Describe electroencephalogram (EEG) characteristics in pediatric anti-NMDA Receptor Encephalitis (NMDARE) and correlate with clinical course.

Electrographic findings are variable in NMDARE. Extreme delta brush (EDB) is an electrophysiologic biomarker of NMDARE and associated with prolonged hospitalization.¹ However, how EDB and other EEG characteristics correlate with clinical course is unknown in children. EEG features in pediatric NMDARE include background slowing, rhythmic delta activity, and interictal epileptiform discharges,^2,4,8-10  with EDB rates reported between 6-53%.^2-4 Electrographic seizures range from 11-52% with status epilepticus in 0-50%.^2,4,8-10 Sleep disturbances and insomnia also occur including changes in stage III and REM sleep.⁵ We examined EEG and sleep characteristics in pediatric NMDARE.

Retrospective chart and EEGs were reviewed in pediatric NMDARE patients at Children’s Healthcare of Atlanta between 2017 and 2020. Institutional Review Board approval was obtained. 11 patients were included; exclusion criteria included a history of herpes simplex virus encephalitis or unavailable EEG. EEGs were reviewed by two epileptologists, and a third if disagreement occurred. Descriptive statistics, student’s t test, Fisher’s exact test and linear regression were used, with Holm-Bonferroni correction for multiple comparisons (STATA).

11 patients (8 female) were included. 63.6% had EDB and 36.4% had generalized rhythmic delta on EEG. Clinical seizures occurred in 63.6% and epileptiform discharges occurred in 27.3%. 81.8% reported sleep disturbance but did not correlate with absence of electrophysiologic sleep (observed in 27.3%). Average hospital length of stay (LOS) (inpatient hospitalization plus inpatient rehabilitation) was 63 days versus 39.5 days in EDB versus non-EDB but this was not significant (p = 0.22). EDB correlation with symptom number would be significant if not for Holm-Bonferroni correction (p = 0.045). Higher immunotherapy number correlated with increased LOS (p = 0.018).

63.6% of pediatric patients had delta brush. Further studies are needed to correlate electrophysiological biomarkers with clinical course and outcomes.