Expanded endonasal approach: fully endoscopic, completely transnasal approach to the middle third of the clivus, petrous bone, middle cranial fossa, and infratemporal fossa

TLDR

The middle third of the clivus and the surrounding petrous internal carotid artery region is a deep, neurovascularly critical skull‑base area that is difficult to access and often affected by typical skull‑base diseases, making expanded endoscopic endonasal approaches a promising option. This study aims to demonstrate the clinical feasibility of reaching the paraclival space in the middle clivus, to propose a practical modular classification, and to detail the critical surgical anatomy for each module. The authors mapped the anatomy around the petrous ICA, cavernous sinus, and middle clivus into zones, translated cadaveric findings into a clinically applicable categorization, and illustrated each zone with a representative case. The expanded endonasal approach proved feasible for accessing the middle clivus, petrous ICA, cavernous sinus, and medial infratemporal fossa when lesions are centrally located and neurovascular structures displaced laterally.

Abstract

Object The middle third of the clivus and the region around the petrous internal carotid artery (ICA) is a difficult area of the skull base in terms of access. This is a deep area rich with critical neurovascular structures, which is often host to typical skull base diseases. Expanded endoscopic endonasal approaches offer a potential option for accessing this difficult region. The objective of this paper was to establish the clinical feasibility of gaining access to the paraclival space in the region of the middle third of the clivus, to provide a practical modular and clinically applicable classification, and to describe the relevant critical surgical anatomy for each module. Methods The anatomical organization of the region around the petrous ICA, cavernous sinus, and middle clivus is presented, with approaches divided into zones. In an accompanying paper in this issue by Cavallo, et al., the anatomy of the pterygopalatine fossa is presented; this was observed through cadaveric dissection for which an expanded endonasal approach was used. In the current paper the authors translate the aforementioned anatomical study to provide a clinically applicable categorization of the endonasal approach to the region around the petrous ICA. A series of zones inferior and superior to the petrous ICA are described, with an illustrative case presented for each region. Conclusions The expanded endonasal approach is a feasible approach to the middle third of the clivus, petrous ICA, cavernous sinus, and medial infratemporal fossa in cases in which the lesion is located centrally, with neurovascular structures displaced laterally.