Estimated low risk of rupture of small-sized unruptured intracranial aneurysms (UIAs) in relation to intracranial aneurysms in patients with subarachnoid haemorrhage

International guidelines for the management of unruptured intracranial aneurysms (UIAs) recommend observation in aneurysms < 10 mm due to the estimated low risk of rupture. The aim of our study was analyse the data of recently treated patients with ruptured cerebral aneurysms with the special focus on size and configuration in view of the frequency scale in a daily routine setting. We reviewed the data of all patients with aneurysmal subarachnoid haemorrhage (SAH) during the last 24 months at our institution. Configuration and size of the aneurysms were measured. Clinical data were collected using the following classifications for analysis: Hunt and Hess (H&H), modified Rankin Scale (mRS) and Fisher classification. Data of 135 patients with aneurysmal SAH (98 women, 37 men; ratio 2.6:1) were analysed. Analysis showed that 19 aneurysms (14 %) were > 10 mm (mean size, 19.2 mm) and 116 aneurysms (85.9 %) < 10 mm (mean size, 6.2 mm). In total, 112 were categorised as berry-like configured aneurysms (n = 113 < 10 mm, n = 3 > 10 mm), 18 as multi-lobar (n = 16 < 10 mm, n = 2 > 10 mm) and 5 as fusiform (n = 4 < 10 mm, n = 1, > 10 mm). Since the results of our study showed that the majority of the aneurysms are < 10 mm (mean, 6.2 mm), it is justified to challenge the recommendations of the international guidelines in a daily routine setting. We believe that the published data are not convincing enough to play a guidance role in daily routine. Due to improving surgical and endovascular techniques with satisfying results and the high number of ruptured small aneurysms, we believe a change in attitude in management of small-sized aneurysms is needed. Further diagnostic models are needed to determine the risk of rupture of intracranial aneurysms properly to obtain adequate treatment for UIAs.