Evaluation of the somatotopic organization of corticospinal tracts in the internal capsule and cerebral peduncle: results of diffusion-tensor MR tractography.
OBJECTIVE
We have used diffusion tensor tractography (DTT) for the evaluation of the somatotopic organization of corticospinal tracts (CSTs) in the posterior limb of the internal capsule (PLIC) and cerebral peduncle (CP).


METHODS
We imaged the brains of nine healthy right-handed subjects. We used a spin-echo echo-planar imaging (EPI) sequence with 12 diffusion-sensitized directions. DTT was calculated with an angular threshold of 35 degrees and a fractional anistropy (FA) threshold of 0.25. We determined the location of the CSTs by using two regions of interest (ROI) at expected areas of the pons and expected areas of the lateral half of the PLIC, in the left hemisphere of the brain. Fiber tracts crossing these two ROIs and the precentral gyrus (PCG) were defined as CSTs. Four new ROIs were then defined for the PCG, from the medial to lateral direction, as ROI 1 (medial) to ROI 4 (lateral). Finally, we defined each fiber tract of the CSTs between the pons and each ROI in the PCG by using two ROIs methods.


RESULTS
In all subjects, the CSTs were organized along the long axis of the PLIC, and the hand fibers were located anterior to the foot fibers. The CSTs showed transverse orientation in the CP, and the hand fibers were located usually medial to the foot fibers.


CONCLUSIONS
Corticospinal tracts are organized along the long axis of the PLIC and the horizontal direction of the CP.
Park
Ji Kang
JK
Department of Radiology, Cheju National University College of Medicine, Jeju, Korea. jkcontrast@naver.com
Kim
Bong Soo
BS
Choi
Gukmyung
G
Kim
Seung Hyoung
SH
Choi
Jay Chol
JC
Khang
Hyunsoo
H
D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D020772:Internal Capsule / Q000033:anatomy & histology*; D008297:Male; D011712:Pyramidal Tracts / Q000033:anatomy & histology*; D013681:Tegmentum Mesencephali / Q000033:anatomy & histology*