A 6-year-old female with no past medical history presented to the ED for acute changes in temperament and speech. One month prior, she experienced rapid behavioral shifts, followed by mid-sentence staring spells. One week before admission, she developed new-onset stuttering. On admission, a neurological examination showed expressive aphasia. She demonstrated emotional lability related to speech production, with instances of aggression after language errors and rapid improvement in mood upon correctly identifying words.
Laboratory tests, including CMP, CBC, and UDS, were normal. Brain MRI with and without contrast was unremarkable. The initial EEG showed focal epileptiform discharges, prompting the initiation of levetiracetam. CSF analysis was without signs of infection or inflammation. Methylprednisolone was initiated for suspected autoimmune encephalitis (AIE). After five days of therapy, her agitation worsened, with new lip smacking and left-sided facial droop. Repeat EEG showed generalized slowing with areas of increased electrical activity and cortical dysfunction, prompting the addition of valproic acid. While these medication changes resulted in reduced aggression, emotional lability persisted.
Due to persistent symptoms despite a dual anti-epileptic treatment regimen, a third EEG was ordered, which revealed left hemispheric delta brushes, supporting the diagnosis of AIE. This was confirmed 2 weeks later with positive CSF NMDA-receptor antibody titer.