Endoscopic endonasal middle and inferior transclival approach, intradural stage. The inferior transclivalapproach provides access to the premedullary cistern and its contents: vertebral arteries, vertebrobasilarjunction, anterior spinal artery, and hypoglossal nerve rootlets. These rootlets arise from the medullain the pre-olivary sulcus, and run postero-lateral to the vertebral artery to enter the hypoglossal canal,where the rootlets merge to form the hypoglossal nerve. The jugular tubercle is located above the hypoglossal canal. The occipital condyle is located below the hypoglossal canal; a medial condylectomy hasbeen performed, providing direct access to the dural entry point of the vertebral artery. (Image courtesy of JC Fernandez-Miranda)