Hemodynamic characteristics associated with cerebral aneurysm formation in patients with carotid occlusion

Nesfatin-1 inhibits cerebral aneurysms by activating Nrf2 and inhibiting NF-κB signaling

AIMS

Cerebral aneurysm (CA) has been considered one of the most common cerebrovascular diseases, affecting millions of people worldwide. A therapeutic agent is currently missing for the treatment of CA. Nesfatin-1 (Nes-1) is an 82-amino acid adipokine which possesses a wide range of biological functions. However, the physiological function of Nes-1 in CA is still unknown. Here, we aimed to assess the preventive effects of Nes-1 in the pathological development of CA and elucidate the mechanisms behind this.

METHODS

We used an elastase-induced CA model, accompanied by a high-salt diet to induce hypertension. Additionally, diverse experimental techniques, including Verhoeff-Van Gieson staining, real time PCR, enzyme-linked immuno sorbent assay (ELISA), and immunofluorescence staining, were employed to assess CA formation, gene and protein expression, as well as the macrophage infiltration.

RESULTS

Our results indicate that administration of Nes-1 significantly decreased the aneurysm size. Additionally, Nes-1 prevented inflammatory response by inhibiting the expression of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and monocyte chemoattractant protein 1 (MCP-1) at both the mRNA and protein levels in the Circle of Willis (COW) region. Also, the increased levels of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in the COW region were reduced by Nes-1. We found that Nes-1 administration suppressed the invasion of macrophages. Mechanistically, Nes-1 activated Nrf-2 by promoting its nuclear translocation but prevented the activation of the IκBα/NF-κB signaling pathway.

CONCLUSION

These findings suggest that Nes-1 might be used as a promising agent for the prevention of CA.

Carotid occlusion of a giant intracavernous aneurysm on a single functional internal carotid artery

The prevalence of intracranial aneurysms (IA) is higher in patients with stenosis of the internal carotid artery (ICA), the intracavernous internal carotid aneurysm is an intracranial aneurysm causing major functional and vital complications. We report the case of a 26-year-old man who consulted for a reduction in visual acuity, converging strabismus and ptosis of the right eye evolving for 7 months before his consultation, the various neuro-radiological examinations made it possible to identify diagnose a giant aneurysm of the right intracavernous internal carotid artery associated with severe stenosis of the contralateral internal carotid artery, hence the performance of a therapeutic arteriography consisting of an occlusion of this aneurysm. In summary, we describe successful management of a giant aneurysm of the intracavernous portion of a single functional internal carotid artery, while preserving optimal cerebral vascularization.

Evaluation of predictive models of aneurysm focal growth and bleb development using machine learning techniques

BACKGROUND

The presence of blebs increases the rupture risk of intracranial aneurysms (IAs).

OBJECTIVE

To evaluate whether cross-sectional bleb formation models can identify aneurysms with focalized enlargement in longitudinal series.

METHODS

Hemodynamic, geometric, and anatomical variables derived from computational fluid dynamics models of 2265 IAs from a cross-sectional dataset were used to train machine learning (ML) models for bleb development. ML algorithms, including logistic regression, random forest, bagging method, support vector machine, and K-nearest neighbors, were validated using an independent cross-sectional dataset of 266 IAs. The models' ability to identify aneurysms with focalized enlargement was evaluated using a separate longitudinal dataset of 174 IAs. Model performance was quantified by the area under the receiving operating characteristic curve (AUC), the sensitivity and specificity, positive predictive value, negative predictive value, F1 score, balanced accuracy, and misclassification error.

RESULTS

The final model, with three hemodynamic and four geometrical variables, along with aneurysm location and morphology, identified strong inflow jets, non-uniform wall shear stress with high peaks, larger sizes, and elongated shapes as indicators of a higher risk of focal growth over time. The logistic regression model demonstrated the best performance on the longitudinal series, achieving an AUC of 0.9, sensitivity of 85%, specificity of 75%, balanced accuracy of 80%, and a misclassification error of 21%.

