Which methods are used to treat a meningioma, and at what stage?

A meningioma is a benign tumor that originates in the meninges.

It usually grows slowly and displaces the surrounding brain tissue, reaching a considerable size before causing symptoms. Depending on its location and how fast it grows, headaches, seizures, personality changes, or even cranial nerve deficits may occur.

A meningioma can develop anywhere in the head and is often named after the location of its growth. Examples include falx meningioma, tentorium meningioma and olfactory meningioma.

In most cases, surgery to remove the tumor—if possible, including the point of attachment—is the treatment of choice. In this case, the meningioma can often be easily separated from the surrounding tissue and removed. This can be difficult in the case of tumors found at the base of the skull that have grown into bone structures or the sinuses. In special cases or in situations involving residual or recurrent tumors, radiation therapy may also be indicated. Depending on the size, location, and biology of the tumor, radiosurgery may be performed, which is a single-stage treatment option especially suitable for smaller tumors. Alternatively, fractionated radiation therapy may be performed. In this case, the dose is divided into several treatments, which is intended to reduce side effects as much as possible.

If the tumors are discovered incidentally and are therefore asymptomatic and small, a wait-and-see approach may be agreed upon. The affected patient should then undergo regular MRI scans to detect any growth at an early stage.

Most patients develop the disease between the ages of 50 and 70, with women twice as likely to be affected as men.

How does a meningioma develop in the head?

Various risk factors are known to contribute to the development of a meningioma in the head. Ionizing radiation is known to be the most important risk factor for the development of these tumors, which are mostly benign. A meningioma occurs significantly more frequently in children who have undergone radiation therapy for a tumor in the head and neck region, as well as in atomic bomb survivors, who have a 6 to 10 times higher risk. There are also genetic defects associated with an increased incidence of tumors.

Patients with neurofibromatosis type 2 (mutation of the NF2 gene) have a significantly higher risk of developing multiple meningiomas. There is also evidence of hormone-related regulatory mechanisms. This supports the higher frequency of the disease in women, its expression of hormone receptors, and its observed acceleration of growth during pregnancy.

In principle, these tumors can be classified based on cell structure as meningothelial, fibrous, or secretory. According to the WHO classification, they are further classified into Grades 1–3 based on their proliferation index, i.e., how quickly a cell divides or how fast the tumor grows. The risk of recurrence increases with a higher grade, so high-grade tumors are irradiated postoperatively to prevent recurrence. These are referred to as atypical (Grade 2) or anaplastic (Grade 3) meningiomas. Anaplastic variants account for only a small proportion (3%) of all meningiomas, while atypical Grade 2 tumors account for 20% according to a new classification. The largest proportion are Grade 1 tumors with a low proliferation index. Regardless of the grade, all variants originate in the meninges, or more specifically, in the cells of the arachnoid membrane.

What symptoms can a meningioma cause?

The symptoms caused by a brain tumor depend largely on its location and size. Since meningiomas are benign tumors that grow relatively slowly, and that steadily displace brain tissue, they can reach a considerable size before the patient experiences symptoms. Clinically, patients with large frontal tumors show signs of depression with motivational disorders and personality changes. This implies that when depression is newly diagnosed, cranial imaging should be used to rule out an organic cause. In rare cases, dementia can also be caused by a brain tumor. Headaches and seizures are symptoms that can often occur in this context.

If the tumor is located in clinically relevant areas, symptoms will occur even if the tumor is small. In the cavernous sinus area, where the oculomotor nerves pass through, visual disturbances and double vision occur early on due to ocular muscle paralysis, which causes significant impairments for the patient. In other areas of the skull base, a meningioma can irritate cranial nerves, such as the sphenoid nerve or the olfactory nerve in the case of an olfactory meningioma. Meningiomas can also develop in the posterior cranial fossa. This may become noticeable due to brain stem compression or cranial nerve deficits, which can result in hearing loss, dizziness, facial paralysis, and swallowing disorders. If new symptoms or deficits occur, patients should promptly see a doctor and undergo cranial imaging.

What size does the meningioma have to be for a surgeon to operate on it?

The question of what size meningioma requires surgery is one that’s often asked—but tumor size isn’t the only factor to consider. Location, symptoms, and the patient’s general condition also play a decisive role.

Referrals to neurosurgery are often elective, either for consultation after intracranial imaging or as an emergency measure if new symptoms such as neurological deficits or seizures occur.

The standard procedure is to discuss the case at an interdisciplinary tumor board meeting, which is held regularly at the hospital. This board is comprised of neurosurgeons, neurologists, pathologists, radiologists, radiation therapists, and oncologists. These physicians advise on the best individual treatment for patients with cancer and whether surgical removal, radiation therapy, chemotherapy, or a combination of these therapeutic methods is indicated. In principle, surgery is the treatment of choice for symptomatic meningiomas. Incidental, asymptomatic tumors found by chance, may also be monitored under certain circumstances. Radiation therapy is an option for patients who are not eligible for surgery because their health is so severely impaired that anesthesia lasting several hours would pose too high a risk.

If the meningioma is located on the convexity or in a parasagittal region, complete resection is often possible. The goal is to remove the entire tumor along with its attachment to the meninges. Lateral sphenoid wing meningiomas can also usually be operated on successfully using a frontotemporal approach.

In contrast, medial sphenoid wing meningiomas often cannot be completely removed because both the intracranial vessels and the cranial nerves are involved.

The principle of surgical treatment is represented by 4 Ds: intracapsular debulking, devascularization, dissection, and detachment. Prior to this, a craniotomy (an opening of the skull) must be performed for every brain tumor resection. The evoDrill from evonos can be used to create a drill hole, allowing precise holes of various sizes to be drilled into the bone without exerting force. At the same time, the dura and the underlying brain are protected by the auto-stop mechanism. A piece of bone is then sawn out using a cranial perforator. In the case of superficial tumors especially, the craniotomy must extend beyond the tumor to identify its boundaries with the brain. If necessary, the affected dura must also be removed. After resection of the brain tumor tissue with the evoCarat diamond knife from evonos, the bone flap is usually repositioned and refixed using small plates. The evoFix cranial fixation system from evonos is ideal for this, offering the surgeon plates in various shapes and sizes.

How do meningiomas affect life expectancy?

Life expectancy is not necessarily reduced in the case of a benign brain tumor such as a meningioma. In particular, if a tumor can be completely removed by a doctor without complications, there is no impact on life expectancy.

However, there are also higher-grade meningiomas that grow more aggressively. Although they do not develop metastases, they can infiltrate brain tissue and grow again after resection. This is referred to as a recurrence. Whether such a recurrence occurs depends not only on the tumor biology but also on the extent of the resection.

The extent of resection is graded according to the Simpson grading scale. Grade I describes complete tumor removal, including the affected dura and bone, while Grade V describes only tumor decompression.

Life expectancy is influenced by possible complications that can occur during surgery. If large vessels such as the carotid artery or middle cerebral artery have grown into the tumor, they can be damaged even during careful preparation and may need to be closed to stop bleeding. This results in reduced blood flow to the brain tissue, which then dies. This is referred to as an infarction, in which the patient not only loses the function of the affected area. The brain can also swell severely, which is life-threatening due to the rigid skullcap. If the intracranial pressure cannot be reduced, the patient will die.

However, iatrogenic damage to the cranial nerves, resulting in swallowing or vision problems, also limits the quality of life and life expectancy of affected patients. These limitations can also arise from unrestricted tumor growth, meaning that detailed information must be provided before treatment begins.

Overall, this leads to a 5-year survival rate of 91.3% for all patients with meningiomas.