Variations in Paranasal Sinus Anatomy: Implications for the Pathophysiology of Chronic Rhinosinusitis and Safety of Endoscopic Sinus Surgery

Objectives: To study the radiologic anatomy of the paranasal sinuses in patients with and without chronic rhinosinusitis to assess whether anatomic variations are associated with disease pathology, and to identify those variants that may impact operative safety. Setting: Tertiary referral otolaryngology unit. Main Outcome Measures: Incidence and nature of anatomic variants with potential impact on operative safety, and the presence or absence of sinus mucosal disease and its correlation with anatomic variants with a potential impact on mucociliary clearance. Methods: We reviewed 278 computed tomographic scans from patients with rhinosinusitis symptoms to investigate anatomic variations that may predispose to sinusitis or impact on operative safety. The incidence of variants with potential impact on sinus drainage was compared between patients with and without sinus mucosal disease with logistic regression. Results: A closed osteomeatal complex was identified in 148 patients (53%), followed by concha bullosa in 98 patients (35%). Closed osteomeatal complex and nasal polyposis were independent risk factors for sinus mucosal disease. Anatomic variants with a potential impact on operative safety included anterior clinoid process pneumatization (18%), infraorbital ethmoid cell (12%), sphenomaxillary plate (11%), and supraorbital recess (6%). In 92% of patients, the level difference between the roof of the ethmoid cavity and the cribriform plate was Keros I. Conclusions: Bony anatomic variants do not increase the risk of sinus mucosal disease. However, anatomic variants with a potential impact on operative safety occur frequently and need to be specifically sought as part of preoperative evaluation.