Comparison between the area and the volume of the air-filled ear space.

The area of the air-filled ear space, assessed planimetrically, was compared with the volume in cases with chronic otitis media with central perforation or recent traumatic perforation of the tympanic membrane. A significant correlation between the area and volume existed. In chronic otitis media the area was larger than in cases with traumatic perforation with equal volume. In these cases the area does not correlate completely with the volume of the functioning air space. The results favour the hypothesis that the pneumatisation of the temporal bone is affected by infection.