Is Palmar Cutaneous Branch of the Median Nerve More Swollen in Carpal Tunnel Syndrome?

Objective To investigate the characteristics of the palmar cutaneous branch of the median nerve (PCBMN) in patient with carpal tunnel syndrome (CTS) using high-resolution ultrasound. Methods Fourteen healthy volunteers (17 wrists) and 31 patients with CTS (41 wrists) were evaluated by highresolution ultrasound. All patients were classified into three groups based on the electrophysiologic CTS impairment severity: mild, moderate, and severe. Using high-resolution ultrasound, the cross-sectional areas (CSAs) of the PCBMN were measured at the proximal wrist crease, bistyloid line, and distal wrist crease, and the largest CSA was defined as the maximal CSA. Results The maximal CSA of the PCBMN of the control, mild, moderate, and severe CTS groups were 0.27±0.08, 0.30±0.07, 0.35±0.10, and 0.47±0.13 mm², respectively. The maximal CSA of the PCBMN was significantly larger in the severe CTS group than in the other groups. Conclusion The PCBMN could be concomitantly affected in patients with severe CTS.