Collateral status predicts functional outcome in early-treated large-core anterior circulation stroke

Background and purpose: Endovascular therapy (EVT) is increasingly offered to patients with large-core acute ischemic stroke (AIS), yet outcomes remain highly heterogeneous. Collateral circulation may be a key determinant of infarct evolution and recovery, but its role in early-window large-core stroke is not fully defined. Methods: We retrospectively analyzed consecutive adults from a prospective stroke registry who presented within 6 h with anterior-circulation large-vessel occlusion, NIHSS ≥6, and a large ischemic core (MRI core >50 mL or CT perfusion core >70 mL, up to 150 mL). All patients received reperfusion therapy (intravenous thrombolysis, EVT, or both). Collateral status on baseline single-phase CTA was graded using the Tan scale (0-3); no patients had grade 3. The primary outcome was 90-day modified Rankin Scale (mRS); secondary outcome was NIHSS at discharge. Results: = 0.003). Conclusion: In early-treated large-core AIS, even simple CTA-based collateral assessment strongly predicts recovery. Patients with absent collaterals follow a distinctly poorer trajectory, while those with any collateral filling behave more favorably. Incorporating collateral status into routine evaluation may improve prognostic accuracy and support treatment decisions in this challenging subgroup.