Microsurgical Relations between Internal Carotid Artery-Posterior Communicating Artery (ICA-PComA) Segment Aneurysms and Skull Base: An Anatomoclinical Study.

Purpose The study of the clinical, anatomic, imaging, and microsurgical characteristics of the aneurysms of the internal carotid-posterior communicating artery (ICA-PComA) segment and their relationships with the skull base structures. Methods The anatomic relationships of PComA with neurovascular elements and skull base structures were studied in cadavers. The clinical, imaging, and microsurgical findings of 84 microsurgically treated ICA-PComA aneurysms compiled in a prospective database were reviewed. Results The most important anatomic relations of the PComA and ICA-PComA aneurysms are with the oculomotor nerve around the oculomotor triangle that forms the roof of the cavernous sinus. Aneurysms of the ICA-PComA are classified according to the orientation of the aneurysmal sac in infratentorial, supratentorial, and tentorial. Infratentorial aneurysms frequently present with subarachnoid hemorrhage (SAH) and oculomotor nerve paralysis. They have relations with skull base structures that often make it necessary to totally or partially resect the anterior clinoid process (6.7%) or anterior petroclinoid dural fold (15%). Supratentorial aneurysms course with SAH and without oculomotor nerve involvement, but they often are associated with intracranial hematoma. Conclusion ICA-PComA aneurysms have complex anatomic relations. The orientation of the aneurysmal fundus induces relevant differences in the anatomic relations, clinical presentation, and microsurgical approach to ICA-PComA aneurysms.