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CT angiography of the models of the stages of aneurysm formation and growth. (A) Post-anterior communicating artery (ACoA) aneurysm formation. (B) Pre-ACoA aneurysm formation: the ACoA aneurysm was removed. (C) Pre-internal carotid artery (ICA) aneurysm growth model-2: the ICA aneurysm was decreased in size. (D) Pre-ICA aneurysm growth model-1: the ICA aneurysm was further decreased in size.
Source publication
Hemodynamic parameters play an important role in aneurysm formation and growth. However, it is difficult to directly observe a rapidly growing de novo aneurysm in a patient. To investigate possible associations between hemodynamic parameters and the formation and growth of intracranial aneurysms, the present study constructed a computational model...
Contexts in source publication
Context 1
... MIMICS 10.0 software (Belgium Materialise Company, Leuven, Belgium), we defined the region of interest and extracted the luminal surface from the three-dimensional raster gray-scale image to construct the post-aneurysm and an anterior communicating artery aneurysm formation model. We then constructed a pre-aneurysm and an anterior communicating artery aneurysm formation model by removing the aneurysm and an anterior communicating artery aneurysm, and further adjusted this model to construct a pre-internal carotid artery aneurysm growth model-2 (by decreasing the size of the internal carotid artery aneurysm) and a pre-internal carotid artery aneurysm growth model-1 (by further decreasing the size of the internal carotid artery aneurysm; Figure 1). ...
Context 2
... areas that needed to be decreased in size were selected, the smooth function was used, and parameters were set to control the changes. The shape and size of the aneurysms could then be constructed as required (Figure 1). The pre-aneurysm and an anterior communicating artery aneurysm formation model was considered to represent the stage immediately preceding the initiation of aneurysm and an anterior communicating artery aneurysm formation. ...
Citations
... This stress could act on the shape and structure of endothelial cells and cause a loss of mechanical resistance of the vessel wall [8]. This effect may lead to the growth of aneurysms and could also impact hemodynamic parameters in both the local and neighboring arteries [10]. ...
... This effect could lead to permanent remodeling in the arterial wall in the adjacent area of the treated aneurysm neck. As a result, a recurrent aneurysm could develop near the treated aneurysm [10,11]. Similarly, clipping can induce hemodynamic changes in the adjacent vessels creating areas of adjacent WSS within the parent vessel [10]. ...
... As a result, a recurrent aneurysm could develop near the treated aneurysm [10,11]. Similarly, clipping can induce hemodynamic changes in the adjacent vessels creating areas of adjacent WSS within the parent vessel [10]. ...
Even after clipping of intracranial aneurysms, patients may experience incomplete occlusion or the future recurrence of their treated aneurysm. This paper presents a distinctive case of a recurrent A1-A2 anterior cerebral artery aneurysm that underwent four interventions over 16 years. The aneurysm was treated with two clippings, subsequent coiling, and flow diversion for definitive treatment. The challenges encountered in managing bifurcation aneurysms are discussed, emphasizing the importance of considering hemodynamic factors, vessel geometry, and recurrence risk factors in treatment decisions. The case highlights the need for closer follow-up of ruptured bifurcation aneurysms due to the higher likelihood of recurrence. The role of flow diverters in reinforcing vessel anatomy and preventing recurrence is also highlighted.
... IAs refer to local abnormal enlargement of the cerebral arterial cavity. This is usually caused by congenital local defects of the arterial wall and increased intracavitary pressure (Wang et al. 2013). The prevalence of IAs is 7% in the 35-75-year age group of the Chinese population . ...
