Vena obelionica alias occipital emissary foramina- an osteological study in north indian population

The occipital emissary foramen or vena obelionica is occasionally present as a solitary foramen in the squamous part of occipital bone at external occipital protuberance. It transmits occipital emissary vein which connects occipital sinus with the sub occipital venous plexus. Variations occur with regard to number and location. The aim of the present study was to ascertain the aforesaid parameters in North Indian population and compare it with the data available in the literature. One hundred and sixteen dry adult human skulls and occipital bones with intact foramen magnum of both sexes with unknown age group were obtained from in the neuroanatomy section of the of anatomy department, LLRM Medical College Meerut, and surrounding medical colleges Uttar Pradesh, India. The occipital emissary foramen was present in 29/116 (25%) skulls. In (7.7%) skulls the foramina was located on EOC. In (6 %) it was located on the right side, (10.3%) on left side and in (8.6%) it was median in position. Bilateral foramina were observed in (1.7%). The occipital emissary vein if present becomes significant in procedure like sub-occipital craniotomy where it becomes susceptible to injury.