Glioma is a type of tumor that develops in the brain or spinal cord from cells that normally support and protect the nervous system. These tumors vary widely in how quickly they grow and how serious they are, ranging from slow-growing forms that may be manageable for years to aggressive types that progress rapidly and pose significant challenges to treatment.
Understanding Glioma: What Happens Inside the Brain
Glioma forms when glial cells, which are the supportive cells in the brain and spinal cord, begin to grow out of control. These glial cells normally have essential roles in helping nerve cells function properly. They surround nerve cells and provide structure and support to the entire central nervous system. When these cells multiply uncontrollably, they form a mass called a tumor.[1][2]
The tumor can press against brain or spinal cord tissue, interfering with normal function. Because the brain controls thinking, movement, sensation, and every other function of the body, a glioma can affect different aspects of daily life depending on where it develops. Some gliomas grow slowly and are not considered cancerous, while others are malignant, meaning they grow quickly and can invade healthy brain tissue.[1]
Healthcare providers classify gliomas by examining the type of glial cell they originate from and how quickly they grow. There are several types of glial cells, including astrocytes, which are star-shaped cells, oligodendrocytes, and ependymal cells. Each type plays a unique role in the brain, and the type of glial cell involved determines the specific name of the glioma.[2][6]
How Common Are Gliomas?
Gliomas are the most common type of primary brain tumor in adults, meaning they start directly in the brain rather than spreading from another part of the body. In the United States, approximately six cases of glioma are diagnosed per 100,000 people every year.[3] These tumors represent about 30 percent of all brain and central nervous system tumors, and they account for 80 percent of all malignant brain tumors.[8]
Gliomas can affect people of all ages, but they are most common in two groups: adults over the age of 65 and children under the age of 12.[2][10] The incidence of these tumors has increased slightly over the past two decades, especially among elderly individuals. Men are affected about 40 percent more often than women, and gliomas occur twice as frequently in white populations compared to Black populations.[12]
Among different types of gliomas, glioblastoma, which is the most aggressive form, accounts for approximately 60 to 70 percent of all malignant gliomas. Anaplastic astrocytomas represent 10 to 15 percent, while oligodendrogliomas and mixed gliomas make up about 10 percent of cases.[3][12]
What Causes Gliomas?
Genetic changes in glial cells cause gliomas to form. These are permanent changes in the DNA of the cells that make them grow and divide uncontrollably. However, healthcare providers do not always understand why these genetic changes occur in the first place. In most cases, gliomas develop without a clear or obvious cause.[2][10]
The only well-established environmental cause of gliomas is exposure to ionizing radiation. This includes radiation from medical treatments, such as radiation therapy used to treat other cancers, as well as radiation emitted by diagnostic imaging tests like CT scans. Studies have shown that there is a relationship between low-dose ionizing radiation and the risk of developing glioma, with risk increasing by about 55 percent for every 100 milligray of radiation exposure.[8][12]
Certain hereditary disorders can also predispose individuals to developing gliomas. Genetic syndromes such as neurofibromatosis and tuberous sclerosis complex are known to increase the risk. These are inherited conditions that run in biological families and affect how cells grow and divide.[8]
Who Is at Greater Risk?
