Vascular geometry change because of endovascular stent placement for anterior communicating artery aneurysms

Ongoing Geometric Remodeling of the Parent Artery After Flow-Diverter Stent Reconstruction in Cerebral Aneurysms: The Device Design Matters

OBJECTIVE

Configuration changes of the parent artery (PA) after flow-diverter (FD) stent reconstruction, caused by the bending force of the device, may have an additional role in aneurysm occlusion as a result of the secondary alteration of intra-aneurysmal hemodynamics related to the geometry alteration of the vessel. To determine the degree of PA deformation and aneurysm occlusion rates after deployment of 2 different types of FD.

METHODS

Patients treated with 2 different designs of cobalt-chromium braid (48 and 64 wire braid) structure FD were subject to analysis. Vascular angle changes at the level of the reconstructed segment immediately after FD deployment and at 1 year follow-up were measured and the potential relationship with aneurysmal occlusion rate was analyzed.

RESULTS

Forty-two patients harboring 48 aneurysms were included in the present study. The aneurysms were divided into side wall (85.4%) and bifurcation types (14.6%). Twenty-six aneurysms were treated using the Pipeline FD (48 wire braid; 54.2%) and 22 using the Evolve FD (64 wire braid; 45.8%). Of the 48 aneurysms, 42 (87.5%) met the primary end point of complete occlusion at 12 months. The median postdeployment angle change was 7.04°± 4.59° for the Pipeline and 5.05°± 2.49° for the Evolve, whereas the median 12 months follow-up angle change was 15.49°± 10.99° and 10.01°± 8.83°, respectively. PA angle changes were significantly higher in the bifurcation group compared with the side wall group both during procedure and at 12 months follow-up. Angle change had a statistically nonsignificant association with complete aneurysm occlusion.

CONCLUSIONS

PA deformation starts immediately after deployment and remodeling continues for 1 year after. Aneurysms located in the vessel bifurcation were more prone to PA straightening after FD deployment than were side wall aneurysms. Furthermore, Pipeline seemed to be more prone to inducing vascular deformation, compared with Evolve.

The Safety and Efficacy of Leo Stents with Coiling or Alone for Anterior Cerebral Artery Aneurysms

INTRODUCTION

Treatment of anterior cerebral artery (ACA) aneurysms is still not well established. The Leo stent with blood flow direction is a retrievable stent for intracranial aneurysms, whereas it needs to be studied clearly in patients with ACA aneurysms.

METHODS

Consecutive patients with ACA aneurysms were retrospectively enrolled in three neurosurgical centers between January 2016 and October 2021. The data on demographics, aneurysm characteristics, symptom resolution, and postoperative course were collected and analyzed. The aneurysm occlusion status was appraised by Raymond-Ray Occlusion Class (RROC).

RESULTS

A total of 57 patients with ACA aneurysms were included in our study. Immediate postprocedural angiograms showed that 20 aneurysms (35.1%) were in complete occlusion (RROC 1), 26 aneurysms (45.6%) were in near-complete occlusion (RROC 2), 11 aneurysms (19.3%) were in incomplete occlusion (RROC 3). The angiographic follow-up found that the rate of complete occlusion increased to 57.9%, and near-completion and incomplete occlusion dropped to 29.8% and 12.3%, respectively. The angiographic result of the last follow-up improved significantly (Z=- 2.805, P=0.005). Univariate analysis indicated that distal location of aneurysms (Z=4.538, P=0.033) and ruptured aneurysms (χ2=.6120, P=0.032) were potential risk factors for intra-parent artery narrowing. Furthermore, multivariate logistic regression analysis found that A3 aneurysms (95% CI 1.427~32.744, P=0.016) are the key risk factor for intra-parent artery narrowing.

CONCLUSIONS

The Leo stent is safe and effective for aneurysms located in ACA circulations. The overall occlusion degree improved during follow-up. A distal, small artery was the risk factor for intra-parent artery narrowing.

Predisposing factors for the deformation of parent artery of anterior circulation saccular aneurysm after stent-assisted embolization: A retrospective cohort study

BACKGROUND

It has been previously reported in several studies that deformation of parent artery (DPA) occurs after stent-assisted coil embolization (SACE) for intracranial aneurysms (IAs).

OBJECTIVE

To investigate the predisposing factors of stent-induced DPA, as well as its effect on the follow-up of aneurysm embolization.

METHODS

Clinical and imaging data were collected from 198 patients (201 aneurysms). Angles of the stent-covered parental artery were measured before treatment and during follow-up. Cases in which the angle had changed more than 5 degrees, were defined as DPA. The related factors of DPA were analyzed. The relation between DPA and follow-up results was also studied.

RESULTS

Univariate analysis revealed that sex (p = 0.014), age (p = 0.017), aneurysm location (p < 0.001), stent type (p < 0.001), aneurysm size (p = 0.019), and pretreatment angle (p = 0.002) correlated with DPA. On the other hand, multivariate analysis revealed that aneurysms located in the anterior communicating artery (ACOA) (OR = 4.559, p = 0.013) and middle cerebral artery (MCA) (OR = 9.474, p < 0.001) were independent predisposing factors for DPA after stent implantation, whereas a braided stent (OR = 0.221, p = 0.030), flow diverter (FD) device (OR = 0.100, p = 0.028) were negative factors to develop DPA. The complete occlusion rate in the DPA group was higher (p = 0.035) than in the non-DPA group.

CONCLUSIONS

Aneurysms located in ACOA and MCA are more prone to DPA after SACE than aneurysms at other locations in the anterior circulation, braided stents and FD devices do not predispose to induce vascular deformation. DPA may be beneficial for the long-term cure of IAs after SACE.

Understanding anterior communicating artery aneurysms: A bibliometric analysis of top 100 most cited articles

Bibliometric analysis is of paramount importance in assessing the research impact wherein studies are ranked on the basis of citations received. It also brings out the excellent contribution of authors and journals in adding evidence for future research. This study aimed at evaluating the top 100 most cited articles on anterior communicating artery (ACoA) Aneurysms. Scopus database was searched using title specific search for the aneurysm of ACoA and top 100 most cited articles along with their authors, author IDs, affiliated institutions, countries and funding bodies were identified. Search yielded 841 articles and top 100 articles were identified to include in this analysis which secured 5615 citations. Citations per year was also calculated to minimize the risk of bias. Maximum citations by any article were 242. The United States was the major contributor to the number of articles while Kessler Institute for Rehabilitation became the highest contributing institution. DeLuca J proved to be a pioneer in this specialized area as he penned 6 studies being first author in 4 of them, making him the most frequent author. National Institutes of Health and the U.S. Department of Health and Human Services were the main funding bodies. Subcategory analysis revealed, 50% studies provided evidence for the treatment and the surgical outcome of the aneurysm. Studies like these can aid in better neurological and neurosurgical management in decision making of ACoA aneurysm.

Intra-procedural complications, success rate, and need for retreatment of endovascular treatments in anterior communicating artery aneurysms: a systematic review and meta-analysis

In recent years, intracranial aneurysms have been widely treated with endovascular methods. The anterior communicating artery (Acom) is the most common site of intracranial aneurysms. Despite its effectiveness, endovascular interventions can be associated with various intra-procedural and post-procedural complications. A systematic review of the literature was performed through PubMed, Embase, Scopus, and Web of Sciences databases up to March 18, 2022. The pooled rates of intra-procedural complications, mortality, procedure-related morbidities, the immediate and late aneurysm occlusion, and also the necessity for retreatment were calculated by applying random-effects models. A total of 41 articles with 4583 patients were included in the meta-analysis. The pooled rate of overall intra-procedural complications was 9.6% (95% CI: 7.7 to 11.8%). The initial rupture status and also type of EVT procedure did not affect the overall complication rate. The pooled rate of intra-procedural thrombosis, aneurysm rupture, coil prolapse, and early aneurysm rebleeding were 6.1% (95% CI: 4.5 to 8.2%); 4.2% (95% CI: 3.4 to 5.2%), 4.7% (95% CI: 3.2 to 6.7%), and 2.2% (95% CI: 1.5 to 3.2%), respectively. Our analysis showed that intra-procedural mortality occurred in 1.7% (95% CI: 1.1 to 2.5%) and procedure-related permanent morbidities in 3.3% (95% CI: 2.3 to 4.7%) of patients. Endovascular methods achieved complete and near to complete aneurysm occlusion (Raymond-Roy occlusion classification 1 and 2) in 89.2% (95% CI: 86.4 to 92.5%) of cases post-procedure, and 9.5% (95% CI: 7.3 to 12.4%) of patients needed retreatment due to recanalization in follow-ups. Endovascular treatment can serve as an acceptable method for Acom aneurysms. However, improved endovascular treatment equipment and new techniques provide more satisfactory outcomes for complicated cases.

