Crescent sign on magnetic resonance angiography revealing incomplete stent apposition: correlation with diffusion-weighted changes in stent-mediated coil embolization of aneurysms

Safety and efficacy of the novel Alpha stent for the treatment of intracranial wide-necked aneurysm

The Alpha stent is an intracranial closed-cell stent with a unique mesh design to enhance wall apposition. It recently underwent structural modifications to facilitate easier stent deployment. This study aimed to evaluate the safety and efficacy of stent-assisted coil embolization for unruptured intracranial aneurysms using the Alpha stent. Between January 2021 and November 2021, 35 adult patients with 35 unruptured intracranial aneurysms in the distal internal carotid artery were prospectively enrolled. For efficacy outcomes, magnetic resonance angiography at the 6-month follow-up was evaluated using the Raymond-Roy occlusion classification (RROC). The safety outcome evaluated the occurrence of symptomatic procedure-related neurological complications up to 6 months postoperatively. Technical success was achieved in 34/35 (97.1%). Six months postoperatively, aneurysm occlusion showed RROC I in 32/35 (91.4%) and RROC II in 3/35 (8.6%) patients. Procedure-related neurologic complications occurred in one patient (2.9%) who experienced hemiparesis due to acute lacunar infarction, which resulted in a 6-month mRS score of 1. The Alpha stent demonstrated excellent efficacy and safety outcomes in stent-assisted coil embolization of unruptured distal ICA aneurysms. The recent structural modifications allowed for easier stent delivery and deployment.Clinical trial registration number: KCT0005841; registration date: 28/01/2021.

Three-dimensional reconstruction imaging by C-arm computed tomography accurately visualizes in-stent neointimal formation in patients with stent-assisted coil embolization

Background

Stent apposition to the vessel wall and in-stent neointimal formation after stent-assisted coil embolization for intracranial aneurysm are important factors associated with postoperative thromboembolic complications. No assessment methods have been established to depict 3-dimensional (3D) all-round in-stent neointimal formation.

Objective

To demonstrate the superiority of Dyna-3D imaging assessment as a modality for all-round ISNF in comparison with conventional two-dimensional digital subtraction angiography (2D-DSA).

Methods

Consecutive patients who underwent braided stent-assisted coil embolization for unruptured aneurysm between November 2016 and September 2021 were enrolled. Radiological assessments for stent apposition to the parent vessel after stent deployment and in-stent neointimal formation after 3 months were obtained. Dyna-3D was reconstructed by overlapping a plain image showing stent struts with a rotational DSA image showing the vessel lumen. Reconstructed Dyna-3D images can be rotated to any angle on the screen to evaluate to stent apposition around the vessel and in-stent neointimal formation in 3D, for comparison with 2D-DSA evaluations.

Results

Among the 73 patients enrolled, 70 patients (96%) showed complete stent wall apposition on Dyna-3D. Higher intra-rater agreement was confirmed on assessment of in-stent neointimal formation with Dyna-3D (Cohen's κ = 0.811) than with conventional 2D-DSA (Cohen's κ = 0.517). in-stent neointimal formation could not be confirmed on conventional imaging in 9 cases (16%) and on Dyna-3D in 2 cases (3%). The number of in-stent neointimal formations rated as stent wire completely outside the endothelial line was significantly higher with Dyna-3D than with 2D-DSA (p = 0.0001).

Conclusion

All-round 3D evaluation by Dyna-3D imaging appears useful for confirming in-stent neointimal formation after braided stent deployment in patients after stent-assisted coil embolization.

Comparison of Enterprise stent 2 with 1 in assisting coiling of ruptured aneurysms: a real-world study

Aim: To investigate the effectiveness and safety of the Enterprise 2 (E2) stent versus the Enterprise 1 (E1) stent in treating ruptured intracranial aneurysms (RIAs) in China. Materials & methods: The authors conducted an electronic medical record analysis for patients with RIAs who underwent E1/E2 deployment. The main outcomes were immediate complete occlusion (ICO), patient functional outcomes, complications and aneurysm recurrence. Results: Stent deployment was successful in all patients (E2: 90; E1: 270). ICO and patients with good functional outcomes at discharge were similar between E2 and E1 (80.0% vs 75.1% and 78.7% vs 81.1%, respectively). The E2 group had a significantly lower complication rate compared with the E1 group (7.8% vs 16.4%; odds ratio: 0.36; 95% CI: 0.15-0.91; p = 0.031). By 6 months post-discharge, the two groups had comparable patient functional outcomes and aneurysm recurrence (E2 vs E1: 80.2% vs 81.9% and 13.3% vs 14.9%). Conclusion: Compared with the E1 stent, the E2 stent had similar effectiveness but a lower complication risk in treating RIAs.

The Enterprise2 Stent for Endovascular Treatment of Intracranial Aneurysms: Short-Term Results From a Single Center Experience

Background: Self-expanding devices, such as the Enterprise VRD (EP-VRD) have widely used for stent-assisted coiling treatment in wided-necked aneuryms while some thromboembolic complications were reported due to its incomplete stent apposition (ISA). We report our experiences on the novel Enterprise2 (EP-VRD2) stent in vivo in the treatment of intracranial and cranial cervical junction aneurysms.

Methods: Twenty-five consecutive patients with intracranial or cranial cervical junction aneurysms were treated with EP-VRD2 stents retrospectively collected in our institution. We use the ‘jailing' technique in all cases and deployed the stent by using pushing over the outer curve technique. The 3- or 6-monthS follow-up was done regularly by DSA.

Results: Twenty-five EP-VRD2 stents were implanted to treat 21 aneurysms at the siphon segment of internal carotid artery (ICA), one at the petrous segment, two at the cervical segment, one at the verteral artery with five accompanied with stenosis. Two patients had kinking during the procedure and were solved by microwire or microcatheter massaging. Four patients with a larger arc angle and a smaller radius of the parent vessel was detected ISA. No patient underwent the ischemic event after the operation. Twenty-three of 25 patients were evaluated after 3- or 6-months by DSA, 22 showed complete occlusion (RROC1), one slight re-stenosis in the follow-up within those five patients with stenosis. A length of 23 mm seemed associated with ISA (p < 0.01).

Conclusion: The EP-VRD2 performed well in our small patient series; however, ISA could still occur with a sharp angle of the parent vessel.

Strategies to Prevent Ischemic Complications after Stent-assisted Coil Embolization of Cerebral Aneurysms

Objective

There have been no delayed ischemic complications related to stent-assisted coil embolization (SACE) of cerebral aneurysms at our institution. We demonstrate our strategies for stent placement and postoperative management of antiplatelet therapy to reduce the risk of ischemic complications.

Methods

We analyzed 57 cases of SACE retrospectively. In the procedure, an appropriate stent was selected and placed to fit the arterial wall without impeding on small arterial branches. Two different antiplatelet drugs, including clopidogrel, were used. Six to twelve months after surgery, follow-up angiography was performed to assess the safety of terminating antiplatelet therapy. In cases in which antiplatelet therapy was tapered, the two antiplatelet drugs were switched to clopidogrel alone, and it was subsequently tapered and finally discontinued.

