Acquired epileptic aphasia in NMDA encephalitis: a unique electroclinical presentation with pathophysiological considerations.

A boy in his middle childhood who was premorbidly normal presented with new-onset seizures and progressive auditory aphasia, raising suspicion of Landau-Kleffner Syndrome (LKS). Continuous spike and wave during sleep with a left centrotemporal spike pattern on the electroencephalogram (EEG) supported the preliminary diagnosis. But the febrile episodes after admission and the MRI findings suggestive of autoimmune encephalitis changed the diagnostic considerations. A repeat EEG performed had an extreme delta brush pattern, a finding strongly suggesting the possibility of autoimmune encephalitis. Confirmed with N-methyl-D-aspartate (NMDA) antibody positivity in cerebrospinal fluid, establishing NMDA receptor encephalitis (NMDARE). Despite the different pathways of pathogenesis, there is significant clinical overlap between LKS and NMDARE, including speech regression and seizures in our index case. The child was managed with immunotherapy and seizure control measures, showing significant clinical improvement. This case illustrates the clinical overlap of LKS and NMDARE, also highlighting the critical role of NMDA receptors in speech and language, suggesting the need for early evaluation and prompt immunotherapy in cases with atypical presentations.