Christensen S, et al. - In this study, researchers examined the data to evaluate if a persistent favorable perfusion profile existing in some cases beyond 24 hours from the onset and could be predicted by a lower baseline hypoperfusion intensity ratio indicating favorable collaterals. They noticed 18% of the control arm subjects had a persistent favorable profile >38 hours after last known well time. They also found 20% of cases with a middle cerebral artery or internal carotid artery occlusion, presented in an extended time window and were not treated with thrombectomy had a persistent mismatch for at least an additional 24 hours. They recorded that such candidates (with a favorable hypoperfusion intensity ratio at presentation) might experience delayed infarct expansion, and also had poor clinical outcomes.