Meningiomas are the most common non-glial primary tumor of the CNS. Meningiomas are also the most common extraaxial primary tumor of the CNS. They represent 15-25% of all intracranial primary tumors. Most patients are in the 5th and 6th decades (40's - 50's). The 2x-4x female predilection is most likely due to hormone receptors for progesterone and estrogen.

The tumor arises from the arachnoid cap cells and is usually a slowly growing intradural intracranial mass, with a broad base of attachment to the overlying dura. Hyperostosis of the overlying skull occurs in 15-25% of cases and may be a "sympathetic reaction" - or - can indicate invasion of the skull.

Meningiomas are the 4H Plus tumor:
H - hemispheric
H - homogeneous
H - homogeneously enhancing
H - hyperdense (CT)
H - hyperostosis
H - hormonally reactive (progesterone/estrogen)