Objective: Vermian fossa (VF) is a shallow fossa of varying size which may occasionally be found on dorsal as- pect of foramen magnum. Our aim was to find out frequency of VF and to measure length and width of the deter- mined VF’s and to classify them according to their shapes.
Materials and methods: We examined dry bones of collections of the Anatomy Departments of Istanbul Univer- sity Istanbul Faculty of Medicine and Dokuz Eylul University Faculty of Medicine. Totally 129 separate occipital bones and 29 basicraniums were inspected. We searched for existence of a fossa on the inner surface of the squ- amous part of the occipital bone, posterior to foramen magnum and determined the frequency of VF. We measured the height and width of each VF by a digital caliper and calculated mean values of them. We classified the VF’s de- termined in two groups according to their shapes. The VF’s which resembled a triangle were classified as type 1, and the VF’s which resembled a quadrangle were accepted as type 2.
Results: We found that 13 of the 158 (8.22 %) occipital bones had a VF. The average height and width of VF we- re determined as 27.8 mm and 18.4 mm, respectively. Type 1 and type 2 were determined in 7 and 4 cases, respec- tively. Two VF’s were atypical.
Conclusion: As there is not enough information about frequency of VF in literature and as there is no information about its size and shape, we believe that our results will provide additional information.
Key words: Occipital bone, vermian fossa, middle cerebellar fossa of Verga, vermis