Abstract Number: Esoc2026a168 Early Versus Late Mri for Detection of Posterior Circulation Stroke in Acute Isolated Continuous Dizziness: Results of the Provide Study

Abstract Background and aims The optimal MRI timing for detecting posterior circulation stroke (PCS) in patients with isolated acute-onset continuous dizziness (iAOCD) remains uncertain. Although MRI is the preferred imaging modality, up to 20% of PCS may be missed within the first 48 hours after symptom onset, yet supporting evidence remains limited. We assessed the additional diagnostic value of late MRI following a negative early MRI. Methods This analysis is part of the PROVIDE-study, a multicenter prospective cohort including 800 patients with iAOCD recruited from 11 centers in the Netherlands. A subset of patients underwent both an early MRI (48 hours after symptom onset) and a late MRI (72 hours). Late MRI was performed only when the early MRI revealed no central etiology. The imaging protocol included 3-mm diffusion-weighted-imaging and T2-weighted sequences. All scans were centrally reviewed by an experienced neuroradiologist. Results Late MRI was performed in 190 patients with a negative early MRI. No previously undetected infratentorial infarctions were identified. One late MRI showed an acute infarction in a clinically silent region in the right posterior cerebral artery territory. This finding was interpreted as asymptomatic new-onset ischemia rather than as a false-negative early MRI. The negative initial MRI can be explained by the short symptom duration (24 hours), a known factor associated with reduced MRI sensitivity. Conclusions In this prospective cohort of patients with iAOCD, late MRI did not provide additional diagnostic value after a negative early MRI. Clinical decision-making should rely on integrated clinical assessment and MRI, without routine use of late-phase imaging. Conflict of interest Merel Verhagen: nothing to disclose. Adriaan Ros: nothing to disclose. Vincent Klokman: nothing to disclose. Kim Jie: nothing to disclose. Meike Schoenmakers: nothing to disclose. Karlijn de Laat: nothing to disclose. Suzanne Cannegieter: nothing to disclose. Korné Jellema: nothing to disclose.