clinical and electrodiagnostic evidence of CTS. Results from the Boston self-assessment questionnaire, median motor and sensory nerve conduction studies, and median nerve ultrasonography were evaluated at baseline, 1 month, and 6 months after injection. Evaluation of median nerve ultrasonography parameters included measurements taken at the maximal swelling point (MS), 2 cm proximal from MS (2MS), and 12 cm proximal from MS (12MS), and its ratio (MS/12MS, 2MS/12MS) was calculated. The correlation between improvement of the symptom score after treatment and baseline parameters was estimated. RESULTS Fourteen individuals (14 women, mean age 53.8 years) with 22 affected wrists were enrolled. After steroid injection therapy, clinical and electromyographic parameters showed significant improvements at 1 month or 6 months after injection, and ultrasonographic parameters showed significant changes in maximal area and area ratio (MS/12MS) of the median nerve. Symptom score improvement showed a positive correlation in the initial 2MS and ratio of 2MS/12MS after 6 months (p<0.05). CONCLUSION Most of the improvements occurred during the first month after injection and lasted up to 6 months. The initial median nerve swelling and its ratio may be a useful predictor of response after steroid injection.