Intraoperative Sylvian Dissection. A, Intraoperative photograph displaying cerebral exposure after a standard right pterional craniotomy. The tip of the suction tube has retracted the pars triangularis medially. 1, posterior orbital gyrus; 2, lateral orbital gyrus (pars orbitalis). The blue arrowheads indicate frontotemporal arachnoid reflection on the basal surface. The black arrowheads indicate frontotemporal arachnoid reflection on the lateral surface. B, Continuation of A. The frontotemporal arachnoid membrane has been split to display the anterior opercular compartment of the sylvian fissure on the basal surface. 1, lesser wing of the sphenoid; 2, planum polare; 3, insular apex. The posterior orbital gyrus is retracted medially by the tip of the suction tube. The black arrowheads indicate the frontotemporal arachnoid membrane. The blue arrow indicates the beginning of the anterior insular cleft. (Images courtesy of AL Rhoton, Jr.)