Demonstration of Differentially Degenerated Corpus Callosam in Patients With Moderate Traumatic Brain Injury: With a Premise of Cortical-callosal Relationship

Traumatic brain injury (TBI) has been shown to predominantly affect the corpus callosum (CC). In light of the anatomical organization of cortico-callosal connections, we hypothesized that injury to the different cortical lobes may specifically affect their corresponding subdivisional fibers in the CC. The aim of this study was to investigate lesion-related Wallerian degeneration across the subdivisions of the CC in patients with moderate TBI. Diffusion tensor tractography (DTT) was performed between 14 days and 6 months after trauma in 18 patients with moderate TBI, and 11 age- and gender-matched healthy control subjects. Based on conventional magnetic resonance imaging findings, patients were classified into 3 groups: A) frontal lobe injury; B) occipito-temporal lobe injury; and C) fronto-parieto-temporal lobe injury. The CC was divided into seven subdivisions based on Witelson’s classifications. Fractional anisotropy (FA) and mean diffusivity (MD) values from the seven segments were compared among patient groups and controls. Compared to controls, Group A showed significantly reduced FA in the rostrum, genu, splenium, and CC. Group B showed significantly reduced FA in the isthmus and whole CC relative to that in the controls. In Group C, FA significantly decreased across the entire CC compared to that in the controls. In our study, subdivisional fibers of the CC showed secondary microstructural changes resulting from primary injury in the corresponding cortical areas. We conclude that DTT-derived measures may act as an indicator of ongoing Wallerian degeneration. By extension, this study may improve our understanding of variable neuropsychological outcomes in clinically similar patients with TBI