A, A1 segments of equal size and small communicating artery pass above the optic chiasm. Recurrent arteries arise from the lateral side of A2. Recurrent arteries pass anterosuperior to A1. B, Both A2 segments arise from large left A1. The right A1 is small. A1 segments pass above the optic nerves. Recurrent arteries arise from A2 segments. Right recurrent artery is longer than the A1 segment. The left recurrent artery passes superior to the A1. Branches of the AComA supply the lamina terminalis above the optic chiasm. C, A1 segments are connected by a double communicating artery. The right recurrent artery arises from the A2 and courses above the A1. The left recurrent artery arises from and passes above the A1. Multiple arterioles pass to the optic chiasm and tract. D, A1 segments are connected by a double communicating artery. Two recurrent arteries arise on the right; one arises proximal and one distal to the communicating artery. The left recurrent artery arises from the posterior aspect of the A1. A spray of arterioles passes from the communicating artery to the optic chiasm. E, A multichanneled AComA gives rise to multiple arterioles to the optic nerves and chiasm and lamina terminalis. A double recurrent artery is on the right. The left recurrent artery gives rise to a large branch that passes below the gyrus rectus to the frontal tip. F, The left A1 segment is split into a double channel. Both A2 segments arise predominantly from the right A1. The left recurrent artery arises from one of the two A1 segments on the left. The right recurrent artery arises from the A2. G, Triple A2 segments arise from the communicating artery area. The left recurrent artery arises from the A1 segment; right from the junction of the A1 and A2 segments. H, Tortuous A1 segments loop forward to the area of the tuberculum sellae. The left recurrent artery arises from the A2 segment and the right recurrent artery arises from the A1 segment. (Images courtesy of AL Rhoton, Jr.)