Results

There were 49 cases of SACE in which postoperative antiplatelet therapy was tapered. Among these cases, antiplatelet therapy was discontinued in 35 cases. The mean duration of dual antiplatelet therapy was 10.6 ± 2.8 months, and the mean duration of total antiplatelet therapy was 15.0 ± 2.1 months. Three patients developed SACE-related ischemic stroke, which developed in the early phase after surgery in all.

Conclusion

Antiplatelet therapy can safely be terminated in most cases of SACE. In order to reduce the risk of ischemic complications, stent selection, stent placement, and management of antiplatelet therapy should be performed appropriately. Furthermore, careful follow-up should be continued even after the termination of antiplatelet therapy.

Optimum concentration of iodine contrast agent injection for best stent visualization using Neuroform Atlas stent during stent-assisted coil embolization: Case reviews based on in vitro experiments

Background:

The present study aimed to evaluate the influence of contrast agent concentration (Conc) on the visibility of Neuroform Atlas in vitro and in clinical cases.

Methods:

A plastic tube was filled with several Conc. in saline (experiment 1) and blood (experiment 2). Thereafter, the Neuroform Atlas was placed around the plastic tube in an acrylic shield case. In experiment 3, the Neuroform Atlas was placed in the internal carotid artery of the endo vascular evaluator endovascular training system with an injection of several Conc in saline. Five slices of the axial images obtained using the 3D-cone-beam computed tomography (3D-CBCT) with the digital subtraction angiography system were evaluated. A 1-cm² circular center, which showed the contrast agent in saline or blood, was determined as the region of interest, and its pixels were evaluated.

Results:

Radiation density (Rd) was directly proportional to the contrast agent in saline and blood (experiment 1: (Rd (pixel)) = 6.8495 × (concentration (%)) + 152.72 (R² = 0.99), experiment 2: (Rd (pixel)) = 6.2485 × (concentration (%)) + 167.42 (R² = 0.9966), experiment 3: (Rd (pixel)) = 10.287 × (concentration (%)) + 108.26 (R² = 0.993)]. Rd calculated similarly in our cases (concentration varied from 5% to 8%) was between the range of “Rd of experiment 2” and “Rd of experiment 3.”

Conclusion:

Based on our in vitro experiments, with 5–8% concentration, Neuroform Atlas stent deployment with complete neck coverage by the bulging stent and wall apposition was visualized on 3D-CBCT.

Comparative Outcome Analysis of Enterprise and Neuroform Stent-Assisted Coiling of Cerebral Aneurysms: A Review of the Literature

Introduction

One of the popular treatment strategies for complex cerebral aneurysms with wide necks or low dome-to-neck ratios is stent-assisted coiling. The most widely used intracranial stents for stent-assisted coiling are Neuroform (NF) and Enterprise (EP) stents. The purposes of this study are to review the recent literature of the past 5 years to compare outcomes between the EP and NF stent-assist coiling systems so as to comment on the safety, efficacy, complications, and recurrence rate of stent-assisted coiling in general.

Methods

PubMed was used to search for all published literature of NF or EP stent-assisted coiling of unruptured cerebral aneurysms from January 2014 to August 2019 with the search terms of "Enterprise stent-assisted coiling," "Neuroform stent," and "Neuroform vs. Enterprise stent."

Results

Twenty two publications met the inclusion criteria which encompass 1764 patients and 1873 aneurysms. Out of these 1873 aneurysms, 1007 aneurysms were treated with EP stent and 866 aneurysms were treated with NF stent. The overall outcome was low rates of thromboembolic complications (4.37%) and intracranial hemorrhage (1.13%), low permanent morbidity (1.70%) and mortality (0.40%), and lower rate of recanalization (11%). Data analysis shows an overall higher rate of complication and recurrence of aneurysm and lower overall rate of aneurysmal occlusion in the patients where EP stent was used in comparison to NF stent. However, this difference was not statistically significant.

Conclusions

The review of two stent-assisted coiling devices using EP and NF stents including 1873 aneurysms in 1764 patients revealed that overall, it is safe and effective with comparable outcomes.

In Vitro Evaluation of Fusiform-Shaped Stents for Wide-Neck Intracranial Aneurysm Treatment

PURPOSE

Wide-neck aneurysms (WNAs) associated with a dilated parent artery (PA) are not uncommon morphological abnormalities and usually cause inappropriate wall apposition and incomplete neck coverage of a tubular stent in stent-assisted coiling of aneurysms. We aimed to introduce a fusiform-shaped stent (FSS) and test its effectiveness in treating intracranial WNAs associated with a dilated PA using a three-dimensional (3D) model.

MATERIALS AND METHODS

Two FSS types were designed with the middle one-third segment dilated by 10% (FSS10) and 20% (FSS20) and were compared with the tubular-shaped stent (TSS). A patient-specific 3D WNA model was prototyped and produced, and in vitro stent placement was performed. Angiographic images of the three stent types were analyzed and compared using predetermined parameters.

RESULTS

The stent lumens were significantly larger in FSS10 and FSS20 than in TSS in the middle segments (P=0.046), particularly FSS20 (P=0.018). The non-covered area at the ostium tended to be smaller in FSS10 and FSS20 than in TSS, but the difference was not significant (P>0.05). The stent length was significantly longer in FSS10 and FSS20 than in TSS. The stent cell size was significantly larger in FSS than in TSS.

CONCLUSION

Better vessel wall apposition and aneurysmal neck coverage was observed for FSS than for TSS. No significant difference was observed between FSS10 and FSS20.

A clinical comparison of Atlas and LVIS Jr stent-assisted aneurysm coiling

BACKGROUND

Case series have described the safety and efficacy of LVIS Jr and Atlas stent-assisted aneurysm coiling, but their comparative clinical performance has not yet been formally studied.

OBJECTIVE

To clinically compare LVIS Jr and Atlas stents, emphasizing comparative rates of technical success and complications.

METHODS

Our institutional endovascular database was queried for aneurysms treated by stent-assisted coiling with either the LVIS Jr or Atlas stents. Demographic data, aneurysm information, treatment technique, periprocedural and device-related complications, and initial and follow-up angiographic results were evaluated.

RESULTS

Thirty-seven patients underwent Atlas stent placement and 27 patients underwent LVIS Jr stent placement for aneurysm coiling. There was no significant difference in aneurysm location, size, coiling technique, and coil packing density between the two cohorts. The rate of initial Raymond 1 occlusion was significantly greater in the Atlas cohort (57% vs 41%, P=0.03). The rate of postoperative ischemic complications, both clinically apparent and as defined on postoperative MRI diffusion-weighted imaging, did not significantly differ between the two groups. Follow-up DSA demonstrated a significantly greater rate of Raymond 1 or 2 occlusion for the Atlas cohort (100% vs 81%, P=0.04), and a significantly lower rate of in-stent stenosis (0% vs 19%, P=0.04).

