No one wants to hear a doctor say, "It's a brain tumor." But what most of us don't realize is that for the majority of people who hear these words, the diagnosis is not a death sentence.
Meningioma is the most common kind of brain tumor-and the majority of these, 85%, are benign. This does not mean that these tumors are not harmful or do not cause serious problems. But understanding of these tumors has advanced, and research is ongoing to determine why these tumors occur and in whom—and this has produced new detection and treatment options.
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What Are Meningiomas?
Meningiomas are tumors that do not grow within the brain tissue itself, but on the meninges, the membrane that covers the brain and lines the spinal cord. Commonly, meningiomas develop between the upper surface of the brain and the skull.
Meningiomas also can occur on the skull base including forming in the bones at the bottom of the skull and the bony ridge in the back of the eyes.
Symptoms can occur as the meningioma grows large enough to exert pressure on the brain or if it irritates the surrounding areas. Depending on its location and which brain areas and nerves are disrupted, symptoms may include blurred vision, impaired hearing or sense of smell, loss of balance or facial pain or numbness. Symptoms such as headaches, seizures, muscle weakness and/or memory loss may also occur.
Who Is Affected?
Meningiomas are two to three times as common in women as in men and are found more frequently in blacks than in any other ethnic group. The higher rate among women has led scientists to wonder whether hormones might play a role—and whether hormone treatment may increase risk.
So far, the data from large population studies in both the US and Finland have found no connection between oral contraceptives and meningiomas and no more than a weak association between postmenopausal hormonereplacement therapy (HRT) and the occurrence of brain tumors.
A large 2011 study that looked at lifestyle factors suggested that the risk for meningioma after menopause rose for women who were overweight but dropped slightly for active women.
The Cause Is Unknown
Researchers are still working on what causes meningiomas. One area of interest is radiation. Several studies have shown that very large amounts of radiation appear to increase the risk for these tumors. Most susceptible are children and young adults who had high doses of radiation to treat a previous cancer. A connection between cell-phone use and meningioma has not yet been determined.
Now researchers at Brigham and Women's Hospital and Yale University are using genetic analysis to help understand why some individuals develop meningiomas after radiation exposure while other people do not.
A study that was published in the journal Cancer in 2012 suggested that there may be a connection between bitewing dental X-rays and meningioma, but the evidence is not definitive. For now, the best advice is simply to have dental X-rays no more often than is necessary.
Diagnosis Of Meningiomas
Sometimes, meningiomas are diagnosed by accident, even before they cause symptoms—for example, in the course of examination for an unrelated problem such as head trauma.
For other patients, meningiomas are not diagnosed until they have been growing for years and reached a substantial size. Slow-growing tumors are almost always benign and rarely become cancerous.
When symptoms (such as those mentioned earlier) make physicians suspect a meningioma, they turn to computed tomography (CT) and magnetic resonance imaging (MRI), with contrast dye to better see the tumor, for diagnosis.
Recent progress: The development of powerful magnets has made MRI scans far more precise than they were in the past-and they are able to detect brain tumors that might have been missed a few years ago.
Once found, not all meningiomas need to be treated. Physicians may opt for the "watchful waiting approach for small, benign tumors that do not create symptoms.
Researchers are studying these benign tumors. At Johns Hopkins, they are looking at the genetic differences between benign meningiomas that stay benign and those that become malignant. This will help doctors determine which tumors need treatment and when it is safe to wait and watch a tumor.
Surgery may become necessary if symptoms develop or if periodic brain scans show that the tumor is starting to grow rapidly. The usual surgical treatment is removal of the entire tumor.
Major advances: With image-guided surgery, the surgeon uses CT or MRI as a kind of 3-D internal GPS to tell him/her just where the tumor ends and to navigate around blood vessels and neural structures.
This type of advance makes it possible to remove tumors that would previously have been considered too risky to remove, and to remove them more completely, making recurrence less likely. The use of intraoperative CT and MRI in the operating room enables surgeons to verify that the entire tumor has been removed.
Sometimes the location of the tumor makes surgery impossible. For instance, a meningioma in the middle of the skull base is likely to be surrounded by crucial nerves and blood vessels that make surgery too risky.
In cases like these, radiation therapy (also called radiotherapy) is used. Radiation therapy has also advanced. Today, stereotactic radiosurgery uses imaging and computerized programming to precisely target high-intensity radiation to the tumor while limiting damage to nearby brain tissue. Gamma Knife, CyberKnife and similar methods deliver this type of concentrated radiation. Stereotactic radiosurgery usually keeps tumors from growing but only occasionally shrinks them.
One possible side effect is brain swelling, which can cause symptoms such as headaches or neurological problems such as seizures or loss of balance.
Antinausea Drug Stops Brain Tumor Growth
Emend, a medication that reduces nausea from chemotherapy, blocks the action of substance P, an inflammatory substance in brain tumors. This discovery may result in a new treatment.
Chemotherapy plays a small role in meningioma-it is reserved for aggressively malignant or recurrent tumors that cannot be treated effectively with surgery or radiotherapy alone.
Research is ongoing to develop new drugs. At Johns Hopkins, scientists have identified a molecular pathway within meningioma cells that spurs their growth-and this could lead to the development of drugs to block their growth.
Researchers at Harvard Medical School, Memorial Sloan-Kettering Cancer Center and elsewhere also are testing medications approved for pancreatic and gastrointestinal cancers with hopes of identifying more effective chemotherapy for those meningiomas that do become ag. gressive or recurrent.