The mastoid foramen is a hole in the posterior border of the temporal bone. It transmits an emissary vein between the sigmoid sinus and the suboccipital venous plexus, and a small branch of the occipital artery, the posterior meningeal artery to the dura mater.

The mastoid foramen is a hole in the posterior border of the temporal bone of the skull.^[1]

The opening of the mastoid foramen is an average of 18 mm from the asterion,^[2] and around 34 mm from the external auditory meatus.^[3] It is typically very narrow.^[1][3] This may be around 2 mm.^[3]

The mastoid foramen transmits:

• an emissary vein between the sigmoid sinus and the suboccipital venous plexus or the posterior auricular vein.^[1][2]
• a small branch of the occipital artery, the posterior meningeal artery, to the dura mater.^[2]