Spectrum and Evolution of EEG Changes in Anti-NMDAR Encephalitis

BACKGROUND: NMDA receptor encephalitis (NMDARE) is the most prevalent autoimmune encephalitis and it encompasses a spectrum of clinical features. It is most commonly associated with alteration in consciousness, seizures, neuro-psychiatric symptoms, and movement disorders. Electroencephalography (EEG) plays a vital role and can give clues to diagnosis in a subset of patients. METHODS: We retrospectively characterized the clinical and EEG findings in our NMDARE patients (n = 48). A total of 131 EEGs were analyzed. RESULTS: We observed that patients with seizures had a younger age of onset (p < 0.001). The most common EEG pattern that was noted was diffuse slowing (n = 20) followed by generalized rhythmic delta activity (n = 9), focal spikes and slowing (n = 8 each). Delta brush pattern was seen in only 3 EEGs. Focal ictal rhythms were seen in 3 EEGs. There was no significant difference in outcomes such as seizure recurrence, modified Rankin score (mRS) at follow up/discharge or relapse between groups of patients who had EEG abnormalities in the first EEG and with those who did not. CONCLUSIONS: NMDARE has varied EEG findings, most of them being non-specific. When combined with clinical presentation, EEG is a useful tool in the diagnosis and management of NMDARE.