Oligodendrogliomas are tumors that develop from a certain type of cell called oligodendroglial progenitor cells. These are the precursors to cells called oligodendrocytes, which wrap around nerve cells in the brain and spinal cord to form insulation. At Columbia University Irving Medical Center/NewYork-Presbyterian Hospital, we specialize in diagnosing and surgically treating oligodendrogliomas. Standard treatment options include careful monitoring, chemotherapy, radiotherapy, and surgical removal.
Oligodendrogliomas can develop anywhere in the cerebrum, the largest part of the brain. The cerebrum extends from the top of the head almost to the neck and occupies the majority of the space in the skull. Most often, oligodendrogliomas develop in the cerebrum’s frontal or temporal lobes. The frontal lobe, located behind the forehead, coordinates tasks like voluntary movement, speech, and reasoning. The temporal lobe is located at the sides of the brain, above the ears, and is responsible for hearing and memory, among other tasks.
On scale of one to four, the World Health Organization grades tumors according to growth speed and ability to spread to nearby tissues. Depending on this grade, oligodendrogliomas are labeled either low- or high-grade.
- Low-Grade (Grade II) tumors grow slowly and are benign, meaning they do not spread to nearby tissues. They are named oligodendrogliomas.
- High-Grade (Grade III) tumors grow quickly and are malignant, meaning they spread to nearby brain tissue and can cause further damage. They are named anaplastic oligodendrogliomas.
Most oligodendrogliomas are low-grade, slow-growing tumors, so they may be present for several years before being diagnosed. However, a low-grade tumor can progress and become high-grade if untreated.
Oligodendrogliomas are not common tumors, making up only about fourpercent of tumors that arise from brain cells, and they rarely occur in the spinal cord. They belong to a group of tumors known as gliomas and comprise about 5 to 19 percent of all gliomas. This percentage has been increasing, likely because diagnostic methods have improved.
Symptoms vary depending on the location and size of the tumor and may overlap with symptoms of other brain tumor types or conditions. Symptoms of oligodendrogliomas may include the following:
- Changes in personality or behavior
- Partial vision loss
- Language problems
The most common symptom is seizure, which nearly 80 percent of patients experience at some point during the course of the illness. Tumors in the frontal lobe may cause personality or behavior changes and hemiparesis. Temporal lobe tumors sometimes lack noticeable symptoms. However, when present, symptoms of these tumors can include seizure or language problems.
A physical examination and neurological examination can establish a patient’s history of symptoms. However, the symptoms of oligodendroglioma can be similar to other brain abnormalities. Therefore, imaging tests are essential for making a diagnosis.
Magnetic resonance imaging (MRI), computed tomography (CT) scan or both may be used to provide a diagnosis. Each test has its own advantages and offers valuable diagnostic information. MRI is often preferred because it shows images of soft tissue and blood vessels and can reveal brain tumors well. CT scan produces fast results and shows the skull, as well as blood and tumor calcifications, which are common in oligodendrogliomas.
Imaging tests can detect an oligodendroglioma, but sampling of tumor tissue is required to establish the diagnosis and grading. Either a craniotomy for resection, an open biopsy or stereotactic biopsy is performed to obtain a sample of the tumor tissue. If the tumor is located where it cannot be safely accessed via brain tumor surgery, a stereotactic biopsy may be recommended instead.
The biopsied tissue can be analyzed under a microscope to determine the tumor grade. It can also be analyzed to determine whether the 1p or 19q chromosomal deletions are present.
As is the case with most brain tumors, the cause of oligodendroglioma is unknown.
However, some oligodendrogliomas have recognizable chromosomal abnormalities that seem to play a role in the disease progression.
Scientists assign a number to each chromosome. Chromosomes 1 and 19 have been found to have some relevance in the response of oligodendrogliomas to treatment. Every chromosome is made up of two regions—a “p” arm and “q” arm. Deletion of the “p” arm on chromosome 1 (1p deletion) and/or deletion of the “q” arm on chromosome 19 (19q deletion) may indicate that the response to treatment will be better than for tumors without these characteristics. Oligodendrogliomas can also have a mutation in the gene IDH1, in which case they have a more favorable prognosis. In general, oligodendrogliomas have a better prognosis and better response to therapies than other infiltrative gliomas.
Oligodendrogliomas can develop at any age. They typically develop in young and middle-aged adults and rarely (6 percent of cases) in children or infants. They occur more often in men than women.
Treatment may vary depending on several factors, such as tumor grade and location. Our neurosurgeons know that each patient’s tumor is different and requires a customized approach.
For low-grade tumors, sometimes the best approach is to observe the tumor and pursue treatment if the tumor grows or symptoms worsen.
For high-grade tumors, the standard treatment is brain tumor surgery, in which as much of the tumor as possible is surgically removed. A neurosurgeon performs a craniotomy to access and remove the tumor. Radiation therapy, chemotherapy, or a combination of both may be recommended to eliminate any tumor that remains after surgery.
If the tumor is located in an area in the brain where a neurosurgeon cannot safely access and remove it, a stereotactic biopsy is performed to confirm the tumor grade. On the basis of the biopsy results, a neurosurgeon chooses the best course of radiation therapy and/or chemotherapy for a patient’s tumor.