ABSTRACT NUMBER: ESOC2026A2139 CHOROID PLEXUS ENLARGEMENT AFTER SPONTANEOUS SUBARACHNOID HEMORRHAGE: LONGITUDINAL CHANGES AND ASSOCIATIONS WITH CLINICAL AND COGNITIVE OUTCOMES

Abstract Background and aims The choroid plexus (CP) is a key interface for cerebrospinal fluid regulation and neuroinflammatory signaling. However, its structural evolution and clinical relevance after spontaneous subarachnoid hemorrhage (SAH) remain poorly characterized. Methods A retrospective cohort of 239 spontaneous SAH patients and 30 age and sex-matched controls was included. In SAH subjects, choroid plexus volume was quantified on 3T-MRI in the acute phase (T3) and at 90 days (T90). CP volumes were compared between patients and controls, and longitudinal changes in SAH cases were assessed using linear mixed-effects models. Associations with functional outcome, measured by the modified Rankin Scale at day 90, were analyzed using ordinal logistic regression. Associations with cognitive performance, including the Montreal Cognitive Assessment and Trail Making Tests A and B, were evaluated using multivariable linear regression. The models were adjusted for age, sex, WFNS grade, modified Fisher scale, hypertension, hydrocephalus, and aneurysm presence. Results CP volume was significantly higher in SAH patients compared with controls at all time points and increased significantly over time. In adjusted models, both CP volume at T90 (aORx100mm3=1.09; 95%CI=1.04-1.14; p=0.0006) and longitudinal CP volume increase from T3 to T90 (OR=1.08; 95%CI=1.02-1.15; p=0.0076) were associated with worse functional outcome. Longitudinal CP volume increase was also associated with executive dysfunction (β-value for logTM-B time=0.015; p=0.047). Conclusions After SAH, dynamic increases in CP volume, rather than acute size, are associated with worse functional recovery and executive dysfunction. These findings identify longitudinal CP changes as a potential imaging marker of recovery processes after SAH. Conflict of interest Paula Roset: nothing to disclose. Inés Bartolomé: nothing to disclose. Daniel Santana: nothing to disclose. Alejandra Mosteiro: nothing to disclose. Ramon Torné: nothing to disclose. Mariano Werner: nothing to disclose. Carlos Laredo: nothing to disclose. Emma Muñoz: nothing to disclose. Laura Llull: nothing to disclose. Sergio Amaro: nothing to disclose.