1. Mastoid antrum, aditus ad antrum, mastoid air cells Adnexa oculi

2. The mastoid Antrum (plural: mastoid antra) (also known as tympanic Antrum or Valsalva Antrum) is an air space (up to 1 cm in size) lying posterior to the middle ear and connected to it by a short passageway, the aditus ad Antrum.