Characteristics of Blood Blister-Like Aneurysms with a Saccular-Shape Appearance

Blood blister-like aneurysms (BBAs) are a subgroup of aneurysms located on nonbranching sites of the internal carotid artery (ICA) and characterized by small size, a fragile wall, and a poorly defined broad-based neck. Both direct surgery and endovascular treatment for BBAs are often challenging. Some of the BBAs have been reported to look like true saccular aneurysms, and the misdiagnosis of BBA might result in catastrophic outcomes. The purpose of this study is to clarify the clinical and intraoperative findings of saccular BBAs.

We analyzed clinical and intraoperative findings in consecutive 11 patients with subarachnoid hemorrhage caused by ruptured BBA. BBAs were divided into typical BBAs, which were defined as typical tiny, broad-based, blister-like aneurysms, and saccular BBAs, which seemingly looked like true saccular aneurysms but were demonstrated to be BBAs by the intraoperative findings of the laceration of the ICA. The characteristics of saccular BBAs were analyzed.

There were 4 patients with saccular BBAs in which the admission day was diverse from the onset day to several days after the onset. The origin of saccular BBAs was the medial (n = 2) or anterior (n = 2) walls of the ICA. Three of the 4 saccular BBAs pointed toward the optic nerve, whereas none of the typical BBAs pointed toward the optic nerve.

Saccular BBAs may not merely develop secondarily from typical BBAs, but also form by the surrounding structures-dependent mechanisms when an aneurysm points toward the optic nerve. The findings in this study suggest that saccular-shaped aneurysms at nonbranching sites of the ICA toward the optic nerve should be considered as saccular BBAs.