Development and Rupture of Very Small (≤3 mm) de novo Internal Carotid-Posterior Communicating Artery Mirror Aneurysms: Two Case Reports

Abstract

We report two cases of very small (≤3 mm) de novo internal carotid-posterior communicating aneurysms (IC-PC AN) that developed and ruptured within a short period at the mirror site of a previous aneurysm.
Case 1: A 75-year-old woman presented with subarachnoid hemorrhage (SAH) caused by rupture of a very small (2.5 mm) left de novo IC-PC AN at the mirror site of a right IC-PC AN clipped 4 years and 6 months ago. The de novo IC-PC AN evolved from dilatation of the infundibulum of the posterior communicating artery and ruptured within 10 months after her last MR angiography (MRA).
Case 2: A 75-year-old woman presented with SAH following rupture of a very small (2.5 mm) right de novo IC-PC AN at the mirror site of a left IC-PC AN embolized 14 years ago. The de novo IC-PC AN developed and ruptured within 7 months after her last MRA.
We emphasize the importance of routine and-long-term radiographic screening in patients with cerebral aneurysms to detect de novo aneurysms, especially at mirror sites of previously occurring aneurysms. Aggressive surgical intervention may be indicated for even very small-sized de novo aneurysms due to the high risk of SAH.