Statistical evaluation of measured biomechanical properties of human brain aneurysm samples.

Background and purpose:

Human brain aneurysms may often prove fatal if not re­cognized in time and treated accordingly. The understanding of development and rupture of aneurysms can significantly be improved by the application of numerical modelling, which in turn, requires the knowledge of mechanical properties of vessel wall. This study aims to identify assumed differences with respect to age, sex, spatial orientation, and rupture by utilizing detailed statistical analysis of uniaxial tensile measurements of human brain aneurysm samples, performed by the authors in a previous project.

At surgery of 42 patients, aneu­rysm fundi were cut distally to the clip. In each case, depending on size, varying number of stripes (altogether 88) were prepared and uniaxial stress-strain measurements were performed. Quantities related to the capacity, energy absorption or stiffness were determined and statistically analysed.

The number of specimens in the aneurysm sample was sufficient to establish statistical differences with respect to sex and rupture (p<0.05). No significant differences were detected in orientation, though higher values of stresses and deformations were ob­tained in the circumferential direction com­pared to the meridional direction. 

Significant differences bet­ween sexes with respect to ultimate deformations were demonstrated according to expectation, and the hypothesis on equality of energy capacity could be supported. Similarity of curves with respect to specimen orientation was also observed and ruptured aneurysm sacs tended to be smaller in size. It seems that differences and trends described in this paper are realistic and need to be applied in numerical modelling.

Intraoperative neuromonitoring as real-time diagnostic for cerebral ischemia in endovascular treatment of ruptured brain aneurysms.

OBJECTIVE: To evaluate the diagnostic accuracy of intraoperative neurophysiological monitoring (IONM) during endovascular treatment (EVT) of ruptured intracranial aneurysms (rIA). METHODS: IONM and clinical data from 323 patients who underwent EVT for rIA from 2014-2019 were retrospectively reviewed. Significant IONM changes and outcomes were evaluated based on visual review of data and clinical documentation. RESULTS: Of the 323 patients undergoing EVT, significant IONM changes were noted in 30 patients (9.29%) and 46 (14.24%) experienced postprocedural neurological deficits (PPND). 22 out of 30 (73.33%) patients who had significant IONM changes experienced PPND. Univariable analysis showed changes in somatosensory evoked potential (SSEP) and electroencephalogram (EEG) were associated with PPND (p-values: <0.001 and <0.001, retrospectively). Multivariable analysis showed that IONM changes were significantly associated with PPND (Odd ratio (OR) 20.18 (95%CI:7.40-55.03, p-value: <0.001)). Simultaneous changes in both IONM modalities had specificity of 98.9% (95% CI: 97.1%-99.7%). While sensitivity when either modality had a change was 47.8% (95% CI: 33.9%-62.0%) to predict PPND. CONCLUSIONS: Significant IONM changes during EVT for rIA are associated with an increased risk of PPND. SIGNIFICANCE: IONM can be used confidently as a real time neurophysiological diagnostic guide for impending neurological deficits during EVT treatment of rIA.

Epithelial-mesenchymal transition related genes in unruptured aneurysms identified through weighted gene coexpression network analysis.

Intracranial aneurysm (IA) can cause fatal subarachnoid hemorrhage (SAH) after rupture, and identifying patients with unruptured IAs is essential for reducing SAH fatalities. The epithelial-mesenchymal transition (EMT) may be vital to IA progression. Here, identified key EMT-related genes in aneurysms and their pathogenic mechanisms via bioinformatic analysis. The GSE13353, GSE75436, and GSE54083 datasets from Gene Expression Omnibus were analyzed with limma to identify differentially expressed genes (DEGs) among unruptured aneurysms, ruptured aneurysms, and healthy samples. The results revealed that three EMT-related DEGs (ADIPOQ, WNT11, and CCL21) were shared among all groups. Coexpression modules and hub genes were identified via weighted gene co-expression network analysis, revealing two significant modules (red and green) and 14 EMT-related genes. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses suggested that cytokine interactions were closely related. Gene set enrichment analysis revealed that unruptured aneurysms were enriched for the terms "inflammatory response" and "vascular endothelial growth". Protein-protein interaction analysis identified seven key genes, which were evaluated with the GSE54083 dataset to determine their sensitivity and specificity. In the external validation set, we verified the differential expression of seven genes in unruptured aneurysms and normal samples. Together, these findings indicate that FN1, and SPARC may help distinguish normal patients from patients with asymptomatic IAs.

