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Wake-Up Stroke DWI-FLAIR — RACP Adult Medicine MCQ

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HardNeurologyWake-Up Stroke DWI-FLAIRRACP Adult Medicine

A 75-year-old man wakes at 7 AM with left hemiparesis. He was last seen normal at 10 PM the previous night (9 hours ago). CT shows no haemorrhage. MRI DWI shows a right MCA territory infarct. MRI FLAIR is negative (DWI-FLAIR mismatch). CTA shows right MCA M1 occlusion. What does the DWI-FLAIR mismatch indicate?

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Correct answer: E — IV alteplase (0.9 mg/kg, 10% bolus then 60 min infusion)

DWI-FLAIR mismatch (DWI positive but FLAIR negative) indicates the stroke is likely <4.5 hours old despite an unknown onset time (WAKE-UP trial). This allows thrombolysis in wake-up strokes that would otherwise be excluded by the time window. DWI shows acute cytotoxic oedema (immediate), while FLAIR shows vasogenic oedema (develops after 4-6 hours). Additionally, with LVO, thrombectomy is indicated based on perfusion imaging.

Reference: WAKE-UP Trial; Stroke Foundation Australia 2024