Septations within cerebral arteries or aneurysms are exceedingly rare in the absence of associated fenestrations. We report an unusual unruptured pedunculated basilar apex aneurysm, with a "pseudoseptation" between the main aneurysmal sac and an anterior compartment, which was, in fact, represented by a perforation in the membrane of Liliequist, permitting anterior aneurysmal herniation into the carotid-chiasmatic cistern. The patient was successfully treated with detachable coils. This case is unusual on 2 accounts: 1) the aneurysm's appearance, and 2) the presence of a large fenestration in the membrane of Liliequist, of which anatomic features are herein reviewed.
Hacein-Bey, L., & Varelas, P. N. (2009). Pedunculated basilar terminus aneurysm with pseudo-septation due to anterior herniation through a perforated membrane of liliequist. American Journal of Neuroradiology, 30(9), 1688–1690. https://doi.org/10.3174/ajnr.A1624