Introduction and historical background 23 This study supports the general opinion that, although coiling is the preferred treatment for cerebral aneurysms, the decision to treat by clipping or coiling should be made on a case-by-case basis. A few guidelines are given by recent publications, such as: • Wide necked aneurysms, aneurysms with arterial branches originating from the base of the aneurysm, patients with intracerebral hematoma, dissected vessels or acute brainstem compression, are better candidates for surgery. • Aneurysms closer to the midline and in the posterior circulation, or in patients with high age, poor neurological condition, medical comorbidity or vasospasm, are better candidates for coiling.347,353 Attempts have been made to design a paradigm for selecting treatment,354 but this selection remains subjective, often being based on preference and experience of the treating physician. Nowadays, in most centers in Western Europe and the US, the preferred treatment of intracranial aneurysms is coiling.343,344,355,356 As mentioned above, patients entering a hospital with a SAH in the last decade have better outcomes than in previous times,37,38 but it is difficult to say if this is the result of an increase in endovascular treatment.357-359 Brinjikji et al found that endovascular treatment of unruptured aneurysms increased the odds for better outcome.360 The same authors mentioned that, in the US, high-volume centers for treatment of intracranial aneurysms tend to perform endovascular treatment more frequently and have better outcomes in treating unruptured aneurysms,361 which leads us to another important question in the treatment of intracranial aneurysms. Should we preferably treat intracranial aneurysms in high-volume centers, where more endovascular procedures are performed and treatment delays are presumably shorter? Most authors, especially those in the US, declare that high-volume centers have better outcome in treating patients with aneurysmal SAH.362-368 The arguments for centralizing intracranial aneurysm treatment or management of patients with SAH are convincing. One such argument is that treatment in high-volume centers can be performed 24/7, an important advantage where timing is crucial for successful treatment, the reason to treat aneurysms in patients with SAH being the prevention of rebleeding of the ruptured aneurysm. The rate of rebleeding in untreated aneurysms is approximately 4% within the first 24 h, 1–2% per day over the next 14 days and 50% overall during the first 6 months.369 Very early rebleeds are near impossible to prevent due to the logistic unfeasibility of direct treatment after the first bleed as well as the risk of surgical morbidity when operating early on an acutely injured brain.370 The latter does not hold true for coiling.371 It was already noted in the ISAT study that the average time between rupture of the aneurysm and treatment was shorter in the endovascular than in the surgical group.194 For clipping, recent studies show that the advantage of preventing early rebleeding outweighs the disadvantage of early surgery.372,373 The present opinion is that aneurysm treatment should be performed as soon as possible to prevent rebleeding, which is more likely to be accomplished in high-volume centers.16,371,372,374-376 Although the positive effect of increased experience in endovascular treatment on patient outcome has been described377 the authors of the ATENA trial, which is concerned with treatment of unruptured aneurysms, found no difference in patient outcome after coiling between low and high volume centers,378 and several reports from small centers present outcome figures comparable with ISAT or other larger studies.379-385 In 2011 we presented the results of treating ruptured aneurysms in our relatively low-volume center,386 where we currently perform ca. 50 coiling and 20 clipping procedures a year.
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