Two-stage reconstructive overlapping stent LEO+ and SILK for treatment of intracranial circumferential fusiform aneurysms in the posterior circulation

Abstract

Intracranial circumferential fusiform aneurysms of the posterior circulation involving arterial branches or perforating vessels are difficult to treat. This article shows an endovascular reconstruction technique not yet described, using a telescoping self-expandable stent (LEO+) and flow-diverter device (SILK) at different surgical times. Two patients with circumferential fusiform aneurysm, one being an aneurysm of the segments P2 and P3 of the posterior cerebral artery, diagnosed after a headache, and the other a partially thrombosed aneurysm of the lower basilar artery, diagnosed following ischemia of the brain stem. Endovascular treatment was performed by means of a vascular reconstruction technique that used at different surgical times: overlapping; a telescoped self-expandable stent, LEO+; and a flow-diverter device, SILK. Angiographic control was carried out at 6 and 12 months, to evaluate arterial patency, flow maintenance in the arterial branches and perforating vessels, and thrombosis of the aneurysm. The combined use at different surgical times of the self-expandable stent and flow-diverter device was technically successful in both patients. There were no complications during the procedure, nor in the long-term follow-up with full arterial vascular reconstruction, maintenance of cerebral perfusion and complete aneurysm occlusion at the 6- and 12-month angiographic follow-up. There was no aneurysm recanalization nor intra-stent stenosis. Circumferential fusiform aneurysm of the posterior circulation involving arterial branches or perforating vessels to the brain stem may be treated with this arterial reconstruction technique at different surgical times, using the self-expandable stent called LEO+ and the flow-diverter device SILK, minimizing the risk of complications and failure of the endovascular technique, with the potential for arterial reconstruction with thrombosis of the aneurysmatic sac, as well as flow maintenance in the eloquent arteries, in this type of cerebral aneurysm.

Introduction

Fusiform aneurysms are non-saccular dilations that involve the entire vessel wall in a given arterial segment, for a short distance. In the presence of a larger, circumferential length involving >180° of the vessel wall, they are called cylindrical or circumferential aneurysms.¹ These aneurysms are rarer; however, their diagnosis has increased in the last few years and may account for 3–13% of all the most commonly found intracranial aneurysms in the posterior circulation.²

Fusiform aneurysms have a multivariate physiopathogenesis, so they may originate following dissection; atherosclerosis; collagen and elastin disorders; infection; or rarely, from neoplastic infiltration, as well as due to unknown factors. This type of aneurysm may present clinically in several forms, ranging from meningeal hemorrhage, intracerebral hemorrhage, neurological deficit from cerebral ischemia; to dizziness, cranial nerve deficit from mass effect, or incidental findings.³ There are few reports on the treatment of fusiform aneurysms. When these aneurysms involve lateral arterial branches or perforating vessels that must be kept pervious, the therapeutic strategy is difficult to define and a particular challenge for neuroradiologists and neurosurgeons.

Case reports

Case 1

A 27-year-old female patient presented with highly intense headache. Computed tomography (CT) scan evidenced a hypercaptant and regular image, next to the brain stem. Figure 1(a) shows the lateral left internal carotid artery angiography, without the posterior communicating artery. Angiography and 3-dimensional (3D) angiography of the vertebral basilar system (Figure 1(b), (c) and (d)) shows a large, circumferential, fusiform aneurysmatic dilation of segments P2 and P3 of the left posterior cerebral artery, which was 18 mm long and measured 9 mm× 9.5 mm at its largest diameter. Treatment was decided upon: A vascular reconstruction technique with the associated use of a self-expandable stent and flow-diverter device, at different surgical times.

Figure 1.

Case 1. (a) Lateral left internal carotid artery angiography, without posterior communicating artery; (b) and (c) Angiography in PA and profile with circumferential fusiform aneurysm of the left posterior cerebral artery P2 and P3, with 18 mm in length and a circumference of 9 mm× 9.5 mm; (d) 3D angiography. (e) Angiographic follow-up at 3 months after the implantation of two stents: LEO+ 2.5 mm× 25 mm and 2.5 mm× 18 mm. (f) Image without bone subtraction, demonstrating good visualization of the overlapping LEO+ stents and eSILK. (g) and (h) Late angiographic follow-up in PA and the profile at 6 and 12 months, demonstrating a total reconstruction of the left posterior cerebral artery, without recanalization of the aneurysm and without intra-stent stenosis.

