Dear Doctor: I've recently been diagnosed with meningioma, but my doctor tells me not to worry about it. That can't be right. What should I know?
Dear Reader: Meningiomas are the most common brain tumors within the central nervous system, and most are considered benign. As the name implies, meningiomas arise from the meninges, the layer of membranes that surrounds the brain and the spinal cord. Approximately 26,000 new cases are diagnosed each year, often found incidentally -- meaning they're detected via brain imaging for symptoms not related to the tumor. The likelihood of an incidental meningioma increases as a person gets older. In fact, a 2016 study of MRIs performed in 5,800 healthy adults with an average age of 65 found that 2.5 percent had meningiomas.
Ionizing radiation, a history of breast cancer, obesity and a family history of meningiomas are all risk factors for this type of tumor.
Of meningiomas, 80 to 90 percent are classified as grade 1, meaning they're slow-growing because the cells within them don't replicate rapidly. This is most likely the type of meningioma that you have. An additional 10 to 15 percent of meningiomas are classified as grade 2, meaning the cells within them replicate more rapidly and are more likely to invade local structures, making them more dangerous. A final 1 to 3 percent of meningiomas are considered grade 3, because the cells within them replicate very rapidly. These types of cancerous meningiomas are more difficult to treat and can spread to distant sites.
A CT scan or an MRI of the brain should be able to detect signs that indicate whether a meningioma is atypical or malignant, such as by assessing whether the tumor has swelling around it or whether it's invading the bone.
If your doctor says you have no reason to be concerned, that's probably because the meningioma is in an area where it isn't compressing any portion of the brain. Some meningiomas, even though they are grade 1, are located in an area of the brain where they compress nerves. This can lead to alterations in vision, loss of hearing or smell, even weakness of the arms and legs and, rarely, if the tumor blocks the movement of fluid within the brain, confusion. Lastly, meningiomas increase the risk of having seizures; this risk appears to be more common in men.
That said, meningiomas occur more often in women than in men. One interesting aspect of meningiomas is that they have receptors for progesterone and estrogen. Theoretically, taking hormone replacement after menopause could incite tumor growth. Although research has not supported this specific connection, some studies have shown a slightly increased rate of meningiomas among women who did hormone replacement. So, if you are undergoing such therapy, I would recommend stopping it.
If indeed your tumor is grade 1 and not compressing any vital structures of the brain, I -- like your physician -- would caution against any surgical or radiation treatment for the tumor. Obviously, such treatments have side effects, and the benefit wouldn't be worth the risk. That said, you should follow up with regular MRIs -- first on a yearly basis. If there's no change in the size of the tumor after three to five years, then you can lengthen the interval in between MRIs.
In the meantime, stay calm and know that, as your doctor said, there's likely no cause for alarm.
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