CONCLUSION

This institutional analysis demonstrates greater obliteration rates and lower in-stent stenosis rates for aneurysms treated via Atlas stent-assisted coiling as compared with those treated via LVIS Jr stent-assisted coiling.

Semi-Jailing Technique Using a Neuroform3 Stent for Coiling of Wide-Necked Intracranial Aneurysms

Objective

The semi-jailing technique (SJT) provides stent-assisted remodeling of the aneurysm neck during coil embolization without grasping the coil delivery microcatheter. We retrospectively evaluated the efficacy and safety of SJT using a Neuroform3 stent for coiling of wide-necked intracranial aneurysms.

Methods

We collected the clinical and radiological data between January 2009 and June 2015 of the wide-necked aneurysms treated with SJT using a Neuroform3 stent.

Results

SJT using a Neuroform3 stent was attempted in 70 wide-necked aneurysms (68 patients). There were 56 unruptured and 14 ruptured aneurysms. The size of aneurysm ranged from 1.7 to 28.1 mm (mean 6.1 mm). The immediate angiographic results were complete occlusion in 55 aneurysms (78.6%), neck remnant in 7 (10.0%), and aneurysm remnant in 8 (11.4%). Overall, periprocedural complications occurred in 13 patients (19.1%), including asymptomatic thromboembolism in 7 (10.3%), symptomatic thromboembolism in 4 (5.9%), and symptomatic hemorrhagic complications in 2 (2.9%). Conventional angiography follow-up was obtained in 55 (78.6%) of 70 aneurysms (mean, 10.9 months). The result showed progressive occlusion in 7 aneurysms (12.7%) and recanalization in 1 aneurysm (1.8%). At the end of the observation period (mean, 17.5 months), all 54 patients without subarachnoid hemorrhage showed excellent clinical outcomes (modified Rankin Scale [mRS] 0), except two (mRS 1 or 2) and seven of 14 patients with subarachnoid hemorrhage remained symptom-free (mRS 0).

Conclusion

In this report of 70 aneurysms, SJT using a Neuroform3 stent for coiling of wide-necked intracranial aneurysms showed good technical safety, as well as favorable clinical and angiographic outcomes.

The Interference Phenomenon of Microcatheters in the Jailing Treatment for Internal Carotid Artery Side Wall Aneurysms with an Open Cell Stent System

Objective

Excelsior XT-27 (Stryker Neurovascular, Fremont, CA, USA) or Rebar 27 (eV3 Covidien, Irvine, CA, USA) microcatheters have recently been used to overcome the limitations of the Renegade Hi-Flo microcatheter such as interference between two microcatheters (one for stent delivery and the other for cerebral aneurysm coiling) during the jailing technique. We evaluated differences and influential factors related to the interference phenomenon according to these two microcatheters group.

Materials and Methods

Between June 2011 and September 2013, the jailing technique was applied to 94 internal cerebral artery (ICA) aneurysms. The jailing technique with the Neuroform EZ stent system was performed using Renegade (n = 22), Rebar (n = 35), and XT-27 microcatheters (n = 37). In the Renegade Hi-Flo microcatheter group, the jailing technique was successful in 19/22 patients (86.4%) and interference between the two microcatheters occurred in 6/21 patients (28.6%). In the Rebar and XT-27 microcatheter group, the jailing technique was successful in 71/72 patients (98.6%) and interference between the two microcatheters occurred in 1/72 patients (1.4%).

Results

There was a significant difference in the interference between the two delivered microcatheters group (p-value < 0.000) and the carotid siphon angle (p-value: 0.004) in the univariate analysis. In the multiple logistic regression analysis, the Rebar and XT-27 microcatheter group (odds ratio [OD] [95% confidence interval (CI)]; 31.277 [3.138-311.729], p-value: 0.003) and the carotid siphon angle (OD [95%CI]; 0.959 [0.922-0.997], p-value: 0.035) were found to be influential factors in the interference phenomenon.

Conclusion

The Rebar 27 and XT-27 microcatheters were more successful and exhibited less interference between the two microcatheters than the Renegade Hi-Flo microcatheter.

Observation of Neointimal Coverage Around the Aneurysm Neck After Stent-Assisted Coil Embolization by Optical Frequency Domain Imaging: Technical Case Report

BACKGROUND AND IMPORTANCE: Stent-assisted coil embolization has been established as a treatment option for wide-necked or complex aneurysms. However, concerns have been raised about the incidence of thromboembolic complications, which is higher for coil embolization without stent assistance. Long-term antiplatelet therapy is necessary to prevent acute or delayed ischemic events potentially associated with incomplete stent apposition after treatment with stent-assisted coil embolization. Optical frequency domain imaging (OFDI) provides excellent-resolution images of intraluminal structures, allowing evaluation of the outcomes of stent-assisted procedures in terms of stent apposition and neointimal coverage. We here describe the novel use of OFDI for the observation of intravascular tissue formation after stent-assisted coil embolization.

CLINICAL PRESENTATION: Two patients were treated with stent-assisted coil embolization for unruptured vertebral artery aneurysm. At the 1- or 2-yr follow-up visit, routine angiography followed by OFDI were performed to evaluate neointimal coverage of the stent strut and stent apposition to the vascular wall. OFDI enabled clear visualization of the vessel wall structures and demonstrated complete coverage of the stent struts as well as full stent wall apposition in 1 patient and incomplete coverage near the aneurism neck as well as mallaposition of some struts in the other patient.

CONCLUSION: OFDI represents a feasible modality for the evaluation of intracranial vasculature and the outcomes of stent-assisted coil embolization in terms of intimal healing of aneurysms, stent-vessel interactions, and neointimal coverage of the stent. Such information is helpful in determining the duration of antiplatelet therapy after stent-assisted coil embolization.

Insufficient platelet inhibition and thromboembolic complications in patients with intracranial aneurysms after stent placement

OBJECT

Insufficient platelet inhibition has been associated with an increased incidence of thromboembolic complications in cardiology patients undergoing percutaneous coronary intervention. Data regarding the relationship between insufficient platelet inhibition and thromboembolic complications in patients undergoing neurovascular procedures remain controversial. The purpose of this study was to assess the relationship of insufficient platelet inhibition and thromboembolic complications in patients with intracranial aneurysm undergoing stent treatment.

METHODS

The authors prospectively recruited patients with intracranial aneurysms undergoing stent treatment and maintained the data in a database. MRI with diffusion-weighted sequences was performed within 24 hours of stent insertion to identify acute ischemic lesions. The authors used thromboelastography to assess the degree of platelet inhibition in response to clopidogrel and aspirin. Univariate and multivariate logistic regression analysis was used to identify potential risk factors of thromboembolic complications.

