Stent-Assisted Coiling of Intracranial Aneurysms Using a Nitinol-Based Stent (Neuroform Atlas): A Systematic Review and Meta-analysis

Thin-film NiTi intrasaccular implant with flaps for aneurysm treatments

Intracranial aneurysms are abnormal, balloon-like formations in the brain blood vessels. They carry a high risk of rupture, which can cause severe complications. Effective aneurysm treatments include reducing blood flow into the aneurysm sac. Coiling is an effective method of occluding the aneurysm sac. However, wide-neck aneurysms are associated with complications because large necks make it difficult to retain the coils securely in the aneurysm sac. This challenge can be overcome by using coil-assisting implants. This additional support avoids the risk of coils migrating into the parent artery avoiding such complications such as ischemic stroke. This study introduces a novel, coil-assisted implant design with flaps fabricated using micro-electromechanical system (MEMS) technology, which provides a higher degree of freedom in designing and prototyping. The designs contain a stable mechanical backbone with mobile thin flaps that allow secondary delivery of coils into the aneurysm sac. Mechanical tests are conducted to measure radial forces for secure anchoring in the aneurysm sac and compression forces to assess the hammering effect from pulsatile blood flow. Furthermore, the novel implants were tested and compared with a commercial braided implant in in-vitro environment using 3D-printed aneurysm models to understand their flow dynamics and coiling performance by using digital subtraction angiography. The findings showed that backbone/flap designs have greater mechanical stability, which enhances effectiveness compared to braided coil-assisting implants. Moreover, coiling was possible through mobile flaps, highlighting the potential for advancing the treatment of brain aneurysms.

Safety and Efficacy of the Neuroform Atlas Stent for Treatment of Intracranial Aneurysms: A Systematic Review, Meta-Analysis, and Meta-Regression

BACKGROUND

Intracranial aneurysms (IAs) are the major cause of subarachnoid hemorrhage. Stent-assisted coiling, especially with the Neuroform Atlas stent (NAS), has proved more effective than coiling alone for treating these aneurysms.

PURPOSE

To perform a systematic review and meta-analysis to investigate the efficacy and safety of the NAS in treating IAs.

DATA SOURCES

A comprehensive literature search was conducted on PubMed, EMBASE, Cochrane Central Register of Controlled Trials, and clinicaltrials.gov from inception until June 2024.

STUDY SELECTION

We included studies on ruptured and unruptured IAs treated with the NAS, covering experimental, observational, and case series across all age groups. The aneurysm occlusion rate was assessed by using the Raymond-Roy classification (RROC). The mRS and adverse events related to stent use were also recorded.

DATA ANALYSIS

The statistical analysis was conducted on R Version 4.3.2 by using the packages "meta" and "metasens." We reported our results as proportions with their corresponding CIs. Meta-regression, leave-one-out, and sensitivity analyses were conducted to confirm the robustness of our results.

DATA SYNTHESIS

A total of 42 studies including 2434 participants with a mean age of 51 to 73 years were included. Among angiographic outcomes, the final RROC 1/RROC 2 was achieved in 95% of the patients, final RROC 1 in 82%, RROC 2 in 12%, and RROC 3 in 5% of the patients. Additionally, 93% of the patients showed mRS grade 0, 5% showed mRS grade 1, 3% showed mRS grade 2, 2% showed mRS grade 3, 0% showed mRS grade 4, 0% showed mRS grade 5, and 1% showed mRS grade 6. All adverse events had a ≤5% rate.

LIMITATIONS

Due to limited cause-specific data, we were unable to analyze mortality specific to the stent placement and complications. Despite the large number of studies included, comparative studies were still observed to be scarce.

CONCLUSIONS

Although the generalizability of our findings is limited, this study demonstrates that the NAS is highly effective for treating IAs, with high occlusion rates and a low incidence of adverse events. The stent's performance, supported by comprehensive analysis, highlights its safety and efficacy in managing both ruptured and unruptured aneurysms.

