I, The insert shows the site of the additional skin incision needed to add a retrosigmoid craniotomy and far-lateral approach. The scalp flap has been reflected to expose the suboccipital triangle located between the superior and inferior oblique and the rectus capitis posterior major and in the depths of which the vertebral artery courses with a dense venous plexus. J, The venous plexus has been removed to expose the margins of the suboccipital triangle. K, The rectus capitis posterior major and the inferior oblique have been reflected medially and the superior oblique laterally to expose the vertebral artery and surrounding venous plexus behind the atlanto-occipital joint. L, The venous plexus has been removed to expose the vertebral artery coursing with the C1 nerve behind the atlanto-occipital joint and across the upper edge of the posterior atlantal arch. (Images courtesy of AL Rhoton, Jr.)