Computational haemodynamics in two idealised cerebral wide-necked aneurysms after stent placement

Endovascular stents are being commonly used to treat cerebral wide-necked aneurysms recently. The effect of a stent placed in the parent artery is not only to protect the parent artery from occlusion, due to extension of coils and thrombosis, but also to act as flow diverter to vary the haemodynamics in the aneurysm. In this article, two idealised cerebral wide-necked aneurysms were created, one was sidewall aneurysm with curved parent vessel and the other was terminal aneurysm with the bifurcated parent vessel. The plexiglass models of the two aneurysms were 'treated' with commercial porous intravascular stents. The stented physical models were scanned by Micro-CT and the numerical models of the two idealised cerebral wide-necked aneurysms after stent placement were constructed from the scanned image files. The pulsatile flow of non-Newtonian fluid inside the models was simulated by using computational fluid dynamics package. From the simulated flow dynamics, various haemodynamic characteristics such as velocity contours, wall shear stress and oscillatory shear index (OSI) were computed. The velocity of the jet entering the sacs reduced after stent was deployed across the necks of both sidewall and terminal aneurysms; the wall shear stress on the distal neck of sidewall aneurysm reduced, the wall shear stress on the dome of the terminal aneurysm increased and the OSI on the dome of the terminal aneurysm reduced. Therefore, stent placement not only promotes thrombus formation in both aneurysm models but also reduces the regrowth risk of the sidewall aneurysm and the rupture risk of the terminal aneurysm.     

Computational haemodynamics in two idealised cerebral wide-necked aneurysms after stent placement

Endovascular stents are being commonly used to treat cerebral wide-necked aneurysms recently. The effect of a stent placed in the parent artery is not only to protect the parent artery from occlusion, due to extension of coils and thrombosis, but also to act as flow diverter to vary the haemodynamics in the aneurysm. In this article, two idealised cerebral wide-necked aneurysms were created, one was sidewall aneurysm with curved parent vessel and the other was terminal aneurysm with the bifurcated parent vessel. The plexiglass models of the two aneurysms were ‘treated’ with commercial porous intravascular stents. The stented physical models were scanned by Micro-CT and the numerical models of the two idealised cerebral wide-necked aneurysms after stent placement were constructed from the scanned image files. The pulsatile flow of non-Newtonian fluid inside the models was simulated by using computational fluid dynamics package. From the simulated flow dynamics, various haemodynamic characteristics such as velocity contours, wall shear stress and oscillatory shear index (OSI) were computed. The velocity of the jet entering the sacs reduced after stent was deployed across the necks of both sidewall and terminal aneurysms; the wall shear stress on the distal neck of sidewall aneurysm reduced, the wall shear stress on the dome of the terminal aneurysm increased and the OSI on the dome of the terminal aneurysm reduced. Therefore, stent placement not only promotes thrombus formation in both aneurysm models but also reduces the regrowth risk of the sidewall aneurysm and the rupture risk of the terminal aneurysm.     

Modeling the interaction of coils with the local blood flow after coil embolization of intracranial aneurysms

Aneurysmal recanalization and coil compaction after coil embolization of intracranial aneurysms are seen in as many as 40% of cases. Higher packing density has been suggested to reduce both coil compaction and recanalization. Basilar bifurcation aneurysms remain a challenge due possibly to the hemodynamics of this specific aneurysm/parent vessel architecture, which subjects the coil mass at the aneurysm neck to elevated and repetitive impingement forces. In the present study, we propose a new modeling strategy that facilitates a better understanding of the complex interactions between detachable coils and the local blood flow. In particular, a semiheuristic porous media set of equations used to describe the intra-aneurysmal flow is coupled to the incompressible Navier-Stokes equations governing the dynamics of the flow in the involved vessels. The resulting system of equations is solved in a strongly coupled manner using a finite element formulation. Our results suggest that there is a complex interaction between the local hemodynamics and intra-aneurysmal flow that induces significant forces on the coil mass. Although higher packing densities have previously been advocated to reduce coil compaction, our simulations suggest that lower permeability of the coil mass at a given packing density could also promote faster intra-aneurysmal thrombosis due to increased residence times.     

