ABSTRACT NUMBER: ESOC2026A2224 BLOOD-BRAIN BARRIER PERMEABILITY AS A MECHANISTIC MEDIATOR OF EARLY PARENCHYMAL HEMORRHAGE AFTER MECHANICAL THROMBECTOMY

Abstract Background and aims Hemorrhagic transformation (HT), particularly parenchymal hemorrhage (PH), is a severe complication after endovascular treatment (EVT). This study evaluates blood-brain barrier (BBB) permeability as a predictor of hemorrhage Methods We included patients who achieved mTICI 2B-3 recanalization after EVT for an acute ischemic stroke due to large vessel occlusion from the French MISO and Spanish FURIAS cohorts. All patients underwent MRI pre-EVT and immediately post-EVT (early post-EVT). BBB permeability was assessed for both acquisitions using dynamic susceptibility contrast (DSC) MRI. HT was evaluated was classified by two independent expert raters using ECASS criteria on immediate post-procedural SWI (early HT) and 24-hour follow-up imaging (final HT). Statistical analysis included multivariate regression, mediation analysis to explore the core-volume/PH relationship, and Net Reclassification Improvement (NRI) for clinical utility. Results In 85 patients (median age 74), early and final HT prevalence was 32% and 40.5%, respectively. Distal (M2) occlusions independently predicted lower pre-EVT BBB leakage compared to M1 (OR 0.44, p=0.011). Pre-EVT BBB permeability was a significant independent predictor of early PH (OR 1.27, p=0.011). Mediation analysis confirmed that BBB disruption accounted for 44.5% of the effect of ischemic core volume on early PH (p=0.038). Furthermore, integrating pre-EVT BBB significantly improved risk reclassification for early PH (NRI 0.940, p=0.034). Conclusions BBB permeability, measured with DSC-MRI, represents a critical mechanistic link between infarct size and PH. Pre-EVT BBB disruption independently predicts hemorrhagic complications, providing superior risk stratification compared to core volume alone. Conflict of interest Nothing to disclose