Importance: Chronic subdural hematomas commonly recur after surgical drainage. The effect of adjunctive embolization of the middle meningeal artery (EMMA) on recurrence risk remains unclear. Objective: To evaluate whether EMMA as an adjunct to surgical drainage reduces chronic subdural hematoma recurrence compared with surgery alone. Design, Setting, and Participants: This trial was a randomized, open-label, blinded-end point trial involving adults with unilateral, symptomatic chronic subdural hematoma (≥10 mm) undergoing surgical drainage across 9 tertiary care centers in Canada between August 2021 and April 2025. Intervention: EMMA using a liquid embolic agent (Onyx-18) within 72 hours after surgical drainage vs a control group that did not receive EMMA after surgical drainage. Main Outcomes and Measures: Primary outcome was symptomatic recurrence of chronic subdural hematoma detected on computed tomographic (CT) scan at 90 days (range, 60 to 120 days). Secondary outcomes included radiographic recurrence of chronic subdural hematoma, 90-day mortality, and serious adverse events. The last date of follow-up was July 27, 2025. Results: Of 192 randomized participants, 186 (mean age, 71.8 years; 136 male 73%) completed the trial (93 per group). The primary outcome of symptomatic recurrence of chronic subdural hematoma detected on CT scan occurred in 4 participants (4.3%) in the EMMA group vs 26 patients (28%) in the control group (risk difference, -23.7; 95% CI, -34.1 to -13.9; P < .001). Radiographic recurrence occurred in 13 participants (14%) in the EMMA group vs 46 patients (49.5%) in the control group. Mortality was 4.3% vs 1.1%; serious adverse events occurred in 8.6% vs 5.4%, respectively. Conclusions and Relevance: Adjunctive EMMA after surgical drainage significantly reduced symptomatic recurrence on CT scan of unilateral chronic subdural hematoma at 90 days compared with surgery alone. Trial Registration: ClinicalTrials.gov Identifier: NCT04750200.
Shankar et al. (2026) studied this question.