Computed Tomographic Analysis of Frontal Recess Cell Prevalence According to International Frontal Sinus Anatomy Classification

Purpose: The frontal recess (FR) has a complex anatomy composed of a number of cells that dictate the frontal sinus drainage pathway. The International Frontal Sinus Anatomy Classification (IFAC) is a new system for classifying FR cells. This study investigated the prevalence and symmetry of IFAC cells in healthy sinuses and assessed the interrater agreement of IFAC cells. Methods 509 adult patients with non-diseased paranasal sinuses were included in this retrospective cross-sectional study. Two rhinologists independently identified IFAC cells on 1018 sides using triplanar CT reconstructions. The prevalence of each cell type was assessed, and interobserver agreement was measured using the kappa coefficient (κ). Results The prevalence of FR cells varied, with the agger nasi cell (ANC) being the most prevalent at 88.0% and the supra bulla frontal cell (SBFC) being the least prevalent at 7.1%. FR cells that pneumatize into the frontal sinus were identified in 28.6% of the FRs, with male patients having a significantly higher prevalence than female patients. The ANC had the highest bilateral incidence at 80.4%, while the SBFC had the lowest at 2.2%. All IFAC cells had excellent interrater agreement, with κ values ranging from 0.94 to 1.0. Conclusion The prevalence of FR cells varies among populations. Male patients were more likely to have FR cells that pneumatize across the frontal sinus. These results highlight the importance of considering population- and gender- specific prevalence rates of individual FR cells in endoscopic sinus surgery planning. IFAC is a reliable tool for identifying cells in the FR with a high level of interrater agreement.