Intracranial Saccular Aneurysms Research Articles

Complication and prognosis factor analysis of stent-assisted coil embolization for ruptured wide-necked saccular intracranial aneurysms

Objective To investigate the factors influencing the complications and prognosis of stent-assisted coil embolization (SACE) for ruptured wide-necked saccular intracranial aneurysms. Methods A retrospective analysis was conducted about the clinical data of 147 patients with ruptured wide-necked saccular intracranial aneurysms who underwent SACE from March 2008 to December 2015 at Department of Neurosurgery, Nanjing General Hospital of Nanjing Military Command. The modified Rankin Scale (mRS) was used to assess the patients’ outcomes. Univariate and multivariate Logistic regression were utilized to identify the factors influencing the related complications and prognosis. Results Surgery-related complications occurred in 26 patients (17.7%) out of 147 cases. The location (P=0.002) and size (P=0.028) of intracranial aneurysms might be risk factors of the complications. Among all patients, 125(85.0%) achieved good clinical outcome. The univariate analysis revealed that the patient's age over 65 (P=0.041) and relatively high Hunt-Hess grade at admission (P<0.001) might be associated with high mRS at the time of discharge. The analysis using multivariate Logistic regression demonstrated that the Hunt-Hess grade (OR, 28.790, 95% CI 8.091-102.446, P<0.001) and aneurysm size (OR, 0.149, 95% CI 0.030-0.734, P=0.019) were independent factors influencing the patient's mRS at the time of discharge, while the short-term outcome was only associated with the Hunt-Hess grade(P<0.001). Conclusions The treatment of SACE seems to be a safe and effective procedure for ruptured wide-necked saccular intracranial aneurysms. Middle cerebral artery aneurysms and large aneurysms might be the risk factors of surgical complications. The patient's age over 65, high Hunt-Hess grade on admission and large size of aneurysm could be associated with poor outcome at the time of discharge assessed by mRS. High Hunt-Hess grade might be a significant factor influencing the patient's short-term prognosis. Key words: Intracranial aneurysm; Embolization, therapeutic; Stents; Postoperative complications; Prognosis

Risk factors for the recurrence of an intracranial saccular aneurysm following endovascular treatment.

BackgroundThis study was aimed to determine risk factors for the recurrence of an intracranial saccular aneurysm (ISA) following endovascular treatment. The findings will help medical professionals to identify patients having a high risk of ISA recurrence and assist them in developing appropriate follow-up plans.ResultsDuring the follow-up period, 12.6% of the patients (83/658) experienced recurrent ISAs. An analysis of related factors, including gender, age, hypertension, diabetes mellitus, smoking, tumor size, width of the aneurysm neck, the presence or absence of a rupture, the volume embolization ratio (VER), the application or nonapplication of a stent, and follow-up time, revealed that a tumor size > 10 mm in diameter, wide-necked aneurysms, an anterior communicating or middle cerebral artery aneurysm, an aneurysm rupture, a VER < 20%, the absence of stent assistance, and follow-up time were high-risk factors for the recurrence of ISAs.Materials and MethodsWe retrospectively reviewed the records of 658 patients who underwent endovascular treatment for ISAs from January 2010 through December 2014. Multivariable logistic regression was performed on the candidates’ risk factors, which were identified via univariable screening analysis.ConclusionsSmoking, a large tumor size, a wide-necked aneurysm, an anterior communicating or middle cerebral artery aneurysm, an aneurysm rupture, a VER < 20%, and an absence of stent assistance are significant risk factors for the postoperative recurrence of an aneurysm. Strict follow-up plans should be created for ISA patients having these high-risk factors.