3D: three-dimensional; PA: posteroanterior projection.

First surgical time period

The patient was started on double antiplatelet therapy 3 days before the procedure. General anesthesia was used. A long 6F IVA introducer (Balt, Montmorency, France) was positioned into the V2 segment of the left vertebral artery. A Fargo Max 6F catheter (Balt, Montmorency, France) was positioned into the V4 segment of the left vertebral artery. A Vasco 10 microcatheter (Balt, Montmorency, France) was positioned distally into the P4 segment of the left posterior cerebral artery, with the aid of a Traxcess 14 microguidewire (Microinvention, Tustin, CA, USA), followed by the release of the first stent, a LEO+ of 2.5 mm× 25 mm (Balt, Montmorency, France). Because the aneurysm was not fully covered, it was decided to implant a second telescoped stent LEO+ of 2.5 mm× 18 mm (Balt, Montmorency, France) over the whole aneurysm length, with dye stagnation being observed within the aneurysmatic sac by angiographic control done at the end of the procedure.

Second surgical time period

The next surgery was 3 months later, keeping the double antiplatelet therapy and a control angiography with a subtotal thrombosis of the aneurysm and arterial reconstruction (Figure 1(e)). General anesthesia was used. A long 6 F IVA introducer (Balt, Montmorency, France) was positioned into the V2 segment of the left vertebral artery. A Fargo Max 6 F (Balt, Montmorency, France) catheter was positioned into the V4 segment of the left vertebral artery. Angiographic control showed evidence of an aneurysm sub-occlusion with partial arterial reconstruction. A Vasco 21 microcatheter (Balt, Montmorency, France) was positioned into the P4 segment of the left posterior cerebral artery, with the aid of a Traxcess 14 micro-guidewire (Microinvention, Tustin, CA, USA), and a flow-diverter device SILK 2.5 mm× 25 mm (Balt, Montmorency, France) positioned and implanted to overlap the two LEO+ stents (Balt, Montmorency, France), covering the whole aneurysm length, and the image without bone subtraction demonstrated good visualization of those overlapping LEO stents + e SILK (Figure 1(f)). Angiographic controls at 6 and 12 months showed full arterial reconstruction of the posterior cerebral artery and full elimination of the aneurysm (Figure 1(g) and (h)). The patient evolved no complications.

Case 2

A 19-year-old male patient presented with clinical conditions of sudden headache, vertigo with loss of balance, and total right hemiparesis. Symptoms receded as days went by. A magnetic resonance imaging (MRI) exam evidenced an image suggesting a partially thrombosed aneurysm of the low basilar artery, with a hypersignal of acute ischemia of the brain stem (Figure 2(a)). Angiography was done in both the internal carotid and in the lateral view, without good posterior communication (Figure 2(b) and (c)). Both the angiography and 3D angiography gave evidence of a partially thrombosed, large and complex circumferential fusiform aneurysm of the low basilar artery, which was 22 mm long and 11 mm× 11 mm at its larger diameter, with involvement of two vertebral arteries, as well as the anterior and inferior cerebellar arteries (AICA) (Figure 2(d), (e) and (f)).

Figure 2.

Case 2. (a) Axial MRI T2 with ischemia of brain stem right and expansive lesion with thrombus in its suggestive interior partially thrombosed aneurysm of the basilar artery. (b) and (c) Angiography in lateral view internal carotid artery right and left are before treatment, without good posterior communications. (d) and (e) Angiography in PA and a profile showing long fusiform circumferential complex aneurysm of the low basilar artery, involving the two vertebral arteries, as well as the previous two cerebellar arteries (AICA). (f) The 3D angiography. (g) Angiographic immediate control of the first procedure with the vertebral artery after implantation of two stents, LEO+ 3.5 mm× 30 mm and 3.5 mm× 25 mm, in the basilar and right vertebral artery. (h) Angiography of the left vertebral artery after occlusion with a detachable Gold Balloon and platinum microcoils, showing no perfusion of the aneurysm and perfusion of the left posterior cerebellar artery (PICA). (i) Image without bone subtraction, demonstrating good visualization of the overlapping LEO+ and SILK stents. (j) and (k) Angiographic follow-up in PA, and profile at 6 and 12 months, demonstrating a total reconstruction of the basilar artery without recanalization of the aneurysm and without intra-stent stenosis, with flow maintenance with the right AICA and occlusion of the left AICA without clinical deficits.

