Neuroradiology 2008 50 909 927 DOI 10 1007 s00234 008 0446 y INVITED REVIEW Materials and techniques for coiling of cerebral aneurysms how much scientific evidence do we have W Kurre J Berkefeld Received 11 June 2008 Accepted 7 August 2008 Published online 19 September 2008 Springer Verlag 2008 Abstract Introduction 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 Materials and methods Studies on aneurysm treatment with Guglielmi detachable platinum coils bioactive coils hydrogel coated coils and complex designs as well as balloonand 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 Results 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 W Kurre J Berkefeld Department of Neuroradiology University of Frankfurt Schleusenweg 2 16 60528 Frankfurt Germany e mail wiebke kurre kgu de Conclusion 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 Keywords Endovascular aneurysm therapy Aneurysm coiling Scientific evidence Introduction Endovascular treatment of intracranial aneurysms evolved with the introduction of Guglielmi detachable platinum coils GDC in 1992 1 The first generation of helical GDC coils was followed by coils with different caliber softness and 3 dimensional instead of helical shape memory Nowadays several manufacturers provide a wide range of coil designs with or without bioactive or other coatings and adjunctive tools like balloons and stents were optimized for intracranial use and assistance of coiling procedures Technical improvements increasing experience and clinical studies widened the indication for endovascular therapy and raised the question how far these techniques are based on scientific evidence One of the pillars of evidence based medicine is systematic evaluation of the quality and results of published clinical studies Commonly a grading system is applied using levels of evidence LOE with level I reserved for randomized controlled trials and level V for expert opinions not supported by scientific investigations see Table 14 in Appendix for an overview In between we find a wide range of study designs including cohort studies case control studies and case series with gradually decreasing levels of evidence 2 It was the aim of this analysis to review the literature reporting clinical and angiographic 910 results of endovascular coiling procedures to define the scientific basis of currently available well established and widespread materials and techniques Emerging new concepts of aneurysm repair like liquid embolics and flow diversion devices were not included in this review Materials and methods Evaluation of GDC treatment in ruptured and unruptured aneurysms We first evaluated the International Subarachnoid Aneurysm Trial ISAT publications representing level I evidence in GDC treatment of cerebral aneurysms For additional information on initial treatment results complication rates permanent morbidity and mortality long term stability and retreatments we performed a PubMed search with the key words cerebral aneurysm and coiling and cerebral aneurysm and endovascular treatment and GDC from 1990 until May 2008 With the large amount of literature available we included only systematic reviews and larger case series with more than 100 treated aneurysms Case series not clearly indicating the type of coil or case series using several different types of coils were omitted for this part of the analysis Neuroradiology 2008 50 909 927 Evaluation of balloon remodeling Articles on balloon assisted coiling of cerebral aneurysms were analyzed putting a special focus on the morbidity and mortality of the treatment Publications were found via PubMed using the key words remodeling balloon assisted balloon remodeling balloon and aneurysm All articles found were cross checked for additional information Evaluation of stent assisted coiling Data on stent assisted coiling procedures were found by a PubMed database search with the terms stent assisted coiling Neuroform Enterprise Leo or Solo recently renamed Solitaire and aneurysm to cover all available stents approved for aneurysm treatment Case reports with less than ten cases were omitted for analysis of treatment feasibility permanent morbidity and mortality and long term stability as well as retreatment rates as far as data were available All advanced coiling materials we refer to within the text or in the table are summarized in Table 15 in Appendix to facilitate the overview Results Evaluation of bioactive and coated coils GDC treatment of ruptured and unruptured aneurysms Results of the ongoing randomized trials on bioactive coils are not yet published Therefore were performed a PubMed search with the key words Matrix Cerecyte Nexus or fibered coil in combination with aneurysm limited by human to gather information on the currently commercially available products References of the articles were cross checked for additional publications We analyzed the articles with respect to permanent morbidity and mortality initial treatment results and long term stability including recanalization rates retreatments and rebleeding rates as far as available For safety and feasibility data of HydroCoils we
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