Unusual primary intraosseous meningioma, mimicking cranial osteoid osteoma: A radiological clue to the differential diagnosis

Primary intraosseous meningioma of the skull is rare. We report a patient who presented with a history of an enlarging scalp mass over 30 years. Noncontrast computed tomography demonstrated a densely calcified right frontal extra-axial mass lesion. Magnetic resonance imaging of the lesion demonstrated heterogeneous hypointensity on T1-and T2-wieghted images and without evidence of gadolinium contrast enhancement. And the mass showed heterogeneous isointensity on diffusion weighted image. Preoperative diagnosis for the lesion was osteoid osteoma of the right frontoparietal bone, and total excision of the tumor was carried out. Histological examination showed intraosseous meningothelial meningioma. We should be aware of the primary intraosseous meningioma showing the classical radiological findings of cranial osteoid osteoma. The radiological clue for the accurate diagnosis is discussed