Posterior Air Cells Of The Ethmoid Bone

Description

Posterior ethmoidal air cells occupy the posterosuperior ethmoid labyrinth, positioned lateral to the cribriform plate and posterior to the bulla ethmoidalis and middle ethmoidal cells. Their thin bony septations form a honeycomb of air-filled cavities between the medial orbital wall (lamina papyracea) laterally and the superior nasal meatus and middle turbinate medially, with the skull base (fovea ethmoidalis) forming a fragile superior boundary. Posteriorly, the most terminal cells approach the anterior wall of the sphenoid sinus, and in some skulls a posterior cell may pneumatize superiorly around the optic canal as an Onodi cell. Boundaries matter. These spaces anchor surgical navigation during functional endoscopic sinus surgery, where identifying the transition from anterior to posterior ethmoid helps prevent two classic complications: cerebrospinal fluid leak at the cribriform plate or fovea ethmoidalis, and orbital injury through the lamina papyracea with extraocular muscle entrapment or hematoma. The posterior ethmoidal artery (a branch of the ophthalmic artery) courses from orbit to ethmoid near the skull base, and its relationship to the posterior ethmoid roof explains why uncontrolled bleeding and skull base violation can occur in the same corridor. Emphasis on the posterior ethmoid also supports teaching about patterns of chronic rhinosinusitis, where obstruction at the superior meatus and sphenoethmoidal recess can maintain disease in posterior ethmoid and sphenoid compartments. Use this illustration in head and neck anatomy modules covering the paranasal sinuses, in otolaryngology and ophthalmology teaching on endoscopic landmarks near the orbit and anterior cranial fossa, or in surgical atlases that discuss ethmoidectomy, sphenoidotomy, and Onodi cell risk. Anatomical accuracy verified by SciePro's Medical Advisory Board.