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Medulloblastomas mə-ˌdəl-ō-ˌblas-ˈtō-mə

By John J. Gregory, Jr., MD

Medulloblastomas are rapidly growing brain tumors that develop in the cerebellum (the part of the brain that helps control coordination and balance).

  • The cause of medulloblastomas is not known.

  • Children may have frequent vomiting, trouble with balance, headaches, nausea, lethargy, or double vision.

  • Diagnosis usually involves an imaging test, biopsy, and a spinal tap.

  • The prognosis depends on whether the cancer is average risk or high risk.

  • Treatment is surgery, chemotherapy, and radiation therapy.

Medulloblastomas account for about 20% of brain and spinal cord cancers in children. These tumors tend to occur in children who are 3 to 4 years old or 8 to 10 years old, but they can occur in infants and younger children and throughout adolescence.

Medulloblastomas develop in the part of the brain that controls coordination and balance (cerebellum), which is located in the back of the brain below the cerebrum. Medulloblastomas tend to spread to other parts of the brain and to the spinal cord. Occasionally, they spread to other parts of the body.

What causes medulloblastomas is unclear. They sometimes occur in people with certain hereditary disorders (such as Gorlin syndrome or Turcot syndrome).

Symptoms of Medulloblastomas

In many children, the first symptom is frequent vomiting. Children may become clumsy, walk unsteadily, or have trouble maintaining their balance. They may have headaches, nausea, lethargy, and double vision.

Diagnosis of Medulloblastomas

  • Magnetic resonance imaging (MRI)

  • Biopsy or often surgery to remove the entire tumor

  • Spinal tap

To make the diagnosis, doctors do an MRI with a contrast agent (a substance that makes the images clearer) to look for a tumor. Then they take a sample of tissue from the tumor and examine it under a microscope (biopsy). Usually, instead of removing just part of the tumor for the sample, the entire tumor is surgically removed and sent for examination.

To determine whether the tumor has spread, doctors do MRI of the spine and a spinal tap (lumbar puncture—see Figure: How a Spinal Tap Is Done). The spinal tap is done to obtain cerebrospinal fluid for examination under a microscope to look for cancer cells. After surgery is done, doctors do another MRI to see whether the tumor has been completely removed. The results of these tests help doctors determine whether the tumor is average risk or high risk.

Risk is average if

  • All or almost all of the tumor can be removed during surgery.

  • The tumor has not spread to other parts of the brain, the spinal fluid, or elsewhere in the body.

Risk is high if

  • A large amount of tumor cannot be removed during the surgery.

  • The tumor has spread to other parts of the brain, the spinal cord, or elsewhere in the body.

Prognosis

How well children do after treatment generally depends on whether they are categorized as having average-risk or high-risk disease.

For children older than 3 years, the chances of surviving cancer-free for 5 years is about 80% if the tumor is average risk and about 50 to 60% if it is high risk.

For children 3 years old and younger, outcome is harder to predict, but overall survival is poor. In about 40% of these children, the tumor has spread at the time of diagnosis. When children are younger, intellectual development is more likely to be affected. For example, they may have difficulty learning, remembering, and making decisions.

Treatment of Medulloblastomas

  • Surgery, radiation therapy, and chemotherapy

Medulloblastomas are best treated by surgically removing the tumor and using chemotherapy and radiation therapy. Some younger children may be effectively treated without radiation therapy.

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* This is the Consumer Version. *