Chiasm and optic nerve necrosis following radiation therapy: Report of two cases

Abstract

Radiation necrosis of the optic nerve and chiasm occurs very rarely. Two cases are reported after telecobalt-60 therapy: one of a nasopharyngeal carcinoma (70 Grays in 33 fractions divided over 49 days), and one of a cavernous sinus meningioma (60 Grays in 29 fractions over 50 days). In both cases, visual impairment occurred one year after irradiation with progressive loss of vision (three and four months, respectively) as has been described previously. The fraction sizes were higher than generally recommended for preventing radiation necrosis.

Special features are the localization of the tumors, and a form simulating a tumor of the visual tract, in one case with unusual CT scan appearance. New fraction size patterns and optimum target volume focusing are therefore necessary to prevent necrosis.

Key Words:

• optic chiasm
• optic nerve
• tissue necrosis
• radiation therapy