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.