What Is Medulloblastoma?
Medulloblastoma is a brain tumor located in the cerebellum, the part of the brain that controls balance, coordination, and other complex motor functions. Medulloblastomas grow most often in the central part of the cerebellum and less frequently in the outer parts of the cerebellum. Medulloblastoma is the most common type of malignant brain tumor in children.
- Medulloblastoma accounts for 15 to 20 percent of all pediatric brain tumors.
- Medulloblastomas occur most commonly in children between the ages of three and eight but can be seen in children and adults of any age.
- There are about 350 cases of medulloblastoma diagnosed each year in the United States.
- The outcome for children with medulloblastoma has improved dramatically over the past several decades. Doctors historically have classified medulloblastoma as either standard or high risk based on biopsy results. In recent years, however, studies by researchers at Dana-Farber/Boston Children’s and other institutions have shown that what we call medulloblastoma could actually be several different diseases. In fact, medulloblastoma can be divided into four molecular subtypes based on specific types of gene mutations within the tumor.
Children with medulloblastoma are treated at Dana-Farber/Boston Children's through our Medulloblastoma Program, part of our comprehensive Childhood Brain Tumor Center. Our pediatric brain tumor specialists provide a unique degree of specialization across many disciplines, which translates into advanced treatment options for children with medulloblastoma. We offer:
- Technological advances such as the intra-operative MRI, which allows our pediatric neurosurgeons to obtain an MRI immediately in the operating room before the operation is complete and remove as much of the tumor as possible.
- Expert diagnosis and consultation by neuropathologists who use advanced molecular diagnostic testing.
- Access to unique clinical trials from our own investigators, the Children’s Oncology Group, and the Pediatric Oncology Experimental Therapeutics Consortium.
Because brain tumors in children, including medulloblastoma, behave differently than those in adults, it's important for families to seek a pediatric center with specific expertise in treating childhood brain tumors.
Causes and Symptoms of Childhood Medulloblastoma
In most cases, the cause of medulloblastoma is not known. In some cases, medulloblastoma is associated with certain inherited diseases, including:
- Li-Fraumeni syndrome
- Nevoid basal cell carcinoma syndrome (Gorlin syndrome)
- Turcot syndrome
It's important to understand that these and other brain tumors most often occur with no known cause. There's nothing that you could have done or avoided doing that would have prevented the tumor from developing.
Brain tumors can cause a variety of symptoms in children based on their age and the location of the tumor. Keep in mind that medulloblastoma symptoms may resemble other more common conditions or medical problems. Always consult your child's physician for a diagnosis.
While your child may experience symptoms differently, common medulloblastoma symptoms include:
- Headache (generally upon awakening in the morning)
- Nausea and vomiting
- Imbalance and lack of coordination
- Problems with motor skills (such as writing)
- Neck tilt or double vision
- Changes in personality or behavior
Rarely, medulloblastoma can spread into the central nervous system or the spinal canal, and your child may experience:
- Loss of strength in the lower extremities
- Back pain
- Bowel and bladder control issues
- Difficulty walking
How We Diagnose Childhood Medulloblastoma
Doctors typically diagnosis medulloblastoma with advanced imaging studies.
The first step in treating your child is forming an accurate and complete diagnosis.
Your child’s physician may order a number of different tests to determine the type and location of the tumor. In addition to a physical exam, medical history, and neurological exam, diagnostic procedures for medulloblastoma may include:
- Magnetic resonance imaging (MRI): This diagnostic procedure produces detailed images of structures within the brain and spine. An MRI scan of the brain after surgery will determine how much of the tumor was removed surgically.
- Surgical resection: After surgical removal of the tumor, a tissue sample will be taken and analyzed to confirm the diagnosis. While an MRI may indicate a possible medulloblastoma, only a tissue sample can confirm the diagnosis.
- Histological diagnosis: The tissue sample obtained from surgery will be reviewed by a neuropathologist, who looks at the tumor under the microscope to confirm whether it has the features of medulloblastoma. We also perform a number of molecular tests to determine the subtype of medulloblastoma. All children undergoing resection of brain tumors at Dana-Farber/Boston Children’s are also invited to participate in our ongoing genetic tumor profiling research studies. These studies may help further define tumor subtypes and may potentially guide personalized (precision) medicine.
