Astrocytomas
Astrocytomas are the most common kind glioma, a tumor arising from glial cells, the cells making up the brain's supportive tissue. The astrocytoma is named for the kind of glial cell (called an astrocyte). Half of all primary brain tumors are glial cell tumors, and three quarters of gliomas are astrocytomas.
Symptoms
The initial symptoms of brain tumors, such as headache and nausea, usually are the result of increased intracranial pressure caused by the bulk of the tumor or a backup of the cerebrospinal fluid that surrounds the brain and spinal cord. The glial cells are widely distributed throughout the central nervous system, so these tumors can occur in a wide variety of locations, and therefore can cause a wide variety of other symptoms. Depending on the location of the mass, gliomas may cause seizures, weakness or numbness in the limbs, impairments in language function, blurred or double vision, gradual changes in mood or personality, and memory loss.
Diagnosis
Imaging studies are the key component in the diagnosis of gliomas. Currently, magnetic resonance imaging (MRI) is the best available imaging modality. Computed tomography (CT) scans also are used. For either study, an agent that provides contrast in the image is administered intravenously so neurological surgeons can visualize the tumor against the normal brain in the background. In some cases, neurological surgeons may employ an MRI scan with frameless stereotactic guidance. For this study, a contrast MRI is performed after special markers (called fiducials) are placed on the patientÃs scalp. The fiducials are processed by a computer, which calculates the location of the tumor and creates a three-dimensional reconstruction. This image then is used at the time of surgery to help locate the tumor precisely, maximize tumor removal, and minimize injury to the surrounding brain.
Astrocytomas can be "low-grade" or slow-growing tumors; their symptoms develop over an extended period of time. Representing approximately 10 to 15 percent of all gliomas, they generally are found in young patients and have a more favorable prognosis. Unfortunately, low-grade astrocytomas also occur less frequently than their malignant, high-grade counterparts.
Treatment
Surgery for gliomas involves the resection of the tumor to decrease the pressure it exerts. For most gliomas, however, surgery will not provide a cure by itself. When a tumor is removed, it can be examined under a microscope to provide an accurate diagnosis so the next steps in treatment, which may include radiation therapy or chemotherapy, can be determined. In addition, some smaller tumors may be treated effectively with stereotactic radiosurgery, which involves the use of a highly focused beam of radiation to target the cancer cells specifically and leave the surrounding brain unaffected. The choice of treatment usually is made based on the grade of the tumor, which is a measure of the tumorÃs malignancy. Not all of the cells in a low-grade astrocytoma are the same, so half of these low-grade tumors eventually will evolve into higher-grade ones. This evolution to more malignant forms is the most common cause of death in patients with low-grade astrocytomas.
This page was last updated on 04/20/05.
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