Intracranial aneurysms: from vessel wall pathology to therapeutic approach

Circ_0008571 modulates the phenotype of vascular smooth muscle cells by targeting miR-145-5p in intracranial aneurysms

BACKGROUND

The dysfunction of human vascular smooth cells (hVSMCs) is significantly connected to the development of intracranial aneurysms (IAs). By suppressing the activity of microRNAs (miRNAs), circular RNAs (circRNAs) participate in IA pathogenesis. Nevertheless, the role of hsa_circ_0008571 in IAs remains unclear.

METHODS

circRNA sequencing was used to identify circRNAs from human IA tissues. To determine the function of circ_0008571, Transwell, wound healing, and cell proliferation assays were conducted. To identify the target of circ_0008571, the analyses of CircInteractome and TargetScan, as well as the luciferase assay were carried out. Furthermore, circ_0008571 knockdown and over-expression were performed to investigate its functions in IA development and the underlying molecular mechanisms.

RESULTS

Both hsa_circ_0008571 and Integrin beta 8 (ITGB8) were downregulated, while miR-145-5p transcription was elevated in the aneurysm wall of IAs patients compared to superficial temporal artery tissues. In vitro, cell migration and growth were dramatically suppressed after hsa_circ_0008571 overexpression. Mechanistically, has_circ_0008571 could suppress miR-145-5p activity by direct sponging. Moreover, we found that ITGB8 expression and the activation of the TGF-β-mediated signaling pathway were significantly enhanced.

CONCLUSION

The hsa_circ_0008571-miR-145-5p-ITGB8 axis plays an essential role in IA progression.

Somatic PDGFRB activating variants promote smooth muscle cell phenotype modulation in intracranial fusiform aneurysm

BACKGROUND

The fusiform aneurysm is a nonsaccular dilatation affecting the entire vessel wall over a short distance. Although PDGFRB somatic variants have been identified in fusiform intracranial aneurysms, the molecular and cellular mechanisms driving fusiform intracranial aneurysms due to PDGFRB somatic variants remain poorly understood.

METHODS

In this study, single-cell sequencing and immunofluorescence were employed to investigate the phenotypic changes in smooth muscle cells within fusiform intracranial aneurysms. Whole-exome sequencing revealed the presence of PDGFRB gene mutations in fusiform intracranial aneurysms. Subsequent immunoprecipitation experiments further explored the functional alterations of these mutated PDGFRB proteins. For the common c.1684 mutation site of PDGFRβ, we established mutant smooth muscle cell lines and zebrafish models. These models allowed us to simulate the effects of PDGFRB mutations. We explored the major downstream cellular pathways affected by PDGFRBY562D mutations and evaluated the potential therapeutic effects of Ruxolitinib.

RESULTS

Single-cell sequencing of two fusiform intracranial aneurysms sample revealed downregulated smooth muscle cell markers and overexpression of inflammation-related markers in vascular smooth muscle cells, which was validated by immunofluorescence staining, indicating smooth muscle cell phenotype modulation is involved in fusiform aneurysm. Whole-exome sequencing was performed on seven intracranial aneurysms (six fusiform and one saccular) and PDGFRB somatic mutations were detected in four fusiform aneurysms. Laser microdissection and Sanger sequencing results indicated that the PDGFRB mutations were present in smooth muscle layer. For the c.1684 (chr5: 149505131) site mutation reported many times, further cell experiments showed that PDGFRBY562D mutations promoted inflammatory-related vascular smooth muscle cell phenotype and JAK-STAT pathway played a crucial role in the process. Notably, transfection of PDGFRBY562D in zebrafish embryos resulted in cerebral vascular anomalies. Ruxolitinib, the JAK inhibitor, could reversed the smooth muscle cells phenotype modulation in vitro and inhibit the vascular anomalies in zebrafish induced by PDGFRB mutation.

CONCLUSION

Our findings suggested that PDGFRB somatic variants played a role in regulating smooth muscle cells phenotype modulation in fusiform aneurysms and offered a potential therapeutic option for fusiform aneurysms.

Phosphodiesterase in heart and vessels: from physiology to diseases

Phosphodiesterases (PDEs) are a superfamily of enzymes that hydrolyze cyclic nucleotides, including cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Both cyclic nucleotides are critical secondary messengers in the neurohormonal regulation in the cardiovascular system. PDEs precisely control spatiotemporal subcellular distribution of cyclic nucleotides in a cell- and tissue-specific manner, playing critical roles in physiological responses to hormone stimulation in the heart and vessels. Dysregulation of PDEs has been linked to the development of several cardiovascular diseases, such as hypertension, aneurysm, atherosclerosis, arrhythmia, and heart failure. Targeting these enzymes has been proven effective in treating cardiovascular diseases and is an attractive and promising strategy for the development of new drugs. In this review, we discuss the current understanding of the complex regulation of PDE isoforms in cardiovascular function, highlighting the divergent and even opposing roles of PDE isoforms in different pathogenesis.

Decoding the biology and clinical implication of neutrophils in intracranial aneurysm

OBJECTIVE

Abundant neutrophils have been identified in both ruptured and unruptured intracranial aneurysm (IA) domes, with their function and clinical implication being poorly characterized.

MATERIALS AND METHODS

We employed single-cell RNA sequencing (scRNA-Seq) datasets of both human and murine model, and external bulk mRNA sequencing datasets to thoroughly explore the features and functional heterogeneous of neutrophils infiltrating the IA dome.

RESULTS

We found that both unruptured and ruptured IA dome contain a substantial population of neutrophils, characterized by FCGR3B, G0S2, CSF3R, and CXCR2. These cells exhibited heterogeneity in terms of function and differentiation. Despite similar transcriptional activation, neutrophils in IA dome expressed a repertoire of gene programs that mimicked transcriptomic alterations observed from bone marrow to peripheral blood, showing self-similarity. In addition, the recruitment of neutrophils in unruptured IA was primarily mediated by monocytes/macrophages, and once ruptured, both neutrophils, and a specific subset of inflammatory smooth muscle cells (SMCs) were involved in the process. The receiver operator characteristic curve (ROC) analysis indicated that distinct neutrophil subclusters were associated with IA formation and rupture, respectively. By reviewing current studies, we found that neutrophils play a detrimental role to IA wall integrity through secreting specific ligands, ferroptosis driven by ALOX5AP and PTGS2, and the formation of neutrophil extracellular traps (NETs) mediated by PADI4.

INTERPRETATION

This study delineated the biology and potential clinical implications of neutrophils in IA dome and provided a reliable basis for future researches.

Clinical and angiographic characteristics of ruptured and unruptured distal cerebral aneurysms: a review of a large series of cases in a high-volume center

OBJECTIVE

To evaluate clinical, angiographic features, and endovascular approach of ruptured and unruptured distal intracranial aneurysms (DIAs).

METHODS

From January 2013 to February 2022, details of all consecutive intracranial aneurysms (IAs) treated endovascularly in our center were collected and retrospectively reviewed. IAs involving the anterior cerebral artery, middle cerebral artery, and posterior cerebral artery (distal to anterior communicating artery, limen insula, and P1 segment, respectively), and those distal to superior cerebellar artery, anterior-inferior cerebellar artery, and posterior inferior cerebellar artery's first segment were classified based on their etiology, location, size, and shape. Demographic, clinical, angiographic, and procedural variables, as well as follow-up outcomes were evaluated.

RESULTS

Of 2542 IAs, 151 (5.9%) DIAs were counted (average size 5.4±2.9 mm), including 61 (40.4%) unruptured and 90 (59.6%) ruptured. No difference in the aneurysmal size was observed, but aneurysms smaller than 4 mm were observed more frequently in the ruptured group (36.7% vs 18%; P=0.01). In addition, ruptured DIAs were more often non-saccular (40% vs 18%; P=0.004) and irregular (93.3% vs 59%; P<0.001), They were treated mostly by coiling, glue, and parent artery sacrifice (P=0.02, P=0.006, and P=0.001), whereas unruptured DIAs were treated by stent-assisted coiling and flow-diverter stents (P=0.001 and P<0.001, respectively), without any differences in occlusion (81.6% vs 82.5%) and recanalization (21.1% vs 17.5%) rates. Procedure-related complications occurred in 20/151 (13.2%) patients, without any differences between subgroups. Ruptured DIAs were more often re-treated (18.4% vs 5.3%, P=0.02). In multivariate analyses, irregular shape appeared as an independent predictor of ruptured presentation (OR=8.1, 95% CI 3.0 to 21.7; P<0.001).

CONCLUSIONS

Compared with unruptured DIAs, ruptured DIAs were more often non-saccular, irregular, and smaller than 4 mm. Despite different therapeutical approaches, ruptured and unruptured DIAs presented comparable occlusion and recanalization rates.

Decoding the Cell Atlas and Inflammatory Features of Human Intracranial Aneurysm Wall by Single-Cell RNA Sequencing

BACKGROUND

Intracranial aneurysm (IA) is common and occasionally results in life-threatening hemorrhagic strokes. However, the cell architecture and inflammation in the IA dome remain less understood.

METHODS AND RESULTS

Single-cell RNA sequencing was performed on ruptured and unruptured human IA domes for delineating the cell atlas, gene expression perturbations, and inflammation features. Two external bulk mRNA sequencing-based data sets and serological results of 126 patients were collected for validation. As a result, a total of 21 332 qualified cells were captured. Vascular cells, including endothelial cells, smooth muscle cells, fibroblasts, and pericytes, were assigned in extremely sparse numbers (4.84%), and were confirmed by immunofluorescence staining. Pericytes, characterized by ABCC9 and HIGD1B, were identified in the IA dome for the first time. Abundant immune cells were identified, with the proportion of monocytes/macrophages and neutrophils being remarkably higher in ruptured IA. The lymphocyte compartment was also thoroughly categorized. By leveraging external data sets and machine learning algorithms, macrophages were robustly associated with IA rupture, irrespective of their polarization status. The single nucleotide polymorphism rs2280543, which is identified in East Asian populations, was associated with macrophage metabolic reprogramming through regulating TALDO1 expression.

CONCLUSIONS

This study provides insights into the cellular architecture and inflammatory features in the IA dome and may enlighten novel therapeutics for unruptured IA.