3D: three-dimensional; AICA: anterior and interior cerebellar arteries; MRI: magnetic resonance imaging; PA: ?; PICA: perfusion of the left posterior cerebellar artery

First surgical time period

The patient was started on double antiplatelet therapy 3 days before the procedure. General anesthesia was given. A long 6 F IVA introducer (Balt, Montmorency, France) was positioned into the V2 segment of the right vertebral artery. A Fargo Max 6 F catheter (Balt, Montmorency, France) was positioned into the V4 segment of the right vertebral artery. A Vasco 21 microcatheter (Balt, Montmorency, France) was positioned distally into the left posterior cerebral artery with the aid of a Traxces 14 microguidewire (Microinvention, Tustin, CA), followed by release of the first stent, LEO+ of 3.5 mm× 30 mm (Balt, Montmorency, France). Because the aneurysm was not fully covered, we chose to implant a second telescoped stent, LEO+ of 3.5 mm× 25 mm (Balt, Montmorency, France), to cover the whole aneurysm length. Dye stagnation was observed within the aneurysmatic sac by angiographic control, at the end of the procedure (Figure 2(g)).

A Long 6 F IVA introducer (Balt, Montmorency, France) was repositioned into the V2 segment of the left vertebral artery. A Fargo Max 6F catheter (Balt, Montmorency, France) was positioned into the V4 segment of the left vertebral artery. A microcatheter with detachable Gold balloon B1 (Balt, Montmorency, France) was positioned into the V4 segment of the left vertebral artery, above the posterior inferior cerebellar artery (PICA) and with release of the detachable balloon. Microcatheterization of the left vertebral artery with Echelon 14 microcatheter (Covidien Ev3, Irvine, CA, USA) and Traxcess 14 microguidewire (Microinvention, Tustin, CA, USA) and final occlusion of the left vertebral artery was done with platinum microcoils (02). Angiographic control evidenced full occlusion of the left vertebral artery with maintenance of flow through the PICA artery (Figure 2(h)).

Second surgical procedure

This was done 3 months later, keeping double antiplatelet therapy. We used general anesthesia. A long 6F IVA introducer (Balt, Montmorency, France) was positioned into the V2 segment of the right vertebral artery. A Fargo Max 6F catheter (Balt, Montmorency, France) was positioned into the V4 segment of the right vertebral artery. Angiographic control evidenced aneurysm sub-occlusion with partial arterial reconstruction. A Vasco 21 microcatheter (Balt, Montmorency, France) was positioned distally into the P4 segment of the left posterior cerebral artery, with the aid of Traxcess 14 microguidewire (Microinvention, Tustin, CA, USA), and the flow-diverter device SILK 3.5 mm× 30 mm (Balt, Montmorency, France) was positioned and implanted overlapping the two LEO+ stents (Balt, Montmorency, France). Angiographic control showed there was no enwrapping of the aneurysm for the full length, so we chose to place a second telescoped flow-diverter device, SILK 3.0 mm× 20 mm (Balt, Montmorency, France), which covered the aneurysm for the full length and the image, without bone subtraction, demonstrated good visualization of the overlapping stents, LEO+ e SILK (Figure 2(i)). Angiographic controls at 6 and 12 months showed the basilar artery reconstruction and full elimination of the aneurysm (Figure 2(j) and (k)). Arterial flow through the right anterior inferior cerebellar artery was kept; however, contralateral AICA was occluded, with its territory being supplied by pial anastomosis of the PICA, without any ischemic event observed clinically or by control MRI. The patient progressed without any complications.

Discussion

Fusiform aneurysms, particularly the circumferential ones involving the arterial wall in > 180°, with arterial branches or perforating vessels to the brain stem and that are symptomatic, are still a challenge.

