• Götz Thomalla and Christian Gerloff.
• Klinik und Poliklinik für Neurologie, Kopf- und Neurozentrum, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
• Curr. Opin. Neurol. 2019 Aug 1; 32 (4): 521-529.

Purpose Of ReviewUntil recently, intravenous thrombolysis and mechanical thrombectomy for acute stroke treatment relied on reported information on the known time of symptom onset and was limited to treatment within a narrow time window. New trials have provided evidence for imaging-based effective reperfusion treatment in an extended time window and unknown-onset stroke. This review summarizes evidence from recent clinical trials and suggests a simple algorithm for the choice of imaging modalities to guide evidence-based reperfusion treatment of acute stroke.Recent FindingsTwo trials have provided evidence for benefit of mechanical thombectomy in patients with stroke from large vessel occlusion up to 24 h after symptom onset or with unknown symptom onset who have a small infarct core but large perfusion lesion or severe clinical deficit (DAWN, DEFUSE-3). An MRI-based trial has demonstrated the benefit of intravenous thrombolysis with alteplase in patients with unknown onset stroke who present with MRI findings of DWI-FLAIR mismatch (WAKE-UP). Another trial demonstrated benefit of intravenous alteplase in an extended or unknown time-window in patients with penumbral pattern on MRI or CT perfusion (EXTEND).SummaryIn stroke patients with unknown symptom onset or known symptom onset up to 24 h, advanced imaging with MRI or with CT perfusion can guide effective acute reperfusion treatment with mechanical thrombectomy and intravenous alteplase.

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