Ultrasonographic Measurement of the Median Nerve Transverse Diameter at the Wrist for Diagnosing Carpal Tunnel Syndrome

Background: Ultrasonographically measuring the median nerve cross-sectional area (MN-CSA) is a useful and complementary method for diagnosing carpal tunnel syndrome (CTS). This study investigated the usefulness of the median nerve transverse diameter (MN-TD) as a simpler and easier technique than MN-CSA for diagnosing CTS severity. Methods: We examined 145 hands from 101 patients with CTS and 114 age- and gender-matched control hands. Based on the electrodiagnostic findings, the severity of CTS was divided into minimal, mild, moderate, severe and extreme. An ultrasonographic assessment of MN-TD and MN-CSA was performed to measure the maximal values around the carpal tunnel inlet level. The values were assessed for comparisons between the CTS and control groups and for the evaluation of differences by CTS severity. Results: The ultrasonographic measurements of MN-TD and MN-CSA were significantly increased in the CTS group compared to the normal group. Furthermore, both measurements significantly increased with increasing CTS severity. A receiver operating characteristic curve (ROC) analysis showed that participants with MN-TD > 7.2 mm had CTS with 88% specificity and 74% sensitivity, and those with MN-CSA > 12.0 mm2 had CTS with 86% specificity and 84% sensitivity. Conclusions: Ultrasonographic measurement for MN-TD may be useful for diagnosing CTS patients and predicting the severity.