Anatomical location and somatotopic organization of the corticospinal tract in the corona radiata of the normal human brain: a diffusion tensor tractography study.

The anatomical location and somatotopic organization of the corticospinal tract (CST) in the corona radiata (CR) of the normal human brain have not been studied using diffusion tensor tractography so far. In this study, the anatomical location and somatotopic organization of the CST in the CR were evaluated by determining the highest probabilistic locations and distances between the upper and lower extremities in the slices of upper and lower CR in the brain. In the mediolateral direction, the average of the highest probabilistic locations for the upper and lower extremities were 40.27 and 37.16% at the upper CR level and 38.19 and 37.14% at the lower CR level, respectively. In the anteroposterior direction, the average of the highest probabilistic locations for the upper and lower extremities were 62.52 and 75.65% at the upper CR level and 60.19 and 68.12% at the lower CR level, respectively. The average distances between upper and lower extremities for the mediolateral direction were 2.41 mm at the upper CR level and 1.21 mm at the lower CR level. The average distances between upper and lower extremities for the anteroposterior direction were 5.23 mm at the upper CR level and 4.47 mm at the lower CR level, respectively. Our findings suggest that the anatomical location and somatotopic organization for the upper extremity are located anterolaterally to the lower extremity in the CR of a normal human brain and distances between the upper and lower extremities become decreased as the CST descends from the upper to the lower CR level.