The intrinsic arterial vascularity and morphology of the median nerve within the carpal tunnel: a microscopic study.

Carpal tunnel syndrome (CTS) is the commonest peripheral nerve entrapment neuropathy and is more prevalent in females for reasons that are not fully understood. The aim of this study was to investigate the intrinsic arterial supply of the median nerve in the region of the carpal tunnel to determine if there are significant individual variations. The median nerve was excised intact from 34 cadaver hands (7 male, 13 female; 18 right, 16 left; age 66-100 years) and sectioned at three levels: 1 cm proximal to the transverse carpal ligament; at the entrance to the carpal tunnel; and 1 cm distal to the latter site. Photomicrographs of histological sections were analyzed using ImageJ and the following recorded: the shape and cross-sectional area (CSA) of the nerve and the total CSA of small arteries/arterioles (>80 μm(2)) within the nerve. The proportion of the nerve's CSA occupied by arteries/arterioles was expressed as a ratio to compare vascularity at the three levels. There were no significant differences between hands or levels in males, but in right hands from female cadavers there was a statistically significant reduction in the intrinsic arterial vascularity of the median nerve at the entrance to the carpal tunnel as compared to proximal and distal levels and left hands (p < 0.05). Gender-based differences in the intrinsic arterial supply of the median nerve could be a factor predisposing to CTS.