Meningioma Risk Factors

Ionizing radiation is the radiation used in medicine that creates ions by knocking electrons out of atoms. Ions penetrate and interfere with living tissue, causing tumor cells to die as they attempt to reproduce. Exposure to ionizing radiation has been found to be associated with a higher incidence of intracranial tumors and particularly meningiomas. Data from atomic bomb survivors exposed to high doses show a greatly increased risk for meningioma. There is also evidence indicating an association with meningioma from lower dose levels. A well-known example of ionizing radiation and meningioma comes from children in Israel who were given radiation for scale ringworm between 1948 and 1960. These children were observed to have a relative risk for meningioma of almost 10. The dose given to these children was approximately the amount used in dental radiographs prior to 1948. Within the Unites States, this is the most common form of exposure to ionizing radiation. A number of studies have linked the number of full mouth dental radiographs to risk of meningioma.

Radiation therapy for intracranial tumors has also been linked to meningioma risk, and animal studies support the notion that ionizing radiation can induce intracranial tumors, including meningiomas, by damaging DNA. No recent large-scale studies of meningioma risk relative to ionizing radiation have been conducted since the time that new radiographic procedures for delivering radiation have been developed. These methods use focus beams to help limit unnecessary exposure to areas outside of the target. A population-based study with a large sample size will help to provide a better estimate of the current association. Patients who have undergone broad radiation treatments in the past should take care to watch for symptoms (see Symptoms section) and monitor themselves for meningiomas. Evidence for meningiomas caused by radiation exposure may be multiple and are generally more aggressive.

An association between meningiomas and hormones has been suggested by a number of findings, including: the increased incidence of these tumors in women versus men; the presence of hormone receptors such as estrogen, progesterone, and androgen on some meningiomas; an association between breast cancer and meningiomas; and indications that meningiomas increase in size during the menstrual cycle and pregnancy. Researchers have also just begun to address the question of whether exogenous hormones (such as the use of oral contraceptives or hormone-replacement therapy) are associated with a risk of meningioma.

A number of other predisposing factors have been associated with meningiomas; however, the relationships are not well understood or have not yet been substantiated. These conditions include:

• Genetics: Recent population-based surveys suggest that meningiomas may arise from highly penetrant, but relatively rare inherited genes. These genes are primarily observed in families with neurofibromatosis 2 (Nf2). In sporadic meningioma, Nf2 is deleted or mutated in up to 50% of cases. However, evidence shows that only a small proportion of meningioma cases are likely to be attributable to this rare inherited genetic condition. It may be of greater interest to examine the evidence of more common, less penetrant genes on meningioma as well as the effect of these variants with environmental factors. New methods in genetics and molecular epidemiology allow for the high-throughput processing of thousands of genes in large patient populations with relative ease and at low cost.
• Previous Trauma: Meningiomas have been found at the site of previous traumas such as head injuries, but the relationship is not fully understood.
• Cell Phone Use: The question of cell phone use and the exposure to electromagnetic fields remains of interest to the public as potential cause of meningiomas and other brain tumors. At present, little evidence exists for an association between meningioma and cell phone use, although studies have included small sample sizes for meningioma and the follow-up time since the advent of cell phone use has been relatively short.
• Viruses: There is a possibility that viruses may be related to meningioma formation but that relationship is not defined. For more information on the causes of intracranial meningioma, please consult a paper published by Dr. Elizabeth Claus et al of Yale University and the Brigham and Women’s Hospital published by the Congress of Neurological Surgeons (PDF, 504KB).