Early electro-clinical features may contribute to diagnosis of the anti-NMDA receptor encephalitis in children

• Abundant theta and alpha band rhythms in non-rapid eye movement (NREM) sleep represent a suggestive EEG pattern of anti-NMDA receptor encephalitis in pediatric patients.
• Preserved background activity over at least one hemisphere in the awake state and in sleep were correlated with milder clinical expression.
• The disruption of NMDA neurotransmission may lead to decrease of the slow waves component in the NREM sleep.

ObjectiveTo describe initial and follow-up electroencephalographic (EEG) characteristics in anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis.MethodsConsecutive polygraphic video-EEG recordings were analyzed in nine pediatric patients with anti-NMDAR encephalitis at the initial stage of the disease and during the intermediate period until motor recovery. EEG characteristics in waking and sleep stages as well as EEG correlates of abnormal movements are described.ResultsIn six of nine patients with anti-NMDAR encephalitis, the waking EEG showed preserved background activity and either focal or unilateral hemispheric slowing. During non-rapid eye movement (NREM) sleep, a decrease in the expected slow waves and unilateral or diffuse theta-alpha band rhythms were also observed in six of nine children. They all had more favorable outcome than the three children with diffuse slowing. Clinically, unilateral abnormal movements contra-lateral to hemispheric or focal slowing were also indicative of milder severity when compared to generalized abnormal movements and diffuse slowing.ConclusionsIn pediatric patients presenting behavioral disorders and abnormal movements, early EEG patterns may be suggestive of anti-NMDAR encephalitis. Moreover early electro-clinical presentation contributes to outcome prediction.SignificanceThis case series demonstrates that early EEG patterns may be suggestive of anti-NMDAR encephalitis in pediatric patients with behavioral disorders and abnormal movements.