Optic glioma is a mass created by growth of abnormal cells, or uncontrolled proliferation of cells, in one optic nerve, both optic nerves, the optic chiasm or in conjunction with hypothalamic glioma.
Causes, incidence, and risk factors
Optic glioma is classified as an astrocytoma . Most are composed of low grade pilocytic astrocytes. Optic gliomas cause symptoms by invasion (pressure) and displacement (destruction) of normal optic nerve tissue. An early sign of the presence of an optic glioma is painless proptosis. They may also result in progressive loss of vision in one or both eyes. The cause of optic glioma is unknown. Tumors may occur at any age but the incidence is higher in children. Optic glioma and other astrocytomas are rare; however, astrocytomas in general are the most common primary brain tumors in adults. There is a strong association between optic glioma and neurofibromatosis Type 1 ( NF1 ).
Signs and tests
A neurologic examination reveals visual loss in one or both eyes, including visual field defects. There may be optic disc or nerve head changes in the optic nerve, including papilledema (swelling of the nerve), or paleness and atrophy of the optic disk. Gliosis (scarring) of the opptic nerve head may be seen on fundoscopic examination. There may be extension of the tumor into deeper locations of the brain and can cause 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. 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
Treatment varies with the size of the tumor and the general health of the person. Treatment goals may be cure of the disorder, relief of symptoms, improvement of functioning, or comfort. Surgical excision (removal) is curative for some optic gliomas. Partial resection to remove some of the bulk of the tumor is feasible for many cases, which will reduce pressure-induced damage from the tumor. Radiation therapy may be advised in some cases where the tumor is extensive and surgical resection is not possible. In some cases it 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 when symptoms recur.
Support groups
The stress of illness can often be helped by joining a support group where members share common experiences and problems. See blindness - support group and cancer - support group .
Expectations (prognosis)
The probable outcome is highly variable. Early treatment improves the chance of a good outcome. Some 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.
Calling your health care provider
Call your health care provider if vision loss occurs or you note a painless bulging of your eye forwards (proptosis).
Prevention
Genetic counseling may be advised for people with neurofibromatosis-1 .