Arterial Bypass in the Treatment of Complex Middle Cerebral Artery Aneurysms: Lessons Learned from Forty Patients

OBJECTIVE

Complex middle cerebral artery (MCA) aneurysms incorporating parent or branching vessels are often not amenable to standard microsurgical clipping or endovascular embolization treatments. We aim to discuss the treatment of such aneurysms via a combination of surgical revascularization and aneurysm exclusion based on our institutional experience.

METHODS

Thirty-four patients with complex MCA aneurysms were treated with bypass and aneurysm occlusion, 5 with surgical clipping or wrapping only, and 1 with aneurysm excision and primary reanastomosis. Bypasses included superficial temporal artery (STA)-MCA, double-barrel STA-MCA, occipital artery-MCA, and external carotid artery-MCA. After bypass, aneurysms were treated by surgical clipping, Hunterian ligation, trapping, or coil embolization.

RESULTS

The average age at diagnosis was 46 years. Of the aneurysms, 67% were large and most involved the MCA bifurcation. Most bypasses performed were STA-MCA bypasses, 12 of which were double-barrel. There were 2 wound-healing complications. All but 2 of the aneurysms treated showed complete occlusion at the last follow-up. There were 3 hemorrhagic complications, 3 graft thromboses, and 4 ischemic insults. The mean follow-up was 73 months. Of patients, 83% reported stable or improved symptoms from presentation and 73% reported a functional status (Glasgow Outcome Scale score 4 or 5) at the latest available follow-up.

CONCLUSIONS

Cerebral revascularization by bypass followed by aneurysm or parent artery occlusion is an effective treatment option for complex MCA aneurysms that cannot be safely treated by standard microsurgical or endovascular techniques. Double-barrel bypass consisting of 2 STA branches to 2 MCA branches yields adequate flow replacement in most cases.

Plasma levels of CD36 and glutathione as biomarkers for ruptured intracranial aneurysm

Evidence has proved that intracranial aneurysm (IA) formation and rupture might be closely related to inflammatory response and oxidative stress. Our objective was to evaluate the potential of CD36 and glutathione (GSH) as biomarkers for IA. In this study, the enzyme-linked immunosorbent assay was used to measure the plasma levels of CD36 and GSH in 30 IA patients and 30 healthy controls. Then, correlation analysis, receiver operating characteristic (ROC) curve, and logistic regression analysis were performed. The results showed that the plasma level of CD36 in IA patients was significantly higher than that in the control group (P < 0.0001), and plasma GSH was significantly lower compared with that in the control group (P < 0.0001). ROC analysis showed that CD36 and GSH had high sensitivity (90.0 and 96.6%) and specificity (96.6 and 86.6%) for IA diagnosis. The combined sensitivity and specificity achieved were 100 and 100%, respectively. The plasma levels of CD36 and GSH did not show a significant correlation with age, the Glasgow Coma Scale, Hunter-Hess score, aneurysm size, aneurysm height, aneurysm neck, and aspect ratio. The AUC of the logistic regression model based on CD36 and GSH was 0.505. Our results suggested that the combination of plasma CD36 and GSH could serve as potential biomarkers for IA rupture.

Black blood MRI sequences in the acute management of ruptured and unruptured intracranial aneurysms

We present an illustrative case series in which high spatial resolution black blood (BB) MRI sequences were used as an adjunct in the acute management of intracranial aneurysms with diagnostic uncertainty regarding rupture status. Several acute management dilemmas are discussed including the surveillance of previously treated ruptured intracranial aneurysms, identifying culprit lesion(s) amongst multiple ruptured intracranial aneurysms, and risk stratifying incidental unruptured intracranial aneurysms. We present our experience which supports the evaluation of this vessel wall imaging technique in larger multi-centre observational studies. MR imaging was performed on a 3.0 Tesla Siemens Somatom Vida system and sequences used included: Susceptibility Weighted Imaging, Diffusion Weighted Imaging & 3D T1 pre- and post-contrast-enhanced BB sequences.

Prevalence and prognosis of acute ischemic stroke coexisting with unruptured intracranial aneurysms

Objectives

The prevalence of unruptured intracranial aneurysms (UIAs) in the acute ischemic stroke (AIS) cohort is probably higher than in the general population. This study investigated the prevalence of UIAs in AIS patients and the management risk and prognosis when treating AIS.

Methods

From January 2020 to January 2023, we conducted a single-center retrospective study at Tianjin Huanhu Hospital. Each patient underwent both brain MRI and MRA/CTA to diagnose AIS and UIAs. Clinical, radiologic, and therapeutic data during hospitalization and prognosis were analyzed. Propensity-score matching (PSM) was performed to evaluate the risk of in-hospital adverse events, unfavorable outcomes at discharge when receiving post-stroke treatment and stroke recurrence.

Results

In all, 2,181 AIS patients were included, of whom 270 had UIAs (12.4%; 95%CI 11.0-13.8%). From the unmatched and matched cohort, the incidence of in-hospital adverse events and unfavorable outcomes at discharge in patients with UIAs were not significantly different; the risk of stroke recurrence was significantly higher in patients with UIAs than in those without (unmatched: aHR, 1.71 [1.08-2.70]; matched: aHR, 2.55 [1.16-5.58]). Multivariable Cox regression models showed that aneurysm size and the presence of homoregional infarction associated with higher risk of recurrence (unmatched: aHR, 1.31 [1.21-1.41] and aHR, 3.50 [1.52-8.10]; matched: aHR, 1.28 [1.18-1.40]; p < 0.001 and aHR, 3.71 [1.12-12.34]).

Conclusion

The UIAs may not increase the risk of in-hospital adverse events and unfavorable outcomes at discharge in receiving post-stroke treatment, but it may associated with a high risk of stroke recurrence.

CypD induced ROS output promotes intracranial aneurysm formation and rupture by 8-OHdG/NLRP3/MMP9 pathway

Reactive Oxygen Species (ROS) are widely accepted as a pernicious factor in the progression of intracranial aneurysm (IA), which is eminently related to cell apoptosis and extracellular matrix degradation, but the mechanism remains to be elucidated. Recent evidence has identified that enhancement of Cyclophilin D (CypD) under stress conditions plays a critical role in ROS output, thus accelerating vascular destruction. However, no study has confirmed whether cypD is a detrimental mediator of cell apoptosis and extracellular matrix degradation in the setting of IA development. Our data indicated that endogenous cypD mRNA was significantly upregulated in human IA lesions and mouse IA wall, accompanied by higher level of ROS, MMPs and cell apoptosis. CypD-/- remarkably reversed vascular smooth muscle cells (VSMCs) apoptosis and elastic fiber degradation, and significantly decreased the incidence of aneurysm and ruptured aneurysm, together with the downregulation of ROS, 8-OHdG, NLRP3 and MMP9 in vivo and vitro. Furthermore, we demonstrated that blockade of cypD with CsA inhibited the above processes, thus preventing IA formation and rupture, these effects were highly dependent on ROS output. Mechanistically, we found that cypD directly interacts with ATP5B to promote ROS release in VSMCs, and 8-OHdG directly bind to NLRP3, which interacted with MMP9 to increased MMP9 level and activity in vivo and vitro. Our data expound an unexpected role of cypD in IA pathogenesis and an undescribed 8-OHdG/NLRP3/MMP9 pathway involved in accelerating VSMCs apoptosis and elastic fiber degradation. Repressing ROS output by CypD inhibition may be a promising therapeutic strategy for prevention IA development.

Intracranial Aneurysms and Genetics: An Extensive Overview of Genomic Variations, Underlying Molecular Dynamics, Inflammatory Indicators, and Forward-Looking Insights

This review initiates by outlining the clinical relevance of IA, underlining the pressing need to comprehend its foundational elements. We delve into the assorted risk factors tied to IA, spotlighting both environmental and genetic influences. Additionally, we illuminate distinct genetic syndromes linked to a pronounced prevalence of intracranial aneurysms, underscoring the pivotal nature of genetics in this ailment's susceptibility. A detailed scrutiny of genome-wide association studies allows us to identify key genomic changes and locations associated with IA risk. We further detail the molecular and physiopathological dynamics instrumental in IA's evolution and escalation, with a focus on inflammation's role in affecting the vascular landscape. Wrapping up, we offer a glimpse into upcoming research directions and the promising horizons of personalized therapeutic strategies in IA intervention, emphasizing the central role of genetic insights. This thorough review solidifies genetics' cardinal role in IA, positioning it as a cornerstone resource for professionals in the realms of neurology and genomics.

Molecular Magnetic Resonance Imaging of Aneurysmal Inflammation Using a Redox Active Iron Complex

OBJECTIVES

Inflammation plays a key role in driving brain aneurysmal instability and rupture, but clinical tools to noninvasively differentiate between inflamed and stable aneurysms are lacking. We hypothesize that imaging oxidative changes in the aneurysmal microenvironment driven by myeloid inflammatory cells may represent a noninvasive biomarker to evaluate rupture risk. In this study, we performed initial evaluation of the oxidatively activated probe Fe-PyC3A as a tool for magnetic resonance imaging (MRI) of inflammation in a rabbit model of saccular aneurysm.

MATERIALS AND METHODS

The difference in longitudinal relaxivity ( r1 ) in reduced and oxidized states of Fe-PyC3A was measured in water and blood plasma phantoms at 3 T. A rabbit saccular aneurysm model was created by endovascular intervention/elastinolysis with subsequent decellularization in situ. Rabbits were imaged at 4 weeks (n = 4) or 12 weeks (n = 4) after aneurysmal induction, when luminal levels of inflammation reflected by the presence of myeloperoxidase positive cells are relatively high and low, respectively, using a 3 T clinical scanner. Both groups were imaged dynamically using a 2-dimensional T1-weighted fast field echo pulse MRI sequence before and up to 4 minutes postinjection of Fe-PyC3A. Dynamic imaging was then repeated after an injection of gadobutrol (0.1 mmol/kg) as negative control probe. Rabbits from the 12-week aneurysm group were also imaged before and 20 minutes and 3 hours after injection of Fe-PyC3A using an axial respiratory gated turbo-spin echo (TSE) pulse sequence with motion-sensitized driven equilibrium (MSDE) preparation. The MSDE/TSE imaging was repeated before, immediately after dynamic acquisition (20 minutes postinjection), and 3 hours after injection of gadobutrol. Aneurysmal enhancement ratios (ERs) were calculated by dividing the postinjection aneurysm versus skeletal muscle contrast ratio by the preinjection contrast ratio. After imaging, the aneurysms were excised and inflammatory infiltrate was characterized by fluorometric detection of myeloperoxidase activity and calprotectin immunostaining, respectively.

RESULTS

In vitro relaxometry showed that oxidation of Fe-PyC3A by hydrogen peroxide resulted in a 15-fold increase of r1 at 3 T. Relaxometry in the presence of blood plasma showed no more than a 10% increase of r1 , indicating the absence of strong interaction of Fe-PyC3A with plasma proteins. Dynamic imaging with Fe-PyC3A generated little signal enhancement within the blood pool or adjacent muscle but did generate a transient increase in aneurysmal ER that was significantly greater 4 weeks versus 12 weeks after aneurysm induction (1.6 ± 0.30 vs 1.2 ± 0.03, P < 0.05). Dynamic imaging with gadobutrol generated strong aneurysmal enhancement, but also strong enhancement of the blood and muscle resulting in smaller relative ER change. In the 12-week group of rabbits, MSDE/TSE imaging showed that ER values measured immediately after dynamic MRI (20 minutes postinjection) were significantly higher ( P < 0.05) in the case of Fe-PyC3A (1.25 ± 0.06) than for gadobutrol injection (1.03 ± 0.03). Immunohistochemical corroboration using anticalprotectin antibody showed that leukocyte infiltration into the vessel walls and luminal thrombi was significantly higher in the 4-week group versus 12-week aneurysms (123 ± 37 vs 18 ± 7 cells/mm 2 , P < 0.05).

CONCLUSIONS

Magnetic resonance imaging using Fe-PyC3A injection in dynamic or delayed acquisition modes was shown to generate a higher magnetic resonance signal enhancement in aneurysms that exhibit higher degree of inflammation. The results of our pilot experiments support further evaluation of MRI using Fe-PyC3A as a noninvasive marker of aneurysmal inflammation.

Increased PDGFRB and NF-κB signaling caused by highly prevalent somatic mutations in intracranial aneurysms

Intracranial aneurysms (IAs) are a high-risk factor for life-threatening subarachnoid hemorrhage. Their etiology, however, remains mostly unknown at present. We conducted screening for sporadic somatic mutations in 65 IA tissues (54 saccular and 11 fusiform aneurysms) and paired blood samples by whole-exome and targeted deep sequencing. We identified sporadic mutations in multiple signaling genes and examined their impact on downstream signaling pathways and gene expression in vitro and an arterial dilatation model in mice in vivo. We identified 16 genes that were mutated in at least one IA case and found that these mutations were highly prevalent (92%: 60 of 65 IAs) among all IA cases examined. In particular, mutations in six genes (PDGFRB, AHNAK, OBSCN, RBM10, CACNA1E, and OR5P3), many of which are linked to NF-κB signaling, were found in both fusiform and saccular IAs at a high prevalence (43% of all IA cases examined). We found that mutant PDGFRBs constitutively activated ERK and NF-κB signaling, enhanced cell motility, and induced inflammation-related gene expression in vitro. Spatial transcriptomics also detected similar changes in vessels from patients with IA. Furthermore, virus-mediated overexpression of a mutant PDGFRB induced a fusiform-like dilatation of the basilar artery in mice, which was blocked by systemic administration of the tyrosine kinase inhibitor sunitinib. Collectively, this study reveals a high prevalence of somatic mutations in NF-κB signaling pathway-related genes in both fusiform and saccular IAs and opens a new avenue of research for developing pharmacological interventions.

Interruption of TRPC6-NFATC1 signaling inhibits NADPH oxidase 4 and VSMCs phenotypic switch in intracranial aneurysm

Intracranial aneurysm (IA) is a frequent cerebrovascular disorder with unclear pathogenesis. The vascular smooth muscle cells (VSMCs) phenotypic switch is essential for IA formation. It has been reported that Ca2+ overload and excessive reactive oxygen species (ROS) are involved in VSMCs phenotypic switch. The transient receptor potential canonical 6 (TRPC6) and NADPH oxidase 4 (NOX4) are the main pathway to participate in Ca2+ overload and ROS production in VSMCs. Ca2+ overload can activate calcineurin (CN), leading to nuclear factor of activated T cell (NFAT) dephosphorylation to regulate the target gene's transcription. We hypothesized that activation of TRPC6-NFATC1 signaling may upregulate NOX4 and involve in VSMCs phenotypic switch contributing to the progression of IA. Our results showed that the expressions of NOX4, p22phox, p47phox, TRPC6, CN and NFATC1 were significantly increased, and VSMCs underwent a significant phenotypic switch in IA tissue and cellular specimens. The VIVIT (NFATC1 inhibitor) and BI-749327 (TRPC6 inhibitor) treatment reduced the expressions of NOX4, p22phox and p47phox and the production of ROS, and significantly improved VSMCs phenotypic switch in IA rats and cells. Consistent results were obtained from IA Trpc6 knockout (Trpc6-/-) mice. Furthermore, the results also revealed that NFATC1 could regulate NOX4 transcription by binding to its promoter. Our findings reveal that interrupting the TRPC6-NFATC1 signaling inhibits NOX4 and improves VSMCs phenotypic switch in IA, and regulating Ca2+ homeostasis may be an important therapeutic strategy for IA.

Cervical Artery Dissection

OBJECTIVE

Cervical artery dissection is a common cause of stroke in young adults. This article reviews the pathophysiology, etiology and risk factors, evaluation, management, and outcomes of spontaneous cervical artery dissection.

LATEST DEVELOPMENTS

Cervical artery dissection is believed to be a multifactorial disease, with environmental factors serving as possible triggers in patients who have a genetic predisposition to dissection formation. Cervical artery dissection can cause local symptoms or ischemic events, such as ischemic stroke or transient ischemic attack. Neuroimaging is used to confirm the diagnosis; classic findings include a long tapered arterial stenosis or occlusion, dissecting aneurysm, intimal flap, double lumen, or intramural hematoma. Patients with cervical artery dissection who present with an acute ischemic stroke should be evaluated for IV thrombolysis, endovascular therapy eligibility, or both. Antithrombotic therapy with either anticoagulation or antiplatelet treatment is used to prevent stroke from cervical artery dissection. The risk of recurrent ischemia appears low and is mostly limited to the first two weeks after symptom onset.

ESSENTIAL POINTS

Cervical artery dissection is a known cause of ischemic strokes. Current data show no difference between the benefits and risks of anticoagulation versus antiplatelet therapy in the acute phase of symptomatic extracranial cervical artery dissection, thereby supporting the recommendation that clinicians can prescribe either treatment. Further research is warranted to better understand the pathophysiology and long-term outcomes of cervical artery dissection.

Image quality improvements for brain soft tissue in neuro-endovascular treatments: A novel dual-axis "butterfly" trajectory for optimized Cone-Beam CT

PURPOSE

Cone-beam computed tomography (CBCT) is useful in the diagnosis of complications after neuro-endovascular treatment. However, the image quality of conventional CBCT is inferior to that of conventional CT. To solve this problem, a dual-axis butterfly CBCT available with an angiography suite has been developed. This study aimed to evaluate the image quality of this dual-axis butterfly CBCT compared to the conventional CBCT in the same patient.

METHOD

We prospectively included patients who underwent scheduled neuro-endovascular treatment and performed conventional CBCT and novel dual-axis butterfly CBCT as a postoperative examination. We evaluated artifacts, brain contrast, and cortico-medullary junctions on a scoring system using a 5-point scale in which lower scores indicate better image quality. In addition, the white matter/gray matter ratio was calculated in selected brain lobe regions.

RESULTS

Forty-seven cases (94 paired images) were enrolled. The novel dual-axis butterfly CBCT had significantly fewer supratentorial and infratentorial artifacts in the artifact evaluation. Similarly, contrast and cortico-medullary junction discrimination in the cerebral hemispheres scored significantly better in the butterfly scan in all regions. The white matter/gray matter ROI ratio was significantly higher in the novel dual-axis butterfly CBCT in the frontal and occipital lobes but not in the temporal lobe.

CONCLUSIONS

Compared to conventional CBCT, the novel dual-axis butterfly CBCT showed supratentorial and infratentorial artifact reduction as well as improved contrast with the brain parenchyma and cerebrospinal fluid space and white matter/gray matter discrimination ability.

Increased macrophage M2/M1 ratio is associated with intracranial aneurysm rupture

PURPOSE

Intracranial aneurysm (IA) rupture results in one of the most severe forms of stroke, with severe neurological sequelae. Inflammation appears to drive aneurysm formation and progression with macrophages playing a key role in this process. However, less is known about their involvement in aneurysm rupture. This study is aimed at demonstrating how relationship between the M1 (pro-inflammatory) and M2 (reparative) macrophage subtypes affect an aneurysm's structure resulting in its rupture.

METHODS

Forty-one saccular aneurysm wall samples were collected during surgery including 13 ruptured and 28 unruptured aneurysm sacs. Structural changes were evaluated using histological staining. Macrophages in the aneurysm wall were quantified and defined as M1 and M2 using HLA-DR and CD163 antibodies. Aneurysm samples were divided into four groups according to the structural changes and the M2/1 ratio. Data were analyzed using the Mann-Whitney U test.

RESULTS

This study has demonstrated an association between the severity of structural changes of an aneurysm with inflammatory cell infiltration within its wall and subsequent aneurysm rupture. More severe morphological changes and a significantly higher number of inflammatory cells were observed in ruptured IAs (p < 0.001). There was a prevalence of M2 macrophage subtypes within the wall of ruptured aneurysms (p < 0.001). A subgroup of unruptured IAs with morphological and inflammatory changes similar to ruptured IAs was observed. The common feature of this subgroup was the presence of an intraluminal thrombus.