Endovascular treatment of ruptured tiny (⩽3 mm) intracranial aneurysms in the setting of subarachnoid hemorrhage: A case series of 20 patients and literature review

Successful endovascular coiling of ruptured tiny saccular intracranial aneurysms (⩽3mm) is technically challenging and traditionally has been associated with technical failures, as well as morbidity related to thromboembolic events and high intraoperative rupture rates. This study analyzes the feasibility, technical efficacy, and clinical outcomes of coil embolization of ruptured tiny intracranial aneurysms using current coil and microcatheter technology and techniques. We performed a retrospective review of 20 patients with 20 ruptured tiny aneurysms treated with endovascular coil embolization from 2013 to 2016 at a single high-volume academic tertiary care practice. The mean aneurysm size was 2.4mm (median 2.5mm, 1–3). Complete occlusion was achieved in 12 of 20 patients (60%), the remaining 7 of 20 patients (35%) had a small neck remnant, and there was 1 failure (5%) converted to microsurgical clipping. Two patients had a failed attempted surgical clip reconstruction and were subsequently coiled. There was 1 intraprocedural rupture (5%) and 1 severe parent artery vasospasm (5%) during coiling. At discharge, 60% of patients were living independently. At follow-up three patients were deceased. Mean angiographic follow-up was 139days (SD 120). There were no aneurysm recurrences among occluded patients and there were no retreatments among those with neck remnants. Coiling of ruptured aneurysms ⩽3mm is feasible with high occlusion rates and low complication rates. The availability of softer coils with flexible detachment zones has led to safe and effective endovascular treatment of tiny ruptured aneurysms.

Microguidewire Looping to Traverse Stented Parent Arteries of Intracranial Aneurysms.

ObjectiveStents are widely used in coil embolization of intracranial aneurysms, but on occasion, a microcatheter must traverse a stented segment of artery (so-called trans-cell technique) to select an aneurysm, or double stenting may necessary. In such situations, microguidewire passage and microcatheter delivery through a tortuous stented parent artery may pose a technical challenge. Described herein is a microguidewire looping technique to facilitate endovascular navigation in these circumstances.MethodsTo apply this technique, the microguidewire tip is looped before entering the stented parent artery and then advanced distally past the stented segment, with the loop intact. Rounding of the tip prevents interference from stent struts during passage. A microcatheter is subsequently passed into the stented artery for positioning near the neck of aneurysm, with microguidewire assistance. The aneurysm is then selected, steering the microcatheter tip (via inner microguidewire) into the dome.ResultsThis technique proved successful during coil embolization of nine saccular intracranial aneurysms (internal carotid artery [ICA], 6; middle cerebral artery, 2; basilar tip, 1), performing eight trans-cell deliveries and one additional stenting. Selective endovascular embolization was enabled in all patients, resulting in excellent clinical and radiologic outcomes, with no morbidity or mortality directly attributable to microguidewire looping.ConclusionMicroguidewire looping is a reasonable alternative if passage through a stented artery is not feasible by traditional means, especially at paraclinoid ICA sites.

Leo stent for endovascular treatment of intracranial aneurysms: very long-term results in 50 patients with 52 aneurysms and literature review.

The Leo stent was the first retrievable stent for endovascular treatment of intracranial aneurysms (IAs). We report our experience with this device with emphasis on very long-term follow-up. This study was approved by authors' ethical committee. A retrospective review of our prospectively maintained database identified all patients treated for a saccular IA with this stent in our institution. Technical issues and immediate and long-term outcomes (at least 12months) were evaluated. Between 2004 and 2015, 50 patients with 52 IAs were identified. In two patients, the stent could not safely be placed (failure rate=3.8%). Among 48 treated patients with 50 IAs, there were 44 women and 4 men (mean age, 53years). Mean aneurysm diameter was 7.2mm. All IAs but six were wide-necked. There was no immediate morbidity or mortality. Anatomical results included 76% complete occlusions, 22% neck remnants, and 2% incomplete occlusions. Mean follow-up was 50.2months (range, 12-139months). Two patients had delayed TIAs but long-term morbidity rate remained = 0%. At follow-up, occlusion was stable in 68% IAs, showed thrombosis in 12%, and recanalization in 20% IAs. Complementary treatment was required in 8% IAs. Final results showed 70% complete occlusions, 24% neck remnants, and 6% incomplete occlusions. Asymptomatic stent occlusion and significant stenosis occurred in one and two cases, respectively. The Leo stent is safe and effective for treatment of wide-necked saccular IAs. Very long-term results show high rates of adequate and stable occlusion. Moreover, the stent is well tolerated.

