Ruptured dissecting aneurysm of the vertebral artery revealed by repeat angiography.

A case of subarachnoid hemorrhage caused by the rupture of a dissecting aneurysm of the vertebral artery is reported. The initial angiogram was normal, and repeat angiography carried out 12 days later revealed a dissecting aneurysm of the right vertebral artery. This angiographic change seems to be due to the progression of minimal dissection that was not found at the time of first angiogram.