Suboccipital triangle, far lateral craniotomy and transcondylar craniotomy anatomy. Cervical musculature of the suboccipital triangle has been removed bilaterally revealing the major surgical approaches to the dorsal and dorsolateral medulla. The V3 segment of the vertebral artery courses along the sulcus arteriosus of the atlas (C1) alongside the C1 nerve roots. Intradural (V4) segments of the vertebral arteries course ventral to the spinal accessory nerve fibers. Telovelotonsillar and cortical segments of the posterior inferior cerebellar arteries are visible dorsal to the cerebellar tonsils. The anterolateral foramen magnum is comprised of the occipital condyles, which are visible bilaterally (on the left, covered by dura). Drilling of the posterior occipital condyles (a transcondylar craniotomy) provides even more lateral exposure, allowing visualization of the ventral medulla. (Image courtesy of AL Rhoton, Jr.)