This multicenter retrospective registry study evaluates the safety and effectiveness of endovascular therapy versus medical therapy for acute large-core basilar artery occlusion. It also investigates clinical, imaging, and laboratory factors associated with functional outcomes and mortality. Patients are grouped according to the treatment received in routine clinical practice.

Inclusion Criteria:

1. Age ≥18 years, men or women.
2. Occlusion (TIMI 0-1) of the basilar artery or intracranial segments of both vertebral arteries (V4) as evidenced by CTA/MRA/DSA.
3. Time from symptom onset (or last known well) to treatment (endovascular therapy or medical therapy) ≤7 days.
4. Patients with large core infarction in the posterior circulation, defined as a posterior circulation Acute Stroke Prognosis Early CT score (pc-ASPECTS) score of 0-5 on CT angiography source images or MR with diffusion-weighted imaging or non-contrast CT.

Exclusion Criteria:

1. Subjects with occlusions in both anterior and posterior circulation.
2. CT or MR evidence of hemorrhage (the presence of microbleeds on MRI is allowed).
3. Missing key clinical information (e.g., unavailable baseline NIHSS, unclear symptom onset/last known well time, or missing major treatment information including whether EVT was performed).
4. Baseline NIHSS score <6.
5. Woman of childbearing potential who is known to be pregnant or lactating or who has a positive pregnancy test on admission.
6. Missing follow-up outcomes at 90 days.
7. Any other condition judged by investigators to substantially affect analysis or interpretation.

Adults (≥18 years) with imaging-confirmed acute vertebrobasilar occlusion and large-core infarction (pc-ASPECTS 0-5) treated within 7 days of symptom onset/last known well at participating centers in China. Patients are identified retrospectively from routine clinical practice and classified according to treatment received: endovascular therapy plus standard medical management versus standard medical management alone.

The study is proceeding.