Fig 4. Color-coded FA-maps of the decussation of the pyramidal tracts. A, In a healthy subject, the transverse orientation of the decussating fibers of the pyramidal tracts can be identified as a "red dot" within the caudal medulla (arrows). B, In JS, the "red dot" is missing, indicating that the pyramidal tracts do not cross within the caudal medulla. C, Fiber tractography displays the course of the pyramidal tracts (blue encoded) in a coronal projection. No crossing fibers could be identified, and the pyramidal tracts show a parallel course within the caudal medulla. A group of the noncrossing fibers within the superior cerebellar peduncles are also displayed on the left side (green encoded). An anatomic axial section is projected within the display for orientation purposes. D, In a healthy subject, fiber tractography displays the normal course of the pyramidal tracts (blue encoded) in a coronal projection. A partially red-encoded pyramidal decussation is seen at the level of the caudal medulla (large arrows). The red-encoded decussation of the superior cerebellar peduncles is seen at the level of the mesencephalon (arrowheads). In addition, multiple red-encoded crossing fibers are seen at the level of the pons (small arrows).