Intentional Bilateral Renal Artery Coverage During Ruptured Endovascular Paraanastomotic Pseudoaneurysm Repair.

The development of a paraanastomotic pseudoaneurysm is a serious complication after open prosthetic reconstruction of the aorta for occlusive or aneurysmal disease. Open repair of these lesions has previously been associated with high rates of morbidity and mortality. Endovascular repair may provide suitable treatment for proximal paraanastomotic aortic bypass graft pseudoaneurysms in patients who are poor candidates for open surgery. Bilateral renal artery coverage may be necessary to achieve adequate fixation and seal during life-threatening emergency cases of pseudoaneurysm rupture. Due to the infrequency of reported cases, the consequences of bilateral renal artery occlusion during these complex procedures are poorly understood. We present a case of a proximal paraanastomotic aortobifemoral bypass pseudoaneurysm rupture that was managed using endovascular repair with intentional coverage of both renal arteries. We also review the contemporary literature on endovascular management of paraanastomotic aneurysms and discuss the role of bilateral renal artery coverage in treating select patients with complex ruptured aortic pathology.

Cross-over Deployment of a Tapered Stent Graft to Repair a Ruptured Isolated Internal Iliac Aneurysm.

We report the case of a 72-year-old man who presented with a left ruptured internal iliac aneurysm (IIA). A percutaneous cross-over approach was used to coil-embolize the 3 distal branches of the IIA. A tapered endograft limb was then delivered via the right common femoral artery using a femorofemoral through-and-through cross-over approach. The widest part of the graft was deployed in the common iliac artery and the smallest in the external iliac artery. This percutaneous endovascular technique opens up new perspectives in emergency care for ruptured internal iliac artery aneurysms.

Long-term outcomes of endovascular treatment of isolated subclavian artery aneurysms.

OBJECTIVES: The aim of the present study was to review our institutional experience of endovascular treatment for isolated subclavian artery aneurysms and evaluate the long-term outcomes. METHODS: A retrospective review of all patients with isolated subclavian artery aneurysms who underwent endovascular treatment between March 2008 and March 2020 was performed. The demographics, aneurysmal characteristics, treatment strategies, and in-hospital and follow-up outcomes were recorded and then analyzed. RESULTS: From March 2008 to March 2020, 35 isolated subclavian artery aneurysms were endovascularly treated at our institution. Atherosclerosis was the most common cause of aneurysms in this series. Most aneurysms were intrathoracic (91.4%) and located at the right side (77.1%). There were 26 true aneurysms, seven pseudoaneurysms, and two ruptured isolated subclavian artery aneurysms. Five types of endovascular strategies were performed. Covered stent placement across the aneurysm was the most (54.3%) commonly used method. Technical success was achieved in all patients. The median postoperative in-hospital stay was 4.0 days (range, 1-15 days). One patient died after discharge but within 30 days of surgery due to myocardial infarction. The median follow-up time was 62.0 months (range, 3-132 months). No death, stroke, stent fractures, or severe upper limb ischemia developed during the follow-up period. The cumulative survival rate at five years was 97.1%. The overall complication rate was 25.7% and one-third of complications (8.6%) required reinterventions. CONCLUSIONS: Endovascular treatment for isolated subclavian artery aneurysms is safe, effective and technically achievable in most patients. Short- and long-term outcomes are promising. Reasonable and flexible use of covered stents can also get satisfactory outcomes in some complicated lesions such as isolated subclavian artery aneurysms located at the origin of the right subclavian artery, avoiding the huge surgical trauma caused by conventional open repair.

Hemodynamics in aneurysm blebs with different wall characteristics.

BACKGROUND: Blebs are important secondary structures of intracranial aneurysms associated with increased rupture risk and can affect local wall stress and hemodynamics. Mechanisms of bleb development and evolution are not clearly understood. We investigate the relationship between blebs with different wall characteristics and local hemodynamics and rupture sites. METHODS: Blebs with different wall appearances in intra-operative videos were analyzed with image-based computational fluid dynamics. Thin red blebs were compared against thick atherosclerotic/hyperplastic white/yellow blebs. Rupture points were identified in videos of ruptured aneurysms harboring blebs. RESULTS: Thin blebs tended to be closer to the inflow than atherosclerotic blebs of the same aneurysm (P=0.0234). Blebs near the inflow had higher velocity (P=0.0213), vorticity (P=0.0057), shear strain rate (P=0.0084), wall shear stress (WSS) (P=0.0085), and WSS gradient (P=0.0151) than blebs far from the inflow. In a subset of 12 ruptured aneurysms harboring blebs, rupture points were associated with thin blebs in 42% of aneurysms, atherosclerotic blebs in 25%, and were away from blebs in the remaining 33%. CONCLUSIONS: Not all blebs are equal; some have thin translucent walls while others have thick atherosclerotic walls. Thin blebs tend to be located closer to the inflow than atherosclerotic blebs. Blebs near the inflow are exposed to stronger flows with higher and spatially variable WSS than blebs far from the inflow which tend to have uniformly lower WSS. Aneurysms can rupture at thin blebs, atherosclerotic blebs, and even away from blebs. Further study of wall failure in aneurysms with different bleb types is needed.

