Median nerve deformation during finger motion in carpal tunnel syndrome: correlation between nerve conduction and ultrasonographic indices.

To compare the median nerve deformation indices between carpal tunnel syndrome (CTS) patients and controls, 60 wrists of asymptomatic volunteers and 40 wrists of idiopathic CTS patients were evaluated by ultrasound. CTS was diagnosed through clinical findings and nerve conduction studies. Deformation indices, which were determined by the ratios of the nerve cross-sectional area, perimeter, aspect ratio, and circularity in finger extension and flexion positions, were measured. The deformation indices were compared between patients and controls. The correlation coefficients between distal motor latency and deformation indices were measured in CTS patients. There were significant differences between patients and controls in the deformation indices of perimeter, aspect ratio, and circularity. There was a mild correlation between distal latency and deformation indices of the perimeter and circularity (correlation coefficient 0.315 and 0.342). The deformation indices of perimeter and circularity might be useful to identify the nerve conduction severity of CTS.