UNASSIGNED: Circulus arteriosus cerebri (CAC), responsible for supplying blood to the brain, presents anatomical variations that have been associated with both haemorrhagic and ischemic strokes. Therefore, it is crucial to conduct comprehensive investigations and comparisons of the diverse variant components of the CAC, published in various journals, and analyze them to identify individuals at risk of cerebrovascular pathologies, thereby ensuring enhanced and timely treatment.
UNASSIGNED: A scoping review according to the five-stage protocol by Arksey and O\'Malley was performed between February and June 2023. Seven hundred and seventy-seven records were initially identified, and a total of 51 studies were finally included.
UNASSIGNED: This scoping review focuses on the anatomical variations of the CAC and their clinical implications on cerebrovascular disease and includes more original articles than review s. Consistent with previous findings, most of the records included small populations or samples, while only three records reported larger populations. Surprisingly, the populations enclosed in the included records consisted of autopsied cadaveric specimens more than living subjects. Finally, the qualitative analysis highlighted three main themes concerning the relationship between the normal CAC morphology and the cerebrovascular disease onset as well as the variant CAC morphology and its main features that might be also involved in these diseases. Finally, techniques that can be used to measure CAC have also been assessed.
UNASSIGNED: Variations in the CAC, more common in the posterior part, with genetic and environmental factors influencing these variations impact cerebrovascular disorders. Understanding variants components of CAC can aid in improving brain surgeries and post-stroke care.

The Circle of Willis (CoW) describes the arterial system in the human brain enabling the neurovascular blood supply. Neurovascular diseases like intracranial aneurysms (IAs) can occur within the CoW and carry the risk of rupture, which can lead to subarachnoid hemorrhage. The assessment of hemodynamic information in these pathologies is crucial for their understanding regarding detection, diagnosis and treatment. Multi-dimensional in silico approaches exist to evaluate these hemodynamics based on patient-specific input data. The approaches comprise low-scale (zero-dimensional, one-dimensional) and high-scale (three-dimensional) models as well as multi-scale coupled models. The input data can be derived from medical imaging, numerical models, literature-based assumptions or from measurements within healthy subjects. Thus, the most realistic description of neurovascular hemodynamics is still controversial. Within this systematic review, first, the models of the three scales (0D, 1D, 3D) and second, the multi-scale models, which are coupled versions of the three scales, were discussed. Current best practices in describing neurovascular hemodynamics most realistically and their clinical applicablility were elucidated. The performance of 3D simulation entails high computational expenses, which could be reduced by analyzing solely the region of interest in detail. Medical imaging to establish patient-specific boundary conditions is usually rare, and thus, lower dimensional models provide a realistic mimicking of the surrounding hemodynamics. Multi-scale coupling, however, is computationally expensive as well, especially when taking all dimensions into account. In conclusion, the 0D-1D-3D multi-scale approach provides the most realistic outcome; nevertheless, it is least applicable. A 1D-3D multi-scale model can be considered regarding a beneficial trade-off between realistic results and applicable performance.

Background and Objectives: The published literature highlights the fact that the integrity of the Circle of Willis has a direct impact on stroke outcome, especially in cases of distal internal carotid T occlusion. The aim of this study was to review the available data on the Circle of Willis configuration and thrombus location impact on patient outcome in cases of ischemic stroke. Materials and Methods: A systematic search according to PRISMA guidelines was performed in PubMed, Cochrane, and EMBASE databases to identify studies investigating the influence of Circle of Willis variants on ischemic stroke outcomes published up to March 2023. The manuscripts were reviewed by three researchers separately and scored on the quality of the research using the MINORS criteria. Results: After screening 157 manuscripts, 11 studies (n = 4643) were included. Circle of Willis integrity plays a vital role in stroke outcome, especially when T-form occlusions are present. Despite this, in the event of M1 occlusion Circle of Willis configuration does not play an important role. In cases of distal internal carotid artery occlusion, the presence of a fully developed contralateral A1 segment and anterior communicating artery is essential for a favorable stroke outcome. Conclusions: The preserved integrity of the Circle of Willis has great significance for collateral flow in the event of ischemic stroke and helps patients to achieve more favorable outcomes, as it determines the affected brain territory. The clinical outcome of the ischemic stroke appears to be significantly better if only one artery territory is affected, compared to two or more.

