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Medulloblastoma

  • What is Medulloblastoma?

    Medulloblastoma/PNET is the most common brain tumour of childhood, representing 20% of all childhood brain tumours. They are most common in children between the ages of three and eight, and are slightly more common in boys than girls.

    The majority of these tumours arise in what is referred to as the posterior fossa region of the brain. This area includes the area at the lower back of the head. Often Medulloblastomas are referred to as a PNET (Primitive Neuroectodermal tumour). These can arise in the posterior fossa, but are also common in other regions of the brain, including the pineal gland and cerebrum. Medulloblastomas/PNETS have the potential to spread (metastasise) to the spinal column via the cerebrospinal fluid, the fluid surrounding the brain and spine. Like other childhood brain tumours, they rarely spread outside the central nervous system (brain and spinal cord) to other organs of the body.

    Signs & Symptoms

    Common symptoms include:

    • Vomiting (most common), with/out nausea. Commonly occurs in the morning after wakening
    • Headaches
    • Clumsiness
    • Difficulty with tasks like handwriting
    • Gradual decline in school performance (impaired attention)

    If there is tumour spread to the spinal cord, the signs and symptoms may include:

    Back pain

    • Difficulty walking
    • Problems with bowel and bladder control

    Diagnosis

    The diagnosis of a Medulloblastoma/PNET is made by the Neurosurgeon taking a biopsy of the tumour. This is taken when the Neurosurgeon makes attempts to remove the entire tumour. The exact location of the tumour is determined by an MRI (Magnetic Resonance Imaging) of the whole brain and spinal cord which is performed before surgery. Spinal imaging is necessary to rule out spread of the disease to the spinal cord. Other tests and investigations that help assist with staging of the disease include a lumbar puncture (or spinal tap). This detects the presence of tumour cells in the cerebro-spinal fluid (Refer to section on tests and investigations).

    Treatment

    Treatment for childhood Medulloblastoma/PNET, begins with surgery, where all atempts are made at acheiving a complete surgical reception of the tuomour, with minimal harm to the surrounding healthy brain tissue. Surgery alone none-curative, as it is nessessary to kill the microscopic tumour cells that reamain after surgery, that are not visable on the post-operative MRI scan. Treatment following surgery usually consist of radio therapy with chemotherapy.

    Children greater than four years of age who have had a complete tumour resection, receive a combination of cranio-spinal (brain and spine) radiation, followed by a four month course of intensive chemotherapy. Because of the significant effects of radiotherapy on an infant's developing brain, children less than three years of age receive high dose chemotherapy immediately following surgery, with the aim to delay or even obliterate the need for radiation treatment.

    If the Neurosurgeon has been unable to completely remove the tumour and/or there is evidence of tumour spread to the spinal cord and/or other areas of the central nervous system, the child is considered high-risk. Treatment is similar for children who have had a complete surgical excision, however high-risk patients receive an additional chemotherapy agent, together with higher doses of radiation to the brain and spine.

    Reduced doses of radiation to the entire brain and spine, has been a major treatment advance in the treatment of Medulloblastoma/PNET over the last couple of years. It is aimed at decreasing the long-term side effects that often result from high doses of radiation delivered to the brain and spine. The use of peripheral blood stem cell transplants has contributed to this advance, enabling the intensity of chemotherapy to be increased, whilst reducing the dose of radiation that is required to the brain and spine.

    This progress has impacted the overall survival rate of this disease. Survival rates for children who had a complete removal of their tumour initial surgery, have risen to 80% survival at 5 years from diagnosis, compared to 50% and 60% survival rates five years ago. The treatment of infants continues to be difficult. This is because of the delay in the ability to deliver radiation to the entire brain and spine, resulting from the known detrimental effects it has on the developing brain.

    Follow Up Care

    After treatment has finished, children visit clinic on a regular basis, and undergo MRI scans and other investigations throughout their childhood to detect any possible recurrence. Importantly, all children attend the Neuro-Oncology Long-Term Effects clinic, where they are regularly reviewed a by a group of specialists involved in monitoring the specific long term growth and development needs of these patients.