A meningioma is a benign tumor that grows from the tissue that covers the brain called the "arachnoid membrane." The tumor grows from outside the brain, not from within the brain. Meningiomas are usually slow growing and can frequently be present without causing any symptoms.
However, if the tumor grows significantly, it can start to push on the brain and cause abnormal brain function. Dr. Neal Naff, chief of neurosurgery at St. Joseph Medical Center, discusses the condition and how to treat it.
* Women are nearly twice as likely as men to develop these tumors, which almost exclusively occur to adults with peak incidence around age 45. They are the most common benign brain tumor in patients older than 40. They also happen more frequently to patients with neurofibromatosis, an inherited nerve tissue disorder.
* Symptoms usually arise only when the tumor compresses against the brain tissue enough to cause abnormal function of the surrounding brain tissue. Therefore, symptoms vary depending on the tumor's location.
If the tumor is pressing on the part of the brain that controls muscle movement or sensation for the opposite side of the body, it may cause weakness or a change in sensation in the legs or arms. If the tumor arises near the nerve to the eye or the area of the brain that interprets visual input, it may cause vision changes. The tumor can also irritate the surrounding brain tissue and generate a seizure, which is marked by uncontrollable contractions in one side of the body. Interestingly, meningiomas are generally not painful and rarely cause headaches.
* When meningiomas cause symptoms, treatment is usually surgery to remove the tumor. The complexity of the surgery varies depending on the tumor's location. Tumors located in areas that are difficult to safely reach with surgery can be treated with highly focused beams of radiation, through a technique known as radiosurgery. Many tumors are discovered "incidentally," meaning they are found on a brain imaging study that was performed for another reason, such as an injury. If it is determined that the meningioma is not causing symptoms and is not particularly large, the tumor may be "followed conservatively," which means watching it with repeat MRI studies and intervening with treatment only if it grows significantly or begins causing symptoms.
* Although most tumors are successfully removed and completely cured through surgery, there can be complications caused by damage to the brain tissue surrounding the meningioma. This can produce a variety of symptoms, such as weakness, sensory changes, visual changes or seizures. Radiosurgery is much less likely to cause immediate complications, but radiosurgery takes much longer to shrink the tumor than when it is removed surgically.