Medulloblastoma

Medulloblastoma is a malignant brain tumor that forms in the cerebellum. The cerebellum controls balance, movement and posture. Medulloblastoma is a type of embryonal tumor, which means it starts in immature cells left over from early development. All medulloblastomas are grade 4, meaning they grow fast.

Medulloblastoma tends to spread through the cerebrospinal fluid, the fluid around the brain and spinal cord. It can seed other parts of the brain and the spine. Spread outside the brain and spine is rare at diagnosis.

Doctors now sort medulloblastoma into groups by the tumor’s genes. The main groups are WNT-activated (about 10%), SHH-activated (about 25%), group 3 (about 25%) and group 4 (about 40%). These groups differ in age, how the tumor behaves and how well treatment works, so they now guide treatment. Medulloblastoma mostly affects children, but about 3 in 10 cases occur in adults, usually between ages 20 and 40.

Medulloblastoma is caused by changes in genes that control how brain cells grow and divide. In most children, the exact cause of these changes is not known. Like other cancers, medulloblastoma does not spread from person to person.

About 5 in 100 people with medulloblastoma have an inherited gene change that raises the risk of this and other cancers. Linked conditions include Gorlin syndrome (PTCH1 or SUFU genes), Li-Fraumeni syndrome (TP53), Turcot syndrome (APC), Rubinstein-Taybi syndrome and Fanconi anemia. In the SHH group, inherited changes are more common. One gene, ELP1, was found in 14% of children with SHH medulloblastoma.

Because of this, the NCI says genetic counseling may be offered to families. A counselor can explain which gene tests may help and what the results could mean for the child and for brothers and sisters.

Most early symptoms come from the tumor blocking the flow of fluid in the brain. The fluid builds up (hydrocephalus) and raises pressure inside the head. Common signs are headaches, often worse in the morning, nausea and vomiting, tiredness, and double vision or other eye problems. Children are usually diagnosed within 2 to 3 months of the first symptoms.

Because the cerebellum controls balance, many children become unsteady, clumsy or have trouble walking. Babies may be irritable, feed poorly, grow slowly, fall behind on milestones such as sitting or walking, or have a growing head size.

If the tumor has spread to the spine, it can cause back pain, trouble walking, or changes in bladder or bowel habits. Between 10% and 40% of children already have spread within the brain or spine when they are diagnosed. Babies are the most likely to have spread, and teens and adults the least likely.

Treatment is intense and usually lasts many months. After surgery, some children develop cerebellar mutism syndrome, also called posterior fossa syndrome. It usually starts within a day or two of surgery. A child may lose speech for a time and have trouble swallowing, moving and controlling emotions. It happens in about 1 in 4 children with medulloblastoma. About half of those children have lasting effects on the nervous system and on thinking skills.

Care teams include neurosurgeons, cancer doctors, radiation doctors, neurologists, rehabilitation specialists and psychologists. St. Jude says care after treatment should include rehabilitation and visits with a neurologist.

Survivors face late effects. These can include problems with learning and memory, hearing loss from cisplatin, slow growth and hormone problems, fertility problems, heart problems and second cancers. The youngest children are at highest risk from radiation. Regular brain and spine scans continue for years, because medulloblastoma most often comes back within 3 years but can return later.

Medulloblastoma is not treated with a donor stem cell transplant. When stem cells are used, the transplant is autologous. The child’s own stem cells are collected and frozen before high-dose chemotherapy and then given back to help the bone marrow recover. No registry donor is needed, and no donor search is part of the plan.

European transplant experts (EBMT) rate donor transplants for children’s brain tumors as generally not recommended. They rate own-cell transplants as developmental in children, and as a clinical option for adults with high-risk or returning medulloblastoma.

For families facing medulloblastoma, joining a blood stem cell registry is a way to help other patients, such as children with leukemia, rather than a need of their own.