CONCLUSIONS

The degree of inflammatory cell infiltration associated with a shift in macrophage phenotype towards M2 macrophages could play an important role in structural changes of the aneurysm wall leading to its rupture.

Qualitative and quantitative wall enhancement associated with unstable intracranial aneurysms: a meta-analysis

Background

Unstable intracranial aneurysms (UIAs) are more likely to rupture and cause serious consequences. Evaluating the stability of unruptured aneurysms facilitates clinical management stratification.

Purpose

To compare and evaluate the predictive performance of qualitative and quantitative wall enhancement (aneurysmal wall enhancement [AWE], circumferential aneurysmal wall enhancement [CAWE], wall enhancement ratio [WER]) on high-resolution magnetic resonance imaging (MRI) of the vessel wall to predict the presence of UIA.

Material and Methods

Original articles describing the depiction of aneurysmal wall enhancement on 3.0-T or 1.5-T high-resolution vessel wall imaging were retrieved from the Web of Science, Medline/PubMed, the Cochrane Library, and EMBASE databases up to 15 February 2022. The combined sensitivity, specificity, and summary area under the receiver operating characteristic curve (AUC) were calculated, and meta-regression analysis was performed.

Results

In total, 12 original articles involving 1619 intracranial aneurysms (IAs) were included. The combined sensitivity and specificity of AWE, CAWE, and WER were 91% and 67%, 59% and 83%, and 86% and 75%, respectively, in the diagnosis of UIA. The summary AUC values of these items were, in order from high to low, 0.88 (WER), 0.84 (AWE), and 0.77 (CAWE), and the differences among them were significant ( z = 2.976, P = 0.003 and z = 2.950, P = 0.003). The meta-regression analysis identified average size and 2D/3D magnetic imaging technology as possible sources of heterogeneity.

Conclusion

Qualitative and quantitative wall enhancement showed moderate accuracy in predicting UIA, and WER had the highest accuracy among them in this meta-analysis. Two covariates were found to explain the heterogeneity.

Multinational Genome-Wide Association Study and Functional Genomics Analysis Implicates Decreased SIRT3 Expression Underlying Intracranial Aneurysm Risk

BACKGROUND

The genetic mechanisms regulating intracranial aneurysm (IA) formation and rupture are largely unknown. To identify germline-genetic risk factors for IA, we perform a multinational genome-wide association study (GWAS) of individuals from the United Kingdom, Finland, and Japan.

OBJECTIVE

To identify a shared, multinational genetic basis of IA.

METHODS

Using GWAS summary statistics from UK Biobank, FinnGen, and Biobank Japan, we perform a meta-analysis of IA, containing ruptured and unruptured IA cases. Logistic regression was used to identify IA-associated single-nucleotide polymorphisms. Effect size was calculated using the coefficient r , estimating the contribution of the single-nucleotide polymorphism to the genetic variance of the trait. Genome-wide significance was set at 5.0 × 10 -8 . Expression quantitative trait loci mapping and functional genomics approaches were used to infer mechanistic consequences of implicated variants.

RESULTS

Our cohort contained 155 154 individuals (3132 IA cases and 152 022 controls). We identified 4 genetic loci reaching genome-wide: rs73392700 ( SIRT3 , effect size = 0.28, P = 4.3 × 10 -12 ), rs58721068 ( EDNRA , effect size = -0.20, P = 4.8 × 10 -12 ), rs4977574 ( AL359922.1 , effect size = 0.18, P = 7.9 × 10 -12 ), and rs11105337 ( ATP2B1 , effect size = -0.15, P = 3.4 × 10 -8 ). Expression quantitative trait loci mapping suggests that rs73392700 has a large effect size on SIRT3 gene expression in arterial and muscle, but not neurological, tissues. Functional genomics analysis suggests that rs73392700 causes decreased SIRT3 gene expression.

CONCLUSION

We perform a multinational GWAS of IA and identify 4 genetic risk loci, including 2 novel IA risk loci ( SIRT3 and AL359922.1 ). Identification of high-risk genetic loci across ancestries will enable population-genetic screening approaches to identify patients with IA.

Remodeling of the Neurovascular Unit Following Cerebral Ischemia and Hemorrhage

Formulated as a group effort of the stroke community, the transforming concept of the neurovascular unit (NVU) depicts the structural and functional relationship between brain cells and the vascular structure. Composed of both neural and vascular elements, the NVU forms the blood-brain barrier that regulates cerebral blood flow to meet the oxygen demand of the brain in normal physiology and maintain brain homeostasis. Conversely, the dysregulation and dysfunction of the NVU is an essential pathological feature that underlies neurological disorders spanning from chronic neurodegeneration to acute cerebrovascular events such as ischemic stroke and cerebral hemorrhage, which were the focus of this review. We also discussed how common vascular risk factors of stroke predispose the NVU to pathological changes. We synthesized existing literature and first provided an overview of the basic structure and function of NVU, followed by knowledge of how these components remodel in response to ischemic stroke and brain hemorrhage. A greater understanding of the NVU dysfunction and remodeling will enable the design of targeted therapies and provide a valuable foundation for relevant research in this area.

Deep Phenotyping of T-Cells Derived From the Aneurysm Wall in a Pediatric Case of Subarachnoid Hemorrhage

Intracranial aneurysms (IAs) are very rare in children, and the characteristics of the T-cells in the IA wall are largely unknown. A comatose 7-years-old child was admitted to our center because of a subarachnoid hemorrhage due to a ruptured giant aneurysm of the right middle cerebral artery. Two days after the aneurysm clipping the patient was fully awake with left hemiparesis. T-cells from the IA wall and from peripheral blood of this patient were analyzed by multi-dimensional flow cytometry. Unbiased analysis, based on the use of FlowSOM clustering and dimensionality reduction technique UMAP, indicated that there was virtually no overlap between circulating and tissue-infiltrating T-cells. Thus, naïve T-cells and canonical memory T-cells were largely restricted to peripheral blood, while CD4^-CD8^-T-cells were strongly enriched in the IA wall. The unique CD4⁺, CD8⁺ and CD4^-CD8^-T-cell clusters from the IA wall expressed high levels of CCR5, Granzyme B and CD69, displaying thus characteristics of cytotoxic and tissue-resident effector cells. Low Ki67 expression indicated that they were nevertheless in a resting state. Among regulatory T-cell subsets, Eomes⁺Tr1-like cells were strongly enriched in the IA wall. Finally, analysis of cytokine producing capacities unveiled that the IA wall contained poly-functional T-cells, which expressed predominantly IFN-γ, TNF and IL-2. CD4⁺T-cells co-expressed also CD40L, and produced some IL-17, GM-CSF and IL-10. This report provides to our knowledge the first detailed characterization of the human T-cell compartment in the IA wall.

Fluid-structure interaction (FSI) simulation for studying the impact of atherosclerosis on hemodynamics, arterial tissue remodeling, and initiation risk of intracranial aneurysms

The biomechanical and hemodynamic effects of atherosclerosis on the initiation of intracranial aneurysms (IA) are not yet clearly discovered. Also, studies for the observation of hemodynamic variation due to atherosclerotic stenosis and its impact on arterial remodeling and aneurysm genesis remain a controversial field of vascular engineering. The majority of studies performed are relevant to computational fluid dynamic (CFD) simulations. CFD studies are limited in consideration of blood and arterial tissue interactions. In this work, the interaction of the blood and vessel tissue because of atherosclerotic occlusions is studied by developing a fluid and structure interaction (FSI) analysis for the first time. The FSI presents a semi-realistic simulation environment to observe how the blood and vessels' structural interactions can increase the accuracy of the biomechanical study results. In the first step, many different intracranial vessels are modeled for an investigation of the biomechanical and hemodynamic effects of atherosclerosis in arterial tissue remodeling. Three physiological conditions of an intact artery, the artery with intracranial atherosclerosis (ICAS), and an atherosclerotic aneurysm (ACA) are employed in the models with required assumptions. Finally, the obtained outputs are studied with comparative and statistical analyses according to the intact model in a normal physiological condition. The results show that existing occlusions in the cross-sectional area of the arteries play a determinative role in changing the hemodynamic behavior of the arterial segments. The undesirable variations in blood velocity and pressure throughout the vessels increase the risk of arterial tissue remodeling and aneurysm formation.

Increased Number of Passes and Double Stent Retriever Technique Induces Cumulative Injury on Arterial Wall After Mechanical Thrombectomy in a Swine Model

The number of stentriever passes during endovascular thrombectomy impacts clinical outcomes in acute ischemic stroke. Previous studies suggest that the simultaneous double stent retriever technique (DSRT) could improve the efficacy and reduce the number of passes. We aim to analyze the degree of vessel wall injury according to the number of passes and technique (single vs. simultaneous devices). Histological changes were evaluated in renal arteries (RAs) of swine models after thrombectomy (1, 2, or 3 passes) with single stent (SSRT) and DSRT. Thrombectomy passes were performed in 12 RA: 3 samples from each artery were studied by optical microscopy to assess a vascular damage score. All thirty-six samples showed endothelial denudation and different degrees of damage in the deepest layers of the arterial wall; however, all arteries remained patent by the time of assessment. In all cases, the degree of vascular injury increased with the number of passes. Compared with a SSRT, DSRT showed a higher severity of histological damage corresponding to the damage caused by 1.4 SSRT passes. However, in distal arteries, vascular damage was relatively similar when comparing SSRT with multiple passes and DSRT with one pass. The degree of vessel injury increases with the number of passes. Even though histological damage per pass was 1.4 higher with DSRT than SSRT, short-term vessel patency was not compromised after up to 3 DSRT passes. Further studies are needed to characterize the risk-benefit ratio of the DSRT in routine clinical practice.

Impinging Flow Induces Expression of Monocyte Chemoattractant Protein-1 in Endothelial Cells Through Activation of the c-Jun N-terminal Kinase/c-Jun/p38/c-Fos Pathway

OBJECTIVE

Monocyte chemoattractant protein-1 (MCP-1) is an important regulator of the formation and development of intracranial aneurysms. This study explored the molecular mechanisms underlying the induction of MCP-1 and related inflammatory factors in human umbilical vein endothelial cells (HUVECs) under hemodynamic conditions.

