Anatomic Variations of Ethmoid Roof and Risk of Skull Base Injury in Endoscopic Sinus Surgery: Statistical Correlations

Background: Recent developments in endoscopic sinus surgery (ESS) have increased the need to investigate the complex anatomic variations in the ethmoid roof and skull base, to inform the surgeon about the risk of damaging these crucial areas during ESS. Objective: To offer a detailed description of sinus anatomy focusing on the key surgical landmarks in ESS and frontal recess surgery to standardize a systematic approach during the preoperative sinuses imaging evaluation. Methodology: A total of 220 computed tomography (CT) scans were reviewed to obtain six sets of measurements: the depth of the cribriform plate (CP); the length of the lateral lamella of the cribriform plate (LLCP); the angle formed by the LLCP and the continuation of the horizontal plane passing through the CP; the position of the anterior ethmoidal artery (AEA) at the skull base; the extent of frontal sinus pneumatization (FSP); the type of superior attachment of the uncinate process (SAUP). Results: The length of the LLCP was statistically significantly correlated with the different Keros classification types, the angle formed by the LLCP with the continuation of the horizontal plane passing through the CP, and with the AEA position at the skull base. The depth of the olfactory fossa was correlated with FSP. Conclusions: According to the Keros and Gera classifications, the data obtained from these evaluations allow the assessment of anatomic-radiological risk profiles and can help identify those patients who are high risk for ethmoid roof injury.