Background In many cases, both the rupture rate of cerebral arteriovenous malformation (bAVM) in patients and the risk of endovascular or surgical treatment (when radiosurgery is not appropriate) are not low, it is important to assess the risk of rupture more cautiously before treatment. Based on the current high-risk predictors and clinical data, different sample sizes, sampling times and algorithms were used to build prediction models for the risk of hemorrhage in bAVM, and the accuracy and stability of the models were investigated. Our purpose was to remind researchers that there may be some pitfalls in developing similar prediction models. Methods The clinical data of 353 patients with bAVMs were collected. During the creation of prediction models for bAVM rupture, we changed the ratio of the training dataset to the test dataset, increased the number of sampling times, and built models for predicting bAVM rupture by the logistic regression (LR) algorithm and random forest (RF) algorithm. The area under the curve (AUC) was used to evaluate the predictive performances of those models. Results The performances of the prediction models built by both algorithms were not ideal (AUCs: 0.7 or less). The AUCs from the models built by the LR algorithm with different sample sizes were better than those built by the RF algorithm (0.70 vs 0.68, p < 0.001). The standard deviations (SDs) of the AUCs from both prediction models with different sample sizes displayed wide ranges (max range > 0.1). Conclusions Based on the current risk predictors, it may be difficult to build a stable and accurate prediction model for the hemorrhagic risk of bAVMs. Compared with sample size and algorithms, meaningful predictors are more important in establishing an accurate and stable prediction model.
BACKGROUND AND PURPOSE: Previous studies have reported that MCA bifurcation aneurysms usually emerge on inclined bifurcations; however, the reason is unclear. We designed this study to explore hemodynamic mechanisms that correlate with the initiation of MCA bifurcation aneurysms. MATERIALS AND METHODS: Fifty-four patients with unilateral MCA bifurcation aneurysms and 54 control patients were enrolled in this study after propensity score matching, and their clinical and CTA data were collected. We extracted the morphologic features of aneurysmal MCA bifurcations to build a simplified MCA bifurcation model and performed a computational fluid dynamics analysis. RESULTS: The presence of MCA aneurysms correlated with smaller parent-daughter angles of MCA bifurcations (P , .001). Aneurysmal MCA bifurcations usually presented with inclined shapes. The computational fluid dynamics analysis demonstrated that when arterial bifurcations became inclined, the high-pressure regions and low wall shear stress regions shifted from the apexes of the arterial bifurcations to the inclined daughter arteries, while the initial sites of MCA bifurcation aneurysms often overlapped with the shifted high-pressure regions and low wall shear stress regions. CONCLUSIONS: Our results suggest that the initiation of MCA bifurcation aneurysms may correlate with shifts of high-pressure regions and low wall shear stress regions that occur on inclined MCA bifurcations. ABBREVIATIONS: CFD ¼ computational fluid dynamics; HPR ¼ high-pressure region; LWSS ¼ low wall shear stress; LWSSR ¼ low wall shear stress region; PSM ¼ propensity score matching; RD ¼ ratio of diameter; ROC ¼ receiver operating characteristic T he occurrence of intracranial aneurysms is generally thought to be due to arterial wall weakening and/or the influence of hemodynamics. 1-4 Most studies on aneurysm etiology have focused on hemodynamics. Because the geometric shapes of intracranial arteries are diverse, their hemodynamics are also complex. Arterial bifurcations are common sites for intracranial aneurysms. The bifurcations are generally exposed to extreme hemodynamic stress; those with special morphologic features that significantly divert blood flow from the direction of flow of the parent vessels are a risk factor for aneurysm formation. 1,5,6 Previous studies have reported that the inclined MCA bifurcations with a widening angle are likely to harbor aneurysms, 7,8 but mechanisms by which the aneurysms develop on MCA bifurcations are controversial and need to be elucidated. 8-11 The present study was designed to extract the morphologic features of aneurysmal MCA bifurcations from clinical data, build a simplified MCA bifurcation model based on these extracted features, perform computational fluid dynamics (CFD) analysis on the aneurysmal MCA bifurcations and simplified models, and finally, to explore the hemodynamic mechanisms that could trigger aneurysm initiation. MATERIALS AND METHODS Case Selection and Matching Patients with unilateral MCA bifurcation aneurysms confirmed ...
Previous studies have reported that intracranial aneurysms frequently occur adjacent to the medial gap. However, the role of the medial gap in aneurysm formation is controversial. We designed this study to explore the potential role of the medial gap in aneurysm formation. Widened artery bifurcations with or without medial gaps were microsurgically created and pathologically stained in the carotid arteries of 30 rats. Numerical artery bifurcation models were constructed, and bidirectional fluid-solid interaction analyses were performed. Animal experiments showed that the apexes of widened bifurcations with a medial gap were prone to being insulted by blood flow compared to those without a medial gap. The bidirectional fluid-solid interaction analyses indicated that artery bifurcations with the medial gap exhibited higher wall shear stress (WSS) and von Mises stress (VMS) at the apex of the bifurcation. The disparity of stress between the gap and no-gap model was larger for widened bifurcations, peaking at 180° with a maximum of 1.9 folds. The maximum VMS and relatively high WSS were located at the junction between the medial gap and the adjacent arterial wall. Our results suggest that the medial gap at the widened arterial bifurcation may promote aneurysm formation.
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