Value of ultrasonography in the diagnosis of carpal tunnel syndrome confirmed by nerve conduction study

Carpal tunnel syndrome (CTS) is the most common form of peripheral entrapment neuropathy. The use of sonography for investigation and diagnosis of musculoskeletal conditions has been rapidly increasing over the past few decades. The purpose of this study was to determine whether sonography can be an alternative method to nerve conduction study (NCS) in the diagnosis of CTS. This prospective cross-sectional descriptive study included patients with electrodiagnostically proven CTS and healthy control subjects. Anthropometric and demographic data included age, height, body mass index (BMI), sex, occupation, medication history, hand dominance, and underlying disorders associated with CTS. Median nerve Cross-Sectional Area (CSA), Flattening Ratio (FR), and flexor retinaculum thickness were measured. Then, we compared the results between ultrasonography and nerve conduction study. In this study, we assessed 120 wrists with CTS (cases) in 90 patients and 60 healthy wrists in 30 patients (control group). CTS was mild in 57, moderate in 29, and severe in 34 wrists. Post hoc comparisons between the patients with CTS and controls demonstrated that the cross sectional areas at various levels of the median nerve were significantly greater in the CTS group compared to the control group. CSA at the tunnel inlet with a threshold higher than 9.15 mm2 showed the best diagnostic accuracy with a sensitivity and specificity of 99.2% and 88.3% respectively. Cross-sectional areas of the median nerve in mild, moderate and severe carpal tunnel syndrome showed statistically significant differences. Ultrasonographic measurement of the cross-sectional area of median nerve is useful for the diagnosis and grading of CTS. Use of sonography as the first-line measure may effectively reduce the number of nerve conduction studies in the diagnosis of CTS.