Relationship between sphenoid sinus volume and accessory septations: a 3D assessment of risky anatomical variants for endoscopic surgery

Sphenoid sinus accessory septations involve serious complications during their removal for the injury of the internal carotid artery (ICA) and the optic nerve (ON). The relationships of this anatomical variant with sphenoid size still remain to be analysed. Two-hundred and sixty patients (male:female ratio 1:1, aged between 18 and 92 years) were retrospectively assessed. Number of accessory septations and their relationship with ICA and ON was recorded. From each CT-scan the 3D model of sphenoid sinuses was extracted. Pearson's coefficient was calculated to assess a possible correlation between the volume of sphenoid sinuses and the number of septations, separately in males and females (p < 0.05). Sex-related differences in prevalence of septations inserted onto ICA or ON were assessed through Chi-square test (p < 0.05). Differences in volume between patients with and without ICA or ON septal insertions were assessed through Mann-Whitney, separately for males and females (p < 0.05). In most of cases two septations were found (24.6%), whereas only 21.9% of patients did not show any septum. ICA and ON septal insertions were found in 20.8% and 7.7% of cases, respectively. Number of septations significantly increased with sinus volume, both in males and in females (p < 0.001). Moreover, volume was significantly higher in patients with ICA septal insertion (p < 0.001), whereas no differences were found between subjects with and without ON septal insertion (p > 0.05). The present study first proved that septations and probability of ICA insertion are related with sphenoid volume. On the other side, ON insertion does not depend upon sphenoid sinuses size.