Stepwise Dissection of Right Cerebral Hemisphere. G, The temporal operculum has been retracted to expose the inferior part of the insula. The pars triangularis is small and its tip is retracted upward away from the fissure, resulting in the formation of a wide space or a wide common stem (red dotted arrow) between the partes opercularis and orbitalis, from which the anterior horizontal and ascending rami arise. H, The frontoparietal and temporal opercula have been retracted to expose the insula. The inferior limiting sulcus is positioned below the long gyri of the insula and separates the insula from the sylvian surface of the temporal lobe. The central sulcus, the deepest insular sulcus, separates the insula into larger anterior and smaller posterior portions. I, Lateral view of the same hemisphere. The anterior and middle short gyri are separated by the short insular sulcus, and the middle and posterior short gyri are separated by the precentral insular sulcus. The long gyri arise as a single gyrus near the limen insulae and bifurcate posteriorly into anterior and posterior long gyri, which are separated by the long insular sulcus. The transverse gyrus connects the anterior part of the insula to the gyri on the orbital surface. The insular pole, located at the anteroinferior edge of the insula between the anterior limiting sulcus and the central insular sulcus, is approximately 2 cm wide (green area). The insular pole is located below the insular apex, the most laterally prominent point of the insula. J, The frontoparietal operculum was removed using an axial cut at the level of the superior limiting sulcus, and the temporal operculum was removed using a sagittal cut parallel to the lateral surface of the temporal lobe. The most anterior of the transverse temporal gyri, the Heschl gyrus, extends backward from the cortical surface to the junction of the superior and inferior limiting sulci. K, The sagittal cut has been extended to the medial edge of the inferior limiting sulcus to show the relationship between the temporal horn and the insula. The Heschl gyrus is located above the roof of the temporal horn and the body of the hippocampus. The vertical distance from the inferior limiting sulcus to the posterior edge of the head of the hippocampus is approximately 1 cm. L, Lateral view of another right insula. The frontoparietal and temporal opercula have been removed to expose the insula. The central insular sulcus, the deepest of the insular sulci, arises from the limen area and extends posterosuperiorly to reach the superior limiting sulcus. The anterior part of the insula consists of three gyri—the anterior, middle, and posterior short gyri. These are separated by the short insular and precentral insular sulci and fuse with each other at the insular pole. The long gyri arise as a single gyrus below the insular apex, near the limen insulae, and bifurcate posteriorly into two gyri. Incising along the inferior limiting sulcus has exposed the temporal horn of the lateral ventricle. The choroid plexus has been elevated to expose the head and body of the hippocampus. The inferior choroidal point, the lower end of the choroidal fissure, is located just behind the head of the hippocampus at a distance of approximately 1 cm from the inferior limiting sulcus. The anterior choroidal artery enters the ventricle at the inferior choroidal point. (Images courtesy of AL Rhoton, Jr.)