Meningioma

The brain and spinal cord are surrounded by three protective membranes called meninges. Tumors that arise from the cobweb skin (arachnoid membrane) of the meninges are called meningiomas. Meningiomas are the most common benign intracranial tumors. 

Depending on its location, a meningioma causes different symptoms.

Meningiomas usually grow very slowly, but in rare cases can infiltrate surrounding tissue and metastasize. Although meningiomas are usually benign, they sometimes go undetected for a long period of time due to their insidious, displacing growth, which can lead to severe damage and disability.

Ionizing radiation is currently considered the most significant known risk factor for the development of meningiomas. People who have been exposed to high doses of radiation have a significantly increased risk of developing a meningioma over the course of their lives. This includes, for example, survivors of the atomic bombings, who have been reported to have a 6- to 10-fold increased risk, as well as patients who have undergone radiation therapy to the head and neck.

People with the inherited condition neurofibromatosis type 2 also have an increased risk of developing meningiomas.

According to the World Health Organization (WHO), meningiomas are classified into three grades based on histopathological criteria:

• WHO Grade I: approx. 70–80%
• WHO Grade II: approx. 15–25%
• WHO Grade III: approx. 1–3%

WHO Grade I meningiomas are the most common type and are generally benign. They usually grow slowly and have a relatively low recurrence rate after complete removal.

WHO Grade II meningiomas often grow more rapidly, can invade surrounding tissue, and carry an increased risk of recurrence.

WHO Grade III meningiomas are rare and malignant (anaplastic). They grow aggressively, recur more frequently, and usually require a combination of surgery and radiation therapy.

Meningiomas usually grow slowly. As they grow, they can compress the surrounding brain tissue or nearby nerves and blood vessels, thereby causing symptoms. The symptoms that occur depend primarily on the tumor’s location, size, and rate of growth.

Since meningiomas usually grow slowly, symptoms often develop gradually and increase over time. It is not uncommon for meningiomas to cause no symptoms for a long time and to be discovered incidentally during imaging (incidental finding).

Common symptoms:

• headaches
• epileptic seizures
• vision, smell, or speech disorders
• paralysis or sensory disturbances

Many meningiomas are discovered incidentally, for example during imaging for nonspecific headaches or following an accident. Such findings are referred to as incidental findings. The diagnosis is often made using magnetic resonance imaging (MRI) or computed tomography (CT).

If the meningioma is small, causes no symptoms, and is not located near functionally important areas of the brain, regular follow-up is often recommended initially. This is usually done through repeated MRI scans, often at yearly intervals at first.

Certain characteristics may indicate an increased potential for growth. These include, among others, a tumor size of more than 2.5 cm, accompanying cerebral edema, or specific signal changes on T2-weighted MRI. In such cases –  or if the tumor is located in an unfavorable position – even an incidentally discovered meningioma may require treatment.

Small meningiomas that do not increase in size can be treated in a conservative manner. If meningiomas grow continuously or have reached a size that compresses the brain, causes cerebral edema, or becomes symptomatic, they should be treated. Standard therapy is surgery, less common is radiosurgical therapy. 

Because of the variable location and size, the decision about the best approach must always be discussed on an individual basis. The optimal treatment therefore depends on the size, location and growth rate of the tumor, as well as on histopathological tissue analysis and the patient's general condition.

Patients with asymptomatic incidental findings, small meningiomas or older age are initially treated conservatively. This means that clinical controls including imaging are performed regularly to monitor the progression of the disease. Initial follow-up is performed within 3‒6 months after the first diagnosis. If the findings are stable, the subsequent time intervals between follow-up examinations can be progressively extended.

In various studies, stable meningioma size without growth tendency was observed in about 50‒70% of patients during imaging follow-up over an average period of 2‒5 years. If the meningiomas increase in size or new symptoms develop, a new decision on further therapy should be made.

In these cases, if an important brain area is affected, the operation must be performed under functional monitoring. For this purpose, the latest technical procedure such as neuronavigation with augmented reality and intraoperative neuromonitoring, are used. They enable the neurosurgeon to work with maximum precision and safety under the operating microscope and to make the patient transparent, i.e. to look into tissue.

Meningiomas are often highly vascularized. To minimize bleeding during surgery, it is important to occlude the blood vessels supplying the tumor as early as possible.

In some cases—for example, with certain meningiomas at the base of the skull—these supplying blood vessels are difficult to access during surgery or can only be reached at a later stage. In such cases, a procedure known as endovascular embolization can be performed prior to the actual surgery. During this procedure, the blood vessels supplying the tumor are selectively occluded as part of a minimally invasive vascular procedure. This reduces blood flow to the tumor, which can make the surgery safer in selected cases and minimize bleeding.

In patients with meningioma that is inoperable or only partially operable, radiation therapy is a treatment option with good tumor size control. Radiation therapy is also used as an adjuvant for higher-grade meningiomas or incomplete resection. However, the meningiomas must not have exceeded a certain size for this.

In difficult cases with gradual disease progression despite surgery and radiation, radionuclide therapy offers another therapeutic option. This involves targeting the tumors with radioactive drugs. The radiopharmaceutical, the radioactive substance, binds to special receptors on the surface of the meningioma, the somatostatin receptors, and achieves a local radiation effect there, thus destroying the tumor cells.

The risk of complications during surgical removal of a meningioma—and, if necessary, during additional radiation therapy—depends on various factors. These include, above all, the size, location, and accessibility of the tumor, as well as the patient’s age and overall health.

For meningiomas in uncomplicated locations, the risk of serious complications is generally low, at less than 2%. For tumors in complex locations or larger tumors, the risk may be higher.

The risks in each individual case depend heavily on the specific situation. We would be happy to discuss these with you personally based on your magnetic resonance imaging (MRI) and explain your personal risk profile.

The prognosis for a meningioma depends on several factors. The most important factors are the tumor’s location and size, as well as its histological characteristics, i.e., the WHO grade (I–III). Another important factor is whether the tumor could be completely or only partially removed during surgery. The results of the histological examination and—in some cases—molecular biomarkers also play a role in planning further treatment. Based on these findings, the next steps are determined on an individual basis.