Supplementary Material for: Emergency MRI as the First Imaging Modality in Acute Stroke: Effect on Diagnostic Performance and Outcomes

Introduction: Whether shifting from CT to MRI as the initial diagnostic approach in emergency assessment may offer an advantage in acute stroke care remains unclear. We sought to evaluate the impact of the MRI-first paradigm on diagnosis, workflow, and clinical outcomes in a comprehensive stroke center. Methods: In this retrospective analysis of a prospective observational cohort, consecutive patients admitted within 24 hours after onset or last known well and with diagnosis of acute ischemic stroke, intracerebral hemorrhage (ICH), or transient ischemic attack (TIA) at the emergency department before (July 2022 to March 2023) and after the implementation of an MRI paradigm (April 2023 to January 2024) were included. We compared the diagnostic performance, workflow metrics, and 3-month modified Rankin Scale (mRS) between CT-first and MRI-first paradigms. Results: A total of 478 patients in the CT-first group and 488 patients in the MRI-first group with initial diagnosis of acute stroke or TIA were included. The concordance of stroke diagnosis was improved after implementation of MRI-first paradigm (95.7% [95% CI 93.9%-97.5%] vs 91.2% [95% CI 88.7%-93.7%], P=0.003). Despite a lower rate of thrombolysis and slightly prolonged door-to-needle time, fewer cases of stroke mimics were treated by thrombolysis. MRI-first paradigm was associated with favorable shift in mRS (adjusted common odds ratio [cOR] 0.65, 95% confidence interval [CI] 0.51-0.84) at three months among all patients with final diagnosis of any acute stroke or TIA. MRI-first paradigm was specifically related to favorable outcome (adjusted cOR 0.61, 95% CI 0.45-0.83) among patients with cerebral ischemia. MRI-first paradigm was not associated with functional outcomes among ICH patients. Conclusion: Implementing MRI as the first imaging modality in emergency assessment of stroke is feasible and associated with favorable clinical outcomes for cerebral ischemia.