Morphological and numerical assessment of intracranial aneurysms ruptures risk

Background ― Rupture of intracranial aneurysms leads to subarachnoid hemorrhage and, as a consequence, to hemorrhagic stroke. Mortality at the same time reaches 45%. Moreover, half of survivors experience serious neurological problems. Diagnosis of cerebral aneurysms is difficult due to the fact that they usually do not have any typical symptoms. Development of criteria for assessing risk of aneurysm rupture is an actual scientific problem, since preventive surgical treatment entails serious post-operative complications and untimely treatment leads to aneurysm rupture. It is necessary to understand whether this or that aneurysm is prone to rupture in order to form a treatment tactic. Methods ― Factors such as size of aneurysm, size ratio, irregular shape and wall shear stress were highlighted in this work. Each of these factors was considered for four models of aneurysms and numerical simulations of the blood flow in these aneurysms were performed. Size ratio was calculated for each model: 1.2, 1.6, 2.0 and 2.5. Height of aneurysms was 3.5, 4.5, 6.0 and 7.5 mm. Aneurysms with size ratios of 2.0 and 2.5 had an irregular shape. Given the morphological factors, 1.2-aneurysm and 1.6-aneurysm had small risk of rupture and other aneurysms had high rupture risk. Results ― Numerical biomechanical modeling showed that there were no vortices in small aneurysm during the entire cardiac cycle. Average wall shear stress of aneurysms with 2.0 and 2.5 size ratios was more than two times lower than wall shear stress of the small aneurysm. Wall shear stress values on most of the dome of the largest aneurysm did not exceed 1.5 Pa. The increase in size ratio led to an increase of blood pressure in aneurysm during the entire cardiac cycle. Distribution of wall shear stress in aneurysms with size ratios more than 2.0 turned out to be essentially inhomogeneous. Also these aneurysms had complex flow patterns. Presence of vortices, inhomogeneous distribution of wall shear stress indicates a higher risk rupture of such aneurysms. Conclusion ― It can be concluded that both morphological and hemodynamic factors do not contradict each other, but complement each other. This fact suggests that one can develop objective and convenient for use in preoperative planning of surgical treatment methods for assessing the risk of cerebral aneurysms rupture for a particular patient