The exact cause of glioma is not clear, although some hereditary disorders are known to increase the likelihood of these tumors developing. Examples of these disorders include tuberous sclerosis and neurofibromatosis.
Gliomas are classified according to the specific type of cells involved, as follows:
- Ependymoma - This tumor arises from the ependymal cells. which are found in the brain ventricles and spinal cord.
- Astrocytoma - This tumor involves the astrocytes, cells that transport nutrients, as well as providing structural support to neurons.
- Oligodendroglioma - Here, cells called oligodendrocytes are involved. These cells provide insulation in the form of myelin.
- Mixed gliomas - These are tumors that contain a combination of cell types such as an oligoastrocytoma, for example.
Gliomas are also classified according to their grade. Low-grade gliomas are usually slow growing, non-malignant and are associated with a better outcome over high-grade gliomas, which are malignant and more aggressive.
Although no specific cause of glioma has been identified, research suggests that the following factors play a role:
- Several acquired gene mutations are associated with the condition. For example, the tumor suppressor p53, sometimes called the “guardian of the genome” has been found to be mutated early on in the course of glioma. This gene usually ensures that DNA is correctly copied during DNA replication, destroying the cell if any damaged DNA cannot be fixed. Mutation of p53 means other mutations go on to survive and cause disease.
- The use of mobile phones has been said to increase the risk of glioma by exposing the brain to electromagentic radiation. However, several studies have been unable to find any significant association between glioma and mobiles.
- Ionising radiation can increase the risk for astrocytomas and oligodendrogliomas.
- Increasing age is another risk factor associated with glioma.
- Males are at a slightly greater risk of this condition than females.
- Genetic conditions known to increase the risk for glioma include neurofibromatosis (type 1 and type 2), Li-Fraumeni syndrome, tuberous sclerosis and Turcot syndrome.