New-Onset Refractory Status Epilepticus (NORSE) As a Recurrence of Anti-Neuronal Nuclear Antibody 2 (ANNA-2) Encephalitis After Immune Checkpoint Inhibition Therapy

Paraneoplastic encephalitis from anti-neuronal nuclear antibody 2 (ANNA-2), usually associated with breast cancer, can cause seizures. We report a case of recurrent paraneoplastic encephalitis due to ANNA-2 presenting with new-onset refractory status epilepticus (NORSE) one month after receiving checkpoint inhibitors therapy. A 69-year-old female was diagnosed with opsoclonus myoclonus syndrome (OMS) secondary to ANNA-2, which led to a diagnosis of breast cancer. OMS improved with surgical resection and intravenous immunoglobulin (IVIG). Three years later, she was diagnosed with metastatic cancer to the liver and spine. She underwent immune checkpoint inhibitor therapy. One month later, she was admitted with NORSE. Opsoclonus was seen at the physical exam. Brain MRI and infectious work-up were unremarkable. Cerebrospinal fluid (CSF) analysis revealed pleocytosis with lymphocytic predominance. She was treated with corticosteroids and immunoglobulins, and she had symptomatic improvement. ANNA-2 test was positive in a lower titration than three years earlier. Opsoclonus in a patient with NORSE can be the hint of ANNA-2 positivity. Immune checkpoint inhibitor therapy should be carefully reconsidered in patients with a history of paraneoplastic encephalitis for ANNA-2 as it could precipitate NORSE.