METHODS

A modified T chamber was used to simulate fluid flow at the bifurcation of the artery and wall shear stress on HUVECs in vitro. Changes in HUVECs were analyzed in response to impinging flow. And HUVECs without impinging flow were used as the control group. Protein expression levels of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38, activator protein-1, and MCP-1 were detected by Western blot, and the messenger RNA expression levels of MCP-1, interleukin (IL)-1β, and IL-6 were determined by quantitative reverse transcription polymerase chain reaction.

RESULTS

Under impinging flow, the phosphorylation levels of ERK, JNK, and p38, as well as the protein levels of MCP-1, c-Jun, and c-Fos, increased. The messenger RNA expression of MCP-1, IL-1β, and IL-6 also increased in HUVECs. Pretreatment of the HUVECs with inhibitors of JNK and p38 significantly attenuated the increased expression of MCP-1, IL-1β, and IL-6, while ERK inhibitors had no obvious effect.

CONCLUSIONS

Under impinging flow, MCP-1 and inflammatory factors are regulated through the JNK/c-Jun/p38/c-Fos pathway and participate in EC inflammation.

Telerobotic neurovascular interventions with magnetic manipulation

Advances in robotic technology have been adopted in various subspecialties of both open and minimally invasive surgery, offering benefits such as enhanced surgical precision and accuracy with reduced fatigue of the surgeon. Despite the advantages, robotic applications to endovascular neurosurgery have remained largely unexplored because of technical challenges such as the miniaturization of robotic devices that can reach the complex and tortuous vasculature of the brain. Although some commercial systems enable robotic manipulation of conventional guidewires for coronary and peripheral vascular interventions, they remain unsuited for neurovascular applications because of the considerably smaller and more tortuous anatomy of cerebral arteries. Here, we present a teleoperated robotic neurointerventional platform based on magnetic manipulation. Our system consists of a magnetically controlled guidewire, a robot arm with an actuating magnet to steer the guidewire, a set of motorized linear drives to advance or retract the guidewire and a microcatheter, and a remote-control console to operate the system under real-time fluoroscopy. We demonstrate our system's capability to navigate narrow and winding pathways both in vitro with realistic neurovascular phantoms representing the human anatomy and in vivo in the porcine brachial artery with accentuated tortuosity for preclinical evaluation. We further demonstrate telerobotically assisted therapeutic procedures including coil embolization and clot retrieval thrombectomy for treating cerebral aneurysms and ischemic stroke, respectively. Our system could enable safer and quicker access to hard-to-reach lesions while minimizing the radiation exposure to physicians and open the possibility of remote procedural services to address challenges in current stroke systems of care.

Atypical intracranial aneurysms: spectrum of imaging findings in computed tomography and magnetic resonance imaging

We aim to describe demographics, clinical presentation, and spectrum of CT and MRI features suggestive of atypical intracranial aneurysms. The imaging protocols used for the diagnosis of intracranial aneurysms were thoroughly reviewed, including different CT and MRI protocols. We classified atypical aneurysms according to their location, size, clinical presentation, and specific imaging features. Dissecting aneurysms are one of the causes of stroke in young adults that may show intimal flap and double lumen. Traumatic intracranial aneurysms are a rare but serious complication of head injuries. Mycotic aneurysms are small and multiple at distal branch points with a high risk of rupture. Aneurysms with vasculitis are fusiform with a wide neck at a non-branch point that may be associated with vessel wall enhancement. Atherosclerotic aneurysms are usually large fusiform that affect large arteries. Oncotic aneurysms are relatively rare. They were reported to occur in patients with left atrial myxoma. Our study represented a wide spectrum of atypical intracranial aneurysms with their detailed diagnostic imaging findings on MRI and CT including newly introduced MRI sequences, which greatly influenced early diagnosis and timely management.

Endovascular Biopsy of Vertebrobasilar Aneurysm in Patient With Polyarteritis Nodosa

Background and Purpose: The management of unruptured intracranial aneurysms remains controversial. The decisions to treat are heavily informed by estimated risk of bleeding. However, these estimates are imprecise, and better methods for stratifying the risk or tailoring treatment strategy are badly needed. Here, we demonstrate an initial proof-of-principle concept for endovascular biopsy to identify the key molecular pathways and gene expression changes associated with aneurysm formation. We couple this technique with single cell RNA sequencing (scRNAseq) to develop a roadmap of the pathogenic changes of a dolichoectatic vertebrobasilar aneurysm in a patient with polyarteritis nodosa.

Methods: Endovascular biopsy and fluorescence activated cell sorting was used to isolate the viable endothelial cells (ECs) using the established techniques. A single cell RNA sequencing (scRNAseq) was then performed on 24 aneurysmal ECs and 23 patient-matched non-aneurysmal ECs. An integrated panel of bioinformatic tools was applied to determine the differential gene expression, enriched signaling pathways, and cell subpopulations hypothesized to drive disease pathogenesis.

Results: We identify a subset of 7 (29%) aneurysm-specific ECs with a distinct gene expression signature not found in the patient-matched control ECs. A gene set enrichment analysis identified these ECs to have increased the expression of genes regulating the leukocyte-endothelial cell adhesion, major histocompatibility complex (MHC) class I, T cell receptor recycling, tumor necrosis factor alpha (TNFα) response, and interferon gamma signaling. A histopathologic analysis of a different intracranial aneurysm that was later resected yielded a diagnosis of polyarteritis nodosa and positive staining for TNFα.

Conclusions: We demonstrate feasibility of applying scRNAseq to the endovascular biopsy samples and identify a subpopulation of ECs associated with cerebral aneurysm in polyarteritis nodosa. Endovascular biopsy may be a safe method for deriving insight into the disease pathogenesis and tailoring the personalized treatment approaches to intracranial aneurysms.

Pharmacological inhibition of epidermal growth factor receptor attenuates intracranial aneurysm formation by modulating the phenotype of vascular smooth muscle cells

Aim

To study the effect of pharmacological inhibition of epidermal growth factor receptor (EGFR) on intracranial aneurysm (IA) initiation.

Methods

Human IA samples were analyzed for the expression of p‐EGFR and alpha smooth muscle actin (α‐SMA) by immunofluorescence (IF). Rat models of IA were established to evaluate the ability of the EGFR inhibitor, erlotinib, to attenuate the incidence of IA. We analyzed anterior cerebral artery tissues by pathological and proteomic detection for the expression of p‐EGFR and relevant proteins, and vessel casting was used to evaluate the incidence of aneurysms in each group. Rat vascular smooth muscle cells (VSMCs) and endothelial cells were extracted and used to establish an in vitro co‐culture model in a flow chamber with or without erlotinib treatment. We determined p‐EGFR and relevant protein expression in VSMCs by immunoblotting analysis.

Results

Epidermal growth factor receptor activation was found in human IA vessel walls and rat anterior cerebral artery walls. Treatment with erlotinib markedly attenuated the incidence of IA by inhibiting vascular remodeling and pro‐inflammatory transformation of VSMC in rat IA vessel walls. Activation of EGFR in rat VSMCs and phenotypic modulation of rat VSMCs were correlated with the strength of shear stress in vitro, and treatment with erlotinib reduced phenotypic modulation of rat VSMCs. In vitro experiments also revealed that EGFR activation could be induced by TNF‐α in human brain VSMCs.

Conclusions

These results suggest that EGFR plays a critical role in the initiation of IA and that the EGFR inhibitor erlotinib protects rats from IA initiation by regulating phenotypic modulation of VSMCs.

Treatment of acute aneurysmal subarachnoid haemorrhage with primary flow diversion: 5-year single-centre experience

AIM

To evaluate the safety and efficacy of treatment of patients presenting with acute aneurysmal subarachnoid haemorrhage (SAH) with primary flow-diverting stents (FDS; with or without adjuncts), with comparison to the published literature.

MATERIALS AND METHODS

A retrospective single-centre review was undertaken of prospectively obtained data on patients treated for SAH over a 60-month period. Of 354 patients treated for SAH during that time period, 24 patients with a total of 25 aneurysms were identified. Baseline patient demographics were recorded and clinical and imaging outcomes assessed.

RESULTS

Eighty-eight per cent (22/25) of the aneurysms were completely occluded (Raymond-Roy 1) at mean 12-month follow-up. The minor complication rate was 12.5% (3/24) without permanent morbidity. Mortality rate was 4% (1/25) after one patient died following aneurysmal rebleed on day 7 post-procedure. Forty-two per cent (10/24) of patients had a high-pressure shunt placed prior to endovascular treatment, no haemorrhagic complications of neurosurgical intervention were observed.

CONCLUSION

The necessity of dual antiplatelet therapy (DAPT) therapy when deploying FDS will rightly continue to limit their use in the acutely ruptured setting to a case-by-case basis whereby other treatment options are deemed unsafe. Methods employed to minimise subsequent haemorrhagic risks from DAPT in these patients may be worthy of further investigation.

Preclinical testing platforms for mechanical thrombectomy in stroke: a review on phantoms, in-vivo animal, and cadaveric models

Preclinical testing platforms have been instrumental in the research and development of thrombectomy devices. However, there is no single model which fully captures the complexity of cerebrovascular anatomy, physiology, and the dynamic artery-clot-device interaction. This article provides a critical review of phantoms, in-vivo animal, and human cadaveric models used for thrombectomy testing and provides insights into the strengths and limitations of each platform. Articles published in the past 10 years that reported thrombectomy testing platforms were identified. Characteristics of each test platform, such as intracranial anatomy, artery tortuosity, vessel friction, flow conditions, device-vessel interaction, and visualization, were captured and benchmarked against human cerebral vessels involved in large-vessel occlusion stroke. Thrombectomy phantoms have been constructed from silicone, direct 3D-printed polymers, and glass. These phantoms represent oversimplified patient-specific cerebrovascular geometry but enable adequate visualization of devices and clots under appropriate flow conditions. They do not realistically mimic the artery-clot interaction. For the animal models, arteries from swine, canines, and rabbits have been reported. These models can reasonably replicate the artery-clot-device interaction and have the unique value of evaluating the safety of thrombectomy devices. However, the vasculature geometries are substantially less complex and flow conditions are different from human cerebral arteries. Cadaveric models are the most accurate vascular representations but with limited access and challenges in reproducibility of testing conditions. Multiple test platforms should be likely used for comprehensive evaluation of thrombectomy devices. Interpretation of the testing results should take into consideration platform-specific limitations.

