Walsh & Hoyt: Anterior Cerebral Artery, Anterior Communicating Artery, and Their Branches

The ACA originates as the medial and smaller of the two terminal branches of the ICA. It courses anteromedially to the hemispheric fissure, passing over the optic chiasm or the distal portion of the optic nerves and below the medial olfactory stria. In the interhemispheric fissure, it is joined to the opposite ACA by the anterior communicating artery (AComA). The segment of the ACA between the ICA and AComA is called the A-1 or precommunicating segment. The segment of the ACA distal to the AComA is usually separated into four smaller segments designated A-2 to A-5.