Are the distributions of variations of circle of Willis different in different populations? – Results of an anatomical study and review of literature

BACKGROUND: Previous studies have proposed correlation between variants of the cerebral arterial circle (also known as circle of Willis) and some cerebrovascular diseases. Differences in the incidence of these diseases in different populations have also been investigated. The study of variations in the anatomy of the cerebral arterial circle may partially explain differences in the incidence of some of the cerebrovascular diseases in different ethnic or racial groups. While many studies have investigated the variations in the anatomy of each segment of the cerebral arterial circle, few have addressed the variants of the cerebral arterial circle as a whole. Similarly, the frequency of occurrence of such variants in different ethnic or racial groups has not been compared. METHODS: 102 brains of recently deceased Iranian males were dissected, in order to observe variations in the anatomy of the cerebral arterial circle. The dissection process was recorded on film and digitized. One resized picture from each dissection, showing complete circle has been made available online. The variations of the circle as whole and segmental variations were compared with previous studies. RESULTS: On the whole, the frequencies of the different variants of the entire cerebral arterial circle and segmental variations were comparable with previous studies. More specifically variants with uni- and bilateral hypoplasia of posterior communicating arteries were the most common in our study, similar to the previous works. No hypoplasia of the precommunicating part of the left anterior cerebral artery (A1), aplasia of A1 or the precommunicating part of the posterior cerebral artery (P1) was seen. In 3% both right and left posterior communcating arteries were absent. CONCLUSION: The anatomical variations found in the cerebral arterial circle of the Iranian males in the current study were not significantly different to those of more diverse populations reported in the literature. While taking into account potential confounding factors, the authors conclude that based on available studies, there is no evidence suggesting that the distributions of the variations of cerebral arterial circle differ in different populations

Chronique des Études anciennes

Cuny Albert, Dürrbach Félix, Radet Georges, Piganiol André, Juret A., Colin Jean. Chronique des Études anciennes. In: Revue des Études Anciennes. Tome 26, 1924, n°3. pp. 291-296

Les enjeux fonciers vus d'en bas. Quand les mobilisations des propriétaires fonciers se font citoyennes

Ce dossier porte sur les propriétaires fonciers, acteurs mal connus de la construction urbaine, et sur leur pouvoir d’intervention dans la construction de la ville. Il s’intéresse à des cas de mise en friction du droit de propriété avec des projets publics Les conflits que la propriété foncière suscite sont analysés du point de vue des populations propriétaires, occupantes ou voisines dans leur relation avec les autres parties-prenantes du processus d’urbanisation, en premier lieu avec la puissance publique, mais aussi avec d’autres acteurs moins connus qui peuvent conduire les changements. Les formes que prennent les relations sont décryptées dans des situations originales. Les conséquences de ces relations sur le processus d’aménagement lèvent le voile sur des influences sous-évaluées et replacent les jeux de pouvoirs dans la dynamique socio-spatiale de la fabrique urbaine. Trois axes structurent et traversent les articles qui composent ce dossier : l’appropriation du droit foncier par les habitants, le processus de mobilisation de ces habitants à des fins collectives et citoyennes, et le rôle joué par des intermédiaires dans les négociations et la résolution des conflits. This issue deals with land properties and analyses the land ownership power on the construction of the City. The conflicts initiated by land ownership are analyzed from the point of view of the inhabitants and their relations with the other stakeholders involved in the urbanization process. Public authorities are concerned but less known actors can also lead the changes. Relationships are decrypted in original situations. The consequences of these relations on the planning process, alliances and power plays are considered in the socio-spatial dynamic of urban fabrics. Three axes structure the subject through the proposed articles: the appropriation of land rights by the inhabitants, the process of mobilizing these inhabitants for collective and civic purposes, and the role played by intermediaries in negotiations and conflict resolution