Oligodendroglioma Health Article

Definition

Oligodendrogliomas are a rare form of brain tumors. The brain is made up of many supporting cells that are called glial cells. Any tumor of these glial cells is called a glioma. Oligodendrogliomas are tumors that arise from a type of glial cell called oligodendrocytes. These cells are the specialized cells of the brain that produce the fatty covering of nerve cells (myelin).

Description

Oligodendrogliomas can grow in different parts of the brain, but they are most commonly found in the frontal or temporal lobes of the cerebrum. The frontal lobes are responsible for cognitive thought processes (knowing, thinking, learning, and judging). The temporal lobes are responsible for coordination, speech, hearing, memory, and awareness of time.

There are two types of oligodendroglioma: the well-differentiated tumor, which grows relatively slowly and in a defined shape; and, the anaplastic oligodendroglioma, which grows much more rapidly and does not have a well-defined shape. Anaplastic oligodendrogliomas are much less common than well-differentiated oligodendrogliomas.

More common than either form of pure oligodendroglioma is the mixed glioma, or oligoastrocytoma. These mixed gliomas are a mixture of oligodendroglioma and astrocytoma. An astrocytoma is a tumor that arises from the astrocytes, specialized cells in the brain that regulate the chemical environment of the brain and help to form the blood-brain barrier.

Oligodendrogliomas and mixed gliomas account for approximately 4 to 5% of all primary brain tumors and 10% of all gliomas. A primary brain tumor is a tumor that begins in the brain, as opposed to a secondary (or metastatic) brain tumor, which originates in another organ and spreads (metastasizes) to the brain.

Demographics

Oligodendromas occur in approximately nine in every one million people. Oligodendrogliomas can occur in people of any age, but most occur in middle-aged adults.

Oligodendrogliomas occur with equal frequency in members of all races and ethnic groups. There does not appear to be any relation of oligodendrogliomas to any geographic region. For unknown reasons, men are affected by oligodendrogliomas in higher numbers than women.

Causes and symptoms

The cause, or causes, of oligodendrogliomas are not known; however, most people with these types of tumors have some type of genetic mutation on chromosome 1, chromosome 19, or on both chromosomes 1 and 19. In early 2001, investigations were ongoing in an attempt to determine if these genetic factors, or other factors, cause oligodendrogliomas. Oligodendrogliomas are not contagious.

The symptoms of oligodenrogliomas are the result of increased pressure in the fluid within the skull (intracranial hypertension). These symptoms include:

• nausea
• vomiting
• irritability
• headache
• vision disturbances
• enlargement of the head
• seizures

Oligodendrogliomas may also be accompanied by a weakness or paralysis on the side of the body opposite to the side of the brain where the tumor is located. When the tumor is located in a frontal lobe, the patient may experience gradual changes in mood and personality. When it is located in a temporal lobe, the patient may experience difficulty with speech, hearing, coordination, and memory.

Diagnosis

The diagnosis of oligodendrogliomas begins in the doctor's office with a basic neurological examination. This examination involves:

• testing eye reflexes, eye movement, and pupil reactions
• testing hearing with a tuning fork or ticking watch
• reflex tests with a rubber hammer
• balance and coordination tests
• pin-prick and cotton ball tests for sense of touch
• sense of smell tests with various odors
• facial muscle tests (e.g., smiling, frowning, etc.)
• tongue movement and gag reflex tests
• head movement tests
• mental status tests (e.g., asking what year it is, who the President is, etc.)
• abstract thinking tests (e.g., asking for the meaning of a common saying, such as "every cloud has a silver lining.")
• memory tests (e.g., asking to have a list of objects repeated, asking for details of what a patient ate for dinner last night, etc.)

If the doctor suspects a brain tumor may be present, further diagnostic tests will be ordered. These tests are performed by a neurological specialist. Imaging tests that may be ordered include computed tomography (CT) and magnetic resonance imaging (MRI).Other tests may include a spinal tap, to examine the cerebrospinal fluid, and an electroencephalogram (EEG), which measures the electrical activity of the brain.

Treatment team

Treatment of any primary brain tumor, including oligodendrogliomas, is different from treating tumors in other parts of the body. Brain surgery requires much more precision than most other surgeries. Also, many medicinal drugs cannot cross the blood-brain barrier. Therefore, the therapies that are used to treat oligodendrogliomas, and the side effects of these therapies, are quite complex.

The most up-to-date treatment opportunities are available from experienced, multi-disciplinary medical professional teams made up of doctors, nurses, and technologists who specialize in cancer (oncology), neurology, medical imaging, drug or radiation therapy, and anesthesiology.