Aneurysmal Subarachnoid Hemorrhage in Patients with Coronavirus Disease 2019 (COVID-19): A Case Series

Objective

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is a pressing public health issue. Although most cases do not result in severe illness requiring hospitalization, there is increasing evidence that SARS-CoV-2–induced inflammation can exacerbate pre-existing diseases. We sought to describe the characteristics of patients with aneurysmal subarachnoid hemorrhage who were actively or very recently infected with SARS-CoV-2.

Methods

We reviewed subarachnoid hemorrhage cases of patients who also were positive for SARS-CoV-2 at 5 high-volume cerebrovascular centers in the United States from March 2020 to January 2021. Cases of aneurysmal subarachnoid hemorrhage were analyzed.

Results

A total of 10 patients were identified, consisting of 5 women (50%) and 5 men (50%). Median age was 38.5 years. Four of the 10 patients (40%) were asymptomatic with respect to SARS-CoV-2–related symptoms, 3 patients (30%) had mild-to-moderate symptoms, and 3 patients (30%) had severe coronavirus disease 2019 (COVID-19), with pneumonia and sepsis. Of the 10 cases, 4 had dissecting pseudoaneurysms (40%), 3 in the posterior circulation and 1 in the anterior circulation. Among 6 saccular/blister aneurysms, 4 (67%) were ≤4 mm in largest diameter.

Conclusions

Our experience with aneurysmal subarachnoid hemorrhage in patients positive for COVID-19 reveals a possibly distinct pattern compared with traditional aneurysmal subarachnoid hemorrhage, namely a high frequency of small aneurysms, dissecting pseudoaneurysms, and young patients.

SDF-1α/CXCR4 Pathway Mediates Hemodynamics-Induced Formation of Intracranial Aneurysm by Modulating the Phenotypic Transformation of Vascular Smooth Muscle Cells

The objective of this study is to explore the role of the SDF-1α/CXCR4 pathway in the development of intracranial aneurysm (IA) induced by hemodynamic forces. We collected 12 IA and six superficial temporal artery samples for high-throughput sequencing, hematoxylin and eosin staining, and immunohistochemistry to examine vascular remodeling and determine the expression of the components of the SDF-1α/CXCR4 pathway, structural proteins (α-SMA and calponin) of vascular smooth muscle cells (VSMCs), and inflammatory factors (MMP-2 and TNF-α). Computational fluid dynamics (CFD) was used for hemodynamic analysis. Mouse IA model and dynamic co-culture model were established to explore the mechanism through which the SDF-1α/CXCR4 pathway regulates the phenotypic transformation of VSMCs in vivo and in vitro. We detected a significant elevation of SDF-1α and CXCR4 in IA, which was accompanied by vascular remodeling in the aneurysm wall (i.e., the upregulation of inflammatory factors, MMP-2 and TNF-α, and the downregulation of contractile markers, α-SMA and calponin). In addition, hemodynamic analysis revealed that compared with unruptured aneurysms, ruptured aneurysms were associated with lower wall shear stress and higher MMP-2 expression. In vivo and in vitro experiments showed that abnormal hemodynamics could activate the SDF-1α/CXCR4, P38, and JNK signaling pathways to induce the phenotypic transformation of VSMCs, leading to IA formation. Hemodynamics can induce the phenotypic transformation of VSMCs and cause IA by activating the SDF-1α/CXCR4 signaling pathway.

Correlation of Aneurysmal Wall Enhancement of Unruptured Intracranial Aneurysms on High-Resolution Vessel-Wall Imaging With Clinical Indices and Surgical Findings

BACKGROUND

Many physicians consider aneurysmal wall enhancement (AWE) on high resolution-vessel wall imaging (HR-VWI) as an imaging biomarker of unstable unruptured intracranial aneurysms (UIAs).

OBJECTIVE

To evaluate the clinical value of different AWE signal intensities (SIs) by assessing the correlation between the AWE SIs and surgical findings and rupture risk assessment tools.

METHODS

Twenty-six patients with 34 aneurysms who underwent surgical clipping were included. The corrected AWE SI was calculated by comparing T1-weighted images with post-gadolinium enhanced T1-weighted images. The correlation of AWE with the population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage from another aneurysm, site of aneurysm (PHASES) and earlier subarachnoid hemorrhage, location of the aneurysm, age >60 years, population, size of the aneurysm, shape of the aneurysm (ELAPSS) scores was evaluated using correlation and linear regression analysis. To quantify the surgical findings, the average color value of the aneurysms expressed in the CIELCh system was measured. Δh, color difference from yellow, was used for statistical analysis.

RESULTS

The mean age of the patients and aneurysm size were 64.08 yr and 6.95 mm, respectively. The mean AWE SI, PHASES and ELAPSS scores, and Δh were 22.30, 8.41, 20.32, and 41.36, respectively. The coefficients of correlation of AWE SI with the PHASES and ELAPSS scores and Δh were 0.526, 0.563, and -0.431. We found that the AWE SI affected the PHASES (β = 0.430) and ELAPSS scores (β = 0.514) and Δh (β = -0.427) in simple linear regression analysis.

CONCLUSION

The AWE on HR-VWI was correlated with the PHASES and ELAPSS scores and the color. The stronger the AWE, the higher were the PHASES and ELAPSS scores and the more abnormal was the color. The AWE might indicate the degree of inflammation.

Rothia dentocariosa causing intracranial mycotic aneurysm and ischaemic stroke

We describe a case of subacute bacterial endocarditis and mycotic brain aneurysm caused by Rothia dentocariosa due to untreated dental caries. R. dentocariosa is a rare cause of endocarditis that has a high incidence of aneurysmal and haemorrhagic complications. All patients with intracranial aneurysms who have signs of systemic infection should be considered to have mycotic aneurysms until proven otherwise. Dental habits should be included in regular medical assessment and dental care should be considered for patients presenting with infectious symptoms.

Associations between haemodynamics and wall enhancement of intracranial aneurysm

BACKGROUND AND PURPOSE

Previous studies have reported about inflammation processes (IPs) that play important roles in aneurysm formation and rupture, which could be driven by blood flow. IPs can be identified using aneurysmal wall enhancement (AWE) on high-resolution black-blood MRI (BB-MRI) and blood flow haemodynamics can be demonstrated by four-dimensional-flow MRI (4D-flow MRI). Thus, this study investigated the associations between AWE and haemodynamics in unruptured intracranial aneurysms (IA) by combining 4D-flow MRI and high-resolution BB-MRI.

MATERIALS AND METHODS

Between April 2014 and October 2017, 48 patients with 49 unruptured IA who underwent both 4D-flow MRI and high-resolution BB-MRI were retrospectively included in this study. The haemodynamic parameters demonstrated using 4D-flow MRI were compared between different AWE patterns using the Kruskal-Wallis test and ordinal regression.

RESULTS

The results of Kruskal-Wallis test showed that the average wall shear stress in the IA (WSS_avg-IA), maximum through-plane velocity in the adjacent parent artery, inflow jet patterns and the average vorticity in IA (vorticity_avg-IA) were significantly associated with the AWE patterns. Ordinal regression analysis identified WSS_avg-IA (p=0.002) and vorticity_avg-IA (p=0.033) as independent predictors of AWE patterns.

CONCLUSION

A low WSS and low average vorticity were independently associated with a high AWE grade for IAs larger than 4 mm. Therefore, WSS and average vorticity could predict AWE and circumferential AWE.

Increased Wall Enhancement Extent Representing Higher Rupture Risk of Unruptured Intracranial Aneurysms

Objective

This study aims to investigate the relationship between aneurysm wall enhancement and clinical rupture risks based on the magnetic resonance vessel wall imaging (MR-VWI) quantitative methods.

Methods

One hundred and eight patients with 127 unruptured aneurysms were prospectively enrolled from Feburary 2016 to October 2017. Aneurysms were divided into high risk (≥10) and intermediate-low risk group (<10) according to the PHASES (Population, Hypertension, Age, Size of aneurysm, Earlier SAH history from another aneurysm, Site of aneurysm) scores. Clinical risk factors, aneurysm morphology, and wall enhancement index (WEI) calculated using 3D MR-VWI were analyzed and compared.

Results

In comparison of high-risk and intermediated-low risk groups, univariate analysis showed that neck width (4.5±3.3 mm vs. 3.4±1.7 mm, p=0.002), the presence of wall enhancement (100.0% vs. 62.9%, p<0.001), and WEI (1.6±0.6 vs. 0.8±0.8, p<0.001) were significantly associated with high rupture risk. Multivariate regression analysis revealed that WEI was the most important factor in predicting high rupture risk (odds ratio, 2.6; 95% confidence interval, 1.4–4.9; p=0.002). The receiver operating characteristic (ROC) curve analysis can efficiently differentiate higher risk aneurysms (area under the curve, 0.780; p<0.001) which have a reliable WEI cutoff value (1.04; sensitivity, 0.833; specificity, 0.67) predictive of high rupture risk.

Conclusion

Aneurysms with higher rupture risk based on PHASES score demonstrate increased neck width, wall enhancement, and the enhancement intensity. Higher WEI in unruptured aneurysms has a predictive value for increased rupture risk.

Peri-Aneurysmal Brain Edema in Native and Treated Aneurysms: The Role of Thrombosis

Cerebral peri-aneurysmal edema (PE) is typically associated with giant partially-thrombosed aneurysms and less frequently with smaller aneurysms treated with endovascular embolization. An understanding of the pathophysiologic mechanism of PE is still limited. We report 3 cases of cerebral aneurysms associated with PE. We describe 2 cases of giant partially thrombosed aneurysms surrounded by vasogenic edema with apposition of an intramural and juxtamural thrombus. Our third case is a smaller aneurysm inciting vasogenic edema several years after coil embolization. Vessel-wall magnetic resonance imaging (MRI) showed avid wall enhancement and an enhancing thrombus embedded within the coils, reflecting inflammation of the aneurysm wall and proliferation of the vasa vasorum. Thrombosis within the aneurysmal sac and walls, both in native and treated aneurysms, may promote inflammatory changes and sustain the occurrence of PE. Vessel-wall MRI has a potential role in the evaluation process of this subgroup of aneurysms.

