Unusual intercarotid anastomosis associated with anterior communicating artery aneurysm. Case report.

The case is presented of a 34-year-old man with subarachnoid hemorrhage from rupture of an anterior communicating artery aneurysm. The magnetic resonance imaging and angiographic findings are reported. Angiography showed the aneurysm plus an unusual anastomosis between the intracavernous portions of both internal carotid arteries. The anastomosis crossed posterior to the base of the dorsum sellae and was associated with absence of the right internal carotid artery and the A1 segment of the right anterior cerebral artery. This is the 11th case of such an unusual intercarotid anastomosis reported in the literature.