Low-grade gliomas in children

Summarize

Central Nervous System (CNS) tumors are Brain tumors are the second most common tumor in children (20% of all pediatric cancers). There are two main types of cells that make up the CNS: neurons and glial cells. Neurons are responsible for information processing, while glial cells form the support and nourishing network for neurons. Gliomas are CNS tumors that originate in glial cells, and approximately 2/3 of all childhood brain tumors are gliomas.

Glial cells can be further subdivided into different types, including oligodendrocytes, which cover the axons of neurons with myelin sheaths, and astrocytes, which have many functions. Gliomas develop from the abnormal growth of glial cells that support neurons in the brain, i.e., tumors of glial cells, especially astrocytes and oligodendrocytes.

Approximately 60% of brain tumors in children occur in the sub-tentorial region (the posterior cranial fossa). The infratentorial portion is primarily the lower part of the brain near the middle of the back of the head and includes the cerebellum and the brainstem, whose main function is to control movement and balance. The brainstem is the middle part of the brain that connects the brain to the spinal cord. The brainstem controls breathing as well as eye movements and transmits information about sensations and involuntary muscle movements. The epencephalon is the main part of the brain above the cerebellum and is the largest part of the central nervous system. The brain controls thinking, emotions, problem solving, learning, speaking, reading, writing, and voluntary movement. Gliomas can be seen anywhere in the brain or spinal cord.

Gliomas can be classified into four grades based on the grading system most commonly used by the World Health Organization (WHO). WHO grade I and II gliomas are considered low-grade, and although these tumors are not considered benign, they are slow-growing and do not usually spread to other tissues or organs. WHO grades III and IV are high-grade gliomas that are more malignant.

Low Grade Gliomas (LGG) are the most common type, accounting for almost half of all CNS tumor types. Most low-grade gliomas are treatable or even curable. For example, the most common type, hairy cell astrocytoma, has a cure rate of over 90%.

Epidemiological

In the United States, the annual incidence of LGG in children is 1.3 to 2.1 cases per 100,000 population, with an estimated 1,000-1,600 new cases per year.

Etiolog & Risk factors

The cause of most brain tumors is unknown. A very small percentage of gliomas are caused by inherited genetic mutations, including NF1 and NF2 mutations in type I neurofibromatosis, TSC1 and TSC2 mutations in tuberous sclerosis, TP53 mutations in LI-Fraumeni syndrome, and multiple mutations associated with Turcot's disease.

In addition, scientists have studied many potential causative factors and have found that ionizing radiation to the head (e.g., X-rays and radioactive substances) may increase the chances of developing the disease, but there is no scientific evidence to suggest that cell phones, head trauma, exposure to petrochemicals, or aspartame increase the chances of developing low-grade gliomas. A history of allergies or atopic disease, on the other hand, may reduce the risk of glioma.

Classification & Stage

There are many types of low-grade gliomas (LGGs), and they are classified clinically based on the appearance of the tumor under the microscope and where it is located. The more common LGGs are:

● hairy cell astrocytoma

This type of LGG consists of astrocytes, so named because of the spindle-shaped (hair cell-like) nature of these astrocytes. These tumors usually grow in the cerebellum or hypothalamus, they generally have well-defined borders, and they generally do not cause edema.

● Fibrous astrocytoma

This type of LGG also consists of astrocytes, but with tiny fibers or filaments. The tumors can occur in any part of the brain and are often found more often in the brainstem (midbrain portion). Another thing that distinguishes them from hairy cell astrocytomas is that they do not have well-defined borders.

● optic nerve glioma

This type of LGG is a hairy cell astrocytoma that occurs on the optic nerve or optic nerve pathway. This tumor is usually associated with type I neurofibromatosis.

● pleomorphic yellow astrocytoma

This type of LGG is also an astrocytoma, but is often associated with cysts and the tumor usually occurs in the temporal cortex.

● Hairy Cell Mucinous Astrocytoma

This type of LGG is a subtype of hairy cell astrocytoma and only shows subtle differences under a microscope. This tumor is more aggressive compared to hairy cell astrocytoma.

● Subventricular giant cell astrocytoma (SEGA)

These tumors are common in children with tuberous sclerosis. Tumors occurring near the ventricles of the brain can cause hydrocephalus.

Clinical manifestations

Although low-grade gliomas are slow-growing tumors, as the tumor grows, the normal surrounding nerve tissues are compressed and their function is affected. Therefore, the symptoms of low-grade glioma in children depend largely on the size of the tumor and where it develops in the CNS.

