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AJNR - American Journal of Neuroradiology

Published ahead of print on May 27, 2009
doi: 10.3174/ajnr.A1624

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American Journal of Neuroradiology 30:1688-1690, October 2009
© 2009 American Society of Neuroradiology

Case Report
INTERVENTIONAL

Pedunculated Basilar Terminus Aneurysm with Pseudo-Septation due to Anterior Herniation through a Perforated Membrane of Liliequist

L. Hacein-Bey^a,b,c and P.N. Varelas^b,c,d

^aFrom the Departments of Radiology (L.H.-B.)
^bNeurosurgery (L.H.-B., P.N.V.)
^cNeurology (L.H.-B., P.N.V.), Medical College of Wisconsin, Milwaukee, Wis
^dDepartments of Neurology and Neurosurgery (P.N.V.), Henry Ford Hospital, Detroit, Mich.

Please address correspondence to Lotfi Hacein-Bey, Radiological Associates of Sacramento Medical Group, 1500 Expo Pkwy, Sacramento, CA, 95815; e-mail: lhaceinbey{at}yahoo.com

SUMMARY: 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.