Abstracts

Rationale: Anti-NMDA receptor encephalitis (anti-NMDARE) is an increasingly recognized etiology of previously unexplained encephalopathy and encephalitis in the pediatric population. It associates epilepsy with psychiatric manifestations, movement disorders, memory deficits and autonomic instability. Recent studies have identified a specific EEG pattern in adult patients with anti-NMDARE named 'burst and slow complexes' (Ikeda A et al., Epileptic Disord. 2006) or 'extreme delta brushes (EDB)' (Schmitt SE et al., Neurology 2012). This study aimed to determine if this EEG pattern reported in adults is seen in pediatric patients with anti-NMDARE.Methods: Two certified neurophysiologists (CG and DN) have independently evaluated the EEG recordings of all the pediatric patients (n=11) diagnosed with anti-NMDARE at the Hospital for Sick Children in Toronto, Canada. Recordings performed while patients were receiving high dose barbiturates or benzodiazepines were excluded as these medications can artificially increase the fast EEG activities and may be a confounder for EDB.Results: All patients diagnosed with anti-NMDARE had at least 1 EEG recording performed, age range was 4-17 years and sex ratio M:F 5:6. Most of them (63%) required continuous EEG monitoring due to the high seizure burden. EDB were seen in all patients that required ICU admission (n=7, M:F 4:3). This suggest that the presence of this pattern is associated with a more severe and prolonged illness, possibly due to a higher titer of the anti-NMDA receptor antibodies. Other EEG abnormalities included intermittent rhythmic slowing (FIRDA, TIRDA) or persistent slowing (focal or generalized). Patients with intermittent slowing or persistent slowing (but no EDB) did not require ICU admission.Conclusions: EDB is a novel EEG finding seen in many children with anti-NMDARE. The incidence in our cohort was much higher than the one reported in adults by Schmitt SE et al. (63% vs. 30%). Since EEG is usually a first line investigation for patients with encephalopathy the identification of EDB in children should raise the clinical suspicion for anti-NMDARE and prompt early therapeutic intervention. Future studies are required to confirm the specificity of EDB for anti-NMDARE.