Case 1: A 61-year-old woman presented with horizontal binocular diplopia, progressive trismus, jaw spasms causing tongue biting, and trouble eating over 5 weeks. Brain MRI revealed dorsal pons and medulla T2-hyperintensity without enhancement. CSF showed no cells, protein 70 mg/dL, and 4 oligoclonal bands. ANNA-2 was present in CSF (1:128) and serum (1:7680), and invasive ductal breast carcinoma (stage 2) was found and treated with right mastectomy and chemotherapy. She developed episodic cyanosis from laryngospasm. Botox moderately helped her jaw opening dystonia, and tracheostomy was recommended for laryngospasm. She did not have improvement with steroids, intravenous immunoglobulin, rituximab, plasma exchange, or cyclophosphamide.  

Case 2:  A 51-year-old woman with a history of recurrent right breast cancer previously treated with bilateral mastectomy, chemotherapy, radiation, and hormonal treatment developed opsoclonus-myoclonus and progressive imbalance over 3 months leading to wheelchair dependence. ANNA-2 was detected in CSF (1:4096) and serum (1:15360). She received seven plasma exchange treatments and a 1-month course of high-dose oral steroids, followed by 1-month tapering. FDG-PET revealed cervical lymph node avidity presumed to be breast cancer recurrence that was treated with chemotherapy. Overall, she reported 70-80% symptom improvement and could walk independently. She was maintained on monthly plasma exchange.