Abstract WP86: Early Detection of Aneurysm Growth by Volume and Surface Area Analysis Using 3D Modeling From CT Angiography

Introduction: Enlargement of unruptured aneurysms indicates an increased risk of rupture. Assessment of aneurysm growth is typically based on aneurysm max diameter. However, this method is often unreliable due to factors such as the degree of contrast enhancement, tilting among studies and artifacts. Hypothesis: Three-dimensional modeling can help to judge aneurysm growth. Methods: All aneurysm patients who underwent CTA (1.0-mm slice thickness) with at least one follow-up in 2015, were reviewed. Intracranial saccular aneurysms were selected and fusiform, dissecting and mycotic aneurysms were excluded. Growth was defined as more than a 0.5 mm increase in size compared with the first study. 3D models were created from the source data using 3D-slicer (http://www.slicer.org). Aneurysm extraction from the parent artery was performed semi-automatically and volume and surface area were calculated using vascular toolkit (http://www.vmtk.org). The Mann-Whitney test and ROC curve analysis were applied to compare cases which increased in size with no-change cases. Results: This research included 59 aneurysms in 51 patients that underwent 250 CTA, with follow-up duration of 50.0 ± 50.5 months. Nine aneurysms increased in size. In 5 of 9 cases, follow-up studies prior to growth detection were available. In these cases, maximum diameter change from the first study was not significant (P = 0.169). By contrast, volume and area were significantly different (P = 0.046 and 0.046, respectively). On ROC analysis, AUCs of maximum diameter, volume, and area changes were 0.7, 0.772 and 0.772. Conclusions: Calculating volume and area changes was useful to judge aneurysm growth earlier than size measurement.

Abstract WP87: Related Factors to Growth of Intracranial Aneurysm: Time Course Analysis

Introduction: Intracranial aneurysms, especially small and asymptomatic ones, are often monitored with imaging studies. However, the prognosis of aneurysms varies according to many factors, which is reflected in variation in growth. Hypothesis: A time course analysis with a long follow up period can reveal characteristics of aneurysm growth and factors related to growth. Methods: All patients who underwent two CTA, including one in 2015, were reviewed. Intracranial saccular aneurysms were selected and fusiform, dissecting and mycotic aneurysms were excluded. Aneurysm characteristics, patient information, and medical history were recorded. Growth was defined as more than a 0.5 mm size increase compared with the first study. Log-rank and Cox regression tests were applied to identify factors related growth. Results: This study included 119 aneurysms of 91 patients that underwent a total of 474 CTA, with initial size 0.0-17.0 mm and follow-up duration of 42.9 ± 44.8 months. Eighteen aneurysms increased in size. Follow-up period to growth was 25.4 ± 20.8 months. Growth rate was highly variable (0.74 ± 3.23 mm/year). On univariate log-rank or Cox regression test, only history of transient ischemic attack (TIA) (P = 0.016) showed significance for aneurysm growth. On multivariate Cox regression test, history of TIA (P = 0.010, hazard ratio = 7.939), the maximum diameter at the first CTA (P = 0.026, hazard ratio = 1.216) and history of cancer (P = 0.028, hazard ratio = 4.499). Cancers existed in breast, thyroid, and lung. Conclusions: Aneurysm growth rate can vary even in the same patient. Aneurysm growth frequency varied according to size and risk factors. History of cancer has not previously been associated with aneurysm growth and may benefit from further study.

