A meningioma is a tumour of the meninges.
The skull protects the brain. Inside the skull, and covering the brain, are 3 thin sheets of body tissue. These are called the meninges and also help to protect the brain. This is the name given to the protective lining of the brain and spinal cord. It can occur in any part of the brain or spinal cord but the commonest sites are at the surface of the brain, either over the top or at the skull base.
Meningioma tumours are more common in older people and in women, although they may occur in men and in young people too.
The latest Cancer Research UK statistics show that between a quarter and a third (25-33%) of all primary brain tumours in adults is a meningioma.
Meningiomas do not spread. 90% of meningiomas are benign (non-cancerous), 6% are atypical, and 2% are malignant.
The word benign is misleading in this case as, when benign tumours grow and constrict the brain, they can cause disability and even be life threatening. A meningioma described as atypical is likelier to re-grow.
Meningioma symptoms vary a lot, depending on where in the brain they are growing. They can grow into surrounding brain tissue and may come back after they have been removed.
Approximately 90% of all meningiomas fall into the benign category. These tumours exhibit slow growth and very little multiplication of cells and very rarely invade the brain tissue. Overall, benign meningiomas are less likely to recur than the atypical and malignant grades.
Atypical meningiomas represent approximately 5% of meningiomas and exhibit increased tissue and cell abnormalities. These tumours exhibit a faster growth rate than benign meningiomas and, on occasion, some degree of brain invasion. Atypical meningiomas have a higher likelihood of recurrence than benign.
Malignant meningiomas account for approximately 3-5% of all meningiomas. These tumours show increased cellular abnormalities as well as a faster growth rate compared to benign and atypical meningiomas. Malignant meningiomas are the most likely to invade the brain and spread (metastasize) to other organs in the body. They are the most likely of the three types to recur.
This type of tumour is generally a slow-growing, localized mass which is actually located outside the structure of the brain but can compress the brain. These tumours can often be removed completely with micro-neurosurgical techniques, and may require no further surgical treatment. In some cases, these tumours are tucked away in areas that cannot be reached safely, or they are wrapped around critical structures such as the carotid artery or the optic nerve. In these situations, specialized radiosurgical or radiotherapy techniques might be considered to either shrink these tumours or stop their growth.
As you have read above, malignant (cancerous) meningiomas are extremely rare. It is also possible, but very rare, to have more than one meningioma. These multiples or clusters of meningiomas present special problems for patients and their doctors.
The most common locations in the brain
- Falx and parasagittal – The falx is a groove that runs between the two sides (hemispheres) of the brain (front to back). Running along the top of this groove is a large blood vessel, known as the superior sagittal sinus. Falx tumours arise from the meninges folded down in the groove, whereas parasagittal tumours arise from the meninges that are near or close to the superior sagittal sinus at the top of the groove.
- Convexity – These tumours grow on the surface of the brain not involving the falx or parasagittal region.
- Sphenoid wing (also called sphenoid ridge) – Sphenoid wing meningiomas lie behind the eyes.
- Olfactory groove – Olfactory groove meningiomas grow along the nerves that run between the brain and the nose.
- Suprasellar – These meningiomas grow above a bony depression that houses the pituitary gland and are very close to where the optic nerve from each eye intersects with the other.
- Posterior fossa – Posterior fossa tumours lie on the underside of the brain.
- Intraventricular – Intraventricular meningiomas are associated with the connected chambers of fluid that circulate throughout the central nervous system. This fluid is known as cerebro-spinal fluid (CSF).
- Intraorbital – Intraorbital meningiomas grow around the eye sockets of your skull.
- Spinal – Spinal meningiomas occur within the spinal cord predominantly in the region of the spine between the neck and abdomen (thoracic area).
As previously mentioned, 90% of meningiomas occur within the skull and the incidence at each location is given below:
|Falx or parasagittal||25%|
|Miscellaneous (e.g., optic nerve, which is involved in vision)||3%|
How often do meningiomas occur?
Because this is a rare condition, meningiomas generally do not occur often, they affect around 1 per 38,000 people. Their incidence increases with age, and they are most commonly found in middle-aged or elderly people, but they also affect younger people and teens.
The majority of meningiomas (over 90%) are grade 1 (benign), but some meningioma tumours recur or re-grow after apparently complete surgical resection. Atypical and malignant meningiomas are more likely to recur.
