What imaging features justify thrombectomy in the 6–24 hour window?

What imaging features justify thrombectomy in the 6–24 hour window?

• A. Large vessel occlusion with perfusion imaging showing a favorable mismatch (penumbra) or meeting DAWN/DEFUSE-3 criteria
• B. Ischemic changes on CT within 1 hour
• C. Any stroke with symptoms persisting >12 hours
• D. Small vessel occlusion and no penumbra

Answer: (A)

In the 6–24 hour window, deciding on thrombectomy isn’t about the clock alone—it hinges on imaging that shows there is still brain tissue that can be saved. The key feature is a large vessel occlusion with a favorable mismatch on perfusion imaging: a small infarct core (dead tissue) surrounded by a larger area of salvageable tissue (penumbra) that is at risk but can be saved with reperfusion. This tissue-based evidence is what makes thrombectomy worthwhile despite the later time. An alternative way this decision is made is by meeting DAWN or DEFUSE-3 criteria, which combine the patient’s clinical deficit with imaging findings to identify those who still have meaningful tissue at risk even after several hours. In both approaches, the important point is that there is still salvageable brain tissue that can be protected by removing the clot. By contrast, simply seeing ischemic changes on CT within a short time frame, or treating based only on elapsed time without evidence of a penumbra, does not justify thrombectomy in this extended window. Likewise, if the occlusion is in a small vessel with no penumbra, there’s little to gain from extraction.

In the 6–24 hour window, deciding on thrombectomy isn’t about the clock alone—it hinges on imaging that shows there is still brain tissue that can be saved. The key feature is a large vessel occlusion with a favorable mismatch on perfusion imaging: a small infarct core (dead tissue) surrounded by a larger area of salvageable tissue (penumbra) that is at risk but can be saved with reperfusion. This tissue-based evidence is what makes thrombectomy worthwhile despite the later time.

An alternative way this decision is made is by meeting DAWN or DEFUSE-3 criteria, which combine the patient’s clinical deficit with imaging findings to identify those who still have meaningful tissue at risk even after several hours. In both approaches, the important point is that there is still salvageable brain tissue that can be protected by removing the clot.

By contrast, simply seeing ischemic changes on CT within a short time frame, or treating based only on elapsed time without evidence of a penumbra, does not justify thrombectomy in this extended window. Likewise, if the occlusion is in a small vessel with no penumbra, there’s little to gain from extraction.