Recovery by Endovascular Salvage for Cerebral Ultra-acute Embolism (RESCUE)-Japan RCT

Inclusion Criteria: * Acute ischemic stroke patients who were treated with intravenous rt-PA therapy within 4.5 hours from onset and have persistent occlusion of IC and M1 proximal portion\* confirmed by cerebral angiography. \*: M1 proximal portion means the segment of MCA within 5mm from the internal carotid bifurcation. * Patients who can receive endovascular treatment within 8 hours after the onset. * Patients whose DWI-ASPECTS was 5 points and more, or CT-ASPECT was 6 points and more just before cerebral angiography. * Patients whose NIHSS is between 8 and 29 points. * Patients who are between 20 and 85 years. * Gender does not matter. * Consent of this study participants must be obtained from patients or legal representative in writing. Exclusion Criteria: * Patients whose neurological symptoms improved and NIHSS is eight points and less after intravenous rt-PA therapy. * Patients whose mRS was 3 points and more before the onset. 3)Patients with past history of lumbar puncture or arterial puncture that were difficult of hemostasis. * Patients with intracranial tumor * Patients with hypersensitivity to contrast agent. * Patients with serious renal disease. * Patients with malignant tumor. * Patients with pregnancy or suspect of pregnancy, or during lactation. * Patients with findings of acute myocardial infarction or pericarditis after myocardial infarction. * Patients who cannot be followed for 3 months. * Patients with past history of cerebral aneurysm, cerebral arteriovenous malformation, cerebral venous thrombosis, or moyamoya disease. * Patients with other occlusions besides ICA or M1 proximal portion. * Patients with aortic dissection complicating endovascular treatment. * Patients with tortuous arteries that prevent the navigation of the device to the target vessel. * Patients considered inappropriate to participate in the study.