Purpose Self-expandable stents have broadened the spectrum of endovascular treatment of intracranial aneurysms. However, procedures involving double stenting in Y/X configurations carry a relatively high risk of procedural complications. The Neuroform ATLAS, the evolution of Neuroform EZ, is a nitinol self-expanding hybrid/open cell stent which can be delivered through a low profile 0.017 inch catheter. We present our experience in the treatment of intracranial aneurysms with this stent in Y and X configurations.
Materials and methods We prospectively maintained a database from consecutive patients who underwent double stent assisted coiling with the Neuroform ATLAS, from July 2015 to February 2019. Clinical and angiographic results were analyzed.
Results 55 patients harboring 55 bifurcation aneurysms were treated with double stenting: 52 ‘Y’ configurations, 3 ‘X’ configurations. Deployment was successful in all cases. Post-treatment control angiography showed complete occlusion in 33 cases (60%), neck remnant in 8 cases (14.5%), and incomplete occlusion in 14 cases (25.4%). The overall symptomatic periprocedural complication rate was 12.7%. 38 aneurysms underwent follow-up (69%, mean duration 16 months): 33 aneurysms (87%) were completely occluded, 3 aneurysms (8%) had a neck remnant, and 2 aneurysms (5%) were incompletely occluded.
Conclusion The Neuroform ATLAS is an effective device for treatment of bifurcation aneurysms, allowing good conformability, a high level of navigability, and easy mesh crossing to perform Y/X stenting procedures. The rate of procedural complications remains non-negligible, and an indication for a double stenting procedure should be carefully discussed in a multidisciplinary meeting.
Statistics from Altmetric.com
Endovascular treatment with coils has become the main treatment modality of intracranial aneurysms1 2; the use of intracranial expandable stents now allows the treatment of bifurcation or wide neck aneurysms while preventing coil protrusion into the parent artery.3–5 A previous study reporting results of 216 aneurysms treated with stent assisted coiling (SAC) (most of which were treated with the Neuroform EZ stent) has even shown a significant decrease in aneurysm angiographic recurrence compared with simple or balloon assisted coiling, at the cost of increased morbidity and mortality.5 The Neuroform Atlas (Stryker Neurovascular, Fremont, California, USA), an evolution of the former Neuroform EZ, is a nitinol self-expanding, hybrid/open cell stent, presenting with a lower profile, allowing its delivery through a 0.017 inch compatible microcatheter (instead of a 0.027 inch microcatheter). It also offers improved navigability owing to its lower profile, which supposedly offers better conformability and stability, especially in tortuous vascular anatomy. Multiple previous case series, which mainly included patients treated with single stent assisted coiling, showed promising results.6–12 However, the full potential of this new tool lies in more complex procedures involving multiple stents in Y or X configurations: the Neuroform ATLAS stent is said to carry minimal risks of displacement or foreshortening, which should ease the deployment of a second stent through the first one.
The purpose of this retrospective study is to evaluate the safety and efficacy of this new device in Y and X configurations for double SAC.
The local ethics committee approved this research protocol. According to the French regulations, the board waived the need for signed consent for patients included in the study.
We have maintained an ongoing prospective database with demographic, angiographic, and clinical information of patients with intracranial bifurcation aneurysms treated by SAC with the Neuroform ATLAS from July 2015 to February 2019. Demographic data for each patient included age, gender, aneurysm status (ruptured or unruptured), location and dimensions, as well as clinical data on pre- and postprocedural clinical status. Wide neck aneurysms were defined by a neck size >4 mm and/or a dome to neck ratio of <1.5. Patient procedural characteristics included: number of stents used, stenting configuration (Y, X), timing of stent deployment (before or after coiling), procedure related morbidity and mortality, and clinical outcome at discharge and at the last follow-up. Procedural complications were divided in two categories: symptomatic complications (ie, complications that led to any temporary or permanent neurological deficit with a follow-up modified Rankin Scale (mRS) score of >2) and asymptomatic complications.
Aneurysm treatment strategies were initially discussed in a multidisciplinary meeting. All patients undergoing SAC began a dual antiplatelet therapy: either 250 mg aspirin+75 mg clopidogrel, starting 21 days before the procedure or 250 mg aspirin+90 mg ticagrelor twice a day, starting the day before the procedure. Platelet inhibition was tested by the Verify Now P2Y12 test (Accumetrics, San Diego, California, USA) the day before the endovascular procedure in the case of clopidogrel administration. Endovascular procedures were performed via the femoral approach, under general anesthesia and full anticoagulation with heparin (with a targeted activated clotting time at 2–3 times above the patient’s basic value). All procedures were carried out with a triaxial system, with a 6F 088 Neuron MAX Long Sheath 90/4 Straight (Penumbra, Alameda, California, USA); a Navien 6 F 105 cm (Covidien, Irvine, California, USA) or Fargo Max 105 cm (Balt, Montmorency, France) as the intermediate support catheter, and a 0.017 inch microcatheter (Excelsior SL-10 (Stryker, Fremont, California, USA), Headway 17 (MicroVention, Tustin, California, USA), or Echelon 10 (ev3, Irvine, California, USA)). In 51/55 cases (92.7%), the stents were deployed first and then they were crossed with the microcatheter used for aneurysm coiling. The stents were deployed after coiling in the remaining four cases. Heparin was discontinued immediately at the end of the procedure. In the case of bail-out stenting, an antiplatelet regimen was initiated with or without intravenous abciximab (Reopro) depending on the patient’s baseline therapy (see Results section). Dual antiplatelet therapy was continued for 3 months after the endovascular treatment, and a single antiplatelet therapy (250 mg aspirin) was continued for an additional 3 months.
