Focal seizures in children with anti-NMDA receptor antibody encephalitis

• Seizures in children with anti-NMDA encephalitis are focal; focal SE is common.
• Focal seizures in anti-NMDA encephalitis have a characteristic EEG onset.
• Initial EEG can be normal in anti-NMDA encephalitis even in the setting of seizures.
• Children with undiagnosed anti-NMDA encephalitis can raise concern for PNES.
• Video EEG monitoring is indispensible in early diagnosis of anti-NMDA encephalitis.

SummaryObjectiveWe investigated the electroclinical features of seizures occurring in children with anti-NMDA receptor antibody encephalitis.MethodsClinical features and video EEG recordings were analyzed from pediatric patients with anti-NMDA receptor antibody encephalitis at our center over a six year period.ResultsWe identified eight pediatric patients with anti-NMDA receptor antibody encephalitis. Video EEG captured multiple focal seizures in four patients. Ictal onset in all four patients consisted of a focal rhythmic sharpened 6–12 Hz activity that subsequently spread to one or both hemispheres. When there was a clinical correlate, seizure semiology was limb posturing with or without dyscognitive features. While background abnormalities were noted at presentation in three cases, the initial EEG background was normal in five, including three patients presenting with seizures. The EEG background deteriorated with clinical progression.ConclusionsFocal seizures are common in pediatric patients with anti-NMDA receptor antibody encephalitis and have a characteristic ictal onset pattern. Anti-NMDA receptor antibody encephalitis should be considered in the differential diagnosis of a child presenting with new onset focal seizures, irrespective of the EEG background, especially if accompanied by dyskinesia, psychiatric symptoms or impaired cognition.