Serial and prolonged EEG monitoring in anti-N-Methyl-d-Aspartate receptor encephalitis.

Objective: To describe serial electroencephalographic (EEG) findings of three patients with anti-NMDAR encephalitis.

Methods: Three women (age 15-34years) with confirmed anti-NMDAR encephalitis underwent serial EEG recordings. Continuous EEG for 72h was performed in one case and 3-day video-EEG monitoring was obtained in two cases.

Results: Generalized rhythmic delta activity (GRDA) was found in all patients. GRDA persisted for hours, but was not continuous on a 24-h EEG recording, disclosed no frequency, voltage or field evolution, and was not seen on the first EEG of two patients. Extreme delta brush was noted in two patients who presented more severe disease. One patient presented seizures, which were electrographically and clinically different from the GRDA pattern and from dyskinetic movements.

Conclusions: Serial or continuous EEG may be necessary to detect GRDA in anti-NMDAR patients. To avoid unnecessary treatment, this pattern should not be interpreted as indicative of ictal activity, unless there is evidence of its ictal nature.

Significance: Our findings may contribute to the diagnosis of anti-NMDAR encephalitis in cases with characteristic clinical picture.