Skull base pneumatization: evaluation of vidian canal and adjacent anatomical structures using high resolution multislice computed tomography.

PURPOSE: To investigate the prevalence and key anatomical features of structures that have critical role in planning and performing endoscopic skull base surgery. MATERIALS AND METHODS: We reviewed high-resolution skull base CT images of 640 consecutive subjects that were referred to Dicle University, School of Medicine, Department of Radiology between February and July 2014. Studies with artifactual degradations, space-occupying skull base lesions or prominent and moderate sinonasal pathologies, and those younger than 18-years- of age were excluded. 171 subjects included for further investigation. RESULTS: Sellar configuration was the most frequent pneumatization type of sphenoid sinuses. 50% of sphenoid sinuses had single midline septum formation and showed lateral extension of pneumatization. Mean length of Vidian canal was 16 mm for both genders. The most common rostral-caudal course of Vidian canal was medial to lateral and was followed by straight course. The frequency of pneumatization pattern was found as type 0, III, II and I, respectively. In most of instances, petrous ICA was located superior to Vidian canal and both structures were visible on same axial slice. 25% of subjects had Onodi cell and ACP pneumatization. Pneumatization of PCP was observed in 5% of subjects. Approximately 20% of ICAs were protruded into sphenoid sinus. In 3% of instances there was no bony covering of ICA. 11% of optic nerves were protruded into sphenoid sinus. 5% of optic nerves had dehiscent bony covering. 4% had both protrusion and dehiscence. CONCLUSION: In the present retrospective observational study, we devised previously described classification and approach models and demonstrated key anatomical features of critical skull base structures.