Woven endobridge embolization versus microsurgical clipping for unruptured wide-neck cerebral aneurysms on middle cerebral artery bifurcation

Woven EndoBridge (WEB) is an endovascular treatment for wide-neck bifurcation aneurysms (WNBAs). This study aimed to clarify the efficacy and safety of the WEB comparing to clipping for treating the middle cerebral artery (MCA) WNBAs. For the matched analysis, we designed a retrospective, tertiary, single-center study including 288 MCA WNBAs treated with WEB (n = 37) or clipping (n = 251). Inverse probability of treatment weighting (IPTW) for the main analysis and 1:2 propensity score matching for the sensitivity analysis were used to adjust for aneurysm geometric parameters. Morbidity, major complications, and aneurysm occlusion grade were assessed at 1 year. In the IPTW analysis, no significant difference was observed in morbidity (2.1% vs. 1.6%, odds ratio [OR]: 1.34, p = 0.776) and major complications (3.3% vs. 3.1%, OR: 1.08, p = 0.926). Adequate aneurysm occlusion was achieved in 76.1% of the WEB group and 97.4% of the clipping group (OR: 0.09, p < 0.001). In line with the main analysis, the 1:2 propensity score matching analysis revealed no significant difference in the morbidity (OR: 2.00, 95% CI: 0.13-31.98, p = 0.624). This study supports that microsurgical clipping still requires to play a vital role, but WEB could be an alternative option for WNBAs in the MCA.

The "CUPCAKE" technique (coiled underlying pseudoaneurysm contained by a woven endobridge device) for treating intracranial aneurysms with atypical morphology

BACKGROUND

Intrasaccular flow diversion using the woven endobridge device (WEB; MicroVention, Aliso Viejo, CA, USA) for the treatment of intracranial aneurysms has demonstrated large scale safety and efficacy. However, limitations arise from its structural configuration, restricting its application to specific aneurysm sizes and shapes.

TECHNIQUE OVERVIEW

We introduce the CUPCAKE technique, a combination of conventional coiling followed by WEB intrasaccular flow disruption in select cases of atypical aneurysms with technically challenging morphology not typically treatable by WEB alone.

MATERIALS AND METHODS

A retrospective analysis of a prospectively-maintained dataset from three Australian neurovascular tertiary referral centers, identifying patients treated with the CUPCAKE technique between April 2018 and September 2023. Evaluation of patient and aneurysm characteristics, procedure parameters, complications, radiological and clinical outcomes at follow-up was performed.

RESULTS

The CUPCAKE technique was used for the treatment of 22 intracranial aneurysms of total 169 treated with WEB. Overall successful immediate flow stagnation was observed in 95.5% (n = 21) of aneurysms with no cases of perforation or intraoperative hemorrhage. Imaging confirmed thromboembolic complications occurred in two patients, one patient had persistent flow requiring re-treatment during initial admission. Follow-up imaging demonstrated 88.2% complete aneurysm conclusion with no delayed aneurysm expansion or rupture.

CONCLUSION

Synergistic use of conventional coiling with WEB intrasaccular flow disruption presents a viable solution for technically difficult aneurysm treatment. In our series, 13% of all patients treated with WEB received CUPCAKE treatment, resulting in high technical success and no increase in thromboembolic complications with the union of two methods.

Long-term results of wide-necked intracranial bifurcation aneurysms treated with stent-assisted coiling using low-profile acandis acclino stents

PURPOSE

Little data exists on endovascular treatment of complex intracranial aneurysms with the Acandis Acclino low-profile self-expanding closed-cell stent systems and is mainly limited to short- or midterm results. We report our long-term, single-centre experience with three generations of Acclino stents treating complex intracranial aneurysms.

METHODS

62 wide-necked intracranial aneurysms were treated electively using 88 Acclino stent systems. Single stent-assisted coiling was the preferred treatment in 38 cases and the kissing-Y stenting technique in 24 cases. We analysed demographic data and long-term follow-up results.

