Hypoperfusion-hypodensity Mismatch for the Identification of Patients With Stroke Within 4.5 Hours

Inclusion Criteria: * acute ischemic stroke * evidence of acute intracranial vessel occlusion (any supratentorial proximal or peripheral artery of the anterior cerebral artery, middle cerebral artery or posterior cerebral artery territory) by CT hyper dense thrombus and/or CTangiography vessel occlusion and/or by ischemic perfusion deficit * evidence for acute ischemic perfusion deficit, i.e. acute symptoms attributable to ischemic CT perfusion lesion * complete native CT and CTperfusion performed on admission * sufficient CT and CTperfusion quality for judgement of acute ischemic hypodensity * known time of symptom onset. Exclusion Criteria: * None