Background: Formation and rupture of cerebral aneurysms may be related to certain types of configuration of the circle of Willis. Analysis of their interdependence can be of great importance. Methods: A group of 114 patients treated operatively for the cerebral aneurysm rupture and a group of 56 autopsied subjects were involved in the study. Four basic types of the circle of Willis configurations were formed–two symmetric types A and C, and two asymmetric types B and D. Results: A statistically significantly higher presence of asymmetry of the circle of Willis in the group of surgically treated subjects (p=0.006) with a significant presence of asymmetric Type B in this group (p=0.017) were determined. The presence of changes in the A1 segment in the group of subjects with solitary aneurysms on the anterior communicating artery showed a statistically significant presence in the group of autopsied subjects (p=0.0004). Analyzing the presence of symmetry of the circle of Willis between the two groups, that is, the total presence of symmetric types A and C indicated their statistically significant presence in the group of autopsied patients (p=0.043). Conclusion: Changes such as hypoplasia or aplasia of A1 and the resulting asymmetry of the circle of Willis directly affect the possibility of the rupture of cerebral aneurysms. Detection of the corresponding types of the circle of Willis after diagnostic examination can be the basis for the development of a protocol for monitoring such patients.

It is yet unknown how the formation of aneurysm inside the human body occurs. Thus, the understanding and analysis of the Coanda effect will result in a better overview of the overall fluid mechanics that develops inside such a structure, leading not only to better treatment plans, but also to diminished postoperative risks. This paper presents how the fluid behaves in this situation, and takes into consideration how this physical phenomenon influences the hemodynamics inside numerous anatomical regions, located in the central nervous system, where aneurysms usually develop. Analyzing the three main areas in which cerebral aneurysms form the Coanda effect can potentially lead to the rupture of the aneurysm, by changing the blood flow trajectory, it should be taken into consideration when choosing a treatment plan, especially in postoperative care. In addition, there are other factors that can influence the evolution of an aneurysm such as shape, size, localization and the patient’s health condition. Understanding and analysis of the Coanda effect will result in a better overview of the overall fluid mechanics that develops inside such a structure, leading not only to better treatment plans, but also to diminished postoperative risks.

Moyamoya disease is also termed a spontaneous obstruction of the arteries in the circle of Willis. It is recognized as the leading cause of ischemic and hemorrhagic stroke. The infrequent cause of stroke is radiologically characterized by the continuous progression of stenosis of the end portion of the bilateral internal carotid artery and compensatory capillaries collaterals. A 1yr old child was admitted to the pediatric I.C.U with a complaint of decreased sensorium, decreased food intake and decreased right upper and lower extremity movements past two days. He had a history of convulsions at seven months of age. He was diagnosed with Moyamoya disease on Magnetic Resonance cerebral angiography. The clinical findings on MR-Angiography show multiple collaterals noted around Circle of Willis, specifically around the posterior communicating artery, anterior communicating artery, posterior cerebral artery, bilateral lenticulostriate, thalamoperforating arteries and medialfrontobasal arteries, which is suggestive of Moyamoya disease. Magnetic resonance imaging of the brain shows Gyral diffusion restriction in a right fronto-parieto-temporal region with mild swelling. The above clinical findings on MR-angiography show the Moyamoya disease in 1year old male child. These clinical findings on MR-Angiography and M.R.I – brain and neck can help the clinician accurately diagnose and manage this rare case.

Haemodynamic simulations are increasingly used to study vascular diseases like Intracranial Aneurysms (IA) and to further develope treatment options. However, due to limited data, some aspects must rely on heuristics, especially at the simulation’s distal ends. In literature, Murray’s Law is often used to model the outflow split based on vessel cross-section area, but this poses challenges for the communicating arteries in the Circle of Willis (CoW). In this study, we contribute by assessing the impact of Murray’s Law in patient-specific geometries featuring IA at the posterior communication. We simulate different domain extensions, representing common modelling choices. We establish Full CoW simulations as a baseline to evaluate the effect of these modelling assumptions on haemodynamic indicators, focusing on IA growth and rupture-related factors like Wall Shear Stress (WSS) and Oscillatory Shear Index (OSI). Our findings reveal qualitative alterations in haemodynamics when not modeling posterior communication. Comparisons between computing the anterior circulation and computing the whole Circle of Willis reveal quantitative changes in WSS may reach up to 80%, highlighting the significance of modelling choices in assessing IA risks and treatment strategies.