Abstract WP89: Preliminary Single-center Experience with Neuroform Atlas Stent-assisted Coiling for Unruptured Intracranial Aneurysms

Background and Purpose: Expandable stents have broadened the spectrum of endovascular treatment of intracranial aneurysms. The Neuroform ATLAS, a nitinol self-expanding, hybrid/open-cell stent, is the evolution of the Neuroform EZ supposing to ease the navigability of the system into intra-cranial arteries, through a low-profile 0.017 inch delivery catheter. We present herein our initial experience in the treatment of intracranial aneurysms with this stent. Materials and Method: We compiled data from consecutive patients of our institution from July 2015 to June 2016 who underwent stent-assisted coiling with the Neuroform ATLAS. Clinical and angiographic results were analyzed retrospectively. Results: Thirty-six intracranial saccular aneurysms (18 MCA, 10 AcoA, 4 ICA bifurcation, 2 basilar tip, 1 vertebral-PICA, 1 pericallosal artery) in 35 patients (24 women, 11 men, mean age 60 years) were consecutively treated. The stent was used in 32 previously untreated aneurysms, and in 4 cases of recanalization. One single stent was used in 15 aneurysms while 21 aneurysms (58.3%) were treated with 2 stents in a “Y” configuration. The immediate post-treatment angiography showed a complete occlusion in 19 cases (52.7%), a residual neck in 4 cases (11.1%) and a residual aneurysmal contrast filling in 13 cases (36.1%). Two complications occurred (5.5%), the first due to an associated aneurysm perforation (mRs 1), and the second due to parent vessel perforation (mRs 6). Both of them occurred after the stent implantation. We don’t report any case of attempted stenting treatment. Conclusion: The Neuroform ATLAS Delivery System is an effective device for treatment of complex intracranial aneurysms, allowing good conformability and stability with a high level of navigability. The 2 main advantages are its low profile and the cell-design allowing easy mesh crossing to perform Y-stenting procedures. Key words: Neuroform ATLAS, Neuroform EZ, Stent-assisted coiling, cerebral aneurysm. Abbreviations: mRs: modified Rankin Scale, AcoA: Anterior communicating artery, PICA: posterior inferior cerebellar artery.

Procedure-related Complications during Endovascular Treatment of Intracranial Saccular Aneurysms.

ObjectiveWe evaluate the rates and outcomes of major procedure-related complications during coiling.Materials and MethodsBetween 2007 and 2015, 436 intracranial saccular aneurysms were treated. Complications are categorized as three types: intraprocedural aneurysm rupture (IAR), thromboembolism (TE), and post-procedural early rebleeding (PER). And we evaluated the risk factors of procedure related complications by multivariate analysis.ResultsComplications occurred in 61 aneurysms (14%). The overall incidence of complications in subarachnoid hemorrhage (SAH) was significantly higher than in unruptured intracranial aneurysm (UIA) (20% vs. 6%). The incidence of IAR and TE were higher in SAH than in UIA (IAR 12% vs. 4%, TE 7% vs. 3%, p < 0.05). Five PER occurred only in SAH. In 34 UIA which were treated with balloon-assisted coiling (BAC), all these patients had good recovery despite 3 patients had the IAR. The incidence of IAR and TE were not different between BAC and non-BAC groups (p > 0.05). All 7 patients who had IAR during BAC had good recovery. In multiple logistic regression analysis, female gender, SAH, and intraventricular hemorrhage were associated with procedure related complication (p < 0.05).ConclusionEndovascular coil embolization is a minimally invasive procedure, but incidence of its complication is not low, especially in SAH. BAC can be a good tool to avoid poor outcome from unexpected IAR during coiling. While IA tirofiban injection is a useful therapy in TE during coiling, sometimes we are aware of the risk of the early rebleeding in SAH patients.

Unruptured intracranial aneurysms: development, rupture and preventive management.

Saccular unruptured intracranial aneurysms (UIAs) have a prevalence of 3% in the adult population, and are being increasingly detected because of improved quality and higher frequency of cranial imaging. Large amounts of data, providing varying levels of evidence, have been published on aneurysm development, progression and rupture, but less information is available on the risks and efficacy of preventive treatment. When deciding how to best manage UIAs, clinicians must consider the age and life expectancy of the patient, the estimated risk of rupture, the risk of complications attributed to preventive treatment, and the level of anxiety caused by the awareness of having an aneurysm. This Review highlights the latest human data on the formation, progression and rupture of intracranial aneurysms, as well as risks associated with preventive treatment. Considering these we discuss the implication for clinical management. Furthermore, we highlight pivotal questions arising from current data on intracranial aneurysms and the implications the data have for future experimental or clinical research. We also discuss data on novel radiological surrogates for rupture for those aneurysms that do not require preventive occlusion. Finally, we provide guidance for clinicians who are confronted with patients with incidentally detected UIAs.

