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]
Variation
The position and size of this foramen are very variable.[1][3] It is not always present.[1][3] Sometimes, it is duplicated on one side or both sides.[1] Sometimes, it is situated in the occipital bone, or in the suture between the temporal bone and the occipital bone.
