Groove for occipital sinus

The groove for occipital sinus starts at the internal occipital protuberance and runs downward and forward along the internal occipital crest. This groove forms a shallow bony depression called the vermian fossa as it reaches the posterior margin of the foramen magnum. From this point, the groove goes on as the marginal sinus grooves along the sides of the foramen magnum. The groove for occipital sinus houses the occipital venous sinus, which extends downward and forward from the confluence of sinuses. It splits into two to continue as the marginal venous sinuses along the edges of the foramen magnum.