PLS is a disease of the UMN, distinguished from ALS in prognosis and absence of LMN signs. We present, to our knowledge, the first conventional MR imaging visualization of the callosal motor segment, a concept previously supported by primate models, electrophysiologic studies, and postmortem examinations. Modification of the Witelson topographic scheme of the CC is supported by MR tractography. On the basis of 2 cases of PLS, we present conventional imaging confirmation of the revised topographic scheme of fiber distribution across the CC.
Riad, S. M., Hathout, H., & Huang, J. C. (2011). High T2 signal in primary lateral sclerosis supports the topographic distribution of fibers in the corpus callosum: Assessing disease in the primary motor segment. American Journal of Neuroradiology, 32(4). https://doi.org/10.3174/ajnr.A2067