CraniofacialMorphometric Associations with Frontal Sinus Hypoplasia/Aplasia in Adults: Orbital and Upper Facial Differences on CT

Background/Objectives: To evaluate whether frontal and maxillary sinus hypoplasia/aplasia are associated with differences in CT-based craniofacial morphometric measurements in adults. Methods: This retrospective case–control study included adults who presented to the otolaryngology outpatient clinic and underwent paranasal sinus CT at a single institution between 3 April 2023, and 30 May 2024. Of 3000 CT scans reviewed, 117 adults with frontal and/or maxillary sinus hypoplasia/aplasia and 53 healthy controls met the eligibility criteria. The sinus variation groups included unilateral frontal sinus variation (UFSV, n = 46), unilateral maxillary sinus variation (UMSV, n = 13), and bilateral frontal sinus variation (BFSV, n = 55); and bilateral maxillary sinus variation (BMSV, n = 3), which was described descriptively but excluded from the main statistical comparisons because of the very small subgroup size. Craniofacial morphometric distances were measured using standardized anthropometric landmarks, and group comparisons were performed using analysis of covariance adjusted for age and sex. Results: Significant adjusted between-group differences were found for left orbital breadth (p = 0.0001), left orbital height (p = 0.0250), right orbital breadth (p < 0.0001), biorbital breadth (p < 0.0001), upper facial breadth (p = 0.0204), and bizygomatic breadth (p = 0.0026). In general, the UFSV and BFSV groups showed lower adjusted values for orbital and upper facial measurements, whereas the healthy control and UMSV groups showed relatively higher adjusted means. No significant between-group differences were observed for the remaining measurements. Conclusions: Frontal sinus hypoplasia/aplasia, particularly unilateral and bilateral frontal sinus variation, was associated with selected differences in craniofacial morphology, especially in the orbital and upper facial regions, rather than demonstrating a direct effect. These findings may help to characterize craniofacial morphometric patterns in adults with sinus variation and could be considered in radiologic evaluation and preoperative assessment, but require confirmation in larger studies.