Background Chronic subdural hematomas (cSDHs) are associated with high recurrence risks following surgical evacuation. The EMBOLISE trial demonstrated that, compared with surgery alone, adjunctive middle meningeal artery embolization (MMAE) significantly reduced reoperation rates. However, given the limitations of the clinical end points of the trial, which may be subject to interrater variability and certain biases, the quantitative imaging metrics need to be evaluated. Purpose To evaluate the prespecified imaging end points of the EMBOLISE trial and assess the long-term resolution of cSDH through quantitative imaging analyses. Materials and Methods EMBOLISE was a multicenter, randomized, interventional trial conducted across 39 U.S. sites between December 2020 and August 2023. Prespecified secondary imaging end points included changes in hematoma volume and thickness and midline shifts from 24 hours to 90 days after the procedure at CT and MRI. The post hoc analyses performed herein extended the assessment to 180 days and included absolute hematoma metrics. Mixed-effects modeling was employed to adjust for confounders. Results Four hundred patients were enrolled in the EMBOLISE study, among whom 352 were included (mean age, 72 years ± 10.4 SD; 256 men). The mean cSDH volume was 126 mL at screening, with no intergroup differences. At 90 and 180 days, the MMAE plus surgery group had lower cSDH volumes (20.6 mL vs 28.9 mL P = .03 and 19.4 mL vs 31.5 mL P = .04, respectively). Mixed-effects models revealed a 6.9 mL (95% CI: -13.5, -0.40; approximately 25%) greater volume reduction and an 8.4 mL (95% CI: -15.2, -1.6; approximately 30%) lower absolute volume at 90 days in the MMAE group There was no evidence of a difference in the prespecified secondary imaging end points between the groups. Conclusion While the prespecified secondary imaging end points did not significantly differ, the absolute 90- and 180-day hematoma volumes were significantly lower in patients who received MMAE and surgery. Confounder-adjusted mixed-effects analysis indicated a greater reduction in hematoma volume with adjunctive MMAE. ClinicalTrials.gov identifier NCT04402632 © RSNA, 2026 Supplemental material is available for this article. See also the editorial by Ramasamy and Baker in this issue.
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