title: "Light switch" mental status changes and irritable insomnia are two particularly salient features of anti-NMDA receptor antibody encephalitis.
abstract: BACKGROUND
  Anti-N-methyl-D-aspartate antibody encephalitis is becoming increasingly recognized as a cause of acute and subacute encephalopathy in both adults and children. The typical features of this disorder include some degree of encephalopathy, seizures, and often a movement disorder component. However, there is wide variability in its presentation, and diagnosis based on clinical features alone is often delayed.
  
  
  METHODS
  We report a series of four of 12 patients observed at our children's hospital between 2011 and 2013 that we chose as particularly representative examples of two distinct clinical features.
  
  
  RESULTS
  In these individuals with anti-N-methyl-D-aspartate receptor antibody encephalitis, we note a very rapid on-off state between responsiveness and nonresponsiveness and/or insomnia accompanied by extreme irritability. We describe the abrupt mental status shift as "light switch" because the patients can awaken in seconds from a completely nonresponsive state. The insomnia noted in our patients was also impressive and often present early in the patients' courses.
  
  
  CONCLUSIONS
  Light switch mental status changes and irritable insomnia are important early features of anti-N-methyl-D-aspartate receptor antibody encephalitis that can signal the presence of this disorder. The exact pathophysiology of these two symptoms has not been fully elucidated, and we feel that presence of one or both of these symptoms early in the disease course should prompt immediate concern for this disorder.
authors.affiliation: University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas; Childrens Medical Center, Dallas, Texas.
authors.forename: Allen D
authors.initials: AD
authors.lastname: DeSena
authors.affiliation: University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas; Childrens Medical Center, Dallas, Texas.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Greenberg
authors.affiliation: University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, Texas; Childrens Medical Center, Dallas, Texas. Electronic address: Donna.graves@utsouthwestern.edu.
authors.forename: Donna
authors.initials: D
authors.lastname: Graves
mesh_terms: D000293:Adolescent; D060426:Anti-N-Methyl-D-Aspartate Receptor Encephalitis / Q000150:complications*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007508:Irritable Mood / Q000502:physiology*; D008297:Male; D001523:Mental Disorders / Q000209:etiology*; D007319:Sleep Initiation and Maintenance Disorders / Q000209:etiology*
keywords: NMDA; autoimmune; insomnia; mental status