Identification of the anterior corticospinal tract in the human brain using diffusion tensor imaging.

The corticospinal tract (CST) is generally classified into the crossed lateral CST and the uncrossed anterior CST. No diffusion tensor imaging study for identification of the anterior CST in the human brain has been conducted. Using diffusion tensor imaging, we attempted to identify the anterior CST and investigate the characteristics of the anterior CST in the normal human brain. We recruited 15 healthy volunteers for this study. Diffusion tensor images were scanned using 1.5T. For the whole CST, two regions of interest were placed on the CST area of the pons and upper medulla. By contrast, for the anterior CST, an additional region of interest was given on the anterior funiculus of the upper cervical cord. The anterior CSTs, which originated from the cerebral cortex descended through the known pathway of the CST, and terminated in the anterior funiculus of the upper cervical cord. Compared with whole CSTs, the anterior CSTs showed decreased fiber number, fractional anisotropy, and apparent diffusion coefficient (P<0.05). The mean fiber number of the anterior CST was 12.4% of the whole CSTs. We identified the anterior CST and found that it has the characteristics of less directionality and fewer fibers in comparison with the whole CST. We believe that the methodology and results of this study would be helpful in research on motor control in the normal human brain and motor recovery mechanisms following brain injury.