Prevalence of the uncinate process, agger nasi cell and their relationship in a Taiwanese population

Objectives: The uncinate process (UP) and the agger nasi (AN) cell are both important anatomical landmarks in endoscopic sinus surgery. The superior attachment of the UP and the prevalence of the AN cell show great anatomical variability and affect the anatomy of the frontal recess. The aim of this study was to investigate the superior attachment types of the UP, the presence of the AN cell, and the relationship between the two. Method: Two hundred sixty-four sides of 132 patients with identifiable superior attachments of the UP were selected from our 2007-'08 computed tomography (CT) scan records. Exclusion criteria were previous nasal or paranasal sinus surgery, neoplastic disease, and a history of nasal trauma. The superior attachment type of the UP and the prevalence of the AN cell were evaluated. Three case series from the English-language literature were selected for racial comparison. Results: Single insertion of the UP into the lamina papyracea was the most common type (70.4%). The other types of UP superior attachment were found to have the following distribution: 10.2% into the middle turbinate; 7.6% into the lamina papyracea and the skull base; 6.1% into the skull base, 4.9% into the lamina papyracea and the middle turbinate; and 0.8% into the middle turbinate and the skull base. The distribution of the UP insertion types with respect to ethnicity was statistically significant (p < 0.01). The AN cell was found in 216 (81.8%) of 264 sides. The AN cell was present bilaterally in 95.3% of the cases (206 sides, 103 patients) and unilaterally in 4.7% (10 sides). The prevalence of the AN cell according to superior attachment of the UP types was not statistically significant (x₂ = 8.6, p = 0.126). Conclusions: The nasofrontal anatomy did show some variations among different races. The single superior attachment of the UP into the lamina papyracea had the highest prevalence. The AN cell was found to be present in 81.8% of cases. The relationship between the presence of the AN cell and the superior attachment types of the UP was not statistically significant.