The Evolution of Flow-Diverting Stents for Cerebral Aneurysms; Historical Review, Modern Application, Complications, and Future Direction

Abstract

In spite of the developing endovascular era, large (15-25 mm) and giant (>25 mm) wide-neck cerebral aneurysms remained technically challenging. Intracranial flow-diverting stents (FDS) were developed to address these challenges by targeting aneurysm hemodynamics to promote aneurysm occlusion. In 2011, the first FDS approved for use in the United States market. Shortly thereafter, the Pipeline of Uncoilable or Failed Aneurysms (PUFS) study was published demonstrating high efficacy and a similar complication profile to other intracranial stents. The initial FDA instructions for use (IFU) limited its use to patients 22 years old or older with wide-necked large or giant aneurysms of the internal carotid artery (ICA) from the petrous segment to superior hypophyseal artery/ophthalmic segment. Expanded IFU was tested in the Prospective Study on Embolization of Intracranial Aneurysms with PipelineTM Embolization Device (PREMIER) trial. With further post-approval clinical data, the United States FDA expanded the IFU to include patients with small or medium, wide-necked saccular or fusiform aneurysms from the petrous ICA to the ICA terminus. However, IFU is more restrictive in South Korea than in United States. Several systematic reviews and meta-analyses have sought to evaluate the overall efficacy of FDS for the treatment of cerebral aneurysms and consistently identify FDS as an effective technique for the treatment of aneurysms broadly with complication rates similar to other traditional techniques. A growing body of literature has demonstrated high efficacy of FDS for small aneurysms; distal artery aneurysms; non-saccular aneurysms posterior circulation aneurysms and complication rates similar to traditional techniques. In the short interval since the Pipeline Embolization Device was first introduced, FDS has been firmly entrenched as a powerful tool in the endovascular armamentarium. As new FDS are developed, established FDS are refined, and delivery systems are improved the uses for FDS will only expand further. Researchers continue to work to optimize the mechanical characteristics of the FDS themselves, aiming to optimize deploy ability and efficacy. With expanded use for small to medium aneurysms and posterior circulation aneurysms, FDS technology is firmly entrenched as a powerful tool to treat challenging aneurysms, both primarily and as an adjunct to coil embolization. With the aforementioned advances, the ease of FDS deployment will improve and complication rates will be further minimized. This will only further establish FDS deployment as a key strategy in the treatment of cerebral aneurysms.

Treatment outcomes of large and giant intracranial aneurysms according to various treatment modalities

“…Aneurysm diameter should be over 15 mm, and only one FD is allowed in a single procedure. Moreover, the use of any detachable coil combined with FD is not permitted [25]. Therefore, patients with subarachnoid hemorrhage (SAH) were inevitably treated with coil embolization, surgical neck clipping, or PAO.…”

Three-dimensional aneurysm volume measurements show no correlation between coil packing density and recurrence

“…In the future, the importance of RRC or volume on aneurysm recurrence may become irrelevant with increased use of intra-saccular devices such as WEB (Woven EndoBridge) [ 47 ]. Intra-saccular devices are an alternative for wide necked aneurysms that are gaining increasing interest due to the advantage of not needing dual antiplatelet therapy after treatment.…”

Intracranial Fusiform and Circumferential Aneurysms of the Main Trunk: Therapeutic Dilemmas and Prospects

“…Urgent EVT was needed, and the acute dissection was resolved. Currently, FD with 24-55% metal coverage is a better option, and FD has revolutionized the treatment for unruptured chronic IFCAs and is used with caution in ruptured acute IFCAs (41,42). After FD deployment, IFCAs begin to form thrombi; endothelialization subsequently occurs.…”