RESULTS

One hundred sixty-eight patients with 193 aneurysms were enrolled in this study. Ninety-one of 168 (54.2%) patients with acute cerebral ischemic lesions were identified by diffusion-weighted MRI. In 9 (5.4%) patients with ischemic lesions, transient ischemic attack or stroke was found at discharge, and these complications were found in 11 (6.5%) patients during the follow-up period. The incidence of periprocedural thromboembolic complications increased with resistance to antiplatelet agents, hypertension, hyperlipidemia, complete occlusion, and aneurysm of the anterior circulation. The multivariate regression analysis demonstrated that the anterior circulation and adenosine diphosphate (ADP) inhibition percentage were independent risk factors of perioperative thromboembolic complications. The maximum amplitude and ADP inhibition percentage were independent risk factors for thromboembolic complications during the follow-up period.

CONCLUSIONS

The ADP inhibition percentage is related to thromboembolic complications after stent placement for intracranial aneurysms. The increase of the ADP inhibition may decrease the risk of thromboembolic complications.

Stent-assisted coil embolization of challenging intracranial aneurysms: initial and mid-term results with low-profile ACCLINO devices

BACKGROUND

Stent-assisted coiling using low-profile, self-expandable and retrievable stents is a valid option in endovascular treatment of challenging intracranial aneurysms. This study aims to evaluate the feasibility and efficacy of ACCLINO 1.9 F and ACCLINO Flex stent systems, designed for use as adjunctive products in coil embolization of intracranial aneurysms.

METHODS

Case files of 47 patients, and 52 aneurysms in total, treated with at least one ACCLINO 1.9 F or ACCLINO Flex stent were retrospectively evaluated. Technical success, complications, and angiographic outcomes were assessed based on immediate post-procedural controls along with 6th and 12th month angiograms.

RESULTS

Mechanical untoward event rate, including asymptomatic complications, is 9.6 % (five out of 52 aneurysms). Failed dual-stenting attempt rate is 15.4 % (two out of 13). Overall procedure-related morbidity is 4.2 % with no neurologic sequelae. Initial occlusion rate is 90.4 % (47 aneurysms). One patient had residual filling in the aneurysm neck, which was stable throughout follow-up. The remaining four cases had spontaneous follow-up occlusion. Recanalization rate at 6th month is 2.1 % with one aneurysm requiring retreatment. One patient was lost to follow-up. There is no mortality associated with treatment.

CONCLUSIONS

Stent-assisted coil embolization with ACCLINO stents in single or dual configurations is a feasible treatment option for challenging intracranial aneurysms. Follow-up results are encouraging; techniques were effective in complex cases and there were no clinically significant adverse outcomes.

In vitro experiments of vessel wall apposition between the Enterprise and Enterprise 2 stents for treatment of cerebral aneurysms

BACKGROUND

A closed-cell stent called Enterprise has been used for stent-assisted coil embolization of cerebral aneurysms. The Enterprise stent tends to cause kinks and vessel wall malposition in curved vessels and may cause thromboembolic complications. We evaluated vessel wall apposition of a new closed-cell stent, Enterprise 2, compared with a previous Enterprise stent, using curved vascular silicone models.

METHODS

The Enterprise or Enterprise 2 stent was deployed in curved vascular models with various radii of approximately 5 to 10 mm. Stent deployment was performed 25 times in each stent. A push-pull technique was used to minimize incomplete wall apposition. To evaluate conformity of stents, gaps between a stent and a vessel wall were measured.

RESULTS

The gap ratio (gap / a wall diameter) was 15 % ± 17 % (mean ± standard deviation) and 41 % ± 15 % with the Enterprise 2 stent and the Enterprise stent, respectively. Taking gap ratios and radii of vessel curvature into consideration, the Enterprise 2 stent had significantly better wall apposition than the Enterprise stent (p = 0.005). In the same radius of vessel curvature, the Enterprise 2 stent had approximately half of the gap compared with the Enterprise stent. There were no significant differences in vessel straightening effects between the two stents.

CONCLUSIONS

The Enterprise 2 stent has better wall apposition in curved vessels than the Enterprise stent. The gap between a vessel wall and the Enterprise 2 stent is approximately half that of the Enterprise stent. However, gaps and kinks are still present in curved vessels with a small radius. Caution should be taken for kinks and malposition in acutely curved vessels, such as the siphon of the internal carotid artery.

Enlarged Parent Artery Lumen at Aneurysmal-Neck Segment in Wide-Necked Distal Internal Carotid Artery Aneurysms

Purpose

Hypothesizing that the parent artery (PA) diameter of the aneurysm-neck segment is larger than those of normal segments, especially in wide-necked aneurysm cases, we conducted 3D angiographic analyses in wide-necked aneurysm cases focusing on the luminal morphologic change of the PA.

Materials and Methods

Under the approval of local IRB, we enrolled 26 patients with distal internal carotid artery (ICA) aneurysms, which were treated with stent assisted coiling. The PA diameters along the centerline were measured at 6 points with built-in software by two observers. Those 6 points were P1 and P2 proximally, P3 and P4 at the aneurysm ostium margins, and P5 and P6 distally. We performed an ANOVA test and a Bonferroni method for post hoc analyses. Linear regression analysis was performed to find any morphologic influencing factors.

Results

There were 20 distal ICA aneurysms out of 26 consecutive cases after exclusion. The differences in diameter at each point were statistically significant (p<0.0001). On post hoc analyses, the difference between P4 and P5 was significant both in maximum and mean PA diameters (p<0.0001 and p<0.001, respectively). Multivariate analyses failed to reveal any morphological influencing factor.

Conclusion

PAs harboring a wide-necked aneurysm requiring stent assistance for coiling showed significant enlargement of the lumen, especially at the distal transition segment of the aneurysm ostium and the PA.

Microembolism after endovascular coiling of unruptured cerebral aneurysms: incidence and risk factors

OBJECTIVE

The incidence and risk factors of microembolic lesions on MR diffusion-weighted imaging (DWI) were analyzed after the endovascular coiling of unruptured intracranial aneurysms (UIAs).

METHODS

Data obtained from 271 consecutive patients (70 men and 201 women; median age 57 years; range 23-79 years) who presented with UIA for coil embolization between July 2011 and June 2013 were analyzed. Two independent reviewers examined the DWI and apparent diffusion coefficient maps obtained the following day for the presence of restrictive diffusion spots and counted the number of spots. Multivariate analysis was then performed to identify independent risk factors for developing microembolism following the coiling of an aneurysm.

RESULTS

Microembolic lesions were noted in 101 of 271 patients (37.3%). The results of the multivariate analysis showed that the following factors significantly influenced the risk for microembolism: age, diabetes, previous history of ischemic stroke, high-signal FLAIR lesions in the white matter, multiple aneurysms, and the insertion of an Enterprise stent (all ORs > 1.0 and all p values < 0.05). Previously known risk factors such as prolonged procedure duration, aneurysm size, and decreased antiplatelet function did not show any significant influence.