CONCLUSIONS

Models trained with cross-sectional data can identify aneurysms prone to future focalized growth with good accuracy. These models could potentially be used as early indicators of future risk in clinical practice.

Treatment of aneurysmal artery with PED: A case report

RATIONALE

Pipeline embolization devices are a new treatment for intracranial aneurysms, especially irregular, giant aneurysms.

PATIENT CONCERNS

A 48-year-old female patient presented with a headache in the frontal part for 3 weeks.

DIAGNOSES

Cerebral computed tomographic angiography and magnetic resonance angiography showed a saccular aneurysm in the right internal carotid artery that wrapped the parent artery. Digital subtraction angiography provided images with 1 large saccular internal carotid aneurysm.

INTERVENTIONS

The patient was treated by flow diverter stent and coil embolization and dual antiplatelet therapy with aspirin and ticagrelor in the ICU and was discharged after 10 days without complications.

OUTCOMES

One year after interventional therapy, repeated digital subtraction angiography showed no recurrence of aneurysm and embolization well, and the patient reported improvement in neurological symptoms.

LESSONS

Aneurysmal parent artery is a rare phenomenon. The combination of flow diverter stents and coil embolization to treat cases with large saccular aneurysms has important clinical significance and this may provide a reference for clinical treatment of aneurysmal parent artery.

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

Objective

Hemodynamic characteristics play critical roles in aneurysm initiation and growth. This study aims to explore the effect of common hemodynamic parameters on the formation of visceral artery aneurysms (VAAs), especially those from the pancreaticoduodenal arteries or other uncommon locations, using real patients' models.

Methods

Three-dimension vessel models of 14 VAAs from 13 patients were selected and constructed from computed tomography angiography (CTA) images. Aneurysms were manually removed to perform computational fluid dynamics (CFD) simulations of the models before aneurysm formation. Flow field characteristics were obtained and compared at the aneurysm forming and para-aneurysm areas. Aneurysm forming models were categorized into high-wall-shear stress (WSS) and low-WSS groups according to WSS value at aneurysm forming versus para-aneurysm areas.

Results

Computational fluid dynamics analysis revealed that the high WSS group had significantly higher WSSmax (P = 0.038), higher time average WSS (TAWSS) (P = 0.011), higher WSS gradient (WSSG) (p = 0.036), as well as lower oscillatory shear index (OSI) (P = 0.022) compared to the low WSS group. Significant higher WSSmax (P = 0.003), TAWSS (P = 0.003), WSSG (P = 0.041) and lower OSI (P = 0.021) was observed at the aneurysm forming site compared to both upstream and downstream areas.

Conclusion

Both local increase and decrease of WSS and WSS gradient were observed for the visceral artery aneurysm forming area. Computational fluid dynamics analysis could shed light on the pathogenesis of visceral artery aneurysms at uncommon vessel locations.

Structural Remodeling of the Extracellular Matrix in Arteriogenesis: A Review

Lower extremity arterial occlusive disease (AOD) results in significant morbidity and mortality for the population, with up to 10% of patients ultimately requiring amputation. An alternative method for non-surgical revascularization which is yet to be fully understood is the optimization of the body's own natural collateral arterial network in a process known as arteriogenesis. Under conditions of conductance vessel stenosis or occlusion resulting in increased flow, shear forces, and pressure gradients within collaterals, positive remodeling occurs to increase the diameter and capacity of these vessels. The creation of a distal arteriovenous fistula (AVF) will drive increased arteriogenesis as compared to collateral formation with the occlusion of a conductance vessel alone by further increasing flow through these arterioles, demonstrating the capacity for arteriogenesis to form larger, more efficient collaterals beyond what is spontaneously achieved after arterial occlusion. Arteries rely on an extracellular matrix (ECM) composed of elastic fibers and collagens that provide stability under hemodynamic stress, and ECM remodeling is necessary to allow for increased diameter and flow conductance in mature arterial structures. When positive remodeling occurs, digestion of lamella and the internal elastic lamina (IEL) by matrix metalloproteinases (MMPs) and other elastases results in the rearrangement and thinning of elastic structures and may be replaced with disordered elastin synthesis without recovery of elastic function. This results in transmission of wall strain to collagen and potential for aneurysmal degeneration along collateral networks, as is seen in the pancreaticoduodenal artery (PDA) after celiac occlusion and inferior mesenteric artery (IMA) with concurrent celiac and superior mesenteric artery (SMA) occlusions. Further understanding into the development of collaterals is required to both better understand aneurysmal degeneration and optimize collateral formation in AOD.

