This information is about a specific type of brain tumour that mainly affects children, called a medulloblastoma. It is written as if the person with a medulloblastoma is a child. If you are an adult with medulloblastoma most of the information will still be relevant to you. It should ideally be read with our general information about brain tumours.

Cells within the brain normally grow in an orderly and controlled way, but if for some reason this order is disrupted the cells continue to divide and form a lump or tumour.

A tumour may be either benign or malignant. Although a benign tumour can continue to grow, the cells do not spread from the original site. In a malignant tumour, the cells can invade and destroy surrounding tissue and may spread to other parts of the brain.

Tumours affecting the central nervous system (CNS), which is made up of the brain and spinal cord, are fairly rare. About 4500 new tumours are diagnosed each year in the UK. Many of these are malignant.

Most brain tumours are named after the type of cells from which they develop. Medulloblastomas are malignant tumours formed from poorly developed cells at a very early stage of their life. They develop in the cerebellum (see diagram below), in a part of the brain called the posterior fossa, but may spread to other parts of the brain.

Very rarely, medulloblastomas may spread to other parts of the body. If they do spread to other parts of the brain, or to the spinal cord, this is usually through the cerebrospinal fluid (CSF). CSF is the fluid that surrounds and protects the brain and the spinal cord.

Medulloblastomas are more common in children, particularly between the ages of three and eight. They make up about one in five (20%) of all childhood brain tumours. The tumour is more common in boys than girls. They can also occur in adults, but this is extremely rare.

As with most brain tumours, the cause of medulloblastoma is unknown. Researchers are continuing to work at finding possible causes.

The first symptoms of any brain tumour are usually due to increased pressure within the skull (raised intracranial pressure). This may be caused by a blockage in the ventricles (fluid-filled spaces in the brain), which leads to a build-up of CSF, or by swelling around the tumour itself.

Raised intracranial pressure can cause headaches, sickness (vomiting) and sight problems. Vomiting is common first thing in the morning. Children often appear tired, weak and irritable. Changes in personality and behaviour may also be noticed.

As the cerebellum is the part of the brain that controls muscle coordination, a tumour in this area may cause problems with walking. A person may appear to stumble, or walk in an awkward or uncoordinated way. Speech can also be affected, and words may be slurred or muddled.

Other specific symptoms associated with medulloblastoma are nystagmus (jerky eye movements), stiffness in the neck, and muscle weakness. The symptoms that people have will depend on the size and position of the tumour.

So that your child's doctors can plan treatment, they need to find out as much as possible about the type, position and size of the tumour, so your child may have a number of tests and investigations.

Neurological examination (nerve tests) This will assess any effect of the tumour on the nervous system.

CT (computerised tomography) scan A CT scan takes a series of x-rays which build up a three-dimensional picture of the inside of the body. The scan is painless and takes from 10–30 minutes. CT scans use a small amount of radiation, which will be very unlikely to harm your child and will not harm anyone they come into contact with. Your child will be asked not to eat or drink for at least four hours before the scan. A CT scan may be used to identify exactly where the tumour is or to check for any spread of the cancer.

Most people who have a CT scan are given a drink or injection to allow particular areas to be seen more clearly. This may make your child feel hot all over. Before having the injection or drink, it is important to tell the person doing this test if your child is allergic to iodine or has asthma.

MRI (magnetic resonance imaging) scan This test is similar to a CT scan, but uses magnetism instead of x-rays to build up a detailed picture of areas of your child's body. During the scan, your child will be asked to lie very still on a couch inside a long tube for about 30 minutes. It is painless but can be uncomfortable, and some people feel a bit claustrophobic during the scan. It is also noisy, but your child will be given earplugs or headphones.

Some people are given an injection of dye into a vein in the arm, but this usually does not cause any discomfort.

Biopsy To give an exact diagnosis, a sample of cells from the tumour is usually taken, then looked at under a microscope. The biopsy involves an operation. The doctor will discuss with you whether this is necessary and exactly what the operation involves.

Lumbar puncture Sometimes it is necessary to carry out a test known as a lumbar puncture. The skin on your child's back is numbed with local anaesthetic, and a needle is passed through the skin and into their spine so that a small amount of spinal fluid (CSF) can be withdrawn for tests. The CSF can then be examined to see if there are any tumour cells present. MRI scans can also show this.

The treatment for medulloblastoma depends on a number of factors, including your child's general health and the size and position of the tumour. The results of the tests will enable the doctor to decide on the best type of treatment.

