Have You Ever Seen the Impact of Crossing Fiber in DTI?: Demonstration of the Corticospinal Tract Pathway

OBJECTIVE: The identification of the corticospinal tract (CST) pathway with a deterministic fiber tracking approach is limited because of crossing fibers, especially for the hand fibers of the CST due to the crossing superior longitudinal fasciculus (SLF). We examined a patient with congenital bilateral perisylvian syndrome (CBPS) who did not have the SLF, in order to visualize CST hand fibers that were not affected by crossing fibers. METHODS: A 10-year-old girl without the SLF due to CBPS and three normal healthy subjects participated in this study. We used a deterministic fiber tracking algorithm, and the regions of interest (ROIs) were drawn in the posterior limb of internal capsule (PLIC) and the primary motor cortex. The apparent diffusion coefficient (ADC), fractional anisotropy (FA), relative anisotropy (RA), and volume ratio (VR) were measured based on the extracted fiber tracts. RESULTS: The ADC values were not different between the normal subjects and the patient with CBPS. The FA, RA, and VR values of the normal subjects were similar, but were relatively higher than those of the patient with CBPS. CONCLUSION: Our results clearly show the impact of the crossing fiber for the hand motor fibers of the CST pathway with deterministic tracking algorithms in diffusion tensor tractography.