Meningiomas are tumors of meninges, which are the protective coverings of the brain and the spinal cord. The tumor usually comes from the arachnoid cap cells, one of the three meningeal layers, different from the dura mater and pia mater.
Meningiomas are benign tumors of meninges. Conversely, invasive meningiomas are the malignant variant of the meningeal tumors. Malignant meningiomas are rare, while benign meningiomas are quite common; actually, the most common benign tumors of the central nervous system. They constitute 20 to 25% of all primary intracranial neoplasms. The cause or risk factors for developing meningiomas are genetic mutations leading to downregulation (loss of function) of the tumor suppressor gene called NF2, in the long arm of chromosome number 22.
NF2 codes for a membrane protein called merlin, which promotes cell to cell communication for growth inhibition (contact inhibition between the neighboring cells). Loss of this gene leads to an overgrowth of the affected cell. They are usually slow-growing tumors, but malignant change can appear very quickly. The meningiomas may be solitary or multiple.
The clinical presentation of the meningiomas depends of its location in the brain, its size, invasiveness, relation with surrounding tissue, and its grading (graded from 1 to 4 by the WHO). The common site of meningiomas in the brain in its cortical dura mater, or the parasagittal sinus. It can also develop at the sphenoidal ridge, supra-sellar, sub frontal, cavernous sinus, occipital lobe, cerebellopontine angle, optic nerve, sphenoid wing, foramen magnum or olfactory groove. They are commonly seen in adulthood, and they are more prevalent in women than men, increasing its incidence with age.
Clinical features can be as follows:
Asymptomatic
Initially, when the tumor is small, it doesn’t affect the normal functions of the brain and is diagnosed during a routine examination.