Introduction: The nasal cavity is the main path for endoscopic skull base approaches. This study presents the 3D osteology of nasal cavity.

Methods: Disassembled bones were paired to reconstruct each wall. Tridimensional photography was performed and stereoscopic pairs combined into anaglyphic images.

Results: The nasal cavity has a bony entrance: piriform aperture; an outlet to pharynx: choana; a medial wall: nasal septum, a lateral wall, separating nasal cavity from orbit, maxillary sinus and pterygopalatine fossa; a posterior wall, continuous with sphenoid sinus; roof and floor. The frontal bone forms most of the roof, which extends from the nasal part of the frontal bone to sphenoid body. The sphenoid is an important crossroad along this pathway: working through its different parts enables to reach different skull base compartments. The body and pterygoid processes of sphenoid are paramount to understand nasal cavity. The body contains the sphenoid sinus. The anterior wall of the sinus is also posterior wall of nasal cavity. The pterygoid processes form the outlines of pharynx, pterygopalatine and infratemporal fossae. The perpendicular plate of palatine and the sphenoidal medial pterygoid plate form the lateral frame of choana, while vomer forms its medial frame. The combination of vomer and perpendicular plate of ethmoid forms the core of bony septum. The medial surface of maxillae is important to deal surgically with the lateral wall of the nasal cavity. Just anterior to the maxillary hiatus, the medial surface presents the lacrimal groove, which receives the lacrimal bone to form the nasolacrimal duct. The anterior edge of perpendicular plate of palatine, ethmoidal and maxillary processes of the inferior nasal concha overlap onto the maxillary hiatus. The ethmoid completes the lateral wall of the nasal cavity.

Conclusions: Understand the bony formation of the nasal cavity walls is paramount in choosing and performing endoscopic skull base approaches.

Patient Care: Allowing for safe performance of complex surgical approaches.

Learning Objectives: 1. Review the bony formation of each nasal cavity wall. 2. Enhance understanding of the nasal cavity as the main endoscopic surgical corridor.

References: 1. Martins C et al. Anatomy of Nasal Cavity and Paranasal Sinuses. In: Stamm AC. Thansnasal Endoscopic Skull Base and Brain Surgery. Thieme, 2011. 2. Rhoton Jr. AL. Cranial Anatomy and Surgical Approaches. Lippincott Williams & Wilkins, 2003.