CONCLUSIONS

The incidence of microembolism after endovascular coiling of UIA was not low. Lesions occurred more frequently in patients with vascular status associated with old age, diabetes, and previous stroke. Aneurysm multiplicity and the type of stent used for treatment also influenced lesion occurrence.

Stent-assisted coil embolization of aneurysms with small parent vessels: safety and efficacy analysis

BACKGROUND

Stent-assisted coil embolization (SACE) is a viable therapeutic approach for wide-neck intracranial aneurysms. However, it can be technically challenging in small cerebral vessels (≤2 mm).

OBJECTIVE

To present our experience with stents approved for SACE in aneurysms with small parent arteries.

METHODS

All patients who underwent stent-assisted aneurysm treatment with either a Neuroform or an Enterprise stent device at our institution between June 2006 and October 2012 were identified. Additionally, we evaluated each patient's vascular risk factors, aneurysm characteristics (ruptured vs non-ruptured, incidental finding, recanalized) and follow-up angiography data.

RESULTS

A total of 41 patients with 44 aneurysms met our criteria, including 31 women and 10 men. Most of the aneurysms were located in the anterior circulation (75%). Stent placement in vessels 1.2-2 mm in diameter was successful in 93.2%. Thromboembolic complications occurred in 6 cases and vessel straightening was seen in 1 case only. Initial nearly complete to complete aneurysm obliteration was achieved in 88.6%. Six-month follow-up angiography showed coil compaction in three cases, one asymptomatic in-stent stenosis and stent occlusion. Twelve to 20-months' follow-up showed stable coil compaction in two patients compared with previous follow-up, and aneurysm recanalization in two patients. Twenty-four to 36-months' follow-up showed further coil compaction in one of these patients and aneurysm recanalization in a previous case of stable coil compaction on mid-term follow-up.

CONCLUSIONS

Our results suggest that SACE of aneurysms with small parent vessels is feasible in selected cases and shows good long-term patency rates of parent arteries.

Ocular thrombosis after stent-assisted coiling of a c7 (paraclinoid) internal carotid artery aneurysm. A report of two cases and literature review

Stent-assisted coiling of paraclinoid aneurysms is widely performed in neurointerventional surgery. The most common adverse event related to this procedure is cerebral thromboembolism. However, reports on ocular thromboembolism are scarce. We report our experience with two patients who developed ocular thromboembolism following Enterprise stent-assisted coiling of paraclinoid aneurysms. We then review the available literature for the possible pathomechanism of ocular thrombosis. Ocular thromboembolism may be a risk of stent-assisted coiling when the stent traverses the orifice of the ophthalmic artery or the stent is placed in the C3 internal carotid artery. Further study is needed to clarify how to avoid this disabling complication.

"Y" and "X" stent-assisted coiling of complex and wide-neck intracranial bifurcation aneurysms

BACKGROUND AND PURPOSE

Stent-assisted coiling with two stents has been described in some series for the treatment of complex and wide-neck bifurcation aneurysms. Our aim was to report our experience of a stent-assisted coiling technique with double stents in "Y" and "X" configurations, with emphasis on safety, feasibility, and efficacy.

MATERIALS AND METHODS

Clinical and angiographic outcomes of patients for whom the strategic therapeutic option was the stent-assisted coiling technique in a Y or X configuration for neck scaffolding from June 2006 to June 2013 were retrospectively analyzed.

RESULTS

One hundred five aneurysms in 97 patients were treated during 100 consecutive procedures. There were 54.2% (57/105) MCA, 28.6% (30/105) anterior communicating artery, 16.2% (17/105) basilar tip, and 1.0% (1/105) ICA termination aneurysms. A Y stent placement was used to treat 87 aneurysms in 85 procedures; an X stent placement was used to treat 7 aneurysms in 6 procedures, while 9 procedures failed for 11 aneurysms. There were 10.0% (10/100) procedure-related permanent neurologic deficits and 1.0% (1/100) death. The immediate angiographic controls showed a complete occlusion in 47.6% (50/105) of the aneurysms and a partial (neck or sac remnant) occlusion in 52.4% (55/105). To date, 81.0% (85/105) of the aneurysms have been followed up (mean, 17 months) with angiography, disclosing a recanalization in 5.9% (5/85) and an improvement in 42.4% (36/85). At discharge and follow-up, the mRS score was 0 in 83.5% (81/97) of patients, 1 in 4.1% (4/97), 2 in 3.1% (3/97), 3 in 4.1% (4/97), 4 in 3.1% (3/97), and 6 in 2.1% (2/97).

CONCLUSIONS

Y and X stent-assisted coiling of complex and wide-neck intracranial bifurcation aneurysms is an effective technique.

A Self-expanding Nitinol Stent (Enterprise) for the Treatment of Wide-necked Intracranial Aneurysms: Angiographic and Clinical Results in 40 Aneurysms

Objective

Self-expanding stents are increasingly used for the treatment of complex intracranial aneurysms. The purpose of this study was to evaluate the usefulness and safety of a self-expanding nitinol stent (Enterprise) in the treatment of wide-necked intracranial aneurysms.

Methods

This was a retrospective study of 39 patients with 40 wide-necked intracranial aneurysms who were enrolled in a single-center registry of patients treated with the Enterprise between June 2009 and December 2011. Thirty patients were asymptomatic, four had cerebrovascular accident sequelae, and five had suffered subarachnoid hemorrhage. One aneurysm had reopened after prior coil embolization, while 39 had not been treated. Clinical charts, procedural data, and angiographic results, including both immediate post-procedural angiograms and follow-up imaging, were reviewed.

Results

The mean neck size of the aneurysms was 5.58 mm (range 3-15.1 mm). Embolization was successful in all patients. There were five procedure-related events. There were no fatalities, but one procedure-related morbidity was noted. The immediate angiographic results included eight complete occlusions (20%), six remnant necks (15%), and 26 remnant sacs (65%). At angiographic follow-up (mean: 11.3 months), out of 18 of the aneurysms treated with stent-assisted coiling, there were 13 (72.2%) complete occlusions, four (22.2%) remnant necks, and one recanalization (5.6%).

Conclusion

Stent-assisted coiling using the Enterprise is effective for the treatment of wide-necked intracranial aneurysms. Further angiographic and clinical follow-up investigation will be needed for evaluation of the long-term outcomes.

Jailing Technique Using a Catheter-based Open-cell Stent System in Internal Carotid Artery Sidewall Aneurysms Unfeasible to Simple Coiling

Objective

An open cell stent system may offer better apposition of cell struts to vessel wall than a closed cell stent system in acute vasculature. The purpose of this study was to evaluate the feasibility of coiling using the jailing technique with the Neuroform EZ stent system.

Methods

The jailing technique using the open-cell stent system of the Neuroform EZ stent was planned in 22 consecutive patients with 22 cerebral aneurysms. We retrospectively evaluated the technical success of the jailing technique and the occurrence of interference between two microcatheters as well as the factors influencing this interference.

