title: Severe form of encephalopathy associated with 2009 pandemic influenza A (H1N1) in Japan.
abstract: BACKGROUND
  Every year, an estimated 200-500 children in Japan develop influenza-associated encephalopathy (IAE), and 10-30% of these children die.
  
  
  OBJECTIVE
  To clarify the clinical features of a severe form of acute encephalopathy seen with 2009 pandemic influenza A (H1N1).
  
  
  METHODS
  This retrospective survey examined 20 children with acute encephalopathy associated with the 2009 pandemic influenza A (H1N1) who died or were in a prolonged deep coma with a flat electroencephalogram tracing and loss of spontaneous respiration. We obtained demographic, clinical, laboratory, and neuroimaging data through interviews with the attending physicians and chart reviews.
  
  
  RESULTS
  Subjects were 13 boys and seven girls. Their median age was 45 (range 11-200) months. Five patients had one or more pre-existing conditions. Acute encephalopathy developed within 2 days after influenza onset in 16 patients. As the initial neurological symptom, delirious behavior was seen in six children, and brief seizures in six. Eighteen patients were comatose within 6h of the onset of encephalopathy. Marked brain edema on computed tomography (CT) was seen in all but one patient. Brainstem lesions on CT were recognized in 12 patients. Sixteen patients died 0-45 (median 2.5) days after the onset of acute encephalopathy, and the others remained in deep comas without spontaneous respiration.
  
  
  CONCLUSIONS
  The clinical course of the patients was characterized by an onset with mild neurological symptoms and rapid deterioration of consciousness into coma. Head CT revealed marked cerebral edema, often associated with brainstem lesions.
authors.affiliation: Department of Pediatrics, Juntendo University Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. okumura@juntendo.ac.jp
authors.forename: Akihisa
authors.initials: A
authors.lastname: Okumura
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakagawa
authors.forename: Hisashi
authors.initials: H
authors.lastname: Kawashima
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Morichi
authors.forename: Takashi
authors.initials: T
authors.lastname: Muguruma
authors.forename: Osamu
authors.initials: O
authors.lastname: Saito
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Fujimoto
authors.forename: Chiaki
authors.initials: C
authors.lastname: Toida
authors.forename: Shuji
authors.initials: S
authors.lastname: Kuga
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Imamura
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Shimizu
authors.forename: Naomi
authors.initials: N
authors.lastname: Kondo
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Morishima
mesh_terms: D000293:Adolescent; D001929:Brain Edema / Q000473:pathology; D001933:Brain Stem / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D018792:Encephalitis, Viral / Q000473:pathology*; D005260:Female; D006257:Head / Q000000981:diagnostic imaging; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000502:physiology*; D007251:Influenza, Human / Q000150:complications*; D007564:Japan; D008297:Male; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed