A glioma is the umbrella term for the various brain tumors that can arise from glial cells, the cells that help support neurons (or nerve cells) in the brain. Although gliomas can occur in adults, they are the most commonly diagnosed brain tumors in children.

Gliomas are classified as low- or high-grade. Low-grade gliomas are slow-growing and sometimes don’t impact a person’s overall health. However, some low-grade gliomas can eventually become high-grade ones. High-grade gliomas grow quickly, leading to significant dysfunction and even death. When a person has a glioma, its location determines its severity and what kinds of problems can develop.

Aggressive treatment and close monitoring with regular follow-up appointments, particularly for patients with a high-grade glioma, can help to extend life and even improve their chance of survival.

Glioma is a catchall category of brain tumor, encompassing the several types of tumors that involve glial cells within the brain. High-grade gliomas are more serious and life-threatening than low-grade gliomas, though these can evolve into high-grade gliomas over time.

Certain genetic mutations that increase the risk of glioma can impact a glial cell’s “on/off” switch, affecting its ability to reproduce. As a result, the cells may continually reproduce because they don’t get the message to stop. When these cells multiply uncontrollably, the resulting mass of cells can form a glioma.

There are several different types and families of gliomas. Depending on their aggressiveness, the tumors are graded from 1 to 4, with 4 being the most aggressive. In adults, the most common family is known as infiltrative gliomas, because they cannot be entirely removed with surgery. Examples of this family are:

• Glioblastoma, a high-grade, fast-growing glioma that spreads quickly into surrounding healthy brain tissue. It is typically diagnosed in adults and is by far the most common form of glioma. They are grade 4 tumors.
• Oligodendroglioma, a tumor that develops from glial cells known as oligodendrocytes. It is characterized by the presence of a mutation in genes, such as IDH-1 or IDH-2, and a chromosomal abnormality called 1p/19q codeletion. This tumor type is less aggressive that the other gliomas and tends to respond better to chemotherapy and radiotherapy. They can present as grade 3 or 4 tumors.
• Astrocytoma is also a tumor characterized by a mutation in the IDH-1 or IDH-2 gene but does not display the 1p/19q codeletion. It is less aggressive than glioblastoma, but more aggressive than oligodendroglioma. It can present as grades 2, 3 or 4 tumors.

In children, many other families of gliomas have been characterized. The most benign tumors in children are those that present as grade 1, such as pilocytic astrocytoma. These tumors can be potentially cured with surgery. Other pediatric tumors can be more aggressive and present as grade 4 gliomas.

Gliomas often form in the brain’s frontal, temporal, parietal, or occipital lobe, but they can also form in the cerebellum, brain stem, optic nerve, or even on the spinal cord.

Doctors aren’t sure why some people develop gliomas. In a small group of patients, the tumor is related to certain genetically inherited conditions. They include:

• Neurofibromatosis type 1
• Tuberous sclerosis
• Li-Fraumeni syndrome
• Lynch syndrome
• Familial adenomatous polyposis

Additionally, people who have previously had radiation therapy to the head or neck for a different type of cancer may develop a glioma.

Symptoms of a glioma can include:

• Headaches
• Behavior changes
• Nausea
• Vomiting
• Double vision
• Muscle weakness
• Trouble swallowing
• Paralysis on one side of the body or in one limb
• Loss of sensation on one side of the body
• Inability to speak or understand speech
• Memory impairment
• Cognitive difficulties
• Seizures

Babies with a glioma may experience:

• Irritability
• Gradual increase in head size, due to hydrocephalus
• Loss of appetite
• Failure to thrive

People with gliomas don’t always have noticeable symptoms early on, and the tumor can be found incidentally. Diagnosis and treatment can be delayed for young children whose symptoms may be present but don’t have communication skills to describe what they are feeling.

Doctors can diagnose glioma after learning about a patient’s medical history, performing a physical exam, and offering diagnostic tests.

When learning about a patient’s medical history, doctors will ask patients (or children’s parents) if they have previously had radiation therapy to the head and neck. They may also ask about a family history of certain inherited conditions, like neurofibromatosis type 1 or inherited genetic mutations.

During a physical examination, a neurological exam and cognitive test will be performed to determine a patient’s abilities and deficiencies. Doctors will look for signs of muscle weakness or hydrocephalus.

In addition, imaging tests, such as MRI, CT scan, PET scan, or Functional MRI (fMRI), may be used to help diagnose a glioma.

However, if doctors suspect a glioma, a biopsy or surgical resection must be performed to confirm the diagnosis.

There are many treatment options for glioma, including:

• Watchful waiting. Some doctors recommend “watchful waiting” for certain types of low-grade gliomas that don’t interfere with a patient’s daily functioning or quality of life.
• Surgery is the preferred treatment for glioma. Removing the entire tumor helps improve a patient’s chance of survival, particularly when a patient has high-grade glioma. However, many gliomas cannot be completely removed because they spread into, and intertwine with, healthy brain tissue. Sometimes, the glioma may be too close to an essential part of the brain (such as the brain stem or structures that control motor function) for doctors to remove the entire tumor.
  
  After surgery, patients might also require radiation therapy and/or chemotherapy, depending on the type of glioma. If a glioma is found in an inoperable location, doctors may treat it directly with radiation and/or chemotherapy.
• Radiation therapy is an effective treatment for many types of glioma. It is often used after surgery, with or without chemotherapy. In some cases, radiation therapy may be given before surgery. When a glioma is inoperable, radiation therapy is often the recommended treatment.
• Chemotherapy. In most cases, chemotherapy alone isn’t as effective against glioma as other treatments. However, chemotherapy after surgery, combined with radiation therapy, can be more effective than surgery plus radiation therapy without chemotherapy. For some patients, targeted therapies specifically developed for the mutations found in their tumors may be available.

The outcome for an individual with a glioma depends on the type of tumor and its grade. Early diagnosis and treatment often help to improve survival rates. High-grade glioma outcomes are not as positive as low-grade glioma ones. For example, 95% of children with low-grade gliomas survive 5 or more years after diagnosis, but fewer than 10% of children with high-grade gliomas survive 5 or more years.

Glioblastomas are particularly difficult-to-treat tumors, and many patients choose to pursue clinical trials to gain access to the latest treatment developments.

“At Yale, highly specialized physicians and surgeons with extensive expertise treat hundreds of patients with glioma each year,” says Antonio Omuro, MD, chief of the Division of Neuro-Oncology and Director of the Yale Brain Tumor Center. “The patients benefit from state-of-the-art infrastructure, including top surgical facilities and techniques, neuroimaging, and radiation therapy equipment. All patients operated at Yale facilities have their tumor molecularly characterized with the latest gene sequencing technologies to individualize and guide treatment choices. Cutting-edge clinical trials are routinely offered, bringing hope to those patients with the most aggressive tumors and limited standard treatment options.”