Osteolytic intra-osseous meningiomas: illustrated review.

While bone invasion and hyperostosis are frequent phenomena in meningiomas, primary intra-osseous meningiomas are rare. With only 15 reported cases, the osteolytic form of primary intra-osseous meningiomas is most uncommon. Its occurrence in the skull base is an extra-ordinary exception. We have reviewed and categorized the pertinent literature on intra-osseus meningiomas with special emphasis on osteolytic tumours and discuss their clinical implications on the basis of a new case located in the petrous bone without contact with the meninges. It is concluded that due to their different clinical, radiological and pathological features, hyperostotic and osteolytic variants of intra-osseus meningiomas should be distinguished from tumours with soft tissue components and from en-plaque lesions.