128 Chapter 7 studies, the incidence of recurrent subarachnoid hemorrhage after adequate coiling was significantly lower than after surgical clipping.17,18 The first imaging follow-up at six months appears to take place at a crucial point in time: if the coiled aneurysm is adequately occluded at this time, it is very likely that it will remain stable.1,9,10,19,20 However, extended imaging follow-up may be considered in patients with aneurysms larger than 10 mm, with aneurysms located on the basilar tip and with partially thrombosed aneurysms.21 Other factors may also play a role in decision making, such as young patient age, the presence of multiple aneurysms or family history of cerebral aneurysms. Since its introduction by Roy and Raymond in 2001, their three-point scale for describing the occlusion status of coiled aneurysms has been generally accepted.2 It served a simple purpose: to differentiate between complete occlusion (class 1), incomplete occlusion that does not require further treatment (class 2), and incomplete occlusion that may require further treatment, depending on other factors (class 3). The practical significance of making a distinction between R&R class 1 and class 2 is unclear although in many studies this level is used as cut-off point for dichotomized analyses.22,23 Only in some more recent publications have analyses been done with dichotomization between adequately occluded (R&R class 1 and 2) and inadequately occluded (R&R class 3) aneurysms.24-27 Only if R&R class 2 occlusions have a predictive value for later recanalization is there a rationale for this distinction. In this study and in the larger multicenter LOTUS study we did not find this predictive value. Conclusion Prolonged imaging follow-up within the first 5-10 years after coiling does not seem beneficial in patients with coiled aneurysms that are adequately occluded at 6 months, in terms of detecting recanalized aneurysms that need retreatment. Whether patients might benefit from screening beyond the 5- to 10- year interval is not yet clear. Occlusion status at six months follow-up of coiled aneurysms can be described as adequate or inadequate. References 1 Ferns, S. P. et al. Late reopening of adequately coiled intracranial aneurysms: frequency and risk factors in 400 patients with 440 aneurysms. Stroke 42, 1331-1337, (2011). 2 Roy, D., Milot, G. & Raymond, J. Endovascular treatment of unruptured aneurysms. Stroke 32, 1998-2004, (2001). 3 Molyneux, A. et al. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial. Lancet 360, 1267-1274, (2002). 4 Wiebers, D. O. et al. Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment. Lancet 362, 103-110, (2003). 5 Ferns, S. P. et al. Coiling of intracranial aneurysms: a systematic review on initial occlusion and reopening and retreatment rates. Stroke 40, e523-529, (2009). 6 Sluzewski, M. et al. Relation between aneurysm volume, packing, and compaction in 145 cerebral aneurysms treated with coils. Radiology 231, 653-658, (2004).
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