Your child's treatment will usually be planned by a team of specialists known as a multidisciplinary team (MDT). The team will usually include a doctor who operates on the brain (neurosurgeon), a doctor who specialises in treating illnesses of the brain (neurologist), a doctor who specialises in treating cancer (an oncologist), a specialist nurse and possibly other health professionals, such as a physiotherapist or a dietitian.

There are some risks associated with treatment to the brain and the doctor will discuss these with you.

Consent

Before any treatment, the doctor will give you full information about what the treatment involves and explain the aims of the treatment to you. They will usually ask you to sign a form saying that you give your permission (consent) for the hospital staff to give the treatment to your child. No medical treatment can be given without your consent.

Benefits and disadvantages of treatment

Treatment can be given for different reasons and the potential benefits will vary for each child. If treatment has been offered that aims to cure the cancer, deciding whether your child has the treatment may not be difficult. However, if a cure is not possible and the treatment is to control the cancer for a period of time, it may be more difficult to decide whether to go ahead.

If you feel that you can't make a decision about the treatment when it is first explained to you, you can always ask for more time to decide.

The treatment is often given at an important time in a child's development. There may be some long-term effects of treatment for medulloblastoma, including growth and hormonal changes, behavioural changes and possible learning difficulties. Before treatment, the doctor will discuss the possible long-term effects with you.

Surgery

Medulloblastoma may block the ventricles of the brain and cause a build-up of CSF, which raises the pressure within the skull. At the beginning of the operation this pressure has to be reduced and a tube (shunt) may need to be inserted to drain off the excess fluid. Alternatively, a minor operation may be done to allow fluid to drain away. This operation is known as a third ventriculectomy. In either case a small flat plastic bubble (ommaya reservoir) may be inserted under the scalp. The device can be used to give chemotherapy treatment into the fluid around the spinal cord.

The aim of surgery is to remove as much of the tumour as possible, without damaging the surrounding brain tissue. As it is rarely possible to remove the tumour completely, surgery will be followed up with radiotherapy and/or chemotherapy.

Following surgery for medulloblastoma, a CT scan or MRI scan may be done to find out how much of the tumour is left.

Radiotherapy

Radiotherapy treatment is the use of high-energy rays to destroy the cancer cells and is commonly used after surgery to destroy any remaining malignant cells. As medulloblastoma may spread through the CSF to the spinal cord, radiotherapy is given to the brain and spinal cord.

Whenever possible, radiotherapy is not given to children under the age of three because of the risk of long-term side effects. Instead, a course of chemotherapy is given and, if necessary, radiotherapy is given when the child is older.

Chemotherapy

Chemotherapy is the use of anti-cancer (cytotoxic) drugs that destroy cancer cells. It may be given alone, or together with surgery and radiotherapy, to treat medulloblastoma. Chemotherapy may be given to young children instead of radiotherapy.

You may find the idea of a tumour affecting the brain extremely frightening. As a parent, the fact that your child has cancer is one of the worst situations you can be faced with. You may experience many different emotions, including anxiety and fear. These are all normal reactions, and are part of the process many people go through in trying to come to terms with their condition.

Many people find it helpful to talk things over with their doctor or nurse, or one of our support service nurses. Close friends and family members can also offer support.

Driving

In some circumstances, adults with a medulloblastoma may not be allowed to drive for a period of time.

After surgery to the main part of the brain, the cerebrum, there is a small risk of epileptic fits. The Drivers and Vehicle Licensing Association (DVLA) requires that you do not drive for at least a year after this type of surgery.

You may not be allowed to drive some vehicles, such as a LGV (large goods vehicle) or a PCV (passenger carrying vehicle). You may not be able to drive them for at least five years after treatment, and will only be able to after this time if your cancer has not come back.

The hospital will not contact the DVLA, but it is your responsibility to do so and your doctor will advise you how to do this.

Children treated for a medulloblastoma will normally be allowed to drive like anyone else from the age of 17, and can hold a full licence until 70, unless there are ongoing medical problems associated with their tumour or treatment, such as epilepsy.

This section has been compiled using information from a number of reliable sources, including:

• Oxford Textbook of Oncology (2nd edition). Souhami et al. Oxford University Press, 2002.
• The Textbook of Uncommon Cancers (3rd edition). Raghavan et al. Wiley, 2006.
• Cancer in the Nervous System (2nd edition). Levin. Oxford University Press, 2002.

For further references, please see the general bibliography.