Endonasal perspective of the exposed parasellar and paraclival regions. The upper or “sellar” clivus is located behind the pituitary gland and is limited inferiorly by the floor of the sella; it relates laterally with the parasellar (paraclinoidal and cavernous) ICA segments. The middle or “sphenoidal” clivus is limited inferiorly by the floor of the sphenoid sinus or choanas and laterally by the paraclival ICA segment. The vidian nerve runs from the pterygopalatine fossa to the infero-lateral aspect of the foramen lacerum. The foramen lacerum is located at the lateral aspect of the floor of the sphenoid sinus and marks the transition from middle to lower or “nasopharyngeal” clivus. (Image courtesy of JC Fernandez-Miranda)