Oligodendroglioma

What is Oligodendroglioma?

Oligodendroglioma is a type of glioma, a tumor that grows from glial cells which make up the brain’s supportive tissue. Oligodendrogliomas grow from oligodendrocytes, glial cells that form a protective covering for nerves in the brain. Oligodendrogliomas most often develop in the cerebrum, and about half occur in the frontal lobe.

Most oligodendrogliomas occur in adults, and they are slightly more common in men. They are very rare in children and teens, accounting for less than 1% of brain tumors in children under 14 years of age.

Oligodendrogliomas can be well differentiated (grade II) or anaplastic (grade III). Treatment usually includes surgery to remove as much of the tumor as possible. Radiation therapy with or without chemotherapy is often used to kill remaining cancer cells. Survival rates for children with oligodendroglioma depend on the tumor grade. Patients with low-grade tumors that are completely removed by surgery have a survival rate greater than 90%.

Signs and Symptoms of Oligodendroglioma

Oligodendrogliomas are often slow growing. The tumor may be present for years before it causes problems. Symptoms of oligodendroglioma depend on several factors including:

• Child’s age and stage of development
• Size of the tumor
• Location of the tumor in the brain
• How fast the tumor grows

Oligodendroglioma symptoms may include:

• Seizures (most common)
• Changes in personality or behavior
• Headaches
• Problems in vision
• Weakness or numbness on one side of the body

About half of patients experience seizures prior to diagnosis. Most patients (about 80%) will have seizures associated with the tumor at some point during the course of their illness.

Diagnosis of Oligodendroglioma

Doctors test for oligodendroglioma in several ways. 

• A health history and physical exam helps doctors learn about symptoms, general health, past illness, and risk factors. 
  • The cause of oligodendroglioma is unknown, but certain genetic changes in cells are associated with these tumors.
    
• A neurological exam measures different aspects of brain function including memory, vision, hearing, muscle strength, balance, coordination, and reflexes.
• An electroencephalogram (EEG), measures electrical activity of the brain. This test monitors and records seizure activity through scalp electrodes.
• Imaging tests are used to help identify the tumor, see how big the tumor is, and find out what brain areas may be affected. Oligodendrogliomas often contain areas of calcium deposits (calcification) within the tumor. These calcium deposits can be seen on certain imaging tests and can help make the diagnosis.
  • Magnetic resonance imaging (MRI) is the main imaging technique that is usually used to evaluate oligodendroglioma. MRI uses radio waves and magnets to make detailed pictures of the body. The images made by MRI can give more information about the type of tumor and the potential spread of disease. An MRI is also done after surgery to see if any tumor remains.
  • Computed tomography (CT Scan) uses X-rays to create cross-sectional images of the organs and tissues inside the body. The machine takes many pictures to make a very detailed image. The images are taken as a series of “slices” of the body and are saved to a computer. These slices or sections can allow very small tumors to be seen.
• A biopsy is usually used to diagnose oligodendroglioma. In a biopsy, a small sample of the tumor is removed during surgery. A pathologist looks at the tissue sample under a microscope to identify the specific grade of tumor. The tissue is also examined for molecular features and genetic markers that give more information about the tumor.

Staging and Grading of Oligodendroglioma

Oligodendroglioma tumors are grouped by how they look under the microscope. The more abnormal the cells look, the higher the grade. Oligondrogliomas are usually grade II or III.

• Grade II oligodendroglioma is considered low grade. The cells look more like normal cells and grow more slowly. They are less likely to spread to other parts of the brain.
• Grade III oligodendroglioma is considered high grade. These tumors are called anaplastic oligodendrogliomas. They are more aggressive and can spread more easily.

Prognosis for Oligodendroglioma

The long-term survival rate for low grade oligodendroglioma is more than 90% when the tumor is completely removed with surgery. If the tumor can’t be completely removed, the survival rate is about 80-85%.

Factors that influence chance of cure include:

• Tumor grade
• Whether the cancer is localized or has spread to other areas of the brain
• If surgery can completely remove the tumor
• If there are certain genetic changes in the tumor cells
• If the cancer is new or if it has come back (recurrent)

Treatment of Oligodendroglioma

Treatment of oligodendroglioma depends on the type of tumor and its location. Doctors also consider the age of the patient. Radiation therapy is not used in very young children because of the potential side effects.

Follow-up care

After treatment for oligodendroglioma, patients will have regular MRI scans to monitor for recurrence. Follow-up should include appropriate rehabilitation and neurological consultation. Steroid and anti-seizure medications may be needed for a period of time.

More: Life After Brain Tumors