What causes meningiomas?
Like most brain tumours the cause of meningioma is unknown. In some people there may be an underlying genetic abnormality such as a mutation in a specific gene. Recent research has also shown a possible link between meningioma and breast cancer. Meningiomas frequently possess progesterone receptors and, less commonly, oestrogen receptors, which may explain their higher incidence in women.
What are the symptoms?
These can vary greatly, dependent on where the tumour is. Symptoms are caused by brain displacement or compression, not by invasion. However, these tumours can be so slow growing that they may go undetected for years. They can grow in and around cranial nerves that control function so that eyesight, taste, smell, sensation (numbness), swallowing or other movement may be affected. They may cause fits or muscle weakness. Sometimes sudden unexplained and/or recurrent severe headaches (which may be accompanied by nausea and/or vomiting) are the first symptom. Occasionally, an eye examination may reveal abnormalities, which lead on to further investigation and diagnosis.
What are the tests and investigations for?
In order to plan the correct treatment doctors need to get as much information as possible about the type, position and size of the tumour. Initially, a neurological examination will take place to assess any effect the tumour has had on the nervous system.
A CT scan or MRI scan will then be done to find the exact position and size of the tumour. MRI scans are the most widely used diagnostic tests since they are very effective in identifying even small meningiomas. The MRI scan usually includes injection of a contrast (a short-acting dye) in order to determine the exact position and size of the tumour. Occasionally, an angiogram will be done, where dye is used to show up the blood vessels in the brain and their relationship with the meningioma.
To confirm the exact type of tumour, a biopsy or sample of cells is taken from the tumour and examined under a microscope, but this is typically done at the time of surgical removal.
What Are The Treatment Options ?
The treatment of meningioma depends on a number of factors including your general health, the size and position of the tumour, and the rate of progression of the symptoms. Some tumours may be unsuitable for surgery.
Surgery – Where possible, surgery is the first form of treatment for meningioma and in many cases the tumour can be removed completely. So far this has been the principal form of treatment for meningioma and it is still so in many circumstances. Surgical resection of meningiomas always has some risk, and growth or size of the meningioma or the progression of the symptoms should justify the risk.
For meningiomas located near the surface of the brain, surgery is often the best option. For meningiomas that are deep (cavernous sinus, medial sphenoid wing, parasellar, skull base and clivus), complete surgical removal may not be possible or it may involve too much risk to the cranial nerves or blood vessels. In addition, meningiomas sometimes recur, especially those that are atypical (on the borderline between benign and malignant). Radiation therapy may then be used to control their regrowth, whereas radiosurgery is increasingly used instead of surgery to control small meningiomas.
Radiation therapy – Conventional radiotherapy may be used after surgery if the meningioma cannot be totally removed, in order to destroy any remaining tumour cells. Radiotherapy and radiosurgery have become a promising alternative to surgery in the treatment of surgically inaccessible meningiomas.
In RT (stereotactic radiotherapy or radiosurgery) a highly focused radiation is given, which precisely targets the tumour with little impact on healthy brain tissue. Radiation is administered in multiple smaller treatments over a number of weeks (often 30 sessions given over six weeks). This allows the overall total dose to be higher than in standard radiation, because it allows normal brain tissue to recover better. It stops tumour growth in the vast majority of cases and in some people it may even cause the tumour to shrink. Each treatment is called a “fraction” therefore this type of therapy is sometimes called “fractionated” therapy. Fractionated stereotactic radiosurgery is often called FSR.
Radiosurgery can be given either with a gamma knife or a modified linear accelerator. Gamma knife radiosurgery is generally a single treatment planned and delivered all in one day, but fractionated radiotherapy using a linear accelerator has overtaken it, as it is safer for most tumours, (though not all).
Chemotherapy – is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. Chemotherapy is very rarely used for treating meningioma although research continues into developing this form of treatment. The use of chemotherapy is limited by the fact that meningiomas are typically slow growing and therefore not very susceptible to chemo drugs.
Watch and Wait – Small, asymptomatic (few or no symptoms or signs) meningiomas can be carefully observed and followed with regular MRI scans. This can be an option where the tumour is slow growing, and it may be preferable, particularly in elderly patients, when there are no clinical signs (symptoms or impairments). A possible advantage is that better treatments and procedures may be available by the time treatment is needed.