If your child has medulloblastoma, your child’s physician also will perform a lumbar puncture, or spinal tap. However, this will be performed at a time after the initial surgery is completed. In addition, there may be other diagnostic tests that your doctor will discuss with you.
How We Classify Childhood Medulloblastoma
Successfully treating your child’s medulloblastoma depends largely on whether the tumor can be completely removed through surgery and whether the tumor has spread to other parts of the brain or spinal cord. Typically, post-surgery medulloblastomas are divided into three risk assessment groups:
- Infants (children under age 3)
- Standard risk (no evidence of disease with a complete removal of the tumor)
- High risk (evidence of incomplete removal or tumor spread elsewhere in the nervous system)
- WNT Medulloblastoma
- Sonic Hedgehog (SHH) Medulloblastoma
- Group 3 Medulloblastoma
- Group 4 Medulloblastoma
Each of these subtypes has a different biological driver, and some subtypes require more intensive treatments than others. These findings are guiding clinical trials exploring new treatments for children with medulloblastoma.
After we complete all necessary tests, our experts meet to review and discuss what they have learned about your child's condition. Then we will meet with you and your family to discuss the results and outline the best treatment options.
How We Treat Childhood Medulloblastoma
Your child's physician will determine a specific course of medulloblastoma treatment based on several factors, including:
- Your child's age, overall health, and medical history
- Type, location, and size of the tumor
- Extent of the disease
- Your child's tolerance for specific medications, procedures, or therapies
- How your child's doctors expect the disease to behave
There are a number of treatments we may recommend. Some of them help to treat the tumor while others are intended to address complications of the disease or side effects of the treatment.
In all cases, a multidisciplinary team is necessary to optimize care. The team may include members from neurosurgery, neuro-oncology, neurology, radiation oncology, and stem cell transplantation, as well as psychology/social work, nutrition, and physical and occupational therapy.
Treatment may include (alone or in combination):
In an endoscopic third ventriculostomy, surgeons create a small hole that allows fluid to flow around the blockage and into the spinal column. About 90 percent of children with symptoms of hydrocephalus will undergo this procedure.
In some cases, children may have an alternative procedure in which a tube is installed to drain excess fluid into the abdomen (VP shunt).
- Endoscopic third ventriculostomy (ETV) or ventriculo-peritoneal shunt (VP shunt): A tumor in the brain can cause blockage of cerebral spinal fluid, the fluid that bathes the brain and spinal cord. If this occurs, our pediatric neurosurgeons may perform a procedure to relieve symptoms of hydrocephalus, the build-up of fluid, which causes increased pressure within the skull.
- Surgery may be needed to treat hydrocephalus (fluid build-up in the skull) and to remove the tumor. Research has shown that the more completely the tumor is removed, the better the outcome may be. Therefore, your child's surgeon will remove as much of the tumor as safely as possible, while avoiding neurological side effects.
- Radiation therapy uses high-energy waves from a specialized machine to damage or destroy cancer cells and shrink tumors. Your child's physician will work with pediatric radiation oncologists to determine the optimal dose of radiation that will effectively treat the tumor while avoiding side effects as much as possible.
- Chemotherapy is a group of drugs that interfere with the cancer cell's ability to grow. Different groups of chemotherapy drugs work in different ways to fight cancer cells and shrink tumors. Your child may receive chemotherapy:
- Orally, as a pill to swallow
- Intramuscularly, as an injection into the muscle or fat tissue
- Intravenously, as a direct injection into the bloodstream; also called IV
- Intrathecally, as a direct injection into the spinal column through a needle
After surgery, your child may have difficulties with coordination, weakness in his extremities, and problems with balance. These typically resolve over a course of several weeks. Our physical and occupational therapists will work with your child to treat these issues.
"Posterior fossa mutism" is a condition that may occur after surgery. Within 24 hours, the child develops an inability to speak, has problems with balance, and has difficulty with swallowing. The condition may range from mild to severe. The cause of this condition is not entirely known, but it is unique to this area of the brain.
In about 15 percent of the children diagnosed with medulloblastoma, hydrocephalus may develop, requiring a procedure to drain spinal fluid. These procedures are performed by our pediatric neurosurgeons.