Identification of a Long Noncoding RNA-Associated Competing Endogenous RNA Network in Intracranial Aneurysm

Intracranial aneurysm (IA) is a cerebrovascular disorder characterized by an abnormally bulged artery in the brain and subarachnoid hemorrhage caused by IA rupture with a high ratio of fatality and morbidity. However, the genetic cause of IA remains largely unknown. A dysregulated long noncoding RNA (lncRNA) -associated competing endogenous RNA (ceRNA) network was constructed by using sample-matched microRNA (miRNA), lncRNA, and messenger (mRNA) expression profiles in 12 saccular IA samples and paired control arteries. In this study, 1150 lncRNAs, 2545 mRNAs, and 286 miRNAs were differentially expressed in IAs compared with control arteries. Using miRanda, a ceRNA score was assigned, and gene expression methods were used to construct a ceRNA network. The network consists of 8401 miRNA-lncRNA-mRNA interactions (199 miRNAs, 445 lncRNAs, 1116 mRNAs; P < 0.05). Further Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis indicated that the mRNAs involved in the ceRNA network were involved in the regulation of muscle contraction and vascular smooth muscle contraction. By comparing IAs and their control arteries, we identified differentially expressed lncRNAs, miRNAs, and mRNAs and suggested ceRNA roles in the pathogenesis of IA. These findings may help to characterize the pathogenesis of IA and provide novel therapeutic targets in the future for patients with IA.

Flow Conditions in the Intracranial Aneurysm Lumen Are Associated with Inflammation and Degenerative Changes of the Aneurysm Wall.

Saccular intracranial aneurysm is a common disease that may cause devastating intracranial hemorrhage. Hemodynamics, wall remodeling, and wall inflammation have been associated with saccular intracranial aneurysm rupture. We investigated how saccular intracranial aneurysm hemodynamics is associated with wall remodeling and inflammation of the saccular intracranial aneurysm wall. Tissue samples resected during a saccular intracranial aneurysm operation (11 unruptured, 9 ruptured) were studied with histology and immunohistochemistry. Patient-specific computational models of hemodynamics were created from preoperative CT angiographies. More stable and less complex flows were associated with thick, hyperplastic saccular intracranial aneurysm walls, while slower flows with more diffuse inflow were associated with degenerated and decellularized saccular intracranial aneurysm walls. Wall degeneration (P = .041) and rupture were associated with increased inflammation (CD45+, P = .031). High wall shear stress (P = .018), higher vorticity (P = .046), higher viscous dissipation (P = .046), and high shear rate (P = .046) were associated with increased inflammation. Inflammation was also associated with lack of an intact endothelium (P = .034) and the presence of organized luminal thrombosis (P = .018), though overall organized thrombosis was associated with low minimum wall shear stress (P = .034) and not with the flow conditions associated with inflammation. Flow conditions in the saccular intracranial aneurysm are associated with wall remodeling. Inflammation, which is associated with degenerative wall remodeling and rupture, is related to high flow activity, including elevated wall shear stress. Endothelial injury may be a mechanism by which flow induces inflammation in the saccular intracranial aneurysm wall. Hemodynamic simulations might prove useful in identifying saccular intracranial aneurysms at risk of developing inflammation, a potential biomarker for rupture.

Risk of Shunting After Aneurysmal Subarachnoid Hemorrhage: A Collaborative Study and Initiation of a Consortium.

