Novel neuroimaging biomarker of cortical gray/white border integrity in blast related-mTBI

BACKGROUND: Recent studies suggest that blast or mid impact neurotrauma are characterized by scar-border forming astrogliosis at the gray-white matter junction. Individuals with mTBI and blast trauma have increased neuroinflammation and impairment of axonal remyelination on post-mortem histopathology. However, there are currently only limited methodologies to use in the assessment of the cortical gray/white interface using in vivo neuroimaging. PURPOSE: To investigate the gray-white matter contrast at the gray-white matter junction that may be linked to neuroinflammation/astrogliosis in the setting of blast exposure and/or mTBI, through 3D T1 weighted magnetization prepared rapid gradient-echo (MP-RAGE) images. MATERIALS AND METHODS: Post-9/11 Veterans (n=723) from the Translational Research Center for TBI and Stress disorders (TRACTS) completed MR imaging. Participants were grouped into 4 categories: Participants with a history of blast-related mTBI (blast-mTBI); participants with a history of mTBI due to other mechanical forces (blunt-mTBI); participants with history of close blast exposure but no mTBI; and those without history of lifetime mTBI or close bast exposure. MR imaging data processing for morphometry and cortical surface mapping was done using FreeSurfer image analysis. Signal intensities in gray and white matter along the cortical and white matter interface were used to calculate mean gray-white matter contrast value (GWC). RESULTS: Veterans in the blast-mTBI group showed diffuse patterns of increased GWC relative to the other groups, particularly in the frontotemporal lobes. This effect was driven primarily by a greater number of high GWC in the blast-mTBI group compared to the no-neurotrauma and blunt-mTBI groups. CONCLUSION: There was diffuse increased GWC on MR in the blast-mTBI group compared to the no neurotrauma, close blast exposure and blunt-mTBI groups. These findings may be linked to astrogliosis and neuroinflammation in blast-mTBI patients. Histopathologic correlation with imaging findings will be necessary to better understand these effects. SUMMARY STATEMENT: A novel neuroimaging biomarker of diffuse increases in contrast at the gray-white matter junction in bast-mTBI may be linked to neuroinflammation and may be related to changes in myelin and/or astrogliosis.