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Medulloblastoma is a primitive neuro-ectodermal tumor (PNET) and is the most common malignant brain tumor in childhood. A medulloblastoma is caused by a fault in the development in one of the precursor cells of the nervous system. Every year, approximately 20 children in the Netherlands are diagnosed with a medulloblastoma. The children are 5 to 6 years old on average when the tumor is detected, but this type of brain tumor also occurs in younger and older children.

A medulloblastoma is always in the cerebellum. The tumor sometimes spreads to other parts of the central nervous system. Metastases in the lymph nodes and bones are rare. The chance of curing children with a medulloblastoma depends very much on any metastases. Medulloblastomas that have not metastasized generally have a chance of approximately 75 percent of healing.

Symptoms of this disease

The complaints are ambiguous initially and, above all, present in varying degrees. Many children feel uncomfortable, nauseated or suffer from headaches for some time. This is due to increased pressure in the head. The tumor grows from the cerebellum, which means there is less space and the cerebrospinal fluid cannot flow away. If the pressure increases further, your child may experience vomiting in the morning, without being nauseous. Balance problems are also common: your child may trip more often or walk differently. The latter is sometimes difficult to discover in very young children, because they are still practicing walking. Very occasionally they may experience numbness and the nerve function in the legs or other parts of the body may fail. In most cases this is a result of metastases in the spinal cord. Finally, there are also children who, as a result of increased pressure in their heads, suddenly start to look cross-eyed, have poorer vision and experience swallowing or speech difficulties.

How do we make the diagnosis? 

In case there is suspicion of a brain tumor, an MRI scan will always have to be performed, followed by an MRI of the spinal cord if the presence of a brain tumor is confirmed. This is necessary in order to map out the possible expansion within the central nervous system. Neurosurgical surgery will always follow in order to obtain tumor tissue for diagnosis. The aim of this operation is also to remove as much tumor tissue as possible. A biopsy is only performed in exceptional cases. The pathologist will diagnose the tumor tissue. For some of these children, cerebrospinal fluid is also taken by means of a spinal puncture to check for the presence of tumor cells. This additional liquor diagnosis always takes place after the tumor has been removed.

In case there is suspicion of a brain tumor, a CT scan or an MRI scan will usually be performed quickly. For some of these children, cerebrospinal fluid is sometimes also taken by means of a spinal puncture to check for the presence of tumor cells. 

Treatment of a medulloblastoma

The treatment of a medulloblastoma almost always starts with surgery. After the operation, the pathologist examines the tissue under the microscope. Based on the results and the data from other tests, the stage is determined and the follow-up to the treatment is determined.

This is usually followed by radiotherapy and chemotherapy. Sometimes chemotherapy starts as early as during radiotherapy. In children younger than three years of age, due to the expected long-term consequences, radiotherapy is not performed, is postponed for as long as possible or is limited to a small part of the brain.