C-Reactive Protein Levels Are Higher in Patients With Fusiform Intracranial Aneurysms: A Case-Control Study

BACKGROUND

Comprehending the risk factors that contribute to the formation of fusiform aneurysms (FAs) might provide some insight into treatment and prevention strategies. This case-control study aimed to compare the levels of serum C-reactive protein (CRP), as a biomarker, between patients with fusiform and saccular intracranial aneurysms.

METHODS

We retrospectively analyzed medical records from 2010 to 2019. Thirty-five patients were identified as having FAs: 13 (37.1%) were ruptured, and 22 were unruptured. An age-matched sample of 70 controls (2:1) with saccular aneurysms was obtained from the same records: 36 (51.4%) ruptured and 34 unruptured.

RESULTS

Patients with FAs had median CRP values of 0.61 mg/dL (IQR: 1.5), compared with 0.29 mg/dL (IQR: 0.42) in controls (P < 0.01). Within both the ruptured and the unruptured group, median CRP was higher in patients with FAs compared with controls (P < 0.01). Diabetes, smoking status, hypertension, and sex did not significantly influence CRP levels. Age-adjusted analyses showed that fusiform morphology was independently associated with higher CRP levels for unruptured aneurysms (OR 1.2, 95% CI 1.05-1.43), but not for ruptured aneurysms (OR 1.02, 95%CI 0.99-1.05).

CONCLUSIONS

CRP was higher in patients with FAs than controls, and it constituted an independent predictor of fusiform morphology for patients with unruptured aneurysms. Inflammation might be an especially important factor in FA formation and growth, and further studies could use this finding to design new treatment strategies.

Comparison of surgical and endovascular treatments for fusiform intracranial aneurysms: systematic review and individual patient data meta-analysis

Fusiform intracranial aneurysms (FIA) are associated with significant morbidity and mortality. We carried out a systematic review and meta-analysis of individual participant data with propensity score adjustment to compare the functional and angiographic outcomes between surgical and endovascular approaches to FIA. We conducted a systematic review for articles on the treatment of FIA with individual patient-level detailing. Data from patients treated for FIA in our institution from 2010 to 2018 were also collected. The primary studied outcome was morbidity, and secondary outcomes were angiographic results and retreatment. Propensity score-adjusted mixed-effects logistic regression models evaluated treatment options, stratified by anatomical location. Compiling original and published data, there were 312 cases, of which 79 (25.3%) had open surgery, and 233 (74.5%) were treated with endovascular procedures. There were no differences between treatment groups, for neither cavernous ICA (OR 1.04, 95% CI 0.05-23.6) nor supraclinoid aneurysms (OR 7.82, 95% CI 0.65-94.4). Both size (OR 1.11, 95% CI 1.03-1.19) and initial mRS (OR 2.0, 95% CI 1.2-3.3) were risk factors for morbidity, independent of location. Neither age nor rupture status influenced the odds of posterior morbidity. Unfavorable angiographic outcomes were more common in the endovascular group for supraclinoid and vertebrobasilar aneurysms (χ², P < 0.01). There were no differences between morbidity of surgical and endovascular treatments for FIA, regardless of aneurysm location. Size and initial mRS were correlated with functional outcomes, whereas age and rupture status were not. Microsurgery seems to yield better long-term angiographic results compared to endovascular procedures.

Shape irregularity of the intracranial aneurysm lumen exhibits diagnostic value

BACKGROUND

Morphological irregularity is linked to intracranial aneurysm wall instability and manifests in the lumen shape. Yet there is currently no consent on how to assess shape irregularity. The aims of this work are to quantify irregularity as perceived by clinicians, to break down irregularity into morphological attributes, and to relate these to clinically relevant factors such as rupture status, aneurysm location, and patient age or sex.

METHODS

Thirteen clinicians and 26 laypersons assessed 134 aneurysm lumen segmentations in terms of overall perceived irregularity and five different morphological attributes (presence/absence of a rough surface, blebs, lobules, asymmetry, complex geometry of the parent vasculature). We examined rater agreement and compared the ratings with clinical factors by means of regression analysis or binary classification.

RESULTS

Using rank-based aggregation, the irregularity ratings of clinicians and laypersons did not differ statistically. Perceived irregularity showed good agreement with curvature (coefficient of determination R² = 0.68 ± 0.08) and was modeled very accurately using the five morphological rating attributes plus shape elongation (R² = 0.95 ± 0.02). In agreement with previous studies, irregularity was associated with aneurysm rupture status (AUC = 0.81 ± 0.08); adding aneurysm location as an explanatory variable increased the AUC to 0.87 ± 0.09. Besides irregularity, perceived asymmetry, presence of blebs or lobules, aneurysm size, non-sphericity, and curvature were linked to rupture. No association was found between morphology and any of patient sex, age, and history of smoking or hypertension. Aneurysm size was linked to morphology.

CONCLUSIONS

Irregular lumen shape carries significant information on the aneurysm's disease status. Irregularity constitutes a continuous parameter that shows a strong association with the rupture status. To improve the objectivity of morphological assessment, we suggest examining shape through six different morphological attributes, which can characterize irregularity accurately.

Age-dependent characterization of carotid and cerebral artery geometries in a transgenic mouse model of sickle cell anemia using ultrasound and microcomputed tomography

To define morphological changes in carotid and cerebral arteries in sickle cell transgenic mice (SS) as they age, a combination of ultrasound and microcomputed tomography of plastinated arteries was used to quantify arterial dimensions and changes in mice 4, 12, and 24 weeks of age. 12-week SS mice had significantly larger common carotid artery diameters than AS mice, which continued through to the extracranial and intracranial portions of the internal carotid artery (ICA). There were also side specific differences in diameters between the left and right vessels. Significant ICA tapering along its length occurred by 12- and 24-weeks in SS mice, decreasing by as much as 70%. Significant narrowing along the length was also measured in SS anterior cerebral arteries at 12- and 24-weeks, but not AS. Collectively, these findings indicate that sickle cell anemia induces arterial remodeling in 12- and 24-weeks old mice. Catalog of measurements are also provided for the common carotid, internal carotid, anterior cerebral, and middle cerebral arteries for AS and SS genotypes, as a reference for other investigators using mathematical and computational models of age-dependent arterial complications caused by sickle cell anemia.

Interleukin Enhancer Binding Factor 2 Regulates Cell Viability and Apoptosis of Human Brain Vascular Smooth Muscle Cells

The proliferation and migration of vascular smooth muscle cells (VSMCs) are involved in the pathogenesis of intracranial aneurysm (IA) formation and rupture. Interleukin enhancer binding factor 2 (ILF2) is known as the nuclear factor of activated T cells and regulates cell growth. This study was aimed to explore the effects of ILF2 on IA progression. Human brain VSMCs (hBVSMCs) were transfected with pCDNA3.1(+), pCDNA3.1(+)-ILF2, siRNA-negative control, and siRNA-ILF2. The transfection efficiency was then evaluated by determining ILF2 expression. The cell viability and apoptosis were determined using Cell Counting Kit-8 and Annexin V-FITC cell apoptosis assay kit, respectively. Real-time quantification PCR (RT-qPCR) was applied to measure the expression levels of apoptosis-related and inflammation-related genes. Finally, western blot was used to detect the expression level of Fas cell surface death receptor 95 (CD95) and Caspase 8. Overexpression of ILF2 could significantly increase cell viability and decrease cell apoptosis (P < 0.05), while knock-down of ILF2 showed opposite trends for hBVSMCs on cell viability and apoptosis (P < 0.05). RT-qPCR results showed that ILF2 knock-down downregulated the expression levels of BCL2 apoptosis regulator (BCL2), transcriptional regulator Myc-like (c-Myc), and caspase 1 (ICE) whereas upregulated the expression levels of CD95, p21, p53, and interleukin-13 (IL-13). Additionally, the protein expression levels of CD95 and Caspase 8 were significantly decreased after ILF2 overexpression while were significantly increased after ILF2 knock-down (P < 0.05). ILF2 knock-down may inhibit cell viability and promote cell apoptosis of hBVSMCs by regulating the expression levels of apoptosis-related genes and suppressing inflammatory response.

Label-free multiphoton microscopy as a tool to investigate alterations of cerebral aneurysms

Cerebral aneurysms are abnormal focal dilatations of arterial vessel walls with pathological vessel structure alterations. Sudden rupture can lead to a subarachnoid hemorrhage, which is associated with a high mortality. Therefore, the origin of cerebral aneurysms as well as the progression to the point of rupture needs to be further investigated. Label-free multimodal multiphoton microscopy (MPM) was performed on resected human aneurysm domes and integrated three modalities: coherent anti-Stokes Raman scattering, endogenous two-photon fluorescence and second harmonic generation. We showed that MPM is a completely label-free and real-time powerful tool to detect pathognomonic histopathological changes in aneurysms, e.g. thickening and thinning of vessel walls, intimal hyperplasia, intra-wall haemorrhage, calcification as well as atherosclerotic changes. In particular, the loss or fragmentation of elastin as well as fibromatous wall remodelling appeared very distinct. Remarkably, cholesterol and lipid deposits were clearly visible in the multiphoton images. MPM provides morphological and biochemical information that are crucial for understanding the mechanisms of aneurysm formation and progression.

Metformin inhibits intracranial aneurysm formation and progression by regulating vascular smooth muscle cell phenotype switching via the AMPK/ACC pathway

Background

The regulation of vascular smooth muscle cell (VSMC) phenotype plays an important role in intracranial aneurysm (IA) formation and progression. However, the underlying mechanism remains unclear. Metformin is a 5′ AMP-activated protein kinase (AMPK) agonist that has a protective effect on vasculature. The present study investigated whether metformin modulates VSMC phenotype switching via the AMPK/acetyl-CoA carboxylase (ACC) pathway during IA pathogenesis.

