Plasticity of Circle of Willis: A Longitudinal Observation of Flow Patterns in the Circle of Willis One Week after Stenting for Severe Internal Carotid Artery Stenosis

Abstract

Background and Purpose: The purpose of the present study was to assess whether the direction of flow via the circle of Willis (CoW) changed after stenting for severe internal carotid artery (ICA) stenosis. Methods: 65 patients (38 men, mean age 63.2 ± 8.4 years, range 44–82) with a symptomatic ICA occlusion were investigated. Magnetic resonance angiography was performed prior to and 1 week after carotid artery stenting (CAS). The pattern in the CoW was assessed. Results: One third of the subjects (35.38%) had a significantly altered flow pattern in the CoW after unilateral CAS, including blocked ipsilateral A1 segment collateral (n = 4), blocked contralateral A1 segment collateral (n = 5), blocked ipsilateral posterior communicating artery (PCoA) segment collateral (n = 4), blocked ipsilateral A1 segment and P1 segment collateral (n = 1), opening of ipsilateral A1 segment collateral (n = 5), opening of ipsilateral PCoA segment collateral (n = 3) and opening of ipsilateral P1 segment collateral (n = 1). Conclusions: CoW segmental hypoplasia is not a static feature. Willisian collateralization with recruitment of the CoW segment (A1, P1 and PCoA) may be blocked after CAS. CAS also leads to the opening of new willisian collateralization, either for relief of reperfusion pressure or for other hypoperfused areas.

Ophthalmic Artery Flow and Cognitive Performance in Patients with Carotid Artery Stenosis

“…In our previous study, 23 of 65 (35%) patients with symptomatic CAS had a significantly altered flow pattern in the circle of Willis on the magnetic resonance (MR) angiography after carotid artery stenting [19]. In summary, segments in the circle of Willis were opened preoperatively but blocked after carotid revascularization in 14 patients, whereas other segments of the circle of Willis were closed initially but reopened postoperatively in 9 patients, leading to the reorganization of Willisian collateralization.…”

Circle of Willis anomalies in stroke patients related with symptomatic carotid artery disease

“…Bu oran normal popülasyonda için bildirilmiş olan yaklaşık %50 oranına göre yüksektir. Fakat normal popülasyondaki anomalik WP segment sıklık sırası ile bizim olgularımız arasında belirgin fark yoktu (14,16) WP anomalilerinden hangisinin hemodinamik yetmezlikte önemli olacağı tutulum konfigürasyonuna göre değişir. Örneğin P1 segmentinin aplazisi yada çapının PcomA' den daha küçük olması durumunda oksipital lobun kan ihtiyacı PcomA vasıtasıyla ipsilateral İKA' dan sağlanacağından (17), ipsilateral hemisferin perfüzyonunda bozukluk ortaya çıkacak bu da artmış inme riskine neden olacaktır.…”

Appraising the Plasticity of the Circle of Willis: A Model of Hemodynamic Modulation in Cerebral Arteriovenous Malformations

“…Radiosurgery reduced the collateralization demand, which shut down recruitment and led to a false-positive MRA diagnosis of CoW vascular hypoplasia. CoW segmental hypoplasia is not only a variable feature, but is also enrolled as part of an autoregulatory mechanism [3,4]. …”

“…Nevertheless, the collateral pathway may be reversely closed after pathological hemodynamics have been corrected. One of our previous studies found that extracranial internal carotid artery occlusion might lead to a prompt initiation of CoW collaterals, while they promptly ceased in one third of the subjects after carotid artery stenting [3]. However, the number of blocked recruiting segments in the CoW was statistically higher than that of ‘hypoplastic’ segment openings in the CoW.…”

“…However, the number of blocked recruiting segments in the CoW was statistically higher than that of ‘hypoplastic’ segment openings in the CoW. The hemodynamic redistribution after carotid artery stenting was predominantly observed in the anterior circulation [3,4]. Given this background, we hypothesized that the plasticity of CoW served as a reservoir for cerebral hypoperfusion stress and collateral demand.…”