Abstract
DTI literature on single-center studies contains conflicting results regarding acute effects of mTBI on WM microstructure and their prognostic significance. This larger-scale multicenter DTI study aimed to determine how acute mTBI affects WM microstructure over time and how early WM changes affect long-term outcome. From TRACK-TBI, a cohort study at eleven US level 1 trauma centers, a total of 391 acute mTBI patients ages 17-60 years were included and studied at two weeks and six months postinjury. Demographically matched friends or family of the participants were the control group (n=148). Axial diffusivity (AD), fractional anisotropy (FA), mean diffusivity (MD), and radial diffusivity (RD) were the measures of WM microstructure. The primary outcome was the Glasgow Outcome Scale Extended (GOSE) score of injury-related functional limitations across broad life domains at 6 months postinjury. AD, MD, and RD were higher and FA was lower in mTBI versus FC at both two weeks and six months postinjury throughout most major WM tracts of the cerebral hemispheres. In the mTBI group, AD and, to a lesser extent, MD decreased in WM from two weeks to six months postinjury. At two weeks postinjury, global WM AD and MD were both independently associated with six-month incomplete recovery (GOSE<8 vs =8) even after accounting for demographic, clinical, and other imaging factors. DTI provides reliable imaging biomarkers of dynamic WM microstructural changes after mTBI that have utility for patient selection and treatment response in clinical trials. Continued technologic advances in the sensitivity, specificity, and precision of diffusion MRI hold promise for routine clinical application in mTBI.
