To describe a case from our institution that presented with Charles Bonnet syndrome (CBS) after radiation induced optic neuropathy (RION).

Radiation to the optic nerve is generally avoided due to the risk of RION. About 3.8% of brain, head, and neck tumor patients develop radiation-induced ocular changes. RION may result in irreversible vision loss, particularly in doses over 50 Gy. Charles Bonnet Syndrome (CBS) is rare disorder characterized by complex visual hallucinations in those with partial or complete vision loss. Few cases of CBS as a side effect of radiation have been described but it is likely under reported.

Case Report:

A 33-year-old male with a right frontal/ corpus callosum grade 2 oligodendroglioma, IDH MT, 1p/19q codeleted underwent a subtotal resection followed by radiation alone and four cycles of procarbazine, lomustine, and vincristine chemotherapy. Six months after radiation, he developed progressive bilateral vision loss. He subsequently developed complex visual hallucinations, initially involving common household objects and later progressing to images of animals including insects, antelopes, giraffes, and cats. He would attempt to interact with them but denied auditory hallucinations.