Delta brush variant: A novel ictal EEG pattern in anti-NMDAR encephalitis

Seizure is one of the main symptoms of anti-NMDAR encephalitis, but data of ictal electroencephalogram (EEG) patterns remain limited. In this study, we aimed to introduce a unique ictal pattern. This delta brush variant (DBV) was characterized as generalized delta rhythm with fast spike activity riding on it. We retrospectively evaluated the ictal pattern from six patients with anti-NMDAR encephalitis, and patients were grouped based on the presence of DBV. DBV was found in two patients who were in the florid phase of the disease: (a) A 17-year-old girl experienced rhythmical jerking of bilateral limbs. Corresponding EEG patterns showed generalized DBV. Seizure terminated after intravenous injection of midazolam, but oral-facial dyskinesia reappeared; and (b) a 24-year-old man suffered stiffening of the right limbs and oral-facial dyskinesia. The EEG pattern showed frontal DBV with left prominence. Seizure was controlled, but oral-facial dyskinesia remained after intravenous injection of midazolam. Compared with patients without DBV, patients in this group were more likely to have prolonged excessive delta brush (100% vs 25%) and hyperpyrexia (39.7℃ vs 38.2℃). Duration in ICU (36 days vs 18 days) and hospital (52 days vs 36 days) was relatively longer in DBV group, and no significant difference was found in terms of the mRS score (1 vs 0.5) and seizure relapse rate (0% vs 25%) during 3-month follow-up. DBV is a peculiar pattern in anti-NMDAR encephalitis. An EEG-based monitoring should be considered to avoid misleading this ictal EEG pattern to the electromyographic artifact.