Clinical characterization of unknown/cryptogenic status epilepticus suspected as encephalitis: A multicenter cohort study

Autoimmune and unknown/cryptogenic encephalitis have been increasingly noted in the inflammatory etiology of new-onset status epilepticus (SE). We aimed to investigate clinical characteristics and the potential role of immunotherapy in encephalitis-related adult SE through our multicenter prospective SE registry. Among the 274 patients with SE, 35 (12.8%) patients demonstrated an inflammatory etiology and 19 out of 35 (54.3%) patients demonstrated unknown/cryptogenic cause. Patients with autoimmune and unknown/cryptogenic encephalitis shared similar clinical features. In unknown/cryptogenic encephalitis, the proportion of favorable outcomes (mRS 0–3) showed a different propensity at 3–6 months after discharge between patients receiving active immunotherapy and not receiving any immunotherapy, although it was not statistically significant (at admission 28.6% vs 20%, p = 0.603; at discharge 57.1% vs 60%, p = 0.570; at 3–6 months after discharge 90% vs 60%, p = 0.214 in patients treated with active immunotherapy or without immunotherapy, respectively). Extensive autoantibody screening should be carried out and empirical immunotherapy may be potentially helpful even in patients without antibodies, although longer term and multi-national studies may be necessary to make a stronger recommendation.