A, Cerebrum with the coronal and sagittal sutures preserved, superior view. There is commonly an area devoid of bridging veins entering the superior sagittal sinus just in front of the coronal suture, as shown, that would be a suitable site for a transcallosal approach. The author places the flap for a transcallosal approach exposure one-third behind and two-thirds in front of the coronal suture. B, Lateral view, right hemisphere. The area in front of the coronal sutures is devoid of bridging veins emptying into the superior sagittal sinus. C, Anterior view. On the left side, a large bridging vein (yellow arrow), into which the anterior, middle, and posterior frontal veins empty, drains almost all of the left frontal lobe. On the right side, two large bridging veins (red and white arrows) drain most of the frontal lobe. D, Anterolateral view of the left hemisphere. A large part of the left frontal lobe is drained by a single large bridging vein (yellow arrow). In the limited exposures used for surgical approaches, it is difficult to know how significant the anastomotic channels are. Sacrificing the large bridging vein on the left frontal lobe is more likely to produce a disturbance of venous drainage than sacrificing the smaller frontal bridging veins on the right side. (Images courtesy of AL Rhoton, Jr.)