Radiographic and histologic demonstration of an aneurysm developing on the infundibulum of the posterior communicating artery

✓ In this case an aneurysm of the posterior communicating artery developed 9 years after an infundibular dilatation of this posterior communicating artery, without aneurysm formation, had been radiographically demonstrated. Histological examination, after a fatal subarachnoid hemorrhage from the aneurysm, demonstrated that it arose exactly at the site of narrowing of the funnel-shaped infundibulum.