A, The right AChA arises from the posterior wall of the ICA above the origin of the PComA and passes back-ward below the optic tract and lateral to the PCA. It ascends around the medial surface of the uncus as it travels posteriorly. B, The medial part of the parahippocampal gyrus has been removed. The AChA courses backward medial to the anterior segment of the uncus to reach the uncal apex located at the junction of the anterior and posterior uncal segments where it turns laterally along the upper margin of the posterior uncal segment to reach the choroidal fissure. C, The posterior uncal segment has been retracted. The AChA passes above the posterior uncal segment and enters the temporal horn by passing through the choroidal fissure located between the thalamus above and fimbria of the fornix below. The lateral geniculate body forms the part of the thalamus above where the artery enters the choroidal fissure. The dentate gyrus is located at the lower edge of the fimbria. D, The floor of the temporal horn and the fimbria have been removed to expose the AChA entering the choroid plexus of the temporal horn by passing through the choroidal fissure just behind the posterior segment of the uncus. The lower end of the choroidal fissure and the site where the artery passes through the fissure are called the inferior choroidal point. (Images courtesy of AL Rhoton, Jr.)