Rationale: Recently, two prospective multicenter RCT reported a potential beneficial effect of endovascular thrombectomy (EVT) in patients with an acute symptomatic basilar artery occlusion (BAO). However, the high rate of crossover in BEST study and the long-term of recruitment in BASICS study influenced the validity of the results. Besides, a recently prospective clinical registry with large sample size (BASILAR) showed a significantly beneficial effect of EVT in BAO patients.

Objective: To assess the effect of EVT in addition to best medical management (BMM) compared to BMM alone, in patients with BAO, caused by a CTA/MRA confirmed occlusion of the basilar artery on functional and safety outcome.

Study design: This is a parallel group, randomized clinical trial of EVT with BMM versus BMM. The trial has observer blind assessment of the primary outcome and of neuro-imaging at baseline and follow up.

Study population: Patients with acute ischemic stroke and a confirmed basilar artery occlusion by CTA/MRA.

Main study parameters/outcomes: The primary effect parameter will be favourable outcome at day 90 defined as a modified Rankin Score (mRS) of 0-3. The estimate will be adjusted for the known prognostic variables age, pre-stroke mRS, time from onset to randomization, stroke severity (NIHSS) and collaterals and adjusted and unadjusted estimates with corresponding 95% confidence intervals will be reported.

Inclusion Criteria

1. Symptoms and signs compatible with ischemia in the basilar artery territory；
2. Basilar artery occlusion confirmed by CTA/MRA/DSA；
3. Age of 18 years or older；
4. Time from stroke onset to randomization within 12 hours of estimated time of basilar artery occlusion (defined as the sudden onset of stroke symptoms consistent with acute occlusion of the basilar artery (e.g. not considering any previous minor prodromal symptoms) as adjudicated by two local experienced neurologists). If symptoms of sudden deterioration are not witnessed (e.g. wake-up or unwitnessed strokes) the time that the patient was last known to be without any major neurological deficits (such as moderate or severe weakness, stupor, coma) will be used as the time of stroke onset.
5. Written informed consent;
6. National Institutes of Health Stroke Scale (NIHSS) score ≥10 at the time of neuroimaging Exclusion criteria

1. Pre-existing dependency with mRS ≥3 for patients<80 years; premorbid mRS≥1 for patients≥80 years； 2. bilateral mydriasis; 3. Pregnancy; if a woman is of childbearing potential a urine or serum beta HCG test is positive; 4. Severe contrast allergy or absolute contraindication to iodinated contrast; 5. Participation in other clinical trials; 6. Systolic pressure >185 mmHg or diastolic pressure >110 mmHg, and cannot be controlled by antihypertensive drugs; 7. Known genetic or acquired bleeding constitution, lack of anticoagulant factors, or oral anticoagulant drugs and INR > 1.7; 8. Blood glucose < 2.7 or >22.2 mmol / L; platelet count < 50×109 / L, or hematocrit < 25%; 9. Life expectancy < 1 year； 10. Patients that cannot complete 90-day follow-up (e.g. no fixed residence, overseas patients, etc.)； 11. Acute ischemic cerebral infarction within 48 hours after major surgery (patients can be enrolled if more than 48 hours); 12. Premorbid cerebrovascular inflammation; 13. Premorbid nervous system disease or mental disorders hindering the assessment of the disease; Imaging exclusion criteria

1. CT/MR shows intracranial hemorrhage (patients with microbleeds on MR can be included if lesion diameter ≤5mm);
2. CTA/MRA/DSA shows the artery is seriously tortuous, variability or dissection, and thrombectomy device cannot reach the target vessel;
3. PC-ASPECTS on CT/CTA-Source Images/MRI-DWI <6 for patients<80 years (<8 for patients ≥80 years);
4. CT or MR shows the cerebellar infarction with obvious space occupying effect and obvious compression of the fourth ventricle;
5. Complete bilateral thalami or bilateral brainstem infarction confirmed by CT/MR;
6. Occlusion of both anterior and posterior circulation confirmed by CTA/MRA/DSA;
7. Intracranial tumors (except small meningiomas).