Mastoid antrum

Last revised by Daniel J Bell on 9 Jul 2020

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.

The superior wall or roof of the mastoid antrum is known as the tegmen mastoideum, which continues anteriorly as the tegmen tympani.

Peripherally, the antrum intercommunicates with multiple, variably-sized, smaller air spaces extending down to the tip of the mastoid process, the mastoid air cells.

The inner surface of the antrum is covered by a mucous membrane, which is in continuity with that of the middle ear. 


The mastoid antrum is already at its adult size at birth.

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