[A Case of Unruptured Cerebral Aneurysm Arising from Duplicate Origin of the Middle Cerebral Artery].

We experienced a case of an unruptured cerebral aneurysm arising from a duplicate origin of the middle cerebral artery(MCA). Initially, we diagnosed the condition as an unruptured aneurysm arising from the internal carotid artery on three-dimensional computed tomography;neck clipping was attempted. However, an unidentified vessel was found around the aneurysmal neck, which could not be easily separated from the aneurysm, making neck clipping difficult. Thus, we only completed coating of the aneurysm without neck clipping. Postoperatively, cerebral angiography showed that the unidentified vessel originated from the internal carotid artery and fused with the MCA horizontal segment. We recognized that the identified vessel was a duplicate origin of the MCA. Few reports on the treatment of an aneurysm arising from a duplicate origin of the MCA are available;there has been no discussion on whether this vessel can be occluded. We assumed that occlusion of the proximal end of the duplicate origin of the MCA together with the aneurysm was unlikely to cause ischemia as the duplicate origin of the MCA fuse with MCA. Coil embolization was performed for the aneurysm, and the duplicate origin was unexpectedly preserved immediately after coil embolization. However, it was not enhanced on cerebral angiography performed after several months, and no cerebral infarction was noted on magnetic resonance imaging. If preservation of the duplicate origin of the MCA is difficult, occlusion of the aneurysm together with the proximal end of the duplicate origin of the MCA can be considered as a surgical strategy.