Meningiomas are the most frequently diagnosed primary tumor of the central nervous system, originating from the protective layers surrounding the brain and spinal cord. Spinal meningiomas are a much rarer subset, accounting for only a small fraction of all meningioma cases. While the exact cause remains unknown, research has identified several strong statistical associations and underlying biological mechanisms that contribute to their formation.
Understanding Spinal Meningioma
A meningioma is a growth that develops from the meninges, the three layers of tissue that encase the central nervous system. Specifically, these tumors arise from the arachnoidal cap cells, which are part of the middle layer, the arachnoid mater. Spinal meningiomas are typically found within the dura mater—the outermost layer—but outside the spinal cord itself, a location known as intradural extramedullary.
These tumors are classified as World Health Organization (WHO) Grade I, meaning they are slow-growing and non-cancerous in most cases. They are most commonly located in the thoracic region of the spine, which is the middle and upper back. As they grow, spinal meningiomas cause symptoms by compressing the spinal cord or the surrounding nerve roots, leading to issues like pain, numbness, or motor dysfunction.
Established Risk Factors
The most apparent risk factors for spinal meningioma are demographic, based on age and biological sex. These tumors are highly specific to older adults, with the peak incidence for sporadic (non-inherited) spinal meningiomas typically occurring in individuals in their sixties. This suggests that the development of the tumor is a process that accumulates over many years.
A striking feature of spinal meningiomas is the strong female predilection, which is even more pronounced than in their cranial counterparts. Sporadic spinal cases show a female-to-male ratio that can range from 3:1 up to 9:1. This significant imbalance points to the probable involvement of female sex hormones in the tumor’s development or growth.
Research shows that meningioma cells frequently express receptors for progesterone and, less often, estrogen. This presence of hormone receptors is believed to be the reason why tumor growth may be associated with periods of elevated hormone levels, such as during pregnancy or with the use of hormone replacement therapy. The hormonal environment appears to provide a stimulus that encourages the proliferation of the affected meningeal cells.
Prior exposure to ionizing radiation, particularly therapeutic radiation directed at the head or neck, is another established and definitive risk factor. Although the overall risk remains low for the general population, this exposure can induce genetic damage that predisposes cells to tumor formation decades later. Radiation-induced tumors may also occur at a younger age and sometimes exhibit more aggressive characteristics compared to spontaneous cases.
The Role of Genetic Predisposition
While most spinal meningiomas occur without a clear hereditary cause, a specific inherited disorder is linked to their development. Neurofibromatosis Type 2 (NF2) is a rare genetic condition that significantly increases the risk of developing multiple tumors of the nervous system, including meningiomas. This condition is caused by a mutation in the NF2 gene located on chromosome 22, which produces a tumor-suppressor protein called Merlin.
The malfunction of the Merlin protein disrupts the normal mechanisms that control cell growth and division, leading to uncontrolled proliferation of meningeal cells. Patients with NF2 often develop meningiomas at a much younger age, sometimes in their thirties, and are prone to having multiple tumors in both the brain and spine. The presence of multiple, pathologically distinct spinal tumors is highly suggestive of an underlying NF2 diagnosis.
In sporadic cases—those that are not inherited—genetic changes still play a fundamental role. The loss of the tumor-suppressor function from chromosome 22, the same region where the NF2 gene is found, is a common finding in many meningiomas. This random, non-inherited genetic alteration suggests that a breakdown in the cell’s ability to regulate its own growth is a central biological event in the formation of these tumors.
Debunking Common Misconceptions
When searching for the cause of any tumor, people often look to environmental factors and personal habits, but many commonly suspected links are not supported by scientific evidence for spinal meningiomas. For instance, there is no current research that establishes a causal relationship between specific lifestyle choices, such as diet, smoking, or exercise habits, and the development of these tumors. While obesity has been studied as a possible risk factor for cranial meningiomas, the link is not well-defined for the spinal location.
A historical misconception suggested that prior head or spinal trauma could lead to meningioma formation. Current research has investigated this possibility and has found no credible evidence to support that head or back injuries are a causative factor. Similarly, concerns regarding exposure to common environmental toxins or the use of mobile phones have not been substantiated by rigorous scientific studies as a cause for spinal meningioma.