Comparison of hemodynamic stress in healthy vessels after parent artery occlusion and flow diverter stent treatment for internal carotid artery aneurysm

OBJECTIVE

De novo aneurysms generally develop in healthy vessels after parent artery occlusion for large internal carotid artery (ICA) aneurysm, possibly owing to increased hemodynamic stress in the remaining vessels. In recent years, there has been a shift toward flow diverter stent treatment. However, there is a lack of direct evidence and data that prove this change in hemodynamic stress in healthy vessels after parent artery occlusion and flow diverter stent treatment. The authors compared hemodynamic stress in healthy-side vessels before and after parent artery occlusion and flow diverter treatments.

METHODS

The authors included patients who underwent 3D cine phase-contrast MRI before and after large ICA aneurysm treatment. Spatially and temporally averaged volume flow rates and spatially averaged systolic wall shear stress (WSS) in healthy-side ICA distal to the posterior communicating artery (C1 segment according to Fisher's classification) were measured before and after parent artery occlusion and flow diverter treatments.

RESULTS

Seventeen patients were included (5 patients in the parent artery occlusion group and 12 in the flow diverter group). At 1-2 months after treatment, median volume flow rate in healthy-side ICA increased from 5.36 ml/sec to 6.28 ml/sec (total increase 117%, p = 0.04) in the parent artery occlusion group and from 4.65 ml/sec to 4.93 ml/sec (total increase 106%, p = 0.02) in the flow diverter group. In the parent artery occlusion group, median WSS in the C1 segment of the healthy-side ICA increased from 3.91 Pa to 5.61 Pa (total increase 143%, p = 0.08); however, no significant increase was observed in the flow diverter group (4.29 Pa to 4.57 Pa [total increase 107%, p = 0.21]).

CONCLUSIONS

Postoperatively, volume flow rate and WSS in the C1 segment of the healthy-side ICA significantly increased in the parent artery occlusion group. Therefore, the parent artery occlusion group was more prone to de novo aneurysm than the flow diverter group.

Flow-related posterior cerebral artery aneurysms with internal carotid artery occlusions: An institutional series

BACKGROUND

Aneurysm formation after internal carotid artery (ICA) occlusion has been described in animal models and human case series with alteration of cerebral blood flow dynamics considered an aetiological risk factor. Such de novo aneurysms have seldom been described in the posterior cerebral artery (PCA) with the majority observed in the anterior circulation collateral pathways.

METHODS

We retrospectively reviewed our institutional database of posterior circulation aneurysms in patients with iatrogenic, atherosclerotic or congenital ICA occlusions. A comprehensive review of the online literature using the PubMed and Medline databases was performed to identify previous cases of PCA aneurysms that were considered 'flow-related'.

RESULTS

We present five patients with symptomatic or ruptured PCA aneurysms with ICA occlusions. Age at presentation ranged from 21-58 and aneurysm size from 3-12 mm. All cases had angiographic evidence of posterior-anterior flow via the ipsilateral posterior communicating artery (PComA). The clinical presentation, diagnostic imaging and management strategies are further discussed. A literature review identified only two previous reported cases.

