Combat-related Mild Traumatic Brain Injury: Association between Baseline Diffusion-Tensor Imaging Findings and Long-term Outcomes

Purpose: To determine whether functional outcomes of veterans who sustained combat-related mild traumatic brain injury (TBI) are associated with scalar metrics derived from diffusion- tensor (DT) imaging at their initial postdeployment evaluation. Materials and Methods: This HIPAA-compliant retrospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. From 2010 to 2013, initial postdeployment evaluation, including clinical assessment and brain magnetic resonance (MR) examination with DT imaging, was performed in combat veterans who sustained mild TBI while deployed. Outcomes from chart review encompassed initial postdeployment clinical assessment as well as later functional status, including evaluation of occupational status and health care utilization. Scalar diffusion metrics from the initial postdeployment evaluation were compared with outcomes by using multivariate analysis. Veterans who did and did not return to work were also compared for differences in clinical variables by using t and x(2) tests. Results: Postdeployment evaluation was performed a mean of 3.8 years after injury (range, 0.5-9 years; standard deviation, 2.5 years). After a mean follow-up of 1.4 years (range, 0.5-2.5 years; standard deviation, 0.8 year), 34 of 57 veterans (60%) had returned to work. Return to work was associated with diffusion metrics in multiple regions of white matter, particularly in the left internal capsule and the left frontal lobe (P = .02-.05). Overall, veterans had a mean of 46 health care visits per year during the follow-up period (range, 3-196 visits per year; standard deviation, 41 visits per year). Cumulative health care visits over time were inversely correlated with diffusion anisotropy of the splenium of the corpus callosum and adjacent parietal white matter (P < .05). Clinical measures obtained during initial postdeployment evaluation were not predictive of later functional status (P = .12-.8). Conclusion: Differences in white matter microstructure may partially account for the variance in functional outcomes among veterans who sustained combat-related mild TBI. (C) RSNA, 2016