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Learn About Medulloblastoma©
Written by Cancer Center Staff

Source: Cancer Resource Room

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What is Medulloblastoma?
Medulloblastoma is a brain cancer that occurs in children and young adults. Like all cancers, it is caused by abnormal cells that grow and divide without control. The growing cells form a tumor or lump in the brain that keeps getting bigger. Medulloblastoma can spread to nearby parts of the brain and spinal cord, but not usually to other parts of the body.

Brain tumors like medulloblastoma take up space inside the skull. Because the skull is hard bone and cannot expand, the tumor presses on normal parts of the brain causing problems in brain function. Pressure on the brain causes symptoms such as headache, loss of balance, nausea, vomiting, and sleepiness. The symptoms are often worst in the morning.

In addition to pressure directly on the brain, medulloblastoma grows in a space that gets blocked off as the tumor gets larger. The brain and spinal cord are surrounded by fluid called cerebrospinal fluid (it is easier to call it, “CSF”). This fluid needs to flow all around the spinal cord and brain. The growth of a tumor like medulloblastoma can block the flow of CSF causing a back-up, like a dam in a river. When the CSF gets backed up, that causes pressure on the brain, too. Giving the patient a steroid medication can sometimes decrease fluid pressure. Other patients need the fluid drained away from the brain with something called a shunt. It consists of a long, thin tube that drains fluid away from the brain. Draining this fluid helps relieve the symptoms caused by pressure on the brain.

Inside of Brain. Massachusetts General Hospital Cancer Center, Boston, MAMedulloblastoma is most common in young children. The typical age at the time of diagnosis is around 7-8 years old, but it can occur in younger children as well as in adults. The tumor appears most often in the part of the brain where the cerebellum, fourth ventricle and brain stem meet.

Medulloblastoma starts in this area but easily invades nearby tissue or spreads (metastasizes) to other parts of the brain and spinal cord. As many as 30% of patients have disease spread at the time the tumor is first diagnosed. But less than 5% of patients have tumor spread anywhere else in the body. If it spreads outside the brain and spinal cord, it usually goes to the bones.

How is medulloblastoma diagnosed?
The diagnosis of medulloblastoma begins with a history and physical exam. The medical history is the story of the patient’s health and present symptoms. The details of each symptom are explored. For example, if the symptom is headache, the questions will include how long the headaches have been happening, when during the day they occur, how long they last, what other symptoms happen along with the headaches, does anything relieve the headaches, what medications have been tried, and so on.

What are the symptoms of medulloblastoma?
Of the many symptoms that may be caused by medulloblastoma, the most common are:

  • headache
  • nausea and vomiting
  • sleepiness
  • changes in vision (blurred or double vision)
  • loss of coordination
  • slurred speech
  • poor balance
  • dizziness
  • confusion

Many questions about a patient’s general health are asked. After the patient’s health history, a thorough physical exam is done. The most important part is a test of all the brain and spinal cord functions called a “neurological” exam. This helps to match up the history with the physical findings.

When the history and physical exam are complete, some other tests may be done. Some blood tests are done just to check the patient’s general state of health. Other tests are specially for diagnosing a brain tumor. The most useful are a CT scan and MRI of the brain. These imaging tests can show the location and size of the tumor. It also shows what effect the tumor has on other parts of the brain. The location of a tumor in the fourth ventricle and cerebellum and its particular appearance of the tumor on the MRI image makes a diagnosis of medulloblastoma likely.

Another imaging test for brain tumors is called a PET scan. Although this test is not used for the diagnosis of medulloblastoma, it may be in the future. PET stands for Positron Emission Tomography. These scans require an injection of glucose (a sugar molecule) that has been made mildly radioactive. The brain uses the glucose for energy. Some parts of the brain use more glucose than others. The PET scanner picks up the amounts of radioactivity coming from different parts of the brain as the glucose is used up. When a tumor is present, it shows on the PET scan because the tumor cells use an abnormal amount of the radioactive glucose.

Other tests are done for finding if there is spread of tumor to the spine. One is a spine MRI, sometimes done at the same time as the brain MRI. Children may be given sedative medication or anesthesia for the MRI because it is necessary to lie very still in the MRI scanner. They need an IV for anesthesia and for something called the contrast dye. Contrast dye makes the MRI more capable of showing areas of abnormal cells. Another test called a spinal tap is done 10 – 14 days after surgery. A spinal tap removes a small amount of CSF (cerebrospinal fluid) so it can be tested for tumor cells. It is done by putting a long, thin needle in the space between the spinal bones and the spinal cord. This is the space the CSF flows through. A spinal tap is uncomfortable so children are sedated by an anesthesiologist for these procedures. In older patients all that is needed is some novacaine in the skin where the needle starts.

The diagnosis of medulloblastoma can be made with some certainty from the history, physical exam, and the CT and/or MRI. But confirming the diagnosis only happens after the tumor is removed and a pathologist looks at the tumor tissue under a microscope.

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