颅内动脉瘤栓塞术的临床分析

目的：用动脉瘤栓塞体积比评价颅内动脉瘤栓基术的治疗效果,观察颅内动脉瘤栓塞术治疗颅内动脉瘤的影响因素及颅内动脉瘤栓塞术的术后情况。方法：选取112例行血管内栓塞治疗的患者为研究对象,按术后动脉瘤栓塞体积比分成VER〉25％和VER〈25％两组,观察不同的栓塞材料（电解可脱弹簧圈、水解可脱弹簧圈）和术中血管的痉挛程度（轻、中、重）对栓塞程度的影响;术后随访106例病人,按动脉瘤栓塞体积比分成VER〉25％和VER〈25％两组,统计两组患者的再出血率和复发率,用动脉瘤栓塞体积比评价栓塞术的预后效果。结果：动脉瘤栓塞体积比VER〉25％和VER〈25％两组间进行比较,不同血管痉挛情况下和使用不同的栓塞材料在两组间均存在显著差异（P〈O．05）,具有统计学意义;术后随访半年,比较VER〉25％和VER〈25％两组的再出血率也有显著差异（P〈O．05）,具有统计学意义。结论：动脉瘤栓塞体积比在评价颅内动脉瘤栓塞术中有重要意义,血管痉挛情况、栓塞材料是影响颅内动脉瘤栓塞术栓塞疗效的主要影响因素;术后随访证实动脉瘤栓塞体积比对评价动脉瘤栓塞术的预后有一定的作用。     

球囊辅助栓塞技术治疗未破裂颅内动脉瘤的有效性及安全性分析

目的:探究球囊辅助栓塞技术治疗未破裂颅内动脉瘤的有效性和安全性。方法:选择2014年1月~2019年1月在本院介入诊疗科接受介入治疗的540例患者作为研究对象。根据治疗方案分为两组,球囊辅助栓塞组有340例,单纯栓塞组有200例。回顾性分析研究对象的一般资料、临床资料、手术并发症等情况。结果:球囊辅助栓塞组和单纯栓塞组在性别组成、年龄、颅内动脉瘤性质、位置、Hunt-Hess分级等方面,差异不具有统计学意义(P>0.05);在术后即刻及术后6个月血管造影结果显示,前者栓塞程度明显优于后者,两组差异具有统计学意义(P<0.05);前者改良Rankin量表评分明显优于后者,两组差异具有统计学意义(P=0.005);前者预后良好率明显高于后者,两组差异具有统计学意义(P<0.001);手术过程中,球囊辅助栓塞组发生2例破裂出血、2例脑血管痉挛、1例弹簧圈移位,单纯栓塞组发生2例破裂出血、1例栓塞、2例脑血管痉挛、3例弹簧圈移位。前者并发症发生率明显低于后者,两者差异具有统计学意义(P<0.001)。结论:在治疗未破裂颅内动脉瘤方面,球囊辅助栓塞技术的有效性、安全性明显优于单纯栓塞介入治疗,值得临床推广。     

介入栓塞治疗内脏动脉瘤的临床研究

目的:探讨介入血管腔内栓塞治疗内脏动脉瘤的方法、疗效及安全性。方法:选择内脏动脉瘤患者23例,包括脾动脉瘤13例,肝动脉瘤2例,胃十二指肠动脉瘤3例,肠系膜上动脉瘤4例,肾动脉瘤1例。其中,9例行远近端动脉栓塞术,4例采用支架辅助弹簧圈瘤体内填塞,3例采用弹簧圈瘤体内填塞加瘤体内注胶栓塞术,4例行弹簧圈瘤体内栓塞术,2例行分支动脉颗粒栓塞术,1例行单纯注胶栓塞术。术后1月、3月、6月行超声、CTA或血管造影复查,以后每年复查一次。结果:本组均成功行介入血管腔内栓塞治疗内脏动脉瘤,栓塞治疗后造影示动脉瘤体和/或载瘤动脉闭塞,动脉瘤体内无明显对比剂显影,脾动脉瘤栓塞患者有3例出现发热,脾区疼痛等脾梗塞症状,未见栓塞术相关严重并发症发生。4例消化道出血患者出血均停止。术后随访3~48个月,未见动脉瘤破裂出血、动脉瘤复发或增大,支架置入者,支架内及分支动脉血流均保持通畅。结论:介入血管腔内栓塞是一种治疗内脏动脉瘤的简便、微创、安全有效的方法。     

