Location of the corticospinal tract at the corona radiata in human brain

Little is known about the location of the corticospinal tract (CST) at the corona radiata (CR). In the current study we attempted to elucidate the location of the CST for the hand at the CR using diffusion tensor tractography analysis based on functional MRI activation results. Functional MRI was performed at 1.5-T with timed hand grasp-release movements, and diffusion tensor tractography was performed using a Synergy-L Sensitivity Encoding (SENSE) head coil. Probabilistic mapping was obtained for 16 normal subjects using areas of functional MRI activation as the first region of interest (ROI 1) and the CST area in the lower pons as the second region of interest (ROI 2). The authors measured the antero-posterior and medio-lateral locations of pixels in the CST in two areas of the CR (CR 1 - the first axial image to show the septum pellucidum and the body of the fornix from the vertex, and CR 2 - the axial image showing the insular gyrus). The most probable locations in the medio-lateral direction (from the most medial point of the lateral ventricle wall to the most lateral point of the cerebral cortex) were 24.2% in both CR 1 and 2, and the most probable locations in the antero-posterior direction (from the most anterior point of the lateral ventricle to the most posterior point of the lateral ventricle) were 66.7 and 63.6% in CR 1 and 2, respectively. It was found that the CST for the hand descended through about one quarter (medio-lateral direction) and two-thirds (antero-posterior direction) at the CR.