Definition and Overview

Medulloblastoma is the most common type of childhood brain cancer. It starts in or near the cerebellum, the part of the brain that regulates motor movements and controls coordination, balance, and other complex functions.

Medulloblastoma is one type of primitive neuroectodermal tumours (PNETs), a group of malignant, highly invasive growths with a high tendency to spread (metastasise) throughout the central nervous system (CNS) through the cerebrospinal fluid (CSF). Other PNETs are pineoblastoma, atypical teratoid/rhabdoid tumor (ATRT), and supratentorial PNET.

With aggressive treatment (a combination of surgery and radiotherapy or chemotherapy), the majority of patients with localised medulloblastoma can be cured. However, despite successful treatment, many brain cancer survivors suffer from significant endocrinological and intellectual impairment. Reported long-term complications include problems with learning, hearing, growth, and fertility. They also have an increased risk of developing secondary cancers later in life.

Medulloblastoma accounts for up to 20% of all childhood brain tumours. Although commonly found in children between the ages of three and eight, it can also occur in older individuals. It is more common in boys than girls.

Causes of Condition

Just like other types of cancer, the exact cause of medulloblastoma remains unknown. However, in general, cancer begins when healthy cells in the body change, grow out of control, and form an abnormal mass.

Although the exact cause of the condition is unknown, scientists have identified factors that can increase one’s risk of developing this type of tumour. These include rare genetic syndromes, such as nevoid basal cell carcinoma syndrome or Gorlin syndrome. Boys and children below eight years old also have an increased risk.

Key Symptoms

Some patients with medulloblastoma do not present any symptoms. However, when the tumour starts to grow and put pressure on the brain, the following signs usually develop:

  • Chronic headaches

  • Problems with coordination and balance

  • Abnormal eye movements

  • Vision problems

  • Problems with handwriting

  • Dizziness

  • Changes in personality and behaviour

  • Nausea and vomiting

  • Back pain and problems with bladder control and walking, if the tumour has spread to the spinal cord

  • Fatigue

Who to See and Types of Treatments Available

Children with medulloblastoma are treated by a multidisciplinary team of doctors composed of a paediatrician, neurosurgeon, and medical and radiation oncologists, among others.

The condition is diagnosed with the following tests:

  • Physical exam and review of the patient’s medical history

  • Imaging studies - Patients undergo magnetic resonance imaging (MRI) and computed tomography (CT) scan; two imaging tests that create pictures of the brain and surrounding structures. These tests can show abnormal growths and provide crucial information needed for cancer staging.

  • Spinal tap or lumbar puncture - For this procedure, the doctor inserts a needle into the lower part of the spine to collect a small amount of CSF. The test looks for tumour markers.

  • Biopsy - To determine if the tumour is malignant, the doctor will obtain a small amount of tissue from the brain or remove the entire tumour through traditional open surgery. The obtained tissue/tumour is then analysed under a microscope by a pathologist.

The results of these tests can confirm if the tumour is malignant and if it is standard (localised) or high-risk (has spread to other parts of the brain and spinal cord).

Treatment of medulloblastoma focuses on the complete surgical removal of the tumour, if possible. The procedure, called craniotomy, involves removing a part of the skull to access and subsequently remove the tumour. Surgery is often followed by several months of chemotherapy in young patients (three years and younger) or radiotherapy in older patients.

Chemotherapy is a standard cancer treatment that uses drugs to destroy tumour cells. In some cases, it is the main and only treatment method used if the tumour is inoperable or inaccessible. Chemotherapy drugs can be delivered intravenously or taken orally.

Radiation therapy, on the other hand, uses high-energy x-rays to destroy malignant cells. The most common type of this procedure is called external-beam radiation therapy in which the radiation is given from a machine outside the body.

In cases of recurrent medulloblastoma, bone marrow or stem cell transplantation may be recommended.

The prognosis for children with medulloblastoma is relatively good. The five-year survival rate for those with localised tumour is up to 80%. This number goes down to 65% for those with high-risk medulloblastoma.

Following successful treatment, patients are advised to follow-up with their physician on a regular basis. During such visits, the patient may undergo blood or imaging tests to check for any signs of recurrence. Patients also often require treatment to manage the side effects of cancer treatment and complications of their conditions, including:

  • Heart and lung problems

  • Emotional and cognitive problems

  • Depression

  • Learning difficulties

References:

  • Massimino M, Cefalo G, Riva D, Biassoni V, Spreafico F, Pecori E, et al. Long-term results of combined preradiation chemotherapy and age-tailored radiotherapy doses for childhood medulloblastoma. J Neurooncol. 2012 Feb 16

  • Deorah S, Lynch CF, Sibenaller ZA, Ryken TC. Trends in brain cancer incidence and survival in the United States: Surveillance, Epidemiology, and End Results Program, 1973 to 2001. Neurosurg Focus. 2006 Apr 15. 20(4):E1

  • Min C, Paganetti H, Winey BA, Adams J, MacDonald SM, Tarbell NJ, et al. Evaluation of permanent alopecia in pediatric medulloblastoma patients treated with proton radiation. Radiat Oncol. 2014 Nov 18. 9(1):220.

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