Extreme delta brush in electroencephalogram may be nonspecific to the anti-NMDAR encephalitis. (P5.223)

Objective: To clarify whether extreme delta brush (EDB) in electroencephalogram (EEG) is specific to a diagnosis of anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis. Background: EDB has been reported as a unique EEG pattern observed in up to 30% of patients with anti-NMDAR encephalitis. To our knowledge, encephalitis negative for anti-NMDAR antibodies with the EDB finding has never been reported. Design/Methods: We reviewed the EEG data of consecutive 26 patients with encephalitis from 2015 to 2016 in a single-center. Anti-NMDAR antibody was tested with cell-based assay. Results: EDB was observed in 3 patients. Anti-NMDAR antibodies were negative in the cerebrospinal fluid of Patient 1 and 2, and for Patient 3 investigation is incomplete. All patients received conventional combination therapy for autoimmune encephalitis: high-dose corticosteroid, intravenous immunoglobulin, plasmapheresis, or intravenous cyclophosphamide (IVCY). They had no tumors including teratoma. Patient 1: A 21-year-old woman presented with fever and generalized tonic-clonic seizure. There were no signs of psychosis or abnormal behavior. The diagnosis was encephalitis with febrile refractory convulsive status epilepticus. IVCY resulted in a slight improvement, but she died of sepsis. Patient 2: A 51-year-old man presented with fever, asymmetric tonic limb posturing and loss of consciousness. First and second EEGs showed slow waves, but his third EEG showed bilateral periodic epileptiform discharges. The diagnosis was non-herpetic encephalitis with sinus arrest and status epilepticus. Corticosteroid and immunoglobulin therapy were ineffective, but he responded to IVCY. After 5 months of treatment he was discharged home and currently he is independent for daily activities. Patient 3: A 10-year-old girl was admitted with a diagnosis of limbic encephalitis due to delusion, abnormal behavior, fever, and involuntary movement. Although corticosteroid and immunoglobulin were ineffective, she responded to IVCY and plasmapheresis. After a month of onset she is improving. Conclusions: EDB may not be as specific to anti-NMDAR encephalitis as reported. Disclosure: Dr. Namekawa has nothing to disclose. Dr. Mori has nothing to disclose. Dr. Tabata has nothing to disclose. Dr. Miyahara has nothing to disclose. Dr. Minote has nothing to disclose. Dr. Nishida has nothing to disclose. Dr. Shindo has nothing to disclose.