Influence of the circle of Willis on leptomeningeal collateral flow in anterior circulation occlusive stroke: Friend or foe?

Abstract

Background: Clinical outcome after large vessel occlusion (LVO) stroke depends on collateral integrity. We aimed to evaluate whether the completeness of the circle of Willis (CoW) and anterior temporal artery (ATA) determines the status of leptomeningeal collaterals (LC) in patients with acute LVO (internal carotid artery (ICA) and middle cerebral artery M1 (MCA) occlusion) treated with endovascular thrombectomy.

Patients and methods: LC, cross-flow through the anterior communicating artery (ACoA), presence of the ipsilateral posterior communicating artery (IpsiPCoA) and presence of the ATA were evaluated using CT angiography. LC was graded as good when ≥50% collateral filling was noted compared to the unaffected hemisphere.

Results: We included 159 patients with a median age of 75 years (IQR 63-82), MCA M1 occlusion in 96 (60%) and good outcome in 68 (45.6%). The LC were good in 129 (81.1%) patients. Complete IpsiPCoA and incomplete ACoA status was inversely associated with good LC in LVO (OR 0.51 (95% CI 0.02-0.07)). A complete CoW was associated with good LC in ICA occlusions, OR 8.4 (p = .025). Good outcome (modified Rankin scale 0-2 at 3 months) was associated with good LC (OR 5.63 (95% CI 1.11-28.4)), small ischemic lesion volume (OR 0.94 (95% CI 0.97-0.98)) and absence of the ACoA and IpsiPCoA (OR 4.47 (95% CI 1.09-18.3)).

Conclusions: ATA presence was associated with good leptomeningeal collaterals in LVO (OR 8.13 (95% CI 1.69-39.0)) and in MCA M1 patients (OR 7.9 (95% CI 1.7-36.4)). The effect of ATA was most pronounced in MCA M1 occlusions, and that of ACoA was most pronounced in ICA occlusions.

Keywords: Anterior temporal artery; Circle of Willis; Collateralization; Ischemic stroke; Thrombectomy.