Gliomas are tumors that grow in various parts of the brain. The term ‘optic’ relates to conditions related to eyes.
Optic gliomas are gliomas that can affect different parts of the eye, mainly in one or both of the optic nerves that carry visual information to the brain from each eye, and the optic chiasm, the area where the optic nerves cross each other in front of the hypothalamus area of the brain, when it grows along with a hypothalamic glioma.
Fortunately, optic gliomas are rare, and the cause is unknown. Most optic gliomas are slow-growing and benign (non-cancerous) and occur in children, almost always before the age of 10.In rare cases malignant (cancerous) optic gliomas are seen and almost always have a poor outcomes Optic gliomas can occur in 30% of children with neurofibromatosis Type 1, where tumors occur on the skin along nerves of the skin, brain and other parts of the body, with distinct skin color changes. Neurofibromatosis related gliomas are associated with a favorable outcome.
Optic gliomas cause visual disturbances only when they grow and press the optic nerve or other structures that are located nearby. Patients may show some visual loss in either one eye or both eyes, which may start towards outer field and often goes unnoticed by the person. This can lead to an irreversible blindness gradually. Sometimes involuntary eyeball movement, outward bulging of one or both eyes, and squinting becomes obvious. It is better to examine a child thoroughly who sleeps too much, has reduced memory and brain function, delayed milestones and does not feed well (loss of appetite), or whose skin shows areas of discoloration.
A detailed neurologic (brain and nervous system) and eye examination, including visual field tests, will reveal a loss of vision in one or both eyes. The changes in the optic nerve, if any, including swelling or scarring of the nerve, or paleness and damage to the optic disc. Brain MRI imaging with contrast can confirm the location and extent, and a tissue biopsy guided by CT scanning can confirm the tumor type. It may not be possible to have a biopsy in all cases especially, if the glioma is encircling the nerve.
Treatment varies with the size of the tumor and the symptoms present in each patient to cure the disorder, relieve symptoms, or improve vision and comfort. Surgery can cure some optic gliomas and a partial removal to reduce the size of the tumor to prevent damaging normal neural tissue around it. The role of radiation therapy is important in cases where surgery cannot be done or only partial removal has been done. Corticosteroids may be prescribed to reduce swelling and inflammation during radiation therapy, or if symptoms return.
The present day technical advances of VMAT (Volumetric Modulated Radio Therapy) and IMRT (Intensity modulated Radio Therapy) with daily in –room Image Guidance (IGRT) have made it possible to give growth restraint radiation to the gliomas without compromising the neural pathways.
Normally, the growth of the tumor is very slow, and the condition remains stable for long periods. However, the tumor can continue to grow, so it must be monitored closely with regular eye and imaging examinations. Genetic counseling may be advised if NF1 (Neurofibromatosis) is present.