Meningioma Diagnosis, Risks, and Grades

A meningioma is a type of slow-growing brain tumor. It is easily treated, but can occasionally become serious.

This article looks at meningiomas, their diagnosis, and risk factors. It will also help you understand when a meningioma might become serious.

What Is a Meningioma? 

Although meningiomas are often considered primary brain tumors, they are not tumors of brain tissue. Instead, they grow from the meninges, the protective tissue surrounding the brain. Specifically, meningiomas usually stem from the arachnoid mater. This is the middle of three membranes that surround the brain and spinal cord. 

The meninges follow the brain's major curves. For example, they dip towards the middle of the brain where the left and right hemispheres are separated, and also wrap around the base of the skull and the optic nerves. The symptoms and treatment of meningioma partially depend on where the tumor is located.

How Often Are Meningiomas Diagnosed?

Autopsy studies have suggested that in the United States, around 2.3% of the population may have a meningioma. They are not as commonly diagnosed in the living, however. This is because the tumors may grow slowly or sometimes hardly at all. 

Meningiomas account for around 39% of all primary brain tumors diagnosed in the United States. Around 37,000 people are diagnosed with meningioma each year. Based on these statistics, meningiomas are among the most common of all brain tumors.

When meningiomas do cause problems, they are often treated with a relatively simple surgery. In some cases, however, they can become serious or even life-threatening. This depends on the type and location of the meningioma, as well as the unique characteristics of individual people. 

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Risk Factors For Meningioma

Meningiomas are at least twice as common in females compared to males. The incidence increases with age. They are relatively rare in children but are likely the most common type of brain tumor diagnosed in adults. 

There are also genetic risk factors for meningioma. The best known is a hereditary condition called neurofibromatosis type II. This syndrome occurs because of a mutation in the NF2 gene, which normally helps suppress tumors. People who have this condition have an increased chance of developing tumors. 

Radiation exposure is the most definite risk factor for meningioma. This has been studied in patients who have received radiation treatment for different cancers of the brain. Since a lot of time can pass between the radiation treatment and the discovery of a meningioma, the risk is highest for people who received radiation as children. 

A 2017 review found that patients with radiation-induced meningiomas developed them an average of 23 years after radiation treatment. The average age these patients received the radiation treatment was around 13 years.

Studies have also shown a connection between frequent dental X-rays and later meningioma growth. The risk is much lower, however.

Other potential risk factors for meningioma have been studied with conflicting results, including obesity, hormone replacement, and head trauma. 

What Makes a Meningioma Serious?

Most meningiomas are benign. This means they are non-cancerous and unlikely to spread. Benign meningiomas may never even be detected. Some meningiomas, though, can become serious.

Meningiomas are graded according to their appearance under a microscope. The higher the grade, the more dangerous the meningioma.

• Grade 1: Grade I meningiomas are relatively benign. Grade 1 tumors may still require surgery to ensure they're not compressing important brain structures. Typically, though, they only need monitoring to ensure they aren't getting significantly larger.
• Grade 2: These meningiomas have more signs of active cell division. More caution needs to be taken with these tumors. Subtypes include chordoid, clear cell, and atypical meningiomas.
• Grade 3: These tumors have several signs of active cell division. The tumor may even be infiltrating the underlying brain or show areas of cell death. Subtypes include papillary, rhabdoid, and anaplastic meningiomas. Only 2 to 3 percent of all meningiomas are Grade 3. 

Patients with advanced meningiomas are more likely to have a recurrence of the meningioma after treatment. They also have a higher risk of death overall. The five-year survival rate for people with grade II meningioma is around 67.5%. This is compared to 55.6% for patients with grade III tumors.

How Meningiomas Are Treated

Regardless of the type of meningioma, location and size are also important considerations. These factors can help determine the need for treatment and how quickly it should be done.

Most importantly, healthcare providers consider how the tumor might be impacting the patient's daily life. For example, a meningioma that is pushing on the brain and causing symptoms like weakness or numbness may need to be treated, while one that is not growing or causing symptoms may not.

Grade I meningiomas may not require treatment. Instead, they are often monitored over time to ensure they aren't growing. For meningiomas that do need treatment, surgery is the most common option. When the tumor can't be completely removed surgically, radiation therapy may be used. Radiation is also sometimes used for tumors in inoperable locations.

Summary

Meningioma is a common type of brain tumor. These tumors tend to be slow-growing and often don't require treatment, though they should be monitored.

Females are more likely than males to develop meningiomas. The risk also increases with age. People who have had past radiation treatment to the brain are also at higher risk.

Meningiomas become serious when they are growing or infiltrating other parts of the brain. When this happens, they can be treated with surgery or radiation therapy. Aggressive meningiomas are uncommon.