[Natural history and management of asymptomatic unruptured cerebral aneurysms]

Natural history of asymptomatic unruptured cerebral aneurysms (AUCAs) still remains unclear. The concern on the natural history is incidence of rupture that was thrown into confusion with the report by International Study of Unruptured Intracranial Aneurysm Investigators (ISUIA) published on the New England Journal of Medicine in 1998. The annual rupture rate of AUCAs of our series was 1.1%. The study of Unruptured Cerebral Aneurysm Study of Japan (UCAS Japan) is now on going. Management modalities for AUCA includes surgery, intravascular treatment, and conservative treatment. Optimal treatment still remains under discussion. We first consider surgery for AUCAs, second intravascular treatment, and third conservative treatment. Our surgical indications are as follows: 1) patient's age is under 75 years old, 2) aneurysm locates in the anterior circulation, and 3) aneurysm size is over 5 mm. For patients with conservative treatment, periodic observation with magnetic resonance angiography is required. When aneurysm size increases with or without bleb, surgical or intravascular treatment should be considered. Our management strategy provides satisfactory results in patients with AUCAs. It is important to select the best treatment among those three modalities. In management of AUCAs, good surgical result (no mortality and low morbidity) are required for neurosurgeon.