Treatment options of unruptured intracranial aneurysms.

Abstract

Aneurysmal subarachnoid hemorrhage (SAH), despite improvements in surgical and medical treatment, is still a serious disease with high rates of case fatality (40% to 50%) and morbidity.1–3 Incidence rates of SAH have not changed during the CT era, and outcome of SAH has only modestly improved during the past few decades. Outcome is still determined mainly by severity of initial bleeding or early rebleeding.1–4 It seems that identification of preventive treatment methods for aneurysm rupture and of modifiable risk factors for SAH are important as means to influence incidence and outcome of this serious disease. Unruptured aneurysms, when incidentally discovered or found in connection with diagnosis of ruptured aneurysm (multiple aneurysm cases), have been operated on for 2 to 3 decades in western countries. In this way, the high case fatality and morbidity associated with a possible severe initial bleed can be eliminated by preventive surgical intervention. However, the natural history as well as risks of surgery of unruptured intracranial aneurysms are poorly known as are the risk factors for rupture because of lack of studies with sufficient number of patients and follow-up years. The Table shows cohorts of largest studies of rupture risk of unruptured intracranial aneurysms.4–8 The recently published prospective part of The International Study of Unruptured Intracranial Aneurysms (ISUIA; patient enrollment in 61 centers between 1991 and 1998)5 shows somewhat different results as compared with those of the retrospective part of ISUIA (in 53 centers between 1970 and 1991).7 In the prospective study,5 overall incidence of aneurysm rupture was higher (0.8% versus 0.3% per year); risk for rupture of vertebrobasilar aneurysms was lower (relative risk 2.3 versus 5.1 to 13.8 as compared with other aneurysms); mean follow-up time per patient was shorter (3.9 versus 8.3 years); there was a lower limit …