Role of Morphological and Hemodynamic Factors in Predicting Intracranial Aneurysm Rupture: A Review

Abstract

Intracranial aneurysms (IAs) carry the risk of rupture, which will lead to subarachnoid hemorrhage, which has a high mortality and morbidity risk. However, the treatment of IA's carries mortality and morbidity risks too. There are well-known risk factors for the rupture of IAs like age, size, and site. However, choosing patients with unruptured IAs for treatment is still a big challenge. This review article aimed to find out the relationship between morphological and hemodynamic characters of IAs with their rupture and incorporate these factors with well-known factors to yield an accurate module for predicting the rupture of IAs and decision-making in the treatment of unruptured IAs. We searched in PubMed and Medline databases by using the following keywords: IAs, subarachnoid hemorrhage, and risk of rupture, morphology, and hemodynamic "mesh." A total of 19 studies with 7269 patients and 9167 IAs, of which 1701 had ruptured, were reviewed thoroughly. Some modules like population, hypertension, age, size, earlier subarachnoid hemorrhage, and site (PHASES) score that involve well-known risk factors can be used to assess the risk of rupture of IAs. However, decision making for treating unruptured IA needs more detailed and more accurate modules. Studying morphological and hemodynamic factors and incorporation of them with well-known risk factors to yield a more comprehensive module will be very helpful in treating unruptured IA. Among morphological factors, aspect ratio (AR), size ratio (SR), aneurysm height, and bottleneck factor showed significant effects on the growth and rupture of IA. Besides, wall shear stress (WSS), oscillatory shear index (OSI), and low wall shear stress area (LSA) as hemodynamic factors could have a substantial impact on the formation, shape, growth, and rupture of unruptured IA.

Inflow Angle Impacts Morphology, Hemodynamics, and Inflammation of Side‐wall Intracranial Aneurysms

“…While previous studies using CFD simulation reported that inflow angle may positively correlate with WSS and the inflow velocity 2,8 . Actually, results from CFD were under the condition of an idealized model with other parameters controlled including aneurysm size, location, aspect ratio, and hypertension, which all could contribute to aneurysm hemodynamics change 9,10 . Interestingly, in this study, it was also found that aneurysm size showed a negative trend toward inflow velocity and WSS, which was supported by another CFD study 25 .…”

“…It has been reported that, in side‐wall aneurysms, blood flow hemodynamic environment of the aneurysm can change with the increased inflow angle 2,8 . Moreover, hemodynamics, influenced and mediated by morphological parameters, have been proposed to be a driven factor of inflammation processes in the aneurysmal wall, which has been suggested as the key mediator of aneurysm initiation and progression 9–13 . Thus, in side‐wall aneurysms, inflow angle may impact hemodynamics and further affect inflammation processes in the aneurysmal wall, since inflammation processes like inflammatory cell infiltration could be initiated by abnormal hemodynamics 13,14 …”

“Atypical” Mild Clinical Presentation in Elderly Patients With Ruptured Intracranial Aneurysm: Causes and Clinical Characteristics

“…However, on the basis of significant brain atrophy and vascular degeneration in our elderly cohort, we consider that a larger bleeding volume and more diffuse distribution of SAH could be noted after the rupture of an aneurysm with larger size. Aneurysms with a wide neck, however, are characterized by slower blood flow, less turbulence formation and lower shear stress, which has been widely reported as a factor related to a lower risk of rupture, compare to those with a narrow neck (31). With more stable pressure and hemodynamics across the lesion, rupture of a wide-necked aneurysm might be less likely to cause widespread bleeding in the subarachnoid space (32).…”

Patient-specific modeling of hemodynamic characteristics associated with the formation of visceral artery aneurysms at uncommon locations

“…On the other hand, significantly lower OSI was only observed for the high-WSS group. The role of OSI in aneurysm forming and rupture remains controversial ( 27 ).…”