Predictive variables for sonographically guided corticosteroid injection in mild-to-moderate carpal tunnel syndrome

Objective To assess the predictive variables after sonographically guided corticosteroid injection in carpal tunnel syndrome. Methods A prospective, observational study was carried out on 25 wrists of 20 consecutive patients with carpal tunnel syndrome, confirmed by the American Association of Neuromuscular and Electrodiagnostic Medicine criteria, which includes clinical history, symptoms, and evidence of slowing of distal median nerve conduction. Visual analogue scale (VAS) and Boston Carpal Tunnel Questionnaire (BCTQ) were asked to the patients before and 4 weeks after the procedure. On a basis of VAS difference before and after the procedure, we divided the patients into two groups: more than 50% of VAS improving (good response group) and less than 50% of VAS improving (poor response group). Also, nerve conduction studies and ultrasound evaluations were performed prior to sonographically guided corticosteroid injection and at 4 weeks after the procedure. The cross-sectional area (CSA) of median nerve at maximal swelling point around wrist was measured by manual tracing using ultrasonography. With assessments mentioned above, we tried to assess predictive variables for prognosis after sonographically guided corticosteroid injection in carpal tunnel syndrome. Results The CSA of median nerve at wrist measured before the procedure was significantly larger in good response group than in poor response group. Furthermore, the CSA of median nerve at wrist, symptom severity scale of BCTQ, motor/sensory latency and sensory amplitude were correlated with VAS improving. Conclusion The CSA of median nerve at wrist is the strongest predictive value for sonographically guided corticosteroid injection in mild-to-moderate carpal tunnel syndrome.