The Use of Solitaire AB Stents in Coil Embolization of Wide-Necked Cerebral Aneurysms

Background

The Solitaire AB stent is one of many assistant stents used for treating wide-necked cerebral aneurysm, and has been used since 2003. However, large sample studies on its safety and effectiveness are lacking. The objective of this study was to evaluate the effectiveness and safety of the Solitaire AB stent in the coil embolization of wide-necked cerebral aneurysms.

Methods

Retrospective review of the clinical and image data of 116 patients with wide-necked cerebral aneurysms who had been enrolled at six interventional neuroradiology centers from February 2010 to February 2014 and had been treated by coil embolization; in total, 120 Solitaire AB stents were used. The degree of aneurysm occlusion was examined using digital subtraction angiography (DSA) immediately after the procedure and during follow-up, and was graded using the modified Raymond classification. We also observed complications to evaluate the safety and effectiveness of this therapy.

Results

The 120 Solitaire AB stents (4 mm × 15 mm, four stents; 4 mm × 20 mm, 16 stents; 6 mm × 20 mm, 36 stents; 6 mm × 30 mm, 64 stents) were inserted to treat 120 wide-necked cerebral aneurysms. All stents were inserted successfully. DSA immediately post-surgery revealed 55 cases of complete occlusion, 59 cases of neck remnant, and six cases of aneurysm remnant. Perioperatively, there were four cases of hemorrhage and four cases of stent thrombosis. The follow-up spanned 3–37 months; of 92 patients examined by DSA at the 6-month follow up, 12 had disease recurrence.

Conclusions

The Solitaire AB stent is effective with a good technical success rate and short-term effect for assisting coil embolization of wide-necked cerebral aneurysms.     

Interlock可解脱弹簧圈在脾动脉瘤腔内治疗中的应用

目的:探究Interlock可解脱弹簧圈在脾动脉瘤的腔内治疗中的应用价值。方法:回顾性分析2016年2月至2019年2月于本中心使用Interlock可解脱弹簧圈治疗的36例脾动脉瘤患者的临床资料,包括10例男性,26例女性,31例真性动脉瘤,5例假性脾动脉瘤,术前均行超声或CTA明确诊断。术中栓塞后,立即血管造影以明确技术成功率。围手术期及术后2周、3个月和6个月监测血常规、胰淀粉酶和主动脉CTA,观察并发症的发生情况。结果:6例患者弹簧圈栓塞动脉瘤远近端及瘤腔,其余仅栓塞脾动脉瘤瘤腔。术中DSA血管造影提示即刻脾动脉瘤栓塞闭塞率为97%以上,术中共使用128枚Interlock弹簧圈,其中104枚为钻石型,24枚为普通2D型。弹簧圈平均直径为6.3±4.2(2-12)mm,平均长度为16±13.5(3-32)mm,瘤体平均尺寸为40.6±12.5(15-70) mm。围手术期无并发症发生。平均随访10.0±3.2(6-15)个月,1月后2例出现脾梗死,7例发生轻微腹痛及低热等症状,所有病例均未见瘤腔再通和瘤体增大。结论:Interlock可解脱弹簧圈可以安全有效地治疗脾动脉瘤,但其远期疗效需长期随访观察。     