CONCLUSION

To our knowledge this is the first single centre series of posterior circulation aneurysms in patients with ICA occlusions that are considered to be 'flow-related.' The natural history of these rare lesions is unclear and the best management and surveillance strategy requires a patient-tailored approach by an experienced neurovascular team.

Ruptured vertebrobasilar junction aneurysm unmasking subclavian steal syndrome

Background

Subclavian steal occurs due to stenosis or occlusion of the subclavian artery or innominate artery proximal to the origin of the vertebral artery. Often asymptomatic, the condition may be unmasked due to symptoms of vertebrobasilar insufficiency triggered by strenuous physical exercise involving the affected upper limb. The association of vertebrobasilar junction (VBJ) aneurysms with subclavian steal syndrome has been rarely reported. Hereby, we present a case of VBJ aneurysm associated with subclavian steal treated successfully with endovascular coiling.

Case Description

A 65-year-old female presented in the emergency department with acute severe headache and vomiting with no focal neurological deficits. Non-contrast computed tomography of the brain showed modified Fischer Grade 3 subarachnoid hemorrhage. Subsequent digital subtraction angiogram (DSA) showed VBJ aneurysm directed inferiorly with the left subclavian artery occlusion. There was retrograde filling of the left vertebral artery on right vertebral injection, confirming the diagnosis of subclavian steal. Balloon assisted coiling of the VBJ aneurysm was performed while gaining access through the stenotic left vertebral artery ostium which provided a more favorable hemodynamic stability to the coil mass.

Conclusion

Subclavian steal exerting undue hemodynamic stress on vertebrobasilar circulation can be an etiological factor for the development of the flow-related aneurysms. Access to the VBJ aneurysms may be feasible through the stenosed vertebral artery if angioplasty is performed before the coiling of the aneurysm.

Multiple flow-related intracranial aneurysms in the setting of contralateral carotid occlusion: Coincidence or association?

The prevalence of intracranial aneurysms (IAs) is higher in patients with internal carotid artery (ICA) stenosis, likely due to alterations in intracranial hemodynamics. Severe stenosis or occlusion of one ICA may result in increased demand and altered hemodynamics in the contralateral ICA, thus increasing the risk of contralateral IA formation. In this article, we discuss a relevant case and a comprehensive literature review as it pertains to the association of ICA stenosis and IA. Our patient was a 50-year-old female with a chronic asymptomatic right ICA occlusion who presented with diffuse subarachnoid hemorrhage. Emergent angiography revealed left-sided A1-A2 junction, paraclinoid, left middle cerebral artery (MCA) bifurcation, and left anterior temporal artery aneurysms. Brisk filling of the right anterior circulation through the anterior communicating artery was also identified, signifying increased demand on the left ICA circulation. Complete obliteration of all aneurysms was achieved with coil embolization and clipping. For our literature review, we searched the PubMed and EMBASE databases for case reports and case series, as well as references in previously published review articles that described patients with concurrent aneurysms and ICA stenosis. We selected articles that provided adequate information about the case presentations to compare aneurysm and patient characteristics. Our review revealed a higher number of patients with multiple aneurysms contralateral (25%) to rather than ipsilateral to (6%), the ICA stenosis. We discuss the pathogenesis and management of multiple flow-related IA in the context of the existing literature related to concurrent ICA stenosis and IA.

Three-Month Outcome of Carotid Artery Stenting in Patients with/without Coexistent Unruptured Intracranial Aneurysms

INTRODUCTION

Safety of carotid artery stenting (CAS) in patients having carotid stenosis with coexistent unruptured intracranial aneurysms (UIAs) is rarely reported. Thus, we studied the 3-month outcome of CAS in the presence of coexistent UIAs in our institution.

METHODS

A retrospective analysis of patients receiving CAS at our institution from September 2011 to December 2019 was carried out. Patients were stratified into 2 groups: group of CAS with UIAs (CAS-UIA) and group of CAS without UIAs (CAS). The main complications within 3 months after stenting were TIA, ischemic stroke, symptomatic intracranial hemorrhage (sICH), rupture of UIAs, and death. The baseline characteristics and complications of the 2 groups were compared.

