What is meningioma
Meningioma is a generally benign tumor of the meninges (tissues that cover and protect the central nervous system). It can compress adjacent brain tissues and manifest singly or in multiple lesions. It is one of the most common tumors of the central nervous system.
It most often affects people between 40 and 60 years, but it can appear sincechildhood or in older adults. It is the only one of the most common brain tumors among women.
The tumor can develop in any portion of the dura, but most often occurs over the convex parts, near the venous sinuses, at the base of the skull, in the posterior fossa, and in the ventricles. It does not directly invade the brain, but it can compress it and/or the cranial nerves, which can block the absorption of CSF.
The causes of meningioma are not defined.
Meningiomas are classified into three grades by the WHO (World Health Organization), according to their characteristics, which are:
- Grade I meningioma – slow-growing benign tumor, the most common of the three types;
- Grade II meningioma – atypical and benign tumor that has a higher risk of recurrence after removal; and
- Grade III meningioma – an atypical, cancerous tumor that grows rapidly.
Meningioma symptoms and signs
Many meningiomas are asymptomatic. When they do have symptoms, they usually depend on where the tumor is:
- Symptoms of meningioma at the frontal region of the head – loss of vision, of smell and change of behavior;
- Symptoms of meningioma at the posterior region of the head – change in coordination; and
- Symptoms of meningioma at the base of the skull – difficulty speaking, swallowing or moving the tongue.
There are symptoms of meningioma common to all places where it can occur: headache, vomiting, loss of strength and sensation. Spine-related neurological symptoms can also indicate the presence of a meningioma.
In older people, it can cause dementia.
The diagnosis of meningiomas, like other brain tumors, is performed by magnetic resonance imaging with paramagnetic contrast.
CT scans or plain x-rays taken for other reasons may indicate bone abnormalities (such as brain atrophy, hyperostosis around brain convexities, tuberculum sellae changes) and incidentally indicate the presence of a meningioma.
Asymptomatic and small tumors, especially in older people, do not need treatment. Follow-up with periodic imaging exams is sufficient.
Grade I meningiomas are only treated with surgery and observed, as the risk of recurrence is low. On the other hand, grade II and III meningiomas present a higher risk of local recurrence, requiring a post-surgical complementary treatment with radiotherapy.
Radiotherapy can be used with IMRT technique (modulation of the X-ray beam) and conventional fractionation (small dose per day for 30 days) or with radiosurgery technique with stereotaxis (conformation to the tumor, decreasing the dose margin around with precision maximum and high doses in a few or a single day). Its choice, as well as the total and daily dose, is performed by the specialist doctor (radio-oncologist) after careful evaluation of each case.
In cases where surgery can cause more damage than the tumor, and therefore is contraindicated, radiotherapy alone can be used for treatment. Fit in here:
- Large meningiomas;
- Invasion of blood vessels (usually adjacent veins); and
- Proximity to critical brain regions (such as the brain stem).
As the cause of meningioma is not defined, there is no way to prevent it.