Interdural transcavernous approach to the upper clivus; close-up view. The origin of the IHA can now be better visualized. Coagulation and transection of the IHA is usually required to avoid its avulsion from the ICA.  The top of the posterior clinoid can be clearly defined, which facilitates controlled dissection of the ligamentous attachments. The interclinoid ligament is observed attaching to the posterior clinoid and forming the roof of the cavernous sinus. Note the postero-lateral projection of the top of the posterior clinoid, which increases the difficulty of the posterior clinoidectomy maneuver. (Image courtesy of JC Fernandez-Miranda)