Endoscopic and microsurgical anatomy of the cranial base

Neuroendoscopic transnasal surgical approaches have become increasingly common for some time and have started to replace microsurgical techniques in pituitary surgery. Endoscopic transnasal approaches have also been recently used in some neurosurgical centres to reach pre- and retrosellar areas and targets localized in the basal cisterns. One major factor is the localization of the carotid artery between the siphon and aperture externa of the carotid canal at the base of the petrous bone. The following areas are especially critical: 1. the anterior siphon area 2.the area between the bottom of the sphenoid sinus and the base of Processus pte- goideus 3. the proximity of the carotid canal to the Tuba Eustachii the labyrinth Bulbus su- rior of the internal jugular vein and the facial nerve. Some segments of the course of the carotid artery are well known but they have rarely been surgical target areas using transnasal approaches to date. This has changed since the introduction of modern imaging techniques especially neuronavigation. It has become possible to identify and localize structures of the skull and extra- and intracranial structures in any desired plane.