Overview

Gliomas are the most common primary tumours of the brain and spinal cord.¹ A tumour forms when a mass of abnormal cells group together and grow. Gliomas are primary because they originate in the brain tissue rather than spreading to the brain from another site.¹ Gliomas have some characteristics of normal brain cells called glial cells. Glial cells support, protect and nourish neurons (nerve cells). 

Gliomas are usually more common in older adults than children and in people assigned male at birth (AMAB) than in those assigned female at birth (AFAB).² 

There are 3 main types of glioma, which are classified according to the type of glial cell they originated from and also how abnormal the tumour cells look. According to the World Health Organisation (WHO), gliomas can be graded from I to IV, depending on how malignant they are.³ The more normal the cells look the lower the grade, and the more abnormal the cells look the higher the grade. Some gliomas are slow-growing and aren’t considered to be cancers as they don’t invade healthy brain tissue. The most aggressive form of grade IV glioma, which grows quickly, is known as glioblastoma multiforme. 

As the glioma grows, it can press on parts of the brain or spinal cord and lead to symptoms. Symptoms and their treatment, therefore, depend on which area of the brain or the spinal cord is affected.

The survival rates of gliomas depend on the tumour type, tumour grade and a person’s age. Recent studies have also shown that patients with mutations in the isocitrate dehydrogenase (IDH) gene have favourable survival rates.³ 

Types of glioma

As mentioned above, the 3 main types of glioma are grouped according to the glial cell they originated from. Some gliomas contain multiple types of cells, which are called mixed gliomas.

The 3 most common types of glioma are astrocytomas, ependymomas and oligodendrogliomas.

Astrocytomas

These start in glial cells called astrocytes, which support and connect neurons in the brain and spinal cord. Some astrocytomas grow slowly and are, therefore, not considered cancerous (known as benign astrocytomas). Those that grow quickly are considered cancerous (malignant). 

Astrocytoma symptoms depend on the tumour’s location. Astrocytomas are categorised into different grades according to how fast they grow and the likelihood that they will spread to nearby brain tissue. Grade 1 are the mildest and grade 4 the most aggressive astrocytomas.

Astrocytomas are common gliomas in children. Diffuse intrinsic pontine glioma (DIPG) is a rare, but very aggressive form of brain cancer in children, which forms in the brain stem.

Glioblastoma

A glioblastoma is an astrocytoma which grows quickly, spreads throughout the brain and destroys healthy tissue. Glioblastomas make up half of nearly all cancerous brain tumours in adults. There is no cure for glioblastoma and it is difficult to treat, but treatments may slow the cancer's growth and reduce symptoms.

Ependymoma

This is a type of tumour which starts in the ependymocytes within the ventricles of the brain and spinal cord. They do not spread outside of this region, but  may spread through cerebrospinal fluid. Ependymoma most often occurs in children.

Oligodendrogliomas

This tumour begins in cells called oligodendrocytes. Oligodendrocytes are responsible for making myelin, which insulates nerve fibres and helps to conduct electrical signals to and from the brain. Oligodendrogliomas are more common in adults and are one of the more treatable forms of brain tumours. They tend to grow more slowly and rarely spread outside of the brain or spine.

Causes of glioma

The exact causes of gliomas are currently unknown. We do know that they develop due to DNA changes in cells in the brain or spinal cord. A cell contains DNA, which contains instructions about the function of the cell and how it should grow and multiply. Mutations or changes to the DNA will cause the cells to grow out of control to form a tumour and lose their previous function. When these DNA changes tell the cells in the brain to infiltrate and destroy healthy brain tissue, it becomes brain cancer. These DNA mutations can be inherited from your parents or occur spontaneously during your lifetime.

The following factors can increase your risk of glioma:

• Age: gliomas are most common in adults between the ages of 45 and 65 years of age
• Exposure to radiation: studies have shown that individuals (especially children) who have been exposed to high-dose ionising radiation are at an increased risk of developing gliomas later on.⁴ Radiation therapy which is used to treat cancer is an example of ionising radiation
• Family history: some inherited genetic disorders may increase your risk of gliomas. Approximately 5% of gliomas occur in families with a history of glioma. Some of these are due to inherited disorders which lead to DNA mutations⁴ 

Signs and symptoms of glioma

The symptoms caused by the glioma depend on where it is located, and sometimes also the size, the type and how quickly the glioma is growing.

