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What is a meningioma?
Meningiomas arise from the meninges, the layer of cells that cover the brain and spinal cord, and account for approximately 30% of all brain tumors. 85% of meningiomas represent a benign, non-cancerous tumor. However, in rare cases, they can degenerate into a cancer.
Causes & Risk Factors
There is no obvious cause of a meningioma; most are sporadic or random diseases. However, this type of brain tumor is more common in women than men, with a 3:1 ratio, and in people between the ages of 40 and 70. Other risk factors include:
Genetic inheritance of neurofibromatosis, a rare nervous system disorder which can cause benign tumors throughout the body
Exposure to radiation, such as was given in the 1950’s to control head lice in some countries. Radiation therapy to the head can be used to treat an infection of the scalp or tumors of the head, brain or neck
Overall, 99% of meningiomas represent pure chance. There does not appear to be any link to smoking, diet, or other lifestyle risks that are associated with other types of tumors.
Signs & Symptoms
Meningiomas compress parts of the brain or spinal cord as they grow, often achieving great size before they put enough pressure on the brain or spine to cause any symptoms at all. Most often, meningiomas are found incidentally on MRIs. If symptoms do present, they generally appear slowly and may be slight at the onset.
Typical symptoms a patient might notice include:
Loss of sense of smell
Loss of hearing
Loss of coordination
In spinal meningiomas, difficulty walking and clumsiness in the hands will typically be among the first things patients notice. Very rarely, a large tumor can cause a stroke.
Most often, meningiomas are found incidentally on MRIs leading from a patient visit that was unrelated to the meningioma itself. Because meningiomas arise separately from the brain itself, they usually display a very sharp border between the brain and tumor both on MRI imaging and on microscopic appearance. The microscopic appearance of the tumor determines its grade, a measure of how cancerous the tumor is. The majority of meningiomas are grade I, benign tumors, but occasionally can be grade II (atypical) or grade III (malignant), which are more cancerous.
Grade I – Benign meningioma: Represent 78-81% of meningiomas. Benign meningiomas are non-cancerous and are recognized for their slow growth and distinct borders.
Grade II – Atypical meningioma: Represent 15-20% of meningiomas. Atypical meningiomas are made up of tumor cells that do not appear typical or normal. They have a higher recurrence rate and tend to grow faster. They are neither malignant (cancerous) nor benign, but may become malignant in the future.
Grade III – Malignant or anaplastic meningioma: Represent 1-4% of meningiomas. This is an aggressive type of brain tumor, most often invading the parts of the brain closest to the tumor.
The treatment for a meningioma depends on several factors: the location of the brain tumor, whether the tumor is benign or malignant, and the patient’s general health and preferences.
The majority of meningiomas can be cured or controlled through a combination of surgery and radiation therapy. The mainstay of therapy for meningiomas is surgical removal. Because meningiomas arise from the covering over the brain, rather than the brain itself, they can usually be successfully removed through an operation known as a craniotomy. The type of craniotomy and approach used by the surgeon to access and remove the tumor depends on its location in the brain, with the risks of surgery generally increasing for larger tumors and for tumors that grow closely to critical brain structures such as major blood vessels and nerves. In some instances the risk of injuring these critical structures may prevent a surgeon from removing a tumor in its entirety.
In the event that a tumor can’t be removed completely or for small tumors that are found asymptomatically, another approach that is very successful uses stereotactic radiosurgery with tumor control rates >90%. Additional radiation and/or chemotherapy is sometimes also prescribed for tumors in the grade II or grade III classes if they fail to respond or are resistant to surgery and radiosurgery.
Sometimes very small tumors require no treatment at all. It is not uncommon to find tumors on CT or MRI scans that are ordered for other reasons. If the tumor is small and is not causing any symptoms, doctors may decide to observe and monitor it by taking pictures of it every 6-12 months to make sure it’s not growing, holding off on any surgery or treatment until the tumor shows signs that it is actively getting bigger.
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