We report a case of a large aneurysm of left posterior cerebral artery presenting with intraluminal thrombosis or intramural hemorrhage. A 49-year-old female was admitted to our department suffering from severe headache and vomiting. CT scan did not show subarachnoid hemorrhage but demonstrated a round high density mass of 1.5 cm in diameter in the left ambient cistern. MRI demonstrated that the intensity of the inside of the mass was low and that of the outer wall was somewhat high in the both Ti and T2 weighted image. Cerebral angiography showed crescent opacification of supero-lateral part of the aneurysm while medial-inferior part was not visualized, indicating thrombus formation.
We carried out surgery via the left extended subtemporal approach. No evidence of subarachnoid hemorrhage was observed during the operation. The wall was dark-blue colored. The parent artery was clipped at the proximal side of the aneurysm and disappearance of the aneurysm was confirmed by the intraoperative angiography. The postoperative course was uneventful and CT scan showed no abnormal low-density area. PCA aneurysms were overviewed literary, and mechanisms of intraluminal thrombosis and intramural hemorrhage were considered.