Brain arteriovenous malformations (BAVMs) and intracranial aneurysms (IAs) are the results of a combination of genetic and environmental factors. Epigenetic factors also play an important role in the pathogenesis of these disorders. The aim of this study was to determine the effect of DNA methylation at the cyclin-dependent kinase inhibitor 2A (CDKN2A) gene on the risk of BAVMs and IAs. A total of 70 intracranial vascular malformation patients (22 patients with BAVMs and 48 patients with IAs) and 26 patients with cerebral trauma (used as controls) were included in this study. DNA methylation levels of eight cytosine-phosphate-guanine (CpG) dinucleotides present in the CDKN2A gene were measured using bisulfite pyrosequencing technology. Significant differences in methylation at CpG1 (p = 0.005), CpG5 (p = 0.011), and CpG8 (p = 0.017) were observed between BAVM patients and controls. CDKN2A methylation levels in BAVM patients were much higher than those in IA patients (CpG5: p = 0.004; CpG8: p = 0.010). Significant differences were observed between female IA patients and female BAVM patients (CpG5: p = 0.006; CpG8: p = 0.005; mean: p = 0.015). Receiver operating characteristic (ROC) curve analysis showed that the CDKN2A gene methylation trended toward a diagnostic indicator in BAVM patients (area under curve = 0.711, p = 0.013). In conclusion, our study demonstrated that the CDKN2A gene methylation levels are significantly correlated with the occurrence of BAVMs, and thus, have potential for use in the early diagnosis of BAVMs. Future research on the pathogenesis of BAVMs should focus on the role of genetic factors in aberrant venous development. The association of the CDKN2A gene with venous development also deserves further study.
... As ACoA is a communicating artery, which is supplied by both ICAs, it is characterized by different hemodynamics than MCA. Wang et al [45] study showed that WSS and flow rate in ACoA aneurysm are lower than in MCA aneurysm. Therefore, changes in hemodynamics parameters, resulting from increase or decrease tortuosity, might influence differently these two artery aneurysm formations. ...
Objectives
We decided to perform computer-aided analysis of the anterior cerebral artery (ACA) to check for a potential correlation with anterior communicating artery (ACoA) aneurysm presence and growth.
Methods
We retrospectively analyzed the ACA anatomy of 121 patients with ACoA aneurysms along with 121 age, risk factors, and vessel side-matched control patients without an ACoA aneurysm. We obtained their medical history and digital subtraction angiography (DSA) data from their medical records. For each patient’s DSA, we extracted curve representing the course of their ACA and calculated its relative length (RL), sum of angle metrics (SOAM), triangular index (TI), product of angle distance (PAD), and inflection count metrics (ICM).
Results
Patients with ACoA aneurysm had significantly higher RL (0.64 ± 0.23 vs. 0.56 ± 0.22; p < 0.01), SOAM (0.27 ± 0.19 vs. 0.18 ± 0.15; p < 0.01), PAD (0.12 ± 0.13 vs. 0.09 ± 0.11; p = 0.02), and TI (0.57 ± 0.14 vs. 0.44 ± 0.15; p < 0.01). In multivariate logistic regression analysis, after adjustment for possible confounders, SOAM (OR, 1.34; 95% CI, 1.12–1.63; p < 0.01) and TI (OR, 1.84; 95% CI, 1.47–2.35; p < 0.01) remained independently associated with higher risk of ACoA aneurysm. Additionally, we found significant negative correlations between TI and aneurysm dome size (R = − 0.194; p = 0.047).
Conclusions
Increased tortuosity of ACA might increase the risk of ACoA aneurysm development and decrease the risk of aneurysm growth.
Key Points
• Anterior cerebral artery’s sum of angle metrics is associated with hypertension as well as with history of ischemic stroke and myocardial infarction.
• Increased tortuosity of anterior cerebral artery might be associated with anterior communicating artery aneurysm development.
• Tortuosity of anterior cerebral artery is negatively correlated with anterior communicating artery aneurysm dome size.
... By nature, they are subject to the same systemic conditions and risk factors (i.e., age, sex, smoking status, alcohol consumption, and genetic variables) already known to influence their development and growth (4). Moreover, the Table 3 symmetric origin of such lesions demonstrates similarities in hemodynamic stress and wall shear stress as etiologic forces (23)(24)(25). For this reason, we speculated that mirror aneurysms might be of similar size, and indeed, lesions of 126 patients (74.6%) in our series showed little size disparity. ...
Objective
Mirror aneurysms are generally considered as a subset of multiple aneurysms, defined as aneurysms occurring bilaterally and symmetrically on the same-named vessels. Although not infrequent, the characteristics of mirror aneurysms are not well studied. This investigation was conducted to elucidate the anatomic features of such lesions and examine treatment options.
Materials and Methods
A retrospective review was conducted, aimed at 172 patients treated for 344 mirror aneurysms between January 2007 and December 2015. Aneurysms of similar nature but in asymmetric locations on the same-named vessels were excluded. All available records were examined and lesion characteristics, as well as treatment outcomes were assessed.
