Early and persistent ‘extreme delta brush’ in a patient with anti-NMDA receptor encephalitis

Since its original description in 2007, anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis associated with an ovarian teratoma is an increasingly recognized etiology of previously unexplained encephalopathy and encephalitis. Extreme delta brush (EDB) is a novel electroencephalogram (EEG) finding seen in many patients with anti-NMDAR encephalitis. The presence of this pattern is associated with a more prolonged illness, although the specificity of this pattern is unclear. Additionally, the frequency and sensitivity of EDB in anti-NMDAR encephalitis and its implications for outcome have yet to be determined. We report a patient with early evidence of extreme delta brush and persistence of this pattern 17.5 weeks later with little clinical improvement.