We present a case in which bilateral aneurysm developed from junctional dilatations of the posterior communicating arteries. A follow-up study of this case strongly suggests that a junctional dilatation can develop into a true aneurysm. After reviewing nine cases in the literature, the authors conclude that junctional dilatations, especially in young women with a history of aneurysmal rupture, should be carefully followed by angiography.
