Aneurysm at a duplication of the middle cerebral artery.

In an anatomic study of 374 autopsied brains, Crompton and Lond (1) found that in 3% (10 of 374 cases) there was an artery arising from the internal carotid artery between its terminal bifurcation and the origin of the anterior choroidal artery, which passed into the Sylvian fissure along with the ordinary middle cerebral artery. He termed this vessel an accessory middle cerebral artery. In addition, another case with an artery arising from the region of the anterior communicating artery and passing back similarly into the Sylvian fissure was noted. Teal et al (2) established a distinction between these two arteries and called the one originating from the ICA a duplication of the middle cerebral artery. He called the other originating from the anterior cerebral artery an accessory middle cerebral artery. An aneurysm of the duplication of the middle cerebral artery was described by Crompton and Lond (1) and was classified as an internal carotid artery aneurysm, but it is rare. In this paper, two cases of ruptured aneurysm at the origin of the duplication of the middle cerebral artery will be reported and discussed together with eight previously documented cases.