FOSSA OCCIPITALIS MEDIANA

Abstract

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Background. Fossa occipitalis mediana is a more correct term for fossa vermiana, a small depression above the foramen magnum, at the inferior divergence of the falx cerebelli. Aim. The aim was to determine the prevalence and parameters and define the norm of the inferior margin of the crista occipitalis interna/sulcus sinus occipitalis to prevent confusion with fossa occipitalis mediana. Material and Methods. 1042 dry skulls from collections of anatomical departments in the Czech Republic were examined. The fossa variants were classified into five categories. Results and Discussion. The norm (missing fossa) was present in 710 (68.1%) skulls, the fossa occipitalis mediana was recorded in 309 (29.6%) - its type I in 264 (25.3%) and its type II in 45 (4.3%) - and other rare variants were registered in 23 (2.21%) of specimens. Conclusions. Bony variants are closely related to the soft tissue variants and their knowledge is principal during surgical approach for preventing hemorrhage from dural venous sinuses.