Microsurgical Clipping of Giant P3 Segment Posterior Cerebral Artery Aneurysm: 2-Dimensional Operative Video.

Posterior cerebral artery (PCA) aneurysms comprise <2% of all intracranial aneurysms and are usually located on the P1 and P2 segments. Aneurysms of the P3 segment of the PCA are even rarer, and despite their proximity to the cerebral aqueduct, presentation with hydrocephalus is exceptional. This video demonstrates the case of a 28-year-old female patient who presented acute hydrocephalus due to a partially thrombosed, giant P3 segment PCA aneurysm. The patient was operated on in the semisitting position, and a right frontal ventricular drain was placed for brain relaxation. A U-shaped skin incision was made, and a left-sided, 6 cm × 6 cm parietooccipital craniotomy crossing the midline was performed. An interhemispheric approach was used to reach the aneurysm. The aneurysm was trapped via temporary clipping of the inflow and outflow arteries, thrombectomized, and then clipped using a right-angled fenestrated aneurysm clip. Postoperative computed tomography and magnetic resonance imaging revealed resolution of the hydrocephalus, and cerebral angiography confirmed total exclusion of the aneurysm from the circulation and occlusion of the P4 segment of the PCA, which was considered embolic. The patient made an excellent recovery, and she was discharged on postoperative day 3 (Video 1). This case demonstrates the efficacy of microsurgical clipping for a giant thrombotic P3 segment PCA aneurysm that caused a mass effect. Surgery excluded the aneurysm from the circulation and decompressed the cerebral aqueduct, obviating the need for a permanent ventriculoperitoneal shunt.