Modified radical mastoidectomies as gas pockets.

An analysis of 45 adult ears which underwent a modified radical mastoidectomy showed: (a) in practically all these ears a variable amount of air was present behind the tympanic membrane; (b) this air was in continuation with the Eustachian tube; (c) two-thirds of the ears showed a collapse of part of the tympanic membrane--located predominantly in the posterior superior parts of the middle ear. These findings indicate that these atelectatic ears are gas pockets which are not closed, yet suffer from an imbalance of gas diffusion--from or into the middle ear.