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Low-Grade Glioma

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A diagnosis of low-grade glioma can be worrisome for both patients and caregivers. Currently available information on the Internet is confusing and at times contradictory. Herein, we will attempt to tackle many commonly asked questions to keep you informed and ease some of the burden of the unknown. Reliable information about brain tumors can empower patients and relieve some of their anxiety, therefore making informed decisions about their care a reality.

What Is a Low-Grade Glioma?

Glial cells are support cells of the brain. When they grow in an uncontrolled fashion, they can form tumors referred to broadly as gliomas. These are different types of glial cells that can grow throughout the central nervous system (brain and spinal cord). Low-grade gliomas are typically non-cancerous, although there are instances where these tumors can become more aggressive with time.

A diagnosis of low-grade glioma usually has a relatively good prognosis as compared to its more malignant counterparts and can often be treated when caught early.

How Are Gliomas Graded?

Saying something is "low-grade" does not help with your anxiety, frustration, or fear when you do not know what it means. Your doctor or oncologist may use these grades to help explain how invasive or fast growing a glioma appears to be under a microscope. Subtle changes in grading scales exist for different types of tumors based on their genetics. Generally, tumors with lower grades are less invasive, slow-growing and associated with a long survival. Examples of specific grades are provided here:

  • Grade I: This is the least invasive grade of tumor made up of slow-growing cells that often have high rates of survival.
  • Grade II: While Grade II tumors are also slow-growing, they can invade healthy tissues and become more invasive and aggressive over time.
  • Grade III: This level of tumor contains actively reproducing cells that can invade normal brain tissue.
  • Grade IV: At the highest level, these tumor cells are rapidly reproducing and developing into abnormally structured cells. Grade IV tumors often represent the most aggressive tumors or cancers.

Common Forms of Low-Grade Glioma

There are several different types of glial cells with the potential to form different types of tumors. Some show up more often than others and each brings their own challenges. Some even require different treatments. By knowing exactly which glioma you are dealing with, you can make an informed decision about your treatment.


This tumor originates from oligodendrocytes, a type of glial cell that forms the coating of nerve fibers to help them transmit signals faster. Oligodendrogliomas often form around these nerve fibers in the frontal or parietal lobes of the brain. Grade II oligodendrogliomas are considered low-grade, while Grade III oligodendrogliomas are considered high-grade.


When a tumor forms in certain glial cells responsible for protecting and supporting the nervous system (astrocytes), it is called an astrocytoma. They are usually found in the cerebrum or spinal cord. Astrocytomas can be considered low-grade. However, they can become more aggressive, as in the case of glioblastomas, which are the most aggressive type of astrocytoma. Grades I and II astrocytomas are considered low-grade.


The brain contains fluid-filled cavities called ventricles. Ventricles contain cerebrospinal fluid (CSF) and function to protect the brain and spinal cord. CSF is created by ependymal cells which are found along the walls of the ventricles. When these cells grow out of control, they can result in an ependymoma. These tumors can cause a number of symptoms, especially if they block the flow of CSF. Grade I and II ependymomas are considered low-grade gliomas, while Grade III ependymomas are high-grade.

                                            Figure 1: Different grades of gliomas on MRI. Left: High-grade glioma with evidence of enhancement (white-appearing tissue). Middle: Intermediate-grade glioma with slight enhancement. Right: Low-grade glioma without any enhancement.

Figure 1: Different grades of gliomas on MRI. Left: High-grade glioma with evidence of enhancement (white-appearing tissue). Middle: Intermediate-grade glioma with slight enhancement. Right: Low-grade glioma without any enhancement.

Key Takeaways

  • Receiving a diagnosis of a low-grade glioma is understandably troublesome for patients and caregivers alike.
  • Not all gliomas are created equal. Grading scales allow doctors to determine the nature of gliomas and may dictate prognoses and treatment options.
  • Low-grade gliomas generally have better outcomes than high-grade gliomas.
  • Regardless of whether you or a loved one has been diagnosed with a low-grade glioma, it is important to remain informed and aware of this information as it can help guide your treatment.
  • The experience of your surgeon can play an important role in the outcome of your treatment by providing a maximal safe resection of the tumor.