栓塞治疗颅内动脉瘤的并发症及处理方法分析

目的:分析栓塞治疗颅内动脉瘤过程中并发症的发生原因及处理方法。方法:回顾性分析微弹簧圈栓塞治疗的97例颅内动脉瘤患者的临床资料,包括性别、年龄、Hunt-Hess分级,对住院患者进行术前整体状况评估。影像学检查主要记录动脉瘤的位置、瘤体长度和瘤颈宽度,测量其长宽比例。血管内介入手术治疗观察各种介入治疗方法以及相关并发症。结果:本组97例颅内动脉瘤患者中,男44例、女53例,男性平均年龄51.3岁,女性平均年龄46.7岁,男女共同平均年龄48.7岁。颈内动脉-后交通支及其附近动脉瘤51个,前交通动脉和大脑前动脉29个,大脑中动脉11个,椎-基底动脉系统6个,所用到的栓塞材料包括各种弹簧圈、颅内支架、不可脱球囊等。97例中15例出现并发症(15.5%),动脉瘤破裂出血4例,术中发生血管痉挛3例,血栓形成或血栓性栓塞5例,3例死亡。结论:栓塞治疗颅内动脉瘤过程中最主要并发症包括动脉瘤破裂、栓塞和血栓形成、血管痉挛等,术前评估、术中谨慎操作以及正确及时的处理能够降低栓塞治疗颅内动脉瘤的并发症。     

Flow dynamics in Models of Intracranial Terminal Aneurysms

Flow dynamics play an important role in the pathogenesis and treatment of intracranial aneurysms. The evaluation of the velocity field in the aneurysm dome and neck is important for the correct placement of endovascular coils, and the temporal and spatial variations of wall shear stress in the aneurysm are correlated with its growth and rupture. This numerical investigation describes the hemodynamic in two models of terminal aneurysm of the basilar artery. Aneurysm models with a aspect ratio of 1.0 and 1.67 were studied. Each model was subject to physiological representative waveform of inflow for a mean Reynolds number of 560. The effects of symmetric and asymmetric outflow conditions in the branches were studied.     

Nonlinear anisotropic stress analysis of anatomically realistic cerebral aneurysms

BACKGROUND: Static deformation analysis and estimation of wall stress distribution of patient-specific cerebral aneurysms can provide useful insights into the disease process and rupture. METHOD OF APPROACH: The three-dimensional geometry of saccular cerebral aneurysms from 27 patients (18 unruptured and nine ruptured) was reconstructed based on computer tomography angiography images. The aneurysm wall tissue was modeled using a nonlinear, anisotropic, hyperelastic material model (Fung-type) which was incorporated in a user subroutine in ABAQUS. Effective material fiber orientations were assumed to align with principal surface curvatures. Static deformation of the aneurysm models were simulated assuming uniform wall thickness and internal pressure load of 100 mm Hg. RESULTS: The numerical analysis technique was validated by quantitative comparisons to results in the literature. For the patient-specific models, in-plane stresses in the aneurysm wall along both the stiff and weak fiber directions showed significant regional variations with the former being higher. The spatial maximum of stress ranged from as low as 0.30 MPa in a small aneurysm to as high as 1.06 MPa in a giant aneurysm. The patterns of distribution of stress, strain, and surface curvature were found to be similar. Sensitivity analyses showed that the computed stress is mesh independent and not very sensitive to reasonable perturbations in model parameters, and the curvature-based criteria for fiber orientations tend to minimize the total elastic strain energy in the aneurysms wall. Within this small study population, there were no statistically significant differences in the spatial means and maximums of stress and strain values between the ruptured and unruptured groups. However, the ratios between the stress components in the stiff and weak fiber directions were significantly higher in the ruptured group than those in the unruptured group. CONCLUSIONS: A methodology for nonlinear, anisotropic static deformation analysis of geometrically realistic aneurysms was developed, which can be used for a more accurate estimation of the stresses and strains than previous methods and to facilitate prospective studies on the role of stress in aneurysm rupture.     

Comparison of the Association of Sac Growth and Coil Compaction with Recurrence in Coil Embolized Cerebral Aneurysms

Background and Purpose

In recurrent cerebral aneurysms treated by coil embolization, coil compaction is regarded as the presumptive mechanism. We test the hypothesis that aneurysm growth is the primary recurrence mechanism. We also test the hypothesis that the coil mass will translate a measurable extent when recurrence occurs.

Methods

An objective, quantitative image analysis protocol was developed to determine the volumes of aneurysms and coil masses during initial and follow-up visits from 3D rotational angiograms. The population consisted of 15 recurrence and 12 non-recurrence control aneurysms initially completely coiled at a single center. An investigator sensitivity study was performed to assess the objectivity of the methods. Paired Wilcoxon tests (p<0.05, one-tailed) were performed to assess for aneurysm and coil growth. The translation of the coil mass center at follow-up was computed. A Mann Whitney U-Test (p<0.05, one-tailed) was used to compare translation of coil mass centers between recurrence and control subjects.

