Optic and perioptic enhancement as an imaging finding after radiation therapy

Purpose Radiation therapy that includes the optic nerve in the irradiation field can occasionally lead to severe complications such as optic neuropathy. For the early detection of such damage, knowledge of post-radiotherapy imaging findings is important. The aim of this study is to investigate the imaging findings of the optic nerve and its surrounding structures following radiotherapy. Methods This retrospective study targeted patients who underwent contrast-enhanced MRI as part of routine follow-up to assess for recurrence after radiation therapy for periorbital malignancies. The optic nerve assessment included unilateral evaluation in cases of maxillary sinus carcinoma, with bilateral evaluation in all other instances, cumulatively assessing 24 optic nerve sides of 16 patients. Results The abnormal enhancement was detected in 7 out of 16 cases. In terms of individual sides, abnormal enhancement was observed in 12 out of 24 sides. A significant association between abnormal enhancement and radiation dose was observed only in the optic nerve. Among the reviewed cases, one patient showed left optic nerve enhancement with a relative afferent pupillary defect; no others reported visual impairment. Conclusions Our study demonstrates that abnormal contrast enhancement around or within the optic nerve can occur after radiotherapy for head and neck malignancies, even in the absence of visual symptoms. While these imaging findings may represent a prodromal finding of Radiation-Induced Optic Neuropathy, it is also possible that they are benign post-radiation changes with limited clinical significance, and further studies are warranted.