ANATOMICAL VARIABILITY OF THE ETHMOID AND SPHENOID SINUSES.

Background: The ethmoid and sphenoid sinuses exhibit marked anatomical variability that can impact surgical approaches and predispose individuals to complications during sinus and skull base procedures.

Objective: To characterize the morphometric patterns and anatomical variants of the ethmoid and sphenoid sinuses based on high-resolution CT data and to analyze their surgical and clinical significance.

Methods: A total of 400 CT scans were analyzed. Sinuses were classified by pneumatization type, dimensions, and presence of anatomical variants. 3D reconstructions were performed to assess spatial orientation and proximity to neurovascular structures.

Results: Ethmoid sinus complexity was classified into three distinct types, with higher complexity correlating with narrower surgical corridors and increased risk of incomplete ethmoidectomy. Sphenoid pneumatization showed significant variability, including presellar, sellar, and postsellar types. Onodi cells were identified in 13% of cases, closely related to the optic canal. Septated sphenoids were present in 21%, often traversing the internal carotid artery canal.

Conclusion: Detailed anatomical understanding of posterior sinus morphology and variation is essential for safe and effective sinus and skull base surgery. This study provides a morphometric atlas to support individualized surgical planning.