Results

The jailing technique was successful in 19/22 patients (86.4%), and interference between two microcatheters occurred in 6/21 (28.6%). The jailing technique failed in 3/22 patients, with problems that included failure of the stent delivery system to advance into the positioned microcatheter in one, interference between the microcatheters during the advancement of the stent delivery system in one, and failure of microcatheter insertion into the aneurysm sac in the remaining patient. Interference between the two microcatheters developed during the advance of the stent delivery system into the positioned microcatheter in all cases. One factor that influences interference between two microcatheters more than expected by chance is the carotid siphon angle (p = 0.019).

Conclusion

The acuteness of the carotid siphon angle influences the interference between two microcatheters. Therefore, the jailing technique using the Neuroform EZ stent should be performed carefully in cerebral aneurysms with an acute carotid siphon angle because the procedure may possibly fail.

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.

Analysis of closed-cell intracranial stent characteristics using cone-beam computed tomography with contrast material

The intracranial nitinol stent named the Enterprise Vascular Reconstruction Device has poor radiographic visibility. The characteristics of closed-cell intracranial stents were investigated and the efficacy of intraoperative stent visualization examined with the 80 kV high-resolution XperCT protocol, which is a flat detector C-arm volume acquisition functionality system integrated with the angiography equipment. We treated 39 aneurysms with stent-assisted coil embolization. The aneurysms were located on the internal carotid artery in 24 cases, the anterior communicating artery (AcomA) in three, the basilar artery (BA) in 10, and the vertebral artery in two. Intraoperative 80 kV XperCT was performed in all cases after deposition of the stent. We evaluated the coverage of the aneurysm neck, incomplete stent apposition (ISA), and shift of vessels. Accurate stent visualization was achieved in 29 of the 39 cases without coil and delivery wire artifact. Coverage of the aneurysm neck succeeded in 28 cases; there was one case of BA top Y-configuration stenting in which the stent was dislocated into the aneurysm. ISA was detected in nine cases, including seven kinks and one flattening in the carotid siphon and one kink in the BA top. We detected linearization of vessels due to stent deployment in three AcomA cases and three BA top cases. We conclude that intraoperative 80 kV XperCT is an efficient modality for the evaluation of ISA. Stent kinking in the carotid siphon and linearization in distal vessels can be detected with this protocol.

Advances in Endovascular Approaches to Cerebral Aneurysms

Recent advancements in all phases of endovascular aneurysm treatment, including medical therapy, diagnostics, devices, and implants, abound. Advancements in endovascular technologies and techniques have enabled treatment of a wide variety of intracranial aneurysms. In this article, technical advances in endovascular treatment of cerebral aneurysms are discussed, with an effort to incorporate a clinically relevant perspective. Advancements in diagnostic tools, medical therapy, and implants are reviewed and discussed.

Stent recanalization of carotid tonsillar loop dissection using the Enterprise vascular reconstruction device

Although advances in endovascular techniques have permitted reconstruction of intimal dissections and related pseudoaneurysms of the extracranial cervical internal carotid artery, highly tortuous tonsillar loop anatomic variants still pose an obstacle to conventional extracranial self-expanding carotid stents. During a 12 year period, nine of 48 cases with cervical carotid dissections were associated with a tonsillar loop. Five patients required endovascular treatment, which was performed using a microcatheter-based technique with the low-profile Enterprise vascular reconstruction device (Codman Neurovascular, Raynham, MA, USA). Technical, radiographic, and clinical outcomes were analyzed for each patient. Dissection etiology was spontaneous in three patients, iatrogenic in one, and traumatic in one. Four near-occlusive tonsillar loop dissections were successfully recanalized during the acute phase. Dissection-related stenosis improved from 90±22% to 31±13%, with tandem stents needed in three instances to seal the inflow zone. There were no procedure-related transient ischemic attacks (TIA), minor/major strokes, or deaths. Angiographic follow-up for a mean of 28.0±21.6 months showed all stents were patent, with average stenosis of 25.2±12.2%. Focal ovalization and kinking of the closed-cell design was noted at the sharpest curve in one patient. Clinical outcome (follow-up of 28.1±21.5 months) demonstrated overall improvement with no clinical worsening, new TIA, or stroke. Tonsillar loop-associated carotid dissections can be successfully and durably recanalized using the low-profile Enterprise stent with an excellent long-term patency rate and low procedural risk. The possibility of stent kinking and low radial force should be considered when planning reconstruction with this device.

Effect of antiplatelet therapy on thromboembolism after flow diversion with the Pipeline Embolization Device

Object

Flow-diverting stents offer a novel treatment approach to intracranial aneurysms. Data regarding the incidence of acute procedure-related thromboembolic complications following deployment of the Pipeline Embolization Device (PED) remain scant. The authors sought to determine the rate of embolic events in a bid to identify potential risk factors and assess the role of platelet inhibition.

Methods

Data in all patients receiving a PED for treatment of an intracranial aneurysm were prospectively maintained in a database. Diffusion-weighted 3-T MRI was performed within 24 hours of PED deployment. The incident rate of procedural embolism was established, and univariate analysis was then performed to determine any associations of embolic events with measured variables. The degree of platelet inhibition in response to aspirin and clopidogrel was evaluated by challenging the platelet samples with arachidonic acid and adenosine diphosphate, respectively, and then performing formal light transmission platelet aggregometry.

Results

Twenty-three patients with 26 aneurysms were eligible for inclusion in the study. Thirty-one PEDs were deployed in 25 procedures. All ischemic lesions detected on diffusion-weighted 3-T MRI were identified as embolic based on their location and distribution, with none appearing to be due to perforator artery occlusion. Procedural embolic events were found in the target parent vessel territory in 13 (52%) of 25 procedures, with no patients harboring lesions contralateral to the deployed PED. The number of embolic events per procedure ranged from 3 to 16, with a mean of 5.4. There was no significant difference between cases with and without procedural embolism in platelet inhibition by aspirin (mean 15% vs 12% residual activation; p = 0.28), platelet inhibition by clopidogrel (mean 41% vs 41% residual activation; p = 0.98), or intraprocedural heparin-induced anticoagulation (mean activated clotting time 235 seconds vs 237 seconds; p = 0.81). By multivariate analysis, the authors identified larger aneurysm size (p = 0.03) as the single variable significantly associated with procedural embolism. There was no significant relationship between aneurysm size and the number of embolic events (p = 0.32) or the total burden of the embolism lesion area (p = 0.53).

Conclusions

Acute embolism following use of the PED for treatment of intracranial aneurysms is more common than hypothesized. The only identifiable risk factor for embolism appears to be greater aneurysm size, perhaps indicating significant disturbed flow across the aneurysm neck with ingress and egress through the PED struts. The strength of antiplatelet therapy, as measured by residual platelet aggregation, did not appear to be associated with cases of procedural embolism. Further work is needed to determine the implications of these findings and whether anticoagulation regimens can be altered to lower the rate of complications following PED deployment.