Anyone can develop a glioma, but certain factors may increase the likelihood. Age is one of the most significant risk factors. Gliomas are most common in adults after age 65, though they can also occur in children, particularly those under 12 years of age.[2][10]
Family history plays a role as well. Some genetic disorders that can be inherited from biological parents increase the risk of developing gliomas. If close relatives have had brain or spinal cord tumors, the risk may be slightly higher, though most gliomas are not clearly linked to family history.[2][10]
Race is another factor. People who are white appear to be more likely to develop gliomas compared to other racial groups.[2][10] Repeated exposure to radiation or certain chemicals may also increase risk. This includes both medical radiation and occupational exposure to specific toxins.[2][10]
There has been concern about whether electromagnetic radiation from cell phones might cause gliomas. However, several large studies have not found conclusive evidence linking cell phone use to brain tumors. Research continues, but current evidence does not confirm a relationship.[8]
Interestingly, some research suggests that people with allergies or elevated levels of a certain antibody called IgE may have a reduced risk of developing gliomas. This suggests that immune system factors might play a protective role, though the exact reasons are not yet fully understood.[12]
Recognizing the Symptoms
The symptoms of glioma depend largely on where the tumor is located in the brain or spinal cord and how large it has grown. Because different parts of the brain control different functions, a tumor in one area can cause very different symptoms than a tumor in another area. Symptoms also depend on the type of glioma, its size, and how quickly it is growing.[1]
Headaches are among the most common symptoms of glioma, particularly headaches that are worst in the morning. These headaches occur because the tumor increases pressure inside the skull. As the brain is enclosed in a rigid skull, any extra mass creates pressure that can cause pain.[1][8]
Nausea and vomiting often accompany the headaches, also due to increased pressure within the skull. People with glioma may also experience confusion or a decline in brain function. This can show up as problems with thinking, understanding information, or remembering things. Personality changes or irritability may occur, and these changes can be distressing for both the person affected and their loved ones.[1][2]
Vision problems are another common symptom. These can include blurred vision, double vision, or sudden vision loss. If the glioma affects the optic nerve or areas of the brain involved in processing visual information, these problems can be particularly pronounced.[1][2][8]
Seizures are a significant symptom of glioma and can be the first sign that something is wrong. Seizures occur when abnormal electrical activity spreads through the brain. They can vary in severity, from brief moments of confusion to full convulsions.[2][8]
Other symptoms include difficulty walking or keeping balance, dizziness, new depression or anxiety, trouble speaking or communicating, and weakness or numbness on one side of the body. When gliomas affect the spinal cord, they can cause pain, weakness, or numbness in the arms, legs, hands, or feet.[2][8]
In children with a specific type called pontine glioma, which affects the brainstem, symptoms may include abnormalities in the function of certain nerves that control facial movement and swallowing, unsteady walking due to muscle stiffness, and behavioral changes.[8]
Can Gliomas Be Prevented?
Unfortunately, there is no proven way to prevent gliomas because their exact causes are not fully understood. Since most gliomas develop without a clear environmental or behavioral cause, specific prevention strategies are limited. However, reducing unnecessary exposure to ionizing radiation, such as limiting non-essential medical imaging tests that use radiation, may theoretically reduce risk.[8]
For individuals with a family history of brain tumors or known genetic syndromes that increase risk, genetic counseling and regular monitoring may be beneficial. While this does not prevent gliomas, it can help with early detection if a tumor does develop.[2][10]
Staying informed about symptoms and seeking medical care early if warning signs appear may improve outcomes. While this is not prevention in the traditional sense, early diagnosis can lead to earlier treatment, which may slow disease progression or improve quality of life.[2][10]
How Gliomas Affect the Body
Gliomas disrupt normal brain and spinal cord function in several ways. The most direct effect is through physical pressure. As the tumor grows, it takes up space within the skull or spinal canal, both of which are rigid structures that cannot expand. This leads to increased pressure on surrounding brain tissue, blood vessels, and nerves.[1][8]
High-grade gliomas, which are more aggressive, can invade and infiltrate healthy brain tissue. Unlike some tumors that grow in a well-defined lump, many gliomas are diffuse, meaning they spread into the surrounding tissue without clear boundaries. This makes them difficult to remove completely with surgery and allows them to continue growing even after treatment.[1][5]
Gliomas can also disrupt the normal chemical and electrical activity of the brain. Nerve cells communicate using electrical signals and chemical messengers. When a tumor interferes with this communication, it can cause seizures, cognitive problems, and other neurological symptoms.[8]
Another important aspect of glioma growth is how it affects blood flow in the brain. Some gliomas stimulate the formation of new blood vessels to supply the tumor with nutrients and oxygen. This process, called angiogenesis, supports tumor growth but also contributes to swelling and increased pressure in the brain.[3]
Gliomas generally do not spread to other parts of the body through the bloodstream, which is different from many other types of cancer. However, they can spread through the cerebrospinal fluid, the fluid that surrounds the brain and spinal cord. This can lead to “drop metastases,” where tumor cells spread down to the spinal cord.[8]
The location of the glioma within the brain determines which functions are affected. For example, a tumor in the area that controls movement can cause weakness or paralysis on one side of the body. A tumor in the area responsible for language can cause difficulty speaking or understanding words. Tumors in the visual areas of the brain can lead to vision loss or hallucinations.[1][8]