Hemodynamic Effects of Stent-Induced Straightening of Parent Artery vs. Stent Struts for Intracranial Bifurcation Aneurysms

Objective

This study aims to compare the hemodynamic impact of stent-mesh and stent-induced straightening of the parent artery in intracranial bifurcation aneurysms using finite element method simulation.

Material and Methods

Three intracranial bifurcation aneurysms treated with different stent-assisted coil embolization were evaluated. Simulation using the finite element method was conducted for Solitaire, LVIS and Neuroform stents. Four models of each stent were established, including a pre-treatment baseline, stenting without parent artery straightening (presented as stent-mesh effect), no-stent with parent artery reconstruction (to reveal the straightening impact), and stenting with straightening (categorized as Models I–IV respectively). Hemodynamic characteristics of the four models for each stent were compared.

Results

In the Neuroform stent, compared with the pre-treatment model (100%), the mean WSS decreased to 82.3, 71.4, and 57.0% in Models II-IV, velocity to 88.3, 74.4, and 62.8%, and high flow volume (HFV, >0.3 m/s) to 77.7, 44.0, and 19.1%. For the LVIS stent, the mean WSS changed to 105.0, 40.2, and 39.8% in Models II to IV; velocity to 91.2, 58.1, and 52.5%, and HFV to 92.0, 56.1, and 43.9%. For the Solitaire stent, compared with the pre-treatment model (100%), the mean WSS of Models II-IV changed altered by 105.7, 42.6, and 39.4%, sac-averaged velocity changed to 111.3, 46.6, and 42.8%, and HFV 115.6, 15.1, and 13.6%.

Conclusion

The hemodynamic effect of straightening the parent artery of intracranial bifurcation aneurysms by stenting was noticeably improved over stent mesh diversion in all three stents tested. Therefore stent-induced remodeling of the parent artery appears to be the best method of decreasing recurrence in intracranial bifurcation aneurysms.

Parent Artery Straightening after Flow-Diverter Stenting Improves the Odds of Aneurysm Occlusion

BACKGROUND AND PURPOSE

Intracranial stents for the treatment of aneurysms can be responsible for parent artery straightening, a phenomenon with potential consequences for aneurysmal occlusion. We aimed to evaluate parent artery straightening following flow-diverter stent placement in patients with intracranial aneurysms and explored the association between parent artery straightening and subsequent aneurysm occlusion.

MATERIALS AND METHODS

All patients treated with flow-diverter stents for anterior circulation aneurysms located downstream from the carotid siphon between January 2009 and January 2018 were screened for inclusion. Parent artery straightening was defined as the difference (α-β) in the parent artery angle at the neck level before (α angle) and after flow-diverter stent deployment (β angle). We analyzed the procedural and imaging factors associated with parent artery straightening and the associations between parent artery straightening and aneurysmal occlusion.

RESULTS

Ninety-five patients met the inclusion criteria (n = 64/95 women, 67.4%; mean age, 54.1 [SD, 11.2]  years) with 97 flow-diverter stents deployed for 99 aneurysms. Aneurysms were predominantly located at the MCA bifurcation (n = 44/95, 44.4%). Parent artery straightening was found to be more pronounced in patients treated with cobalt chromium stents than with nitinol stents (P = .02). In multivariate analysis, parent artery straightening (P = .04) was independently associated with aneurysm occlusion after flow-diverter stent deployment.

CONCLUSIONS

The use of flow-diverter stents for distal aneurysms induces a measurable parent artery straightening, which is associated with higher occlusion rates. Parent artery straightening, in our sample, appeared to be more prominent with cobalt chromium stents than with nitinol stents. This work highlights the necessary trade-off between navigability and parent artery straightening and may help tailor the selection of flow-diverter stents to aneurysms and parent artery characteristics.

The Safety and Efficacy of Endovascular Treatment for Very Small Ruptured Anterior Communicating Artery Aneurysms: A Large Single-Center Experience With 81 Consecutive Cases

OBJECTIVE

This study aimed to investigate the safety and efficacy of endovascular embolization for very small ruptured anterior communicating artery (AcomA) aneurysms.

METHODS

From August 2015 to June 2020, 81 patients with very small (≤3 mm) ruptured AcomA aneurysms treated endovascularly were enrolled in this study. Clinical and radiographic data were analyzed retrospectively, including the aneurysm occlusion rate, complications, and clinical outcome.

RESULTS

Among 81 patients, simple coiling embolization was performed in 52 cases and stent-assisted embolization in 29 cases. Immediate angiography demonstrated complete occlusion in 59 (72.8%) aneurysms, residual neck in 20 (24.7%) aneurysms, and residual lumen in 2 (2.5%). Procedure-related complications rate was 2.5% (2 of 81), all of which were transient thromboembolic events. Angiographic follow-up outcomes of 60 patients (mean: 6.8 ± 3.2 months) revealed complete occlusion in 91.7% (55 of 60), with recurrence in 1 patient. The mean clinical follow-up time was 22.6 ± 11.4 months and good prognosis rates (6-month modified Rankin Scale score: 0-2) reached 90.2% (73 of 81). The differences in aneurysm occlusion and procedure-related complications between the simple coiling group and the stent-assisted coiling group were not statistically significant.

CONCLUSIONS

Coiling with or without stent-assisted technique for the treatment of very small ruptured AcomA aneurysms was safe and effective.

Safety and efficacy of stent-assisted coiling for acutely ruptured wide-necked intracranial aneurysms: comparison of LVIS stents with laser-cut stents

Background

To compare the safety and efficacy of LVIS stent-assisted coiling with those of laser-cut stent-assisted coiling for the treatment of acutely ruptured wide-necked intracranial aneurysms.

Methods

Patients with acutely ruptured wide-necked intracranial aneurysms treated with LVIS stent-assisted coiling (LVIS stent group) and laser-cut stent-assisted coiling (laser-cut stent group) were retrospectively reviewed from January 2014 to December 2017. Propensity score matching was used to adjust for potential differences in age, sex, aneurysm location, aneurysm size, neck width, Hunt-Hess grade, and modified Fisher grade. Perioperative procedure-related complications and clinical and angiographic follow-up outcomes were compared. Univariate and multivariate analyses were performed to determine the associations between procedure-related complications and potential risk factors.

Results

A total of 142 patients who underwent LVIS stent-assisted coiling and 93 patients who underwent laser-cut stent-assisted coiling were enrolled after 1:2 propensity score matching. The angiographic follow-up outcomes showed that the LVIS stent group had a slightly higher complete occlusion rate and lower recurrence rate than the laser-cut stent group (92.7% vs 80.6%; 3.7% vs 9.7%, P = 0.078). The clinical outcomes at discharge and follow-up between the two groups demonstrated no significant differences (P = 0.495 and P = 0.875, respectively). The rates of intraprocedural thrombosis, postprocedural thrombosis, postoperative early rebleeding, and procedure-related death were 0.7% (1/142), 1.4% (2/142), 2.8% (4/142), and 2.1% (3/142) in the LVIS stent group, respectively, and 4.3% (4/93), 2.2% (2/93), 1.1% (1/93), and 3.2% (3/93) in the laser-cut stent group, respectively (P = 0.082, 0.649, 0.651, and 0.683). Nevertheless, the rates of overall procedure-related complications and intraprocedural rupture in the LVIS stent group were significantly lower than those in the laser-cut stent group (5.6% vs 14.0%, P = 0.028; 0.7% vs 6.5%, P = 0.016). Multivariate analysis showed that laser-cut stent-assisted coiling was an independent predictor for overall procedure-related complications (OR = 2.727, P = 0.037); a history of diabetes (OR = 7.275, P = 0.027) and other cerebrovascular diseases (OR = 8.083, P = 0.022) were independent predictors for ischemic complications, whereas none of the factors were predictors for hemorrhagic complications.

Conclusions

Compared with laser-cut stent-assisted coiling, LVIS stent-assisted coiling for the treatment of acutely ruptured wide-necked intracranial aneurysms could reduce the rates of overall procedure-related complications and intraprocedural rupture.

