A clinical-radiographic classification of skull base lesions.

Lesions involving the base of the skull can be divided into primary and secondary disease processes. The primary group consists of bone lesions more often seen elsewhere in the skeletal system while the secondary group consist of those lesions extending to the base of the skull by direct extension from adjacent intracranial or extracranial sites. The purpose of this paper will be to arrive at a classification of skull base lesions based on the roentgen localization of the disease process. The base of the skull because of its anatomically variable curvature can be difficult to evaluate on good quality conventional radiographs. In addition to the changing angles of the bone itself, the overlying soft tissues of the pharynx and neck only serve to further conceal areas of bone pathology. The advent of polytomography and CAT scanning has greatly aided the evaluation of this region which clinically is extremely difficult to assess. In some instances invasive modalities such as angiography and posterior fossa myelography are necessary to define the lesion. With these diagnostic methods available, rather than discovering classical patterns of disease, a variety of disease processes have been found that radiographically mimic each other. Similarly, on a purely clinical basis, many of the disease entities present in a similar fashion. It is only by a combined approach that an intelligent differential diagnosis can be offered.