Shunt dependent hydrocephalus after aneurysmal subarachnoid hemorrhage (aSAH) is a common sequela that may lead to poor neurological outcome and predisposes to various interventions, admissions, and complications. We reviewed post-aSAH shunt dependency in a population-based sample and tested the feasibility of a clinical risk score to identify subgroups of aSAH patients with increasing risk of shunting for hydrocephalus. A total of 1533 aSAH patients from the population-based Eastern Finland Saccular Intracranial Aneurysm Database (Kuopio, Finland) were used in a recursive partitioning analysis to identify risk factors for shunting after aSAH. The risk model was built and internally validated in random split cohorts. External validation was conducted on 946 aSAH patients from the Southwestern Tertiary Aneurysm Registry (Dallas, TX) and tested using receiver-operating characteristic curves. Of all patients alive ≥14 days, 17.7% required permanent cerebrospinal fluid diversion. The recursive partitioning analysis defined 6 groups with successively increased risk for shunting. These groups also successively risk stratified functional outcome at 12 months, shunt complications, and time-to-shunt rates. The area under the curve-receiver-operating characteristic curve for the exploratory sample and internal validation sample was 0.82 and 0.78, respectively, with an external validation of 0.68. Shunt dependency after aSAH is associated with higher morbidity and mortality, and prediction modeling of shunt dependency is feasible with clinically useful yields. It is important to identify and understand the factors that increase risk for shunting and to eliminate or mitigate the reversible factors. The aSAH-PARAS Consortium (Aneurysmal Subarachnoid Hemorrhage Patients' Risk Assessment for Shunting) has been initiated to pool the collective insights and resources to address key questions in post-aSAH shunt dependency to inform future aSAH treatment guidelines.

Antidepressant Use After Aneurysmal Subarachnoid Hemorrhage: A Population-Based Case-Control Study.

To elucidate the predictors of antidepressant use after subarachnoid hemorrhage from saccular intracranial aneurysm (sIA-SAH) in a population-based cohort with matched controls. The Kuopio sIA database includes all unruptured and ruptured sIA cases admitted to the Kuopio University Hospital from its defined catchment population in Eastern Finland, with 3 matched controls for each patient. The use of all prescribed medicines has been fused from the Finnish national registry of prescribed medicines. In the present study, 2 or more purchases of antidepressant medication indicated antidepressant use. The risk factors of the antidepressant use were analyzed in 940 patients alive 12 months after sIA-SAH, and the classification tree analysis was used to create a predicting model for antidepressant use after sIA-SAH. The 940 12-month survivors of sIA-SAH had significantly more antidepressant use (odds ratio, 2.6; 95% confidence interval, 2.2-3.1) than their 2676 matched controls (29% versus 14%). Classification tree analysis, based on independent risk factors, was used for the best prediction model of antidepressant use after sIA-SAH. Modified Rankin Scale until 12 months was the most potent predictor, followed by condition (Hunt and Hess Scale) and age on admission for sIA-SAH. The sIA-SAH survivors use significantly more often antidepressants, indicative of depression, than their matched population controls. Even with a seemingly good recovery (modified Rankin Scale score, 0) at 12 months after sIA-SAH, there is a significant risk of depression requiring antidepressant medication.

Wall enhancement on high-resolution magnetic resonance imaging may predict an unsteady state of an intracranial saccular aneurysm.

The aneurysm wall has been reported to play a critical role in the formation, development, and even rupture of an aneurysm. We used high-resolution magnetic resonance imaging (HRMRI) to investigate the aneurysm wall in an effort to identify evidence of inflammation invasion and define its relationship with aneurysm behavior. Patients with intracranial aneurysms who were prospectively evaluated using HRMRI between July 2013 and June 2014 were enrolled in this study. The aneurysm's wall enhancement and evidence of inflammation invasion were determined. In addition, the relationship between aneurysm wall enhancement and aneurysm size and symptoms, including ruptured aneurysms, giant unruputred intracranial aneurysms (UIAs) presenting as mass effect, progressively growing aneurysms, and aneurysms associated with neurological symptoms, was statistically analyzed. Twenty-five patients with 30 aneurysms were available for the current study. Fourteen aneurysms showed wall enhancement, including 6 ruptured and 8 unruptured aneurysms. Evidence of inflammation was identified directly through histological studies and indirectly through intraoperative investigations and clinical courses. The statistical analysis indicated no significant correlation between aneurysm wall enhancement and aneurysm size. However, there was a strong correlation between wall enhancement and aneurysm symptoms, with a kappa value of 0.86 (95% CI 0.68-1). Aneurysm wall enhancement on HRMRI might be a sign of inflammatory change. Symptomatic aneurysms exhibited wall enhancement on HRMRI. Wall enhancement had a high consistent correlation of symptomatic aneurysms. Therefore, wall enhancement on HRMRI might predict an unsteady state of an intracranial saccular aneurysm.

