MON-133 Steroid Pulse Therapy for Radiation-Induced Optic Neuropathy After Pituitary Macroadenoma Treatment

Abstract Disclosure: R.B. Jacobo: None. M. Maningat: None. Introduction: Radiation-induced optic neuropathy (RION) is a rare, severe complication of radiation therapy, leading to painless, progressive vision loss due to vascular injury, ischemia, demyelination, and axonal damage. Risk factors include high radiation doses, fractionation schedules, and optic apparatus proximity to radiation. Diagnosis is clinical, supported by MRI showing optic nerve enhancement. No definitive treatment exists, though high-dose steroids are used to reduce inflammation, with uncertain efficacy in reversing vision loss. Case Report: A 68-year-old man with a history of non-functioning pituitary macroadenoma underwent transsphenoidal resection. Six months post-surgery, the MRI showed a residual tumor displacing the optic chiasm, prompting radiation therapy (5400cGy). The tumor remained stable post-radiation, and he remained asymptomatic. However, 18 months later, he developed progressive, painless vision loss. Optical coherence tomography showed ganglion cell and inner plexiform layer thinning, suggestive of chronic optic neuropathy. Perimetry revealed bitemporal hemianopsia. MRI showed persistent chiasmal compression without significant tumor growth. His medical history included type 2 diabetes mellitus, multinodular non-toxic goiter, secondary hypothyroidism (on levothyroxine), and secondary hypogonadism (not on testosterone therapy). His endocrine panel showed low testosterone, with normal thyroid and adrenal function. Diagnosed with radiation-induced optic neuropathy, he received IV methylprednisolone (1g daily for five days). Post-treatment perimetry showed significant improvement in temporal field defects. His vision continued to improve with ophthalmologic and endocrinologic monitoring. Long-term follow-up was recommended for potential recurrence and endocrine complications, including panhypopituitarism. This case highlights the importance of early recognition and treatment of RION, especially in patients treated for pituitary adenomas. Prompt steroid therapy may mitigate visual loss. Long-term multidisciplinary follow-up involving neuro-ophthalmology and endocrinology is crucial for managing post-radiation complications. Conclusion: Endocrinologists should recognize RION as a late complication in post-radiation patients, as misdiagnosis can lead to inappropriate management. Distinguishing RION from tumor progression or apoplexy is essential. While steroid therapy may help, collaboration with neuro-ophthalmologists is necessary to optimize outcomes. A multidisciplinary approach ensures endocrine stability and visual preservation. Presentation: Monday, July 14, 2025