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Classic anatomical atlases depict a contralateral hemispheral representation of each side of the face. Recently, however, a bilateral projection of each hemiface was hypothesized, based on animal studies that showed the coexistence of an additional trigeminothalamic tract sprouting from the trigeminal principal sensory nucleus that ascends ipsilaterally. This study aims to provide an anatomical substrate for the hypothesized bilateral projection. Three post-mortem human brainstems were scanned for anatomical and diffusion magnetic resonance imaging at 11.7T. The trigeminal tracts were delineated in each brainstem using track density imaging (TDI) and tractography. To evaluate the reconstructed tracts, the same brainstems were sectioned for polarized light imaging (PLI). Anatomical 11.7T MRI shows a dispersion of the trigeminal tract (tt) into a ventral and dorsal portion. This bifurcation was also seen on the TDI maps, tractography results and PLI images of all three specimens. Referring to a similar anatomic feature in primate brains, the dorsal and ventral tracts were named the dorsal and ventral trigeminothalamic tract (dtt and vtt), respectively. This study shows that both the dtt and vtt are present in humans, indicating that each hemiface has a bilateral projection, although the functional relevance of these tracts cannot be determined by the present anatomical study. If both tracts convey noxious stimuli, this could open up new insights into and treatments for orofacial pain in patients.

Original publication

DOI

10.1007/s00429-018-1767-1

Type

Journal article

Journal

Brain Struct Funct

Publication Date

01/2019

Volume

224

Pages

159 - 170

Keywords

Anatomy, Brainstem, Diffusion-weighted imaging, Ex-vivo high-resolution imaging, Histology, MRI, Polarized light imaging, Trigeminal pathways, Aged, Brain Stem, Cadaver, Diffusion Magnetic Resonance Imaging, Face, Female, Humans, Male, Microscopy, Polarization, Middle Aged, Neural Pathways, Trigeminal Nerve