Brain tumors are a significant health concern in children. While not as common as other childhood conditions, understanding rare types is important due to their unique characteristics.
Defining Rare Childhood Brain Tumors
Childhood brain tumors differ from those in adults in location and cell types. Pediatric tumors are often in lower brain parts like the brain stem and cerebellum, regions that influence movement and coordination. The incidence in children is lower (5.7 per 100,000) than in adults (29.9 per 100,000). A tumor is categorized as rare based on its very low occurrence rate.
Many childhood brain tumors also exhibit distinct biological and molecular characteristics, which influence their behavior and response to therapies. Unlike some adult tumors, childhood brain tumors are less likely to transition from a slow-growing, less aggressive state to a fast-growing, more serious one. These differences highlight why understanding the specific nature of pediatric brain tumors is important for their diagnosis and management.
Common Types of Rare Childhood Brain Tumors
Several rare brain tumor types affect children, each with distinct features and locations.
Atypical Teratoid/Rhabdoid Tumor (AT/RT)
Atypical Teratoid/Rhabdoid Tumor (AT/RT) is a highly aggressive tumor often arising in the cerebellum or brainstem but can occur elsewhere. It is characterized by specific genetic changes, particularly in the SMARCB1 gene.
Choroid Plexus Carcinoma (CPC)
Choroid Plexus Carcinoma (CPC) develops from the choroid plexus, a cell network producing cerebrospinal fluid within the brain’s ventricles. This aggressive tumor can spread through cerebrospinal fluid pathways.
Diffuse Midline Glioma (DMG)
Diffuse Midline Glioma (DMG), previously Diffuse Intrinsic Pontine Glioma (DIPG), is a highly infiltrative tumor primarily in the brainstem, particularly the pons. Its diffuse nature means it grows intertwined with healthy brain tissue, making surgical removal difficult.
Ependymomas
Ependymomas originate from ependymal cells lining the brain’s ventricles and spinal cord’s central canal. While they can occur in different locations, certain subtypes, especially in the posterior fossa, are more common in children.
Craniopharyngiomas
Craniopharyngiomas are typically benign tumors forming near the pituitary gland. Their location can affect vision and hormone regulation due to pressure on nearby structures like the optic nerves and hypothalamus.
Identifying and Diagnosing These Tumors
Identifying a brain tumor in a child is challenging as symptoms are often subtle and resemble common childhood illnesses. Symptoms vary widely by tumor location, size, and growth rate. Tumors at the brain’s base can cause headaches, vomiting, and behavioral changes by obstructing cerebrospinal fluid flow, increasing intracranial pressure.
Common Symptoms
Common signs include:
Frequent nausea and vomiting
Headaches, often worse in the morning
Seizures
Changes in vision, hearing, or speech
Issues with balance or coordination
Personality shifts
Delays in developmental milestones like walking or talking
Increased head size in babies
Diagnosis Methods
When a brain tumor is suspected, a medical team conducts a neurological examination to assess reflexes, muscle strength, eye and mouth movement, coordination, and alertness. Imaging techniques visualize the brain; Magnetic Resonance Imaging (MRI) is most effective for detecting brain and spinal cord tumors, providing detailed images without radiation. Computed Tomography (CT) scans may also be used, though they offer less detail. A definitive diagnosis typically requires a biopsy, where a tissue sample is removed, often during surgery, for laboratory analysis.
Treatment Strategies
Treatment for rare childhood brain tumors involves a multidisciplinary approach. Teams of specialists, including neuro-oncologists, neurosurgeons, and radiation oncologists, develop individualized plans. The specific strategy depends on the tumor type, size, location, and the child’s age and overall health.
Surgery
Surgery is often the first step, aiming to safely remove as much of the tumor as possible without damaging healthy brain tissue. This procedure, often a craniotomy, involves opening the skull to access the tumor. If complete removal is not possible, a partial removal may reduce tumor bulk and alleviate symptoms. Shunts may also be placed to drain excess cerebrospinal fluid and relieve pressure.
Radiation Therapy
Radiation therapy uses high-energy beams to destroy cancer cells, used after surgery or as a primary treatment if surgery is not an option. External beam radiation therapy is common. Proton therapy, an advanced form, uses protons that release most energy within the tumor, minimizing damage to healthy tissues, beneficial for developing brains. Doctors may delay or avoid radiation in children younger than three due to potential long-term effects on brain development.
Chemotherapy
Chemotherapy uses medicines to kill tumor cells, administered orally, intravenously, or directly into cerebrospinal fluid. Delivering these drugs to the brain is challenging due to the blood-brain barrier, a protective network. This treatment may be used with surgery and radiation, or as an initial treatment for very young children.
Understanding Causes and Prognosis
For most rare childhood brain tumors, exact causes remain largely unknown. Lifestyle factors influencing adult cancers are not typically significant in childhood cases.
Genetic Factors
Genetic predispositions play a role in a small percentage of cases. Inherited conditions and germline mutations in genes like NF1, P53, or ELP1 link to an increased risk of pediatric brain tumors. Approximately 8% to 19% of children with central nervous system tumors may have an underlying germline alteration.
Environmental Factors
Environmental factors have been investigated, but consistent evidence linking specific exposures to childhood brain tumors is limited. Ionizing radiation from previous medical treatments is the only well-established environmental risk factor. Other suspected factors, such as pesticides, air pollutants, and N-nitroso compounds, show inconsistent associations across studies.
Prognosis
Prognosis for children with rare brain tumors varies significantly based on tumor type, location, resectability, and treatment response. While some tumors have better outcomes, others remain challenging. Advances in treatment, particularly with therapies like proton therapy showing improved neurocognitive outcomes, continue to improve the outlook for many children.