Stent-assisted coiling versus coiling alone in unruptured intracranial aneurysms in the matrix and platinum science trial: safety, efficacy, and mid-term outcomes

BACKGROUND AND PURPOSE

Stent-assisted coiling may result in less aneurysm recanalization but more complications than coiling alone. We evaluated outcomes of coiling with and without stents in the multicenter Matrix and Platinum Science Trial.

MATERIALS AND METHODS

All patients in the Matrix and Platinum Science Trial with unruptured intracranial aneurysms treated per protocol were included. Baseline patient and aneurysm characteristics, procedural details, neurologic outcomes, angiographic outcomes, and safety data were analyzed.

RESULTS

Overall, 137 of 361 (38%) patients were treated with a stent. Stent-coiled aneurysms had wider necks (≥4 mm in 62% with stents versus 33% without, P < .0001) and lower dome-to-neck ratios (1.3 versus 1.8, P < .0001). Periprocedural serious adverse events occurred infrequently in those treated with and without stents (6.6% versus 4.5%, P = .39). At 1 year, total significant adverse events, mortality, and worsening of mRS were similar in treatment groups, but ischemic strokes were more common in stent-coiled patients than in coiled patients (8.8% versus 2.2%, P = .005). However, multivariate analysis confirmed that at 2 years after treatment, prior cerebrovascular accident (OR, 4.7; P = .0089) and aneurysm neck width ≥4 mm (OR, 4.5; P = .02) were the only independent predictors of ischemic stroke. Stent use was not an independent predictor of ischemic stroke at 2 years (OR, 1.1; P = .94). Stent use did not predict target aneurysm recurrence at 2 years, but aneurysm dome size ≥10 mm (OR, 9.94; P < .0001) did predict target aneurysm recurrence.

CONCLUSIONS

Stent-coiling had similar outcomes as coiling despite stented aneurysms having more difficult morphology than coiled aneurysms. Increased ischemic events in stent-coiled aneurysms were attributable to baseline risk factors and aneurysm morphology.

Stent/balloon combination assist technique for wide-necked basilar terminal aneurysms

We describe an enhanced endovascular procedure for the coiling of broad-necked basilar terminal aneurysms with a combined balloon/stent assist technique. A balloon-assisted catheter is inserted in the origin of one posterior cerebral artery (PCA) and an assisted stent is deployed from the opposite PCA to the basilar artery. A microcatheter for coiling is inserted through the stent strut (trans-cell approach), and the aneurysm is coiled under stent support and assisted balloon inflation to keep the patency of both PCAs. This technique is more beneficial for reducing the risk of stent deformity than Y-stenting, and it provides a simpler procedure than other advanced stent techniques. Additionally, it enables an easy approach when retreatment is necessary for aneurysm recurrence. This technique may be one of the useful procedures for embolizing broad-necked basilar terminal aneurysms safely and effectively.

Triple antiplatelet therapy with addition of cilostazol to aspirin and clopidogrel for Y-stent-assisted coil embolization of cerebral aneurysms

BACKGROUND

Dual antiplatelet therapy for stent-assisted coiling of cerebral aneurysms is essential to prevent thromboembolic complications. There is concern that Y-stent-assisted coiling may increase thromboembolic complications compared with coiling with a single stent. Several reports have demonstrated that cilostazol may improve clopidogrel responsiveness. We investigated whether triple antiplatelet therapy with addition of cilostazol to aspirin plus clopidogrel for Y-stents can prevent thromboembolic events.

METHODS

Between July 2010 and October 2012, we treated 40 consecutive aneurysms with coil embolization using Enterprise stents. At the peri-procedural period, dual antiplatelet agents (100 mg aspirin and 75 mg clopidogrel) were used for the single stent group (n = 36), and triple antiplatelet agents (addition of 200 mg cilostazol) were used for the Y-stent group (n = 4). We evaluated post-operative diffusion-weighted imaging (DWI) and any complications. We assessed the following for statistical analysis: age, sex, aneurysm location, shape, and size, neck size, size of parent vessels, and stent length.

RESULTS

We found two neurological peri-procedural complications: one transient ischemic attack and one infarction. Both complications belonged to the Y-stent group, which was a significant factor of thromboembolic events (P = 0.008). There were no other significant factors related to neurological complications or positive DWI. For subgroup analysis of the single stent group, stent length was significantly longer in positive DWI than negative DWI (P = 0.04). In the follow-up period of 20 ± 8.6 months, there were no symptomatic late complications in any patients.

CONCLUSIONS

Although the number of patients in the Y-stent group is small, this group had a significantly higher risk of thromboembolic complications. While our protocol of a routine dose of dual antiplatelet therapy may be sufficient for single stent therapy, our protocol of a routine dose of triple antiplatelet therapy for Y-stents may not prevent thromboembolic events. This suggests that evaluation of platelet function may be essential, especially for Y-stents.

Neuroform Intracranial Stenting for Aneurysms Using Simple and Multi-stent Technique Is Associated With Low Risk of Magnetic Resonance Diffusion-Weighted Imaging Lesions

BACKGROUND:

Detection of procedural thromboembolism by diffusion-weighted magnetic resonance imaging (MR-DWI+) can help identify and mitigate endovascular risk factors. Data remain scant on procedural MR-DWI+ following the use of the Neuroform open-cell design stent in aneurysm embolization.

OBJECTIVE:

We sought to evaluate the incidence of MR-DWI+ in Neuroform simple and multi-stent construct stenting for intracranial aneurysms in an attempt to delineate baseline risk and identify possible associated procedural factors.

METHODS:

Seventy-six patients receiving 97 Neuroform stents in the treatment of intracranial aneurysm were identified from a prospective database and eligible for inclusion in the study. Diffusion-weighted magnetic resonance imaging (MR-DWI) was obtained in all patients within 48 hours of the procedure and reviewed for the presence of MR-DWI+ with patient records reviewed for analysis of factors predisposing to these lesions.

RESULTS:

Patients were treated with single-stent Neuroform constructs in 57 cases (73%) and multi-stent Neuroform constructs in 21 cases (27%). Y-stent technique was used in 16 cases. MR-DWI+ was identified in 7 of 78 cases (9.0%), with MR-DWI+ in 0 of 10 subarachnoid hemorrhage cases. No MR-DWI lesions led to a permanent neurological deficit at discharge. There was no MR-DWI+ in patients treated with Y-stenting or multi-stent Neuroform constructs. The only factor associated with ipsilateral MR-DWI+ was target aneurysm location on an arterial sidewall over bifurcation (P = .01).

CONCLUSION:

The Neuroform stent carries a very low risk of MR-DWI+ compared with its closed-cell design counterpart. Subarachnoid hemorrhage and deployment of multiple stents in the same anatomical region in configurations such as the Y-stent construct did not increase the risk of acute procedural thromboembolism.