Relationship between aneurysm wall enhancement and conventional risk factors in patients with unruptured intracranial aneurysms: A black-blood MRI study.

Aneurysmal wall enhancement (AWE) has emerged as a new possible biomarker for depicting inflammation of the intracranial aneurysm (IA). However, the relationships of AWE with other risk factors are still unclear for unruptured IA. The purpose of this study was to investigate the association between AWE and other risk metrics. Forty-eight patients with unruptured saccular IAs diagnosed by digital subtraction angiography were recruited to undergo magnetic resonance (MR) black-blood imaging. AWE was evaluated using the pre- and post-contrast black-blood MR images. Univariate and multivariate logistic regression analysis was performed to investigate the association of AWE with other risk factors, including size, maximal neck width, parent vessel diameter, location, multiplicity, daughter sacs and other clinical factors. The prevalence of AWE in each ISUIA grade was reported and compared by Wilcoxon rank sum test. In total, 61 aneurysms were detected in 48 patients. Aneurysm size was found to be an independent risk factor associated with AWE (OR 2.46 per mm increase, 95% CI 1.34-4.51; p = 0.004). Patient age was independently and inversely associated with AWE (OR 0.898 per year increase, 95% CI 0.812-0.994; p = 0.037). Higher prevalence of AWE was observed in larger aneurysms (12%, 71.4%, 100%, and 100% of ISUIA grade 1-4 IAs have AWE, respectively). Notably, 12% of small IAs (size <7 mm) exhibited AWE. The IAs with AWE had significant higher ISUIA grade than the IAs without (p < 0.001, Wilcoxon rank sum test). The wall enhancement in contrast-enhanced black-blood MR images was independently associated with aneurysm size in unruptured IAs. However, some small unruptured aneurysms did exhibit wall enhancement, suggesting that AWE may provide additional aneurysm instability information to improve current size-based rupture risk evaluation metrics.

Nonlinear Dynamics and Analysis of Intracranial Saccular Aneurysms with Growth and Remodeling

A new mathematical model for the interaction of blood flow with the arterial wall surrounded by cerebral spinal fluid is developed with applications to intracranial saccular aneurysms. The blood pressure acting on the inner arterial wall is modeled via a Fourier series, the arterial wall is modeled as a spring-mass system incorporating growth and remodeling, and the surrounding cerebral spinal fluid is modeled via a simplified one-dimensional compressible Euler equation with inviscid flow and negligible nonlinear effects. The resulting nonlinear coupled fluid-structure interaction problem is analyzed and a perturbation technique is employed to derive the first-order approximation solution to the system. An analytical solution is also derived for the linearized version of the problem using Laplace transforms. The solutions are validated against related work from the literature and the results suggest the biological significance of the inclusion of the growth and remodeling effects on the rupture of intracranial aneurysms.

