A glioma is a tumor arising from the gial cells in the brain or spine. Glial cells, or neuroglia are the support cells of the nervous tissue, providing nutrition and other physical support to the neurons. Gliomas occur most often in the brain. The cause of gliomas is unknown, though genetic predisposition is a factor, and exercise during adolescence may decrease a person's risk of developing gliomas later in life.
Gliomas may 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 cerebelli, a membrane of the brain separating the cerebrum above from the cerebellum below. A glioma arising above the tentorium cerebelli is called a supratentorial glioma, while one below the tentorium cerebelli is an infratentorial glioma. The former is more common in adults and the latter in children.
When classified by their cell type, gliomas are named after the type of normal cell they most resemble. Ependymomas are gliomas resembling ependymal cells, neuroglial cells that line the ventricular system of the brain and spinal cord, a set of structures containing cerebrospinal fluid. Astrocytomas are gliomas resembling astrocytes, star-shaped neuroglia that perform multiple functions. Oligodendrogliomas resemble oligodendrocytes, which serve to insulate the axons of neurons. Gliomas may also be of mixed cell types, in which case they are called oligoastrocytomas.
The third possible system of classification for gliomas is their grade, which may be either 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 do not require treatment if there are no symptoms. High-grade gliomas, on the other hand, grow very quickly, and nearly always grow back after surgical excision.
Gliomas in the brain can cause headaches, seizure, nausea, vomiting, and cranial nerve disorders, while spinal cord gliomas can cause weakness, pain, or numbness in the extremities. A glioma on the optic nerve can cause loss of vision. 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 patients with high-grade glioma have a very high mortality rate. Glioma is typically treated with a combination of radiation therapy, chemotherapy, and surgery, depending upon the location and severity of the tumor. Medication, specifically angiogenic blockers such as bevacizumab, which block the growth of new blood vessels, are sometimes part of the treatment as well. More experimental treatments use gene therapy to infect cancer cells with a virus.