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Updated: Oct 31, 2025
A Magnetic Resonance Imaging Protocol for Stroke Onset Time Estimation in Permanent Cerebral Ischemia
Published on: September 16, 2017
Implementation of emergent MRI for wake-up stroke: a single-center experience
Matthew H Kulzer1, Warren Chang1, Russell Cerejo2
1Division of Neuroradiology, Imaging Institute, Allegheny Health Network, 320 E. North Ave, Pittsburgh, PA, USA.
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.
Insights
Emergent MRI, including DWI-FLAIR mismatch, is effective for diagnosing wake-up strokes. Successful implementation requires 24/7 availability and collaboration among stroke specialists.
Area of Science:
- Neurology
- Radiology
- Stroke Medicine
Background:
- National guidelines now include emergent MRI for wake-up strokes.
- Wake-up strokes present diagnostic challenges due to unknown symptom onset times.
- A DWI-FLAIR mismatch is a key concept for interpreting emergent MRIs in these cases.
Purpose of the Study:
- To analyze the implementation of a new workflow using emergent MRI for wake-up strokes.
- To describe the DWI-FLAIR mismatch concept in the context of emergent MRI for wake-up strokes.
- To evaluate the effectiveness of emergent MRI in a Comprehensive Stroke Center setting.
Main Methods:
- Retrospective case series of 16 patients with wake-up strokes over 14 months.
- Analysis of brain MRIs by two fellowship-trained neuroradiologists.
- Assessment of process metrics including time intervals and DWI-FLAIR mismatch diagnosis.
Main Results:
- 13 out of 16 patients (81.3%) showed a DWI-FLAIR mismatch, indicating infarct < 4.5 hours old.
- Mean time from last known well to MRI was 7.89 hours.
- 46% of patients with DWI-FLAIR mismatch received intravenous thrombolysis.
Conclusions:
- Successful implementation of emergent MRI for wake-up strokes depends on accurate MRI interpretation and stakeholder collaboration.
- 24/7 availability of MRI and onsite neurology/radiology coverage are crucial.
- This workflow facilitates timely diagnosis and treatment for wake-up stroke patients.
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