Middle cerebral artery dissecting aneurysm with persistent patent pseudolumen. Case report.

The extremely rare condition of an ischemic right middle cerebral artery dissecting aneurysm with persistent patent pseudolumen is described. In the majority of cases of dissecting aneurysms, the pseudolumen persists for a very short time, probably because reentry from the pseudolumen is minimal or nonexistent. In contrast, the present case was assumed to have sufficient reentry from the bypass flow in the pseudolumen. Endothelial formation both in the true lumen and the pseudolumen was suggested as the possible mechanism of the stabilized double lumen.