Size of the human mastoid air cell system.

Abstract

The area of mastoid pneumatization was measured on 68 children's ears and, after simple mastoidectomy, the cavity volume was determined. Another measurement was made utilizing the dural tegmen and sigmoid plate laminae as limiting structures. This “laminal limits'' figure corresponded well with cavity volume, but in small children the air cell area was significantly smaller. Several factors are responsible for absent or poor pneumatization: if infection starts in infancy, mastoid pneumatization does not start or is arrested until normal conditions prevail in the middle ear. Mastoiditis in small children may result in marked new bone formation and subsequent sclerosis, and air cell formation fails to penetrate this barrier even if the middle ear is restored to normal. In a well pneumatized ear, persisting infection in the mastoid process causes obliteration of the cells already existing and the end result resembles cases of primary arrested pneumatization.