Abstract
To clarify the optimal timing of surgical or endovascular treatment for patients with small-sized (<5 mm) unruptured intracranial aneurysms (UIA) with conventional follow-up, we retrospectively evaluated the characteristics of UIA that ruptured or enlarged during observation. From 1999 to 2014, 316 UIA (271 cases) were initially treated without surgical or endovascular intervention. Four ruptured and 17 grown UIAs were treated with clipping or coil embolization. In these cases, the ratio of the internal carotid to the posterior communicating artery and that of the anterior cerebral artery to the anterior communicating artery was 71%. Intraoperative findings revealed that the bleb formed during follow-up was observed as a very thin wall. Ruptured UIAs are prone to rapid growth. We conclude that location, growth rate, and bleb formation are useful to estimate the risk of rupture of smallsized UIAs during follow-up.