Results

Image analysis protocol was found to be insensitive to the investigator. Aneurysm growth was evident in the recurrence cohort (p=0.003) but not the control (p=0.136). There was no evidence of coil compaction in either the recurrence or control cohorts (recurrence: p=0.339; control: p=0.429). The translation of the coil mass centers was found to be significantly larger in the recurrence cohort than the control cohort (p=0.047).

Conclusion

Aneurysm sac growth, not coil compaction, was the primary mechanism of recurrence following successful coil embolization. The coil mass likely translates to a measurable extent when recurrence occurs and has the potential to serve as a non-angiographic recurrence marker.     

Finite element modeling of embolic coil deployment: Multifactor characterization of treatment effects on cerebral aneurysm hemodynamics

Endovascular coiling is the most common treatment for cerebral aneurysms. During the treatment, a sequence of embolic coils with different stiffness, shapes, sizes, and lengths is deployed to fill the aneurysmal sac. Although coil packing density has been clinically correlated with treatment success, many studies have also reported success at low packing densities, as well as recurrence at high packing densities. Such reports indicate that other factors may influence treatment success. In this study, we used a novel finite element approach and computational fluid dynamics (CFD) to investigate the effects of packing density, coil shape, aneurysmal neck size, and parent vessel flow rate on aneurysmal hemodynamics. The study examines a testbed of 80 unique CFD simulations of post-treatment flows in idealized basilar tip aneurysm models. Simulated coil deployments were validated against in vitro and in vivo deployments. Among the investigated factors, packing density had the largest effect on intra-aneurysmal velocities. However, multifactor analysis of variance showed that coil shape can also have considerable effects, depending on packing density and neck size. Further, linear regression analysis showed an inverse relationship between mean void diameter in the aneurysm and mean intra-aneurysmal velocities, which underscores the importance of coil distribution and thus coil shape. Our study suggests that while packing density plays a key role in determining post-treatment hemodynamics, other factors such as coil shape, aneurysmal geometry, and parent vessel flow may also be very important.     

Posterior Cerebral Artery Angle and the Rupture of Basilar Tip Aneurysms

Since the initial publication of the International Study of Unruptured Intracranial Aneurysms (ISUIA), management of unruptured intracranial aneurysms has been mainly based on the size of the aneurysm. The contribution of morphological characteristics to treatment decisions of unruptured aneurysms has not been well studied in a systematic and location specific manner. We present a large sample of basilar artery tip aneurysms (BTA) that were assessed using a diverse array of morphological variables to determine the parameters associated with ruptured aneurysms. Demographic and clinical risk factors of aneurysm rupture were obtained from chart review. CT angiograms (CTA) were evaluated with Slicer, an open source visualization and image analysis software, to generate 3-D models of the aneurysms and surrounding vascular architecture. Morphological parameters examined in each model included aneurysm volume, aspect ratio, size ratio, aneurysm angle, basilar vessel angle, basilar flow angle, and vessel to vessel angles. Univariate and multivariate analyses were performed to determine statistical significance. From 2008–2013, 54 patients with BTA aneurysms were evaluated in a single institution, and CTAs from 33 patients (15 ruptured, 18 unruptured) were available and analyzed. Aneurysms that underwent reoperation, that were associated with arteriovenous malformations, or that lacked preoperative CTA were excluded. Multivariate logistic regression revealed that a larger angle between the posterior cerebral arteries (P1-P1 angle, p = 0.037) was most strongly associated with aneurysm rupture after adjusting for other morphological variables. In this location specific study of BTA aneurysms, the larger the angle formed between posterior cerebral arteries was found to be a new morphological parameter significantly associated with ruptured BTA aneurysms. This is a physically intuitive parameter that can be measured easily and readily applied in the clinical setting.     

