Anti-NMDAR Encephalitis in children: Delineation of the epileptic phenotypes

Objective: Anti-NMDAR Encephalitis is an encephalopathic disorder involving seizures, neuropsychiatric symptoms, cognitive deterioration, dyskinesia and autonomic instability. Whereas in adults the epileptic phenotype mimics focal forms of epilepsy (temporal and extratemporal) as to EEG pattern and seizure semiology, the epileptic phenotype in children still asks to be characterised.

Methods: Delineation of epileptic phenotype was performed with continuous video-EEG monitoring for 5 days. Thus syndrome classification and localization of the epileptic focus was carried through before the diagnosis was established.

Results: We report on two girls aged 7 and 8 years without relevant medical history. The clinical picture developing over weeks consisted of aggressive behaviour, cognitive deterioration and seizures. Continuous video-EEG monitoring showed an encephalopathic pattern with background slowing and intermittent as well as continuous generalized slow activity. Furthermore generalized slow spike-wave complexes were present. We recorded dialeptic, tonic and tonic-clonic seizures without lateralization with a generalized seizure pattern. Serum anti-NMDA receptor antibodies were positive in both cases.

Interpretation: Distinguishing anti-NMDAR encephalitis in children from adult disease is important in diagnose finding because of numerous differences involved. Whereas in adults the phenotype of focal epilepsy is dominant, we were able to show in the demonstrated cases a picture of generalized epilepsy regarding EEG pattern and seizure semiology. We suggest that a few cases with cryptogenic Lennox-Gastaut syndrome responding positively to steroids could represent NMDAR associated encephalitis.