Most meningiomas do not actually invade brain tissue, but impact the Central Nervous System (CNS) by:
- compressing brain tissue, nerves originating from or entering into the brain or spinal column (cranial and spinal nerves) and other associated structures;
- causing reactive swelling in brain tissue surrounding the tumor;
- blocking the flow of the cerebrospinal fluid (CSF) in the brain and spinal cord resulting in its accumulation, a condition called obstructive hydrocephalus, which in turn compresses brain tissue and associated structures;
- blocking the flow of blood in various veins and arteries in the head by compressing these structures or invading them.
The types of symptoms that patients with meningiomas experience include seizures, headaches, muscle weakness, confusion, changes in personality, visual disorders and hearing loss. Seizures are the most common symptom associated with cranial meningiomas, appearing in 30 to 40% of patients pre-treatment.
Examples of tumor effects associated with specific locations are presented in the following table.
|Falx and parasagittal
||Symptoms can vary depending upon the location of these tumors along the falx, a groove that runs between the brain’s two hemispheres in a front to back direction. For example, those located in the frontal section may impair higher levels of brain functioning such as reasoning and memory, while those located in the middle section would be more likely to cause leg weakness.
||Seizures, headaches and neurological deficits related to the specific location of the tumor on the surface of the brain.
|Sphenoid wing (also called sphenoid ridge)
||Problems with vision, loss of sensation in the face, or facial numbness, and seizures.
||Loss of smell due to compression of the nerves that run between the brain and the nose, and if the tumor grows big enough, visual symptoms can be expressed due to compression of the optic nerve.
||Problems with vision due to compression of the optic nerve.
||Facial symptoms or loss of hearing due to compression of cranial nerves.
||May block the flow of cerebrospinal fluid causing pressure to build up (obstructive hydrocephalus), which can produce headaches, wooziness, and changes in mental function.
||Buildup of pressure in the eyes, giving a bulging appearance and potential loss of vision.
||Back pain, or pain in the limbs, from compression of the nerves where they run into the spinal cord.
It can be difficult to diagnose a meningioma for numerous reasons. Given that the majority of meningiomas are slow-growing and most often occur in people between the ages of 40 and 70, symptoms may be so subtle that the patient and/or doctor may attribute them as the normal signs of aging (for example, visual changes, loss of memory, menopausal effects, and unsteady gait). Also, the variety of symptoms associated with meningiomas can lead to confusion regarding the cause, since many of the effects can also be due to other medical conditions. Misdiagnosis is not uncommon and it can take some patients years to be correctly diagnosed.
Fortunately, once imaging of the patient’s brain or spinal cord is performed, diagnosis of a meningioma is relatively straightforward. The two most widely used imaging techniques are CT (also called CAT) and MRI scans. CT and CAT stand for computerized tomography or computed axial tomography, respectively, and this technique involves the use of X-rays to image the patient. MRI stands for magnetic resonance imaging and uses a magnet to scan the brain. Often a substance (also called a contrast agent) is injected into the patient’s vein to enhance the imaging so that a clearer distinction can be made between tumor and non-tumor tissue. MRI is the preferred imaging technique in the case of brain or spinal tumors, as it can give a more precise picture of a tumor’s location and the area of the meninges from which it arose.