OBJECTIVE: Intracranial aneurysms are more common in women than in men. Some anatomical variants of the circle of Willis (CoW) are associated with a higher risk of developing intracranial aneurysms. We hypothesized that variations of the CoW are sex dependent which may partly explain why intracranial aneurysms are more common in women. We systematically reviewed and meta-analyzed the literature to compare the presence of anatomical variations of the CoW between women and men in the general population.
METHODS: A systematic search in Pubmed and EMBASE using predefined criteria, following the PRISMA guidelines was performed. The presence of different CoW anatomical variants and a complete CoW was compared between women and men using an inverse variance weighted random effects meta-analysis to calculate relative risks (RR) with 95% confidence intervals (95% CIs).
RESULTS: Fourteen studies were included reporting on 5478 healthy participants (2511 women, 2967 men). Bilateral fetal type posterior cerebral arteries (RR 2.79; 95%CI 1.65-4.72, I2=0%), and a complete CoW (RR 1.24, 95%CI 1.13-1.36; I2=0%) were more prevalent in women than in men. The variants absence or hypoplasia of one of the anterior cerebral arteries (RR 0.58, 95%CI 0.38-0.88, I2=57%) and hypoplasia or absence of both posterior communicating arteries (RR 0.79, 95%CI 0.71-0.87, I2=0%) were more prevalent in men.
CONCLUSIONS: Several anatomical variations of the CoW are sex dependent, with some variants being more common in women while others in men. Future research should assess how these sex-specific CoW variants relate to the sex-specific occurrence of intracranial aneurysms.

Flow diverters (FDs) have demonstrated a safe and effective profile. However, the use of FDs for posterior communicating artery (PComA) aneurysms remains controversial.
To evaluate the safety and effectiveness of FDs for PComA aneurysms using a systematic review and meta-analysis of the literature.
We performed a systematic search from inception until June 2022 for flow diversion in PComA aneurysms. Primary effectiveness was the rate of complete aneurysm occlusion defined by Raymond-Roy class 1. Primary safety outcomes were treatment-related ischemic/hemorrhagic (composite) events causing morbidity and mortality. Secondary safety was PComA patency at follow-up. Random-effects meta-analyses were used to calculate proportions, and statistical heterogeneity was assessed.
A total of 13 studies with 397 patients harboring 403 aneurysms were included. Mean age was 48 years, and the mean aneurysm size was 5.3 mm. Most aneurysms were unruptured (65%). Complete occlusion at final follow-up was 73% (CI 66%-79%), and adjunctive coils were used in 10% of aneurysms. Retreatment rate was 2% (CI 0%-9%). The primary safety composite outcome was 4% (CI 3%-7%), and mortality was 1%. PComA patency at final follow-up was 76% (CI 57%-89%). Subgroup analysis, patients with fetal PComAs had a lower complete occlusion rate (42% fetal PComA vs 77%, psubgroupdifference = <.01).
The performance of FDs in PComA aneurysms is comparable with outcomes found in other subtypes of supraclinoid aneurysms. Effectiveness was acceptable and safety favorable. However, effectiveness was suboptimal in patients with fetal-type PComAs; alternative treatments should be considered in these cases.

UNASSIGNED: The anterior (AcomA) and posterior communicating arteries (PcomA) are two of the most frequent sites for intracranial aneurysms. Anatomical variations in the Circle of Willis (COW) are frequently observed in patients with AcomA and PcomA aneurysms. Strong evidence is needed to determine the pooled estimate of the effect of COW variations on the formation and rupture of these aneurysms.
UNASSIGNED: This systematic review and meta-analysis aimed to establish the effect of COW variations on the formation and rupture of AcomA and PcomA aneurysms using available studies.
UNASSIGNED: PubMed, Embase, and Web of Science databases were systematically searched for studies published in English before September 21, 2022. Studies investigating AcomA aneurysms and the hypoplastic/aplastic A1 segment of the anterior cerebral artery and PcomA aneurysms and hypoplastic/aplastic PcomA or fetal-type posterior cerebral artery (FTP) were included. The heterogeneity of the studies was assessed using Cochran Q-test and I2 statistic. Pooled estimate was assessed using either a random- or fixed-effects model based on the heterogeneity of the studies. Among the 4,932 studies, 21 were eligible and included in the analysis. The presence of hypoplastic/aplastic A1 was significantly correlated with the formation [OR (95% confidence interval [CI]) = 7.97 (5.58, 11.39), P < 0.001] and rupture [OR (95%CI) = 1.87 (1.29, 2.72), P < 0.001] of AcomA aneurysms. Significant associations between FTP and both the formation [OR (95%CI) = 2.15 (1.41, 3.30), P < 0.001] and rupture [OR (95%CI) = 1.72 (1.26, 2.36), P < 0.001] of PcomA aneurysms were observed.
UNASSIGNED: Significant associations were observed between COW variations and both the formation and rupture of AcomA and PcomA aneurysms. This can help in determining interventions for patients with aneurysms.
UNASSIGNED: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=225149, identifier: CRD42021225149.

