Mid A1 blister aneurysm presenting with subarachnoid hemorrhage: Case report and review.

Blister aneurysms are uncommon and difficult-to-treat lesions. They are a substantial cause of morbidity and mortality when encountered. Here, we report a blister aneurysm of the mid A1 segment of the anterior cerebral artery presenting with diffuse basal subarachnoid hemorrhage (SAH). The aneurysm was treated by surgical clipping of the parent vessel. Postoperatively, there was no filling of the parent vessel or aneurysm. A treatment algorithm including direct surgical repair and flow diversion for ruptured blister aneurysms is described. A high level of suspicion should be maintained in the setting of angiographic-negative SAH with an asymmetrically diffuse pattern.