Stent-Induced Vascular Remodeling in Two-Step Stent-Assisted Coiling Treatment of Brain Aneurysms: A Closer Look Into the Hemodynamic Changes During the Stent Healing Period

Stenting has become an important adjunctive tool for assisting coil embolization in complex-shaped intracranial aneurysms. However, as a secondary effect, stent deployment has been related to both immediate and delayed remodeling of the local vasculature. Recent studies have demonstrated that this phenomenon may assume different roles depending on the treatment stage. However, the extent of such event on the intra-aneurysmal hemodynamics is still unclear; especially when performing two-step stent-assisted coiling (SAC). Therefore, we performed computational fluid dynamics (CFD) analysis of the blood flow in four bifurcation aneurysms focusing on the stent healing period found in SAC as a two-step maneuver. Our results show that by changing the local vasculature, the intra-aneurysmal hemodynamics changes considerably. However, even though changes do occur, they were not consistent among the cases. Furthermore, by changing the local vasculature not only the shear levels change but also the shear distribution on the aneurysm surface. Additionally, a geometric analysis alone can mislead the estimation of the novel hemodynamic environment after vascular remodeling, especially in the presence of mixing streams. Therefore, although the novel local vasculature might induce an improved hemodynamic environment, it is also plausible to expect that adverse hemodynamic conditions might occur. This could pose a particularly delicate condition since the aneurysm surface remains completely exposed to the novel hemodynamic environment during the stent healing period. Finally, our study emphasizes that vascular remodeling should be considered when assessing the hemodynamics in aneurysms treated with stents, especially when evaluating the earlier stages of the treatment process.

Hemodynamic effects of intracranial aneurysms from stent-induced straightening of parent vessels by stent-assisted coiling embolization

BACKGROUND

Straightening of parent vessels happens for stent-assisted coiling embolization (SACE) treatment of intracranial aneurysms. This study aims to investigate aneurysmal hemodynamic modifications caused by stent-induced vessel straightening.

METHODS

Stent and coil deployments of a SACE-treated distal bifurcation aneurysm by finite element method were performed first with the preoperative (not straightened, NS) and postoperative (straightened, S) vessel models respectively. Computational fluid dynamics were then performed for eight models, including (I) NS only model, (II) NS+stent model, (III) NS+coils model, (IV) NS+stent+coils model, (V) S only model, (VI) S+stent model, (VII) S+coils model, and (VIII) S+stent+coils model. Finally, changes in aneurysmal flow velocity, isovelocity surface and wall shear stress (WSS) were analyzed qualitatively and quantitatively.

RESULTS

The flow was less in the S models than that in the corresponding NS models. Coils blocked most of the flow into the aneurysm sac in both NS models and S models and vessel straightening had more profound effect on the high aneurysmal flow volume reduction than coiling, while stenting generated adverse effect on flow reduction. Taking the NS only model as baseline (100%), the sac-averaged velocities of models II to VIII were 112%, 36%, 42%, 45%, 39%, 12%, 13%, and high flow volumes were 119%, 21%, 30%, 10%, 8%, 3%, 3%, while the sac-averaged WSSs were 106%, 37%, 44%, 41%, 35%, 17% and 24%, respectively.

CONCLUSIONS

Stent-induced vessel straightening combined coil embolization has the best performance in hemodynamic modifications and may reduce the recurrence rate, whereas stenting may generate adverse effect on hemodynamic alterations.

Staged Approach for Stent-Assisted Coiling of Cerebral Aneurysms after Failure of Initial Intra-Saccular Catheterization

Purpose

Microcatheter navigation into an aneurysm sac can present difficulties through negative interactions between the deployed stent mesh and microcatheter. We hypothesized that endothelialization of the stent mesh would minimize these interactions. We aimed to assess the feasibility of staged coiling after stenting by reviewing our experiences with unavoidably staged embolization cases.

Materials and Methods

Between 2011 and 2019, 7 patients (mean age 57.2 years, range 49–76 years) including 5 females, experienced 9 unruptured aneurysms treated with staged stenting and coiling due to unstable microcatheter navigation into the aneurysm after stent placement. The aneurysms were in the paraclinoid internal carotid artery (ICA) (n=3), ophthalmic origin ICA (n=1), superior cerebellar artery origin (n=2), basilar tip (n=2), and the middle cerebral artery bifurcation (n=1). The stents used were the Neuroform Atlas (n=4), Neuroform EZ (n=2), and Low-profile Visualized Intraluminal Support Blue (n=1).

Results

The mean interval between stenting and coiling was 15 weeks (range, 12–21 weeks). The average navigation time between the first roadmap imaging and microcatheter insertion in the sac was 14 minutes (range, 8–20 minutes). One aneurysm was occluded without further coiling on follow-up. Staged coiling successfully treated the remaining aneurysms (n=8). No complications were identified.

Conclusion

In cases of difficult intra-saccular catheterization, intentional staged coiling may be a feasible option for stent-assisted coiling of the cerebral aneurysms.

Endovascular Treatment of Ruptured Wide-Necked Anterior Communicating Artery Aneurysms Using a Low-Profile Visualized Intraluminal Support (LVIS) Device

Objective: To evaluate the safety and efficacy of low-profile visualized intraluminal support (LVIS) stent-assisted coiling for the treatment of ruptured wide-necked anterior communicating artery (ACoA) aneurysms.

Methods: The clinical and angiographic data of 31 acutely ruptured wide-necked ACoA aneurysms treated with LVIS stent-assisted coiling between January 2014 and December 2018 were retrospectively reviewed.

Results: All stents were successfully deployed. The immediate angiographic results were modified Raymond-Roy class I in 27 cases, modified Raymond-Roy class II in 2 cases, and modified Raymond-Roy class IIIa in 2 cases. Intraoperative thrombosis and postoperative aneurysmal rebleeding occurred in one case each. Two patients (6.5%) who were admitted due to poor clinical grade conditions died during hospital admission as a result of initial bleeding. Angiographic follow-up (mean: 12.9 months) was performed for 26 patients, the results of which demonstrated that 25 aneurysms were completely occluded and one was class II. The last clinical follow-up (mean: 25.3 months) outcomes demonstrated that 27 patients had favorable clinical outcomes and two had poor clinical outcomes.

Conclusion: LVIS stent-assisted coiling for ruptured wide-necked ACoA aneurysms was safe and effective, with a relatively low rate of perioperative complications and a high rate of complete occlusion at follow-up.

Factors Affecting the Degree of Angular Remodeling in Stent-Assisted Coiling of Bifurcation Aneurysms

Background

Stent-assisted coiling (SAC) leads to significant changes in the vascular angle altering the bifurcation geometry and the hemodynamics at the bifurcation apex. It is believed that the stent alone exerts this effect, but other possible factors have not been studied.

Purpose

To study the factors contributing to angular remodeling following SAC of bifurcation aneurysms including the anatomical, stent-related, and coil-related factors.

Materials and Methods

We reviewed 43 basilar and carotid bifurcation aneurysms treated by SAC using Neuroform EZ (n = 28), Enterprise (n = 8), and Lvis Jr. (n = 7) stents. The bifurcation angle between the mother and stented daughter vessel was measured in 4 settings: pretreatment, poststenting, postcoiling, and at delayed follow-up (6-12 months). The degree of stent-induced angular remodeling was calculated by subtracting the poststenting bifurcation angle from the pretreatment one, while the coil-induced angular remodeling was calculated as the difference between the postcoiling and poststenting bifurcation angle. The immediate postprocedural degree of angular remodeling is the sum of the stent- and coil-induced angular remodeling. We studied the effect of several factors including the pretreatment bifurcation angle, aneurysm site, diameter of parent vessel, stent type, stent length in the daughter vessel, postoperative actual in situ coil size, and packing density.

Results

The mean degree of stent-induced and coil-induced angular remodeling was 10.2 (0-47) and 4.53 (-7 to 30), respectively. The immediate postprocedural and delayed angular remodeling was 14.8 (-4 to 47) and 4.75 (-12 to 40), respectively. The degree of immediate remodeling was significantly affected by the actual in situ coil size (p = 0.017), and the pretreatment bifurcation angle (p = 0.024). Linear regression was carried out and the pretreatment bifurcation angle was defined as a predictor. The degree of delayed remodeling is significantly affected only by the pretreatment bifurcation angle (p = 0.011).

