Volumetric changes of the aerated middle ear and mastoid after insertion of tympanostomy tubes.

Volumetric changes of the middle ear and mastoid were measured monthly by the direct volumetric method in 28 ears from 21 patients (12 children and nine adults) with otitis media with effusion. The mean volumetric increase immediately after the insertion of the tubes was 1.56 ml and was attributed to the volume of effusion aspirated from the tympanic cavity and mastoid antrum. The volume increased significantly for three months (P less than 0.01). The increase was speculated to be due to disappearance of the mucosal edema and of effusion in the tympanic cavity and mastoid. The volumetric changes showed little increase thereafter.