Chiasmal optic glioma after radiation therapy. Neuro-ophthalmologic/pathologic correlation

A 16-year-old white girl with neurofibromatosis was documented as having progressive visual loss in both eyes over 3 years before diagnosis of a chiasmal glioma. She was then treated with supervoltage irradiation to the sella and parasellar area. Bitemporal fields measuring 5 x 5 cm each were initially used, and source skin distance of 80 cm with coplanar opposing technique was used whereby each field was treated daily to a midplane dose of 186 rads. The patient received a cumulative tumor dose over the 5-week course of 4680 rads. She tolerated this well, and her visual function was stabilized thereafter for over a year. Two years following therapy, she expired suddenly and unexpectedly at home. At autopsy, there was no radionecrosis in the brain or optic nerves, but minimal radiation changes were seen in the tumor. Extensive local invasion was seen in the entire chiasm, adjacent optic tracts and hypothalamus. In addition, other disparate small fibrillary astrocytic gliomas were found in the optic radiations, midbrain, and left anterior midfrontal lobe. This patient therefore documents clinically progressive visual deterioration before irradiation therapy, and palliative visual function stability for well over a year after irradiation therapy. The patient also demonstrates the difficulty in treating a locally aggressive optic chiasmal glioma, its infiltrative nature, and the multifocality of other unsuspected neural tumors in neurofibromatosis.