Gliomas are among the most common brain tumors in children and adolescents. They can develop in the cerebral hemispheres, the cerebellum, the optic tracts, the brainstem, the thalamus, or the spinal cord. Their course ranges from localized forms—which can sometimes be cured by surgery alone—to diffuse tumors that are very difficult to treat.

The terms “low-grade” and “high-grade” remain useful for understanding a tumor’s overall aggressiveness, but they are no longer sufficient to define it. The current classification distinguishes pediatric gliomas specific to children, which are biologically distinct from adult-type gliomas. It incorporates molecular alterations that help refine the diagnosis and may open the door to targeted therapy or a clinical trial.

For a long time, gliomas were primarily classified based on their histological appearance. The World Health Organization’s classification, published in 2021, places a central emphasis on genetic and epigenetic alterations. In particular, it distinguishes between pediatric-type diffuse gliomas and adult-type diffuse gliomas and recognizes new entities.

Low-grade pediatric gliomas generally grow slowly. Their overall prognosis is often favorable, but their location may threaten essential functions, such as vision, motor function, or endocrine function. Some tumors remain stable for a long time, while others progress or recur and require multiple lines of treatment.

Pilocytic astrocytoma

Pilocytic astrocytoma is one of the most common gliomas in children. It can develop in various regions of the central nervous system, particularly the cerebellum and the optic pathways. In many cases, it is a well-circumscribed tumor classified as Grade 1 by the WHO, but its behavior depends heavily on its location and the feasibility of removing it without causing sequelae.

When complete resection is possible—particularly for certain tumors of the cerebellum—surgery may be the only treatment required. If the tumor cannot be safely removed, monitoring, chemotherapy, or targeted therapy may be considered depending on its progression and molecular profile.

Optic pathway gliomas

These gliomas affect the optic nerve, the optic chiasm, or the visual pathways. They can cause vision loss, strabismus, abnormal eye movements, or—when they involve the hypothalamic-pituitary region—endocrine disorders. In young children, vision loss can be difficult to detect.

The primary strategy is to preserve vision and development. Simple monitoring may be recommended if the tumor is stable and visual function is preserved. When treatment is necessary, chemotherapy or therapy targeting the MAPK pathway may be considered depending on the situation. Surgery is reserved for specific indications, and radiation therapy is used with caution in children.

Neurofibromatosis Type 1

Neurofibromatosis type 1, or NF1, is a genetic disorder that notably increases the risk of optic pathway glioma. It can be hereditary or present for the first time in a child. Its manifestations vary widely. The presence of café-au-lait spots may warrant a specialist evaluation, but it is not sufficient on its own to establish a diagnosis of NF1.

Other Low-Grade Gliomas and Glioneuronal Tumors

Dysembryoplastic neuroepithelial tumors (DNETs) and certain gangliogliomas often present with epilepsy. When these tumors are resectable, surgery can control seizures and may be sufficient treatment. Other entities, such as low-grade diffuse glioma with MAPK pathway alteration, require precise molecular characterization to avoid confusion with adult-type tumors.

High-grade pediatric gliomas are rare and aggressive diseases. Their classification has changed significantly with the discovery of alterations specific to children, particularly in histones and the mechanisms that control DNA organization and expression. Their management must be tailored to the molecular profile and should not automatically mirror that of adult glioblastoma.

Infiltrating brainstem glioma

When located in the pons, symptoms may include balance problems, weakness on one side of the body, double vision, facial asymmetry, and difficulty speaking or swallowing. MRI is highly suggestive of this condition, but a biopsy is currently being considered in specialized centers to confirm the molecular diagnosis and identify abnormalities that can guide treatment decisions or determine eligibility for a clinical trial.

Radiation therapy is the standard of care for temporarily controlling the disease and alleviating symptoms. Drug therapies are primarily evaluated in clinical trials. A second course of radiation therapy may sometimes be considered in the event of disease progression, depending on the time elapsed since the first course of radiation, the child’s condition, and the clinical situation.

Symptoms vary depending on the affected area and the rate of progression. They may be mild at first and are not specific to a tumor. If they persist, worsen, or occur in combination, a medical evaluation is warranted.

An MRI of the brain or spinal cord determines the tumor’s location, whether it is circumscribed or infiltrating, and its relationship to neighboring structures. Depending on the situation, an MRI of the entire central nervous system may be performed to complete the evaluation.

When feasible and beneficial, surgery or a biopsy provides the tissue necessary for a comprehensive diagnosis. Pathological analysis is supplemented by molecular tests. These may screen for alterations in BRAF, the MAPK pathway, histones H3, MYB or MYBL1, gene fusions, and other markers relevant to the suspected tumor.

In certain very specific situations—particularly for an optic tract glioma associated with NF1—the diagnostic strategy may be adjusted. The decision to perform a biopsy takes into account the expected benefit, the risk of the procedure, and the impact of the result on treatment.

Treatment is tailored to the individual. Watchful waiting may be appropriate for a stable tumor that does not pose a functional threat. In other situations, several approaches are combined or used sequentially.

Surgery

The goal is to remove the tumor or obtain a biopsy while preserving neurological function. Complete resection may be curative for certain low-grade, circumscribed gliomas. It is not possible when tumor cells have infiltrated a critical structure.

Chemotherapy

It is used in particular for progressive low-grade gliomas when surgery is insufficient or not feasible. The choice of drugs depends on age, tumor type, prior treatments, and available protocols.

Targeted Therapies

BRAF or MEK inhibitors may be recommended for certain tumors with a corresponding alteration in the MAPK pathway. The choice depends on the exact abnormality, as not all BRAF alterations are treated in the same way. Other gene fusions may also serve as targets in rare forms of the disease.

Radiation Therapy

It may be indicated for high-grade gliomas, inoperable tumors, or certain cases of disease progression. The treatment fields, doses, and technique are tailored to the patient’s age, tumor location, and prior treatments. Proton therapy may reduce exposure to certain healthy tissues in selected cases, but its benefit depends on the target geometry and not solely on the diagnosis.

Clinical Trials

They play an important role in high-grade gliomas and relapsed disease. They can evaluate new drugs, drug combinations, treatments guided by tumor biology, or new administration methods.

Ependymomas have long been classified alongside gliomas because of their glial origin. In the current classification, they constitute a distinct family of ependymal tumors. Their diagnosis takes into account location and molecular characteristics, particularly for posterior fossa and supratentorial forms.

Surgery is crucial, and the team evaluates the possibility of a second procedure when residual tumor can be removed without disproportionate risk. For a non-metastatic intracranial ependymoma, highly conformal local radiation therapy is generally recommended after surgery. The role of chemotherapy remains more limited and depends, in particular, on the patient’s age and the chosen treatment strategy.

Follow-up care combines MRI scans with a clinical evaluation tailored to the type of tumor. It monitors for disease progression or relapse, as well as the neurological, visual, endocrine, cognitive, auditory, motor, and psychosocial effects of the disease and its treatments.

The Department of Pediatric and Adolescent Oncology coordinates multidisciplinary care with teams specializing in imaging, neuropathology, molecular biology, radiation therapy, partner neurosurgery, rehabilitation, and supportive care. Rare or complex cases can be discussed within specialized networks.

Research on pediatric gliomas combines biological characterization, preclinical models, precision medicine, and clinical trials. At Gustave Roussy, the BIOMEDE program relies in particular on biopsy and molecular analysis of infiltrating brainstem gliomas to evaluate strategies tailored to tumor biology. Ongoing trials are evolving and must be linked, on the website, to the institution’s clinical trial database.