Brain MRI Analysis of Cumulative Blast Exposure and Intracranial Aneurysms in Special Operations Forces

Background Special operations forces personnel are frequently exposed to blast forces, but the structural MRI correlates of cumulative blast exposure remain poorly defined. Purpose To determine the prevalence of structural brain MRI abnormalities in special operations forces personnel and examine their association with cumulative blast exposure, quantified using the generalized blast exposure value (GBEV). Materials and Methods This retrospective study included special operations forces personnel evaluated in the Comprehensive Brain Health and Trauma Program, or ComBHaT. All underwent 3-T brain MRI with time-of-flight MR angiography. Imaging findings were extracted from structured neuroradiology reports. Cumulative blast exposure was modeled as log₁₀ (GBEV + 1) (logGBEV). Associations between blast exposure and MRI findings were evaluated using Mann-Whitney U tests, Fisher exact tests, and multivariable logistic regression. Results A total of 564 personnel were evaluated (mean age, 43.3 years ± 9.1 [SD]; 563 male). The most prevalent MRI finding was white matter hyperintensities (215 of 564 participants [38.1%]), followed by intracranial aneurysms (33 of 564 [5.9%]). Among all evaluated MRI findings, only intracranial aneurysms were associated with cumulative blast exposure (mean logGBEV in participants with vs without aneurysms, 7.02 ± 1.06 vs 6.54 ± 0.98; P = .01). No association was observed for other structural abnormalities, including white matter hyperintensities (P = .82). Using a median split of logGBEV (high exposure, ≥6.55; low exposure, <6.55), aneurysm prevalence was greater in the high-exposure group (21 of 220 participants [9.5%]) compared with the low-exposure group (six of 220 [2.7%]) (P = .005; odds ratio, 3.76 [95% CI: 1.49, 9.52]; relative risk, 3.50 [95% CI: 1.44, 8.51]). In multivariable regression (n = 293), logGBEV remained independently associated with aneurysm presence (odds ratio, 1.81 [95% CI: 1.09, 3.03]; P = .02). Conclusion In this large military sample, intracranial aneurysms, but not other structural MRI findings, were independently associated with greater cumulative blast exposure.