Figure 1

Results of diffusion tensor tractography for the pyramidal tract (PT) and the aberrant pyramidal tract (APT). (A) For the reconstruction of the PT, two regions of interest (ROIs) were placed on the posterior limb of the internal capsule and the PT area of the anterior medulla (portion of anterior blue color) on the color map. By contrast, for the reconstruction of the APT, three ROI were given on the posterior limb of the internal capsule, the PT area of the anterior medulla (portion of anterior blue color), and additional ROI was placed on the isolated APT area (behind the posterior transpontine fiber at the pontine level). (B) the PT and APT were constructed in the right hemisphere (red: the PT, yellow: the APT). The APT descended along the known pathway of the PT to the posterior limb of the internal capsule and then descended through the medial lemniscus from the midbrain to the pons (blue arrows). (C) The pathways of the PT and the APT are shown at the axial views (blue arrow: the APT was separated from the PT at the upper midbrain level, green arrow: the APT rejoined with the PT at the upper medulla level).