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Abstract
Objective To describe the treatment of posterior inferior cerebellar artery (PICA) aneurysms with the Low-profile Visualized Intraluminal Support Device (LVIS Jr) stent.
Materials and methods The databases of three institutions were retrospectively reviewed. Patients who underwent endovascular treatment of PICA aneurysms using a reconstructive technique where the LVIS Jr stent was totally or partially deployed into the PICA were included in the analysis. Clinical presentation, aneurysm and PICA sizes, procedural complications, and clinical and angiographic follow-up information was recorded and analyzed.
Results Seven patients who underwent endovascular treatment of PICA aneurysms with an LVIS Jr stent were identified. Four aneurysms were treated in the acute phase of subarachnoid hemorrhage (SAH). There were no symptomatic complications. One patient had spasm distal to the stent as a result of mechanical straightening of the vessel. One patient was treated in the acute phase of SAH and required a gycoprotein IIb/IIIa inhibitor after the stent was implanted. This patient needed to be re-treated to complete embolization. All patients had good clinical outcomes (Glasgow Outcome Scale 5). No in-stent stenosis or occlusion was seen on short-term angiographic follow-up and the aneurysms were occluded.
Conclusions This small series suggests that the use of a reconstructive technique with the LVIS Jr stent for the treatment of PICA aneurysms is feasible, safe and effective in the short term.
- Aneurysm
- Angiography
- Stent
- Subarachnoid
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Introduction
Posterior inferior cerebellar artery (PICA) aneurysms are uncommon, with a reported incidence of 0.5–3% of all intracranial aneurysms.1 Surgical and endovascular treatment of these aneurysms is often challenging. The proximity of important intracranial structures such as the brainstem and cranial nerves limits operative working space and makes microsurgical treatment technically challenging.2 Moreover, the small caliber of the PICA and the broad neck often associated with these aneurysms create unique challenges in preserving this artery during microsurgical and endovascular approaches.
Current endovascular techniques include primary coiling, stent-assisted coiling (SAC), balloon-assisted coiling (BAC), occlusion of the parent artery with coils or liquid embolic materials, and flow diversion. However, parent vessel sacrifice may lead to brainstem and cerebellar infarction. The aim of surgical and endovascular approaches should be to preserve the PICA and permanently occlude the aneurysm.
Low-profile stents that can be deployed through a 0.017-inch microcatheter are an excellent alternative for PICA reconstruction and SAC of PICA aneurysms. We describe a multicenter experience in the treatment of PICA aneurysms with the Low-profile Visualized Intraluminal Support Junior (LVIS Jr) stent (MicroVention, USA).
Materials and methods
An institutional review board at each institution approved retrospective analysis of prospectively acquired data. Inclusion criteria were the following: presence of a PICA aneurysm treated by placement of an LVIS Jr stent into the PICA.
We recorded the following baseline data: age, sex, neurologic examination before and after the procedure, angioarchitecture of the PICA and aneurysm, and clinical presentation, and follow-up data: the interval from the index procedure, aneurysm occlusion status, patency of the PICA, and neurologic examination.
Seven patients with PICA aneurysms were identified and treated with an LVIS Jr stent. Every case was discussed with a multidisciplinary team and endovascular treatment was deemed the best approach.
All procedures were performed under general anesthesia after informed consent was obtained from the patient and their family members. Endovascular treatment of the aneurysms was performed on a single plane or a biplane angiography unit (Allura Xper FD20, FD 20/10 or FD20/20; Philips Medical Systems, The Netherlands) depending on the institution.
Patients were on dual antiplatelet therapy for at least 5 days before the procedure, except for patients with an acute subarachnoid hemorrhage (SAH) who received a loading dose of 500 mg of aspirin and 300 mg of clopidrogel the day before the procedure. During the procedure all patients received systemic heparinization to achieve an activated clotting time greater than or equal to 250 s.
