Most brain tumors develop from the actual brain substance. Meningiomas, on the other hand, develop from the cells of the meninges. The meninges consist of three layers. In a meningioma, the arachnoid membrane, the middle layer, is affected. The cells of this meningeal layer then grow uncontrollably.
Why the growth of these cells gets out of control has not yet been fully explained.
However, researchers have identified risk factors that promote the development of a meningioma. These include
- Radiotherapy to treat a previous cancer,
- dental X-ray diagnostics (depending on the X-ray procedure used and the time at which the diagnostics were carried out),
- the hereditary disease neurofibromatosis type two. People affected by this disease are significantly more likely to develop a meningioma. Often, several meningiomas develop, whereas people without this hereditary disease only develop one tumor.
Meningiomas form in the arachnoid membrane, the middle layer of the meninges © olgadanilina | AdobeStock
Meningiomas grow very slowly, so that the first symptoms often only appear years after the onset of the tumor disease. It is only when the tumor mass displaces neighboring brain regions or nerve structures that symptoms occur. However, these are extremely non-specific and can also occur with other diseases.
If the tumor is located near the motor center, patients suffer from paralysis of the arms and legs.
Meningiomas located in the olfactory groove of the brain, on the other hand, result in a restriction or loss of the sense of smell. However, as olfactory disorders tend to develop gradually, they often go unnoticed.
A meningioma can also irritate the three meninges and trigger a seizure. Patients lose control of their body for a short period of time and suffer from convulsions and seizures. They may also lose consciousness.
The tumor increases the pressure inside the skull. Increased intracranial pressure manifests itself in various symptoms. These include
If the meningioma occurs on the meninges in the area of the spinal cord, a so-called local compression syndrome occurs. Patients complain of sensory disturbances and pain in the corresponding area. A considerable mass in the spinal canal leads to myelopathy. Depending on the localization, this manifests itself as
- Gait disturbances,
- sensory disturbances and
- disturbances when going to the toilet.
In some cases, the meningioma grows so slowly that the brain can adapt to the structural changes. These asymptomatic brain tumors are discovered by chance during a computer or magnetic resonance imaging scan.
Various imaging techniques can be used to diagnose meningiomas. The most commonly used procedure is magnetic resonance imaging (MRI). This allows the different soft tissue qualities to be easily recognized and the examination does not involve radiation exposure.
This examination method is also almost exclusively suitable for examining the spinal canal.
A more detailed classification of the space-occupying process in the brain is possible using
- magnetic resonance spectroscopy (MRS),
- diffusion-weighted MRI and
- blood flow measurement of the brain with computer tomography.
Despite the indications provided by these imaging techniques, only the examination of tissue samples can confirm the diagnosis. This is particularly important when a brain tumor occurs for the first time. For this purpose, tissue is removed from the tumor during an operation and then examined in the laboratory.
Not every meningioma requires treatment. A small tumor that does not cause any symptoms can initially be observed. To do this, patients must see a radiologist at regular intervals. The radiologist uses CT or MRI to check whether the tumor is growing or remains unchanged.
However, if the tumor causes symptoms, neurosurgical removal is advisable. If the tumour is particularly rich in blood vessels, embolization is necessary before surgery. This involves closing off the blood vessels to reduce the risk of major blood loss during the surgical procedure.
If the meningioma cannot be completely removed, radiotherapy is then carried out. This involves the use of high-dose ionizing radiation. It is intended to damage the genetic material of the tumor and thus prevent it from growing.
Another treatment option is the gamma knife: this radiosurgical radiotherapy device concentrates radiation in a single point and destroys the focus of the disease.
The prognosis of a brain tumor depends primarily on the severity of the disease.
A grade I meningioma can usually be completely removed in an operation and therefore has a good prognosis.
Around ten percent of all meningiomas are grade II. They can grow faster than grade I meningiomas and often grow back after a successful operation.
Grade III meningiomas are classified as malignant. In contrast to grade I and II tumors, it can also metastasize to other organs. The chances of recovery are low here and the prognosis is correspondingly poor.
Overall, the 5-year survival rate for meningioma is more than 90 percent. This means that 90 percent of patients are still alive five years after diagnosis.
