Epidemiology of acute encephalopathy in Japan, with emphasis on the association of viruses and syndromes

Brain Dev. 2012 May;34(5):337-43. doi: 10.1016/j.braindev.2011.07.012. Epub 2011 Sep 15.


A research committee supported by the Japanese government conducted a nationwide survey on the epidemiology of acute encephalopathy in Japan using a questionnaire. A total of 983 cases reportedly had acute encephalopathy during the past 3 years, 2007-2010. Among the pathogens of the preceding infection, influenza virus was the most common, followed by human herpesvirus-6 (HHV-6) and rotavirus. Among syndromes of acute encephalopathy, acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) was the most frequent, followed by clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS), acute necrotizing encephalopathy (ANE) and hemorrhagic shock and encephalopathy syndrome (HSES). Influenza virus was strongly associated with ANE and MERS, HHV-6 with AESD, and rotavirus with MERS. Mortality was high in ANE and HSES, but was low in AESD, MERS and HHV-6-associated encephalopathy. Neurologic sequelae were common in AESD and ANE, but were absent in MERS.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Encephalitis / epidemiology*
  • Encephalitis / etiology
  • Female
  • Health Surveys
  • Humans
  • Incidence
  • Infant
  • Influenza, Human / complications*
  • Japan / epidemiology
  • Male
  • Roseolovirus Infections / complications*
  • Rotavirus Infections / complications*