Differentiation of the first psychotic episode and autoimmune encephalitis with anti-NMDA receptor antibodies, using the EEG findings – case report and literature review

Purpose: The first-time psychotic incident is a diagnostic challenge due to the lack of definite tests that initially verify the underlying cause. Differential diagnosis should include autoimmune encephalitis with anti-NMDA receptors antibodies (NMDARE). The waiting time for the antibodies determination, being the only method of confirmation, may exceed several days. The article presents the capability of electroencephalographic study (EEG) to strengthen the NMDARE suspicion. Case description: In a 19-year-old healthy woman sudden behavioural changes occurred. Initially, psychotic episode was diagnosed. Severity of the symptoms and no reaction to the treatment determined further diagnostics. Based on clinical symptoms and EEG, NMDARE was diagnosed and adequate treatment initiated. Antibody assay confirmed this diagnosis. Comment: The presence of extreme delta brush in the EEG with the clinical suspicion of NMDARE allows to accelerate therapy in anticipation of antibodies determination. The EEG can be a valuable diagnostic tool for differential diagnosis, especially in the first psychotic episode.