Hemodynamic conditions that favor bleb formation in cerebral aneurysms.

BACKGROUND: Although it is generally believed that blebs represent weaker spots in the walls of intracranial aneurysms (IAs), it is largely unknown which aneurysm characteristics favor their development. OBJECTIVE: To investigate possible associations between aneurysm hemodynamic and geometric characteristics and the development of blebs in intracranial aneurysms. METHODS: A total of 270 IAs in 199 patients selected for surgical clipping were studied. Blebs were visually identified and interactively marked on patient-specific vascular models constructed from presurgical images. Blebs were then deleted from the vascular reconstruction to approximate the aneurysm before bleb formation. Computational fluid dynamics studies were performed in these models and in cases without blebs. Hemodynamic and geometric characteristics of aneurysms with and without blebs were compared. RESULTS: A total of 173 aneurysms had no blebs, while 97 aneurysms had a total of 122 blebs. Aneurysms favoring bleb formation had stronger (p<0.0001) and more concentrated inflow jets (p<0.0001), higher flow velocity (p=0.0061), more complex (p<0.0001) and unstable (p=0.0157) flow patterns, larger maximum wall shear stress (WSS; p<0.0001), more concentrated (p=0.0005) and oscillatory (p=0.0004) WSS distribution, and a more heterogeneous WSS field (p<0.0001), than aneurysms without blebs. They were also larger (p<0.0001), more elongated (p<0.0001), had wider necks (p=0.0002), and more distorted and irregular shapes (p<0.0001). CONCLUSIONS: Strong and concentrated inflow jets, high-speed, complex, and unstable flow patterns, and concentrated, oscillatory, and heterogeneous WSS patterns favor the formation of blebs in IAs. Blebs are more likely to form in large, elongated, and irregularly shaped aneurysms. These adverse characteristics could be considered signs of aneurysm instability when evaluating aneurysms for conservative observation or treatment.

Experience of managing superior mesenteric artery aneurysm and its midterm follow-up results with 18 cases.

OBJECTIVES: To characterize the clinical features, treatment, and prognosis of superior mesenteric artery aneurysms and provide evidence for clinical decision-making. METHODS: We retrospectively reviewed the diagnosis and treatment of 18 cases of superior mesenteric artery aneurysm admitted to our center from 2003 to 2020, including demographic data, risk factors, clinical manifestations, diagnosis, treatment strategies, and follow-up results. RESULTS: The average age of the patients was 49.1 years, and males accounted 83.3%. The development of the disease was associated with infection, hypertension, pancreatitis, and trauma, but no significant associations with atherosclerosis were noted by our results. Nine patients were diagnosed with true aneurysm, seven patients with pseudoaneurysm, and two patients with dissecting aneurysm. Rupture of aneurysm occurred in three patients (16.7%), and one of them died before surgery. The surgery success rate was 94.1%, and open surgery was performed on nine patients, endovascular surgery on three patients, and conservative treatment on three patients. The follow-up rate was 77.8% (14/18), and the average follow-up time was 48.2 months. The mortality and reintervention rate during follow-up was 0. The two-year patency rate of artificial vessels and covered stents was 50%. CONCLUSION: The clinical manifestations and features of superior mesenteric artery aneurysms vary between patients. Careful evaluation of vascular anatomy and personalized treatment strategy are critical in the management of superior mesenteric artery aneurysms. Midterm follow-up results of superior mesenteric artery aneurysms are satisfactory.

Impact of Ruptured Aneurysm Circulation on Mortality: A Nationwide Inpatient Sample Analysis.