脑血管畸形破裂出血的影响因素及受试者工作特征曲线预测价值分析

目的:探讨脑血管畸形破裂出血的影响因素,并进行受试者工作特征(ROC)曲线分析。方法:回顾性分析我院2015年6月至2018年1月收治的138例脑血管畸形患者的临床资料,根据患者是否并发破裂出血,将其分为出血组(n=76)和未出血组(n=62)。采用单因素和多因素Logistic回归分析法对两组患者的临床资料进行研究,并采用ROC曲线评价各影响因素对脑血管畸形破裂出血的预测价值。结果:两组患者在与畸形血管团位置关系、是否合并硬脑膜动静脉瘘、合并动脉瘤数目、合并动脉瘤大小、合并瘤样变、供血动脉位置、引流静脉方向以及畸形血管团大小方面差异具有统计学意义(P0.05)。多因素Logistic回归分析结果显示,引流静脉方向、畸形血管团大小以及合并动脉瘤数目是脑血管畸形破裂出血的独立危险因素(P0.05)。引流静脉方向的ROC曲线下面积为0.921,特异度和灵敏度分别为0.832和0.801,是三种影响因素中预测价值最高的,其次是合并动脉瘤数目和畸形血管团大小。结论:合并动脉瘤、引流静脉方向以及畸形动脉血管团大小是脑血管畸形破裂出血的重要危险因素,且对脑血管畸形破裂出血具有一定的预测价值,可为脑血管畸形破裂出血的预防诊治提供参考。     

自膨式支架辅助弹簧圈栓塞治疗颅内动脉瘤的疗效及安全性分析

摘要 目的：探讨自膨式支架辅助弹簧圈栓塞治疗颅内动脉瘤的疗效及安全性。方法：回顾性分析2014年1月-2019年1月我院采取自膨式支架辅助弹簧圈栓塞治疗颅内动脉瘤患者159例（A组）及采取单纯弹簧圈栓塞治疗颅内动脉瘤患者178例（B组）,比较两种手术方法治疗颅内动脉瘤的手术时间、术后住院时间、随访时间、手术相关并发症发生率并通过格拉斯哥（GOS）预后评分、Raymond分级比较2种治疗方法的安全性及有效性。结果：两组手术时间、术后住院时间、随访时间比较差异无统计学意义（P＞0.05）。两组术后出血及缺血事件发生率差异有统计学意义（P＜0.05）,脑积水、肺炎发生率、致死率及致残率差异无统计学意义（连续校正后P=1）。术后1月内及术后12个月随访GOS评分,A组评分高于B组,差异具有统计学意义（P＜0.05）;术后1月内及术后12个月随访Raymond分级,A组优于B组,差异具有统计学意义（P＜0.05）。结论：自膨式支架辅助弹簧圈栓塞治疗颅内动脉瘤栓塞效果明显且术后并发症少,对于颅内动脉瘤患者在弹簧圈栓塞基础上应用自膨式支架辅助可提高手术安全性及栓塞的疗效。     

The Management of Vertebrobasilar Dissecting Aneurysm Using Endovascular Embolization

To explore the imaging features of the vertebrobasilar artery dissecting aneurysm (VBA-DA) and to evaluate the effect of endovascular treatments. Five patients with VBA-DA undergoing endovascular treatments were retrospectively studied. Stent-alone technique was used to treat two of the patients, stent-assisted coil embolization of aneurysm in one patient, coil embolization of parent artery in the other patient, and stent-assisted coil embolization of parent artery in the last patient. Postoperative angiography revealed complete occlusion of aneurysm in two patients and delayed image development in three patients. One patient suffered postoperative cerebral hemorrhage without any neurological deficits. Five patients achieved favorable outcomes on both the imaging results and clinical recovery during a mean follow-up of 20.2 months (range 6–90?months). The string sign pearl and string sign and double-lumen sign are typical imaging features of VBA-DA. Treatment modality is determined by the imaging results. Endovascular embolization is a minimally-invasive, safe, effective, and reliable intervention for managing VBA-DA.     

