Angiography and neurological examination are reliable tools for the identification of rupture in patients with multiple intracranial aneurysms. However, unusual presentation of rupture may cause the false localization of the ruptured aneurysm. We described two cases of bilateral internal carotid artery (ICA) aneurysms that were incorrectly positioned on CT scan. In the first case, CTA revealed bilateral IC-PC aneurysms. According to the localization of injured nerves and findings on radiograph rupture of left aneurysm was diagnosed. The patient suddenly became unconscious 24 h after operation. The cause of death was assumed to be the rupture of the right aneurysm. In the second case, CTA revealed IC-PC aneurysms. The diagnosis of a ruptured right IC-PC aneurysm was made based on neuroradiological findings. However, no rupture or bleeding was found during the operation. Thus the diagnosis of ruptured right IC-PC aneurysm was wrong. In the first case, disastrous re-bleeding occurred before the second operation for the ruptured one. In the second case, the patient died after we performed bilateral craniotomies at the same time. Misjudgment of rupture site by the CT scan resulted in clipping of the wrong aneurysm.

Key words: Bilateral intracranial aneurysm, rupture.