Did you know patients with multiple sclerosis are at unique risk of experiencing toxicity in their radiation fields? Here is an interesting case report of a 44 year-old woman with breast cancer receiving Gamma Knife radiosurgery for an isolated slowly progressive small right cerebellar brain met. Within two months she developed a symptomatic, large liquified cavity adjacent to but separate from the small treated lesion consistent with cyst formation and radiation necrosis. The thought is that radiation damage to myelin-producing cells has a more profound clinical impact on a person with pre-existing demyelinating disease. Another layer of complexity is higher levels of chronic inflammation may quickly exacerbate otherwise subclinical radionecrosis. Importantly, the patient achieved durable resolution of her symptoms with a one-month course of steroids. | Liu, Adv Radiat Oncol 2023
