This tumor is the most common non-malignant, non-glial primary brain tumor. Even so, although the majority are benign, a small subset of these tumors are malignant. They are more common in women and in patients with neurofibromatosis type 2.
90% of meningiomas are benign and are easily resected if they are found to be growing superficially on the dura.
This tumor is thought to arise from arachnoid villi, which are projections of arachnoid tissue that are involved in CSF absorption.
These tumors can arise anywhere along the dura and therefore often have a dural attachment.
These tumors are most commonly found in the parasagittal region, but can also be found in the falx and hemispheres.
Given their variable location, meningiomas can compress a range of intracranial structures and therefore present with an array of signs & symptoms. Involvement of the parasagittal region can compress the motor cortex and result in contralateral leg weakness.
Meningiomas may cause seizures as a result of compression on brain tissue resulting in abnormal neuronal excitability. Examples of other focal neurologic signs include unilateral vision loss with compression of the optic tract, or hearing loss with compression of the cerebellopontine angle.
Histological examination often shows psammoma bodies which are concentric, ring-like patterns of calcification characteristic of meningiomas. The tissue appears in a whorled pattern. Spindle-shaped cells may also be seen.
Calcifications or concretions may be seen on histological specimens. CT or MRI imaging typically show a dural-based mass which may contain calcifications.
Meningiomas can often incite an osteoblastic reaction in the overlying cranial bone resulting in increased bone density. This hyperostosis is not well understood, though theories include a reaction of the bone to the tumor itself, as well as invasion of the bone by the tumor.
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