Brainstem Glioma

Brainstem gliomas usually belong to the group of tumors known as astrocytoma, one of the most common types of brain tumor that can develop in children. Astrocytoma arises from a specific type of cell in the brain, called an astrocyte.

Brainstem gliomas are divided into subgroups based on their grade. The grade is determined by what the tumor tissue looks like under the microscope. In general, the lower a tumor's grade, the less aggressive its behavior. Brainstem gliomas can be grade 1, 2, 3 or 4 tumors.

Grade 2 astrocytomas in the brainstem frequently grow much faster than grade 2 tumors in the rest of the brain, and can transform into a higher-grade tumor. Grade 3 and grade 4 astrocytomas grow very fast, particularly in the brainstem. The reason for the very rapid growth of these tumors in this particular area of the brain is still unknown.

Because many brainstem tumors are not biopsied, a diagnosis is usually made based on the tumor's appearance on an MRI scan. Most tumors that arise from the brainstem region, other than proven grade 1 tumors, are considered highly malignant.

Boys and girls are equally affected by brainstem gliomas, most often between 5 and 10 years of age. Patients usually experience sudden onset of symptoms, over a period of days or weeks.

Typical symptoms of a brainstem glioma can include:

  • Abnormalities in eye movement
  • Weakness of one side of the face
  • Numbness or weakness of the extremities
  • Difficulty with balance
  • Headaches
  • Possibly nausea

Brainstem gliomas are typically diagnosed when symptoms related to cranial nerve dysfunction — such as double vision and difficulty speaking or swallowing — lead to an imaging study. An MRI of the brain will show a mass within the brainstem. Often, the MRI is all that is needed to diagnose a brainstem glioma.

In some cases, the tumor does not have the typical appearance of most brainstem gliomas, and a neurosurgeon will discuss the option to remove the tumor surgically or, at a minimum, perform a biopsy. In recent years, brainstem lesions are biopsied much more frequently, both to confirm the diagnosis and to obtain tumor tissue for molecular analysis that may someday aid in treatment decisions.

Surgery alone can often cure grade 1 brainstem gliomas. If surgery cannot remove most of the visible tumor, radiation therapy is very effective.

Unfortunately, the majority of brainstem gliomas are rapidly growing grade 3 or grade 4 astrocytoma, and even grade 2 tumors grow quickly. Because the tumor grows directly in the brainstem, in an area called the pons, surgery to remove the tumor is not possible. This area of the brain controls many vital functions necessary for survival, including breathing, heart rate and blood pressure.

At the same time, if the tumor continues to grow, those functions can be affected by the tumor itself. For this reason, treatment is started as quickly as possible. If the treatment does not control tumor growth, problems with breathing, heart rate, blood pressure and other neurologic deficits will eventually develop.

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Reviewed by health care specialists at UCSF Benioff Children's Hospital.

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