The most common symptoms of low-grade gliomas in children include:

● Headaches, especially in the morning or better after vomiting

● Severe or frequent vomiting without other signs of gastrointestinal disease

● Visual disturbances such as double vision (diplopia), blurred vision or loss of vision

● Difficulty walking or balancing

● convulsive seizure

● Significant weight gain or loss

● Early puberty (precocious puberty)

● Clumsiness (coordination disorder)

● fuzzy

● weary

● Behavior change

Clinical Department

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Examination & Diagnosis

In order to properly diagnose low-grade gliomas in children, the doctor will take the child's medical history and perform a variety of tests, including a general and neurological exam. In addition, the doctor may perform a variety of other tests on the child, including:

● Magnetic Resonance Imaging (MRI) Scan: used to evaluate the tumor and determine its extent;

● Biopsy or sampling of the tumor: the pathologist can analyze the tissue specimen to define the type of tumor and its grading, and to analyze the molecular pathological staging of the tumor;

● Electroencephalography (EEG): It measures the electrical activity of the brain;

● Lumbar puncture: The doctor may take a small sample of cerebrospinal fluid from the spinal canal and perform biochemical and cytological tests to see if any tumor cells are distributed in the cerebrospinal fluid.

Clinical Management

Treatment for low-grade gliomas depends largely on the type, stage, and location of the tumor and the age of the child. Not all low-grade gliomas require treatment, and if the tumor is not causing symptoms, the child will often only need to be monitored regularly by a doctor.

Some therapies are designed to treat tumors, while others are designed to address complications of the disease or side effects of treatment. In addition, clinicians may offer targeted therapies based on the molecular typing profile of the child's tumor. Currently, the main therapies are listed below:

1. Surgery

The goal of surgery is to remove as much of the tumor as possible without damaging normal brain tissue. If the neurosurgeon believes that surgery in the area where the tumor is growing may result in serious surgical side effects (such as paralysis or loss of vision), the surgical approach changes to a biopsy, which is the safe removal of a small piece of the tumor tissue in order to make a definitive pathological diagnosis of the tumor.

Generally hairy cell astrocytomas or pleomorphic yellow astrocytomas in the cerebellum can usually be completely removed by surgery. Fibrous astrocytomas, on the other hand, are difficult to remove completely with surgery, which is primarily a biopsy to clarify the diagnosis. Usually, completely resected low-grade gliomas do not require any other additional treatment.

2. Chemotherapy

Chemotherapy may be given to shrink the tumor before surgery or to remove residual tumor cells after surgery. In younger children, chemotherapy can be used to supplement radiation therapy, delaying the time when radiation therapy is given and reducing the possible side effects of radiation therapy.

There are several types of effective chemotherapy available, some administered intravenously and others orally, with varying dosing cycles. Consultation with an experienced neuro-oncologist is generally required to determine the appropriate chemotherapy regimen for the appropriate pathologic diagnosis and the efficacy of surgical therapies.

3. Radiotherapy

Radiotherapy is also a very effective treatment for brain tumors. In older children, radiotherapy is usually the treatment of choice when low-grade gliomas cannot be completely removed. However, radiotherapy is not commonly used in younger children because of its significant adverse effects on brain development.

There are also children with low-grade gliomas in need of treatment who can participate in clinical trials to try to apply new therapies on an experimental basis.

Prognosis

The overall prognosis for children with low-grade gliomas is good, with 5-year survival rates reaching 90%. The prognosis for children with low-grade gliomas depends on many different factors, including:

● Tumor type

● Tumor classification

● Extent of the disease

● Size and location of the tumor

● have or have not metastasized

● Tumor response to treatment

● Age and general health status of the child

● Tolerance of the child to specific drugs, manipulations or treatments

● New advances in treatment

The best prognosis depends on prompt treatment and appropriate therapies. Many brain tumor survivors face challenges related to various aspects of their treatment, which will require ongoing evaluation and specialized follow-up, making scheduled follow-up visits important. At the follow-up visit, the physician may suggest the following tests and tailor treatment and interventions:

● MRI scans to monitor tumor recurrence

● Assessment of intellectual functioning

● Assessment of endocrine function

● Neurological function assessment

● Motor function assessment

● Evaluation of other vital organ function

● Psychosocial assessment

Follow-up & Review

Children may have developmental delays in intellectual and motor function due to treatment, and the establishment of an individualized follow-up and treatment plan will maximize the quality of the child's academic life.