[The "normal" pneumatization of the temporal bone].

Radiographs of the mastoids and the petrous pyramids of ear-healthy adults were investigated to ascertain the normal appearance of the temporal bone pneumatisation. The radiographs included those of patients with skull trauma, provided that these subjects had had no signs or symptoms of middle ear disease or hearing loss before the trauma. The extent of pneumatisation of the mastoid and petrous pyramid ranged from small cell groups around the mastoid antrum to extensive cell formations in the squamous temporal bone, in the apex of the petrous pyramid and in the retrosinus area. The planimetric measurements did not correspond to a normal distribution. It was also striking that ears could be found among these healthy individuals with irregular, asymmetric or indistinct pneumatisation, probably as a residual of sub-clinical middle ear disorders during the development of the cell system. After eliminating these irregular findings the ears with exclusively regular, symmetric and clear cell pictures also did not follow a normal distribution. Rather, they resulted in a typical curve with a steep ascent rising from a functionally-necessary minimum of about 4 cm2 to mean values of 8-12 cm2, and then a wide distribution reaching a value of 26 cm2. All these can be taken as genetically-determined "normal variants". The irregular cell-formations were seen mainly in the smaller pneumatised mastoids, so that it can be concluded that exogenous influences have at some time disturbed the pneumatisation process.(ABSTRACT TRUNCATED AT 250 WORDS)