Flow instability detected in ruptured versus unruptured cerebral aneurysms at the internal carotid artery

Flow instability has emerged as a new hemodynamic metric hypothesized to have potential value in assessing the rupture risk of cerebral aneurysms. However, diverse findings have been reported in the literature. In the present study, high-resolution hemodynamic simulations were performed retrospectively on 35 aneurysms (10 ruptured & 25 unruptured) located at the internal carotid artery (ICA). Simulated hemodynamic parameters were statistically compared between the ruptured and unruptured aneurysms, with emphasis on examining the correlation of flow instability with the status of aneurysm rupture. Pronounced flow instability was detected in 20% (2 out of 10) of the ruptured aneurysms, whereas in 44% (11 out of 25) of the unruptured aneurysms. Statistically, the flow instability metric (quantified by the temporally and spatially averaged fluctuating kinetic energy over the aneurysm sac) did not differ significantly between the ruptured and unruptured aneurysms. In contrast, low wall shear stress area (LSA) and pressure loss coefficient (PLC) exhibited significant correlations with the status of aneurysm rupture. In conclusion, the present study suggests that the presence of flow instability may not correlate closely with the status of aneurysm rupture, at least for ICA aneurysms. On the other hand, the retrospective nature of the study and the small sample size may have to some extent compromised the reliability of the conclusion, and therefore large-scale prospective studies would be needed to further address the issue.     

An Analysis of 1256 Cases of Sporadic Ruptured Cerebral Aneurysm in a Single Chinese Institution

Background

To review the epidemiology of sporadic ruptured cerebral aneurysm.

Methods

This is a retrospective study of consecutive 1256 Chinese patients between January 2006 and January 2013, who were admitted to the Second Hospital of Hebei Medical University, China, for spontaneous subarachnoid hemorrhage due to a rupture of cerebral artery aneurysm. In 288 males and 478 females, the size of aneurysms was measured by a neuroradiologist on DSA. In 123 males and 184 females, the size of the ruptured aneurysms was not measured. The remaining patients, with 61 males and 122 females, had multiple aneurysms, and the medical record could not reliably determine the specific aneurysm responsible for the rupture.

Results

In total there were 784 females and 472 males with a female/male ratio of 1.66. The female/male ratio was down to 0.50 for patients younger than 35 yrs. For both males and females, aneurysm rupture was most common during the age of 50–59 yrs. Ruptured aneurysms were mostly of 2 mm–5 mm in size (47.1%), followed by 5 mm–10 mm (39.7%). Ruptured single cerebral aneurysm occurred in anterior circulation in 95.0% of the cases, with 5.0% occurred in posterior circulation. Ruptured aneurysm most commonly occurred at posterior communicating artery (34.9%) and anterior communicating artery (29.5%). 183 cases (14.6%) had multiple aneurysms.

Conclusions

With younger patients, there is a male predominance in our series. Ninety percent of patients have ruptured aneurysms less than 10 mm in size.     

Stability of pulsatile blood flow at the ostium of cerebral aneurysms

The strength and direction of blood flow into and within a cerebral aneurysm are important issues in developing effective interventional strategies to stabilize the aneurysm. We tested the hypothesis that there are significant major hemodynamic features that are common to many aneurysm flows of the type studied here. This was investigated by performing computational fluid dynamic simulations of flow near 7 cerebral aneurysms using geometrical data obtained from clinical CT scans. Our numerical simulations of flow across the ostium plane of an aneurysm show that in many cases there is relatively stable flow structure that is maintained over the phase of the pulsatile flow cycle. The two main features of this flow are (1) quasi-permanent regions of flow influx and efflux across the ostium plane exist, separated by a “virtual boundary”, and (2) a helical vortex flow pattern within the aneurismal sac with swirl in two orthogonal cross-sectional planes. These numerical observations are consistent with in vitro experimental data from ultrasound color-Doppler velocimetry and other numerical and experimental studies. The observed flow patterns are found to occur in different types of aneurysms (bifurcation and sidewall), and can persist even after flow parameters are perturbed beyond the normal range of physiological flow conditions. These results suggest that in many cases, major aspects of the behavior of aneurismal hemodynamics for important classes of aneurysms can be learned from an analysis of steady, non-pulsatile flow, which is simpler and faster to simulate than time-dependent, pulsatile flow. An understanding of this fluid dynamical behavior may also prove useful in the design of stents, coils, and various other endovascular flow diverting devices.