Do Anatomical Variations Affect the Location of Solitary Sphenoid Sinus Fungal Balls? A 10-Year Retrospective Study

Background and Objectives: Sinonasal fungal balls (FBs) most commonly occur in the maxillary sinus, followed by the sphenoid sinus (SS). Relatively little is known about the predisposing factors and pathogenesis of unilateral sphenoid sinus fungal balls (SSFBs) compared to maxillary sinus FBs. We investigated whether anatomical variations have clinical implications for the location of unilateral SSFBs.Methods: This study included 33 patients who underwent endoscopic sinus surgery for unilateral SSFBs between 2010 and 2021. Preoperative computed tomography scans were used to analyze the presence of anatomical variations, including sphenoid lateral recess, complete accessory septum of the SS, types of SS pneumatization, anterior and posterior nasal septal deviation (NSD), cephalocaudal NSD, concha bullosa (CB), Haller cell (HC), paradoxical middle turbinate (MT), everted uncinated process (UP), and Onodi cell.Results: The presence of HC (33.3% vs. 12.1%, p=0.04), complete accessory septum of the SS (51.6% vs. 25.8%, p=0.04), and the sellar type of the SS (90.9% vs. 50%, p=0.003) differed significantly according to the presence or absence of FBs in the SS. However, other anatomical variations, including NSD, CB, paradoxical MT, everted UP, Onodi cell, and sphenoid lateral recess, were not significantly associated with the presence of unilateral SSFBs (all p>0.05). In the multivariable analysis, only sellar-type pneumatization of the SS showed a statistically significant relationship with SSFB, not the combined conchal and presellar type (adjusted odds ratio, 8.96; 95% confidence interval, 1.27–63.19; p=0.03).Conclusion: We demonstrated that unilateral SSFBs were most strongly associated with the ipsilateral type of SS pneumatization, followed by the presence of HC and a complete accessory septum of the SS. Intranasal anatomical variations may play a significant role in the location of unilateral SSFBs.