EEG analysis in anti-NMDA receptor encephalitis: Description of typical patterns.

OBJECTIVE: To describe different electroencephalogram (EEG) patterns and epileptic features in patients with anti-N-methyl-D-aspartate receptor encephalitis (anti-NMDARE), their timeline in the course of the disease, their correlation with clinical data and outcome.

METHODS: We retrospectively analyzed EEG recordings between November 2007 and June 2016 in 24 consecutive patients.

RESULTS: Three EEG patterns were described: Excessive Beta Activity range 14-20 Hz (EBA) in 71% of patients, Extreme Delta Brush (EDB) in 58% and Generalized Rhythmic Delta Activity (GRDA) in 50%. They followed a chronological organization in the course of the disease: EBA appeared first, followed by EDB and then GRDA, as the median time of appearance for EBA, EDB and GRDA was respectively 10, 16.5 and 21.5 days. The presence of GRDA was strongly associated with concomitant abnormal movements (p < 0.001).

CONCLUSION: This study focuses on EEG and epileptic abnormalities in anti-NMDARE. Beyond EDB that were already reported (Schmitt et al., 2012), GRDA seems to be a very frequent pattern. Its rhythmic aspect should not be misinterpreted as seizure or status epilepticus, to avoid antiepileptic treatments intensification.

SIGNIFICANCE: This study comforts the importance of EEG in anti-NMDARE, with a better description of EEG abnormalities for a better treatment management.