Ultrasonographic changes after steroid injection in carpal tunnel syndrome

Objective To determine the ultrasonographic changes after steroid injection in carpal tunnel syndrome (CTS) and to evaluate the diagnostic value of ultrasound in post-treatment examination with clinical correlation. Materials and Methods Twenty-seven wrists with idiopathic CTS after a single injection of 40 mg of prednisolone hydrochloride were prospectively studied using a high-resolution ultrasound. Axial images of the wrists were obtained at the level of the distal radius, pisiform and hamate prior to and 1, 4 and 8 weeks after steroid injection. The cross-sectional area (CSA, mm(2)) and flattening ratio (FR) of the median nerve were measured. The bowing of the flexor retinaculum (palmar displacement: PD, mm) and the transverse sliding distance of the median nerve (TSD, mm) during flexion-extension of the index finger were computed. Pre- and post-injection ultrasonographic findings were analyzed in relation to clinical parameters such as pain score. Results At all levels of the wrist, the CSA decreased significantly at 1 week after the injection, which continued to 8 weeks post-injection. The PD also diminished significantly 1 week after the injection. Furthermore, the TSD significantly increased from 1 week after injection, which lasted to the end of this study. The CSA, PD and TSD showed significant correlation with improvement of pain scores. Conclusion Ultrasound is useful in follow-up examinations of CTS. Significant ultrasound findings after steroid injections in CTS include decreased swelling of the median nerve, decreased bowing of the flexor retinaculum and increased mobility of the median nerve. All of them significantly correlate with clinical symptoms.