Aspect ratio as a factor predicting rupture of cerebral aneurysms

Cerebral vascular aneurysms are abnormalities present in 2–5% of the population. Aneurysm rupture often leads to the development of a hemorrhagic stroke. Among its consequences are disability and death. Despite this, preventive surgical treatment of aneurysms is not always justified, since it leads to serious postoperative complications. In this regard, there is the problem of developing and justifying reliable and convenient criteria for assessing the risk of aneurysm rupture. Aspect ratio (the ratio of the height of the aneurysm to the diameter of the neck) is the relative size of the aneurysms used to classify them as prone to rupture and not prone to rupture. This characteristic is also used as predictor of aneurysm rupture. In this paper, we carried out a series of numerical biomechanical calculations aimed at substantiating the critical value of the aspect ratio characterizing aneurysms prone to rupture. In the simulation, the average shear stresses on the aneurysm wall were compared for different aspect ratios from 0.5 to 2.25 with a step of 0.25 for asymmetric models and for aspect ratios from 0.5 to 2.1 with a step of 0.2 for symmetrical models. It was revealed that average wall shear stresses on the aneurysm significantly decrease when the aspect ratio is greater than critical. An abrupt decrease in the average wall shear stresses on the aneurysm with aspect ratio greater than the critical value was revealed.