Tegmental and petromastoid defects in the temporal bone.

Fifty temporal bones were examined using the temporal bone dissecting microscope. 34 per cent were found to have defects in the tegmen and petromastoid segments, resulting in communications between the cranial cavity and the middle ear cleft. However, no defects were found in the overlying dura. This may have an important bearing on the intracranial spread of infection from the middle ear cleft, even in the absence of any bony destruction due to chronic middle ear disease.