Spinal meningiomas are growths that form along the protective layers surrounding the spinal cord. This article explores the factors and conditions that contribute to their development.
Understanding Spinal Meningioma
Spinal meningiomas originate from the meninges, the thin membranes that encase and shield the brain and spinal cord. These tumors arise from arachnoidal cap cells within these protective layers, not from the spinal cord tissue itself. Most spinal meningiomas are non-cancerous (benign) and grow slowly. They may remain asymptomatic for extended periods, causing symptoms only if they press on the spinal cord or nerves. While more common in the brain, about 12% of all meningiomas occur in the spine. They typically develop in the middle (thoracic) or upper (cervical) spine, rarely in the lower (lumbar) region.
Key Factors in Development
Several factors contribute to the development of spinal meningiomas, including genetic predispositions, environmental exposures, and hormonal influences.
Genetic Predisposition
Neurofibromatosis type 2 (NF2) is a recognized genetic link. This rare inherited condition significantly increases the risk of developing multiple benign tumors, including meningiomas. Individuals with NF2 have mutations in the NF2 gene on chromosome 22. This gene produces Merlin, a tumor suppressor protein that regulates cell growth. Impaired NF2 leads to uncontrolled cell multiplication and tumor formation. Approximately half of all NF2 patients develop meningiomas, which are often multiple. In children, meningiomas are almost always associated with NF2.
Radiation Exposure
Exposure to ionizing radiation is an established risk factor. This includes prior radiation therapy, especially to the head and neck, for other medical conditions. The latency period between radiation exposure and diagnosis can be substantial, averaging 23.5 to 35 years. Radiation-induced tumors are often multiple and may have higher recurrence rates than spontaneously occurring ones.
Hormonal Influences
Hormonal factors play a significant role, as spinal meningiomas are more common in women than men (2:1 to 4:1 ratio), particularly after middle age. Meningioma cells have hormone receptors, specifically for progesterone and estrogen. About 70% express progesterone receptors, while fewer than 31% express estrogen receptors. Hormonal fluctuations, such as during pregnancy or the menstrual cycle, can influence tumor growth, suggesting progesterone’s role.
Age
The likelihood of developing spinal meningiomas increases with age, making them more prevalent in older adults. Most are diagnosed in individuals between 50 and 70 years old, with peak incidence for benign forms occurring in the 60-69 age range.
When Causes Remain Unclear
Despite identified risk factors, the precise cause of many spinal meningiomas remains unknown. Many cases have no identifiable genetic or environmental trigger, indicating an idiopathic origin. Current research continues to investigate other potential contributing factors and molecular pathways. Studies are exploring genetic mutations beyond NF2, such as TRAF7, which may pre-exist in healthy meningeal tissues. These efforts aim to uncover a more complete understanding of why these tumors develop.