Treatment of aneurysms of the P2 and P3 segments of the posterior distal cerebral artery is challenging for performing the surgical technique due to: The difficult access, the involvement of perforating vessels of the brain stem, the extensive anastomotic vascular network of that region, as well as the risk of injury of cranial nerves (nerves III and IV);^4–6 as well as the circumferential fusiform aneurysms of the basilar artery involving its branches, with variable clinical symptoms related to its course, due to the compressive effect, ischemia or rupture. Existing data indicate that non-saccular vertebrobasilar aneurysms have a poor natural history, as well as that their surgical treatment has poor results.^2,7

Fusiform aneurysms of the vertebrobasilar junction and basilar artery are lesions in need of a complex surgical approach, and are difficult for the performance of arterial bypass or arterial wall reconstruction. Endovascular treatment of this type of lesion with the use of stents and microcoils has been described for long sections, even with the risk of occlusion of the perforating vessels, which is also common with this surgical procedure.⁸ This combined technique using stents and microcoils may significantly reduce aneurysm recurrences as seen by angiographic follow-up in the long term; however, a higher association with increased morbidity and fatal complications was observed, when compared with the use of microcoils without stents.⁹

With the evolution of intracranial stents, low-porosity, self-expandable stents with better navigability into intracranial arteries started to be used in fusiform aneurysms of the basilar artery, reaching remarkable results with aneurysm healing and arterial remodeling.^10,11 In-vitro evaluation has shown that aneurysms of the basilar artery may be treated by redirecting the flow vortex in the arterial lumen; and these changes may create a favorable environment for aneurysm thrombosis, without the need of using microcoils.¹² Intracranial stents have anatomical action by the arterial reconstruction, functional action with the modification of the flow within the aneurysm, and a biological action with neointimal growth over the aneurysm neck.¹³

Fusiform aneurysms located in the P2 segment of the posterior cerebral artery have been treated with the endovascular technique, through occlusion of the aneurysmatic sac and the proximal portion of the P2A segment of the posterior cerebral artery, with the use of platinum microcoils following occlusion testing.¹⁴

The treatment of fusiform aneurysms, using exclusively self-expandable stents or balloon-expandable stents, has been described; however, there were poor results and partial aneurysmatic occlusion on the long-term angiographic follow-up.^15-17

Another technique in endovascular treatment of fusiform aneurysms was the use of the self-expandable stent with a balloon catheter expanded at the time of the microcoil placement, to prevent prolapse within the vessel; however, this may increase the risk of complications with the temporary occlusion of arterial branches and perforating vessels.^18,19

The exclusive use of the self-expandable stent was depicted as an option for fusiform aneurysms of the P2 segment of the distal posterior cerebral artery.²⁰

The use of a stent may minimize cerebral perfusion in the territory of perforating vessels, with an increased risk of cerebral infarction when placed over perforating arteries.²¹ Nevertheless, the use of the single stent in intracranial arteries is, in general, considered as safe with regard to occlusion of the perforating vessels, as this type of device may reduce flow through the perforating arteries by as much as 15%.²²

In-vitro studies have shown that the use of three low-profile, telescoped stents, or flow-diverter stents, reduces flow rates through the perforating vessels by as much as 46%; however, the risk of infarction or ischemia occurs when there is a higher than 50% reduction in the perforating vessel flow.^23,24

In the post-procedural analysis of diffusion-weighted magnetic resonance imaging (DWI) of aneurysms treated with a flow-diverter implant at 24 h, 48 h and after 3 months, showed that a greater quantity of ischemic and asymptomatic micro lesions (DWI spots) were noticed distal to the managed arterial segment (86%), which revealed an increase in embolic events with the use of these devices, which may be related to their mechanical properties or their handling during the procedure, but that have not been shown to be statistically significant in a multivariable analysis.²⁵

The endovascular technique with the approach in different stages of the same aneurysm is already being described as a more efficacious technique for the treatment of aneurysms with the need of using stent in patients not on antiplatelet aggregation drugs, or even when there is the need of stabilizing the stent with its endothelialization and adherence to the arterial endothelium, in wide-necked aneurysms.^15,26

More recently, the development of flow-diverter devices is an alternative to the treatment of wide and giant aneurysms, wide-necked aneurysms, as well as relapsing aneurysms; with the aim of achieving a quick flow reduction that, in its turn, leads to aneurysm sac thrombosis, as shown in animal experiments.²⁷

