Meningioma

Meningioma is the most common primary intracranial tumor, arising from the arachnoid cells that line the meninges — the three-layered membranous covering of the brain and spinal cord. The overwhelming majority are benign (WHO grade 1) and grow slowly, often over many years. Despite this, meningiomas can cause significant neurological symptoms depending on their size and location, and they require careful long-term monitoring even after complete surgical removal.

Meningiomas are incidentally discovered with increasing frequency as MRI use has become more widespread, and many are managed conservatively with surveillance imaging. Treatment decisions are highly individualized, balancing tumor size, growth rate, location, patient age, and neurological symptoms.

The WHO classification defines three grades of meningioma. Grade 1 (benign) tumors represent the majority of cases and encompass a range of histological subtypes. Grade 2 (atypical) meningiomas represent a smaller proportion of cases; they carry higher rates of recurrence than grade 1 tumors and often require adjuvant radiation therapy following surgical resection. Grade 3 (anaplastic or malignant) meningiomas are rare and behave aggressively, with a high risk of local recurrence and, occasionally, metastatic spread.

Many meningiomas — particularly small ones — produce no symptoms and are found incidentally during brain imaging performed for an unrelated reason. When symptoms do occur, their nature is determined by the tumor's location within the central nervous system.

Meningiomas along the cerebral convexities (the outer surface of the cerebral hemispheres) may cause seizures or focal neurological deficits such as limb weakness. Parasagittal and parafalcine meningiomas (near the midline) often produce leg weakness. Sphenoid wing meningiomas may affect vision and eye movement as they impinge on the optic nerve or cranial nerves in the cavernous sinus. Olfactory groove meningiomas may cause gradual loss of smell and personality changes. Meningiomas compressing the optic chiasm or nerves produce visual field defects, while posterior fossa meningiomas can cause hearing loss, balance problems, and swallowing difficulty.

The underlying cause of most meningiomas is unknown, though several factors have been consistently associated with their development.

Therapeutic ionizing radiation to the head — particularly higher-dose irradiation delivered decades earlier for conditions such as scalp ringworm, childhood leukemia, or prior brain tumors — is a well-established risk factor, accounting for approximately five to ten percent of meningiomas. 

Meningiomas are approximately twice as common in women as in men.

No specific preventive measures are established for sporadic meningioma. Minimizing unnecessary cranial radiation exposure, particularly in children and young adults, reduces the risk of radiation-induced meningioma in later life. Individuals with known NF2 (Neurofibrmatosis Type 2) mutations benefit from regular MRI surveillance to detect meningiomas at an early, more manageable stage.