Transcondylar craniotomy. The vertebral artery has been completely mobilized and reflected in this transcondylar craniotomy to visualize the ventral medulla. The dural ring around the vertebral artery, demarking the V3 and V4 segments, is visible along the lateral medulla and the contralateral vertebral artery is visible across midline. The sigmoid sinus is retracted laterally to expose the lateral medullary segment of the posterior inferior cerebellar artery along with the ascending spinal accessory nerve fibers and the hypoglossal nerve. (Image courtesy of AL Rhoton, Jr.)