The SILK flow diverter in the treatment of intracranial aneurysms

Abstract

The SILK flow diverter (SFD; Balt Extrusion, Montmorency, France) is a flow diverting stent used in the endovascular treatment of intracranial aneurysms. It works on the principle of redirecting flow away from the aneurysm sac, leading to occlusion over time. We present a systematic review on the clinical outcomes and complications of the SFD. A literature search for English language articles were conducted on PubMed, Medline and EMBASE for articles on the treatment of intracranial aneurysms with the SILK flow diverter. The inclusion criteria were n > 10, use of SFD only, data on complications and aneurysm occlusion rate (AOR). Eight studies with 285 patients and 317 intracranial aneurysms were included. The mean age was 52.7 years and nearly 80% were women. In terms of angiographic distribution, 86.8% of aneurysms were located in the anterior circulation and 13.2% in the posterior circulation. As for the aneurysm size, 37.9% were classed as small, 44.4% as large and 17.7% as giant. Ischemic complications and parent artery occlusion each occurred in 10% of patients. Aneurysm rupture rate was 3.5%, while the cumulative mortality was 4.9%. The main outcome measure, 12 month AOR, was 81.8% with complete occlusion in 216 out of 264 aneurysms. Use of flow diverters for the treatment of intracranial aneurysm with complex morphologies has gained in popularity over the last few years. Our review suggests that SFD achieves comparable AOR to its contemporary, the Pipeline Embolization Device (ev3 Endovascular, Plymouth, MN, USA) but has a higher rate of higher rate of ischemic complications, aneurysm rupture and mortality.

Introduction

Endovascular treatment of intracranial aneurysms with complex morphology such as giant, wide-necked or fusiform aneurysms is challenging. Previously, the preferred option was stent assisted coiling, which is associated with a high recanalization rate. Introduction of flow diverter stents has provided a promising alternative option for the repair of such aneurysms [1], [2]. By reducing flow across the aneurysm neck, flow diverters lead to aneurysm thrombosis, and by promoting neo-intimal growth they cause parent vessel reconstruction [3], [4]. In 2007, the SILK flow-diverting stent (SFD; Balt Extrusion, Montmorency, France) became the first such flow diverter entering clinical use for intracranial circulation. The SILK is made of 48 braided Nitinol strands that offer a high-coverage mesh once expanded, and is available in different diameters (2–5 mm) and lengths (15–40 mm) [5]. The SFD kit includes a self-expanding stent and a reinforced catheter (Vasco 21; Balt Extrusion) for its delivery. A distinct advantage of this delivery system in contrast to other stents is that it allows resheathing and repositioning, even when up to 90% of it has been deployed [5].

While it has not yet received regulatory approval in the USA for monotherapy, it is widely used as a stand-alone treatment in Europe. Initial results with the SILK stent suggested a promising rate of aneurysm occlusion, morbidity and mortality [5], [6], [7], [8] but recent reports have highlighted a higher risk of thromboembolic complications and delayed aneurysm rupture, especially following treatment of giant aneurysms [9], [10]. To the best of our knowledge there is no comprehensive article exclusively on the clinical outcomes of SFD. We present a systematic review of the published literature to evaluate aneurysm occlusion rates, mortality and procedure-related complication rates for intracranial aneurysms treated with the SFD.