Low-grade glioma in children — compassionate, coordinated care from diagnosis to recovery

A low-grade glioma is a slow-growing brain or spinal cord tumour that arises from glial cells — the supportive cells of the central nervous system. In children, these tumours are classified as WHO Grade 1 or Grade 2 under the World Health Organization brain tumour classification. The most common type in children is pilocytic astrocytoma (WHO Grade 1), which tends to be well-defined and often curable with surgery alone. Grade 2 tumours such as diffuse astrocytoma grow more slowly than high-grade gliomas but can gradually affect nearby brain tissue. The word “low-grade” refers to how slowly the tumour cells divide when viewed under a microscope — not that the tumour is unimportant or that symptoms are mild. Depending on where the tumour sits in the brain, even a slow-growing tumour can cause significant symptoms. CION reviews every paediatric brain tumour case at a multidisciplinary tumor board before any plan is made.

Pilocytic astrocytoma is the most common low-grade brain tumour in children and one of the most common paediatric brain tumours overall. It is a WHO Grade 1 tumour, meaning it is the slowest-growing category. It most often arises in the cerebellum (the part of the brain at the back that controls balance and co-ordination), but can also occur in the optic pathways, hypothalamus, brainstem, or spinal cord. Unlike high-grade gliomas, pilocytic astrocytoma tends to be well-defined rather than infiltrating the surrounding brain, and in many locations it can be completely removed with surgery, which often results in long-term disease control. However, tumours in the optic pathway or hypothalamus may be difficult to fully remove because of their location near critical structures, and these children need careful, long-term follow-up. Pilocytic astrocytoma is biologically different from the aggressive gliomas seen in adults or in children with DIPG.

Symptoms of a low-grade glioma depend on where in the brain or spinal cord the tumour is located, and they often develop slowly over weeks or months because the tumour grows slowly. Common symptoms include persistent headaches, nausea and vomiting (especially in the morning), problems with balance or unsteady walking, vision changes such as blurring or loss of a part of the visual field, eye wobbling or unusual eye movements (nystagmus), problems with co-ordination, and in younger children, unexplained irritability or change in behaviour. Optic pathway tumours — which are common in children with neurofibromatosis type 1 (NF1) — may cause gradual loss of vision in one or both eyes, sometimes noticed only when a child sits close to the television or struggles at school. Spinal cord tumours may cause back pain, weakness in the legs, or bladder or bowel changes. If you have noticed a gradual change in your child’s co-ordination, vision, or headache pattern over several weeks, speak to a doctor promptly.

Diagnosis begins with an MRI of the brain, usually with and without contrast dye. Low-grade gliomas have characteristic features on MRI that help neuroradiologists and neurosurgeons assess the likely tumour type, its size, and its location. For pilocytic astrocytoma in the cerebellum or cerebral hemispheres, the MRI appearance is often distinctive enough to guide surgical planning directly. In some locations — particularly the optic pathways in children known to have NF1 — a biopsy may not be needed and the diagnosis may be made on imaging and clinical history alone. Where tissue can be safely obtained, molecular testing is now standard to confirm the tumour subtype and check for specific genetic alterations (such as the BRAF fusion that is very common in pilocytic astrocytoma). The full picture — MRI, pathology, and molecular results — is reviewed at the CION paediatric tumor board before a treatment recommendation is made.

For many children with low-grade glioma — particularly those with a pilocytic astrocytoma (WHO Grade 1) that can be completely removed with surgery — long-term disease control is achievable. Complete surgical removal is often the goal for accessible tumours, such as cerebellar pilocytic astrocytoma, and many children who achieve a complete resection do not experience a recurrence. However, “cured” is a word used carefully in oncology: long-term follow-up with MRI scans is needed for all children with low-grade glioma, because even after complete removal there is a possibility of recurrence, and Grade 2 tumours that cannot be fully removed may require ongoing monitoring or treatment over many years. For tumours in difficult locations such as the optic pathway, hypothalamus, or brainstem, complete removal may not be possible; in these cases, the goal is to control the tumour and preserve function. We will be honest with you about what is realistic for your child’s specific situation.

Treatment depends on the tumour type, its location, how much can be safely removed, and the child's age. Surgery is the primary treatment for most accessible low-grade gliomas — the aim is to remove as much of the tumour as safely possible without damaging critical brain functions. For completely removed pilocytic astrocytoma, no further treatment may be needed, and the child is followed with regular MRI scans. When surgery cannot remove all of the tumour, or when the tumour grows back, additional treatments including chemotherapy and radiation therapy may be recommended. Radiation therapy is generally avoided in very young children with low-grade glioma where possible, because of the potential effects on the developing brain; chemotherapy may be used first in these cases to control growth. For tumours with specific molecular features — such as certain BRAF alterations — targeted approaches are an area of active clinical research. At CION, the treatment plan for every child is decided by the full multidisciplinary tumor board, not a single doctor.