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Gliomas are tumors that arise from glial cells in the brain or spine. They can be classified by location, cell type, or grade. There is no cure, and treatment includes radiation therapy, chemotherapy, surgery, and sometimes drugs or gene therapy. High-grade gliomas have a high mortality rate.
A glioma is a tumor that arises from yellow cells in the brain or spine. Glial cells, or neuroglia, are the support cells of nerve tissue, providing nutrition and other physical support to neurons. Gliomas occur most often in the brain. The cause of gliomas is unknown, although genetic predisposition is a factor, and exercising during adolescence can reduce a person’s risk of developing gliomas later in life.
Gliomas can be classified according to their location, cell type, or grade. When classified by location, gliomas are distinguished by whether they appear above or below the tentorium cerebellum, a membrane in the brain that separates the cerebrum above from the cerebellum below. A glioma that arises above the tentorium cerebellar is called a supratentorial glioma, while one below the tentorium cerebellar is a subtentorial glioma. The former is more common in adults and the latter in children.
When classified by cell type, gliomas are named after the type of normal cell they most closely resemble. Ependymomas are gliomas that resemble ependymal cells, neuroglial cells that line the ventricular system of the brain and spinal cord, a collection of structures containing cerebrospinal fluid. Astrocytomas are astrocyte-like gliomas, star-shaped neuroglia that perform multiple functions. Oligodendrogliomas resemble oligodendrocytes, which serve to insulate the axons of neurons. Gliomas can also be of mixed cell types, in which case they are called oligoastrocytomas.
The third possible classification system for gliomas is their grade, which can be low or high. Low-grade gliomas are well differentiated and benign; high-grade gliomas are undifferentiated, or anaplastic, and malignant. A patient with low-grade glioma has a better prognosis. Low-grade gliomas grow slowly and often don’t require treatment if there are no symptoms. High-grade gliomas, on the other hand, grow very rapidly and almost always grow back after surgical excision.
Gliomas in the brain can cause headaches, seizures, nausea, vomiting, and cranial nerve disorders, while gliomas in the spinal cord can cause weakness, pain, or numbness in the extremities. A glioma on the optic nerve can cause vision loss. Gliomas cannot spread through the bloodstream, but they can spread to other areas of the nervous system through the cerebrospinal fluid.
There is no cure for gliomas, and high-grade glioma patients have a very high mortality rate. Glioma is typically treated with a combination of radiation therapy, chemotherapy, and surgery, depending on the location and severity of the tumor. Sometimes drugs, especially angiogenic blockers such as bevacizumab, which block the growth of new blood vessels, are also part of the treatment. More experimental treatments use gene therapy to infect cancer cells with a virus.
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