Posterior circulation strokes (PCS) represent ~30% of all ischemic strokes, but existing prognostic tools are limited, especially for non-basilar artery occlusions. Accurate early outcome prediction may aid treatment decisions and clinical trial design. We developed and externally validated the Posterior Circulation Clot Burden Score (PC-CBS), a radiological tool to predict 3-month functional outcome in acute ischemic stroke due to posterior circulation occlusion.

Inclusion Criteria:

• age >18 years old
• admitted within 24h from last known well
• symptomatic arterial occlusion. The following arterial occlusions were eligible for inclusion: the extracranial vertebral artery between the V0 and V3 segments; the intracranial portion of the vertebral artery; the basilar artery either in its proximal, mid and/or distal segment, the P1 and/or the P2 segments of the posterior cerebral artery.

Exclusion Criteria:

• simultaneous clinical and/or radiological strokes in the posterior and anterior circulation

Patients suffering from an acute ischemic stroke (AIS) clinically and/or radiologically attributable to a posterior circulation arterial occlusion