Overview

A meningioma is a type of tumor that develops from the meninges, the membrane that surrounds the brain and spinal cord. There are three layers of meninges, called the dura mater, arachnoid and pia mater. Most meningiomas (90%) are categorized as benign tumors, with the remaining 10% being atypical or malignant. However, the word "benign" can be misleading in this case, as when benign tumors grow and constrict and affect the brain, they can cause disability and even be life threatening.
In many cases, benign meningiomas grow slowly. This means that depending upon where it is located, a meningioma may reach a relatively large size before it causes symptoms. Other meningiomas grow more rapidly, or have sudden growth spurts. There is no way to predict the rate of growth for a meningioma, or to know for certain how long a specific tumor was growing before diagnosis.

Most people with a meningioma will only have a tumor at only one site, but it is also possible to have several tumors growing simultaneously in different parts of the brain and spinal cord. When multiple meningiomas occur, more than one type of treatment may have to be used.

Meningiomas are most common in people between the ages of 40 and 70. They are more common in women than in men. Among middle-aged patients, there is a marked female bias, with a female: male ratio of almost 3:1 in the brain and up to 6:1 in the spinal cord. Meningiomas are very rare in children, with pediatric cases accounting for only 1.5% of the total.

Meningiomas may cause seizures, headaches, and focal neurological defects, such as arm or leg weakness, or vision loss. Patients often have subtle symptoms for a long period before the meningioma is diagnosed. Sometimes memory loss, carelessness, and unsteadiness are the only symptoms.
Diagnosis is made by a contrast enhanced CT and/or MRI (magnetic resonance imaging) scan. While MRIs are in some ways superior, the CT can be helpful in determining if the tumor invades the bone, or if it’s becoming hard like bone.

What difference does the location of the tumor make?

Convexity meningiomas

These grow on the surface of the brain, often toward the front. They may not produce symptoms until they reach a large size. Symptoms of a convexity meningioma are seizures, focal neurological deficits, or headaches.

The falx is a groove that runs between the two sides of the brain (front to back), and contains a large blood vessel (sagittal sinus). Parasagittal tumors lie near or close to the falx. Because of the danger of puncturing the blood vessels, removing a tumor in the falx or parasagittal region can be difficult. Large parasagittal meningiomas may result in bilateral leg weakness.

Olfactory groove meningiomas grow along the nerves that run between the brain and the nose. These nerves allow you to smell, and so often tumors growing here cause loss of smell. If they grow large enough, olfactory groove meningiomas can also compress the nerves to the eyes, causing visual symptoms. Similarly, meningiomas growing on the optic nerve can cause visual problems, including loss of patches within your field of vision, or even blindness. They can grow to a large size prior to being diagnosed due to changes in the sense of smell and mental status changes being difficult to catch.