Low-voltage EEG activity presenting from psychotic stage in a patient with anti-NMDA receptor encephalitis

EEG in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis shows generalised or predominantly frontotemporal δ-θ activity, and epileptiform potentials are less frequent than slowness. The voltage of EEG activity in this disorder is uncertain. We studied the voltage pattern of EEG of two patients. Both patients had psychiatric symptoms, central hypoventilation requiring prolonged ventilatory support, seizures, involuntary movements and autonomic instability. No patient showed abnormal findings on conventional MRI. Mature teratoma was diagnosed in one patient after ovarian tumour resection. Both patients received corticosteroids and intravenous immunoglobulins, and plasmapheresis. One patient recovered completely. In one patient, teratoma was not found, and ventilatory support or sedative drugs were given for about 35 months. The EEG voltages in both patients were decreased in all brain areas as compared with those of the healthy controls. Low-voltage EEG activity in all brain areas was evident from the psychotic stage.