In general, a 6 F guide catheter was positioned in the V2–V3 segment of the vertebral artery (VA). The guide catheter was positioned depending on the angle of origin of the PICA for an ipsilateral or contralateral catheterization. If the PICA originated in an acute angle from the VA, the microcatheter catheterization was performed through the contralateral VA. A Headway 17 microcatheter (MicroVention, USA) was then navigated into the PICA and across the aneurysm with a 0.014 or 0.008 microwire. Once the microcatheter was positioned at least 0.5 cm distal from the aneurysm neck, the LVIS Jr stent was slowly deployed. In some cases once the LVIS Jr stent was deployed, the Headway microcatheter was advanced forward into the stent through the inner delivery wire of the stent to achieve correct wall apposition of the distal stent struts.
Once the stent was deployed, a 0.014 microwire was used to access the aneurysm with the Headway microcatheter. We then proceeded with coiling of the aneurysm.
Case 1
A patient in their early 20s presented with a SAH Fisher IV and World Federation of Neurological Surgeons Grading System for Subarachnoid Hemorrhage (WFNS) of 1. CT angiography demonstrated a proximal wide-neck right PICA aneurysm. The night before endovascular embolization, the patient received 500 mg of aspirin and 300 mg of clopidogrel. Digital subtraction cerebral angiography (DSA) demonstrated the presence of a dominant bi-hemispheric right PICA and a wide-neck aneurysm arising from the tonsilomedullary portion of the PICA (figure 1A). Due to the tortuosity of the PICA, a 0.008 Mirage microwire (ev3 Inc, USA) was used to cross the aneurysm and catheterize the distal portion of the PICA. The Headway microcatheter was then advanced and used to deploy a 3.5×23 mm LVIS Jr stent. The microcatheter was then pushed inside the stent through the inner delivery wire of the stent to expand the distal struts. Once the stent was completely opposed to the vessel wall, a 0.014 microwire was used to cross the stent struts and access the aneurysm’s sac for coiling. A gycoprotein IIb/IIIa inhibitor was initiated and maintained for 24 h to ensure stent patency since during the procedure slower blood flow through the PICA was noticed. A small aneurysm remnant was left and coiled in a second procedure (figure 1B, C).
A patient in their 20s presented with subarachnoid hemorrhage (SAH). (A) A three-dimensional angiogram demonstrated the presence of a lobular 10×6 mm posterior inferior cerebellar artery (PICA) aneurysm. The aneurysm had a wide neck and it was decided to place a stent for stent-assisted coiling (SAC). A 0.008 microwire was navigated inside the aneurysm and used to catheterize the distal PICA segment. (B) Follow-up angiogram after treatment showing complete occlusion of the aneurysm and modification of the angioarchitecture of the PICA. (C) Unsubstracted view showing the proximal and distal ends of the stent (arrows).
Case 2
A patient in their early 50s presented with a SAH Fisher IV and a WFNS of 1. A DSA demonstrated a fusiform aneurysm located in the telovelotonsillar segment of the PICA. The night before endovascular intervention the patient was loaded with dual antiplatelet therapy as described. The PICA was accessed with a Headway microcatheter and a 0.014 microwire. The aneurysm was crossed and a 3.5×23 mm LVIS Jr stent was placed along the fusiform segment of the PICA (figure 2A). It was decided not to place any coils in the hope of achieving flow diversion and reconstruction of the PICA with placement of the stent. A follow-up MRI at 1 month and a DSA at 1 year confirmed reconstruction of the PICA by the stent and obliteration of the fusiform aneurysm (figure 2B). The patient remained clinically intact on follow-up.
(A) Oblique angiogram demonstrating a fusiform aneurysm in the telovelotonsillar portion of the posterior inferior cerebellar artery (PICA). Notice the distal LVIS Jr struts. (B) One-year follow-up angiogram demonstrating complete aneurysm obliteration without the use of coils.
