High resolution CT evaluation on the morphologic characteristics and variations of foramen ovale and adjacent foramina in the skull base

PURPOSE: To evaluate the morphologic characteristics and anatomical variation of the foramen ovale(FO) and its relationship with adjacent foramina. MATERIALS AND METHODS: We evaluated 305 HRCT studies of the temporal bone in patients without having any disease that might alter the foraminal anatomy. This study focused on the variations in presence, shape, size, location and relationship with each other. RESULTS: The shapes of FO were 6 types(ovoid :75.2%, pyriform, elongated, round, polygonal and figure of 8). The average size was 7.4mm 1.3 in long diameter and 4.3mm 0.9 in short diameter. The position of the posterior margin of FO in respective to the line connecting the both mandibular fossa of temporal bone was various(on the line:62.3%, anterior:30.2%, posterior:7.5%). FO had communication with the foramen spinosum (FS) in 4.1% and with the foramen vesalius(FV) in 1.9%. FV was present in 47.5%(bilateral: 26.2%, right:10.2%, left:11.1%). The shapes were round or ovoid. The distance from the midline was 18.9mm 1.7. No data showed statistically significant differences between right and left. There was no inverse relationship between the presence of FV and the size of FO. Three continuous sections in one patient showed variations in the formation of foramen ovale and foramen spinosum ;one pyriform shaped foramen ovale and one foramen spinosum on the lower section, one round shaped foramen ovale and two foramen spinosum on the midsection, assimilation of two foramen spinosum into one elongated foramen spinosum on the upper section. The canaliculus innominatus was observed in 9%. CONCLUSION: Skull base foramina of the middle cranial fossa have various shape, size, location, presence and relationship with each other. It is important to recognize foraminal varients not to misinterprete as disease.ope