To repair a cerebral aneurysm by craniotomy, an incision is made in the skin on the side of the head (A). Small holes are drilled in the skull (B), and a special saw is used to cut the bone between the holes (C). The bone is removed (D), and the aneurysm is treated (E). The bone is replaced, and the skin is sutured closed (F). (Illustration by GGS Inc.)