Conclusion

Immediate angular remodeling following SAC of bifurcation aneurysms can happen after stenting or coiling or both. This is the first study reporting the role of the coils as an additional factor beside the stent in inducing immediate angular changes; this effect is correlated to the size of the coils. The pretreatment bifurcation angle is the most consistent factor affecting the degree of both immediate and delayed angular remodeling.

Effect of Straightening the Parent Vessels in Stent-Assisted Coil Embolization for Anterior Communicating Artery Aneurysms

BACKGROUND

Stent-assisted coil embolization (SAC) for treating anterior communicating artery (AcomA) aneurysms is safe and effective. Straightening of parent vessels by stent placement can lead to progressive thrombosis. We describe our experience with SAC for AcomA aneurysms and demonstrate the effect of straightening the parent vessels.

METHODS

A total of 26 patients with AcomA aneurysms were treated using SAC in our institute between July 2010 and December 2017. Follow-up digital subtraction angiography was performed 6 months after treatment, magnetic resonance angiography was performed every year, and outcomes were analyzed.

RESULTS

From all aneurysms (n = 24), 12 (50.0%) were neck remnant, and 12 (50.0%) were dome-filling types immediately after the procedure. At the 6-month digital subtraction angiography follow-up (n = 22), 13 (59.1%) aneurysms were complete obliteration, 8 (36.4%) were neck remnant, and 1 (4.5%) was dome filling. The median parent vessel angle was measured preoperatively at 98.1°, increased to 124.8° immediately after stent deployment, and further increased to 149.6° at the 6-month follow-up. Progressive thrombosis was observed in 13 of 22 (59.1%) aneurysms. The parent vessel angle change immediately after stent deployment in the progressive thrombosis group tended to be larger than that observed in the no thrombosis group; this change was significant at the 6-month follow-up. The median follow-up term was 18 months. No patients required retreatment.

CONCLUSIONS

Good SAC outcomes were achieved for AcomA aneurysms, and hemodynamic changes related to straightening of the parent vessels is a consideration in SAC.

Angiographic and clinical results of anterior communicating artery aneurysm endovascular treatment

Introduction

The anterior communicating artery (ACoA) is the most common location of intracranial aneurysms, observed in 35% of cases. Endovascular treatment has become an alternative to surgical clipping and the primary method of choice.

Aim

To assess the treatment results of ruptured and unruptured ACoA aneurysms and to assess the incidence of intraprocedural complications and various factors influencing these aspects.

Material and methods

One hundred and eleven embolizations of ACoA aneurysms (80.7% ruptured and 19.3% unruptured) were retrospectively analysed. The methods of embolization were: coiling, balloon-assisted coiling, stent-assisted coiling. Morphology and dimensions of aneurysms were assessed on 3D digital subtraction angiography (DSA) images. Medical records were analysed for patient’s clinical status at admission, intraprocedural complications, follow-up examination and modified Rankin Scale (mRS) score 1 month after discharge.

Results

Immediately after the procedure 56.9% of patients had Raymond-Roy Occlusion Classification (RROC) class I, 37.6% class II and 5.5% class III. The overall intraprocedural complication rate was 6.6%. There were significantly more cases of bleeding (p = 0.012) and coil prolapse (p = 0.012) during the procedures ending with higher packing density. Twenty-eight (25.7%) patients died during hospital stay, 27 (96.4%) with ruptured aneurysm. In the follow-up of 41 patients, RROC was the same or improved in 73.2% of cases and recanalization occurred in 26.8%. Six patients with aneurysm recanalization underwent repeat embolization.

Conclusions

Endovascular embolization of ACoA aneurysms is an effective and safe treatment method. The most powerful factor influencing the incidence of complications is packing density. Superior orientation of the dome, initial incomplete embolization and poor outcome in mRS scale are factors predisposing to ACoA aneurysm recurrence.

Selective Temporary Stent-Assisted Coil Embolization for Intracranial Wide-Necked Small Aneurysms Using Solitaire AB Retrievable Stent

Objective

Stent-assisted coil embolization of intracranial wide-necked aneurysm requires long-term postoperative antiplatelet therapy to prevent in-stent thrombosis. This study aimed to demonstrate results of temporary stent placement for coiling wide necked small intracranial aneurysms, which eliminated need for antiplatelet agents, and to discuss its feasibility and safety.

Methods

Data of 156 patients who underwent stent-assisted coil embolization between 2011 and 2014 were retrospectively analyzed. Thirteen cases of temporary stent-assisted coil embolization were included, and their clinical and radiological results were evaluated.

Results

The aneurysms treated were all unruptured except one case. All of them had wide neck with mean dome-to-neck ratio of 0.96 and were small-sized aneurysms with mean maximal diameter of 4.2 mm. There was no technical failure in retrieval of stent after completion of embolization of the target aneurysm. Immediate angiography revealed 11 complete and two partial embolization (one residual neck and one residual aneurysm). Two cases encountered thrombosis complication, and they were managed without neurological sequelae. The mean follow-up period was 43 months, angiographic follow-up revealed two cases with minor recurrence, and clinical outcome was good with modified Rankin scale score of 0.

Conclusion

Temporary stent-assisted coil embolization of small wide-necked intracranial aneurysm using fully retrievable stent appears safe and effective. Further application and evaluation of this technique in more cases with larger size aneurysm is warranted.

Endovascular stent-induced alterations in host artery mechanical environments and their roles in stent restenosis and late thrombosis

Cardiovascular stent restenosis remains a major challenge in interventional treatment of cardiovascular occlusive disease. Although the changes in arterial mechanical environment due to stent implantation are the main causes of the initiation of restenosis and thrombosis, the mechanisms that cause this initiation are still not fully understood. In this article, we reviewed the studies on the issue of stent-induced alterations in arterial mechanical environment and discussed their roles in stent restenosis and late thrombosis from three aspects: (i) the interaction of the stent with host blood vessel, involve the response of vascular wall, the mechanism of mechanical signal transmission, the process of re-endothelialization and late thrombosis; (ii) the changes of hemodynamics in the lumen of the vascular segment and (iii) the changes of mechanical microenvironment within the vascular segment wall due to stent implantation. This review has summarized and analyzed current work in order to better solve the two main problems after stent implantation, namely in stent restenosis and late thrombosis, meanwhile propose the deficiencies of current work for future reference.

Stent-assisted coiling of cerebral aneurysms with the Neuroform Atlas stent

Objectives The Neuroform Atlas stent (AS) is the smallest intracranial stent with an open-cell design. This study reports the first clinical experience with AS. Methods All intracranial aneurysms treated by stent-assisted coiling using a single AS in a single institution were retrospectively evaluated. Patient demographics, aneurysm characteristics, angles between the parent artery and stented branch, technical success, and clinical and angiographic follow-up were analyzed. Results Fifty-five consecutive aneurysms treated with AS-assisted coiling were included. Of these, 69.1% were located distal to the circle of Willis. Technical success rate was 100%. The mean diameters of proximal and distal parent arteries were 2.62 mm (range 1.5-4.4) and 1.8 mm (range 0.8-3.5), respectively. Except for a minor stroke in a patient who completely discontinued antiplatelet therapy on postoperative day 4, there were no clinical events with permanent sequelae, and 94.1% of patients had Raymond-Roy score of 1 or 2 aneurysmal occlusion at a mean follow-up duration of 7.9 months. Although the angle between the parent artery and the stented branch increased significantly ( p < 0.001) with time, the angular change at follow-up was only 16.45 ± 11.03 degrees and was inversely correlated both with preoperative angle and the diameter of the distal parent artery ( r = -0.465 and r = -0.433, respectively, p = 0.004 for both). Conclusion AS-assisted coiling was associated with a favorable early clinical outcome and angiographic results in this series. This stent can be used for distally located aneurysms and results in minimal alteration of the arterial anatomy.

