Association of sphenoid sinus pneumatization patterns, Onodi cells, and rostrum pneumatization with natural ostium location: A cross-sectional CT study

Endoscopic management of sphenoid sinus pathologies requires a meticulous understanding of the regional anatomy to avoid injury to adjacent critical structures. Since the natural sphenoid ostium provides a consistent and preferred entry point, clarifying its position relative to various pneumatization patterns is essential for successful surgical planning. This study aimed to investigate the relationship between the location of the sphenoid sinus ostium and sphenoid sinus pneumatization patterns, including the presence of Onodi cells and pneumatization of the sphenoid rostrum, using computed tomography (CT). We conducted a cross-sectional descriptive study of paranasal sinus CT scans of 181 adult patients (362 sphenoid sinuses, both sides analyzed separately) at a tertiary ear–nose–throat hospital. Sphenoid sinus pneumatization was classified in the sagittal plane as presellar, sellar, or postsellar, and in the coronal plane as Type 1 (previdian), Type 2 (intercanal), or Type 3 (post rotundum) based on the degree of lateral extension. The presence of Onodi cells and pneumatization of the sphenoid rostrum (anterior sphenoid beak) were recorded. We measured the horizontal and vertical diameters of the sphenoid ostium, along with distances to adjacent landmarks: D1, superior border of the ostium to the skull base; D2, inferior ostium to the superior border of the choana; D3, medial ostium to the nasal septum; D4, lateral ostium to the orbital wall; and D5, sphenoid sinus roof to floor (sinus height). The study found that all sphenoid sinuses had a single natural ostium, with mean horizontal and vertical diameters of 1.25 mm and 1.82 mm, respectively. Onodi cells (141/362 sinuses, 39%) were associated with a significantly greater ostium-to-choana distance (D2: 11.77 vs 10.00 mm, P  <.001). A pneumatized sphenoid rostrum (53%) was the strongest predictor of non-medial ostium placement (OR = 15.86, P  <.001), while extensive lateral pneumatization (Type 3) was associated with medial ostium displacement (OR = 0.32, P  = .002). Sphenoid sinus pneumatization patterns and anatomical variations, such as pneumatized sphenoid rostrum and Onodi cells, were significantly associated with the location of the ostium. Preoperative CT evaluation of these variations may assist surgeons in anticipating ostium positioning and planning safer endoscopic approaches.