Mastoid pneumatization in secretory otitis. Further support for the environmental theory.

A cohort of 222 randomized healthy children was followed with 7 repetitive tympanometries from the age of 4 to the age of 7 years. At the age of 8, the size of the mastoid air cell system in 17 children with normal tympanometric profiles and in 27 children with pathological tympanometric profiles, indicating secretory otitis, was examined by planimetry. The air cell system was significantly larger in the normal group than in the abnormal group, strongly indicating the validity of the environmental theory of pneumatization.