Causes of Meningioma

If you or a loved one has recently been diagnosed with a meningioma, it is common to have many questions regarding the diagnosis. Meningiomas are the most common primary brain tumor, accounting for over one third of all intracranial tumors diagnosed in the United States in recent years. The incidence of meningioma varies with age, race, gender, environmental exposures (e.g., ionizing radiation), and genetic disorders, among other factors. This article will attempt to address some of the most common causes of meningiomas.

As with most types of tumors, the risk of developing a meningioma increases with age. Meningiomas are exceedingly rare in children and young adults less than 20 years of age. In the third decade of life, a small proportion of cases occur.

The incidence of meningioma then rises in an almost linear fashion with age such that most meningiomas are discovered in patients 65 years and older. The accumulation of genetic changes and/or damage to our cells over time may contribute to this observation, though why exactly aging increases the risk of developing a meningioma is still being investigated.

A higher incidence of meningioma has been observed in non-Hispanic Blacks, as compared to non-Hispanic Whites, Hispanics, and Asian and Pacific Islanders.

Ionizing radiation is currently the main known environmental risk factor for the development of meningioma. This relationship is significant with higher doses of ionizing radiation (e.g., exposure to an atomic bomb), though it has also been observed with frequent low doses of ionizing radiation.

Several studies have been conducted to determine if ionizing radiation may be one of the causes of meningioma. From the 1930s to 1960, irradiation, or exposure to ionizing radiation through X-rays, was practiced in Eastern Europe to eradicate ringworm in children. In the following decades, researchers discovered a high incidence of meningiomas among adults who had received irradiation treatment as children. 

Ionizing radiation continues to be cited as one of the most common meningioma risk factors for adults today. In 2012, researchers reviewed 1,433 intracranial meningioma cases of patients between 29 and 79 years old and found that those who had frequent X-rays (one or more times a year) had elevated risks of meningioma. However, the risks were higher among the patients who started getting Panorex films at a younger age (less than 10 years old).

Similarly, radiation therapy to the head as a treatment for other types of brain tumors is also one of the known causes of meningioma. Therefore, it is crucial to continue post-treatment consultations and checks to ensure that a successful brain tumor treatment will not result in another tumor.

Old X-rays used to emit higher radiation levels than the modern machines we use today, which explains the link between ionizing radiation and meningioma. Still, remember that X-rays remain to be one of the known risk factors for meningioma.

Several studies have reported an increased risk of meningioma in first-degree relatives of patients with a meningioma diagnosis. This suggests that there are genes that may contribute to the formation of meningiomas, perhaps by influencing the immune system or the production of hormones. However, the exact ways in which genetics plays a role in meningioma development is unclear.

The most common genetic disorder associated with meningiomas is Neurofibromatosis type 2 (NF2). Abnormalities in the genes NF1, PTCH1, CREBBP, VHL, PTEN, and CDKN2A may also contribute to the formation of meningiomas. 

Possibly, but we are still not sure. Although meningiomas more commonly occur in women as compared to men, have several hormone receptors, and change in size over the course of the menstrual cycle and during pregnancy, the relationship between hormones and meningiomas is still under investigation. A clear relationship, either causative or protective, has not been clearly established.

Research efforts are underway to better elucidate the relationship between oral contraceptive use and the development of meningiomas. Some studies have found an increased risk of meningiomas with oral contraceptive use depending on several factors such as duration of usage and pre- vs post-menopausal status, while others have found a protective effect with oral contraceptive use. Oral contraceptives are a diverse group of medications with varying hormonal compositions. Thus, further research is needed that stratifies specific oral contraceptive use with meningioma risk.    

Several studies have pointed to a potential relationship between obesity and development of meningiomas. The Million Women Cohort study found an increasing risk of meningiomas with increasing body mass index (BMI). This observation ties into the potential relationship between hormones and the risk of meningioma. Increased body fat means increased aromatase activity, an enzyme that contributes to increased estrogen levels.  

It has long been suggested that the risk of developing a meningioma is increased following head trauma. This has not been consistently proven in the literature. Several smaller studies found a significant relationship between traumatic head injury and later incidence of meningioma growth but a large Danish cohort study performed in the late 20th century provided conflicting results, finding no significant relationship between traumatic head injury and later incidence of meningioma.  

Meningiomas are the most common primary brain tumor. Increased risk of meningioma has been associated with increasing age (over 65 years of age), African American race, female gender, past exposure to either high- or low-dose ionizing radiation, a positive family history, and certain genetic disorders (e.g. Neurofibromatosis type 2). The relationship between meningioma risk and hormones, oral contraceptive use, and obesity warrants further investigation.

• Meningioma incidence increases with age, with most patients presenting after 65 years of age.
• Women are twice as likely as men to develop meningiomas.
• African Americans are more likely to develop meningiomas.
• Exposure to ionizing radiation increases the risk of developing a meningioma.
• A positive family history and predisposing genetic disorders increase the risk of meningioma.
• The relationship between hormones, oral contraceptive use, and obesity with meningioma incidence warrants further investigation.

• American Association of Neurological Surgeons 
• National Cancer Institute 
• American Brain Tumor Society 
• National Brain Tumor Society