The use of diagnostic ultrasound in carpal tunnel syndrome.

PURPOSE: Traditional evaluation of suspected carpal tunnel syndrome (CTS) involves a thorough history, physical examination, and nerve conduction velocity studies (NCS). Ultrasound is used widely in Europe and has gained acceptance in the United States in the diagnosis of various musculoskeletal disorders. The purpose of this study was to document the ultrasonographic measurement difference in median nerve size between patients with CTS and controls and to correlate these findings with NCS findings, thereby allowing us to test the validity of ultrasound as a diagnostic modality for CTS.

METHODS: Forty-four wrists in 26 CTS patients and 86 wrists in 43 asymptomatic volunteers were imaged using a real-time ultrasound scanner with a 12/5 MHz linear-array transducer. The cross-sectional area of the median nerve was measured at the level of the distal wrist crease in both CTS patients and controls. All CTS patients had NCS. The ultrasonographic median nerve area was compared for the 2 groups and correlation analysis between ultrasonographic nerve sizes and NCS findings was performed.

RESULTS: The average cross-sectional area of the median nerve at the distal wrist crease was 9 mm(2) in asymptomatic volunteers and 14 mm(2) in CTS patients. For the CTS patients the Pearson correlation coefficient between ultrasound nerve measurement and NCS values was 0.37, suggesting that higher values of ultrasound measurements are associated with abnormal NCS findings.

CONCLUSIONS: Our results indicate that high-resolution ultrasound is informative in the evaluation of CTS and shows enlargement of the median nerve at the distal wrist crease in symptomatic patients. Therefore it is a reliable modality for imaging the wrist in patients with CTS. In addition ultrasound is well tolerated and safe.

TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic, Level I.