[Angiographic findings of vertebral dissecting aneurysm. Report of two cases and review of literature].

The authors report two cases of vertebral dissecting aneurysm. The first case, a 49-year-old female, developed severe headache and computed tomography scan showed subarachnoid hemorrhage (SAH), but 4-vessel cerebral angiography failed to show an aneurysm. The second angiograms obtained 2 weeks later showed possible aneurysmal dilatation on the right vertebral artery. The third angiograms, 2.5 months after SAH, disclosed a right vertebral fusiform aneurysm on the arterial phase and it was diagnosed as a dissecting aneurysm since the contrast medium remained until the very late venous phase. The previous angiograms were reviewed using the subtraction technique, which revealed retention of the contrast medium. The second case, a 42-year-old female, suffered from SAH. Left vertebral angiography revealed a fusiform aneurysmal tapered narrowing just distal to the aneurysm, which was a typical "pearl and string sign." The subtraction film of the venous phase also showed retention of the contrast medium in the aneurysmal portion. These findings accurately diagnosed dissecting aneurysm of the vertebral artery. Since the classical true diagnostic "double lumen sign" was rarely observed in the angiograms, it was not easy to diagnose dissecting aneurysm of the vertebral artery. The authors emphasize the angiographic findings of retention of the contrast medium in the venous phase as a "true diagnostic sign" for correct diagnosis of dissecting aneurysm.