[A successfully treated case of a ruptured anterior wall aneurysm of the internal carotid artery (C2) which changed in form from blister-like to saccular type].

We successfully treated a case of ruptured anterior wall aneurysm of the ICA (C2) which changed in form from blister-like to saccular type. A 46-year-old woman developed subarachnoid hemorrhage on July 12, 2002. Cerebral angiogram demonstrated a blister-like aneurysm located in the left C2 portion of the internal carotid artery, but which didn't affect the arterial branches. Because of the risk of premature rupture during early surgery, delayed surgery was scheduled and the patient underwent serial study of the aneurysm. During 2 weeks of follow-up, the shape and size of the aneurysm changed in form blister-like to an enlarged saccular type aneurysm. On the day 18th, a left episubcombined approach, after insertion of a balloon catheter into the cervical ICA, was attempted and the aneurysm projecting antero-medially under the left carotid artery was exposed. The aneurysm had a distinct neck and its wall was not fragile. There was no macroscopic evidence of dissection of the ICA and the aneurysm was successfully clipped by conventional manipulation. Because of the difficulty in determining by angiographic evidence alone, whether an anterior wall aneurysm is a blister type or saccular type, careful follow-up is needed and if the shape or size changes, immediate appropriate treatment becomes mandatory. Intraoperative observation will determine the final diagnosis, as in this uncommon case.