Delta brush on EEG: a characteristic EEG finding in autoimmune encephalitis

A woman in her late 20s was admitted via the emergency department in the psychiatric ward with acute-onset behavioural changes and suicidal thoughts in the past 2 weeks. Workup revealed positive N-methyl-D-aspartate (NMDA) receptor antibodies in cerebrospinal fluid and electroencephalogram (EEG) showing a specific pattern of delta brush on bilateral frontal regions. Other investigations were unremarkable. The patient was started on intravenous methylprednisolone 1000 mg for 5 days with oral steroids. She responded on steroids. She has been recommended for workup for teratoma/mediastinal tumours with NMDA receptor encephalitis is an autoimmune disorder predominantly affecting women of childbearing age. Delta brush pattern on EEG is specific for NMDA receptor encephalitis hence can be used as a diagnostic tool. It is advisable to investigate any patient with the presentation of mental deterioration for pathological causes. However, treatment with immunotherapy increases the chance of survival and may prevent cognitive impairment.