ABSTRACT NUMBER: ESOC2026A2471 PROGNOSTIC UTILITY OF DIFFUSION-WEIGHTED MRI IN POSTERIOR VERSUS ANTERIOR CIRCULATION MINOR ISCHAEMIC STROKE: A POPULATION-BASED STUDY

Abstract Background and aims Diffusion-weighted imaging (DWI) is less sensitive to minor ischaemic stroke (MIS) in the posterior circulation (PC-MIS) versus in anterior circulation events (AC-MIS), potentially risking under-treatment of PC-MIS by non-specialists. However, it uncertain whether patients with DWI-negative PC-MIS have a high risk of recurrent stroke. In the absence of previous prospective studies, we aimed to determine the prognosis of PC-MIS in relation to DWI findings. Methods In a UK population-study based study of all vascular events, consecutive eligible patients with MIS (NIHSS≤3 at first assessment) underwent brain MRI/DWI before any recurrent event. Vascular territory was determined based on symptoms/examination/imaging. Risks of recurrent stroke at 90-days and at 90-days to 3-years follow-up were stratified by vascular territory and DWI-findings and adjusted for age and sex. Results Among 809 patients with MIS (343 PC-MIS; 466 AC-MIS), 452 (55.9%) were DWI-negative. PC-MIS were more frequently DWI-negative than AC-MIS (237/343 vs 215/466; OR=2.6;95%CI=2.0–3.5;p<0.001). However, although a positive DWI predicted 90-day stroke risk irrespective of vascular territory (overall aHR=7.8,1.76-34.9,p=0.007), it was a poor predictor of the subsequent 3-year risk (aHR=1.39,0.79-2.47,p=0.25), driven particularly by lack of predictive value in patients with PC-MIS (aHR=1.07,0.43-2.67,p=0.88). Conclusions DWI is often negative in suspected PC-MIS, but although patients with a positive DWI have an increased early risk of recurrent stroke, normal imaging does not indicate a low long-term risk. Treatment decisions in patients with PC-MIS should reflect the low sensitivity of DWI and the poor long-term predictive value. Conflict of interest Nothing to disclose