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In patients with progressive optic nerve sheath meningiomas, fractionated stereotactic radiotherapy is the standard of care and prevents further vision loss.
Dr. Savino discussed the case of an otherwise healthy 35-year-old woman with visual loss that had been slowly progressing over the previous several months. The patient was not taking any medications. The vision in the left eye, which had an afferent pupillary defect, had decreased to 20/70, and the disc was mildly swollen without hemorrhages or exudates.
The rule of thumb in neuro-ophthalmology, he explained, is that when confronted with a middle-aged woman with unilateral slowly progressive visual loss and a swollen optic nerve, the diagnosis is optic nerve sheath meningioma.
Optic nerve sheath meningiomas are rare and represent about 2% of all orbital tumors. The tumor occurs more frequently in women. The tumor is characterized by progressive visual loss, optic atrophy, and optochoroidal or optociliary shunt vessels seen on ophthalmoscopy.
"There are only several treatment options, the first of which is observation," Dr. Savino said. "However, almost all patients with an optic nerve sheath meningioma will go on to lose vision.
"A previous popular option was surgery, but it is no longer performed routinely because most of the patients became blind as a result of the surgery itself," he added. "Radiotherapy was later considered to be a viable treatment option."
Initially, radiotherapy for meningiomas was controversial because the tumors are slow growing and benign. This treatment was seen to be effective after some meningiomas of patients who were to undergo surgery were first irradiated and the radiation was seen to have an effect on the tumors.
"We know that radiation works in cases of meningiomas," Dr. Savino said.
In 1975, J. Lawton Smith, MD, presented his experience with radiation used to treat six cases of optic nerve sheath meningioma in the Journal of Clinical Neuro-ophthalmology. The vision was preserved in these cases.
In another study of patients with optic nerve sheath meningioma who were observed only or who were treated with surgery and radiation, those whose lesions were irradiated had the better visual outcome, Dr. Savino recounted.
Initially, standard radiation was used to treat these patients, but because of the associated complications, the visual outcomes were actually better for patients who had only been observed. When fractionated stereotactic radiotherapy began to be used, a large study that compared the results of standard radiation with those of fractionated stereotactic radiotherapy indicated that the results were better for the latter because of the limited treatment field and the decreased rate of complications compared with the early attempts.
Another study from Wills Eye Institute and Thomas Jefferson University, Philadelphia, showed that after 156 months of follow-up, fractionated stereotactic radiotherapy effectively prevented further vision loss, improved some of the visual loss, and, importantly, the complication rate was very low.
Dr. Savino recommended that if patients with optic nerve sheath meningioma are going to be treated, fractionated stereotactic radiotherapy should be used. The questions of who and when to treat remain when the following case is considered.