Contribution of the straightening effect of the parent artery to decreased recanalization in stent-assisted coiling of large aneurysms

OBJECTIVE The durability of embolization of large aneurysms is enhanced by use of the neck-bridging stent. However, it remains unclear what factors contribute to decreased recanalization. The purpose of this study was to demonstrate the contribution of the straightening effect of the parent artery to the durability of stent-assisted coiling for large aneurysms. METHODS Of the 182 aneurysms treated by embolization since the introduction of the neurovascular stent, 82 consecutive unruptured aneurysms with a diameter greater than 7 mm were selected. There were 52 aneurysms treated with a stent (Group S) and 30 treated without a stent (Group NS). Occlusion status was evaluated 12 months after embolization with digital subtraction angiography. The vascular angle of the parent artery was measured before, immediately after, and 12 months after embolization. The rates of recanalization were compared between Group S and Group NS. In Group S, the rates of recanalization were further compared between those aneurysms with and without a significant angle change. RESULTS The rate of major recanalization was 9.6% in Group S and 26.7% in Group NS. The volume embolization ratio was 32.6% in Group S and 31.6% in Group NS, with no statistically significant difference. However, the angulation change before and after coiling was significantly higher in Group S (10.6°) than in Group NS (0.9°). The difference in the angulation was more evident 12 months after coiling (19.1° in Group S and 1.5° in Group NS). In Group S, recanalization was found in 14.3% of 35 stented aneurysms without a significant angular change when a significant angular change was defined as more than 20°. In contrast, all 17 aneurysms with ≥ 20° of angular change remained occluded. CONCLUSIONS Significant angular change of ≥ 20° most likely leads to decreased recanalization following stent-assisted embolization of large aneurysms.

Reconstructive endovascular treatment of vertebral artery dissecting aneurysms with the Low-profile Visualized Intraluminal Support (LVIS) device

Introduction

The Low-profile Visualized Intraluminal Support (LVIS) device is a new generation of self-expanding braided stent recently introduced in China for stent assisted coiling of intracranial aneurysms. The aim of our study is to evaluate the feasibility, safety, and efficacy of the LVIS device in reconstructive treatment of vertebral artery dissecting aneurysms (VADAs).

Methods

We retrospectively reviewed the neurointerventional database of our institution from June 2014 to May 2016. Patients who underwent endovascular treatment of VADAs with LVIS stents were included in this study. Clinical presentation, aneurysmal characteristics, technical feasibility, procedural complications, and angiographic and clinical follow-up results were evaluated.

Results

38 patients with VADAs who underwent treatment with LVIS stent were identified, including 3 ruptured VADAs. All VADAs were successfully treated with reconstructive techniques including the stent-assisted coiling (n = 34) and stenting only (n = 4). Post-procedural complications developed in 3 patients (7.9%) including two small brainstem infarctions and one delayed thromboembolic event. Complications resulted in one case of minor permanent morbidity (2.6%). There was no procedure-related mortality. The follow-up angiogram was available in 30 patients at an average of 8.3 months (range, 2 to 30 months), which revealed complete occlusion in 23 patients (76.7%), residual neck in five patients (16.7%), and residual sac in two patients (6.7%). The follow-up of 25 aneurysms with incomplete immediate occlusion revealed 22 aneurysms (88%) with improvement in the Raymond class. One aneurysm (3.3%) showed recanalization and required retreatment. Clinical followed-up at 5–28 months (mean 14.1 months) was achieved in 36 patients because two patients died of pancreatic cancer and basal ganglia hemorrhage, respectively. No new neurologic deterioration or aneurysm (re)bleeding was observed.

Conclusions

Our preliminary experience with reconstruction of VADAs with the LVIS device demonstrates that this treatment approach is feasible with good short-term angiographic and clinical outcomes. Long-term and larger cohort studies are necessary to determine long-term outcomes of this therapy.

The Use of Single Stent-Assisted Coiling in Treatment of Bifurcation Aneurysms: A Multicenter Cohort Study With Proposal of a Scoring System to Predict Complete Occlusion

BACKGROUND

The development of stent-assisted coiling has allowed for the endovascular treatment of wide-necked bifurcation aneurysms. A variety of options exist, and little is known about the optimal stent configuration in this setting. We report a large multicenter experience of stent-assisted coiling of bifurcations aneurysms using a single stent, with attention to factors predisposing to aneurysm recanalization.

OBJECTIVE

To assess the safety and efficacy of single stent-assisted coiling, in addition to analyzing the factors associated with recanalization, and proposal of a predictive scoring scale.

METHODS

A multicenter retrospective analysis of bifurcation aneurysms treated with a single stent-assisted coiling technique between 2007 and 2015 was performed. Clinical and radiographic data were collected and used to develop a scoring system to predict aneurysm occlusion.

RESULTS

A total of 74 bifurcation aneurysms were treated with single stent-assisted coiling. At a median follow-up of 15.2 mo, complete occlusion or remnant neck was achieved in 90.6% of aneurysms. Aneurysm location, maximal diameter, neck size, and alpha angle were predictive of aneurysm occlusion at last follow-up. A scoring system to predict complete occlusion based on these factors was developed. An increasing score correlated with a higher rate of complete occlusion.

CONCLUSION

The treatment of bifurcation aneurysm using single stent technique for stent-assisted coiling is safe and effective. Complete occlusion or remnant neck occlusion was achieved in 90.6% of cases. Class III aneurysms can be effectively treated using a single stent, while class I may require Y-stent technique.

Proposed Parent Vessel Geometry Based Classification of Anterior Communicating Artery-Located Aneurysms

BACKGROUND AND OBJECTIVES

The present study is focused on correlation of parent vessels and neck diameters with anterior communicating artery (AComA) aneurysmal depth and growth direction. The study principally aims to suggest a new classification of AComA-located aneurysms based on the physical characteristics of parent vessels.

METHODS

A retrospective analysis was performed of 155 patients with ruptured AComA-located aneurysms. The percentage of difference between both A1 arteries was measured on computed tomography angiography images and neck locations were determined. Accordingly, AComA-located aneurysms were classified into 2 groups. In both groups, A1 and A2 arteries and neck size diameters were measured and their relation with aneurysmal depth was studied. The aspect ratio was calculated.

RESULTS

Eleven patients in which the aneurysm neck originates from the AComA proper with almost equal A1s were classified as the true AComA aneurysm group whereas 144 patients in whom the aneurysm neck originates at the dominant A1 bifurcation into the AComA and A2 with the average difference between both A1s of about 84.44% were classified as the dominant A1-bifurcation group. There is significant correlation between aneurysmal depth and neck diameter in both groups (P ≤ 0.05, P < 0.001). The aspect ratio was calculated as equal to 1.166.

CONCLUSIONS

The dominant A1 bifurcation type is the most common type of AComA-located aneurysm. The present classification provides clinical value in understanding how AComA aneurysms grow and behave. It helps to understand the geometry of multilobulated aneurysms such as ruptured blebs locations during treatment procedures respecting the direction of the dominant A1 axis in group II. Multiple anatomic variations of this complex AComA area can clarify future subtypes of these 2 groups. Thus, further investigation of more patients is needed.

Modification of cerebral vascular anatomy induced by Leo stent placement depending on the site of stenting: A series of 102 cases

BACKGROUND AND PURPOSE

Recent studies demonstrated the capacity of stents to modify cerebral vascular anatomy. This study evaluates arterial anatomy deformation after Leo stent placement according to the stenting site and the impact on the immediate postoperative and six-month degree of aneurysmal occlusion.

MATERIALS AND METHODS

A total of 102 stents were placed against the neck of aneurysms situated in the anterior cerebral circulation. Aneurysms were classified into two groups: The first was called the distal group (n = 62) and comprised aneurysms situated in the middle cerebral and anterior communicating arteries and the second was called the proximal group (n = 40) and comprised aneurysms in other sites. The stented arterial segment was classified as deformed or non-deformed by blinded review and superimposition of anonymised films before and after stenting. The degree of occlusion was determined immediately postoperatively and at six months.

RESULTS

Significantly, anatomical deformity was observed in the distal group compared to the proximal group (85% vs 28%). No significant difference was observed between the two groups in terms of postoperative degree of occlusion. At six months, a significant difference was observed between the two groups: three recurrences in the distal group vs 10 recurrences in the proximal group. Two (3%) recurrences were observed in the deformed group vs 11 (31%) recurrences in the non-deformed group.

CONCLUSIONS

Arterial deformity induced by stenting is even more marked for distal aneurysms. The recurrence rate is smaller when the stent placement results in an arterial anatomical change. The percentage of recurrence is lower when anatomy was amended by stent implantation.

Closed-Cell Stent-Assisted Coiling of Intracranial Aneurysms: Evaluation of Changes in Vascular Geometry Using Digital Subtraction Angiography

Background

Stent-assisted coil embolization (SACE) plays an important role in the treatment of intracranial aneurysms. The purpose of this study was to investigate geometrical changes caused by closed-cell design stents in bifurcation and sidewall aneurysms.

