The sphenoid sinus, foramen rotundum and vidian canal: a radiological study of anatomical relationships.

INTRODUCTION: The sphenoid sinus is an important structure in ventral skull base surgeries that is surrounded by several vital anatomical structures including the internal carotid arteries, optic nerve and cranial nerves inside the cavernous sinus. In addition, the foramen rotundum is a small canal deeply situated in the base of the skull, which represents the way for exit of the maxillary nerve. Understanding of the sphenoid bone anatomical relationships is central to the expanded endonasal approaches to the skull base. OBJECTIVE: To record and analyze the measurement indexes of the sphenoid sinus and foramen rotundum in the coronal plane of normal computer tomography scans. METHODS: Patients underwent paranasal sinuses computer tomography scan from June 2014 to November 2015 were retrospectively entered this cross-sectional study. We obtained several morphometric measurements from both the right and left sides using computer software. We also classified foramen rotundum and vidian canal types and determined position of the foramen rotundum regarding to base of lateral pterygoid plate. RESULTS: One-hundred patients with the mean age of 38.56±18.51 years entered this study. Mean bilateral FR distances were 38.48±3.87mm. Average right and left FRs distances to midline were 19.00±2.07 and 19.34±2.17mm, respectively (p=0.03). Twenty-eight cases (28%) had type I vidian canal, 48% and 24% had type II and III vidian canals, respectively. Four patients (4%) had type I rotundum foramen, 28% and 44% had type IIa and IIb, respectively and 24% had type III rotundum foramen. The position of foramen rotundums regarding to the base of lateral pterygoid plate was online in 50% of cases, medially placed in 47% and laterally placed in 3% of cases. CONCLUSION: The results of this study can be used to provide a better anatomical understanding of the area, which is necessary for endoscopic skull base surgeons.