Review
Endovascular techniques for the management of wide-neck intracranial bifurcation aneurysms: A critical review of the literature

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Summary

Endovascular treatment is the first line treatment for intracranial aneurysms, but wide-neck aneurysms are often difficult to treat due to the difficulty in stabilizing the coils inside the aneurysm. It is singularly true for wide-neck bifurcation aneurysms (WNBA) as bifurcation branches often arise from the aneurysm neck. To overcome these difficulties, several approaches are available to treat both ruptured and unruptured aneurysms (balloon-assisted coiling and intra-aneurysmal flow disruption), while some techniques are essentially restricted to unruptured aneurysms due to the need of concomitant use of antiplatelet medications (stent-assisted coiling and flow diversion). Several ways of performing balloon-assisted coiling have been proposed for WNBA. Two stent-assisted techniques are available for WNBA (Y-stenting and the waffle-cone technique), but these techniques have yet to be evaluated in large, prospective series. Off-label use of flow diverters in WNBA has been proposed but efficacy has still to be established, and the technique presents unique potential safety issues (the potential modifications of bifurcation branches covered by the flow diverter) that has to be assessed. Intrasaccular flow disruption devices are promising tools for the endovascular treatment of WNBA. The WEB device has been extensively evaluated with prospective, multicenter studies showing high safety and good efficacy.

Introduction

The overall prevalence of intracranial aneurysms is estimated as 3.2% in a population without comorbidity [1]. Most aneurysms are sacciform and are anatomically classified in 2 groups: sidewall and bifurcation aneurysms. In both groups aneurysm neck can be narrow (< 4 mm) or wide (≥ 4 mm).

After the publication of International Subarachnoid Aneurysm Trial (ISAT) results, coiling became progressively the first line treatment for ruptured and unruptured aneurysms [2], [3], [4], [5]. However, a limitation of the coiling treatment became rapidly obvious in wide-neck aneurysms due to the high risk of coil protrusion in the parent vessel. Subsequently, another limitation became evident, which was the relatively high rate of aneurysm recanalization, this phenomenon having a higher frequency in wide-neck bifurcation aneurysms (WNBA). These 2 limitations prompted the development of more complex endovascular techniques, such as balloon-assisted coiling, stent-assisted coiling, flow diversion, and flow disruption [6], [7], [8], [9], [10], [11], [12], [13].

The endovascular treatment (EVT) of WNBA is singularly difficult as it is necessary to simultaneously stabilize the coils in the aneurysm sac and preserve the permeability of the different branches of the bifurcation. The latter are frequently arising from the aneurysm neck making endovascular (and also surgical) treatment technically difficult. This subgroup of aneurysms includes aneurysms located at ICA terminus, MCA bifurcation, anterior communicating artery, and apex of the basilar artery. Different strategies and tools have been progressively developed over time for the EVT of WNBA. In the present review, these techniques and devices are described and their clinical and anatomical results analyzed. The pertinent literature was collected with a systematic research of papers dealing specifically with the treatment of WNBA.

Section snippets

Balloon remodeling (or balloon-assisted coiling)

This technique is probably the more frequently used in the treatment of ruptured WNBAs and also plays an important role in the management of unruptured WNBAs.

The use of a balloon temporarily inflated in front of the neck rapidly emerged as an effective approach especially for the treatment of wide-neck sidewall aneurysms [6]. For WNBAs, the use of this technique was more complicated to use, as it was mandatory to close completely the aneurysm neck and to protect the different branches of the

Stent-assisted coiling

This technique is frequently used singularly for the treatment of unruptured WNBA.

Flow diverters

Flow diverters are low-porosity stents designed to reduce hemodynamic exchange between the aneurysm and the parent artery, which promotes thrombosis within the aneurysm sac. In addition, flow diverters should provide scaffolding for neointimal overgrowth over the aneurysm neck (Fig. 5) [10]. After the positive results of Pipeline for Uncoilable or Failed Aneurysms (PUFS) trial, Pipeline Embolization Device (PED; Medtronic/Covidien, Irvine, California, USA) was approved by FDA and European

Intrasaccular devices (flow disruption)

Flow disruption is a new endovascular approach, which involves placement of an intrasaccular device. Placed in the aneurysm sac, the device will modify the blood flow at the level of the neck and induce aneurysmal thrombosis with a mechanism of action relatively similar to intravascular flow diversion. One device (WEB, Woven EndoBridge, Sequent Medical, Aliso Viejo, California, USA) is available for clinical use in Europe and South America and was widely evaluated in retrospective and

Conclusion

EVT of WNBA is challenging. Several techniques are now available for the treatment of WNBA, including balloon-assisted coiling, stent-assisted coiling (Stenting and Y-stenting, Waffle-cone technique), flow diversion, and flow disruption. Some of these techniques are essentially indicated for the treatment of unruptured (or recanalized) aneurysms as they involve the placement of the device in the parent vessel that needs to be accompanied with antiplatelet treatment (stent-assisted coiling and

Disclosure of interest

LP: proctoring/consulting contracts with Medtronic-Covidien Neurovascular, Microvention, Neuravi, Sequent.

AB: proctoring/consulting contracts with Balt, Medtronic-Covidien Neurovascular, Microvention, Stryker Neurovascular, Phenox.

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