What is a brainstem glioma?
Brainstem gliomas make up approximately 10-20% of all central nervous system tumors of childhood. They typically occur in children less than 10 years of age. Brainstem gliomas arise from glial cells within the brain stem. Glial cells are a type of support tissue cell. The behavior, treatment and prognosis of a brainstem glioma are determined by where it is located within the brainstem (midbrain, pons, medulla), how it grows within the brainstem (diffuse or focal and intrinsic or exophytic), and the type of glioma (low grade or high grade). The brainstem is composed of three main parts: midbrain, pons and medulla. Brainstem gliomas can arise in any area of the brainstem, but the pons is the most common location making up 75-85% of brainstem tumor. Brainstem gliomas typically grow in a diffuse fashion among the normal cells within the brainstem, making it impossible to remove the tumor without injuring the normal brainstem. These tumors are termed “diffuse intrinsic”, have a more aggressive pathology (high grade), and have a poor prognosis. Diffuse intrinsic brainstem tumors commonly arise within the pons and rarely within the medulla. Some brainstem gliomas develop within the brainstem (intrinsic) but grow in a focal fashion and are termed “focal intrinsic” brainstem gliomas. Focal intrinsic brainstem gliomas are typically located in the medulla or midbrain. Focal brainstem gliomas can also develop in an exophytic fashion (i.e. growing from the edge of the brainstem with the majority of the tumor protruding outside of the brainstem). Focal intrinsic and exophytic brainstem gliomas tend to have a less aggressive pathology (low grade), can often be surgically removed, are typically responsive to chemotherapy and radiation therapy, and usually have a good prognosis.
Common brainstem gliomas include Tectal Glioma, Diffuse Intrinsic Pontine Glioma (DIPG), and Cervicomedullary Glioma.
What are the symptoms of a brainstem glioma?
The brainstem is where the nerves that control motor and sensation of the head and neck arise. The brainstem also contains nerve fibers that travel from the brain to the spinal cord to control the movement, coordination and sensation of the body. Lastly, the brainstem plays an important role in the regulation of cardiac and respiratory function. Brainstem gliomas interfere with the function of the surrounding nerve fibers resulting in symptoms. Tumors located within the brainstem can also block the flow of spinal fluid resulting in hydrocephalus and symptoms of increased intracranial pressure (headache, vomiting, poor balance and decreased level of consciousness).
Symptoms of a brainstem glioma are determined by where it is located within the brainstem and the rate at which it is growing:
- Midbrain brainstem gliomas can cause hydrocephalus, upward gaze weakness and rarely weakness of one side of the body.
- Pontine gliomas typically cause multiple different facial nerve weakness involving one or both sides of the face (uncoordinated eye movements, facial weakness, numbness of the face, slurred speech, swallowing dysfunction), weakness of the arms and legs and poor balance. Because these tumors are fast growing the symptoms tend to come on quickly over a one-month period of time.
- Medullary brainstem gliomas cause hydrocephalus (headache, vomiting, poor balance and decreased level of consciousness) if there is an exophytic component.
- Diffuse medullary gliomas cause swallowing dysfunction, weakness of the arms and legs, and poor balance.
- Cervicomedullary tumor results in slurred speech, swallowing dysfunction, vomiting, weakness of one side of the body, abnormal breathing and a preference to turn or tilt the head to one side.
How is a brainstem glioma diagnosed?
The diagnosis of a brainstem glioma is made through an MRI scan. Many brainstem gliomas can be diagnosed based on the symptoms and MRI without need tumor tissue (i.e. tectal gliomas, diffuse medullary gliomas, diffuse intrinsic pontine gliomas). Focal or exophytic brainstem gliomas typically undergo surgical removal, which provides tumor tissue to confirm the pathology. Some cases of diffuse brainstem tumors undergo biopsy to confirm the diagnosis.
How is a brainstem glioma treated?
The brainstem contains vital structures. Diffuse brainstem tumors cannot be surgically removed without causing unacceptable side effects. Focal or exophytic gliomas can often be completely or near completely surgically removed depending on how intimately the tumor is associated with the surrounding normal brainstem.
Tectal Glioma: Tectal gliomas are a type of midbrain glioma. These tumors are usually very small (less than 1-2 cm), are extremely low grade, and usually remain quiet throughout the individual’s life. Tectal gliomas typically cause hydrocephalus, requiring placement of a ventriculoperitoneal shunt (VP shunt) or a 3rd floor ventriculostomy. It is unusual for tectal gliomas to require any further treatment due to their indolent nature.
Focal Intrinsic or Exophytic Brainstem Glioma: These tumors are low grade and slow growing. The first treatment is typically surgical removal if possible. Surgery can be curative if all or the majority of the tumor is removed. Chemotherapy and radiation therapy can be effective treatments for cases where surgery is not an option or in cases where the tumor grows back.
Diffuse Intrinsic Medullary or Pontine Gliomas: These tumors can never be surgically removed. The diagnosis can be made from an MRI but sometimes a biopsy is recommended to confirm the aggressiveness of the tumor. Radiation therapy is recommended to temporarily stop the tumor from growing, although it is rarely curative. Chemotherapy has not been shown to improve outcome. Many studies are underway to better understand the biology of diffuse brainstem gliomas and to find better treatments.
About treatment for brainstem glioma at Children’s Minnesota
Our cancer and blood disorders program consistently achieves excellent results ranking it in the top ten programs in the United States. Children’s Minnesota treats the majority of children with cancer and blood disorders in Minnesota and provides patients access to a variety of clinical trials using ground-breaking new treatments. Through our renowned program, patients experience unparalleled family support, a nationally recognized pain management team, and compassionate, coordinated care.
If you are a family member looking for a Children’s neuro-oncologist, please call our clinic at 612-813-5940.
If you are a health professional looking for consultation or referral information, please call Children’s Physician Access at 1-866-755-2121 (toll-free) and ask for the on-call hematologist/oncologist.
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