The goal of this study was to use diffusion-tensor magnetic resonance (MR) imaging to define the location and organization of corticospinal tracts (CSTs) in the posterior limb of the internal capsule (PLIC). The Institutional Review Board approved the study, and informed consent was obtained from all subjects. Eight volunteers and two patients with brain tumor were imaged at 3 T. All CSTs were found to lie in a compact area in one part of the PLIC: If the PLIC is divided into four equal quarters from anterior to posterior, the CST was shown to be in the third quarter. Seventeen of 20 CSTs were organized somatotopically, with hand fibers anterolateral to foot fibers, not anteromedial as is currently believed. In three of 20, hand and foot fibers were intermixed. Classically, it was thought that the CST was located in the anterior third of the PLIC. The present data confirm recent results that the CST is located more posteriorly. In the majority of cases, however, the CST is organized somatotopically.

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CT may be useful in detecting RVD in patients with acute PE.

The anatomy of the brain is extremely complex, and certain, even large structures, such as the corticospinal tract (CST), remain poorly understood. Diffusion tractography provides an opportunity to explore the white matter tracts in a fundamentally new way. In the current paper, we show how this technique has already added to our understanding of the anatomy of the CST. We also explore the future projects involving diffusion tractography of the motor white matter tracts that will advance this method and further our understanding of brain anatomy.