Common symptoms include the following:

• headaches, which are often worse in the morning and when coughing or straining
• problems with speaking and communicating
• vision problems, such as blurred vision, double vision or loss of peripheral vision
• confusion, memory loss or problems with thinking and understanding information 
• difficulty walking or keeping your balance
• dizziness
• one-sided weakness or numbness 
• nausea and vomiting
• personality or behavioural changes 
• seizures, especially if they haven’t had seizures before

Management and treatment for glioma

Your treatment plan for glioma will depend on several factors such as:

• the location, size and type of the tumour
• your age
• your health
• if you have already had previous treatment for brain cancer

For most people, surgery is the first treatment if it is possible. However, if the glioma is growing in an important or hard-to-reach area of the brain, it might be too risky to remove and then surgery is not an option. Other treatments, such as chemotherapy and radiation therapy may then be used as the primary treatment instead. 

If you have had surgery as the primary treatment, chemotherapy and radiation therapy are typically used as an additional treatment afterwards to destroy any remaining cancer cells or parts of the tumour which could not be removed.

Diagnosis

In order to make a diagnosis, your healthcare provider will use some of the following tests and procedures:

• a medical history and physical exam
• a neurological exam, which consists of a physical exam to assess your mental status, speech, hearing, strength, sensation, balance, coordination and reflexes.
• the doctor may check your eyes for papilledema. This is swelling of the optic discs in your eyes, caused by increased intracranial pressure. This swelling is a sign that requires immediate medical attention.  
• MRI and CT scans to look for tumours in the brain, as well as in other places in the body.
• a biopsy if an abnormal mass is found on the scans. Depending on where the tumour is located, the tumour's biopsy and removal may be performed simultaneously. If the doctor can’t do a biopsy, due to the tumour being in a difficult-to-remove location, they will diagnose the brain tumour and determine a treatment plan based on other test results.

Complications

It is important to seek prompt diagnosis and treatment if you are concerned as having a glioma can lead to potentially life-threatening complications. These include:

• brain haemorrhage (bleeding in the brain)
• brain herniation (brain tissue moves outside its normal position in the skull)
• hydrocephalus (excessive accumulation of fluid in your brain, which puts harmful pressure on the tissues of your brain)
• pressure inside your skull
• seizures

FAQs

How can I prevent glioma?

Gliomas usually can’t be prevented as they are due to spontaneous or inherited DNA mutations. If you have symptoms of glioma, visit your healthcare provider, as early diagnosis can prevent or slow down a low-grade glioma progressing to a high-grade glioma. If you have a family history of gliomas, you may wish to consider genetic testing. It may also be a good idea to limit exposure to ionising radiation and to maintain a healthy lifestyle.

How common is glioma?

Gliomas are the most common primary tumours in the brain. The incidence of gliomas is 4.67 to 5.73 per 100,000 people.²

Who is at risk of glioma?

The risk of glioma increases with age. Also, people assigned male at birth (AMAB) have a higher risk of most gliomas than those assigned female at birth (AFAB). People who have been exposed to ionising radiation are also at a higher risk of gliomas. Those with a family history of gliomas also have a higher risk of being diagnosed with gliomas themselves. 

When should I see a doctor?

If you are suffering from any new concerning symptoms, or if you have been suffering from symptoms for some time, you should make an appointment with your healthcare provider. Symptoms can vary depending on the type, size and location of the tumour. Symptoms can include headaches, vision, speech, memory or cognitive problems.

Summary

Gliomas are the most common primary tumours in the brain. The types of gliomas are determined by the type of glial cell they started in. They are categorised into 4 grades, from low to high depending on their malignancy. Glioblastomas are the most common type of grade IV glioma. Symptoms of gliomas vary depending on their location, their size and the type. The exact cause of gliomas is not clear, yet we know they are caused by mutations in DNA, which may be hereditary or due to spontaneous mutations during a person’s lifetime. There are certain risk factors which may increase a person’s chances of developing a glioma such as age, exposure to ionising radiation and a family history of gliomas. The primary treatment option, if possible, is usually surgery. Radiation therapy and chemotherapy can also be used as additional or alternative methods of treatment. The outlook for gliomas depends on tumour type, tumour grade, a person’s age, certain mutations, and also if it is a low-grade tumour early diagnosis and treatment.