A recent multicenter report shows major interest in the use of flow-diverter devices for the treatment of intracranial aneurysms, mainly the giant ones and fusiform aneurysms; however, there was a high complication rate in 21.5% of the patients, which may be related to the learning curve with the novel method. Most of these complications occurred in complex, previously non-treatable aneurysms of the posterior circulation.²⁸

The hemodynamic change within the aneurysmatic sac, as well as thrombosis, have been described as a cause of fatal aneurysm rupture following the implant of flow-diverter devices.²⁹ Thrombosis occurring within the aneurysmatic sac may cause inflammation of the perianeurysmal brain tissue, with symptomatic worsening after implantation of flow-diverter stents.³⁰ After a flow diverter implant, occlusion of lateral branches with an estimated diameter of 0.5–1 mm may be immediate or occur at long term, and may be or not associated to neurological deficit.³¹

The use of flow-diverter devices was already described for treating circumferential fusiform aneurysms of the posterior circulation; however, what causes a certain confusion in results is that in the two described cases, aneurysms were previously treated with microcoils and/or self-expandable stent, without aneurysm thrombosis having occurred, and so it was decided to use the flow diverter.³²

Currently, there seems to be a trend to use flow-diverter devices as the treatment of choice for aneurysms defined as complex, such the fusiform, circumferential and giant aneurisms of the posterior circulation, even with the risk of fatal rupture or occlusion of lateral vessels with ischemic events.²⁹

In a multicenter experiment, a trend was shown towards the use of flow diverters in giant, complex, and fusiform aneurysms; with a technical complication rate in 21.5% of the cases. This rate was probably also related to the learning curve of the relatively novel method; in addition, complications occurred more frequently in complex aneurysms of the posterior circulation, considered as non-treatable until recently. However, the occlusion rate in early angiographic controls at 3 months was shown to be high in 85% of the aneurysms.²⁸

In the two cases presented here, aneurysms were fusiform and circumferential, both with the potential involvement of perforating vessels to the brain stem, with the aneurysm of the basilar artery being even more complex, due to the involvement of two vertebral arteries and the AICA, making still more difficult the therapeutic strategy. The endovascular treatment option with the associated use of the self-expandable stent, LEO+ (Balt, Montmorency, France), and the flow-diverter device, SILK (Balt, Montmorency, France), at different surgical times starting with the implant of that self-expandable LEO+ (Balt, Montmorency, France) stent, and waiting for a time period between 3 and 4 weeks later for the performance of a second procedure for the overlapping or telescoped implant of the SILK flow-diverter device (Balt, Montmorency, France) was chosen for the following reasons:

1. To prevent migration of the self-expandable stent to within the aneurysm when passing the microguide, microcatheter or even the flow-diverter device;

2. To wait 3–4 weeks for the endothelialization of the self-expandable stent, making handling it safer to implant SILK (Balt, Montmorency, France) at a second surgical time;

3. To provide a potential slow and partial thrombosis of the aneurysmatic sac, even before the SILK (Balt, Montmorency, France) implant, minimizing the risk of fatal aneurysm rupture;

4. To provide partial arterial reconstruction, with the possibility of pial arterial anastomosis emergence in the event of involvement with occlusion of the lateral or distal arterial branches before implantation of SILK (Balt, Montmorency, France); and

5. To improve accuracy in the choice of the flow diverter device size, providing improved adherence to the proximal and distal arterial walls, with improved anchorage of the same, since the stent contact surface decreases in circumferential fusiform aneurysms and may cause greater shrinkage of the flow diverter.

Conclusions

Treatment of circumferential fusiform aneurysms of the posterior circulation is still a big challenge for neurosurgeons and neuroradiologists. Arterial reconstruction with the use of flow-diverter devices seemed to be a good option for the treatment of this type of aneurysm; however, a concern about occlusion of the lateral arterial branches and perforating vessels still exists, with the risk of neurological deficit and death due to fatal aneurysm rupture. Due to the complexity of most of these lesions, the possibility of treating them with a technique combining the use of a self-expandable stent and flow-diverter device, overlapping or telescoped, at different surgical times with a 3–4 week time interval, may reduce the risk of morbidity and mortality, as well as the risk of technical failure. The present technique was shown to be feasible; however, a greater number of cases would be required, as well as a long-term angiographic follow-up, in order to define the sustained feasibility of the technique.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship and/or publication of this article.