Epidemiology

Meningioma stands out as the most common type of primary brain tumor in adults, accounting for approximately 37.6% of all primary central nervous system tumors and about 50% of all benign brain tumors.^[5] This means that when doctors find a tumor originating in the brain or spinal cord area, meningioma is the most likely diagnosis. The frequency with which these tumors occur makes understanding them particularly important for public health.

Meningiomas occur most commonly in people aged 40 to 70 years, and they are found in about 3% of people over age 60.^[3] The risk of developing a meningioma increases significantly with age, with high-grade meningiomas tending to occur in people around 60 years old.^[4] An estimated 3,360 people are living with high-grade meningiomas in the United States alone, though this number only represents the more aggressive forms of the disease.^[4]

The distribution of meningiomas shows clear patterns based on sex and tumor grade. Overall, meningiomas occur more commonly in women than in men, especially for the most common, slow-growing type called Grade 1 meningiomas.^[1] However, this pattern reverses for more aggressive tumors. Grades 2 and 3 meningiomas occur more often in males than females.^[4] Cancerous meningiomas are also more common in males overall.^[2]

High-grade meningiomas are most common in non-Hispanic white people, though the reasons for this demographic pattern are not fully understood.^[4] People who are Black may also be at increased risk for developing meningiomas.^[2] These demographic differences highlight the complex nature of tumor development and the various factors that may influence who develops these growths.

Causes

The exact cause of most meningiomas remains unknown, which can be frustrating for people seeking to understand why they developed this condition. Most meningiomas happen because of a chromosomal deletion, which is a genetic change where part of a chromosome is missing.^[2] A chromosome is a structure inside cells that carries genetic information, and when pieces are missing or altered, cells can begin to behave abnormally. These genetic mutations usually happen randomly, meaning they occur by chance rather than being caused by something a person did or did not do.^[2]

Cancer, including meningiomas, is fundamentally a genetic disease caused by changes to genes that control how cells function. These genetic changes can increase the growth and spread of abnormal cells.^[4] Even though we call it a genetic disease, this does not necessarily mean it is inherited from parents. In most cases of meningioma, the genetic changes happen sporadically, or randomly, during a person’s lifetime rather than being passed down through families.^[5]

Meningiomas arise from meningeal cells, which are the cells that make up the meninges. The meninges consist of three layers of tissue that cover and protect the brain and spinal cord: the tough outer layer called the dura mater, the web-like middle layer called the arachnoid, and the delicate inner layer called the pia mater.^[1] Most meningiomas grow from the arachnoid layer. Because they develop from the protective coverings rather than from brain tissue itself, meningiomas are not technically brain tumors, even though they grow inside the skull and can affect brain function.^[1]

Risk Factors

Several factors can increase a person’s chance of developing a meningioma, though having these risk factors does not guarantee that someone will develop the tumor. Exposure to radiation, especially during childhood, is one of the few well-established risk factors. People who underwent radiation therapy to the head are at increased risk of developing meningiomas later in life.^[4] This connection between radiation exposure and meningioma development has been observed in patients treated for other conditions with radiotherapy.^[3]

Hormonal factors play a significant role in meningioma development. Studies have shown that meningiomas express receptors for progesterone, estrogen, and androgen on their cell membranes, with progesterone receptors found in up to 72% of tumors.^[5] Because of this hormonal connection, certain groups face higher risk. People who are female and using hormone replacement therapy or birth control pills have increased risk.^[2] Additionally, people who have had or currently have breast cancer are at higher risk for meningiomas.^[2] The tumors can even exhibit changes in size during pregnancy, further demonstrating the influence of hormones on these growths.^[5]

Certain genetic conditions significantly increase the risk of developing meningiomas. People with a genetic condition called neurofibromatosis type 2 are at particularly increased risk.^[4] Other genetic conditions that raise risk include Cowden syndrome, Li-Fraumeni syndrome, multiple endocrine neoplasia type 1, schwannomatosis, Von Hippel-Lindau disease, and Gorlin syndrome.^[2] In these conditions, the genetic mutations can be inherited, meaning they are passed down from biological relatives who also have the condition.^[2]

Having a biological relative with a meningioma increases risk, suggesting that family history matters even outside of specific genetic syndromes.^[2] Age is another important factor, with people over age 65 at higher risk for developing these tumors.^[2] Other environmental factors that may increase risk include obesity and alcohol use disorder, though the connections are less clearly established than for radiation exposure.^[5]

Symptoms

Meningiomas usually grow very slowly, which means they can reach a large size before causing any noticeable problems. Many people have no symptoms at all, especially when the tumor is small.^[1] Because meningiomas typically grow slowly, they may not cause symptoms until they grow large enough to push on important structures around them, such as brain tissue, nerves, or blood vessels.^[2] The symptoms of a meningioma often begin slowly and may be hard to notice at first, sometimes making them easy to mistake for normal signs of aging, particularly in adults over 65.^[2]

The specific symptoms a person experiences depend heavily on where in the brain or spine the meningioma is located and which nearby structures it affects. Headaches are among the most common symptoms, particularly headaches that are worse in the morning.^[1] These headaches occur because the growing tumor creates pressure inside the skull or irritates sensitive tissues. Seizures, or sudden episodes of uncontrolled electrical activity in the brain, are another frequent symptom, particularly when the tumor is located over the cortex, which is the uppermost layer of the brain.^[6]