Results
Five women and two men were treated (table 1). Four patients were treated acutely due to SAH and three electively due to the incidental finding of the PICA aneurysm. In five patients, the PICA was catheterized from the ipsilateral side, while two patients required contralateral catheterization. We experienced two minor procedural complications. During coiling of the aneurysm in patient 3, slowness of blood flow through the PICA was noticed and it was decided to stop the procedure and start infusion of a glycoprotein IIb/IIIa inhibitor. Since most of the aneurysm was protected, the remnant was coiled in a second procedure 3 months later and without complications. In patient 5, transient vasospasm was noticed after placement of the stent and straightening of the PICA (figure 3).
Patient characteristics
A patient in their 60s presented with an unruptured right posterior inferior cerebellar artery (PICA) origin dissecting aneurysm. (A) Oblique right vertebral cerebral angiogram. (B) Roadmap image demonstrating straightening of the PICA with a 0.014 microwire. (C) Native image after stent-assisted coil embolization. (D) Vasospasm after stent deployment. (E) One-month follow-up demonstrates complete resolution of the spasm and total occlusion of the dissecting aneurysm.
All patients had angiographic follow-up (median 5.1 months). Patient 2 had no aneurysm regrowth at 6 months follow up. However, at 12-month follow-up, grade 3 recanalization was noticed and was treated with coiling.3
All patients had a good recovery and were able to return to their normal activities (Glasgow Outcome Scale 5).
Discussion
Aneurysms located in the anterior medullary, lateral medullary and tonsillomedullary segments of the PICA usually are not suitable for vessel sacrifice due to the presence of brainstem perforators.4 Therefore, endovascular approaches should aim to preserve the PICA at the time of aneurysm embolization. Small-neck aneurysms do not pose a challenge when they can be accessed for coiling. However, wide-neck and fusiform aneurysms may need reconstruction of the diseased segment of the PICA through SAC, BAC or flow diversion.
The deployment of the stent into the PICA can be performed through the ipsilateral or contralateral VA based on the angle of origin of the PICA and the size of the neck of the aneurysm. The choice of access also depends on the patency and caliber of the VA.5 Contralateral access for stenting in conjunction with ipsilateral access for coiling of the aneurysm might be considered in appropriate circumstances.6 The small diameter of the PICA may not allow jailing of a second microcatheter and the procedure may need a ‘one microcatheter’ approach. In this setting, the LVIS Jr delivery system may be extremely helpful in allowing both stenting and coiling with a single microcatheter. Moreover, a small caliber VA may only allow 5-F guide catheters, limiting endovascular options like jailing or BAC.
The LVIS Jr system offers several advantages in accessing and treating aneurysms located in small-lumen vessels. Most intracranial stents use stiffer 0.021 and 0.027 stent delivery systems not amenable for navigation into small-lumen arteries like the PICA. The LVIS Jr device is an excellent alternative to catheterize and reconstruct the PICA since it can be delivered through a 0.017-inch microcatheter. The system has proven to be effective in treating middle cerebral artery aneurysms and basilar tip aneurysms through SAC or even Y-stenting.7–9 Chalouhi et al described their experience in treating 76 PICA aneurysms: four patients underwent SAC with the Neuroform stent (Stryker-Neurovascular, USA) and in 1 patient the stent was not deployed due to PICA tortuosity.10 The authors highlighted the limitations of SAC and BAC in treating distal PICA aneurysms due to the small caliber of the PICA and unfavorable geometry. Similar studies have described the difficulty in treating wide-neck PICA aneurysms with SAC or BAC.11 ,12
The LVIS Jr stent can be used for SAC and in some instances as a flow-diverter alone. The sole presence of the stent struts within a dilated vessel segment like a fusiform aneurysm serves as a scaffold for endothelial growth (case 2, figure 2). Flow diversion has been successfully used in PICA reconstruction with a small 2×15 mm Silk device (Balt, France) and a ≤3 mm Pipeline Embolic Device (Covidien, USA).13 ,14 However, access to small and distal vessels is likely to be more difficult because flow diverters are delivered in a large and relatively stiff 0.027-inch microcatheter and tortuosity or sharp corners can pose serious challenges. Although the LVIS Jr is not a flow diverter, its smaller cell structure may improve flow diversion when compared to other currently available intracranial stents as has been illustrated in case 2.8
Another advantage of the LVIS Jr system is that there is no need to re-access the lumen of the stent or jail another microcatheter in the aneurysm in order to proceed with coiling, which in the case of a small-lumen PICA can be impossible. We used only one microcatheter for stenting and coiling. The braided wire structure enables the wire strands to slide over each other, allowing easy catheterization through the interstices.
