The Insula. A, Right pterional exposure. The inset shows the position of the head and skin incision for the frontotemporal craniotomy. The sylvian fissure has been widely opened and the frontal and temporal opercula have been retracted to expose the anterior half of the insula. The inferior trunk has been retracted to expose the junction of the central and precentral insular veins forming a common stem. The central insular vein courses along the central insular sulcus and drains the sulcus and the adjacent portion of the anterior short gyrus. The precentral insular vein drains the middle and posterior short gyri. The posterior insular vein courses along the inferior limiting sulcus and joins the deep MCV in the limen area. B, Another right pterional exposure. The M2 branches have been retracted to expose the formation of the deep MCV. The precentral insular vein drains the middle short gyrus and insular apex and joins the central insular vein behind the apex. The central insular vein courses along the central insular sulcus and joins the precentral insular vein to form a common trunk, which receives the anterior and posterior insular veins forming the deep MCV at the limen insulae. C, Lateral view of right cerebral hemisphere. The frontoparietal and temporal opercula have been retracted to expose the course of the insular veins. The four insular veins and the initial portion of the deep MCV have been exposed. The anterior insular vein courses downward and backward near the anterior limiting sulcus, drains the anterior limiting sulcus and anterior short gyrus, and empties into the deep MCV. The precentral insular vein, the insular vein most commonly connected with the SSV, drains the middle short gyrus and the insular apex, crosses the anterior short gyrus, and turns superficially to empty into the SSV without contributing to the formation of the deep MCV. The central insular vein courses anteroinferiorly; drains the central insular sulcus, the posterior short and anterior long gyri, and the limen area; and joins the posterior insular vein. The posterior insular vein courses anteriorly along the inferior limiting sulcus; drains the inferior limiting sulcus, the adjacent portion of the posterior long gyrus, and the limen area; and joins the central insular vein to form the initial portion of the deep MCV near the limen insulae. The bifurcation of the MCA has been retracted to expose the LSAs arising from the postbifurcation trunks. Although the most lateral LSA most frequently originates from the prebifurcation M1 segment, in this particular hemisphere the artery originates from the superior trunk. The mean distance from the insular apex, the most laterally prominent or highest point on the insula, to the origin of the most lateral LSA was less than 15 mm (yellow dashed arrow). (Images courtesy of AL Rhoton, Jr.)