Spectrum and Evolution of EEG Changes in Anti-NMDAR Encephalitis

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.

We retrospectively characterized the clinical and EEG findings in our NMDARE patients (n = 48). A total of 131 EEGs were analyzed.

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.

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.