OBJECTIVE: This study investigates the effect of aneurysm circulation on mortality and patient outcomes after aneurysmal subarachnoid hemorrhage (SAH) within the United States. METHODS: A retrospective cohort study was conducted using the Nationwide Inpatient Sample (NIS), a part of the Healthcare Cost and Utilization Project (HCUP), with ICD-10 codes for non-traumatic SAH between 2015-2016. Aneurysms were stratified as either anterior or posterior circulation. Multivariate logistic regression was used to find the impact of selected variables on the odds of mortality. RESULTS: The NIS reported 1,892 cases of non-traumatic SAH within the study period that were predominantly anterior circulation (82.6%), female (68.6%), white (57.7%), with mean age of 59.07 years, and in-hospital mortality of 21.4%. Anterior circulation aneurysms were associated with lower severity of initial illness (p = 0.014) but higher likelihood of vasospasm (p = 0.0006) than those of the posterior circulation. In a multivariate logistic regression analysis, mortality was associated with posterior circulation aneurysms (OR: 1.42; CI 95% 1.005-20.10, p = 0.047), increasing age (OR: 1.035; 95% CI 1.022-1.049; p < 0.0001), and shorter hospital stays (OR: 0.7838; 95% CI 0.758-0.811; p < 0.0001). Smoking history (OR: 0.825; 95% CI 0.573-1.187, p > 0.05) and vasospasm (OR: 1.005; 95% CI 0.648-1.558; p > 0.05) were not significantly associated with higher odds of mortality. CONCLUSIONS: Mortality following aneurysmal SAH is associated with posterior circulation aneurysms, and increasing age, but not smoking history or vasospasm. These findings may be useful for prognostication and counseling patients and families.

A pilot study using a machine-learning approach of morphological and hemodynamic parameters for predicting aneurysms enhancement.

PURPOSE: The development of straightforward classification methods is needed to identify unstable aneurysms and rupture risk for clinical use. In this study, we aim to investigate the relative importance of geometrical, hemodynamic and clinical risk factors represented by the PHASES score for predicting aneurysm wall enhancement using several machine-learning (ML) models. METHODS: Nine different ML models were applied to 65 aneurysm cases with 24 predictor variables. ML models were optimized with the training set using tenfold cross-validation with five repeats with the area under the curve (AUC) as cost parameter. Models were validated using the test set. Accuracy being significantly higher (p < 0.05) than the non-information rate (NIR) was used as measure of performance. The relative importance of the predictor variables was determined from a subset of five ML models in which this information was available. RESULTS: Best-performing ML model was based on gradient boosting (AUC = 0.98). Second best-performing model was based on generalized linear modeling (AUC = 0.80). The size ratio was determined as the dominant predictor for wall enhancement followed by the PHASES score and mean wall shear stress value at the aneurysm wall. Four ML models exhibited a statistically significant higher accuracy (0.79) than the NIR (0.58): random forests, generalized linear modeling, gradient boosting and linear discriminant analysis. CONCLUSIONS: ML models are capable of predicting the relative importance of geometrical, hemodynamic and clinical parameters for aneurysm wall enhancement. Size ratio, PHASES score and mean wall shear stress value at the aneurysm wall are of highest importance when predicting wall enhancement in cerebral aneurysms.

Anterior communicating artery complex fenestration combined with tandem aneurysm: a case report and literature review.

INTRODUCTION: Clinically, anterior communicating artery complex fenestration combined with fenestration-related aneurysms is rare, and combination of this condition with tandem aneurysms is even rarer. PATIENT CONCERNS: A case of a 43-year-old man with spontaneous subarachnoid hemorrhage. DIAGNOSIS: A computed tomography angiography examination revealed a fenestrated anterior communicating artery complex combined with 2 aneurysms. Then, a digital subtraction angiography examination was performed to further determine the diagnosis, which showed a complex anatomical structure of the local tissue. After the aneurysms ruptured, they were partially wrapped by a hematoma and compressed, which increased the difficulty of surgery. INTERVENTIONS: An endovascular interventional therapy method was chosen, and a simple coil was successfully inserted through the blood vessel into the tandem aneurysms to maintain the integrity of the anatomical structure. OUTCOMES: The patient recovered well postoperatively. An imaging review after the operation did not show the aneurysms, and the upper and lower branches were patent. CONCLUSION: Therefore, endovascular treatment is an appropriate choice for arterial fenestration combined with tandem aneurysms, once the aneurysms have ruptured.

Subclavian Artery Branch Pseudoaneurysm Rupture With Massive Hemothorax in a Patient With Neurofibromatosis Type 1.

