Intraspinal osteogenic meningioma: report of a case.

Dense calcification and psammomatous bodies are common in spinal meningioma, but are rarely reported in osteogenic meningioma. We present a 73-year-old woman with an extramedullary, intradural tumor located at the T5 vertebra. The tumor showed mixed intensity and heterogeneous enhancement on the T1-weighted image and hypointensity on the T2-weighted image, and was situated near the spinal nerve root. The tumor's initial symptom was myelopathy, as is usual with spinal meningioma. We successfully removed the tumor under microscopy and found it to be separated from the vertebral column by the epidural space. The symptoms and signs improved gradually after the operation. Because the pathologic examination revealed areas of lamellar bone with bone marrow in the transitional meningioma, and because these were not related to the psammomatous bodies, osteogenic meningioma was diagnosed. Metaplasia of arachnoid cells is considered to be the putative etiology of osteogenic meningioma.