Emergence of Atypical Lymphocytes Before Cryptogenic New Onset Refractory Status Epilepticus: A Case Report

New-onset refractory status epilepticus (NORSE) is one of the most severe neurological manifestations of status epilepticus. The etiology is unknown in about 50% cases, as so-called cryptogenic NORSE (C-NORSE). We report a case with emergence of atypical lymphocytes just before C-NORSE. A 25-year-old woman with no significant medical history presented to our department with a 4-day history of headache and fever. Neurological examination and cerebrospinal fluid tests yielded normal results, but atypical lymphocytes were observed in the serum. Two days later, she was admitted to our emergency department in a comatose state, and subsequently developed convulsive refractory status epilepticus. The etiology remained unknown despite an extensive diagnostic work-up, so C-NORSE was diagnosed. Seizures were controlled with immunotherapies including corticosteroids, intravenous immunoglobulins, rituximab, tocilizumab, and administration of 4 antiseizure medications. The etiology of atypical lymphocytes involves hypercytokinemia similar to NORSE, and clarification of the emergence of atypical lymphocytes just before the onset of NORSE could contribute to the understanding of the pathophysiology of NORSE.