Neurofibromatosis type 1 is a rare disorder that occurs secondary to pathogenic variants in the NF1 tumor suppressor gene on chromosome 17. Characteristic clinical manifestations include multiple hyperpigmented macules, axillary and inguinal freckling, optic gliomas, and numerous skin neurofibromas. Vasculopathies are a rare complication of this disease and can affect vessels ranging from the proximal aorta to small arterioles, with pathology including arterial stenosis, aneurysms, and arteriovenous malformations. Aneurysms in these patients are often asymptomatic, and most patients with this complication appear for treatment after vessel rupture. We describe a 33-year-old man with neurofibromatosis type 1 who presented with chest pain and was ultimately found to have a ruptured left subclavian artery branch pseudoaneurysm leading to a large hemothorax.

Inferior Pancreatico-Duodenal Artery Aneurysm with Superior Mesenteric Artery Stenosis.

Pancreatico-duodenal artery aneurysm (PDAA) associated with stenosis or occlusion of the celiac trunk is a rare condition. Furthermore, PDAAs associated with stenosis of the superior mesenteric artery (SMA) are even more uncommon, with only six cases reported in the literature. We report a case of a 61-year old male patient who presented with hematemesis, haematochezia and haemorrhagic shock. The upper gastrointestinal endoscopy revealed an ulcerous lesion at the third portion of the duodenum, without achieving the haemostasis. The emergency laparotomy (suture of the lesion and gastro-entero-anastomosis) permitted temporary haemostasis. Computed tomography angiography identified the PDAA ruptured into the third portion of the duodenum and the SMA stenosis at its origin; a dense network of collateral vessels was present. The patient was successfully managed with coil embolization. Short and mid-term follow-up were without incidents.

Impact of early surgery of ruptured cerebral aneurysms on vasospasm and hydrocephalus after SAH: Our preliminary results.

OBJECTIVE: Timing of surgical treatment of ruptured intracranial aneurysms has undergone a drastic change in the last few decades with preference for early surgery Our paper focuses specifically on the prognostic importance of timing of surgery, since early surgery of ruptured aneurysms provides immediately good clinical results. We present a series of cases operated in early and ultra early surgery, evaluating the technical aspects, the efficacy, the safety and the clinical results. PATIENTS AND METHODS: We retrospectively reviewed the clinical records and radiological imaging of patients treated for ruptured intracranial aneurysms who underwent early and ultra early clipping between January 2011 and April 2017 at our Institution. We included patients treated within the first 12 h and subsequently we divided our series in two subgroups based on the timing of surgery comparing the "early surgery" group (within 12 h) with the "ultra early surgery" group (within 6 h). RESULTS: Seventy-six (76) patients undergoing either early or ultra-early surgery for ruptured intracranial aneurysms have been reported Either early or ultra-early surgery showed a statistically favorable impact on reducing the incidence of both postoperative vasospasm and hydrocephalus. Ultra-early surgery group had the best outcome at the statistical analyses. (good postoperative 1Y GOSE.) CONCLUSIONS: We strongly believe that patients affected by ruptured intracranial aneurysms excluding Hunt and Hess grade V patients) should be treated as soon as possible and hence it should be considered as an emergency surgery. This approach prevents immediately a second bleeding of the aneurysm, allows to treat any associated condition of intracranial hypertension including hematomas and hydrocephalus and to use safely aggressive medical therapy such as hypertension.

Unilateral Lower Extremity Edema and Lymphorrhea as Manifestations of a Ruptured Iliac Artery Aneurysm and Arteriovenous Fistula.

An arteriovenous fistula is a rare complication of ruptured abdominal aortic or iliac artery aneurysms (IAAs). Its clinical symptoms depend on its size, with signs of heart failure dominating if the fistula is large. Herein, we present a case of arteriovenous fistula with an unusual presentation. An 86-year-old male patient presented with extreme lower extremity edema, skin erosion, and continuous lymphorrhea (starting 3 months prior). Despite the large fistula between the right common IAA and the left common iliac vein after the rupture of the aneurysm, he did not develop heart failure symptoms, as the large shunt was predominantly directed toward the left lower extremity due to iliac vein compression. Careful physical examination and a high index of suspicion could have contributed to an earlier diagnosis and management.

Endovascular Treatment of a Ruptured Superficial Femoral Artery Aneurysm in Behcet's Disease: Case Report and Literature Review.

