The aim of this trial is to investigate whether head elevation position after endovascular treatment can improve the 90-day functional outcome of acute large vessel occlusion in the anterior circulation.

The optimal head position for patients with acute ischemic stroke (AIS) remains uncertain. The HeadPoS study revealed that there is no significant difference in disability outcomes between patients who are placed in a lying-flat position for 24 hours and those who are placed in a sitting-up position with the head elevated to at least 30 degrees for 24 hours. However, this study included both patients with ischemic and hemorrhagic strokes, and most of the patients had mild strokes (median National Institutes of Health Stroke Scale score of 4). It is unclear how to arrange the patient's head position after endovascular treatment.

The hypothesis of this trial: Compared with the lying flat head positioni, the head elevation position after endovascular treatment can significantly improve the 90-day functional outcome of acute large vessel occlusion in the anterior circulation.

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.