[Improved risk counselling possible for patients with unruptured intracranial aneurysms]

The 'International Study of Unruptured Intracranial Aneurysms' (ISUIA) investigators have recently published the results of a large prospective, observational study on risks of rupture and risks of treatment in patients with unruptured intracranial aneurysms. In patients with aneurysms smaller than 7 mm no rupture of the carotid, middle cerebral and anterior communicating arteries occurred during follow up (mean 4.1 years) if there was no history of subarachnoid haemorrhage from a separate aneurysm. Risks were higher in aneurysms of the posterior circulation (2.5% in 5 years), and in patients with a previous episode of subarachnoid haemorrhage from another aneurysm (1.5 to 3.4% in 5 years for aneurysms < 7 mm). Size was the most important risk factor for rupture, and aneurysms of the posterior circulation > 25 mm had a 50% cumulative risk of rupture over 5 years. The absence of rupture in some subgroups, such as small aneurysms of the anterior communicating artery, is probably explained by the small numbers in these subgroups. Similarly, the lack of identification of risk factors other than size is probably explained by insufficient power of the study. The overall risk (defined as death or dependence) of surgical treatment was 13%, with patient age and size and site of the aneurysm as the most important risk factors. Endovascular treatment carried a 7 to 10% risk in most subgroups; only patients with aneurysms > 25 mm had increased risks. Age was not a risk factor for endovascular treatment. By making use of these results, patients can now be given sound advice regarding the benefits of preventive treatment in each individual case.