RESULTS

Five hundred fifty-six patients (CAS, n = 468; CAS-UIA, n = 88) were included and 604 stenting procedures were performed. More patients had hypertension in the CAS-UIA group (87.5 vs. 73.7%, p = 0.006). There was no significant difference in TIAs, ischemic stroke, sICH, and death within 3 months after stenting between the CAS and CAS-UIA groups. None of the 113 coexistent UIAs detected in 88 patients had aneurysm rupture within 3 months after CAS.

CONCLUSIONS

In our large cohort of CAS patients, coexistent UIAs are not uncommon. Stenting of a carotid artery in the presence of coexistent UIAs could be conducted safely. Together with 3-month dual antiplatelet therapy, CAS did not increase the rupture risk of the coexistent UIAs within 3 months.

Occlusion of Extracranial-Intracranial Bypass Anastomosis-Associated Aneurysms Following Contralateral High-Flow Extracranial-Intracranial Bypass in a Patient with Impaired Cerebrovascular Reserve

BACKGROUND AND IMPORTANCE

Extracranial-intracranial (EC-IC) bypass anastomosis-associated aneurysms are rare sequelae of cerebral revascularization surgery. Although treatment paradigms are not well defined, clipping, trapping with revision bypass, and donor vessel ligation represent the most common microsurgical approaches.

CLINICAL PRESENTATION

A 53-yr-old male presented with cognitive decline, left extremity weakness, and left visual field blurriness. Computed tomographic angiography of head/neck demonstrated bilateral cervical internal carotid artery occlusion and magnetic resonance imaging of brain showed a small right parieto-occipital lobe infarct. The patient's symptoms worsened despite aggressive medical management. Therefore, a right superficial temporal artery to middle cerebral artery (STA-MCA) bypass was performed for flow augmentation. Follow-up digital subtraction angiography (DSA) approximately 1 yr after surgery noted 2 new aneurysms adjacent to the patent STA-MCA anastomosis. Perfusion imaging at that time showed persistently reduced blood flow in the left cerebral hemisphere. A left STA-MCA bypass was performed, and intraoperative blood flow measurements showed this to be a high-flow bypass. Follow-up DSA 4 mo later demonstrated involution of the right STA-MCA bypass and occlusion of the anastomosis-associated aneurysms with increased perfusion of the right cerebral hemisphere via collateral blood flow from the patent high-flow left STA-MCA bypass. At 7 mo following left STA-MCA bypass, the patient's neurological examination remained stable and perfusion imaging showed improved blood flow in the left cerebral hemisphere.

CONCLUSION

We present a unique case in which a high-flow left EC-IC bypass with robust contralateral collateral blood flow was associated with subsequent occlusion of a right EC-IC bypass and 2 anastomosis-associated aneurysms in a patient with bilateral impaired cerebrovascular reserve.

Cerebral arteriovenous malformation venous stenosis is associated with hemodynamic changes at the draining vein-venous sinus junction

