Left Hemisphere Cerebrovascular Structures with Angiographic Correlate. A, Lateral view of the left hemisphere. The pars orbitalis has been retracted anterior and superiorly. 1, precentral gyrus; 2, postcentral gyrus; 3, pars triangularis, anterior horizontal, and anterior ascending rami of the sylvian fissure; 4, orbitalis; 5, pars opercularis; 6, posterior orbital gyrus and the anterior insular cleft; 7, lesser wing of the sphenoid. Asterisk, insular apex. M2, insular segment of the MCA that has just turned around the insular pole (just distal to the genu of the MCA). B, Same specimen in A in surgical position (left pterional exposure). The spatula on the left side is retracting the planum temporale, and the spatula on the right side is retracting the posterior portion of the pars orbitalis. 1, lesser wing of sphenoid; 2, superior temporal gyrus; 3, pars orbitalis; 4, middle temporal gyrus; 5, posterior orbital gyrus; 6, anterior insular cleft and anterior short gyrus of the insula; 7, posterior long gyrus and the inferior limiting sulcus of the insula; 8, pars triangularis; 9, precentral gyrus; 10, pars opercularis; 11, Heschl’s gyrus; 12, postcentral gyrus; M2, insular segment of the MCA that has just turned around the insular pole (just distal to the genu of the MCA). Asterisk, insular apex. The arrowheads indicate the sharp transition between the basal and lateral surfaces of the cerebrum. C, AP view of a right carotid angiography. Note the laterally deviated supraclinoid carotid artery, the initial upward course followed by a downward curve of the M1, and then a rather horizontal course to turn around the insular pole. D, The expected intraoperative course of the M1 shown in C. (Images courtesy of AL Rhoton, Jr.)