Methods

31 patients with 34 aneurysms underwent SACE with closed-cell design stents. Inflow angle α, determined by aneurysm neck and afferent vessel, and angle between afferent and efferent vessel close to (δ₁), respectively, more remote from the aneurysm neck (δ₂) were graphically determined in 2D angiography projections.

Results

Stent assisted coiling resulted in a significant increase of all three angles from a mean value (±SEM) of α = 119° (±6.5°) pretreatment to 130° (±6.6°) posttreatment (P ≤ .001), δ₁ = 129° (±6.4°) to 139° (±6.1°), (P ≤ .001) and δ₂ = 115° (±8.4°) to 126° (±7.5°), (P ≤ .01). Angular change of δ₁ in AcomA aneurysms was significant greater compared to sidewall aneurysms (26°±4.9° versus 8°± 2.3°, P ≤ .05). The initial angle of δ₁ and δ₂ revealed a significantly inverse relationship to the angle increase (δ₁: r = -0.41, P ≤ .05 and δ₂: r = -0.47, P ≤ .01). Moreover, angle δ₁ was significantly higher in unruptured compared to ruptured aneurysms (135°±7.1° versus 103°±10.8°, P ≤ .05).

Conclusion

Stent deployment modulates the geometry of the aneurysm-vessel complex, which may lead to favorable hemodynamic changes more similar to unruptured than to ruptured aneurysms. Our findings also suggest that the more acute-angled aneurysm-vessel anatomy, the larger the angular change. Further studies are needed to investigate whether these changes improve the clinical outcome.

The safety and efficacy of low profile visualized intraluminal support (LVIS) stents in assisting coil embolization of intracranial saccular aneurysms: a single center experience

BACKGROUND

The low profile visualized intraluminal support (LVIS) device is a new generation of self-expanding braided stents recently introduced into China for stent assisted coiling of intracranial aneurysms. This study assessed the clinical safety and efficacy of the LVIS stent for embolization of intracranial saccular aneurysms.

METHODS

Patients with intracranial saccular aneurysms treated using the LVIS device in our center between April 2014 and December 2014 were reviewed. The primary outcomes were procedural safety, target aneurysm recurrence, and mid-term follow-up of clinical and angiographic outcomes.

RESULTS

97 patients with intracranial saccular aneurysms were treated using the LVIS stent, with 100% technical success rate. No mortality was observed. One patient had transient deficit (1/97, 1.0%). Immediate angiographic outcome evaluation showed complete occlusion in 28 (28.8%) and neck remnant in 39 (40.2%) of the 97 patients, respectively. Of the 76 (78.35%) patients who underwent angiographic follow-up at a mean of 8.1 months, complete occlusion was achieved in 64 (84.2%) patients. In the remaining patients, neck remnant in nine (11.8%) and residual sac in three (4%) patients were observed. None of the patients had any target aneurysm recurrence, and the mortality rate was 0%.

CONCLUSIONS

The LVIS stent is safe and effective in the treatment of intracranial saccular aneurysms.

Do Contrast-Fill Patterns Immediately After Coil Embolization of Small Saccular Aneurysms Impact Long-Term Results?

PURPOSE

It is generally accepted that filling of a saccular aneurysm with contrast immediately after coil embolization predisposes to later recanalization. However, not all such scenarios evolve similarly over time. We investigated outcomes of small (≤ 7 mm) aneurysms with contrast-filled sacs immediately after coil embolization, evaluating the impact of pattern and degree of filling on subsequent recanalization.

METHODS

Between January, 2008 and December, 2010, 186 small (≤ 7 mm) saccular aneurysms that retained contrast after coil embolization accrued for this study. Lesions were categorized by pattern (eccentric vs. concentric) and degree of filling on working projections. Clinical and morphologic factors were also analyzed to assess impact on subsequent recanalization. Morphologic outcomes at 6 months or more were assessed.

RESULTS

In 93.5 % (174/186) of aneurysms with visible contrast retention, complete occlusion was evident on follow-up imaging studies at 6 months. Multiple logistic regression analysis indicated that eccentric (vs. concentric) contrast filling carried greater risk of subsequent recanalization (p = 0.020). Stent placement and progressive occlusion were also linked, falling short of statistical significance (p = 0.089). Of 166 progressively occluded aneurysms followed for more than 12 months (mean, 30.8 ± 7.3 months), 158 (95.2 %) exhibited stable occlusion.

CONCLUSION

Small (≤ 7 mm) aneurysms that retain contrast immediately after coil embolization are more likely to become completely occluded over time through progressive thrombosis. However, an eccentric fill pattern may predispose to recanalization.

Endovascular treatment of wide-neck anterior communicating artery aneurysms using the LVIS Junior stent

We performed this retrospective study to assess the clinical safety and efficacy of the low-profile visualized intraluminal support junior (LVIS Jr.; MicroVention, Aliso Viejo, CA, USA) stent placement in anterior communicating artery (ACA) aneurysms. ACA aneurysms are some of the most common intracranial aneurysms. Stent placement is particularly difficult due to the complexity of the vascular anatomy and the small vessels of the ACA complex. From November 2013 and June 2014, LVIS Jr. stent-assisted coiling was performed in 11 patients with 12 wide-neck ACA aneurysms. Patient demographics, morphologic features of the aneurysm, clinical results and follow-up results are presented. Successful deployment of the LVIS Jr. stent in the targeted artery was achieved in all patients. Complete occlusion was achieved in seven patients, neck remnant in three, and partial occlusion in two. The angiographic follow-up of nine patients (mean 4.4 months) showed that all aneurysms remained stable or improved. There was no in-stent stenosis, recurrence or retreatment. The modified Rankin scale score at discharge was 0 in eight patients and 1 in three patients. The LVIS Jr. stent provided excellent trackability and deliverability and is safe and effective for the treatment of wide-necked ACA aneurysms. Further follow-up is needed to assess the long-term efficacy of LVIS Jr. stent placement in ACA.

Stability of Cerebral Aneurysms After Stent-Assisted Coil Embolization

BACKGROUND:

The availability of stents has widened the indications of endovascular intervention for cerebral aneurysms.

OBJECTIVE:

To elucidate the effect of stents on radiologic outcomes and to analyze the risk factors for aneurysmal recanalization via propensity score matching.

METHODS:

From the 735 aneurysms treated with coil embolization with stents (n = 187) and without stents (n = 548) between 2009 and 2011, 157 propensity score-matched case pairs were selected. The recanalization rates and relevant risk factors were analyzed. The mean follow-up interval was 24.1 ± 11.3 months (range, 6-48 months) and 22.9 ± 11.4 months (range, 6-56 months) in the stent and nonstent groups, respectively (P = .388).

RESULTS:

The stent group demonstrated lower recanalization rates than the nonstent group during both the 6-month (1.9% vs 10.2%, P = .004) and the final follow-up periods (8.3% vs 18.5%, P = .005). The multivariate analysis identified the following significant factors for recanalization: the use of stents (hazard ratio, 0.40; 95% confidence interval, 0.21-0.76, P = .005), larger aneurysm size (hazard ratio, 1.21; 95% confidence interval, 1.11-1.31, P &lt; .001), and initially incomplete occlusion (hazard ratio, 2.39; 95% confidence interval, 1.28-4.43, P = .006). The incidence of permanent neurological complication tended to be higher in the stent group than in the nonstent group (3.2% vs 0%, P = .063).

CONCLUSION:

In this propensity score-matched analysis, stent implantation reduced the overall recanalization of the coiled cerebral aneurysms. However, the use of stents should be carefully decided upon.

Effect of clipping anterior communicating artery aneurysms via pterional approach contralateral to supply of dominant blood: report of 15 patients

BACKGROUND AND PURPOSE

Anterior communicating artery aneurysm (ACoAA) is a common cerebrovascular disease. This research is to observe the curative effect and safety of clipping anterior communicating artery (ACoA) aneurysms by microsurgery through the pterional approach contralateral to supply of dominant blood.

MATERIALS AND METHODS

Before the surgery, three-dimensional-DSA (3D-DSA) was performed to study the regional anatomy of ACoA complexes in all 15 patients with ACoA aneurysms. According to 3D-DSA, the aneurysms and ACoA complexes could be satisfactorily exposed by the microsurgery through the pterional approach contralateral to the supply of dominant blood. And then the microsurgery through the pterional approach contralateral to the supply of dominant blood was performed in 15 patients with ACoA aneurysms.

