Ruptured right posterior inferior cerebellar artery aneurysm associated with hypoplasia of the right vertebral artery and both internal carotid arteries.

The authors report an extremely rare case of a ruptured saccular aneurysm of the right posterior inferior cerebellar artery (PICA) associated with hypoplasia of bilateral internal carotid arteries (ICAs) and the right vertebral artery (VA). The aneurysm was successfully treated by clipping of the aneurysm itself using a lateral suboccipital approach. The aetiology of hypoplastic ICAs and right VA is uncertain, but the associated distal aneurysm from the right PICA appears to have developed most likely due to a coexistent congenital vessel wall anomaly of the cerebral arterial structure.