PURPOSE: The aim of the study was to report the endovascular repair of a ruptured superficial femoral artery (SFA) aneurysm in a young patient with Behcet's disease and review the literature. CASE REPORT: A 43-year-old man with a known history of vasculo-Behcet's disease (v-BD) under daily immunosuppressive therapy presented with a ruptured aneurysm of the left SFA. The patient underwent urgent endovascular exclusion of the aneurysm using a self-expanding covered stent. Surgical cut-down followed by direct puncture of the SFA was preferred to percutaneous approach to reduce the risk of postoperative pseudoaneurysm formation. The procedure and postoperative recovery were successful. Doppler ultrasound performed at 3 months and computed tomography angiography performed at 6 months after the procedure confirmed aneurysm exclusion, the endograft patency, and the absence of aneurysm degeneration both at the level of surgical access and endograft landing zone. CONCLUSIONS: The endovascular treatment of ruptured lower limb aneurysms has been scarcely reported in the literature despite representing the less invasive option. A rare case of ruptured aneurysm SFA in a patient with v-BD was successfully treated with endovascular therapy (ET) and led to satisfactory midterm outcomes. ET offers encouraging results in terms of reduced vessel trauma and reduced postoperative complication rates.

Comparison of statistical learning approaches for cerebral aneurysm rupture assessment.

PURPOSE: Incidental aneurysms pose a challenge to physicians who need to decide whether or not to treat them. A statistical model could potentially support such treatment decisions. The aim of this study was to compare a previously developed aneurysm rupture logistic regression probability model (LRM) to other machine learning (ML) classifiers for discrimination of aneurysm rupture status. METHODS: Hemodynamic, morphological, and patient-related information of 1631 cerebral aneurysms characterized by computational fluid dynamics simulations were used to train support vector machines (SVMs) with linear and RBF kernel (RBF-SVM), k-nearest neighbors (kNN), decision tree, random forest, and multilayer perceptron (MLP) neural network classifiers for predicting the aneurysm rupture status. The classifiers' accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were evaluated and compared to the LRM using 249 test cases obtained from two external cohorts. Additionally, important variables were determined based on the random forest and weights of the linear SVM. RESULTS: The AUCs of the MLP, LRM, linear SVM, RBF-SVM, kNN, decision tree, and random forest were 0.83, 0.82, 0.80, 0.81, 0.76, 0.70, and 0.79, respectively. The accuracy ranged between 0.76 (decision tree,) and 0.79 (linear SVM, RBF-SVM, and MLP). Important variables for predicting the aneurysm rupture status included aneurysm location, the mean surface curvature, and maximum flow velocity. CONCLUSION: The performance of the LRM was overall comparable to that of the other ML classifiers, confirming its potential for aneurysm rupture assessment. To further improve the predictions, additional information, e.g., related to the aneurysm wall, might be needed.

When the Conventional Treatment Fails: A Rare Approach to Superior Mesenteric Arterial Embolization.

Retroperitoneal haemorrhage is a rare but potentially life-threatening event. It may occur either spontaneously or secondary to percutaneous vascular access procedures, trauma, or ruptured aortic, iliac, or mesenteric aneurysms. As a result, the clinical presentation is variable. Computed tomography and/or angiography are vital for diagnosis. Management may range from conservative treatment for stable patients to emergency laparotomy or embolization for catastrophic haemorrhage. Direct percutaneous puncture of a deep intra-abdominal pseudoaneurysm is an accepted but infrequently performed technique due to a number of diagnostic and technical challenges. We describe the successful percutaneous transabdominal angioembolization of a superior mesenteric artery rupture in a 77-year-old woman with a large retroperitoneal haematoma. This was performed after a conventional femoral transarterial approach was unsuccessful.

The biophysical role of hemodynamics in the pathogenesis of cerebral aneurysm formation and rupture.

The pathogenesis of intracranial aneurysms remains complex and multifactorial. While vascular, genetic, and epidemiological factors play a role, nascent aneurysm formation is believed to be induced by hemodynamic forces. Hemodynamic stresses and vascular insults lead to additional aneurysm and vessel remodeling. Advanced imaging techniques allow us to better define the roles of aneurysm and vessel morphology and hemodynamic parameters, such as wall shear stress, oscillatory shear index, and patterns of flow on aneurysm formation, growth, and rupture. While a complete understanding of the interplay between these hemodynamic variables remains elusive, the authors review the efforts that have been made over the past several decades in an attempt to elucidate the physical and biological interactions that govern aneurysm pathophysiology. Furthermore, the current clinical utility of hemodynamics in predicting aneurysm rupture is discussed.