Median pericallosal artery with double proximal origin: case report and clinical consideration.

A 76-year-old male patient underwent magnetic resonance angiography of the head and neck vessels due to a recent incident of transitory ischemic attack. Cerebral angiogram uncovered the double proximal origin of the median unpaired pericallosal artery from the duplicated anterior communicating complex. The vessel curved around the corpus callosum and irrigated the paracentral lobule and the medial parietal cortical areas. The main trunks of the anterior cerebral arteries showed a branching pattern of the marginal callosal arteries, supplying orbital and frontal territories. The pre-communicating segment of the left anterior cerebral artery was identified as hypoplastic. The co-existence of the duplicated anterior communicating artery, with the medial pericallosal artery ascending from it, represents a potential danger for both open and endovascular surgery on the anterior circle of Willis as the deep half of this complex is obscured from the surgeon's eyes. Thorough interpretation of preoperative radiographic images and understanding of the developmental mechanisms of such variability are vital. The described branching arrangement of the anterior communicative region and possible mechanisms of migration with following fusion of the pericallosal arteries are discussed in this paper.