Meningiomas are tumours of the meninges (covering of the brain and spinal cord). The meninges are a protective covering consisting of three layers, the dura mater, arachnoid membrane and the pia mater. Meningiomas are a primary brain tumour, meaning they do not usually metastasise (or spread) from another area, but originate in or on the brain. These tumours are relatively common and are usually slow growing and benign. A very small percentage of meningiomas are malignant.
The symptoms of a meningioma are caused by the pressure the growing tumour exerts on surrounding tissue or the swelling they incite. These tumours can occur in a variety of places and therefore cause a wide range of symptoms, although they tend to occur in specific regions around the brain.
Depending on the location of the tumour, meningiomas may cause headaches, nausea, seizures, weakness or numbness in the limbs or face, visual problems, and gradual changes in mood or personality. The symptoms tend to increase in severity as the tumour grows in size.
Imaging studies are used in the diagnosis of meningiomas. Computed tomography (CT) and magnetic resonance imaging (MRI) scans are used to provide increased levels of detail.
Classification of Meningiomas
Grade 1: Slow growing and benign. Unlike some cancer cells that infiltrate the brain, a grade 1 meningioma remains separate, but can still expand, exerting pressure on the brain. Around 90% of meningiomas are classified as Grade I.
Grade 2: Faster growing and tend to grow into the brain tissue, making them more difficult to treat. Grade 2 meningiomas have a greater chance of recurrence after treatment. Despite being more aggressive, they are not considered to be cancerous/malignant. Around 7-8% of all meningiomas are Grade 2.
Grade 3: Most aggressive form with a higher recurrence rate.Grade 3 meningiomas can grow into the brain, as well as metastasise (spread) to other organs. These tumours will likely require more aggressive therapy. 2-3% of meningiomas are classified as Grade 3, or malignant.
Not all meningiomas will require treatment, and therefore regular observation and monitoring may be recommended. Depending upon the tumour classification, location and symptoms, surgery and/or radiation therapy may be required.
Because these tumours are mostly benign, and rarely invade the surrounding brain tissue, surgery often results in a cure. Some tumours however, may be difficult to remove completely, especially those that occur near important structures at the base of the skull. Radiation therapy may be used as a follow-up treatment, particularly for malignant tumours.