EEG extreme delta brush; could be an ictal pattern in patients with anti-NMDA receptor encephalitis

INTRODUCTION: Anti-NMDA receptor (NMDAr) encephalitis associated syndrome includes neuropsychiatric symptoms, impaired consciousness, seizures, autonomic instability, and hypoventilation. The electroencephalographic (EEG) activity throughout the course of the disease has not been documented enough. We reviewed electroclinical data of patients with NMDAr encephalitis contributing to characterize their EEG and its clinical correlation. MATERIAL AND METHODS: We retrospectively identified 16 patients with NMDAr encephalitis. 15 of them underwent video-EEG in the acute phase in 8 Spanish Medical centres. The other was excluded because video EEG was performed outside the acute phase. RESULTS: 15 patients (11 females). Median age 37.4 (range 14-87) years. Seizures occurred in 9 (60%), and status epilepticus (SE) in 5 (33,3%;), MRI (Magnetic resonance imaging) was abnormal in 10 (66.6%), and CSF (Cerebrospinal fluid) was normal in 3 and abnormal in 12 with positive PCR (polymerase chain reaction) for mycoplasma pneumoniae (1/15) and virus herpes simple (1/15). Ovarian teratoma was found in 1 patient, other malignacies (small cell lung carcinoma) in 1 patient. EEG was abnormal in acute phase in 14/15 (93.3%). Extreme delta brush (EDB) was observed in 5 (33.3%), the presence of EDB was associated with SE in all cases (3 subtle SE and 2 non convulsive SE). Rhythmic delta activity without EDB 5 (33.3%). Excessive beta was present in 8 (53%). EDB can follow a pattern of well characterized electroclinical seizures. CONCLUSIONS: Almost invariably, patients with NMDAr encephalitis had abnormal EEG. The presence of EDB in our patients is associated with seizures, SE and can follow electroclinical seizures. These findings suggest that EDB could be an evolutive pattern of an SE in NMDAr encephalitis.