RESULTS

All stents were successfully deployed with immediate complete (Raymond Roy occlusion classification, RROC I) or near-complete occlusion (RROC II) achieved in 93,5%. Follow-up was available in 55 cases with a mean follow-up of 36 months (range 9-80 months). Long-term RROC I or II was achieved in 49 cases (89,1%). Three cases of stable residual aneurysmal filling were observed (5,5%). Seven aneurysms (12,7%) demonstrated a worsening on follow-up leading either to a neck remnant (4 cases, 7,3%) or to an aneurysm recurrence (3 cases, 5,5%). One recurrent aneurysm was retreated with coilembolization (1,8%). The directly procedural-related complication rate was 4,8%. Seven cases of clinically silent in-stent stenosis (12,7%; morbidity n = 0) were detected on long-term follow-up, six of them using the kissing-Y stenting technique.

CONCLUSION

Endovascular treatment of various intracranial aneurysms using the Acandis Acclino stent systems is safe and efficient with high aneurysm occlusion rates combined with low complication rates on long-term follow-up. Overall, rates of in-stent stenosis are low but may depend on the treatment technique (single stent-assisted coiling versus kissing-Y stenting with coiling).

Assessment of degradability and endothelialization of modified poly L-lactic acid (PLLA) atrial septal defect (ASD) occluders over time in vivo

OBJECTIVE

To evaluate the fiber-degradation and endothelialization of a modified poly L-lactic acid (PLLA) atrial septal defect (ASD) occluder for a long time in vivo.

METHODS

A total of 57 New Zealand rabbits were selected to establish the vasculature implantation model, which would be used to characterize the mechanical properties and pathological reaction of PLLA filaments (a raw polymer of ASD occluder). In total, 27 Experimental piglets were used to create the ASD model for the catheter implantation of PLLA ASD occluders. Then, X-ray imaging, transthoracic echocardiography, histopathology, and scanning electron microscope (SEM) were performed in the experimental animals at 3, 6, 12, and 24 months after implantation.

RESULTS

In the rabbit models, the fibrocystic grade was 0 and the inflammatory response was grade 2 at 6 months after vasculature implantation of the PLLA filaments. The mass loss of PLLA filaments increased appreciably with the increasing duration of implantation, but their mechanical strength was decreased without broken. In the porcine models, the cardiac gross anatomy showed that all PLLA ASD occluders were stable in the interatrial septum without any vegetation or thrombus formation. At 24 months, the occluders had been embedded into endogenous host tissue nearly. Pathological observations suggested that the occluders degraded gradually without complications at different periods. SEM showed that the occluders were endothelialized completely and essentially became an integral part of the body over time.

CONCLUSION

In the animal model, the modified PLLA ASD occluders exhibited good degradability and endothelialization in this long-term follow-up study.

Embolization of unruptured wide-necked aneurysms at the MCA bifurcation using the Neuroform atlas stent-assisted coiling: a two-center retrospective study

Background

The management of middle cerebral artery (MCA) aneurysms remains a controversial topic, and MCA aneurysms have traditionally been treated primarily by surgical clipping. The Neuroform Atlas Stent™ (NAS, available from Stryker Neurovascular, Fremont, California) represents the latest generation of intracranial stents with improved stent delivery system capabilities.

Objective

This study aims to investigate the safety, feasibility and efficacy exhibited by NAS in treating unruptured aneurysms at the MCA bifurcation.

Methods

This was a two-center retrospective study involving 42 patients with unruptured wide-necked aneurysms (WNAs) of the MCA treated with the NAS from October 2020 to July 2022.

Results

The stent was used to treat 42 cases of unruptured WNA at the MCA bifurcation. Endovascular treatment techniques had a 100% success rate. Immediate postoperative angiography found complete aneurysm occlusion in 34 patients (80.9%) (mRRC 1), neck remnant in 7 patients (16.7%) (mRRC 2), and residual aneurysm in 1 patient (2.4%) (mRRC 3). The thromboembolic complication rate was 2.4% (1/42). The follow-up period was 8.7 months on average (3-16 months). The last angiographic follow-up results revealed complete aneurysm occlusion in 39 patients (92.9%) (mRRC 1), neck remnant in 3 (7.1%) patients (mRRC 2), no aneurysm recanalization or recurrence, and no cases of stent intimal hyperplasia. During the latest clinical follow-up, all patients had an mRS score of 0.

