Teaching NeuroImages: In vivo visualization of Edinger comb and Wilson pencils

The “direct” and “indirect” pathways play crucial roles in movement disorder pathophysiology. Both traverse from the striatum to the internal pallidum and substantia nigra, the latter detouring to external pallidum and subthalamic nucleus. Anatomically, the pathways manifest within the striatofugal bundle that passes radially through the pallidum in the form of pencil-like tracts (first described by Wilson1; figure 1) before leaving the pallidum toward the substantia nigra in the form of a comb described by Edinger in 18962 (figure 2). A century later, these structures can be visualized in the living human brain (figures 1D and 2A).