22 Chapter 1 rates were reported.298-300 Other authors, however, reported no difference in outcome with or without the use of balloons,276,301 this still being a subject of dispute in the neuro-interventional community.302,303 Third, stent-assisted coil embolization has made treatment of very wide-necked aneurysms and diffusely diseased segments of arteries possible.304,305 The microcatheter can be navigated through the pores of the stent into the aneurysm or can be trapped between the artery wall and the stent. It must be noted that the use of stents results in a higher complication rate306,307 and is therefore restricted to aneurysms which cannot be treated in any other way.277,308 Controversy exists about which is the best treatment for aneurysms that could in principle be treated by either neurosurgical clipping or endovascular coiling.309 An important study that tried to find a solution for this controversy was the International Subarachnoid Aneurysm Trial (ISAT).310 The initial findings of this trial, which were published in the Lancet in 2002, indicated that patients with a ruptured aneurysm and treated with endovascular coiling had lower mortality rate and better outcome after one year as compared to those treated with surgical clipping.194,311 The first reactions following these publications were critical, mainly addressing the selection of patients and the question of long-term results.312-320 For example, only a very small proportion of posterior circulation aneurysms were included in ISAT and critics warned that therefore the results of ISAT could not be extrapolated to the posterior circulation. However, the reason that so few posterior circulation aneurysms were included in the randomized study lay in the fact that endovascular treatment was already the preferred mode of treatment for these aneurysms.321,322 Furthermore, the results of endovascular coiling appeared to be sustained after five years: even though there was no longer a difference in outcome between the survivors of the two groups (endovascular and surgical), a small but significant difference in mortality remained.323,324 Several subgroup analyses were published establishing the advantages of endovascular treatment in most cases.325-329 Only in young patients were the advantages of coiling possibly offset by the higher rebleed rates observed in the coiled group,330,331 whereas in older patients with a middle cerebral artery aneurysm, clipping appeared to yield better outcomes.329,332,333 Despite the controversy the results of this trial had an enormous impact on the treatment of intracranial aneurysms and caused a shift to primary endovascular treatment273,334-342 to a variable degree in different regions and different hospitals.343-345 A Cochrane database review, largely based on data extracted from the ISAT study, led to the conclusion that: ‘we now have firm evidence that if the aneurysm is considered suitable for both surgical clipping and endovascular treatment, coiling is associated with a better outcome’.346 Apart from the randomized studies evaluated in the Cochrane database review, many observational and nonrandomized prospective studies were published; two reviews exist giving a practical overview of most of these.285,347 Later studies with various outcome parameters supported the results of ISAT.348-350 One of the latest additions is the Barrow Ruptured Aneurysm Trial (BRAT).351,352 In this study 472 patients were randomly assigned to a group that had clipping as the preferred treatment and a group that had coiling as the preferred treatment. If the assigned treatment was considered impossible or high risk, cross-over to the other treatment was allowed. When analyzed on ‘intention-to-treat’ as well as on actual treatment, endovascular treatment had a better one year outcome than clipping.
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