Conclusion

Our study demonstrates that the NAS can be applied to treat unruptured WNAs at the MCA bifurcation with favorable safety, feasibility, and efficacy.

Additional rescue stenting with Neuroform Atlas stents during stent-assisted coiling of saccular aneurysms

OBJECTIVE

Overlapping stenting is sometimes attempted during endovascular treatment of cerebral aneurysm as a rescue for coil herniation, stent mal-positioning, or in-stent thrombosis. We retrospectively evaluated the efficacy and safety of additional rescue stenting (ARS) in telescoping fashion with Neuroform Atlas stent (NAS) during stent-assisted coiling of saccular aneurysms.

METHODS

We collected clinical and radiological data of patients with saccular aneurysms treated with ARS using NASs between March 2018 and December 2021. Y or X-stent-assisted coiling technique was excluded.

RESULTS

Eighteen unruptured and 5 ruptured aneurysms in 23 patients were treated with ARS using NASs. Sizes of aneurysms ranged from 2.0 mm to 10.0 mm (mean: 5.0 mm). Immediate angiographic results were complete occlusion in 11 aneurysms, residual neck in 4 aneurysms, and residual sac in 8 aneurysms. Peri-operative morbidity was 4.3 %. Nineteen of 23 patients underwent follow-up conventional angiography (mean, 9.9 months). Results showed progressive occlusion in 10 (52.6 %) cases and asymptomatic in-stent stenosis in 3 (15.8 %) cases. At the end of the observation period (mean, 17.4 months), all 18 patients without subarachnoid hemorrhage had excellent clinical outcomes (mRS of 0), except one (mRS of 1). Of five patients with subarachnoid hemorrhage, four had a favorable outcome (mRS of 0-1), while the other one was dependent (mRS of 4).

CONCLUSION

In this report on 23 patients, ARS with NASs for treating saccular aneurysms showed good technical safety with favorable clinical and angiographic outcomes. However, delayed in-stent stenosis was not uncommon. Thus, regular imaging follow-up is required.

Endovascular treatment of a supraclinoid internal carotid artery fenestration aneurysm: A case report and literature review

Supraclinoid internal carotid artery (ICA) fenestration aneurysm is rare. Except for open surgery, endovascular treatment (EVT) is considered an alternative for such an aneurysm. However, experience with this procedure is lacking. Therefore, we reported such a case. A 61-year-old woman suffered subarachnoid hemorrhage. Digital subtracted angiography (DSA) showed bilateral middle cerebral artery (MCA) aneurysms and a saccular aneurysm associated with fenestration of the supraclinoid ICA. Two MCA aneurysms were treated with single coiling, and the supraclinoid ICA fenestration aneurysm was coiled under stent assistance. The postoperative recovery was uneventful. At this time, a literature review was performed on the role of EVT in supraclinoid ICA fenestration aneurysms. A total of 13 supraclinoid ICA fenestration aneurysms treated by EVT in 11 cases, including our case, were obtained. After EVT, good outcomes were obtained in all cases. To our knowledge, this is the first study to review the role of EVT for supraclinoid ICA fenestration aneurysms. Our case report and literature review indicated that EVT for such aneurysms may be feasible and act as a therapeutic alternative.

A mini-review of intrasaccular flow diverters

Treatment of wide-necked complex intracranial aneurysms continues to challenge neurointerventionalists. Intrasaccular flow diverters have expanded the armamentarium considerably and are now used extensively. While five types of devices have already obtained the CE mark for use within Europe, only the Woven EndoBridge (WEB) device is approved by the US Food and Drug Administration. Other intrasaccular devices are the Luna/Artisse Aneurysm Embolization System (Medtronic), the Medina Embolic Device (Medtronic), the Contour Neurovascular System (Cerus), and the Neqstent Coil Assisted Flow Diverter (Cerus). This mini review will provide a compact overview of these devices and a summary of the current literature.

