Aneurysm of the posterior inferior cerebellar arteries/communicating artery.

Only 3 cases of aneurysm associated with the communicating artery between both distal posterior inferior cerebellar arteries (PICAs) have been reported in the literature. We present the 4th case of such an aneurysm arising from the communicating artery itself, which is unrelated to the arterial branches. A hypertensive 68-year-old man presented with a Hunt and Hess grade 4 subarachnoid hemorrhage. Angiographic studies revealed that the ruptured aneurysm arose from the fine communicating artery itself interconnecting both distal PICA vermian branches. The right PICA was absent and its vermian territory was supplied by the left PICA through this communicating artery. At surgery, a saccular aneurysm was noted which developed at the top of the arterial loop under the nodulus of the cerebellar vermis and was trapped. The actual prevalence and clinical significance of aneurism associated with the communicating artery interconnecting both PICAs are unknown, but defective embryonal development may lead to congenital vulnerability of the vascular wall, resulting in aneurysm formation.