RESULTS

Clipping of ACoA aneurysms were successfully performed in all patients. The aneurysms and ACoA complexes were satisfactorily exposed via 3D-DSA. Among 15 patients with ACoA aneurysms, 14 cases were cured and 1 case need further care.

CONCLUSIONS

The ideal side of pterional approach may be cheese via simulation of pterional approach with 3D-DSA. The ACoA complex and aneurysm can be clearly exposed, and the aneurysm may be smoothly clipped safely by the microsurgery through the ideal side pterional approach contralateral to supply of dominant blood in the patients with ACoA aneurysms.

Preliminary experience with self-expanding closed-cell stent placement in small arteries less than 2 mm in diameter for the treatment of intracranial aneurysms

OBJECT

The purpose of this study was to report the authors' preliminary experience using self-expanding closed-cell stents deployed in small arteries (< 2 mm in diameter) to treat intracranial aneurysms.

METHODS

A total of 31 patients were studied. All subjects met the following criteria: 1) they received an Enterprise stent for treatment of a wide-necked aneurysm or a dissecting aneurysm or as part of a stent-salvage procedure; and 2) they had an Enterprise stent deployed in a small parent artery (< 2 mm in diameter) that had no atherosclerotic stenosis. Procedure-related complications and follow-up sizes of the parent arteries were evaluated for safety and patency.

RESULTS

There were 16 ruptured aneurysms and 15 unruptured aneurysms. Three (9.7%) of the 31 patients experienced procedure-related complications, and they all were asymptomatic. Follow-up angiography was performed in 27 patients (87.1%) (at a mean 15.5 months after surgery). Parent arteries with 2 acute angles (n = 4) were occluded in 3 cases (75.0%), and those with no acute angles (n = 13) or 1 acute angle (n = 6) showed 100% patency on follow-up angiography. There was a significant difference between the follow-up sizes (mean 1.72 ± 0.30 mm) of parent arteries and their sizes (mean 1.59 ± 0.26 mm) before treatment (95% CI - 0.254 to - 0.009 mm; p = 0.037, paired-samples t-test).

CONCLUSIONS

In the current series the deployment of self-expanding closed-cell stents in small arteries was safe and resulted in good patency, especially when the stents were deployed in segments of the parent artery with no acute angles or only 1 acute angle.

Personalizing flow-diverter intervention for cerebral aneurysms: from computational hemodynamics to biochemical modeling

This paper presents the computational modeling of a variety of flow-diverting stents, deployed in a number of patient-specific aneurysm geometries. We consider virtual device deployment and hemodynamics as well as thrombus formation, with the scope to assess pre-operatively the efficacy of specific devices in treating particular aneurysms. An algorithm based on a linear and torsional spring analogy is developed for the fast virtual deployment of stents and similar minimally invasive devices in patient-specific vessel geometries. The virtual deployment algorithm is used to accurately deploy a total of four stent designs in three aneurysm geometries. A variety of different flow-diverting stent designs, representing the commercially available and the entirely novel, are presented, varying in both mesh design and porosity. Transient computational hemodynamics simulations are performed on multiple patient-specific geometries to predict the reduction in aneurysm inflow after the deployment of each device. Further, a thrombosis initiation and growth model is implemented, coupled with the hemodynamic computations. Hemodynamic simulations show large variations in flow reduction between devices and across different aneurysm geometries. The industry standard of flow-diverters with 70% porosity, assumed to offer the best compromise in flexibility and flow reduction, is challenged in at least one aneurysm geometry.

Flow visualization of recurrent aneurysms after coil embolization by 3D phase-contrast MRI

BACKGROUND

Flow patterns in cerebral aneurysms are clinically important. Information on inflow patterns into aneurysms is especially helpful in preventing a recurrence after coil embolization. Computational fluid dynamics (CFD) simulations of patient-specific cerebral aneurysms are feasible and provide information on flow patterns. However, flow visualization by CFD simulations is challenging for recurrent aneurysms after coil embolization because coils make it difficult to obtain precise geometry of the recurrent aneurysms. In this study, we assessed the feasibility of flow visualization of recurrent aneurysms using 3D phase-contrast magnetic resonance imaging (PC-MRI).

METHOD

Time-of-flight magnetic resonance angiography and 3D PC-MRI were performed in eight cases of recurrent aneurysms after coil embolization. We attempted to visualize flow inside the aneurysms using data of 3D PC-MRI and evaluated the visualization. Additionally, CFD simulations were performed in a single case.

RESULTS

Inflow into aneurysms was visualized in all eight cases (100%). Flow patterns inside aneurysms were visualized in six cases (75%), and these were associated with a large size of recurrent aneurysms (mean size, 10.3 mm for visualized cases vs. 4.8 mm for unvisualized cases; p = 0.046, Mann-Whitney test). Flow patterns were similar between PC-MRI and CFD simulations. PC-MRI was faster and easier for observing inflow patterns than CFD simulations.

CONCLUSIONS

This is the first study to demonstrate that flow visualization of recurrent aneurysms by 3D PC-MRI is feasible. This technique may be more practical and easier than CFD simulations, and may provide clinically helpful information.

Hemodynamic effects of stent struts versus straightening of vessels in stent-assisted coil embolization for sidewall cerebral aneurysms

Background

Recent clinical studies have shown that recanalization rates are lower in stent-assisted coil embolization than in coiling alone in the treatment of cerebral aneurysms.

Objective

This study aimed to assess and compare the hemodynamic effect of stent struts and straightening of vessels by stent placement on reducing flow velocity in sidewall aneurysms, with the goal of reducing recanalization rates.

Methods

We evaluated 16 sidewall aneurysms treated with Enterprise stents. We performed computational fluid dynamics simulations using patient-specific geometries before and after treatment, with or without stent struts.

Results

Stent placement straightened vessels by a mean (±standard deviation) of 12.9°±13.1° 6 months after treatment. Placement of stent struts in the initial vessel geometries reduced flow velocity in aneurysms by 23.1%±6.3%. Straightening of vessels without stent struts reduced flow velocity by 9.6%±12.6%. Stent struts had significantly stronger effects on reducing flow velocity than straightening (P = 0.004, Wilcoxon test). Deviation of the effects was larger by straightening than by stent struts (P = 0.01, F-test). The combination of stent struts and straightening reduced flow velocity by 32.6%±12.2%. There was a trend that larger inflow angles produced a larger reduction in flow velocity by straightening of vessels (P = 0.16).

Conclusion

In sidewall aneurysms, stent struts have stronger effects (approximately 2 times) on reduction in flow velocity than straightening of vessels. Hemodynamic effects by straightening vary in each case and can be predicted by inflow angles of pre-operative vessel geometry. These results may be useful to design a treatment strategy for reducing recanalization rates.

Endovascular treatment of anterior communicating artery aneurysms: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

Endovascular therapy has become an acceptable alternative to traditional clipping for the management of intracranial aneurysms. However, a limited number of studies have examined outcomes and complications specific to embolization of anterior communicating artery aneurysms.

MATERIALS AND METHODS

A systematic review of the literature was conducted with the use of multiple data bases to identify reports on endovascular treatment of anterior communicating artery aneurysms between 1994 and 2012. Angiographic results, clinical outcomes, and complication rates were pooled across studies by using random-effects meta-analysis with subgroup analysis of outcomes by rupture status and time trend stratification.

RESULTS

Fourteen studies, consisting of 1552 treated anterior communicating artery aneurysms, were included in this meta-analysis. The rate of immediate and long-term complete and near-complete angiographic occlusion was 88% (95% CI = 81-93%) and 85% (95% CI = 78-90%), respectively. Intraprocedural rupture rate was 4% (95% CI = 3-6%). The re-bleeding rate was 2% (95% CI = 1-4%) and the retreatment rate was 7% (95% CI = 5-12%). Morbidity or mortality caused by perioperative stroke occurred at a 3% (95% CI = 2-6%) rate. Overall procedure-related morbidity and mortality were 6% (95% CI = 4-8%) and 3% (95% CI = 2-4%), respectively. Outcomes did not differ between ruptured and unruptured aneurysms, nor did outcomes change over time, though these latter subanalyses were relatively underpowered.

CONCLUSIONS

Endovascular therapy for anterior communicating artery aneurysms is associated with a high rate of complete angiographic occlusion. However, the procedure-related permanent morbidity and mortality are not negligible for aneurysms in this location.

