Glioma - optic; Optic nerve glioma

Gliomas refer to a class of tumors that can be found in various parts of the brain. Optic gliomas are gliomas that affect part of the optic nerves (the nerves that carry visual information to the brain from the eyes) or the optic chiasm. The cause of optic glioma is unknown.

These tumors most often occur in children and almost always occur before age 20. Optic gliomas are rare. There is a strong association between optic glioma and neurofibromatosis Type 1 (NF1).

Symptoms are due to progressive growth of a mass that invades and presses on the optic nerve and adjacent structures:

• vision loss
  • one or both eyes
  • general decrease in vision, or a decrease in the visual fields (such as a loss of peripheral vision)
  • eventual blindness
• squinting
• involuntary movement of eyeball
• eye may bulge outward (painless proptosis)

A neurologic examination reveals a loss of vision in one or both eyes. There may be changes in the optic nerve, including swelling or scarring of the nerve or paleness and atrophy of the optic disk.

There may be extension of the tumor into deeper locations of the brain and signs of increased pressure within the brain (intracranial pressure). There may be signs of NF1.

• A head CT scan or MRI of the head confirms the diagnosis and the exact location of the tumor.
• Cerebral angiography is not often necessary, but if used, it shows a space-occupying mass which is not vascular.
• Visual field tests can help determine how invasive the tumor is
• An examination of tissue removed from the tumor during surgery or CT scan-guided biopsy is used to confirm the exact type of tumor.

Treatment varies with the size of the tumor and the general health of the person. The goal of treatment may be to cure the disorder, relieve symptoms, or improve vision or comfort.

Surgical removal may cure some optic gliomas. Partial removal to reduce some of the bulk of the tumor is feasible for many cases, which will minimize pressure-induced damage from the tumor.

Radiation therapy may be advised in some cases where the tumor is extensive and surgery is not possible. In some cases, the use of radiation may be delayed because of the slow growth that this tumor typically displays. Corticosteroids may be prescribed to reduce swelling and inflammation during radiation therapy, or if symptoms recur.

The outlook is highly variable. Early treatment improves the chance of a good outcome. Many tumors are curable with surgery, while others recur. Normally, the growth of the tumor is very slow, and the condition remains stable for long periods of time.

There are a small portion of these types of tumor that behave aggressively in about 20% of childhood cases where the optic chiasm is involved.

• decreased vision
• blindness