More Common in Women: Do Hormones Play a Role?
Meningiomas are the most common primary tumors affecting the central nervous system. The vast majority of meningiomas are slow-growing, benign (noncancerous) tumors, although certain subtypes are more aggressive than others, and benign does not mean without risk. Depending on its size and location, a benign meningioma can cause significant injury, become life-threatening, and be extremely difficult to treat.
While benign meningiomas do not generally invade brain tissue, a growing tumor potentially compresses important structures. Many tumors, however, remain so small they go undetected throughout a person’s lifetime or are only coincidentally discovered if diagnostic imaging is performed for an unrelated reason.
Meningiomas grow from cells of the middle layer (arachnoid) of the meninges, the three membranes enveloping and protecting the brain and spinal cord. They often are found at the surface of the brain near the top of the head, at the base of the cranium (skull), and along the spinal cord
How Meningiomas Are Graded
The World Health Organization classifies 15 subtypes of meningiomas into three categories: benign (Grade I), atypical (Grade II) and malignant (Grade III).
About 90 percent of meningiomas are benign. They include: angiomatous, fibrous, lymphoplasmacyte-rich, meningiothelial, microcystic, metaplastic, psammomatous, secretory, and transitional meningiomas.
While cells of benign tumors look somewhat similar to normal cells under the microscope, cells of atypical meningiomas appear more abnormal, grow more quickly and have a higher recurrence rate. They also are capable of invading the brain. Atypical meningiomas make up an estimated five percent of all meningiomas and include atypical, chordoid, and clear cell sub-types.
Cells of malignant meningiomas appear even more abnormal, grow more quickly, recur more often, and are more likely to invade the brain and spread to other parts of the body. Papillary, rhabdoid and anaplastic meningiomas are considered malignant.
Meningiomas are the only brain tumors more common in women than men, suggesting the possibility that hormones sometimes play a role in the development of these tumors. Meningiomas affect people at all stages of life, but incidence increases in middle age.
Most meningiomas occur for no known reason, although risk is increased among people who have been exposed to radiation; studies are underway to determine if people engaged in certain occupations are at higher risk. A very small percentage of tumors are linked to a rare genetic syndrome known as neurofibromatosis.
If a patient has symptoms that could be caused by a meningioma or other type of brain tumor, a complete physical evaluation will be performed and imaging scans will be ordered. Because meningiomas typically occur in specific areas along the brain’s outer edges and have characteristic appearances, a diagnosis canusually be made using imaging studies alone. A biopsy is rarely needed.
Magnetic resonance imaging (MRI) is the most useful diagnostic tool in most cases, but computed tomography (CT) scans, X-rays and other images are also helpful in making a diagnosis and planning a course of treatment. Neurovascular angiography can be valuable in the diagnosis, treatment planning and surgical intervention of certain meningiomas; this minimally invasive procedure enables surgeons to evaluate and treat problems in the blood vessels of the brain using 3D imaging.
The choice of treatment depends on several factors, including the patient’s overall health and the size, type and location of the tumors. Professionals from a variety of medical fields work together on each patient’s case to select the best treatment option.
For a slow-growing meningioma that does not pose an immediate threat, long-term observation with MRI scans is commonly the only action necessary.Meningiomas growing near the brain’s surface are often easily accessible for surgical removal; it is not uncommon, however, for tumors to press into or grow from the wall of the superior sagittal sinus, a major vein at the top and back of the head. Similarly, meningiomas at the base of the cranium are often situated very deep and in close proximity to cranial nerves or the cavernous sinus, another large venous structure.
In addition to pressing against and constricting blood vessels, meningiomas – like other tumors – develop a blood supply to feed their growth. For many meningiomas, this blood supply is easily accessible in the dura (covering of the brain). For others, especially larger tumors and those located at the base of the skull, the blood supply may be deep. Through endovascular neurosurgery techniques, many such blood supplies can be “embolized,” or blocked off, before surgery to potentially make the surgery safer, ease tumor removal, and lower risk of significant blood loss. Endovascular neurosurgery techniques are not be available at all hospitals.
“Image-complete resection” – removal of the entire tumor visible on MRI – is one of the many factors determining overall effectiveness of treatment; Cedars-Sinai’s Brain Tumor Center provides state-of-the-art surgical facilities; our neurosurgeons are among a select few nationwide specializing in entire brain tumor removal.
In particularly challenging situations, additional specialists– such as an expert in the nerves and structures related to vision (neuro-ophthalmologist) or a surgeon specializing in nerves controlling balance and hearing (neurotologist) – may be called upon to advise in planning or assist in surgery.
In certain situations, surgery may not be a viable option. For example, the neurosurgical team may need to leave part of the tumor in place to avoid damage to a vital structure and the possibility of serious or life-threatening consequences.
Focused radiation, using stereotactic radiotherapy or stereotactic radiosurgery, offers customized treatment for certain tumors, either alone or following surgery. While radiosurgery is accomplished with a single, high dose of radiation, focused radiotherapy consists of “fractionated” treatments delivered in smaller doses over a period of days or weeks. The goal of either approach is to bombard the tumor with a destructive dose of radiation while minimizing damage to healthy tissue.
Cedars-Sinai’s treatment teams have several state-of-the-art focused radiation options. For meningiomas in the brain, the Gamma Knife® is an extremely precise, fixed system that uses up to 201 separate beams of radiation converging at a single point. The Trilogy™ System provides highly focused, image-guided radiotherapy and radiosurgery for treating meningiomas andother lesions that are in close proximity to the spinal cord or other vital structures.
Chemotherapy is not an effective option for most meningiomas and is usually reserved for tumors that resist other treatments and have a history of recurrence.
A Leading Center for Brain Tumor Treatment
With state-of-the-art technology and facilities, Cedars-Sinai’s Brain Tumor Center is among the nation’s top referral centers. The Center offers patient-centered collaboration among physicians and surgeons from a wide variety of specialty fields, and the experience and expertise of neurosurgeons specializing in complex and challenging brain tumor surgery.
Basic scientific research conducted at the Maxine Dunitz Neurosurgical Institute is translated into clinical trials at the Johnnie L. Cochran, Jr. Brain Tumor Center.
Cedars-Sinai is included in the “Best of the Best” Honor Roll of U.S. News and World Report, with Neurology and Neurosurgical services ranking in the top 20 nationally. For more than 20 years, Los Angeles area residents have named Cedars-Sinai the “most preferred hospital for all health needs,” according to National Research Corporation’s annual Healthcare Market Guide survey.
Because these tumors grow slowly and tend to conform to the space around them, it is possible for meningiomas to become very large before causing noticeable problems. Symptoms occur when an enlarging tumor presses on brain tissue or critical structures such as the optic nerve, damages veins, or causes abnormal bone growth.
Common symptoms include:
• Nausea and/or vomiting
• Muscle weakness
• Loss of movement or sensation in a specific area
• Changes in mood, sleep, vision, hearing or speech
Diagnosis is sometimes delayed by the fact that symptoms often become progressively worse over time and are initially dismissed as a normal part of aging.
A meningioma is not the only possible cause of these symptoms, but anyone experiencing one or more should consult a physician and, if necessary, be evaluated by a neurologist or neurosurgeon that can perform the appropriate diagnostic procedures.