151 Bilateral vs Unilateral Middle Meningeal Artery Embolization for Unilateral Subdural Hematoma

INTRODUCTION: Middle meningeal artery embolization (MMAE) has emerged as an effective treatment for subdural hematoma (SDH), but the optimal embolization strategy for patients with unilateral SDH remains unclear. While unilateral embolization targets only the symptomatic side, bilateral embolization may provide additional protection and improve functional outcomes. METHODS: We conducted a retrospective multicenter analysis of patients with unilateral SDH who underwent MMAE between 2018-2024. Patients received either bilateral MMAE or unilateral MMAE. the primary endpoint was good functional outcome (modified Rankin Scale 0-2). Secondary endpoints included recurrence rates, composite success measures, and safety outcomes. Statistical analysis used inverse probability of treatment weighting (IPTW) to adjust for confounding factors including age, gender, SDH thickness, and anticoagulation status. RESULTS: A total of 996 patients with cSDH receiving bilateral MMAE in 119 and unilateral MMAE in 878 were included. After IPTW adjustment, bilateral MMAE demonstrated significantly superior composite outcomes compared to unilateral MMAE. The primary composite endpoint (good functional outcome mRS 0-2 plus no rescue surgery) was achieved in 69.6% of bilateral MMAE patients versus 53.8% of unilateral MMAE patients (absolute difference +15.8%, p=0.003; number needed to treat 6.3). Individual functional outcomes (mRS 0-2) were achieved in 71.8% versus 57.0% (p=0.004), while rescue surgery rates were 4.7% versus 2.5% (p=0.21). Both approaches achieved excellent procedural success with minimal complications. CONCLUSIONS: Bilateral MMAE significantly outperforms unilateral MMAE for unilateral SDH patients. These results favor bilateral embolization to enhance functional independence and minimize rescue interventions. Furthermore, this supports the theory regarding the formation of collaterals by the contralateral middle meningeal artery when not subjected to embolization.