Completely thrombosed giant aneurysm of the basilar artery trunk: a case report.

A patient with a completely thrombosed giant aneurysm arising from the trunk of the basilar artery is described. Although it is difficult to differentiate this anomaly from a posterior fossa tumor, negative angiographic findings combined with certain computed tomographic (CT) signs may point to the correct diagnosis. Our case demonstrates that one of these CT signs (viz. ringlike contrast enhancement) can be explained by the presence of vasa vasorum in the aneurysm wall.