Relationship between sphenoid sinus volume and protrusion of internal carotid artery and optic nerve: a 3D segmentation study on maxillofacial CT-scans.

Anatomy of sphenoid sinuses has acquired a growing importance with the diffusion of transsphenoidal surgical procedures. A common risk in these practices is the damage of internal carotid artery (ICA) and optic nerve (ON), which may protrude into the sphenoid air cavities. This study aims at analysing the relationships between sphenoid sinuses volume and protrusion of ICA and ON. 260 head CT-scans were retrospectively analysed (equally divided among males and females, age range 20-92 years). Volume was segmented through ITK-SNAP software. In addition, the subjects were classified into four groups: no protrusion of any structure (group 1), protrusion of ICA (group 2), protrusion of ON (group 3), protrusion of both ICA and ON (group 4). Possible statistically significant differences in prevalence of the four groups according to gender were assessed through Chi-squared test (p < 0.05). Differences in volume between the four groups were assessed through one-way ANOVA test (p < 0.05), separately for males and females. Group 1 was the most frequent (40.0%), followed by group 4 (27.7%) and group 2 (18.5%), without any difference according to gender. For what concerns volume, cases of ICA and concomitant ICA + ON protrusion had significantly larger sinuses, whereas isolated ON protrusion did not modify sinus volume. Results show that protrusion of ICA is positively related with the volume of sphenoid sinuses, whereas the same relation was not verified for ON: surgeons should accurately consider possible ON protrusion in each case, as it may occur independently from sphenoid sinuses volume.