A prospective, multicenter, open-label, blinded-endpoint, randomized controlled trial to evaluate whether best medical management (BMM) combined with endovascular therapy (EVT) improves neurological outcomes compared to BMM alone in patients with progressive acute mild ischemic stroke due to basilar artery occlusion within an extended time window.

This trial aims to evaluate whether best medical management (BMM) combined with endovascular therapy (EVT) improves neurological outcomes compared to BMM alone in patients with progressive acute mild ischemic stroke due to basilar artery occlusion within an extended time window. The study used a stratified block randomization method, with stratification by center. A central randomization system was used to assign subjects to the experimental group and the control group in a 2:1 ratio for each center.

Inclusion Criteria:

1. Age ≥18 years.
2. Symptoms and signs consistent with basilar artery ischemia.
3. Basilar artery or vertebral artery occlusion confirmed by computed tomography angiography (CTA), magnetic resonance angiography (MRA), or digital subtraction angiography (DSA); if vertebral artery occlusion is present, it should completely block blood flow along the basilar artery.
4. First-time onset meeting the criteria for mild ischemic stroke diagnosis: NIHSS score <6.
5. Symptom progression within 7 days of the first onset.
6. Symptom progression: NIHSS score increase ≥4 points or consciousness level increase ≥2 points from the initial NIHSS score.
7. Time from symptom onset to randomization >24 hours.
8. Symptom progression to randomization time ≤24 hours.
9. NIHSS score ≥10 before randomization.
10. pc-ASPECTS before randomization ≥ 6
11. The patient or their family members are willing to comply with the protocol requirements and data collection procedures, understand, and sign the informed consent form.

Exclusion Criteria:

1. Symptom progression due to intracranial hemorrhage, brain edema, or other clear causes (including but not limited to infarct hemorrhagic transformation, new infarction in non-occluded vascular regions, severe infection, high fever, heart or kidney dysfunction, hypovolemia, or severe electrolyte disturbances).
2. mRS >2.
3. Factors in the target vessel that are expected to prevent completion of endovascular treatment.
4. Multiple vessel occlusions.
5. Prior imaging confirmed or investigator-assessed chronic basilar artery occlusion.
6. Presence of untreated intracranial aneurysms, intracranial tumors (except small meningiomas), or intracranial vascular malformations.
7. Intracranial hemorrhage within the past 6 months, including parenchymal brain hemorrhage, intraventricular hemorrhage, or subarachnoid hemorrhage.
8. Gastrointestinal or urinary tract bleeding, acute myocardial infarction, cranial trauma, or major surgery within the past month.
9. Presence of active bleeding, coagulation disorders, or uncorrectable bleeding tendencies.
10. Platelet count <40×10^9/L, or INR >2 during anticoagulation therapy (irreversible).
11. Severe heart, liver, or kidney dysfunction or other severe systemic late-stage diseases.
12. Known allergy to iodine contrast agents or other treatment-related drugs.
13. Medically uncontrolled refractory hypertension (defined as persistent systolic blood pressure >185 mmHg or diastolic blood pressure >110 mmHg) (Note: Participants can be included if their blood pressure is controllable with medication and maintained at an acceptable level).
14. Uncontrollable blood glucose <2.8 mmol/L or >22.2 mmol/L.
15. Pregnancy or breastfeeding.
16. Life expectancy <6 months.
17. Participation in other clinical studies that may affect outcome assessment.
18. Investigator's judgment that the patient is unsuitable for participation in this study or may face significant risks (e.g., due to mental illness, cognitive, or emotional disorders preventing understanding and/or compliance with study procedures and/or follow-up).