Results
In study subjects (n = 172), mirror aneurysms most often involved middle cerebral artery bifurcation (n = 83), followed by a paraclinoid internal carotid artery (n = 50) and posterior communicating artery (n = 21). Most of the lesions (95.3%) measured ≤ 10 mm, and in 126 patients (74.6%), the size ratios were > 50%. Of the 344 aneurysms studied, coil embolization was undertaken in 217, surgical clipping in 62, and observation alone (no treatment) in 65. Coil embolization and surgical clipping were done bilaterally in 83 and 12 patients, respectively. In 12 patients, combined coiling and clipping were implemented on each side. Single-stage coil embolization of both the aneurysms was performed in 73 patients, with excellent post-procedural (85.6%) and follow-up (86.8%) occlusive results. There was no procedure-related morbidity or mortality.
Conclusion
By adopting different treatment strategies to different configurations and vascular sources, mirror aneurysms can be safely and effectively treated. If feasible, single-stage coil embolization should be considered as a reasonable treatment option for mirror aneurysms.
... These results suggest that correlating aneurysm location to a maximum, and not simply a region of predefined high WSS, has the potential advantage of providing increased accuracy in prospective predictive models by limiting the search area for future aneurysm formation. After the aneurysm initiation phase )which has been determined to be driven by high WSS and high, positive WSS gradient, 8,9 aneurysm sac enlargement lead to low WSS, 24 which is explained by the presence of a countercurrent vortex within the aneurysm region. In the 47 models studied here, the major flow structures were not affected by the presence or absence of the aneurysm; however, small changes within the parent artery could alter the relative position of the aneurysm and thus change its hemodynamic relationships. ...
Objective
To measure morphological indices and wall shear stress (WSS) of aneurysms and parent artery surface in order to explore the relationship of morphological characteristics and WSS.
Methods
Data from 47 events of consecutive cerebral saccular aneurysms from 39 patients which were referred to the interventional Neuroradiology service of the Shaoxing People’s Hospital, Shaoxing, China between 2014 April and 2015 August. Wall shear stress and wall pressure (WP) of the pre-aneurysm, aneurysm and near vessel (<1.0 cm) surface were obtained. Correlation analysis was carried between morphological parameters and WSS and its ratio. WSS, WP, intra-aneurysmal flow pattern, and location of aneurysms were analyzed.
Results
Impaction zone from inflow jet was located in the distal neck part of aneurysm with high WSS in 36 aneurysms (76.6%). There were significant differences in WSS between pre-aneurysm surface and near vessel (p<0.001), aneurysm (p<0.001), aneurysm and near vessel (p<0.001). Significant correlations were found between aneurysm WSS and aspect ratio (r=-0.296), aneurysm-artery WSS ratio and size ratio (r=-0.322), aspect ratio (r=-0.416).
Conclusion
Uneven WSS distributes in the various part of the pre-aneurysm vessel. The impaction zone from inflow jet is located in the distal neck of aneurysm. Aspect and size ratios can effect aneurysm WSS
... [41][42][43][44] On the other hand, high WSS has been proposed to induce degradation of the internal elastic lamina resulting in aneurysm formation. [45] Another parameter is the oscillatory shear index (OSI) , which measures the directional change of WSS during a cardiac cycle in another study, WSS and OSI were the only independent hemodynamic parameters that were significantly different in ruptured and unruptured aneurysms. [46] We should note that these analysis about ruptured aneurysm is made based on the images of ruptured aneurysms, not those of pre-rupture aneurysms. ...
... Abnormally high wall shear stresses at local regions may also physically damage the internal elastic lamina of blood vessels by over-stretching collagen and elastin fibers, forcing them to experience elevated internal stresses and abnormally high mechanical loading throughout each cardiac cycle (3), and potentially resulting in the formation of blebs which have been associated with an increased risk of rupture (14). High wall shear stress may also stimulate overproduction of matrix metalloproteinases, leading to further destructive remodeling of the internal elastic lamina (15)(16)(17). Ultimately, high local wall shear stresses may weaken the structure of the blood vessel wall and be conducive to the initiation of aneurysm growth and an increased risk of aneurysmal rupture. ...
... It is also known that uniform wall shear stress, within normal physiological limits, stabilizes and limits cell proliferation and apoptosis, whereas low wall shear stress may lead to neointimal hyperplasia (18) and blood vessel regression via endothelial cell apoptosis (17,19). Low shear stresses also result in reduced production of NO, resulting in endothelial cell dysfunction (3). ...