Aneurysm occlusion was assessed by a neuroradiologist who was independent of the procedures performed, using the Roy–Raymond scale,2 immediately at the end of the procedure and at follow-up imaging (MRI at 6 months and DSA at 1–3 year).
Fifty-five patients with a total of 55 saccular bifurcation aneurysms were treated by SAC with the Neuroform Atlas stent during the study period, including 3 cases of bail-out (5.4%) and 3 cases of previously coiled aneurysms (5.4%).
The patient characteristics are summarized in table 1.
Aneurysm location and characteristics
There were 30 (54.5%) middle cerebral artery bifurcation aneurysms, 22 (40%) anterior communicating artery aneurysms, and 3 (5.4%) vertebrobasilar aneurysms.
Median (IQR) width of the aneurysms was 7.8 mm (6.8–9.8 mm) (min–max=2–20.7 mm). Median (IQR) neck size was 5.4 mm (4.6–6.6 mm) (min–max=2.1–10.2 mm). There were 52/55 wide neck aneurysms (94.5%).
The stent was deployed in two different configurations: Y stenting in 52 aneurysms (94.5%) and X stenting in 3 cases (5.4%). The stent was deployed before coiling in 51/55 cases (92.7%), after coiling in 1 case (1.8%), and in the bail-out technique in 3 cases (5.4%) because of coil protrusion.
Immediate angiographic results and follow-up
At the immediate post-treatment angiographic control, grade 1 (complete aneurysm occlusion) was achieved in 33/55 cases (60%), grade 2 (neck remnant) in 8/55 cases (14.5%), and grade 3 (incomplete occlusion) in 14/55 cases (25.4%).
Thirty-eight of 55 bifurcation aneurysms (69%) underwent follow-up imaging (mean follow-up period 16 months): 32 cases were controlled by 1 year follow-up DSA (mean follow-up 17.3 months) and 5 cases by 6 month follow-up MRI only (mean follow-up 7.8 months). Among the 38 aneurysms that underwent follow-up imaging, complete occlusion was observed in 33 cases (87%), neck remnant in 3 cases (8%), and incomplete occlusion in 2 cases (5%). An example of a wide neck left middle cerebral artery bifurcation aneurysm treated with Y stenting and coils is shown in figure 1.
Asymptomatic complications occurred in 5/55 cases (9.1%): there were 3 cases of temporary clot formation within the stents (all resolved with vasopressive drugs and/or infusion of abciximab) and 2 cases of slight stent dislodgement while attempting to cross the stents with a microcatheter in order to reach the aneurysm sac. All cases resolved without any neurological symptoms during follow-up.
Symptomatic complications occurred in 7/55 cases (12.7%), including 5 cases of ischemic complications (4 thromboembolic and 1 stent occlusion) and 2 cases of hemorrhagic complications. Regarding hemorrhagic complications, there were two cases of aneurysm perforation (one before coiling and one during coiling). Two of these symptomatic complications led to a permanent neurological handicap (mRS >2), the other symptomatic complications leading to an mRS score of 1 or 2. There were no mortalities. There was no case of delayed bleeding or delayed ischemic events at 6–12 months. Data on complications are summarized in table 2.
In our study involving only wide neck bifurcation aneurysms (the majority of which had an incidental finding (94.5%) treated under elective conditions, exclusively with the Neuroform ATLAS stent, using double stenting in the Y or X configuration, with a standard protocol of double antiaggregation and anticoagulation therapy, we found a high rate of technical success in terms of stent deployment and crossing, with satisfactory results of immediate and follow-up aneurysm occlusion (74.5% and 95%, respectively). However, the rate of symptomatic complication was non-negligible (12.7%), and although we experienced no cases of death, 2/55 patients (3.6%) suffered from procedural complications leading to a permanent neurological handicap (mRS >2).
