What does a DWI bright area with a corresponding absence on FLAIR indicate in acute stroke imaging?

What does a DWI bright area with a corresponding absence on FLAIR indicate in acute stroke imaging?

• A. DWI negative/FLAIR positive mismatch
• B. DWI bright/FLAIR negative mismatch
• C. DWI and FLAIR both bright
• D. DWI negative/FLAIR negative

Answer: (B)

In acute ischemic stroke, diffusion-weighted imaging (DWI) detects cytotoxic edema very early, often within minutes, so the affected tissue lights up on DWI. FLAIR changes, however, take longer to develop and may still be normal in the hyperacute hours after onset. A bright area on DWI with no corresponding bright signal on FLAIR is a diffusion–FLAIR mismatch. This pattern indicates very early ischemia, suggesting the onset was within a short time window (often within a few hours) and supports the diagnosis of an acute stroke in its earliest stage, with potential implications for timely reperfusion therapy. If both DWI and FLAIR are bright, the tissue changes are more established; if both are negative, there is no acute lesion; a DWI-negative with FLAIR-positive pattern is not typical of hyperacute stroke.

In acute ischemic stroke, diffusion-weighted imaging (DWI) detects cytotoxic edema very early, often within minutes, so the affected tissue lights up on DWI. FLAIR changes, however, take longer to develop and may still be normal in the hyperacute hours after onset. A bright area on DWI with no corresponding bright signal on FLAIR is a diffusion–FLAIR mismatch. This pattern indicates very early ischemia, suggesting the onset was within a short time window (often within a few hours) and supports the diagnosis of an acute stroke in its earliest stage, with potential implications for timely reperfusion therapy. If both DWI and FLAIR are bright, the tissue changes are more established; if both are negative, there is no acute lesion; a DWI-negative with FLAIR-positive pattern is not typical of hyperacute stroke.