暂无摘要。

OBJECTIVE: Radiation-induced cerebrovascular toxicity is a well-documented sequelae that can be both life-altering and potentially fatal. We performed a meta-analysis of the relevant literature to create practical models for predicting the risk of cerebral vasculopathy after cranial irradiation.
METHODS: A literature search was performed for studies reporting pediatric radiation therapy (RT) associated cerebral vasculopathy. When available, we used individual patient RT doses delivered to the Circle of Willis (CW) or optic chiasm (as a surrogate), as reported or digitized from original publications, to formulate a dose-response. A logistic fit and a Normal Tissue Complication Probability (NTCP) model was developed to predict future risk of cerebrovascular toxicity and stroke, respectively. This NTCP risk was assessed as a function of prescribed dose.
RESULTS: The search identified 766 abstracts, 5 of which were used for modeling. We identified 101 of 3989 pediatric patients who experienced at least one cerebrovascular toxicity: transient ischemic attack, stroke, moyamoya, or arteriopathy. For a range of shorter follow-ups, as specified in the original publications (approximate attained ages of 17 years), our logistic fit model predicted the incidence of any cerebrovascular toxicity as a function of dose to the CW, or surrogate structure: 0.2% at 30 Gy, 1.3% at 45 Gy, and 4.4% at 54 Gy. At an attained age of 35 years, our NTCP model predicted a stroke incidence of 0.9% to 1.3%, 1.8% to 2.7%, and 2.8% to 4.1%, respectively at prescribed doses of 30 Gy, 45 Gy, and 54 Gy (compared with a baseline risk of 0.2%-0.3%). At an attained age of 45 years, the predicted incidence of stroke was 2.1% to 4.2%, 4.5% to 8.6%, and 6.7% to 13.0%, respectively at prescribed doses of 30 Gy, 45 Gy, and 54 Gy (compared with a baseline risk of 0.5%-1.0%).
CONCLUSIONS: Risk of cerebrovascular toxicity continues to increase with longer follow-up. NTCP stroke predictions are very sensitive to model variables (baseline stroke risk and proportional stroke hazard), both of which found in the literature may be systematically erring on minimization of true risk. We hope this information will assist practitioners in counseling, screening, surveilling, and facilitating risk reduction of RT-related cerebrovascular late effects in this highly sensitive population.

UNASSIGNED: Microvascular failure might result in the collapse of cerebral collaterals. However, controversy remains regarding the role of leukoaraiosis (LA) in collateral recruitment. We, therefore, performed a systematic review and meta-analysis of the association between LA and cerebral collaterals.
UNASSIGNED: Ovid Medline, PubMed, Embase, Web of Science, and three Chinese databases were searched from inception to August 2021. Two types of cerebral collaterals, including Circle of Willis (CoW) and leptomeningeal collaterals (LC), were investigated separately. Random effect models were used to calculate the pooled odds ratio (OR). Meta-regression and subgroup analyses were performed to explore the potential sources of heterogeneity.
UNASSIGNED: From 14 studies (n = 2,451) that fulfilled our inclusion criteria, data from 13 could be pooled for analysis. Overall, there was a significant association between severe LA and incomplete CoW (pooled OR 1.66, 95% CI 1.18-2.32, p = 0.003), with low heterogeneity (I 2 = 5.9%). This association remained significant in deep LA (pooled OR 1.48, 95% CI 1.04-2.11, p = 0.029, I 2 = 0), but not periventricular LA. Similarly, there was a significant association between LA and LC (pooled OR 1.73, 95% CI 1.03-2.90, p = 0.037), but with high heterogeneity (I 2 = 67.2%). Meta-regression indicated a negative association of sample size with the effect sizes (p = 0.029). In addition, most of the studies (7/9) included into the analysis of the relationship of severe LA with poor LC enrolled subjects with large vessel occlusion stroke, and this relationship remained significant when pooling the seven studies, but with high heterogeneity.
UNASSIGNED: Severe LA is associated with a higher prevalence of poor collaterals. This association is robust for CoW but weak for LC. Further studies are required to explore the underlying mechanisms.

Background: The role of regional hemodynamics in the intracranial aneurysmal formation, growth, and rupture has been widely discussed based on numerical models over the past decades. Variation of the circle of Willis (CoW), which results in hemodynamic changes, is associated with the aneurysmal formation and rupture. However, such correlation has not been further clarified yet. The aim of this systematic review is to investigate whether simulated hemodynamic indices of the CoW are relevant to the formation, growth, or rupture of intracranial aneurysm. Methods: We conducted a review of MEDLINE, Web of Science, and EMBASE for studies on the correlation between hemodynamics indices of the CoW derived from numerical models and intracranial aneurysm up to December 2020 in compliance with PRISMA guidelines. Results: Three case reports out of 1046 publications met our inclusion and exclusion criteria, reporting 13 aneurysms in six patients. Eleven aneurysms were unruptured, and the state of the other two aneurysms was unknown. Wall shear stress, oscillatory shear index, von-Mises tension, flow velocity, and flow rate were reported as hemodynamic indices. Due to limited cases and significant heterogeneity between study settings, meta-analysis could not be performed. Conclusion: Numerical models can provide comprehensive information on the cerebral blood flow as well as local flow characteristics in the intracranial aneurysm. Based on only three case reports, no firm conclusion can be drawn regarding the correlation between hemodynamic parameters in the CoW derived from numerical models and aneurysmal formation or rupture. Due to the inherent nature of numerical models, more sensitive analysis and rigorous validations are required to determine its measurement error and thus extend their application into clinical practice for personalized management. Prospero registration number: CRD42021125169.