The investigators initiated a multicenter, prospective, randomized, open label, blinded-endpoint (PROBE) controlled trial to evaluate the efficacy and safety of perfusion-guided endovascular treatment (EVT) compared to standard medical care for patients with acute ischemic stroke due to medium vessel occlusion (MeVO) within 24 hours from symptom onset.

Adult acute ischemic stroke patients due to primary medium vessel occlusions (non-dominant proximal M2 or mid-distal M2/M3 segments of the middle cerebral artery, A1/A2/A3 segments of the anterior cerebral artery, and P1/P2/P3 segments of the posterior cerebral artery) confirmed by CTA/MRA and responsible for the signs and symptoms of acute ischemic stroke with baseline National Institutes of Health Stroke Scale (NIHSS) ≥8 will be enrolled in this trial. The investigators use perfusion imaging to select subjects and the enrolled patients have target mismatch profile on CTP or MRI+PWI (ischemic core volume <70mL, mismatch ratio>1.2, mismatch volume >10mL). The eligible patients will be randomly assigned to receive endovascular treatment (EVT) +best medical treatment or best medical treatment within 24 hours after the time that the patient was last known to be well (including after stroke on awakening and unwitnessed stroke). The primary outcome is the proportion of patients with an mRS score ≤ 1 at 90 days.

Inclusion Criteria:

• Age≥18 years old;
• Acute ischemic stroke symptom onset within 24 hours; including wake-up stroke and unwitnessed stroke, onset time refers to "last-seen normal time";
• Primary medium vessel occlusions confirmed by CTA/MRA, including non-dominant proximal M2 or mid-distal M2/M3 segments of the middle cerebral artery (MCA), A1/A2/A3 segments of the anterior cerebral artery (ACA), and P1/P2/P3 segments of the posterior cerebral artery (PCA) and responsible for the signs and symptoms of acute ischemic stroke;
• Pre-stroke modified Rankin scale (mRS) score ≤1;
• Baseline National Institutes of Health Stroke Scale (NIHSS) ≥8;
• Neuroimaging criteria: Target mismatch profile on CT perfusion or MRI+MR perfusion (ischemic core volume <70 mL, mismatch rate >1.2, mismatch volume >10 mL);
• Written informed consent from patients or their legally authorized representatives.

Exclusion Criteria:

• Any evidence of intracranial hemorrhage on qualifying imaging;
• Known (serious) sensitivity to radiographic contrast agents, nickel, titanium metals or their alloys and unable to complete CTP/PWI;
• Known history of arterial tortuosity, pre-existing stent, other arterial disease and/or known disease at the arterial access site that would prevent the device from reaching the target vessel and/or preclude safe recovery after EVT;
• Radiological confirmed evidence of mass effect or intracranial tumour (except small meningioma);
• Clinical diagnosis of cerebral vasculitis;
• Evidence of vessel recanalization prior to randomisation;
• Severe comorbidities, which will likely prevent improvement or follow-up;
• Any terminal illness such that the patient would not be expected to survive more than 1 year;
• Hypodensity in >1/3 MCA territory on non-contrast CT or significant hypodensity outside the current perfusion lesion suggesting distal clot migration (secondary MeVO);
• Multiple arterial occlusion;
• Pregnant women, nursing mothers, or reluctance to use effective contraceptive measures during the period of the trial;
• Unlikely to adhere to the trial protocol or follow-up;
• Participation in other interventional clinical trials within the previous 3 months.