De novo aneurysm on the posterior cerebral artery: a case report and literature review.

De novo aneurysm formation is a rare entity of cerebral aneurysms. The authors describe a 19-year-old man presenting with spontaneous intracerebral hemorrhage of unknown etiology. The initial cerebral angiography revealed no identifiable vascular lesion. A few weeks following a surgical evacuation of the hematoma, a tiny saccular aneurysm was incidentally found on the distal posterior cerebral artery (PCA) remote from the site of the primary ictus. Several rationales indicated that it was compatible with a cerebral aneurysm of infective etiology. The aneurysm was successfully treated by antibiotic therapy alone. To the authors' knowledge, de novo aneurysm on the PCA has rarely been reported.