To describe the encephalitis that have more frequently acute symptomatic seizures (ASS), type of seizures and development of postencephalitic epilepsy (PE).

Retrospective review of medical records of patients diagnosed with encephalitis between January-2006 and June-2018. Patients with previous epilepsy were excluded. The incidence of ASS, PE, clinical characteristics, complementary studies, treatment, and evolution was analyzed. For the comparison between groups, Chi square and Fisher tests were used for the categorical variables, and parametric and non-parametric methods for the continuous variables.

We included 130 patients with encephalitis, 46 infectious, 50 undetermined etiology and 34 autoimmune. 71% of the autoimmune patients presented ASS, being more frequent than the other etiologies (43% infectious and 58% undetermined etiology, p = 0.05). The autoimmune encephalitis presented a greater frequency of focal onset seizures to bilateral tonic-clonic, respect to the others (33% vs 7% undetermined etiology vs 10% infectious,   p = 0.008). Patients with autoimmune encephalitis developed more PE than the others (24% vs 9% undetermined etiology and 6% infectious, p = 0.2). The most frequent seizures during the evolution of PE in autoimmune encephalitis were focal onset seizures with impaired awareness.

In autoimmune encephalitis, a greater frequency of ASS was observed, manifested predominantly with focal onset seizures and evolved in a greater percentage of PE, compared with infectious and undetermined etiology encephalitis.
From the findings observed, it would be important to determine and establish if the precociousness of the specific treatment of autoimmune encephalitis, could modify the evolution to PE.