Head Position After Endovascular Therapy

Inclusion Criteria: 1. Clinical signs consistent with acute ischemic stroke; 2. Age ≥ 18 years old; 3. Proved anterior circulation large vessel occlusion on digital subtraction angiography (ICA, M1, M2) with/without cervical lesion (tandem); 4. NIHSS score ≥ 8 points before endovascular treatment; 5. ASPECTS score ≤ 7 points before endovascular treatment; 6. Successful vessel recanalization after endovascular treatment (defined as an eTICI score of 2b, 2c, or 3) ； 7. The time from onset to randomization ≤ 24 hours (the onset time is defined as the last normal time); 8. Written informed consent is obtained from patients and/or their legal representatives. Exclusion Criteria: 1. Pre-stroke mRS score\>1 point; 2. Patients with acute occlusions in multiple vascular territories (e.g. bilateral anterior circulation, or anterior/posterior circulation); 3. Currently in pregnant or lactating or serum beta HCG test is positive on admission; 4. Contraindications to a flat head position; 5. Any terminal illness with life expectancy less than 6 months; 6. Participating in other clinical trials; 7. Patients with a preexisting neurological or psychiatric disease that would confound the neurological functional evaluations; 8. Unlikely to be available for 90-day follow-up.