Optic Pathway Glioma
Like many brain tumour types, the exact cause of an optic pathway glioma is unknown. However, optic pathway gliomas are associated with neurofibromatosis type 1 (NF-1), also called Von Recklinhausen’s disease.
- 20% of children with neurofibromatosis (NF-1) will develop an optic glioma.
- These gliomas are typically grade I pilocytic astrocytomas.
- Children with optic glioma are usually screened for NF-1 for this reason.
- Adults with NF-1 typically do not develop optic gliomas.
This tumour type is named for its location on or near the optic nerve pathways between the eyes and the brain. These tumours may involve any part of the optic pathway and have the potential to spread along these pathways.
Common symptoms include, but are not necessarily limited to:
- Behavioural disturbance
- Clumsy, uncoordinated walk
- Developmental delay(s), or early puberty due to hormonal disturbance
- Double vision, also called strabismus (crossed eyes)
- Failure to thrive in very young children
- Visual disturbance/loss (children may fall or bump into things more easily because of this symptom and may not complain directly that their vision has changed)
Treatment/Standard of Care
The treatment of an OPG depends very much on the location and extent of the tumour. Not all patients with identifiable optic pathway gliomas on imaging ever have visual symptoms (especially if the patient has NF-1).
Spontaneous regression of these tumours has been documented (in patients with and without NF-1).
In many patients with mild symptoms, observation alone may be recommended because:
- Symptoms are mild and there is no immediate threat to vision.
- The natural history of disease is most likely very slow (as with patients with NF-1).
- The patient is young and the aim is to reduce the risk of treatment-related morbidity.
Surgical treatment for OPG may involve either biopsy or excision of the tumour. Surgery is usually the first choice when:
- Single nerve involvement is causing progressive disfiguring proptosis (bulging out of the eye) and blindness.
- An exophytic tumour involving the optic chiasm is causing mass effect or hydrocephalus (raised intracranial pressure).
Chemotherapy has the ability to shrink OPG and may even stabilize the tumour. This treatment is often given to very young children to delay giving radiation therapy and avoid damage to the developing brain.
Moderately high-dose radiation therapy can be used to control these tumours. Different techniques can be used to spare surrounding normal structures such as stereotactic radiation therapy.