Teaching NeuroImages: In vivo visualization of Edinger comb and Wilson pencils¶
Summary¶
Terminology¶
Original¶
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 Wilson 1; figure 1) before leaving the pallidum toward the substantia nigra in the form of a comb described by Edinger in 1896 2 (figure 2). A century later, these structures can be visualized in the living human brain (figures 1D and 2A).
Fig.1¶
Wilson pencils
(A) Histologic depiction (image courtesy of Dr. Michael Bonert, McMaster University, CCBY-SA3.0).
(B) Polarized light imaging in vervet monkey.
(C) First description by Wilson (Brain), reproduced with permission from S.A. Kinnier Wilson. An experimental research into the anatomy and physiology of the corpus striatum. Brain 1914;36:427–492. By permission of Oxford University Press, available at: academic.oup.com/brain/article/36/3-4/427/309802?searchresult=1. For permissions, please email journals.permissions@oup.com.
(D) Cardiac-gated T2*-weighted fast low angle shot sequence acquired using 7T MRI shows Wilson pencils.
Fig.2¶
Edinger comb
(A) Cardiac-gated fast low angle shot sequence shows Edinger comb.
(B) First description: “The pedunculus cerebri is traversed by striatal fibers that enter dorsally and connect peduncle and tegmentum—bundle between peduncle and tegmentum, comb system of the peduncle.”
(C) Axial histologic section in dark-field microscopy demonstrates the human comb system.