Small and Medium-Sized Aneurysm Outcomes Following Intracranial Aneurysm Treatment Using the Pipeline Embolization Device: A Subgroup Analysis of the PLUS Registry

Objective

The purpose of this work was to summarize the real-world safety and efficacy of Pipeline Embolization Device (PED) therapy for small and medium-sized intracranial aneurysms in China.

Methods

Patients from the PED in China post-market multi-center registry study (PLUS) with aneurysms smaller than 12 mm were selected. Radiographic outcomes were assessed using digital subtraction angiography. Clinical outcomes included functional outcomes (modified Rankin Scale, MRS) in the early postoperative period ( ≤ 30 days) and early postoperative complications associated with PED therapy.

Results

A total of 652 patients with a combined 754 aneurysms were included in this study (mean age of 53.9 ± 10.3 years, 68.7% women). Mean aneurysm diameter was 6.78 ± 2.67 mm. Of the 687 stents deployed, 99.7% (685/689) were successfully deployed. In this study, 64.7% (488/754) of aneurysms were treated with only the PED, whereas 35.3% (266/754) were subjected to PED-assisted therapy. Radiographic outcome at the last follow-up (median time: seven months) was available for 64.3% (485/754) of the aneurysms. 82.5% (400/485) of aneurysms demonstrated complete occlusion (Raymond Roy Grade I). 81.4% (395/485) of aneurysms were found to meet the study's primary effectiveness outcome. At the early postoperative period, the mRS score was determined to be 0–2 vs. 3-6 in 98.2% (640/652) vs. 1.8% (12/652) of the cases, respectively. The combined major morbidity and mortality rate was 3.2% (21/652).

Conclusion

In the largest study of PED therapy for small and medium-sized intracranial aneurysms to date, pipeline-assisted coil embolization was chosen more often than multiple stent implantation for aneurysm treatment, demonstrating good results, high surgical success rates, high occlusion rates, and low morbidity and mortality.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier: NCT03831672.

Application of the Neuroform Atlas Stent in Intracranial Aneurysms: Current Status

The Neuroform Atlas stent (NAS) is the successor of the Neuroform EZ stent. The NAS is compatible with a low-profile 0.0165-inch microcatheter and is soft enough to pass through small and highly tortuous vessels. The NAS can be used in treating intracranial aneurysms at almost all locations, and its use is becoming increasingly common. However, there has not yet been a complete review of NAS applications. Therefore, we performed this review, which addresses several aspects of the NAS, mainly including its characteristics, clinical trials of its application in treating aneurysms, deployment techniques for the device, the prognosis and complications of its application in treating aneurysms, and antiplatelet requirements associated with its use. Based on the evidence reviewed here, as well as our experience, we found that the NAS is a promising device for treating intracranial aneurysms, especially complex and distal aneurysms. This stent can also be used as a powerful tool to assist in rescuing coil migration, completing dual-stent reconstruction, and coiling aneurysms via a transcirculation approach. The device may require antiplatelet therapy at a lower dose and over a shorter period than other stents. The deployment of the NAS to assist in aneurysm coiling can yield good clinical outcomes and an acceptable rate of complications. Thus, the NAS is a promising device.

