What Is Meningioma?

Meningioma is a tumour that grows in the meninges, which are the membrane tissue layers that protect the brain and spinal cord. Meningiomas are the most prevalent type of primary brain tumour. Read on to learn about the subtle but serious signs and symptoms of meningioma, risk factors, prevention methods as well as how it is diagnosed, managed and treated.

Overview

According to the Brain Tumor Center, meningioma is a type of tumour that arises from the protective tissue layers (meninges) that surround the central nervous system (CNS), which is comprised of the brain and spinal cord.¹  

It is important to note that though they are commonly associated, not all tumours are cancerous. Cancer occurs when cells grow and divide more than they should at a very rapid, abnormal and uncontrollable pace.² Normally, healthy human cells stop growing and dividing once they become old and damaged or have received signals to stop proliferating. However, this process becomes dysfunctional or disrupted in cancer. 

Tumours are lumps of tissue that can be cancerous (malignant) or non-cancerous (benign).¹ A tumour is considered cancerous if it spreads from its original (primary) site to other areas in the body (secondary site) and invades nearby tissues. This process is termed metastasis. Benign tumours do not invade or spread to surrounding tissues and organs. Not all benign tumours result in cancer. 

Classification

The majority of meningiomas are classified as low-grade (Grade I) and benign because the tumour cells grow very slowly and remain in their primary site (the meninges) without spreading to other areas of the brain or body.^1,3 As such, the National Cancer Institute considers most meningiomas to be primary brain tumours.³ Although meningioma does not grow from brain tissue, it remains categorised as a brain tumour as it could affect nearby brain tissues, nerves and/or blood vessels. 

Benign meningioma is often likely to present as intracranial meningioma rather than spinal meningioma because it mainly initiates from the meningeal surface of the brain.⁴ 

Mid-grade (Grade II) atypical and high-grade (Grade III) anaplastic meningiomas are more severe but less common. In contrast to benign meningioma (Grade I), atypical meningiomas have a much faster tumour growth rate and are thus more likely to recur following surgical removal.³ Atypical meningiomas can also invade surrounding tissues including bone tissues. 

Anaplastic meningioma is malignant and has the fastest tumour growth rate.³ In fact, not only does it invade brain tissue, but it often spreads to other tissues and organs in the body, making it the most aggressive and commonly recurrent type of meningioma. Fortunately, anaplastic meningioma is rare, accounting for only 1.7% of meningiomas.⁵ 

In addition to being classified by their tumour growth rate (grade), meningiomas can also be classified depending on their location within the CNS, with the following types being the most common:

• Parasagittal meningioma: Forms between the right and left cerebral hemispheres, near the midline of the brain¹
• Olfactory groove meningioma: Forms above the nose, near the olfactory ‘’smell-sensing’’ nerves¹
• Intraventricular meningioma: Forms within the brain ventricles (cavities) that are filled with cerebrospinal fluid (CSF)¹
• Sphenoid wing meningioma: Forms behind the eyes and nose¹
• Skull base meningioma: Forms in the bottom of skull bones¹

Risk factors

Unfortunately, to date, what causes meningioma tumour cells to grow and divide abnormally remains a mystery. However, certain risk factors are believed to predispose individuals to meningiomas.

People assigned female at birth are twice as likely to develop benign meningioma than people assigned male at birth (2.3-1 female-to-male ratio).⁵ The reason behind this is not completely understood. Still, it is thought to be largely dependent on hormonal factors such as exposure to hormones via oral contraceptive pill use and/or hormonal replacement therapy. Interestingly, women who are pregnant or in the luteal phase of their menstrual cycle are especially at risk of meningioma, as it has been shown that meningiomas grow in size during these periods.⁵ Additionally, breast cancer, which is more likely to occur in women, has been shown to increase the risk of developing meningioma.⁵ Several other risk factors can increase the likelihood of developing meningioma, such as:

• Age: The risk of developing meningioma increases with age, mainly affecting those in their 60s to 80s.^3,5 Adults are more at risk of meningioma than children, with meningioma affecting 37.75 per 100,000 75-84-year-olds compared to 0.14 per 100,000 children aged 0-19 years⁵ 

• Ethnicity: Compared to Caucasians and Asian-Pacific Islanders, African Americans have been shown to have the highest risk of developing meningioma^3,5

• Radiation: People who have been exposed to radiation treatment, especially during childhood, are at higher risk⁵

• Genetics: People with genetic diseases such as neurofibromatosis II, as well as people who have a first-degree relative (parent, child or sibling) that have or have had meningioma, are at higher risk⁵ 

• Obesity: It is currently unclear how obesity increases one’s risk of developing meningioma. However, some research studies suggest excess levels of insulin (a hormone that lowers blood glucose levels) in people with obesity play a key role in meningioma tumour growth.⁵  

Signs and symptoms of meningioma

The signs and symptoms of meningioma may differ between patients as they depend on the size and location of the tumour and whether it initiated in the brain or rarely, the spine.¹ 

As benign meningiomas are typically slow-growing, the symptoms arise slowly, making them easy to miss and hard to predict. Unfortunately, by the time signs and symptoms develop, normal brain functioning is often hindered due to the meningioma compressing nearby brain tissues. 

