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Optic glioma

Definition

Gliomas are tumors that grow in various parts of the brain. Optic gliomas can affect:

• One or both of the optic nerves, which carry visual information to the brain from each eye
• The optic chiasm, the area where the optic nerves cross each other in front of the hypothalamus of the brain

An optic glioma may also grow along with a hypothalamic glioma.

Alternative Names

Glioma - optic; Optic nerve glioma

Causes, incidence, and risk factors

Optic gliomas are rare. The cause of optic gliomas is unknown. Most optic gliomas are slow-growing and noncancerous (benign) and occur in children, almost always before age 20.

There is a strong association between optic glioma and neurofibromatosis Type 1 (NF1).

Symptoms

The symptoms are due to the tumor growing and pressing on the optic nerve and nearby structures. Symptoms may include:

• Involuntary eyeball movement
• One or both eyes may bulge outward
• Squinting
• Vision loss in one or both eyes
  • Leads to eventual blindness
  • May be a loss of peripheral vision or vision loss may be more general

The patient may show symptoms of diencephalic syndrome, which includes delayed growth, loss of appetite and body fat, daytime sleeping and decreased memory and intellectual function.

Signs and tests

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 disc.

The tumor may extend into deeper locations of the brain. There may be signs of increased pressure within the brain (intracranial pressure). There may be signs of neurofibromatosis type 1 (NF1).

The following tests may be performed:

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

Treatment

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

Surgical removal may cure some optic gliomas. Partial removal to reduce the bulk of the tumor can be done in many cases. This will keep the tumor from damaging normal brain tissue around the tumor.

Radiation therapy may be advised in some cases where the tumor is larger and surgery is not possible. In some cases, radiation therapy 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 return.

Chemotherapy could be useful in a number of children. Chemotherapy might be especially useful when the tumor extends into the hypothalamus.

Support Groups

For organizations that provide support and additional information, see blindness resources.

Expectations (prognosis)

The outlook is highly variable. Early treatment improves the chance of a good outcome. Many tumors are curable with surgery, while others return.

Normally, the growth of the tumor is very slow, and the condition remains stable for long periods of time. However, in adults and some childhood cases where the optic chiasm is involved, the tumor behaves aggressively.

Complications

• Decreased vision
• Blindness

Calling your health care provider

Call your health care provider if you have any vision loss, painless bulging of your eye forward, or other symptoms of this condition.

Prevention

Genetic counseling may be advised for people with neurofibromatosis-1. Regular eye exams may allow early diagnosis of these tumors before they cause symptoms.

References

Karcioglu ZA, Haik BG. Eye, orbit, and adnexal structures. In: Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, McKenna WG, eds. Abeloff’s Clinical Oncology. 4th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2008:chap 71.