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

OBJECTIVE: To describe initial and follow-up electroencephalographic (EEG) characteristics in anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis.

METHODS: Consecutive 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.

RESULTS: In six patients, [corrected] the waking EEG showed preserved background activity and either focal or unilateral hemispheric slowing. These children had more favorable outcome than the three children with diffuse slowing. Unilateral [corrected] abnormal movements contra-lateral to hemispheric or focal slowing were also indicative of milder severity when compared to generalized abnormal movements and diffuse slowing. During non-rapid eye movement (NREM) sleep, a decrease in the expected slow waves and unilateral or diffuse theta-alpha band rhythms were observed in six children, not correlated with the outcome, representing a suggestive EEG pattern of anti-NMDAR encephalitis. [corrected].

CONCLUSIONS: In 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.

SIGNIFICANCE: This case series demonstrates that early EEG patterns may be suggestive of anti-NMDAR encephalitis in pediatric patients with behavioral disorders and abnormal movements.