General discussion 151 aneurysms per year.53 High volume centers in Europe treat a larger percentage of aneurysms through coiling than medium- and low volume centers.53 Brinjikji et al. showed that centers treating a higher percentage of unruptured aneurysms with coiling than with clipping achieve markedly lower rates of morbidity and mortality.57 From a cost-effectiveness perspective, Bardach et al. determined that patients in the US benefited from transfer from low-volume centers to high-volume centers with a net gain of roughly $2,200/quality life year.58 These findings have prompted the amendment of the AHA guidelines for the management of aneurysmal SAH: ‘Low volume hospitals should consider early transfer of patients with aneurysmal SAH to high volume centres…’.3 Proposal 7. Patients with intracranial aneurysms should preferably be treated in centers with the highest possible volume where both endovascular and neurosurgical treatment options are available on a 24/7 basis. Follow-up As pointed out in Chapter 6, follow-up of coiled intracranial aneurysms can be done reliably with MRA. Although the advantages of contrast enhanced MRA (CEMRA) have not (yet) been convincingly demonstrated, we use both time of flight (TOF-MRA) and CEMRA sequences in our hospital. When a recanalization is found which may require retreatment, an additional DSA study is performed in most cases in order to confirm the recanalization and guide further management (retreatment or prolonged follow-up). In addition, we perform a scheduled follow-up of all coiled aneurysms at six and 24 months after treatment. From the many studies presented in Chapter 1 it becomes clear that the first follow-up at six months is crucial: the majority of recanalizations and rebleeds occur within this time frame.59-62 Later rebleeds are rare and incomplete occlusion of the coiled aneurysm directly after coiling is a strong predictor of recanalization and rebleed after the follow-up at six months.19,63-66 The risk of a late rebleed, either from the treated aneurysm or from additional or de novo aneurysms, is very low in patients with aneurysms that are adequately occluded at six months.19,63,67-72 The yield of long term follow-up of patients with adequately occluded aneurysms at six months, in terms of recanalizations needing treatment, is very low.73 Even before the results of the LOTUS study were known, the suggestion arose to limit prolonged follow-up to patients with an incomplete aneurysm occlusion at six months.74 The results of the LOTUS study strongly supported this limitation. Proposal 8. Coiled aneurysms that are adequately occluded at six months do not require longer follow-up. The mean length of follow-up in the LOTUS study was six years.73 We cannot yet predict if the risk of new aneurysm formation or recanalization of the treated aneurysm increases after this period. Thus it appears that evaluation at six months should define future patient management. Based on the findings at six months, it must be decided whether any aneurysm needs further treatment, whether the patient should be followed for a longer period or whether the patient is stable and does not need further surveillance. In addition, new aneurysms and growing additional aneurysms must be detected and treated or must receive prolonged surveillance.75,76
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