Implementation of emergent MRI for wake-up stroke: a single-center experience.

Purpose: Recent updates in national guidelines for management of acute ischemic stroke in patients of unknown time of symptom onset ("wake-up" strokes) incorporate, for the first time, use of emergent MRI. In this retrospective case series, we analyze our experience at a Comprehensive Stroke Center implementing a new workflow including MRI in this clinical setting. This study also describes "DWI-FLAIR" mismatch, a critical concept for the interpretation of emergent brain MRIs performed for wake-up strokes.

Methods: Over a 14-month period, all brain MRIs for wake-up stroke were identified. The imaging was analyzed by two board-certified, fellowship-trained neuroradiologists, and a diagnosis of DWI-FLAIR mismatch was made by consensus. Process metrics assessed included interval between last known well time and brain imaging, interval between CT and MRI, and interval between brain MRI and interpretation.

Results: Sixteen patients with a history of "wake-up stroke" were identified. Thirteen of the 16 patients (81.3%) were found to have a DWI-FLAIR mismatch, suggesting infarct < 4.5 h old. The mean time between last known well and MRI was 7.89 h with mean interval between CT and MRI of 1.83 h. Forty-six percent of patients with DWI-FLAIR mismatch received intravenous thrombolysis.

Conclusion: In this "real world" assessment of incorporation of emergent MRI for wake-up strokes, there were several key factors to successful implementation of this new workflow, including effective and accurate description of MRI findings; close collaboration amongst stakeholders; 24/7 availability of MRI; and 24/7 onsite coverage by neurology and radiology physicians.