Optic Pathway Glioma

What is an optic pathway glioma?

An optic pathway glioma (OPG) is a term often used for a type of tumor that forms in the brain regions involved in vision (the visual system). These tumors are low-grade gliomas and are most often classified as pilocytic astrocytomas.

"Optic pathway glioma" is no longer the official term for this tumor, but it is still commonly used by doctors, patients, and their families.

OPGs in children grow slowly. But as the tumor grows, pressure on the optic nerve can cause vision problems. OPGs can also form near the pituitary gland and hypothalamus. Depending on the location, the tumor may affect hormone production.

OPGs make up 5% of all pediatric central nervous system (CNS) tumors. They are most common in young children and children with neurofibromatosis type 1 (NF1).

Treatment for an OPG depends on your child’s age, vision, NF1 status, and tumor location. Treatments may include surgery, chemotherapy, radiation therapy, and targeted therapy. Treatment is complex because the doctors want to avoid harming vision and endocrine function. Doctors may watch patients over time to see how their disease progresses.

Symptoms of optic pathway glioma

Symptoms of an OPG depend on:

• Child’s age and stage of development
• Tumor size
• Tumor location

OPG signs and symptoms may include:

• Vision and eye problems:
  • Vision loss
  • Decrease in color vision
  • Bulging eye, also called proptosis
  • Crossed eye, also called strabismus
  • Swelling or shrinking of the optic disc
  • Decrease in visual field or area of vision
• Head tilt
• Unusual eye movements
• Hormone disturbances that may cause change in appetite, weight, sleep, growth, or other endocrine problems

Risk factors for optic pathway glioma

Most OPGs occur in children under age 10. These tumors are closely linked to neurofibromatosis type 1 (NF1). About 20% (2 in 10) of children with NF1 may develop an OPG. It is important for children with NF1 to have regular eye exams.

Children with NF1 may have slow-growing tumors that can be followed with observation.

Diagnosis of optic pathway glioma

Doctors use several tests to diagnose optic pathway gliomas.

The doctor may do an eye exam to check visual function. This includes:

• Appearance of eye structures
• Sharpness of vision
• Visual field
• Color perception

Your child may have a neurological exam to measure brain function. This exam tests:

• Memory
• Vision
• Hearing
• Muscle strength
• Balance
• Coordination
• Reflexes

Other tests may include:

• A health history and physical exam
• Endocrine function tests, if the tumor is near the pituitary gland
• Imaging tests to help identify the tumor, see how big it is, and learn which areas of the brain it may affect. These tests could include: 
  • Magnetic resonance imaging (MRI)
  • Computed tomography (CT scan) 
• A biopsy when imaging and history are diagnostic

Stages of optic pathway glioma

Most OPGs in children are low grade. The cells of a low-grade tumor:

• Grow slowly
• Do not look much different from normal cells
• Are less likely to spread to other parts of the body

Rarely, OPGs in children may be high grade. High-grade tumors:

• Are more aggressive
• Grow quickly
• Can spread throughout the brain and spinal cord

Treatment of optic pathway glioma

There is no single treatment plan for OPG. Because these are usually low-grade tumors, preserving vision is a main concern. Treatment options include observation, surgery, targeted therapy, chemotherapy, and radiation.

The tumor needs to be tested to get the right diagnosis and find the best treatment. But if the tumor is in the nerve behind the eye, doctors must decide if it can be safely sampled or should be treated without a biopsy.

Therapies depend on:

• Age of the child
• How much vision was lost
• Tumor location and size
• Whether the child has NF1

Observation

Doctors monitor patients using eye exams and regular MRI scans.

If the disease worsens, the patient may have more vision problems, the tumor may grow larger, or the disease may spread.

Surgery

Surgery may be used to remove as much of the tumor as possible. But surgery alone may not provide a cure. In some cases, surgery is not possible due to the tumor’s location. Risks of surgery include worsening vision or harming nearby structures, including the hypothalamus (a part of the brain).

Targeted therapies

Studies show that most low-grade gliomas have specific mistakes in the tumor cells. These mistakes can usually be treated with special medicines called targeted therapies. Targeted therapies work by acting on, or targeting, specific features of tumor cells. In some tumors, there are changes in the genes and proteins that control tumor cell growth and division. Scientists are testing drugs to see if they can block the signals that cause certain cancer cells to grow.

Targeted therapies are changing how doctors treat optic pathway gliomas that cannot be completely removed. New medicines that target tumor cells have made the tumors shrink with fewer side effects than traditional chemotherapy or radiation. So, these targeted therapies are becoming the first choice for treating this disease.

Chemotherapy

Chemotherapy is often used to treat OPGs. It is used in younger patients to delay or avoid radiation therapy. It may also be used when surgery is not a good option or if surgery cannot remove the tumor completely. Not all tumors respond to chemotherapy.

Hearing loss may be a side effect of chemotherapy. Your care team will consider this risk when planning treatments. Patients with OPGs may have vision problems, so avoiding hearing loss is important.

No single chemotherapy plan is used for all OPGs. The medical team will figure out the best plan based on your child’s needs. The plan will depend on factors such as:

• The tumor’s location
• Symptoms
• Your child’s age

Some chemotherapy drugs used to treat OPG include vincristine, carboplatin, vinblastine, lomustine, and temozolomide.

Radiation therapy

Radiation therapy may be used for older children depending on the type of tumor and its location. In OPG, radiation therapy is the most effective treatment and helps preserve vision. But there is a risk of late effects, especially for younger patients. Learn more about clinical trials.

Prognosis for optic pathway glioma

The long-term survival rate for childhood OPG is high (above 90% or 9 in 10) in the United States. But treatment and management of these tumors is complex. Vision problems are common in survivors. Depending on the tumor location, endocrine function may also be affected.

A pediatric cancer care team will need to plan treatments. They will balance cure and quality of life. Every case is different. Ask your care provider for information about your child’s treatment and prognosis.

Prognosis depends on such factors as:

• Your child's age at diagnosis
• Type and grade of the tumor
• If the cancer has spread
• If surgery can completely remove the tumor
• Inherited conditions that increase risk, such as NF1
• Whether the cancer is new or has come back

Early diagnosis helps preserve vision and eye health.

Support for optic pathway glioma

Doctors use imaging tests and eye exams to monitor patients long-term. Follow-up care may include specialty areas such as rehabilitation, neurology, and endocrinology.

Eye health is important for survivors of OPGs. Your child should visit an ophthalmologist (eye doctor) at least once a year as part of routine health care. Many survivors have lifelong vision problems, and vision assistance may be needed. Low-vision specialists and school accommodations can help children adapt to vision loss. Protective eyeglasses can help prevent eye injury.

Questions to ask your care team

• What are our treatment options?
• What are the possible side effects of each treatment?
• What can be done to manage side effects?
• Will my child need to be in the hospital for treatment?
• Where is the treatment available? Is it close to home or will we have to travel?

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