Smooth Muscle Cell Foam Cell Formation, Apolipoproteins, and ABCA1 in Intracranial Aneurysms: Implications for Lipid Accumulation as a Promoter of Aneurysm Wall Rupture

Saccular intracranial aneurysm (sIA) aneurysm causes intracranial hemorrhages that are associated with high mortality. Lipid accumulation and chronic inflammation occur in the sIA wall. A major mechanism for lipid clearance from arteries is adenosine triphosphate-binding cassette A1 (ABCA1)-mediated lipid efflux from foam cells to apolipoprotein A-I (apoA-I). We investigated the association of wall degeneration, inflammation, and lipid-related parameters in tissue samples of 16 unruptured and 20 ruptured sIAs using histology and immunohistochemistry. Intracellular lipid accumulation was associated with wall remodeling (p = 0.005) and rupture (p = 0.020). Foam cell formation was observed in smooth muscle cells, in addition to CD68- and CD163-positive macrophages. Macrophage infiltration correlated with intracellular lipid accumulation and apolipoproteins, including apoA-I. ApoA-I correlated with markers of lipid accumulation and wall degeneration (p = 0.01). ApoA-I-positive staining colocalized with ABCA1-positive cells particularly in sIAs with high number of smooth muscle cells (p = 0.003); absence of such colocalization was associated with wall degeneration (p = 0.017). Known clinical risk factors for sIA rupture correlated inversely with apoA-I. We conclude that lipid accumulation associates with sIA wall degeneration and risk of rupture, possibly via formation of foam cells and subsequent loss of mural cells. Reduced removal of lipids from the sIA wall via ABCA1-apoA-I pathway may contribute to this process.

Irregular Shape of Intracranial Aneurysm Indicates Rupture Risk Irrespective of Size in a Population-Based Cohort.

Size and shape of saccular intracranial aneurysms (sIA) reflect the condition of the sIA wall and were risk factors for rupture in previous follow-up studies. We investigated how well size or shape identify rupture-prone sIAs. In a population-based registry, we investigated the characteristics of ruptured sIAs treated in a single neurosurgical center (1980-2014). In addition to univariate analysis, logistic regression was used in multivariate analysis, and sensitivity and specificity of size or shape were calculated using receiver operating characteristic curves. Ruptured sIAs were on average larger than unruptured sIAs (median, 7 versus 4 mm; P<0.000), but location and patient background affected the size at rupture. Of the ruptured sIAs, 38% were smaller than 7 mm and 18% were smaller than 4 mm. Of those sIAs that had ruptured at a small (<7 mm) size, 87% had an irregular shape. In multivariate analysis, irregular shape had the strongest association with presentation as ruptured sIA (odds ratio, 7.1; 95% confidence interval, 6.0-8.3), with better sensitivity (91%) and specificity (76%), in contrast to smoking (odds ratio, 0.7; 95% confidence interval, 0.6-0.9; sensitivity, 28%; specificity 57%) and Population, Hypertension, Age, Size of sIA, Earlier SAH from another sIA, Site of sIA score (odds ratio, 1.5; 95% confidence interval, 1.4-1.6). Irregular or multilobular shape is strongly associated with rupture in sIAs of all sizes and independent of location and patient background. Especially sIAs with irregular shape should be considered as high rupture risk lesions, even if small in diameter and in nonsmoking patients with low PHASES scores.

Wall expansion assessment of an intracranial aneurysm model by a 3D Digital Image Correlation System

Intracranial aneurysm is a local dilatation of an intracranial artery with high risk of rupture and death. Although it is generally accepted that the weakening of the arterial wall is the main cause for the rupture of an aneurysm, it still no consensus about the reasons for its creation, expansion and rupture. In particular, what is the role played by the blood flow in these phenomena. In this way, the aim of this work is the in vitro mechanical assessment of the wall expansion, namely the displacements, deformations and strains occurring in a saccular intracranial aneurysm model, when subjected to different flow rates. To obtain new insights into the mechanisms involved in the aneurysm rupture, a 3D-Vic™ Digital Image Correlation System was used and validated with a finite element analysis. The wall expansion results have revealed that the displacements, deformations and principal strains are directly related to the internal pressure caused by the fluid on the wall of the aneurism. These findings were especially observed in the weakened areas of the aneurysm model, where the wall was thinner. Furthermore, the technique used in this study has shown to be a potential method to validate numerical simulations of aneurysms, allowing the future performance of more complex and realistic haemodynamic studies.