To describe a complicated case of anti-NMDAR encephalitis in a schizophrenic patient treated with antibiotics for possible bacterial meningitis showing minimal improvements.

Anti-N-Methyl-D-Aspartate receptor (NMDAR) encephalitis, a rare neuroinflammatory autoimmune disorder, characterized by altered mental status, seizures, catatonia, autonomic instability, altered behavior, acute psychosis, and movement disorders. It is caused by autoantibodies against the NMDAR subunits NR1, NR2. Here we present a difficult case of a patient diagnosed with treatment-resistant schizophrenia, admitted to the hospital for suspected recurrent bacterial meningitis. However, he was finally diagnosed with NMDA encephalitis and showed significant improvement with immunosuppression.

A 67-year-old male with an unclear history of schizophrenia, HTN, DM2 presented with  new-onset dysarthria, drooling and unsteadiness, without other neurological deficits. Stroke was ruled out with normal CT head and CTA, his symptoms worsened with altered mental status and agitation, infectious work up was negative, chemistry showed normal ammonia and hyponatremia. EEG showed moderate to severe generalized slowing, but no seizures. CSF showed elevated protein, negative PCR infectious panel, however, the culture was positive for enterobacter cloacae with BAL culture also positive for enterobacter cloacae and Klebsiella pneumoniae. He received antibiotics with partial improvement. Brain MRI was unremarkable, repeat CSF studies were unchanged, antibiotics were switched, and he was discharged still confused, in stable condition with long-term IV antibiotics. One month later, was re-admitted with sudden onset of altered mental status, psychomotor agitation, and right-sided hemiparesis. Again negative stroke and infectious workup, however, the CSF autoimmune encephalitis panel was positive for anti-NMDAR antibodies. IVIG was started resulting in significant improvement in his mentation, returning to his baseline.

NMDAR autoimmune encephalitis cases can be challenging because current guidelines prioritize infectious causes. In our patient’s case a doubtful diagnosis of schizophrenia, combined with misleading infectious workup results, led to overlooking organic causes for his behavioral symptoms.