Persistent patent pseudolumen of ruptured dissecting aneurysm involving the posterior inferior cerebellar artery after proximal clipping.

In the majority of cases of ruptured vertebral artery dissecting aneurysm after proximal clipping, the dissected pseudolumen persists for a very short time, probably because re-entry from the pseudolumen is minimal. Recent reports have indicated a high risk of rebleeding of dissecting aneurysms involving the posterior inferior cerebellar artery (PICA) after proximal clipping, probably due to excessive retrograde flow from the distal vertebral artery into both the PICA and the pseudolumen. We describe an extremely rare case of ruptured dissecting aneurysm involving the PICA with persistent patent pseudolumen after proximal clipping. The present case was assumed to have developed a moderate retrograde flow just sufficient to maintain the patent pseudolumen in the chronic stage. Neointimal formation is suggested to be a possible mechanism by which the pseudolumen is stabilized for a very long period.