Stent placement for complex middle cerebral artery aneurysms

BACKGROUND

To evaluate the safety and effectiveness of stent placement for ruptured or unruptured middle cerebral artery (MCA) aneurysms in a larger number.

METHODS

Between October 2003 and December 2012, data for 70 patients with 72 complex MCA aneurysms treated with stents at our institution were retrospectively collected and analyzed.

RESULTS

Eighty-five stents were successfully deployed in this series. However, failure of followed coiling was encountered in 2 (2.8%) tiny aneurysms of them. Of the 63 aneurysms treated with stent-assisted coiling, complete occlusion was achieved in 22 (34.9%), neck remnant in 15 (23.8%), and residual sac in 26 (36.5%). Of the 9 aneurysms treated with stent alone, the results were contrast stasis in 3 aneurysms and no change in 6. Procedure-related complications occurred in 9 (12.5%) procedures, including 7 of 27 (25.9%) with ruptured aneurysms and 2 of 45 (4.4%) with unruptured aneurysms, which resulted in 1 death and 5 disabilities. Univariate and multivariate analyses show that ruptured aneurysm is an independent factor for the outcome of these patients (odds ratio, 7.35; 95% confidence interval, 1.35-40.0). Angiographic follow-up results (mean, 10.5±8.8 months) showed that 72.1% (44 of 61) were completely occluded, 4.9% (3 of 61) recurred, and others were stable or had improved. Intrastent stenosis was observed in 1 (1.6%) patient, which was managed conservatively. During a clinical follow-up period ranging from 7 to 113 months (mean, 33.0±22.4 months), 1 disabled patient died from severe pneumonia, whereas the clinical status of the others had improved or was stable. Procedure-related morbidity/mortality during the follow-up for the ruptured and unruptured groups were 3.7%/3.7% and 0/0, respectively.

CONCLUSIONS

Our study shows that stent placement for the treatment of certain wide-neck MCA aneurysms is feasible, safe, and effective. However, stent placement for acutely ruptured MCA aneurysms harbors a much higher complication rate.

Balloons and stents in the endovascular treatment of cerebral aneurysms: vascular anatomy remodeled

Wide-neck intracranial aneurysms were originally thought to be either untreatable or very challenging to treat by endovascular means because of the risk of coil protrusion into the parent vessel. The introduction of the balloon remodeling technique (BRT) and later stents specifically designed for intracranial use has progressively allowed these lesions to be endovascularly treated. BRT and stent-assisted coiling technique (SACT) were first designed to treat sidewall aneurysms but, with gained experience and further technical refinement, bifurcation complex-shaped wide-neck aneurysms have been treated by coiling enhanced by BRT and SACT. In this article, we will review and describe the inherent benefits and drawbacks of BRT as well as SACT.

Changes in hemodynamics after placing intracranial stents

Stent-assisted coil embolization has enabled the endovascular treatment of wide-necked cerebral aneurysms. Moreover, recent reports demonstrated that stent-assisted coil embolization was associated with a significant decrease in angiographic recurrences of coiled cerebral aneurysms. One of the possible explanations for this adjunctive effect of stent-assisted coil embolization is changes in the local hemodynamics caused by placing intracranial stents. This study investigated the hemodynamic effect of intracranial stents using computational fluid dynamics (CFD) analysis. The geometry of the intracranial stent, Enterprise(TM) VRD, was acquired by using micro computed tomography and virtually placed across the aneurysm orifice of a saccular aneurysm model (saccular model) and a blister-like aneurysm model (blister-like model) constructed from patient-specific three-dimensional (3D) rotational angiography data. Transient CFD analysis was performed with these models with and without stents. Stent placement induced no significant changes in the 3D streamline in the saccular model and slight changes in the blister-like model. Both saccular and blister-like models with stents had lower wall shear stress (WSS) and flow velocity, and higher oscillatory shear index, WSS gradient, and relative residence time than the equivalent models without stents, indicating the possibility that stent placement induced stagnant and disturbed blood flow. Cross-sectional vector velocity around the stent strut revealed complex blood flow patterns with variable direction and velocity. Although this study was a simulation under limited conditions, similar hemodynamic changes might be induced in the neck remnants treated with stent-assisted coil embolization.

Analysis of complications and recurrences of aneurysm coiling with special emphasis on the stent-assisted technique

BACKGROUND AND PURPOSE

Stent-assisted coiling has expanded the treatment of intracranial aneurysms. With the use of continuously compiled data, we reviewed the role and drawbacks of stent-assisted coiling.

MATERIALS AND METHODS

We compiled data from consecutive patients from 2003-2012 who underwent coiling, with or without stent assistance. Clinical and angiographic results were analyzed retrospectively.

RESULTS

Of 1815 saccular aneurysms in 1505 patients, 323 (17.8%) were treated with stents (299 procedures) and 1492 (82.2%) without stents (1400 procedures). Procedure-related complications occurred in 9.4% with stents versus 5.6% without stents (P = .016, relative risk 1.5; 95% CI, 1.1-2.7). Ischemic complications were more frequent in the stent group than in the no-stent group (7.0% versus 3.5%; P = .005; relative risk, 1.7; 95% CI 1.2-2.5), as were hemorrhagic complications (2.3% versus 1.9%, P = .64). Procedure-induced mortality occurred in 2.7% (8/299) with stents versus 1.1% (15/1400) without stents (P = .029; relative risk, 2.0; 95% CI, 1.1-3.5). Logistic regression analysis identified wide-neck aneurysms as the most significant independent predictor of complications. A total of 64.1% (207/323) of aneurysms treated with stents and 70.3% (1049/1492) treated without stents have been followed, disclosing angiographic recurrence in 15.5% (32/207) versus 35.5% (372/1049), respectively (P < .0001). Logistic regression analysis showed that the presence of a stent was the most important factor for the reduction of angiographic recurrence (P < .0001; relative risk, 2.3; 95% CI, 1.6-3.3).

CONCLUSIONS

The stent-assisted coiling technique is associated with a significant decrease in recurrences but a significant increase in complications. The treatment of wide-neck aneurysms remains hazardous.

Does stent implantation improve the result of repeat embolization in recanalized aneurysms?

BACKGROUND

Although endovascular technique and related devices continue to improve, recanalization of embolized aneurysm remains a pitfall of this approach. The problem of how to treat the recanalized aneurysm needs to be addressed.

OBJECTIVE

To determine the outcomes of patients undergoing repeat embolization for recanalized intracranial aneurysms and to evaluate the impact of stent implantation on subsequent recanalization.

METHODS

Between September 2001 and September 2011, we performed endovascular retreatment in 162 patients with a total of 197 recanalized intracranial aneurysms. Stent implantation was performed in 68 aneurysms during the retreatment. Clinical and morphological outcomes were assessed at 6 months or more after repeat embolization.

RESULTS

Procedure-related complications, including asymptomatic thromboembolism, occurred with 15 aneurysms (7.6%) without permanent neurological sequelae. Follow-up imaging of 172 aneurysms documented stable occlusion in 96 of the lesions (55.8%), minor recanalization in 17 (9.9%), and major recanalization in 59 (34.3%) during the mean follow-up period of 26.0 ± 18.0 months. In multiple logistic regression analysis, stent implantation was shown to reduce the major recanalization rate at 6 months after retreatment (odds ratio: 0.161; 95% confidence interval:, 0.038-0.670; P = .012) and thereafter (odds ratio: 0.226; 95% confidence interval: 0.088-0.581; P = .002).

CONCLUSION

Stent implantation, as well as compact coil packing, at the time of repeat embolization seems beneficial in reducing rates of further recanalization.

Delayed in-stent occlusion due to stent-related changes in vascular geometry after cerebral aneurysm treatment

Stent-assisted coil embolization has been recently accepted as a treatment option for wide-neck or complex cerebral aneurysms. Delayed in-stent occlusion is described due to stent-related changes in vascular geometry. A 66-year-old man underwent stent-assisted coil embolization for an unruptured aneurysm of the vertebral artery. The treatment was successfully performed using the Enterprise stent. Follow-up angiography at 6 months showed asymptomatic in-stent occlusion. Three-dimensional analysis of the vascular geometry revealed that the left vertebral artery was straightened by 40° due to the stent placement. Such straightening of the vessel presumably caused kinking and occlusion of the vessel. Stent-related changes in vascular geometry may cause kinking of a vessel and result in occlusion after the treatment of cerebral aneurysms. Pre-treatment strategy may avoid this risk.