[Pneumatization of the petrous apex]

Pneumatization of the petrous apex was investigated in 226 subjects without middle ear disease by means of target imaging CT. The degree of pneumatization of all subjects was 32.7% (148/452 ears), but no difference in degree was revealed with distinction of bilateral ears or between sexes. In 148 ears with pneumatization of the petrous apex, a higher degree of pneumatization was found in larger mastoid cavities, suggesting that pneumatization of the petrous apex correlates with pneumatized air cells in other parts of the temporal bone. Pneumatization of all parts of the petrous apex was found in about 40% (58/148 ears), and of some parts in about 60% (90/148 ears). In the latter cases, pneumatized air cells were more often found in the lower portions of the CT slices than in the higher ones. These results indicate that pneumatization of the petrous apex must be taken into consideration in studies measuring the gas composition and volume of the middle ear.