Which statement about DWI-FLAIR mismatch is true?

Which statement about DWI-FLAIR mismatch is true?

• A. It indicates delayed onset beyond 4.5 hours
• B. DWI positive/FLAIR negative mismatch is used to select patients for thrombolysis within 4.5 hours or with unclear onset
• C. It means there is no salvageable tissue
• D. It indicates infarct is hemorrhagic

Answer: (B)

DWI-FLAIR mismatch signals a very recent brain infarct and helps guide thrombolysis decisions when the exact onset is unknown or uncertain. Diffusion-weighted imaging (DWI) shows acute cytotoxic edema within minutes of stroke onset, while FLAIR changes appear later, typically after a few hours. If there is diffusion restriction but no corresponding FLAIR hyperintensity, the tissue is likely still in the early, potentially reversible stage, suggesting the patient may still be within the window for intravenous thrombolysis (within 4.5 hours) or for those with unclear onset. This is why the pattern is used to select patients for thrombolysis in those specific time scenarios. The other statements don’t fit because a delayed onset beyond 4.5 hours would more often show FLAIR positivity, lack of salvageable tissue isn’t indicated by a mismatch, and hemorrhagic infarct is a different complication not defined by this mismatch pattern.

DWI-FLAIR mismatch signals a very recent brain infarct and helps guide thrombolysis decisions when the exact onset is unknown or uncertain. Diffusion-weighted imaging (DWI) shows acute cytotoxic edema within minutes of stroke onset, while FLAIR changes appear later, typically after a few hours. If there is diffusion restriction but no corresponding FLAIR hyperintensity, the tissue is likely still in the early, potentially reversible stage, suggesting the patient may still be within the window for intravenous thrombolysis (within 4.5 hours) or for those with unclear onset. This is why the pattern is used to select patients for thrombolysis in those specific time scenarios. The other statements don’t fit because a delayed onset beyond 4.5 hours would more often show FLAIR positivity, lack of salvageable tissue isn’t indicated by a mismatch, and hemorrhagic infarct is a different complication not defined by this mismatch pattern.