Status Epilepticus Caused by Tick-borne Encephalitis.

We herein report a rare case of a 78-year-old Japanese man who developed refractory status epilepticus due to tick-borne encephalitis (TBE). The patient initially presented with left-sided hemiplegia and loss of consciousness. Initial diagnostic tests could not identify the cause of the encephalomyelitis, leading to a preliminary diagnosis of autoimmune encephalomyelitis. Despite treatment with corticosteroids and plasma exchange, the patient experienced status epilepticus, which required multiple antiseizure medications. TBE viral antibodies were eventually detected, confirming the diagnosis. Despite the treatment, the patient remained critically ill. Clinicians should consider TBE in the differential diagnosis of encephalitis of unknown origin associated with status epilepticus.