A glioma is a name for tumours of the glial cells. These are the supporting cells of the nervous system. Gliomas can arise in any part of the brain and may also be found in the spinal cord. More than half of all brain tumours in children are gliomas.
There are different types of gliomas. Some examples of gliomas are:
- low-grade gliomas
- diffuse low-grade gliomas
- glioneuronal tumours
A low-grade glioma is the most common brain tumour in children. Low grade means that the glioma is growing slowly (benign tumour).
There are many types of low-grade gliomas. Low-grade gliomas are treated according to their location, morphologic (structural) and molecular characteristics. They are usually treated with surgery, which is sometimes followed by chemotherapy and, more recently, targeted agents. Radiation therapy is rarely used but may sometimes be required. When surgery is not possible, other options are considered, including observation, chemotherapy, or targeted agents.
More recently low-grade gliomas are being classified with molecular alterations. Common alterations with low-grade gliomas are:
- BRAF fusions
- BRAF mutation
- FGFR alterations (not as common)
Types of low-grade gliomas
Cerebellar
This type of low-grade glioma is located at the back of the brain, in the cerebellum. It is commonly treated with surgery. Sometimes, if some tumour remains after surgery, additional therapy is necessary.
Optic/hypothalamic
Optic gliomas are located along nerves that are involved with sight. Hypothalamic gliomas occur in a part of the brain called the hypothalamus. This part of the brain plays an important role in controlling the body’s temperature, water balance, blood sugar levels, and the way the body uses fat (fat metabolism). Optic and hypothalamic tumours are types of low-grade glioma but unlike other low-grade gliomas, they cannot be removed surgically due to their location and the irreversible damage surgery would cause.
Brainstem
Brainstem gliomas are tumours located in the brainstem at the base of the brain. These tumours are difficult to treat. Because the tumour is in an important area, surgery is often incomplete. Following surgery, several options may be considered, including chemotherapy, targeted agents, observation or, rarely, radiation.
Hemispheric
This type of low-grade glioma is in a cerebral hemisphere, in the upper part of the brain. One common symptom is seizures. Hemispheric low grade gliomas are treated with surgery and potentially chemotherapy or targeted agents.
Thalamic
This type of tumour, located in the thalamus, is complex to treat. A biopsy may be done to diagnose the tumour, followed by additional medical treatment.
Spinal cord
This tumour is located in the spinal cord. Children with a spinal cord tumour may sometimes present with a spinal deformity called scoliosis, and/or weakness in their arms or legs. The primary treatment for a spinal cord tumour is surgery. Some children may need chemotherapy, targeted medication or, rarely, radiation.
What are the symptoms of a low-grade glioma?
Common symptoms of a low-grade glioma are:
- headaches
- vomiting
- double vision
The symptoms depend on the location of the glioma. Other symptoms can include seizures, hydrocephalus, lack of coordination, and balance problems.
What causes a low-grade glioma?
It is not known what causes a low-grade glioma. A person with a medical condition called neurofibromatosis type 1 (NF1) has a slightly increased risk of developing a low-grade glioma.
However, there is no way to predict that a child will get a tumour. Nobody is to blame if a child develops a tumour.
Researchers have also been studying whether environmental factors, such as food or chemicals, can cause brain tumours. At the moment, there is no definite proof that there is a connection.
How many other children have low-grade gliomas?
Low-grade gliomas are the most common type of brain tumour in children. In Canada about 100 children are diagnosed with a low-grade glioma each year.
How are low-grade gliomas diagnosed?
Doctors and other health-care professionals will use well-established diagnostic tests to see if a brain tumour is causing your child’s symptoms. These tests will include a physical examination, and brain scans such as magnetic resonance imaging (MRI) . A biopsy may be necessary. This is a type of surgery that allows doctors to remove samples of tumour tissue to determine the exact type of tumour.
The diagnosis of any brain tumour can be a long and difficult process. If the symptoms are dramatic, the diagnosis may happen quickly. If they are milder, it can take many months to identify the source of symptoms.
How are low-grade gliomas treated?
Once the doctors have a clear understanding of what is causing your child’s symptoms — usually after surgery — you will meet with the treatment team. Remember that it is helpful to bring paper and a pen or laptop and take notes at each meeting with this team. Or ask a relative or friend to come to do this for you.
The treatment team may include a neurosurgeon, a neuro-oncologist, a nurse practitioner, nurse, and a social worker. During the meeting, they will explain which doctor is responsible for your child’s treatment, and the roles of everyone who is there.
The doctor will explain the type of tumour that your child has, based on what the team has learned through diagnostic testing. You will learn the expected effect this tumour will have on your child in the upcoming months and years, based on what is known about the tumour. This is called the prognosis.
They may talk about placing your child on a clinical trial or a standard of care treatment which is a treatment plan for a particular tumour. You will need to agree to the plan for the treatment to begin. Teenaged patients may be asked for their agreement as well.
There are three main types of treatment for brain tumours in children. They are surgery, radiation , and chemotherapy or targeted therapy. Your child may have one of these treatments, or a combination of two or more treatments. For some tumours, the best approach is simply observation.
Some children experience hydrocephalus, which is a condition where there is increased pressure in the brain due to the tumour blocking the flow of cerebrospinal fluid (CSF) in the brain. In such cases, a shunt may be surgically implanted to help relieve the pressure in the brain.
Many doctors are trying to make treatments more successful. They can do this by studying different types of treatment, in clinical trials. Your child’s doctor may ask if you would like your child to participate in a clinical trial. You will have to sign an informed consent form for your child to participate in a trial.
When you meet with the treatment team, you may also be told about resources available to support your child, you and your other children during treatment and recovery. You will be encouraged to think about any questions concerning the diagnosis and the treatment plan.
Before you agree to the treatment offered, it is important that you understand what to expect and feel comfortable with your decision.
Recurrence of low-grade gliomas
Surgery may be considered if a low-grade glioma recurs (returns) in an area that can be operated on. It is often the only treatment needed for a cure. Sometimes though, the surgeon may not be able to remove the tumour completely and then you and your child's doctor will need to discuss options to best treat the remaining tumour.
If surgery is not possible, then other options are considered. There are treatment protocols for recurrence that depend on the child’s previous treatment, and how the child responded.
Chemotherapy, targeted agents or, rarely, radiation therapy will be considered.
Radiation therapy will typically only be considered if multiple lines of chemotherapy or targeted agents do not work to control the tumour.