[A case of a ruptured anterior communicating aneurysm which was originally the smallest of several unruptured aneurysms].

A 64-year-old male suddenly developed headache and nausea. He had been pointed 3 years before out as having an unruptured basilar artery aneurysm and a right middle cerebral artery aneurysm. Computed tomography (CT) revealed diffuse subarachnoid hemorrhage in the basal cistern and bilateral Sylvian and interhemispheric fissures. Hematomas in the anterior horns of the lateral ventricles and third ventricle were also seen. Angiography revealed an anterior communicating artery aneurysm, which, retrospectively, had been recognized as a small dilatation of artery wall 3 years before. An operation was performed and the anterior communicating artery aneurysm was successfully clipped. The intraoperative findings revealed the aneurysm was the ruptured one. The risk of rupture and surgical indication for unruptured small aneurysms are discussed.