Methods

Adult male Sprague-Dawley rats (n = 80) were used to establish an elastase-induced IA model. The effects of metformin on AMPK activation and VSMC phenotype modulation were examined. We also established a platelet-derived growth factor (PDGF)-BB-induced VSMC model and analyzed changes in phenotype including proliferation, migration, and apoptosis as well as AMPK/ACC axis activation under different doses of metformin, AMPK antagonist, ACC antagonist, and their combinations.

Results

Metformin decreased the incidence and rupture rate of IA in the rat model and induced a switch in VSMC phenotype from contractile to synthetic through activation of the AMPK/ACC pathway, as evidenced by upregulation of VSMC-specific genes and decreased levels of pro-inflammatory cytokines. AMPK/ACC axis activation inhibited the proliferation, migration, and apoptosis of VSMCs, in which phenotypic switching was induced by PDGF-BB.

Conclusions

Metformin protects against IA formation and rupture by inhibiting VSMC phenotype switching and proliferation, migration, and apoptosis. Thus, metformin has therapeutic potential for the prevention of IA.

Practical value of three-dimensional high resolution magnetic resonance Vessel Wall imaging in identifying suspicious intracranial vertebrobasilar dissecting aneurysms

Background

Direct evidence of intimal flaps, double lumen and intramural haematomas (IMH) is difficult to detect on conventional angiography in most intracranial vertebrobasilar dissecting aneurysms (VBDAs). Our purpose was to assess the value of three-dimensional high-resolution magnetic resonance vessel wall imaging (3D HRMR VWI) for identifying VBDAs.

Methods

Between August 2013 and January 2016, consecutive patients with suspicious VBDAs were prospectively enrolled to undergo catheter angiography and VWI (pre- and post-contrast). The lesion was diagnosed as definite VBDA when presenting direct signs of dissection; as possible when only presenting indirect signs; and as segmental ectasia when there was local dilation and wall thickness similar to adjacent normal artery’s without mural thrombosis.

Results

Twenty-one patients with 27 lesions suspicious for VBDAs were finally included. Based on findings of VWI and catheter angiography, definite VBDA was diagnosed in 25 and 7 lesions (92.6%, vs 25.9%, p <  0.001), respectively; possible VBDA in 0 and 20 (0 vs 74.1%), respectively; and segmental ectasia in 2 and 0 (7.4% vs 0%), respectively. On VWI and catheter angiography, intimal flap was detected in 21 and 7 lesions (77.8% vs 25.9%, p = 0.001), respectively; double lumen sign in 18 and 7 (66.7% vs 25.9%, p = 0.003), respectively; and IMH sign in 14 and 0 (51.9% vs 0), respectively.

Conclusions

3D HRMR VWI could detect direct dissection signs more frequently than catheter angiography. This may help obtain definite diagnosis of intracranial VBDAs, and allow accurate differentiation between dissecting aneurysm and segmental ectasia as well. Further prospective study with larger sample was required to investigate the superiority of HRMR VWI for definite diagnosis of intracranial VBDAs than catheter angiography.

Comparison of Aneurysm Patency and Mural Inflammation in an Arterial Rabbit Sidewall and Bifurcation Aneurysm Model under Consideration of Different Wall Conditions

Background: Biological processes that lead to aneurysm formation, growth and rupture are insufficiently understood. Vessel wall inflammation and degeneration are suggested to be the driving factors. In this study, we aimed to investigate the natural course of vital (non-decellularized) and decellularized aneurysms in a rabbit sidewall and bifurcation model. Methods: Arterial pouches were sutured end-to-side on the carotid artery of New Zealand White rabbits (vital [n = 6] or decellularized [n = 6]), and into an end-to-side common carotid artery bifurcation (vital [n = 6] and decellularized [n = 6]). Patency was confirmed by fluorescence angiography. After 28 days, all animals underwent magnetic resonance and fluorescence angiography followed by aneurysm harvesting for macroscopic and histological evaluation. Results: None of the aneurysms ruptured during follow-up. All sidewall aneurysms thrombosed with histological inferior thrombus organization observed in decellularized compared to vital aneurysms. In the bifurcation model, half of all decellularized aneurysms thrombosed whereas the non-decellularized aneurysms remained patent with relevant increase in size compared to baseline. Conclusions: Poor thrombus organization in decellularized sidewall aneurysms confirmed the important role of mural cells in aneurysm healing after thrombus formation. Several factors such as restriction by neck tissue, small dimensions and hemodynamics may have prevented aneurysm growth despite pronounced inflammation in decellularized aneurysms. In the bifurcation model, rarefication of mural cells did not increase the risk of aneurysm growth but tendency to spontaneous thrombosis.

Hemodynamics of Cerebral Aneurysms: Connecting Medical Imaging and Biomechanical Analysis

In the last two decades, numerous studies have conducted patient-specific computations of blood flow dynamics in cerebral aneurysms and reported correlations between various hemodynamic metrics and aneurysmal disease progression or treatment outcomes. Nevertheless, intra-aneurysmal flow analysis has not been adopted in current clinical practice, and hemodynamic factors usually are not considered in clinical decision making. This review presents the state of the art in cerebral aneurysm imaging and image-based modeling, discussing the advantages and limitations of each approach and focusing on the translational value of hemodynamic analysis. Combining imaging and modeling data obtained from different flow modalities can improve the accuracy and fidelity of resulting velocity fields and flow-derived factors that are thought to affect aneurysmal disease progression. It is expected that predictive models utilizing hemodynamic factors in combination with patient medical history and morphological data will outperform current risk scores and treatment guidelines. Possible future directions include novel approaches enabling data assimilation and multimodality analysis of cerebral aneurysm hemodynamics.

Decreased contrast enhancement on high-resolution vessel wall imaging of unruptured intracranial aneurysms in patients taking aspirin

OBJECTIVE

Inflammation plays an integral role in the formation, growth, and progression to rupture of unruptured intracranial aneurysms (UIAs). Animal and human studies have suggested that, due to its antiinflammatory effect, aspirin (ASA) may decrease the risks of growth and rupture of UIAs. High-resolution vessel wall imaging (HR-VWI) has emerged as a noninvasive method to assess vessel wall inflammation and UIA instability. To the authors' knowledge, to date no studies have found a significant correlation between patient use of ASA and contrast enhancement of UIAs on HR-VWI.

METHODS

The University of Iowa HR-VWI Project database was analyzed. This database is a compilation of data on patients with UIAs who prospectively underwent HR-VWI on a 3T Siemens MRI scanner. The presence of aneurysmal wall enhancement was objectively defined using the aneurysm-to-pituitary stalk contrast ratio (CRstalk). This ratio was calculated by measuring the maximal signal intensity in the aneurysmal wall and the pituitary stalk on postcontrast T1-weighted images. Data on aneurysm size, morphology, and location and patient demographics and comorbidities were collected. Use of ASA was defined as daily intake of ≥ 81 mg during the previous 6 months or longer. Univariate and multivariate logistic regression analyses were performed to determine factors independently associated with increased contrast enhancement of UIAs on HR-VWI.

RESULTS

In total, 74 patients harboring 96 UIAs were included in the study. The mean patient age was 64.7 ± 12.4 years, and 60 patients (81%) were women. Multivariate analysis showed that age (OR 1.12, 95% CI 1.05-1.19), aneurysm size ≥ 7 mm (OR 21.3, 95% CI 4.88-92.8), and location in the anterior communicating, posterior communicating, and basilar arteries (OR 10.7, 95% CI 2.45-46.5) were significantly associated with increased wall enhancement on HR-VWI. On the other hand, use of ASA was significantly associated with decreased aneurysmal wall enhancement on HR-VWI (OR 0.22, 95% CI 0.06-0.83, p = 0.026).

CONCLUSIONS

The study results establish a correlation between use of ASA daily for ≥ 6 months and significant decreases in wall enhancement of UIAs on HR-VWI. The findings also demonstrate that detection of wall enhancement using HR-MRI may be a valuable noninvasive method for assessing aneurysmal wall inflammation and UIA instability.

Gadolinium Enhancement of the Aneurysm Wall in Extracranial Carotid Artery Aneurysms

BACKGROUND AND PURPOSE

The natural history and optimal treatment of extracranial carotid artery aneurysms are unknown. Gadolinium enhancement of the aneurysm wall may reflect aneurysm wall inflammation and instability. In this study, we investigated the feasibility of extracranial carotid artery aneurysm wall imaging and explored a potential relationship of aneurysm wall enhancement with aneurysm growth and the presence of (silent) brain infarcts and white matter lesions.

MATERIALS AND METHODS

Fourteen conservatively treated patients with 15 asymptomatic extracranial carotid artery aneurysms underwent gadolinium-enhanced 3T MR imaging at 2 time points with a 12-month interval. Primary outcome was growth of the aneurysm sac (≥2.0 mm); secondary outcomes were the presence of (silent) brain infarcts and white matter lesions at baseline and follow-up. MR images were reviewed by 2 independent observers, and inter- and intraobserver reproducibility was assessed.

RESULTS

Seven (50%) patients were men; the median age was 55 years (range, 40-69 years). Eleven extracranial carotid artery aneurysms (73%) were saccular (median size, 11 mm; range, 5.0-38.5 mm), and 4 were fusiform (median size, 21.5 mm; range, 10.0-40.0 mm). Eleven of 15 aneurysms (73%) exhibited gadolinium enhancement at baseline. Four aneurysms (27%) showed growth at follow-up imaging, 2 gadolinium-positive (+) and 2 gadolinium-negative (-) (P = .245). Three patients (21%) had ipsilateral brain infarcts at baseline; 1 of them showed a new silent brain infarct at follow-up imaging (gadolinium+). Nine patients (64%) showed bilateral white matter lesions at baseline. In 3 patients, increased white matter lesion severity was observed at follow-up (2 gadolinium+). All observations showed excellent inter- and intraobserver reproducibility.

CONCLUSIONS

In this explorative study, we demonstrated that extracranial carotid artery aneurysm wall imaging was feasible. Future well-powered studies are needed to investigate whether extracranial carotid artery aneurysm gadolinium enhancement predicts aneurysm growth and thromboembolic complications.