The median to ulnar cross-sectional surface area ratio in carpal tunnel syndrome.

OBJECTIVE: To investigate the use of a sonographic median-to-ulnar cross-sectional area ratio (MUR) in diagnosis of carpal tunnel syndrome (CTS); and to compare the MUR with currently used sonographic parameters, and electrophysiology.

METHODS: Subjects with CTS and healthy volunteers underwent ultrasound studies of the median and ulnar nerves in the wrist and forearm. Various sonographic parameters and ratios were calculated, and compared between CTS patients and controls. The sensitivity and specificity of the different parameters were compared by plotting receiver operator characteristic curves. Correlations of sonographic results with electrophysiologic studies were calculated.

RESULTS: The MUR was increased in patients with CTS, in comparison with controls. A cut-point of >2.09 yielded a sensitivity of 86% and specificity of 84%. This was comparable to the currently used ultrasound metrics for CTS. The MUR also correlated with electrophysiologic severity.

CONCLUSIONS: The MUR is an effective means of diagnosing CTS and correlates with electrophysiologic severity.

SIGNIFICANCE: This report provides support for the use of the MUR in the sonographic diagnosis of CTS.