Volumetric Analysis of the Onodi Cell in Relation to Perisphenoidal Anatomical Variations

<strong>Objective:</strong> This study aimed to evaluate the presence and volume of the Onodi cell (OC) and to investigate its anatomical relationship with surgically important neighbouring structures such as the optic canal (OCa), internal carotid canal (CC), and vidian canal (VC), focusing on canal types and bony dehiscence. <strong>Materials and Methods:</strong> High-resolution computed tomography (CT) scans of 110 patients were analysed, with 220 sphenoid sinus sides evaluated. Onodi cells were identified and classified based on their location. Their volumes were measured using manual segmentation in the OSIRIX software. The types of OCa, CC, and VC, as well as the presence or absence of bony dehiscence in these canals, were radiologically assessed. Statistical analyses were performed to evaluate the relationships between the OC volume, canal configurations and dehiscence status. <strong>Results: </strong>The OC was present in 30% of cases. Its presence was significantly associated with higher-risk OCa types (Types 3 and 4) and with optic nerve dehiscence. Onodi cell volume was significantly greater in patients with type 3 OCa and type 3 CC. Internal carotid artery and VC dehiscence were also more common in cases with larger OC volumes. <strong>Conclusion:</strong> This study is one of the few to quantitatively assess OC volume and its associations with nearby critical neurovascular structures. The findings emphasise that both the presence and size of the OC are important anatomical considerations that should be carefully evaluated preoperatively using high resolution CT to reduce the risk of complications in endoscopic sinus surgery.