ABSTRACT NUMBER: ESOC2026YS156 FROM LEAKAGE TO LESIONS: BLOOD–BRAIN BARRIER DYSFUNCTION AS A PRECURSOR OF HEMORRHAGIC MARKERS IN CEREBRAL AMYLOID ANGIOPATHY

Abstract Background and aims Blood–brain barrier (BBB) dysfunction may play an important role in hemorrhagic manifestations of cerebral amyloid angiopathy (CAA), with contrast leakage on MRI serving as a marker of BBB disruption. Previous case reports and small cross-sectional studies suggest that focal contrast enhancement on post-contrast FLAIR imaging may indicate locally increased vascular vulnerability. Our aim was to assess whether in patients with CAA, new cerebral microbleeds (CMBs) or cortical superficial siderosis (cSS) develop during follow up at locations with contrast enhancement on a preceding MRI. Methods We included patients with CAA from 2 prospectively collected cohorts (FOCAS, FETCH) who underwent baseline contrast-enhanced MRI (3T or 7T) and follow-up susceptibility-weighted imaging. Enhancement sites were visually identified on baseline post-contrast FLAIR and co-registered to follow-up scans. New CMBs or cSS foci were documented on follow up. The primary outcome was the percentage of enhancement sites developing new CMB/cSS. Secondary outcomes included the proportion of new hemorrhagic markers arising outside enhancement regions. Results Nineteen patients with CAA were included. Follow-up susceptibility-weighted imaging was available after a median interval of 11 months (range 2–36). Preliminary analyses indicated that, in patients with CAA, new CMBs/cSS develop at the exact locations of focal contrast enhancement on a preceding MRI. Image assessment is ongoing. Interim findings suggest that focal contrast enhancement may indicate localized vulnerability for future hemorrhagic lesion formation in CAA. Dual-rater scoring and completion of follow-up imaging will determine the robustness of this spatial association. Conflict of interest Prof. Wermer reports independent support from the Dutch Research Council (NWO), ZonMw (VIDI grant 91717337), the Dutch Heart Foundation (Dekker grant 2016T086), and the Dutch CAA foundation. Prof Klijn is PI of DIST (www.dutch-ich.nl), which is part of the CONTRAST consortium, and supported by a Promising Care funding scheme grant of the National Health Care Institute and ZonMw (2021038368) and an unrestricted research grant of Penumbra Inc, to Radboudumc and Erasmusmc. All other authors have nothing to disclose.