A Novel Classification System for the Anatomical Variations of the Infraorbital Ethmoidal (Haller) Air Cells

Background: Infraorbital ethmoidal air cells (IOEAc) are ethmoidal cells that pneumatizes inferior to the orbital floor and lateral to a line parallel to the lamina papyracea. Studies have shown considerable anatomical variation with different extensions in humans. Objectives: To identify and categorize the anatomical variations of the IOEAc creating a new, comprehensive variation classification system. Patients and methods: All included 1260 computed tomography of the nose and paranasal sinuses were reviewed to detect the presence or absence of IOEAc. All cases with IOEAc were evaluated for bilaterality, multiplicity, and shape and categorized according to its extensions to the maxillary infundibulum and its relations to the entire length of the inferior orbital wall. Results: IOEAc were identified in 173 (13.7%) scans. Bilaterality was observed in 99 patients (57.2%), while 50 patients (28.9%) had unilateral air cells on the right and 24 patients (13.9%) had unilateral air cells on the left. They were classified into 5 categories that were subclassified into subtypes. With 173 cases distributed as 26%, 17.9%, 3.5%, 9.8%, 24.9%, 10.4%, 2.3%, 1.7%, and 3.5% among the 5 categories, respectively. Conclusions: The new classification system provides a comprehensive classification of the described anatomical variations of the IOEAc. It allows the description and categorization of variants identified in past and future studies. It is applicable to current clinical practice.