Ultrasound features of carpal tunnel syndrome: a prospective case-control study

The purpose of the study was to examine the most adequate cut-off point for median nerve cross-sectional area and additional ultrasound features supporting the diagnosis of carpal tunnel syndrome (CTS). Forty wrists from 31 CTS patients and 63 wrists from 37 asymptomatic volunteers were evaluated by ultrasound. All patients were women. The mean age was 49.1 years (range: 29-78) in the symptomatic and 45.1 years (range 24-82) in the asymptomatic group. Median nerve cross-sectional area was obtained using direct (DT) and indirect (IT) techniques. Median nerve echogenicity, mobility, flexor retinaculum measurement and the anteroposterior (AP) carpal tunnel distance were assessed. This study was IRB-approved and all patients gave informed consent prior to examination. In CTS the median nerve cross-sectional area was increased compared with the control group. Median nerve cross-sectional area of 10 mm2 (DT) and 9 mm2 (IT) had high sensitivity (85% and 88.5%, respectively), specificity (92.1% and 82.5%) and accuracy (89.3% and 82.5%) in the diagnosis of CTS. CTS patients had an increased carpal tunnel AP diameter, flexor retinaculum thickening, reduced median nerve mobility and decreased median nerve echogenicity. Ultrasound assists in the diagnosis of CTS using the median nerve diameter cut-off point of 10 mm2 (DT) and 9 mm2 (IT) and several additional findings. (orig.)