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.
Treatment & Risks
Each patient and tumor is unique and requires a team of specialists that work together to develop a customized treatment plan. Depending on the location and size of the tumor, your personalized team may include one or more of the following specialists:
• Neurosurgeon: A physician trained in surgery on the nervous system, especially the spine and the brain.
• Neurotologist (also known as an otoneurologist): A specialist in cranial base and ear surgery.
• Neuro-ophthalmologist: A specialist specializing in diseases affecting vision.
• Radiation oncologist: A physician who specializes in the treatment of cancer patients, using radiation therapy as the main method of treatment.
Treatment of a meningioma is often done in stages, depending on the size and location of the tumor. Treatments can include observation, surgery and radiation.
1. Observation: If a meningioma is found when it is very small and causing few, if any, symptoms, physicians may choose to simply monitor the tumor over time. Observation with regularly scheduled MRI scans (see Diagnostic Procedures) is usually the only action necessary.
2. Surgery: Meningiomas that grow near the brain’s surface are often easily accessible for surgical removal. In some instances, however, the tumors may press or grow deeper within the brain, making surgery more difficult. Cedar-Sinai specialists rely on advanced surgical procedures to effectively and safely remove meningiomas, including:
• Endovascular Neurosurgery: Tumors rely on blood supplies that feed their growth and allow tumor cells to multiply. Endovascular neurosurgery techniques cut off these blood supplies (also known as embolization) before surgery. This helps to make actual neurosurgery much safer, makes removing the tumor easier and lowers the risk of significant blood loss. Cedars-Sinai specializes in endovascular neurosurgery; these highly specialized techniques are not available at all hospitals.
• Image-Complete Resection: This type of surgery removes the entire tumor so that it is no longer visible on an MRI scan. A clear MRI is just one of many factors determining a successful surgical outcome.
3. Radiation: In certain situations, surgery may not be an 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. In these cases radiation may be an appropriate treatment, either alone or following surgery. 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 and other lesions that are in close proximity to the spinal cord or other vital structures. The goal of either approach is to bombard the tumor with a destructive dose of radiation while minimizing damage to healthy tissue.
Diagnostic Procedures & Grading
There are two main methods used to diagnose a meningioma: various imaging studies and neurovascular angiography. Biopsies are rarely needed.
1. Imaging Studies: Because meningiomas usually grow in specific areas – usually along the brain’s outer edge – and have fairly recognizable characteristics, imaging studies are typically the best ways to make a diagnosis. These can include, but are not limited to, the following scans:
• MRI (Magnetic Resonance Imaging): A non-invasive scan that reveals detailed images of the brain and its surrounding nerves and tissue.
• CT Scan: While a surefire diagnosis comes from an MRI scan, a CT scan (computed tomography) can also help identify the exact location and size of the tumor. A CT scan uses X-rays to make detailed images of structures inside the body.
2. Neurovascular Angiography: A minimally invasive procedure that uses 3D imaging to allow surgeons to evaluate and treat problems in blood vessels of the brain.
The World Health Organization divides meningiomas into three categories:
1. Grade I (Benign): About 90 percent of meningiomas are non-cancerous, also known as benign. They include angiomatous, fibrous, lymphoplasmacyte-rich, meningiothelial, microcystic, metaplastic, psammomatous, secretory, and transitional meningiomas.
2. Grade II (Atypical): Around five precent of meningiomas are classified as Atypical or Grade II, because their cells look abnormal under a microscope. Atypical meningiomas grow faster than benign meningiomas and are more likely to re-grow (also known as recur) after being removed.
3. Grade III (Malignant): 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.
The choice of treatment depends on several factors, including the patient’s overall health and the size, type and location of the tumor – specialists 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. This procedure can potentially make surgery safer, ease tumor removal, and lower risk of significant blood loss. Cedars-Sinai specializes in endovascular neurosurgery; these highly specialized techniques are not 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™ Systemprovides highly focused, image-guided radiotherapy and radiosurgery for treating meningiomas and other 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 ranked among the nation's leaders for Neurology and Neurosurgical services in U.S. News and World Report's annual list of America's Best Hospitals. 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.
Meningiomas grow very slowly and conform to the space around them, often going undetected for years. However, this also means they may grow to be very large before causing any noticeable symptoms. Symptoms eventually occur when a tumor puts pressure on brain tissue or other structures like the optic nerve (which controls sight) or important veins that allow blood to flow within the brain.
Common symptoms include:
• Nausea and/or vomiting
• Muscle weakness
• Loss of movement or sensation in a specific area
• Changes in mood and sleep
• Vision problems like blurriness or double-vision
• Hearing loss
• Slurred speech