Fibrous dysplasia of the temporal bone: imaging findings.

Lichtenstein [1] in 1938 coined the term fibrous dysplasia to describe a disorder characterized by the progressive replacement of normal bone elements by fibrous tissue. Histopathologically, these lesions consist of an abnormal proliferation of fibrous elements intermixed with haphazardly arranged trabeculae of woven bone. The disease can involve any bone in the body. In the head and neck, the skull and facial bones are involved in 10-25% of cases of monostotic fibrous dysplasia and in 50% of the polyostotic variety. Involvement of the temporal bone, however, is relatively rare, and only 53 cases have been reported. The three major radiographic classifications of fibrous dysplasia are pagetoid, sclerotic, and cystic. Any of these types may involve the temporal bone and related structures, including the external canal, middle ear, jugular foramen, or, rarely, the otic capsule. In this essay, we illustrate the radiographic features of the disease based on our experience with seven cases, seen at our institution since 1977, of fibrous dysplasia involving the temporal bone.