Unexpected early radiographic findings associated with a ruptured blister-like carotid wall aneurysm

A 33-year-old man presented with aneurysmal subarachnoid hemorrhage from a ruptured, blister-type sidewall internal carotid artery (ICA) aneurysm. Balloon-assisted coiling was performed with residual neck. He subsequently developed severe vasospasm requiring intra-arterial therapies on multiple occasions, during which it was noted that despite widespread vasospasm, a focal segment of the ICA at the site of the aneurysm showed no significant spasm, suggesting underlying vessel abnormality. He was discharged without deficit and scheduled for flow diversion given concern over this potentially pathologic segment of vessel. At time of scheduled flow diversion 6 weeks later, a de novo unstable-appearing 6 mm stalk-like pseudoaneurysm was identified in this segment. Both aneurysms and the diseased vessel were successfully treated with Pipeline stenting, with excellent clinical and angiographic result. This case highlights the need for close angiographic follow-up when there is a heterogeneous vasospastic response in arterial segments adjacent to a ruptured aneurysm.