ABSTRACT NUMBER: ESOC2026YS216 MRI PHENOTYPE AND NIHSS SUBDOMAINS PREDICT NEGATIVE CT PERFUSION IN DWI-POSITIVE ACUTE ISCHAEMIC STROKE

Abstract Background and aims CT perfusion (CTP) may be negative or show a perfusion deficit in the wrong territory despite diffusion-weighted imaging (DWI)–positive MRI. We sought determinants of CTP negativity and territorial mismatch, and whether NIHSS subdomains add value beyond total NIHSS. Methods Retrospective cohort of consecutive clinical CTP (Oct 2024–Dec 2025) from two acute stroke centres. Patients were included if MRI was performed within 7 days of CTP (≤8 calendar days) and was DWI-positive. MRI was reported using a structured proforma and radiological variables were extracted. Multivariable logistic regression with 5-fold cross-validation reported AUC (mean, 95% CI). Outcomes were: (i) negative vs positive CTP (excluding wrong-area), and (ii) wrong-area vs correct-area CTP positivity. Results Of 722 CTP studies, 268 had MRI within 8 days; 159 were DWI-positive and included. For negative vs positive CTP, discrimination improved from clinical-only AUC 0.692 (0.518–0.865) to 0.777 (0.613–0.941) after adding MRI phenotype variables. For wrong-area vs correct-area CTP positivity, AUC improved from 0.624 (0.422–0.826) to 0.711 (0.477–0.946) with MRI variables. After adjustment for age, timing and MRI phenotype, adding NIHSS Visual/Gaze improved AUC from 0.772 (0.652–0.892) to 0.806 (0.712–0.900), exceeding the incremental value of total NIHSS. Conclusions Small, deep and/or single infarcts can yield misleading CTP - a negative or discordant CTP should not reassure when infarction is suspected. Conflict of interest Kausik Chatterjee: nothing to declare, Adam Seed: nothing to declare; Fathalla Elnagi: nothing to declare; NANA GYIMAH-KESSIE: nothing to declare Figure 1 - belongs to Methods Figure 2 - belongs to Results