The upper clivus is the part above the crossing of the trigeminal and the abducens nerves from the posterior to the middle cranial fossa; this part includes the dorsum sellae and the posterior clinoid processes. This area is bounded anteriorly by the sella turcica and sphenoid sinus, posteriorly by the basilar artery and midbrain, and laterally by the cavernous sinus, temporal lobes, and (from superior to inferior) cranial nerves III through VI.