A 69-year-old woman, whose right breast cancer had been treated by surgery and radiation at age 50, had right hand sensory loss and pain. The hand began to show choreoathetosis (video). Blood examination revealed that anti-Hu, anti-Yo, and anti-Ri antibodies were negative but anti-SS-A antibody was positive without sicca syndrome. Neurogenic changes, including myokymic discharges, were present diffusely in the right arm on EMG (figure, A), suggesting radiation-induced brachial plexopathy. Brain and cervical MRIs were normal. PET was normal within the right arm and the brain (figure, B and C). Two years later, both the choreoathetosis and myokymic discharges had ameliorated.