Diffuse axonal injury (DAI) is characterized by diffuse white matter (WM) disruption caused by shearing forces acting on the brain. Cortical atrophy can be accompanied by WM disruption, which is assumed to reflect the loss of neuron cell bodies in gray matter (GM) regions adjacent to disrupted WM. It remains unclear whether WM disruption leads to regional GM alteration in DAI. The aim of the present study was to assess WM disruption and corresponding GM alterations in patients with DAI using a connectome-based approach. Twenty-four patients and 24 healthy controls underwent magnetic resonance imaging with diffusion tensor imaging (DTI). Deterministic fiber tracking was conducted to investigate structural connectivity between the corpus callosum (CC) and each pre-defined regional cortical area. We calculated 85 × 85 connectivity matrices for fractional anisotropy (FA). Group comparisons were conducted to identify abnormal connectivity in patients. Further, the regional cortical volume of each connectivity matrix was compared between patients and controls. Finally, correlation analyses between the matrices and regional cortical volumes were performed within the patient group. Connectome analyses revealed that, compared with controls, patients exhibited a FA reduction in connectivity via CC to 32 cortical regions including the frontal, parietal, and occipital cortices. Among these regions, GM volume was reduced in 19 of 32 regions. There were no significant correlations between WM disruption in which abnormal connectivity was identified and the corresponding GM alterations. These results suggest that GM pathology is, at least in part, independent of the corresponding WM damage in DAI.
Keywords: CC; GM volume; connectome; traumatic brain injury.