Feasibility of Ultrasonographic Area Ratio of Median Nerve in the Diagnosis of Carpal Tunnel Syndrome in Korea

ABSTRACT

OBJECTIVE: To examine the usefulness of ratio of maximal swelling to normal cross sectional area (CSA) of median nerve with ultrasound in patients with carpal tunnel syndrome (CTS) and healthy controls. METHOD: Patients with electrodiagnostically proven CTS underwent ultrasonography of the median nerve. The median nerve area was measured at three points (maximal swelling site, 2 cm proximal to maximal swelling site, 12 cm proximal to maximal swelling site) and compared to values from asymptomatic volunteers. RESULTS: The ratio of maximal swelling site to 12 cm proximal was 1.34+/-0.14 in asymptomatic volunteers and 2.31+/-0.43 in patients presenting with CTS. The ratio of maximal swelling site to 12 cm proximal gave 73.7% sensitivity and 90.0% specificity. While using only median nerve area at the wrist resulted in 81.6% sensitivity and 70.0% specificity, depending on the cutoff value used. CONCLUSION: The ratio of maximal swelling site to proximal in patients with CTS is elevated as compared to asymptomatic controls. The ratio of maximal swelling site to 12 cm proximal has higher specificity to diagnose CTS, and may be superior to measuring median nerve area at the wrist alone.