[Analysis of prodromal phase and prodromal events in anti-N-methyl-D-aspartate receptor encephalitis]

Objective: To analyze prodromal phase and prodromal events of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Methods: Clinical data of 179 patients hospitalized and diagnosed during 2010-2016 including adults and children in Peking Union Medical College Hospital and Beijing Children's Hospital were collected.Patients with prodromal phase or prodromal events were selected.A retrospective analysis of clinical characteristics including prodromal phase or prodromal events, course of disease, brain imaging, laboratory results and therapeutic effect was performed. Results: Prodromal phase was presented in 31.8% (57/179) of patients.Most common symptoms included fever (73.7%) and headache (68.4%). Prodromal phase was prolonged in 6 patients, the longest being 64 days.Among those 6 patients (10.5%), headache and fever were the only symptoms throughout disease courses in 3 cases.Prodromal events were reported in 6.1% (11/179) of patients, including 5 patients after HSV1 encephalitis, 1 after Japanese encephalitis, and 2 after resection of melanocytic nevi. Conclusions: Anti-NMDAR encephalitis can be preceded with prolonged prodromal phase.In some patients prodromal symptoms are the only clinical presentation.Clinical features of those atypical cases suggest that infection may be the precipitating factor.Viral encephalitis including HSV1 encephalitis and Japanese encephalitis may be prodromal events in some cases.