Subarachnoid hemorrhage is a potentially devastating pathological condition in which bleeding occurs into the space surrounding the brain. One of the prominent sources of subarachnoid hemorrhage are intracranial aneurysms (IA): degenerative, irregular expansions of area(s) of the cerebral vasculature. In the event of IA rupture, the resultant subarachnoid hemorrhage ends in patient mortality occurring in ~50% of cases, with survivors enduring significant neurological damage with physical or cognitive impairment. The seriousness of IA rupture drives a degree of clinical interest in understanding these conditions that promote both the development and possible rupture of the vascular malformations. Current metrics for the assessment of this pathology rely on measuring the geometric characteristics of a patient's vessel and/or IA, as well as the hemodynamic stressors existing along the vessel wall. Comparatively less focus has been granted toward understanding the characteristics of much of the bulk-flow within the vasculature and how it may play a role in IAs. Specifically, swirling hemodynamic flow (vortices) have been suggested as a condition which exacerbates vascular changes leading to IAs, yet quantified measurements of the spatial and temporal characteristics of vortices remain overlooked. This dissertation studies the role of the spatial and temporal characteristics of vortex flow and how it plays a role on IA pathology. Its chapters are a collection of five (5) works into this matter. First, established methods for the identification of vortices was investigated, and a novel method for vortex identification and quantification of their characteristics was developed to overcome the limitations of previous methods. Second, the developed method for vortex identification/quantification was then applied to a simulation study to improve predictive models aimed at predicting areas of IA development from those unlikely to suffer this pathology. Third, assessing how the simulated repair of one IA impacts changes to hemodynamic conditions within other nearby un-repaired IAs in a multiple IA system. Fourth, it was determined if vortex identification/quantification improved predictive models aimed at differentiation ruptured from unruptured IAs. Fifth, impart vortical flow of differing characteristics onto cultured vascular cells to determine if vortex stability imparts varied levels of cellular changes.
Background
Flow diverters (FDs) are increasingly used in the treatment of intracranial aneurysms, and carry the risk of thromboembolic complications, even in patients treated with dual antiplatelet therapy. The effect of FDs on the downstream vascular is unknown. The aim of the study was to investigate vascular wall pulse wave velocity (PWV) and contractility changes following FD treatment in a rabbit model.
Methods
FDs (Pipeline Embolic Device, Medtronic Inc., Irvine, California, USA) were implanted in the aorta of normal rabbits and sham-operated aorta were used as controls (n=6 per group). Pulse wave imaging with ultra-fast ultrasound at 1600 frames per second (Vantage, Verasonics, Inc., Kirkland, WA) was performed in the vessel wall distal to FD prior to device implantation and at 8- week follow-up to measure the PWV. Force contraction vascular reactivity studies were conducted in the aortic rings using an organ bath.
Results
The difference in mean PWV in the follow-up compared with pre-implantation was significantly higher in the distal vessels compared with sham controls (1.18 m/s [SD=0.54] vs. 0.37 m/s [SD=1.09], P=0.03). Conversely, the aortic segments distal to the FD exhibited a 55% increase in vascular contractility compared with proximal segments (P=0.002). We observed a significant positive correlation between mean PWV and mean vascular contractility.
Conclusion
Implantation of FD was associated with increased PWV and vascular contractility, suggesting that FD implantation causes changes to the vascular wall. Further studies are needed to understand the clinical implication of changes in vascular PWV and contractility.
Introduction:
Unruptured brain aneurysms (UIAs) present a challenge due to the lack of definitive understanding of their natural history and treatment outcomes. As the treatment of UIAs is aimed at preventing the possibility of rupture, the immediate risk of treatment must be weighed against the risk of rupture in the future. As such, treatment for a large proportion of UIAs is currently individualized.
Areas covered:
In this article, we discuss the important natural history studies of UIAs and discuss the existing scientific evidence and recent advances that help identify the rupture risk guide management of UIAs. We also address the recent advances in pharmacological therapy of UIAs. Expert Commentary: In the recent years, there have been great advances in understanding the pathophysiology of UIAs and determining the rupture risk going beyond the traditional parameter of aneurysm size. Aneurysm morphology and hemodynamics play a pivotal role in growth and rupture. A true randomized trial for the management of UIAs is the need of the hour.
