[Saccular aneurysm-like bleb formation after rupture of the internal carotid-posterior communicating artery aneurysm: a case with interesting angiographic findings].

A case of saccular aneurysm-like bleb formation after rupture of an aneurysm in the internal carotid-posterior communicating artery. In connection with this, an interesting angiographic finding was reported. A 65-year-old man suffered from sudden disturbance of consciousness and left hemiparesis. Computed tomography (CT) scan revealed typical subarachnoid hemorrhage localized in the right Sylvian fissure. Next day, a cerebral angiography was performed, but no aneurysm was detected. A second angiography was performed 21 days after the onset, and it revealed a saccular right internal carotid-posterior communicating artery (IC-PC) aneurysm. An operation for the IC-PC aneurysm was performed by conventional pterional approach. However, intraoperative findings were unexpected. The collapsed ruptured true IC-PC aneurysm was found at the orifice of the larger bleb, and the ruptured point was in the neck of the true aneurysm. Clipping of the aneurysm was performed successfully. The patient was discharged on foot. The aneurysm detected by the second angiography was not a true one but a bleb formation. Continuous hemodynamic stress on the rupture point may induce the formation of such an aneurysm-like bleb. It should be kept in mind that an aneurysm found in the chronic period might be an aneurysm-like bleb.