A favorable outcome of intensive immunotherapies for new-onset refractory status epilepticus (NORSE)

BACKGROUND: New-onset refractory status epilepticus (NORSE) is a newly defined critical disease entity characterized by prolonged periods of refractory epileptic seizure with no readily identifiable cause in otherwise healthy individuals. Its etiology is uncertain, but autoimmune encephalitis is a possible candidate for the underlying cause of this condition. Immunotherapies could be considered for this condition, but its efficacy is not established. CASE PRESENTATION: A 31-year-old man with no prior history presented with refractory status epilepticus. His seizure persisted even with multiple anti-epileptic drugs and required prolonged general anesthesia under mechanical ventilation. Magnetic resonance imaging and cerebrospinal fluid did not indicate the cause of seizure, and autoantibodies related to encephalitis were not detected. It was speculated that the patient had occult autoimmune encephalopathy because of its acute-onset clinical course preceded by fever, even without definite evidence of an autoimmune mechanism. The patient received intravenous methylprednisolone, plasma exchange, and intravenous immunoglobulin in succession and manifested a favorable outcome after these treatments. CONCLUSION: Our case supports the efficacy of immunotherapies for NORSE even though it does not manifest definite evidence for autoimmune background. Clinicians should consider these immunotherapies for NORSE as early as possible, because this condition is associated with high mortality and morbidity owing to prolonged seizure activity and long-term intensive care including general anesthesia and mechanical ventilation.