The most common signs and symptoms include:

• Vision changes: Such as diplopia (double vision) or blurriness^3,4
• Headaches: particularly those that persist and worsen in the morning¹
• Loss of hearing³
• Loss of memory
• Loss of smell (anosmia)⁵
• Seizures¹
• Nausea or vomiting¹ 
• Personality changes¹
• Weakness in the arms or legs⁵

Diagnosis

To accurately diagnose meningiomas, a doctor will refer the suspected patient to a neurologist who will first perform a neurological examination to evaluate the functioning of a patient’s nervous system by assessing things like memory, hearing, vision, balance and coordination. The clinician will then perform several imaging tests with contrast dye including either an MRI or a CT scan.

In some cases, the patient may also undergo other diagnostic tests, including blood tests and/or brain angiograms to scan the blood vessels within the brain.⁶ Finally, to confirm a meningioma diagnosis, determine the type/grade of meningioma and rule out other types of brain tumours, a biopsy might be performed where a small sample of tissue is dissected and analysed under a microscope. 

Treatment and Management

The management and treatment for meningioma varies depending on multiple factors, primarily the tumour size, location and type, as well as the rate of tumour growth and the extent to which it has spread. The treatment plan will also take into account the patient’s age and overall health, as well as what the patient wishes to achieve from the treatment.

Low-grade meningioma (Grade I):

If the patient has low-grade asymptomatic meningioma with no symptoms or signs of visible tumours, no treatment is often required. However, the patient will likely undergo ‘’active monitoring’’ by taking periodical brain scans such as magnetic resonance imaging (MRI) scans to ascertain whether the meningioma has grown or spread elsewhere.⁶ The patient may be required to take the MRI scans every year, for the first five years and then every two years. 

Patients with benign but small visible tumours present may be offered radiation treatment, such as stereotactic radiosurgery (SRS).⁵ In this type of radiation therapy, a large machine containing several high-energy radiation (X-ray) beams is used to ‘’shoot’’ and effectively destroy any remaining meningioma tumour cells. 

Mid-grade (Grade II) and high-grade (Grade III) meningiomas

Often, patients with either atypical symptomatic meningioma or anaplastic symptomatic meningioma present with a few or all of the above symptoms and indicators of the tumours invading and spreading into nearby tissues.³ In these cases, patients are referred for neurological surgery, which is the primary treatment for both atypical and anaplastic meningioma.^1,3,4 The main aim of the surgery is to remove as much of the tumour as possible whilst keeping most of the healthy brain tissue intact. This surgical process is termed ‘’maximal safe resection’’.¹ 

If some of the tumours cannot be fully removed via surgical removal, patients with atypical or anaplastic meningioma are offered further treatments, including radiation therapy such as SRS and/or chemotherapy.³  Other treatment options include clinical trials and immunotherapy. 

In addition to meningioma treatment, patients with atypical and anaplastic meningioma might undergo MRI scans to monitor the tumour. Atypical meningioma patients are advised to have MRI scans every 6 to 12 months, then every two years, after the first five years.⁷ Anaplastic meningioma patients are advised to have MRI scans every 3 to 6 for the first two years then every 6 to 12 months.⁶ 

FAQs

Can meningioma be prevented?

Unfortunately, no, at least not to date.⁵

How common is meningioma?

According to the National Brain Tumor Society, meningioma accounts for approximately 39% of all primary brain tumours, making it the most common type of primary brain tumour worldwide.^6,7 Every year, about 371 people are diagnosed with meningioma. In England, between 2006 and 2010, 21 out of every 100 brain tumours (21%) were diagnosed as meningiomas.^3,6

When should I see a doctor?

Seek medical care from your general practitioner (GP), doctor or healthcare provider if you have persistent headaches. Seek immediate emergency care if you suddenly experience seizures, changes in memory or changes in vision.

Summary

Meningioma is a primary brain tumour that mainly grows from the meningeal surface of the brain (intracranial meningioma). It is often benign (non-cancerous), slow-growing, asymptomatic (has no signs or symptoms) and does not result in brain cancer or spread around the body (non-malignant). 

Unfortunately, to date, meningioma cannot be prevented as it is unclear what causes and triggers it. However, women, the elderly, people with neurofibromatosis II, breast cancer, obesity, and/or a history of excessive radiation treatment are more at risk of meningioma. 

Slow-growing, asymptomatic meningioma (Grade I) is often diagnosed and managed via periodical MRI scans or CT scans. On the other hand, fast-growing, symptomatic meningiomas such as atypical meningioma (Grade II) and anaplastic meningioma (Grade III) are often managed and treated via neurological surgery, radiation therapy and/or SRS.