Vision changes occur in many people with meningiomas, especially when tumors grow near the eyes or optic nerves. These changes can include seeing double, experiencing blurring, or bulging of the eyes.^[2] Some people lose part of their field of vision, meaning they cannot see objects in certain areas even when looking straight ahead. When meningiomas grow near the olfactory nerve, which provides the sense of smell, people may experience loss of smell, a condition called anosmia.^[6]

Hearing problems can develop when meningiomas affect the nerves responsible for hearing. People may experience hearing loss or ringing in the ears, a condition known as tinnitus.^[1] Memory problems and confusion may occur depending on which parts of the brain are compressed by the growing tumor.^[2] Some people notice personality changes or behavioral changes, which can be subtle at first but become more pronounced as the tumor grows.^[2]

Physical symptoms often include weakness in an arm or leg, which typically affects one side of the body.^[1] People may experience muscle weakness, loss of balance, or difficulty with coordination.^[2] When meningiomas grow in certain locations, they can cause numbness or altered sensation in the face or body. Speech difficulties may develop if the tumor affects areas of the brain responsible for language and communication.^[2] Some people experience spontaneous bouts of uncontrollable laughter even when something is not funny, or develop hiccups after eating dry food and coughing when drinking liquids.^[17]

Prevention

Because the cause of most meningiomas is unknown and they typically occur randomly, there are no proven methods to prevent their development. However, avoiding unnecessary exposure to radiation, particularly to the head area during childhood, may reduce risk since radiation exposure is one of the few confirmed risk factors.^[4] When radiation therapy is medically necessary, the benefits typically outweigh the small risk of developing a meningioma years later, but this is an important consideration doctors weigh when recommending treatment plans.

For people with genetic conditions that increase meningioma risk, such as neurofibromatosis type 2, regular monitoring and screening may be recommended. While this does not prevent meningiomas from forming, it can help detect them early when they are smaller and potentially easier to treat. Genetic counseling may be valuable for families with a history of meningiomas or related genetic conditions to understand their risks and available options for monitoring.

Since hormonal factors appear to influence meningioma development, some people may wonder about hormone replacement therapy or birth control pills. However, the decision to use these medications should be made in consultation with a healthcare provider, weighing all the benefits and risks for an individual’s specific health situation. The increased risk of meningioma from these medications is generally considered small compared to their benefits for many people who use them.

Maintaining overall brain health through general wellness practices may not specifically prevent meningiomas, but it supports the body’s ability to function well. This includes managing chronic conditions, maintaining a healthy weight, limiting alcohol consumption, and seeking regular medical care. These practices contribute to overall health even though they have not been proven to specifically prevent meningioma development.

Pathophysiology

Understanding how meningiomas affect the body requires looking at where they grow and how they interact with surrounding structures. Meningiomas form along the dura mater, which is the outermost layer of tissue that covers and protects the brain and spinal cord.^[4] Because they arise from the protective coverings rather than from brain tissue itself, they tend to grow along the surface of the brain. Most meningiomas are found near the top and outer curve of the brain, though they can also form at the base of the skull.^[2]

As meningiomas grow, they usually grow inward, causing pressure on the brain, spinal cord, or eye. They can also grow outward toward the skull, sometimes causing the bone to thicken.^[7] The way a meningioma affects the body depends on three main mechanisms: compression, irritation, and in some cases, invasion. Compression occurs when the tumor becomes large enough to squash the underlying brain tissue, which is often what causes headaches.^[6] The brain is enclosed in the rigid skull, so even slow-growing tumors can eventually create problematic pressure.

Irritation happens when the nerves of the brain are disrupted by the tumor’s presence. This is particularly true when tumors are located over the cortex, the brain’s outer layer. When nerves become irritated, they can fire inappropriately, leading to seizures.^[6] The symptoms a person experiences depend directly on which part of the brain is being compressed or irritated. For example, if a meningioma grows where the optic nerve is located, it can impair vision. If it presses on spots of the brain that control hearing, it may cause hearing loss.^[18]

Blood vessel involvement represents another important aspect of how meningiomas affect the body. Some meningiomas contain tightly packed bunches of blood vessels, and tumors can disrupt normal blood flow in the brain.^[7] When meningiomas grow near major blood vessels, they can be particularly challenging because the tumor may involve critical blood vessels that supply the brain, such as branches of the carotid artery.^[3] This relationship with blood vessels is one reason why some meningiomas are more difficult to treat than others.

Meningiomas are classified into three grades based on how their cells look under a microscope and how they behave. Grade 1 meningiomas are the most common, accounting for about 85-90% of all cases. These are low-grade tumors, meaning the cells grow slowly, typically at a rate of about 1 millimeter per year.^[18] Grade 2, or atypical meningiomas, are mid-grade tumors that grow more quickly, at a rate between 3 to 6 millimeters per year, and have a higher chance of returning after treatment.^[18] Grade 3, or anaplastic meningiomas, are malignant (cancerous) and represent less than 3% of all meningiomas. These grow rapidly and are likely to return even after removal.^[18]

Most meningiomas do not spread to other parts of the body, which distinguishes them from many other types of cancer.^[18] However, higher-grade meningiomas can spread to other areas of the central nervous system through cerebrospinal fluid, the clear fluid that surrounds the brain and spinal cord.^[4] Grade 2 meningiomas can invade surrounding tissue, including nearby bone tissue, while Grade 3 meningiomas have irregular cells and are more likely to invade the brain or spread to other organs in the body.^[4] About 1 to 3% of meningiomas can transform into malignant tumors, with a 5-year survival rate of 32 to 64% for these aggressive cases.^[5]