Comprehensive review of the recent advances in devices for endovascular treatment of complex brain aneurysms

The International Subarachnoid Aneurysm Trial (ISAT) showed superiority for endovascular treatment of ruptured aneurysms and technology has since moved on rapidly. Many approaches and technology now exist for the endovascular management of ruptured and unruptured intracranial aneurysms, which reflects their varied nature - there is no one-size-fits-all technique. We aim to provide an overview of the various classes of device and the major developments over the past decade. Coiling is the oldest of the technology and continues to demonstrate high levels of occlusion and acceptable risks, making it the default treatment choice, particularly in the acutely ruptured aneurysm setting. Advances on coiling include the use of adjuncts such as balloons, stents and fully retrievable temporary neck-bridging devices, which have facilitated the treatment of more complex aneurysms. Flow divertors have also revolutionised complex aneurysm treatment with small added risk in acute aneurysm treatment and seek to remodel the aneurysm-vessel interface without accessing the aneurysm sac. The latest development and most promising avenue appears to be intrasaccular flow disrupting devices like WEB, Contour and Neqstent that provide excellent opportunities to treat wide neck complex aneurysm with minimal mortality and morbidity and good occlusion rates and may in future replace a significant number of stent-assisted coiling too.

Results of watchful waiting of unruptured intracranial aneurysms in a Western patient population: a single-center cohort

BACKGROUND

The natural history of unruptured intracranial aneurysms (UIAs) in Western populations is still debated, especially for those <7 mm. Reporting data of a large single-center cohort managed with watchful waiting is therefore interesting.

METHODS

From January 2011 to June 2019, 662 UIAs were followed up by yearly MR angiography. Morphologically stable UIAs were managed conservatively while unstable UIAs were offered treatment. The patients' clinical and radiological data were analyzed retrospectively.

RESULTS

UIAs were ≤4 mm in 60%, 4.1-7.0 mm in 33%, and >7 mm in 7%. They were located on the anterior circulation in 90% of cases. The mean follow-up duration was 51.32 months for a total of 2831 aneurysm-years. During follow-up, 37 UIAs (5.5%) were treated because of an increase in size, and 8 UIAs were treated because of patient decision. Three aneurysms ruptured during follow-up for an annual risk of rupture of 0.1% (95% CI 0% to 0.24%). No risk factors for rupture were identified. The three ruptured cases made an excellent recovery. During follow-up, annual mortality from unrelated causes was 0.8% (95% CI 0.51% to 1.18%).

CONCLUSIONS

This single-center cohort evaluated our watchful waiting policy applied in two-thirds of all incidental UIAs. Morphological change of UIAs during follow-up led to treatment in 5.5% of cases. With such a management paradigm, we found a low rupture rate in these selected UIAs and the mortality was unrelated to aneurysms.

Efficacy and safety of PulseRider for treatment of wide-necked intracranial aneurysm-A systematic review and meta-analysis

OBJECTIVE

PulseRider is a novel self-expanding nickel-titanium (nitinol) stent for treatment of wide-necked aneurysms, which is commonly located at the arterial branches in the brain. This systematic review and meta-analysis aims to assess the efficacy and safety of PulseRider for treatment of wide-necked intracranial aneurysm.

METHOD

We performed a systematic literature search on articles that evaluate the efficacy and safety of PulseRider-assisted coiling of the wide-necked aneurysm from several electronic databases. The primary endpoint was adequate occlusion, defined as Raymond-Roy Class I + Raymond-Roy Class II upon immediate angiography and at six-month follow-up.

RESULTS

There were a total of 157 subjects from six studies. The rate of adequate occlusion on immediate angiography was 90% (95% CI, 85%-94%) and 91% (95% CI, 85%-96%) at six-month follow-up. Of these, Raymond-Roy Class I can be observed in 48% (95% CI, 41%-56%) of aneurysms immediately after coiling, and 64% (95% CI, 55%-72%) of aneurysms on six-month follow-up. Raymond-Roy Class II was found in 30% (95% CI, 23%-37%) of aneurysms immediately after coiling, and 25% (17-33) after six-month follow-up. Complications occur in 5% (95% CI, 1%-8%) of the patients. There were three intraoperative aneurysm rupture, three thrombus formation, three procedure-related posterior cerebral artery strokes, one vessel dissection, and one delayed device thrombosis. There was no procedure/device-related death.

CONCLUSIONS

PulseRider-assisted coiling for treatment of patients with wide-necked aneurysm reached 90% adequate occlusion rate that rises up to 91% at sixth month with 5% complication rate.