Post-radiation optic neuropathy

A middle-aged man developed subacute painless visual loss in the left eye leading to no light perception, and 2 weeks later developed subacute visual loss in the right eye to no light perception. He had a history of resected pituitary macroadenoma. MR scan of brain and orbits with contrast showed short prechiasmatic segments of enhancement in each optic nerve. Cerebrospinal fluid analysis was normal. Extensive diagnostic work-up was unrevealing but review of medical records identified a history of prophylactic radiotherapy to the pituitary gland following pituitary macroadenoma resection 1.5 years before. We diagnosed post-radiation optic neuropathy. This condition typically occurs 1-1.5 years after the radiotherapy given near the visual pathway. Its pathophysiology presumably relates to an endotheliopathy of the vasa nervosum supplying the optic nerve due to free radical accumulation following radiotherapy. It manifests with unilateral or bilateral sequential severe visual loss with imaging showing characteristic enhancement of the short segment of the affected intracranial optic nerve. There is no available definitive treatment, but hyperbaric oxygen therapy, given shortly after onset of visual loss, is a promising treatment.