Case report 680. Intraosseous meningioma of the sphenoid bone.

Two cases of intraosseous meningioma of the calvaria with hyperostosis are presented and compared with the appearance on plain films and CT of en plaque meningioma, metastatic disease from such primary sites as prostatic cancer, and fibrous dysplasia. It is emphasized that intraosseous meningioma in the calvaria is relatively uncommon, occurring most often in the sphenoid bone (probably because of its numerous articulations). The relationship of the development of intraosseous meningioma to the entrapment of dura containing arachnoid cells is discussed in considering the cause of such lesions, and it is stressed that calvarial fractures and cranial sutures may contribute to the entrapment of arachnoidal tissue and later the formation of a meningioma.