Flow-diverting Stent (Pipeline Embolization Device) for Treating Unruptured Large and Giant Wide-necked Intracranial Aneurysms

Proprietary names: Pipeline® Embolization Device (PED) Generic names: aneurysm flow-diversion device, intracranial aneurysm flow diverter, flow-diverting endoluminal device

An intracranial aneurysm (IA) is an enlargement or ballooning of a blood vessel in the brain where the vessel wall is particularly weak. Clinicians classify aneurysms by size and shape; large aneurysms measure 11 to 25 mm in diameter, and giant aneurysms measure greater than 25 mm.1 An aneurysm has a wide neck (opening from parent vessel to the aneurysm) if the opening's diameter is greater than 4 mm or the dome (widest part of the aneurysm body) -to-neck ratio is less than 1.5.2 Wide-necked aneurysms can be saccular (i.e., also known as a "berry" aneurysm because it resembles a berry on a vine), fusiform (i.e., a widening of a vessel's walls), or dissecting (i.e., accumulation of blood between the layers of a vessel wall).3 Many conditions can contribute to aneurysm formation, including congenital or inherited conditions and environmental influences (e.g., atherosclerosis, hypertension, head trauma, infection).1 Left untreated, an IA may rupture, causing subarachnoid hemorrhage that can lead to severe functional disability, cognitive loss, and death.3 Some studies show that increasing aneurysm size may correlate with increased risk of rupture.4,5

Typically, IAs are asymptomatic until they become large or rupture.3,6 Large and giant aneurysms can cause symptoms by pressing on surrounding tissues and nerves (i.e., mass effect), which occurs in 70% to 75% of cases.3,7 Symptoms depend on the aneurysm's location and may include cranial nerve palsy, dilated pupils, vision changes, localized headache, pain above and behind the eye, and progressive weakness or numbness.1

Clinicians typically use imaging to diagnose aneurysms and assess treatment options for patients with unruptured IAs. Clinicians commonly assess aneurysms with intra-arterial angiography, which has high resolution and allows the clinician to construct a three-dimensional (3-D) image of the aneurysm and surrounding vasculature.8 However, transcatheter procedures are invasive and carry a small risk of serious complications.8 Noninvasive imaging techniques used to assess IAs include computed tomography angiography and magnetic resonance angiography; however, these techniques may not allow clinicians to finalize a treatment strategy.8

Clinical practice guidelines strongly recommend patients and clinicians consider treating large and giant aneurysms.8 Treatment options include observation with control of hypertension and/or smoking cessation if necessary, open microsurgery (e.g., clipping, trapping), and endovascular interventions (e.g., coiling with or without balloon or stent assistance, parent vessel occlusion, liquid embolic agents).1,9 Clinicians typically use patient and aneurysm characteristics to determine the best treatment option.4

Despite advancements in treating IAs, clinical outcomes for certain large and giant wide-necked aneurysms may be unsatisfactory.10 Some aneurysms may be challenging to treat with open microsurgery because of inflexible, calcified aneurysms walls; location in a difficult to access area; or a neck unsuitable for clip placement.11 Challenges for treating large and giant wide-necked aneurysms with endovascular coiling have included difficulty achieving adequate coil packing density and preventing coil migration. Inadequate coil density allows blood to enter the aneurysm, increasing rupture risk, and coils protruding into the parent artery may decrease blood flow.2 Some studies show the incidence of aneurysm recurrence after coiling may be as high as 30% to 50%.12

This report describes a novel endovascular approach to treating unruptured...