De novo dissecting aneurysm in a patient with a ruptured saccular lesion. Case report.

Formation of a new saccular aneurysm after successful treatment of ruptured aneurysm has recently raised significant clinical concerns; however, de novo formation and rupture of a dissecting aneurysm has not been discussed. The authors report on a 42-year-old man who initially sought treatment for a ruptured saccular aneurysm of the right middle cerebral artery, which was successfully eliminated by surgical clipping of the aneurysm neck. Two years later, the patient presented with another subarachnoid hemorrhage and was found to have a dissecting aneurysm of the right vertebral artery, which arose from a previously angiographically documented normal artery. This rare association sheds light on the causes and growth of two distinct types of aneurysms, both clinically and pathologically.