The LVIS Jr is a hybrid closed-cell microstent composed of braided nitinol wires. When delivered in small vessels like the PICA, it may take some time to completely expand and the 0.017-inch microcatheter may have to be advanced through the inner delivery wire to achieve complete stent apposition. In addition, it is extremely important to partially open and recapture the stent before hooking it with the delivery hub, which facilitates opening of the struts at the time of deployment. The device is 80% resheathable and provides 15–18% surface area coverage. It is not uncommon to observe vasospasm after stent delivery since the stent may change the angioarchitecture of the PICA. However, in this small case series vasospasm was not symptomatic and responded well to intra-arterial infusion of calcium channel blockers.
PICA stenting has been described with self-expandable stents, mostly to preserve flow after treatment of VA dissection.5 In a series of seven patients described by Cho et al,15 wide-neck PICA aneurysms were treated with placement of an Enterprise stent (Codman, USA) from the PICA into the VA. Similarly, Chung et al16 described a series of 31 patients that included 9 PICA aneurysms that were treated with an Enterprise stent. Parent artery occlusion on follow-up was related to rectification of vessel tortuosity by the stent. The lower-profile LVIS Jr system appears to be a better alternative to conventional intracranial stents designed for larger-lumen vessels due to its easier navigability and better conformability because of its smaller size. Moreover, we did not document any parent vessel occlusion on follow-up, although the angioarchitecture of the PICA was modified after stent deployment.
In this case series we encountered two minor procedural complications. In patient 3 it was decided to interrupt coiling and start intravenous infusion of a glycoprotein IIb/IIIa antagonist. Cho et al described a similar complication when using Enterprise stents in SAC of PICA aneurysms. A glycoprotein IIb/IIIa antagonist was also administered to improve blood flow.15 It appears that the smaller caliber of the PICA and the hemodynamic flow rearrangements after stenting favor vasospasm and thrombosis.16 In cases where the treatment is performed acutely without proper dual antiplatelet inhibition, glycoprotein IIb/IIIa antagonists should be readily available once the aneurysm has been secured.
Despite high technical success rates, surgical treatment of PICA aneurysms is often challenging. Horowitz et al17 described a 68% postoperative complication rate in 34 patients who underwent surgical treatment of PICA aneurysms. Moreover, the unfavorable geometry of PICA aneurysms may require complex reconstructive microsurgical management. In a series of 47 PICA aneurysms treated with microsurgery, only 61% were treated with direct clipping, while the rest required proximal occlusion, wrapping and/or bypass.18 Microsurgery is an excellent alternative in managing these complex aneurysms and the treatment choice should be addressed by a multidisciplinary team.
In this small series, SAC of PICA aneurysms with the LVIS Jr stent was feasible and safe. The system provides adequate protection of the parent artery when the aneurysm has a wide neck or a fusiform configuration.
References
Supplementary materials
Abstract in Spanish
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- Abstract in Spanish - Online abstract
Footnotes
Contributors EAS: study concept and design, study supervision, administrative, technical and material support, and drafting of the manuscript; EAS and GD: analysis and interpretation of data; all authors: acquisition of data and critical revision of the manuscript for important intellectual content.
Competing interests RAH acts as a consultant for Covidien, Microvention, Stryker and Codman, is board member of Medina Medical, and holds stock in Blockade. GD is a consultant/proctor/speaker for Medtronic and MicroVention, and holds shares in Medina Medical and Surpass Medical.
Ethics approval The institutional review board at each institution approved this study.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Treatment protocols are available upon request to the corresponding author.