Background: Seizures are rare in REM sleep. To our knowledge, the effects of different sleep stages in anti-NMDA encephalitis have not been studied. Methods: Case report. Results: 32 year-old healthy female presented with acute fluctuating level of consciousness with episodic impulsivity, disorientation, and emotional outbursts following 3 days of headache. Her temperature was 37.8°C and she was started on ceftriaxone, vancomycin, and acyclovir. CSF only showed a total nuclear cell count of 182 and pleocytosis. MRI revealed increased T2 hyperintense right lateral temporal and parietal cortical thickening. EEG revealed right frontotemporal seizures with left sided rhythmic jerking, and an extreme delta brush pattern. Interestingly, seizures and extreme delta brush disappeared in REM sleep. After HSV PCR was negative, she was immunosuppressed with corticosteroids, IVIG, rituximab, and cyclophosphamide, given the extreme delta brush pattern. Repeat CSF analysis eventually yielded highly positive anti-NMDA antibodies. Ten weeks later, she became seizure free. Conclusions: For the first time, we report REM sleep in a case of anti-NMDA encephalitis during which there was absence of extreme delta brush and ictal EEG patterns. This observation may provide insight into the ongoing debate over whether extreme delta brush is an ictal EEG pattern.