[Autoimmune Encephalitis Triggered by Herpes Simplex Encephalitis: Main Syndrome, Diagnosis, and Treatment]

Autoimmune disorders, such as choreoathetosis and abnormal behavior secondary to herpes simplex encephalitis (HSE), are discussed in this review. These disorders are known to develop without any evidence of HSE relapse, while they respond to immunotherapies such as intravenous corticosteroids. Recent evidence, including a prospective Spanish cohort study of HSE, revealed that autoimmune encephalitis (AE) can be triggered by HSE, which is closely related to several neuronal surface antibodies (NSAs). Anti-N-methyl-D-aspartate encephalitis (NMDARE) is the most common phenotype of AE post-HSE. Moreover, approximately 30% of cases of AE post-HSE are caused by NSAs against undetermined antigens. Thus, patients suspected of having AE post-HSE should be tested for NSAs using comprehensive techniques combining tissue-based and cultured live neuron assays. The primary syndrome of AE post-HSE is age dependent, as demonstrated in non-post-HSE onset NMDARE. Choreoathetosis is the most common symptom in infants and toddlers, while abnormal behavior and psychiatric symptoms are the most common symptoms in adolescents and adults. Regarding the treatment, current knowledge reveals that intensive immunotherapies can be used to treat AE post-HSE and lead to better outcomes although a minority of cases show recovery without immunotherapy administration.