Mastoid pneumatization. Evidence of the environmental theory.

Forty-one randomized, otherwise healthy children with tympanometry were observed from birth until the age of 6 years. At a total of 13 trials, tympanometry and otoscopy were performed. The tympanometric profile was correlated to the size of the mastoid air cell system, as determined by planimetric measurement of roentgenograms taken at age 6 years. There was a notable correlation between the size of the cell system and the tympanometric profile. Thus, the least affected ears with mostly normal or slightly abnormal tympanometry had considerably larger cell systems than the most affected ears with secretory otitis and tubal dysfunction. The findings support the environmental theory of pneumatization.