FIG 1. Case 1, a 55-year-old woman with acute subarachnoid hemorrhage.

A, Anteroposterior right vertebral angiogram, showing the eccentric location of the aneurysm relative to the vertebral artery.

B, Lateral right vertebral angiogram, showing aneurysm of the V4 segment of the vertebral artery. Tapered narrowing proximal and distal suggests dissection, which is confirmed by visualization of a linear filling defect representing intima.

C, Sixteen hours later, left vertebral anteroposterior angiogram, showing tapered narrowing of the vertebral from propagation of the dissection, with severe narrowing at the vertebrobasilar junction.

D, Left vertebral angiogram after angioplasty, showing markedly improved caliber from vertebral to basilar artery.

E, Anteroposterior right vertebral angiogram, showing pseudoaneurysm between the right posterior inferior cerebellar artery and the vertebrobasilar junction.

F, Lateral right vertebral angiogram after embolization, showing right vertebral occlusion distal to the PICA.