Cerebral arteriovenous malformations (AVMs) are an uncommon vascular anomaly that carry the risk of rupture and hemorrhage. Several factors have been implicated in the propensity of an AVM to bleed. One such factor is stenosis of AVM draining veins, as impairment of the AVM venous drainage system is associated with increased risk of intracranial hemorrhage. Currently, our understanding of the pathogenesis of AVM venous outflow stenosis is limited, as there is insufficient data on the blood flow patterns and local hemodynamic parameters of these draining veins. The angioarchitecture of AVMs features a nidus lacking a high resistance capillary network. Accordingly, our previous studies on AVM arterial feeders have demonstrated an abnormally high flow volume rate along with low pulsatility and resistance indices on quantitative magnetic resonance angiography. As such, AVM vessels endure high, non-physiologic levels of flow that may partially contribute to ectasia or stenosis depending on whether wall shear stress (WSS) is high or low, respectively. We hypothesize that AVM venous outflow stenosis occurs most commonly near the junction of the draining vein and the dural venous sinus. Increased flow volume rate through the AVM circuit coupled with the variation in compliance and rigidity between the walls of the draining vein and the dural venous sinus likely create turbulence of blood flow. The resulting flow separation, low WSS, and departure from axially aligned, unidirectional flow may create atherogenic conditions that can be implicated in venous intimal hyperplasia and outflow stenosis. We have previously found there to be a significant association between intimal hyperplasia risk factors and venous outflow stenosis. Additionally, we have found a significant association between age and likelihood as well as degree of stenosis, suggesting a progressive disease process. Similar conditions have been demonstrated in the pathophysiology of stenosis of the carotid artery and dialysis arteriovenous fistulas. In both of these conditions, the use of computational fluid dynamics (CFD) has been employed to characterize the local hemodynamic features that contribute to the pathogenesis of intimal hyperplasia and stenosis. We recommend the utilization of CFD to characterize the anatomic and hemodynamic features of AVM venous outflow stenosis. An improved understanding of the possible causative features of venous outflow stenosis may impact how clinicians choose to manage the treatment of patients with AVMs.

The role of wall shear stress in the parent artery as an independent variable in the formation status of anterior communicating artery aneurysms

OBJECTIVES

The study aimed to determine which hemodynamic parameters independently characterize anterior communicating artery (AcomA) aneurysm formation and explore the threshold of wall shear stress (WSS) of the parent artery to better illustrate the correlation between the magnitude of WSS and AcomA aneurysm formation.

METHODS

Eighty-one patients with AcomA aneurysms and 118 patients without intracranial aneurysms (control population), as confirmed by digital subtraction angiography (DSA) from January 2014 to May 2017, were included in this cross-sectional study. Three-dimensional-DSA was performed to evaluate the morphologic characteristics of AcomA aneurysms. Local hemodynamic parameters were obtained using transcranial color-coded duplex (TCCD). Multivariate logistic regression and a two-piecewise linear regression model were used to determine which hemodynamic parameters are independent predictors of AcomA aneurysm formation and identify the threshold effect of WSS of the parent artery with respect to AcomA aneurysm formation.

RESULTS

Univariate analyses showed that the WSS (p < 0.0001), angle between the A1 and A2 segments of the anterior cerebral artery (ACA) (p < 0.001), hypertension (grade II) (p = 0.007), fasting blood glucose (FBG; > 6.0 mmol/L) (p = 0.005), and dominant A1 (p < 0.001) were the significant parameters. Multivariate analyses showed a significant association between WSS of the parent artery and AcomA aneurysm formation (p = 0.0001). WSS of the parent artery (7.8-12.3 dyne/cm²) had a significant association between WSS and aneurysm formation (HR 2.0, 95% CI 1.3-2.8, p < 0.001).

CONCLUSIONS

WSS ranging between 7.8 and 12.3 dyne/cm² independently characterizes AcomA aneurysm formation. With each additional unit of WSS, there was a one-fold increase in the risk of AcomA aneurysm formation.

KEY POINTS

• Multivariate analyses and a two-piecewise linear regression model were used to evaluate the risk factors for AcomA aneurysm formation and the threshold effect of WSS on AcomA aneurysm formation. • WSS ranging between 7.8 and 12.3 dyne/cm ² was shown to be a reliable hemodynamic parameter in the formation of AcomA aneurysms. The probability of AcomA aneurysm formation increased one-fold for each additional unit of WSS. • An ultrasound-based TCCD technique is a simple and accessible noninvasive method for detecting WSS in vivo; thus, it can be applied as a screening tool for evaluating the probability of aneurysm formation in primary care facilities and community hospitals because of the relatively low resource intensity.