Meningiomas account for about 25% of primary brain tumors: Mayo Clinic Health Letter

Meningiomas, the most common type of brain tumors, are rarely cancerous and may not require treatment. The July issue of Mayo Clinic Health Letter offers an overview of this brain tumor that is usually benign.

Meningiomas account for about 25 percent of primary brain tumors, those that originate in the brain. They are formed from the cells that provide a protective coating (meninges) that lines the outer surface of the brain and spinal cord. They typically grow outside brain tissue and rarely grow into the brain. The cause is unknown.

Symptoms: Meningiomas easily can go unnoticed, with no signs or symptoms. They may exert pressure on the brain and cause symptoms that can include vision changes, seizures, loss of hearing, weakness in the arms or legs or changes in balance.

Diagnosis: Diagnostic imaging -- particularly MRI -- is useful to identify the size and location of the tumor. On an MRI scan, meningiomas have a very characteristic appearance. Because many meningiomas don't cause symptoms, they often are detected during imaging for some other, unrelated purpose.

Treatment: Ninety percent of meningiomas are benign, slow-growing tumors. If no bothersome symptoms are present, periodic monitoring for changes may be all that's needed.

When meningiomas are causing symptoms, growing rapidly or are cancerous, several treatment options are available. The tumor can be removed during surgery. Depending on the location, removing the entire tumor may not be possible. When that's the case, another step in treatment may be radiosurgery or radiation therapy.

In stereotactic radiosurgery, narrow beams of radiation are directed simultaneously at a small tumor, usually no bigger than an inch. Another approach is radiation therapy over a period of weeks. Radiation therapy is considered when tumor removal isn't complete or surgery is not possible.

Overall, treatment outcomes are good for benign meningiomas after complete surgical removal. Tumors that can't be totally removed due to their location are more likely to recur. However, in those cases, when radiotherapy or radiosurgery is done in combination with surgery, recurrence rates also are low.