Five-Year Serial Brain MRI Analysis of Military Members Exposed to Chronic Sub-Concussive Overpressures

BackgroundThe Canadian Special Operations Forces Command conducts explosives operations and training which exposes members to explosive charges at close proximity. This 5‐year longitudinal trial was conducted in follow‐up to our initial trial which examined military breachers with MRI and EEG pre and post blast exposure.PurposeTo examine brain MRI findings in military personnel exposed to multiple repeated blast exposures.Study TypeFive‐year longitudinal prospective trial.PopulationNinety‐two males aged 23–42 with an average of 9.4 years of blast exposure.Field Strength/Sequence3 T brain MRI/T1‐weighted 3D with reconstruction in three planes, T2‐weighted, T2‐weighted fluid attenuated inversion recovery (FLAIR) 3D with reconstruction in three planes, T2‐weighted gradient spin echo (GRE), saturation weighted images, DWI and ADC maps, diffusion tensor imaging.AssessmentAll MRI scans were interpreted by the two neuroradiologists and one neuroradiology Fellow in a blinded fashion using a customized neuroradiology reporting form.Statistical TestsMatching parametric statistics represented the number of participants whose brain parameters improved or deteriorated over time. Odds ratio (OR) and 95% confidence intervals (CI) were computed using log regression modeling to determine volume loss, white matter lesions, hemosiderosis, gliosis, cystic changes and enlarged Virchow Robin (VR) spaces. A Kappa (κ) statistic with a 95% CI was calculated to determine rater variability between readers.ResultsA significant deterioration was observed in volume loss (OR = 1.083, 95% CI 0.678–1.731, permutation test), white matter changes (OR: 0.754, 95% CI 0.442–1.284, permutation test), and enlargement of VR spaces (OR: 0.775, 95% CI 0.513–1.171). Interrater reliability was low: κ = 0.283, 0.156, and 0.557 for volume loss, white matter changes, and enlargement of VR spaces, respectively.Data ConclusionThere were significant changes in brain volume, white matter lesions, and enlargement of VR spaces.Evidence Level2Technical EfficacyStage 2