Endoscopic endonasal inferior transclival approach, step-by-step dissection. The nasopharyngeal mucosa has been removed to expose the underlying muscle layer. The longus capitis muscle arises from the anterior tubercles of the transverse processes of the C3-C6 and firmly inserts into the superior clival line. The rectus capitis anterior is located immediately behind the longus capitis and has an oblique trajectory; it arises from the lateral mass and transverse process of C1 and inserts both at the superior and inferior clival lines. (Image courtesy of JC Fernandez-Miranda)