Materials and techniques for coiling of cerebral aneurysms: how much scientific evidence do we have?

Since coils were approved for aneurysm treatment, materials and techniques developed rapidly. It still remains an open question whether one material or method is superior. This article reviews the literature on various coil types and treatment approaches assessing the scientific evidence of its use.

Studies on aneurysm treatment with Guglielmi detachable platinum coils, bioactive coils, hydrogel coated coils, and complex designs as well as balloon- and stent-assisted techniques were retrieved by a PubMed database search from 1990 until May 2008. Data were analyzed in terms of aneurysm occlusion, permanent morbidity and mortality, recanalization, and retreatment. We also assessed the level of evidence of the published studies.

Only the International Subarachnoid Aneurysm Trial provides level I evidence proving the superiority of endovascular over surgical therapy in ruptured aneurysms. Randomized trials comparing bioactive or hydrogel coated devices with bare coils are ongoing. Other studies were based on registries or case series mainly conducted without control groups. Morbidity, mortality, and initial occlusion rates appear similar for all devices. No clear evidence exists for the superiority of bioactive- or hydrocoils regarding long-term stability. It remains ambiguous whether morbidity and mortality rises with the use of balloons and stents. There is no evidence that routine use of balloons improves treatment durability. Mid-term results of stent-assisted coiling of complex aneurysms appear favorable.

There is a lack of studies with a high level of evidence comparing different coiling materials and techniques. Case series and registries were not able to prove the superiority of any device or method.