Review of the aetiology, diagnostics and outcomes of childhood encephalitis from 1970 to 2009

Aim: Encephalitis is a rare, serious condition, and antiviral therapies, increased knowledge of inflammatory pathways and improved diagnostics have increased the therapeutic possibilities. We describe 40 years of childhood encephalitis in Sweden, covering the diagnostics, aetiology and outcomes. Methods: We reviewed the clinical data that were available for all children discharged from the Karolinska University Hospital in Stockholm following treatment for encephalitis from 1970 to 2009. The hospital treated all children in the region with the condition during the study period. Results: There were 408 episodes of encephalitis from 1970 to 2009 and the incidence was similar over the whole period, ranging from 6.4 to 8.7 per 100 000 child years. Although mortality markedly decreased from 10% in the first decade to zero in the last decade, and aetiologies shifted, no clear long-term improvements in outcome were seen. The need for intensive care was unchanged (18-20%) for each of the study intervals, possibly indicating that the severity of cases remained unaltered. Conclusion: Understanding the pathophysiological mechanisms of encephalitis is vitally important for developing more efficient treatment regimens. As well as reporting the results of this 40-year study, this study considers possible explanations, addresses current therapeutic options and explores directions for central nervous system infection research.