gms | German Medical Science

Objective: Meningiomas tend to appear with calcifications or even as complete osseous masses on imaging. However the intraoperative appearance does not always correlate as some of these meningiomas are psammomatous in nature and easy to mobilize. We evaluate preoperative imaging in this sub entity of meningiomas.

Methods: Out of a database of more than 3000, six meningiomas of the posterior fossa were identified with complete osseous-like appearance in contrast to reactive hyperostosis or intraosseous infiltration of the temporal bone. Radiological, clinical and intraoperative features of this special entity were evaluated.

Results: Although stone-like meningiomas had various appearances on imaging, comparing the intraoperative consistency with the CT-scan appearance showed that the psammomatous meningiomas were hyperdense in the soft-tissue window and “corny” in the bone-window scan. True osseous meningiomas were less hyperdense in the soft-tissue window and had various layers, more heterogenic and with "compacted" segments. However, the calcified psammomatous bodies were so dense that MRI imaging could not distinguish between true osseous formation and calcified meningioma gravel.

Conclusions: Although osseous-like on imaging, the frequent presence of psammomatous bodies in meningiomas can give a false impression of a hard, true osseous tumour. CT-scans should be analysed carefully so that the indication for surgery will not be influenced.Generally stone-like meningiomas are psammomatous and therefore intraoperatively manageable, allowing an excellent postoperative result.