Previous studies have shown high efficacy and safety with the Neuroform Atlas,6–12 however most patients described in these series were treated with a single stent, and the number of patients treated with multiple stents in the Y and X configurations ranged from 212 to 1811 (total 33 patients). More importantly, none of the studies reported complications with these complex procedures.6–12 Our experience with a large number of patients (55) confirms the satisfactory results previously reported in terms of technical and angiographic success: we had no cases of device deployment failure, only two cases of slight stent dislodgement during their crossing (with no clinical consequence), and the rates of aneurysm (near-)complete occlusion are comparable with previous results: an immediate adequate occlusion rate (complete occlusion or neck remnant) of 41/55 aneurysms (74.5%) and an adequate occlusion rate of 36/38 cases (95%) on follow-up imaging. The study by Cay et al 6 included 55 aneurysms (all treated with a single stent) with an adequate occlusion rate of 48/51 aneurysms (94.1%) at follow-up. The study of Ulfert et al 12 included 37 aneurysms (including two cases treated with Y stenting) with an adequate occlusion rate of 29/29 aneurysms (100%) at follow-up. The study of Ten Brinck et al 10 included 27 aneurysms (including 10 aneurysms treated in the acute hemorrhagic phase and 10 aneurysms treated with Y stenting) and reported an adequate occlusion rate of 18/26 aneurysms (69.2%) at follow-up.
SAC provides an efficient mechanical scaffold across the aneurysm neck that prevents coil protrusion into the parent vessels.13–15 The SAC technique is thought to promote a higher occlusion rate on follow-up compared with other endovascular techniques. Many studies5 16–18 show that complete occlusion (Roy–Raymond scale 1) with SAC can be achieved immediately in approximately 45% of cases. Until 2011, the deployment of self-expandable stents was possible through 0.021–0.027 inch delivery catheters only.13 15 19–22 Self-expandable braided stents such as the LEO Baby (Balt) and LVIS Junior (MicroVention) were introduced in 2011. These stents, deliverable through a low profile 0.017 inch microcatheter, allowed easier navigation and stent deployment in small sized vessels.3 14 18 According to previous studies reporting the results of SAC with low profile stents,23–27 a complete occlusion rate (grade 1) was achieved in 47–73% of cases with the LVIS Junior stent23 24 27 and in 56.6% of cases with the Leo Baby.25 26 An adequate immediate angiographic result (grade 1+2) was reported in 93% with the Leo Baby25 and in 79% in a recent meta-analysis.23 Our study shows comparable occlusion rates with the Neuroform Atlas stent.
SAC is known to significantly decrease the rate of recanalization and aneurysm retreatment compared with coiling.3 Progressive thrombosis promoted by SAC20 21 may be correlated with scaffolding that promotes the reconstruction of the aneurysm neck16 and/or with a hemodynamic/flow remodeling effect related to modification of the angle between the aneurysm neck and the parent vessels.13 19 22 In our series, a progressive occlusion rate was found in 85.7% and the mid-term recanalization rate was 7.8%.
SAC is generally associated with higher rates of complications compared with simple coiling or balloon assisted coiling techniques.4 18 In a case series of 105 aneurysms treated with Y or X SAC (mostly laser cut models), the rate of complications leading to a permanent neurological deficit was 10%.28 A previous meta-analysis of aneurysms treated by SAC with low profile self-expandable stents23 reported an overall procedure related complication rate of 12.4% (10.9% with the Leo Baby and 11.2% with the LVIS Junior). Our experience with the Neuroform Atlas stent in Y and X configurations has shown a similar proportion of procedure related adverse events: symptomatic complications occurred in 7/55 cases (12.7%), including 2 cases (3.6%) leading to permanent neurological handicap. It is noteworthy that we did not encounter any delayed complications of any type (delayed aneurysm bleeding or delayed ischemic complication). Other novel stents have recently been introduced, and their performance with wide neck aneurysms are promising.29 30 Further studies are necessary to determine the best endovascular tool for these aneurysms.
Our study has limitations inherent in its retrospective and monocentric observational design. Although our case series is, to our knowledge, the largest series with a focus on Y and X stenting with the Neuroform Atlas stent published so far, the overall number of patients remains relatively small, and larger sample studies are needed to determine the exact rate of symptomatic complications.
The Neuroform ATLAS is an effective device for treatment of intracranial bifurcation aneurysms, allowing good conformability, a high level of navigability, and easy mesh crossing to perform Y or X stenting procedures. The rate of procedural complications remains non-negligible, and an indication for a double stenting procedure should always be discussed in a multidisciplinary meeting.
Contributors GC: study design, data collection, data analysis, figure, tables, and writing. TR and SS: data collection, data analysis, and writing. RF, JPD, HR, SE, MM, and RB: data analysis and writing. MP: study design, data collection, data analysis, and writing.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial, or not-for-profit sectors.
Competing interests None declared.
Ethics approval The local ethics committee approved the research protocol. According to French regulations,the board waived the need for signed consent for patients included in the study.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Data, analytic methods, and study materials will be made available to any researcher for purposes of reproducing the results or replicating the procedure. Requests to receive these materials should be sent to the corresponding author, who will maintain their availability.
Patient consent for publication Not required.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.