Medulloblastoma in children — what every parent needs to know

Medulloblastoma is a malignant brain tumour that begins in the cerebellum — the part of the brain at the back of the skull that controls balance and movement. It arises from rapidly dividing cells and can spread through the cerebrospinal fluid to the spine. It is the most common malignant brain tumour in children, most often seen between the ages of 3 and 8, and it is slightly more common in boys than in girls. Medulloblastoma is a serious diagnosis, but it is also one of the paediatric brain tumours for which multimodal treatment — surgery, radiation, and chemotherapy working together — can produce good outcomes when care is expert-led and started without delay.

The earliest signs of medulloblastoma are usually caused by raised pressure inside the skull as the tumour grows and blocks cerebrospinal fluid flow. Parents should watch for: morning headaches that are worse on waking and ease through the day; vomiting without obvious nausea, especially first thing in the morning; unsteady walking, stumbling, or a noticeable change in balance; clumsiness or deterioration in handwriting; double vision or eyes that do not move together; and a new head tilt. These symptoms can seem like a viral illness at first. If several of these signs appear together, or if they persist for more than one to two weeks without a clear cause, your child needs to be assessed by a doctor promptly — an MRI of the brain will usually clarify the picture.

Yes. Pathologists now classify medulloblastoma by both histology (how the cells look under a microscope) and molecular biology (specific genetic changes inside the tumour cells). There are four main molecular subgroups: WNT-activated, SHH-activated, Group 3, and Group 4. The WNT subgroup generally has the most favourable outcomes; Group 3 carries the highest risk of spread and relapse and requires the most intensive treatment. The histological subtypes include classic medulloblastoma, desmoplastic/nodular, and the large-cell/anaplastic variant. Knowing both the histological and molecular profile is essential because it directly determines the treatment plan and risk classification for your child. At CION, every tumour sample undergoes full molecular profiling as part of our tumor board review.

Diagnosis begins with an MRI of the brain with contrast — this typically shows a tumour in the posterior fossa. Because medulloblastoma can spread to the spine through cerebrospinal fluid, a full spinal MRI is done at the same time. A lumbar puncture to examine the cerebrospinal fluid for tumour cells is also performed, usually after surgery when it is safer. The definitive diagnosis comes from the surgical biopsy or tumour resection: the removed tissue is sent for histopathology, immunohistochemistry, and molecular profiling including DNA methylation classification and testing for WNT, SHH, and other subgroup markers. A staging work-up determines whether the tumour is confined to the brain or has spread along the spinal cord.

Treatment always begins with surgery to remove as much of the tumour as safely possible — maximal safe resection significantly improves outcomes. After recovery, children over 3 years of age typically receive craniospinal radiation therapy, which targets the entire brain and spinal cord, followed by a boost to the tumour site. Chemotherapy is then given to reduce the risk of relapse. Children under 3 are managed differently because radiation to the developing brain carries significant developmental risks; they may receive intensive chemotherapy instead. The exact plan depends on the molecular subgroup, staging, and the surgical outcome. At CION, this plan is decided by a multidisciplinary tumor board — not a single doctor — so your child benefits from coordinated expertise across surgery, radiation oncology, and medical oncology simultaneously.

Because treatment for medulloblastoma includes radiation to the brain and spine in most children over 3, parents should be aware that long-term side effects are a real consideration. These can include effects on learning and memory (neurocognitive effects), growth hormone deficiency, hearing changes, and effects on the spine and long bones from radiation. The degree of impact varies depending on the child's age at treatment, the radiation dose used, and the molecular subgroup. Modern protocols aim to reduce radiation dose in lower-risk children precisely to protect the developing brain. Our team at CION works with you to plan for and monitor these effects — we involve rehabilitation, endocrine, and neuropsychology support from early in the journey, not as an afterthought. You deserve complete, honest information about what treatment involves and what to expect in the years that follow.