The two anterior cerebral arteries anastomose proximally via the anterior communicating artery, anterior to the optic chiasm (eFig. 9.22). Distal to this connection, the anterior cerebral artery (ACA) courses along the medial aspect of the cerebral hemisphere within the longitudinal fissure and follows the superior border of the corpus callosum to the anterior portion of the parietal lobe. Along its course two large branches arise: the callosomarginal artery, which follows the cingulate sulcus, and the pericallosal artery, which is immediately adjacent to the corpus callosum (eFig. 9.23). Given its course and branches, the ACA perfuses most of the medial aspect of the brain from the frontal lobe to the anterior portion of the parietal lobe.