Stent-assisted coiling of intracranial aneurysms: predictors of complications, recanalization, and outcome in 508 cases

BACKGROUND AND PURPOSE

Self-expanding stents are increasingly used for treatment of complex intracranial aneurysms. We assess the safety and the efficacy of intracranial stenting and determine predictors of treatment outcomes.

METHODS

A total of 508 patients with 552 aneurysms were treated with Neuroform and Enterprise stents between 2006 and 2011 at our institution. A multivariate analysis was conducted to identify predictors of complications, recanalization, and outcome.

RESULTS

Of 508 patients, 461 (91%) were treated electively and 47 (9%) in the setting of subarachnoid hemorrhage. Complications occurred in 6.8% of patients. In multivariate analysis, subarachnoid hemorrhage, delivery of coils before stent placement, and carotid terminus/middle cerebral artery aneurysm locations were independent predictors of procedural complications. Angiographic follow-up was available for 87% of patients at a mean of 26 months. The rates of recanalization and retreatment were, respectively, 12% and 6.4%. Older age, previously coiled aneurysms, larger aneurysms, incompletely occluded aneurysms, Neuroform stent, and aneurysm location were predictors of recanalization. Favorable outcomes were seen in 99% of elective patients and 51% of subarachnoid hemorrhage patients. Patient age, ruptured aneurysms, and procedural complications were predictors of outcome.

CONCLUSIONS

Stent-assisted coiling of intracranial aneurysms is safe, effective, and provides durable aneurysm closure. Higher complication rates and worse outcomes are associated with treatment of ruptured aneurysms. Stent delivery before coil deployment reduces the risk of procedural complications. Staging the procedure may not improve procedural safety. Closed-cell stents are associated with significantly lower recanalization rates.

Incomplete stent apposition in Enterprise stent-mediated coiling of aneurysms: persistence over time and risk of delayed ischemic events

OBJECT

Incomplete stent apposition of the closed cell-design Enterprise stent following stent-mediated coil embolization of intracranial aneurysms has been associated with increased risk of periprocedural thromboembolic events. In this study, the authors seek to determine the natural history of incomplete stent apposition and evaluate the clinical implications of the phenomenon.

METHODS

Since January 2009, all patients receiving Enterprise stents in the treatment of intracranial aneurysms at the authors' institution have undergone serial 3-T MRI with incomplete stent apposition identified by the crescent sign on multiplanar reconstructions of MR angiograms. Magnetic resonance images and MR angiograms obtained at 3, 9, and 18 months after stent-assisted coil embolization were analyzed along with admission and follow-up clinical medical records. These records were evaluated for any radiographic and clinical, transient or permanent ischemic neurological events.

RESULTS

Fifty patients receiving Enterprise stents were eligible for inclusion and analysis in the study. Incomplete stent apposition was identified in postoperative imaging studies in 22 (44%) of 50 patients, with 19 (86%) of 22 crescent signs persisting and 3 (14%) of 22 crescent signs resolving on subsequent serial imaging. Delayed ischemic events occurred in 8 (16%) of 50 cases, and all cases involved patients with incomplete stent apposition. The events were transient ischemic attacks (TIAs) in 5 cases, asymptomatic radiographic strokes in 2 cases, and symptomatic strokes and TIAs in the final case. There were no delayed ischemic events in patients who did not have incomplete stent apposition. Only 1 of the delayed ischemic events (2%) was permanent and symptomatic. The postoperative presence of a crescent sign and persistence of the crescent sign were both significantly associated with delayed ischemic events (p < 0.001 and p = 0.002, respectively).

CONCLUSIONS

Incomplete stent apposition is a temporally persistent phenomenon, which resolves spontaneously in only a small minority of cases and appears to be a risk factor for delayed ischemic events. Although further follow-up is needed, these results suggest that longer duration of antiplatelet therapy and clinical follow-up may be warranted in cases of recognized incomplete stent apposition.

Our capricious vessels: The influence of stent design and vessel geometry on the mechanics of intracranial aneurysm stent deployment

There is a growing interest in virtual tools to assist clinicians in evaluating different procedures and devices for endovascular treatment. In the present study we use finite element analysis to investigate the influence of stent design and vessel geometry for stent assisted coiling of intracranial aneurysms. Nine virtual stenting procedures were performed: three nitinol stent designs ((i) an open cell stent resembling the Neuroform, (ii) a generic stiff and (iii) a more flexible closed cell design), were deployed in three patient-specific cerebral aneurysmatic vessels. We investigated the percentage of strut area covering the aneurysm neck, the straightening induced on the cerebrovasculature by the stent placement (quantified by the reduction in tortuosity), and stent apposition to the wall (quantified as the percentage of struts within 0.2mm of the vessel). The results suggest that the open cell design better covers the aneurysm neck (11.0±1.1%) compared to both the stiff (7.8±1.6%) and flexible (8.7±1.6%) closed cell stents, and induces less straightening of the vessel (-5.1±1.6% vs. -42.9±9.8% and -26.9±11.9% ). The open cell design has, however, less struts apposing well to the vessel wall (56.0±6.4%) compared to the flexible (73.4±4.6%) and stiff (70.4±5.1%) closed cell design. With the presented study, we hope to contribute to and improve aneurysm treatment, using a novel patient specific environment as a possible pre-operative tool to evaluate mechanical stent behavior in different vascular geometries.

Cerebrovascular geometry in the anterior circulation: an analysis of diameter, length and the vessel taper

BACKGROUND

A study was undertaken to determine the typical length, diameter and taper of vessels in the anterior cerebral circulation.

METHODS

The sample size was calculated at 100 patients based on similar measurements in the literature and divided into cohorts based on gender and side. These patients were consecutively collected from a population that had undergone CT angiography and did not have any vascular abnormality. The arterial diameter was measured at the proximal cavernous internal carotid artery (ICA), the ICA terminus, the middle cerebral artery (MCA) origin and an M2 origin. The length between these endpoints was calculated along the center line. The vessel taper was calculated for the ICA as the change in caliber per unit length.

RESULTS

The mean length of the ICA from the proximal cavernous segment to the ICA terminus was 33.1 ± 6.1 mm. The mean diameter at the cavernous ICA and the ICA terminus was 5 ± 0.6 mm and 3.6 ± 0.4 mm, respectively. The mean ICA taper was 0.04 ± 0.02 mm/1 mm. For the MCA, the diameter at the MCA and M2 origins measured 3.1 ± 0.4 mm and 2.4 ± 0.4 mm, respectively. The mean MCA length was 22.5 ± 8.1 mm. There was no significant difference based on gender or between right and left sides. Patients aged >60 years had longer ICAs (p=0.02), larger cavernous ICA (p=0.003), ICA terminus (p<0.0001) and MCA origin (p=0.01) diameters than those aged 40-60 years. The ICA vessel taper did not change with age.

CONCLUSION

ICA and MCA vessel size did not change based on gender or side. Older patients had more redundant vessels based on diameter and length. The ICA has a gentle taper from its proximal cavernous segment to the ICA terminus. This information can be important in planning interventions or designing endovascular devices.