An optic nerve glioma is a type of noncancerous, slow-growing tumor that develops in the glial cells of the optic nerve. They are most common in children. Doctors may refer to this type of tumor as pilocytic astrocytoma.
Optic nerve gliomas develop anywhere between the optic nerve head next to the retina and the optic chiasm, where the left and right optic nerves partially cross. The optic nerves transmit visual signals from the eye to the brain.
Optic nerve glioma is rare, accounting for only 5% of all childhood brain tumors. They are most common in children
This article lists the symptoms to look out for with an optic nerve glioma. It also explains how a doctor will diagnose the condition and the possible treatments they may recommend.
Symptoms of optic nerve glioma depend on the location of the tumor.
Proptosis
Proptosis is when the eyes seem to protrude slightly from the head. This happens because the eye moves forward in response to the growing tumor and the eyelids appear retracted.
This is the most common sign of optic nerve glioma, presenting in
A person may also find it challenging to move their eye within the socket. However, this is more common when the tumor is in the orbit — the space where the eyeball sits within a person’s skull.
Vision loss
As a tumor grows, it presses against the optic nerve. This can cause changes to vision and loss of visual clarity.
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Other symptoms
Optic nerve glioma will resemble common medical changes in children, such as needing glasses to correct vision.
Other symptoms a person may experience include:
- difficulty reading
- worsening vision
- double vision
- blind spots
- flickering eyes
- squinting
- head tilt
- headaches
- nausea
- vomiting
- lethargy
- irritability
These tumors develop at the base of the brain, which is where hormonal control occurs. This can affect development in children.
For example, a 2020 article notes that optic gliomas can affect precocious puberty.
This can include the development of breast buds before the age of 8 years in girls and a testicular volume of more than 4 millimeters before the age of 9 years in boys. Weight changes can also indicate hormonal disruption.
As with many types of brain tumors, the exact cause of optic nerve gliomas is unknown. However, it has strong associations with a condition called neurofibromatosis 1 (NF1).
NF1 is a genetic condition. It causes tumors to develop along the nerves. The gene that causes this condition overproduces the substance neurofibromin, which helps regulate cell growth.
Optic nerve gliomas develop in approximately 15% of children with NF1. Most of the time, the tumors stop growing and slowly disappear without treatment.
Optic nerve gliomas develop specifically on and around the tissues that make up the central nervous system.
Initially, a doctor will typically perform or order the following tests:
- A complete physical assessment: This will include measuring weight and height.
- Hormone testing: This allows a doctor to check if a tumor is pressing on a child’s hypothalamus or pituitary gland, both parts of the brain important for regulating hormone release. This typically involves routine blood tests.
- Comprehensive eye examination: The eye doctor can see changes inside the eye that correlate with optic nerve glioma. Additionally, there are many helpful eye findings that allow them to confirm whether NF1 is present. If a child receives treatment for vision changes relating to optic nerve glioma, they may require vision testing throughout the treatment process and after treatment. This is to assess how they are responding to the treatment and if their symptoms are improving.
A doctor will also use a range of imaging tests to look for structural abnormalities around the optic nerve. These tests can include MRI and CT scans.
Treatment will vary depending on the individual’s needs. A team of doctors, including neuro-ophthalmologists, will determine the best route for treatment. Neuro-ophthalmologists are doctors who specialize in the part of the brain responsible for vision.
Factors that determine the most suitable treatment include:
- a medical history, including whether the individual has NF1
- the severity of the condition
- the location of the tumor
- the size of the tumor
- rate of tumor growth
Undergoing treatment for a tumor, whether benign or malignant, that affects the visual pathways can be stressful and may have lasting effects.
A person can speak with their doctor about how to reduce any side effects.
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Surgery
If a person experiences severe proptosis and vision loss, a healthcare professional may consider surgery to remove the tumor.
Chemotherapy and radiotherapy
Depending on where the tumor is, chemotherapy may be an option.
Chemotherapy for optic nerve glioma has a high success rate, with over 70% of people seeing no tumor growth after treatment. However, doctors are unable to recommend chemotherapy to children with NF1.
Children with an optic nerve glioma have a survival rate of nearly 90%.
Treatment typically resolves any vision problems. This is because the pressure on the optic nerve releases when the tumor shrinks, allowing it to regain typical function.
Children who develop optic nerve glioma secondarily to a diagnosis of NF1 are more likely to have no symptoms than those who develop optic nerve glioma spontaneously.
While rare, optic nerve glioma can occur in adulthood but is typically malignant. If this occurs, the outlook is
Optic nerve glioma can occur by itself or secondarily to NF1.
It is most common in children
Treatment typically involves watchful waiting unless it causes symptoms of pain or impaired vision. The outlook depends on individual circumstances.