Study of Influenza-Associated Encephalitis/Encephalopathy in Children During the 1997 to 2001 Influenza Seasons

Abstract

The 1997 to 2001 influenza A epidemics in Japan were markedly neurovirulent, and many children died of influenza-associated encephalitis/encephalopathy. We studied 20 patients with influenza-associated encephalitis/encephalopathy during the last four influenza seasons. No patients had been previously inoculated with influenza vaccine. Antipyretics were used in 16 patients before the onset of encephalopathy. Although all patients were treated intensively, 5 patients died and 8 had neurologic sequelae. Patients with coagulopathy, hepatic dysfunction, and computed tomographic abnormalities had a poor prognosis. The plasma concentrations of inflammatory cytokines were variable. The neuroradiologic findings could be divided into four categories. These findings indicated that the pathogenesis of the brain damage induced by influenza infection was variable. Further investigation is necessary to determine whether insufficient influenza vaccination or the use of antipyretics is one of the reasons for these epidemics of encephalopathy in Japanese children.

Viral encephalitis

“…MRI studies show nonspecific T2 signal abnormalities in the splenium, focal or generalized cerebral edema, posterior reversible encephalopathy, and ADEM. Acute necrotizing encephalopathy is a more specific type of severe encephalopathy associated with influenza, first described in Japanese children 24 . Clinical condition deteriorates rapidly and brain MRI shows bilateral necrosis of thalami and other regions, including the cerebral white matter, cerebellum, and brainstem.…”

The Value of Standardized Case Definitions in Encephalitis Clinical Research

“…In addition, influenza has been increasingly recognized as a vaccine preventable cause of encephalitis, especially in children and adolescents. 67 Initial reports emerged from Japan and the United States [68][69][70][71][72][73][74][75] and recently, a number of case reports as well as surveillance reports by CDC have been issued on neurologic complications of Influenza A (in particular pandemic H1N1) disease. [76][77][78][79][80][81][82][83][84][85][86][87][88] Example 3: Encephalitis as an adverse event following immunization (AEFI)…”

High Mobility Group Box 1 in Children with Acute Encephalopathy and Other Convulsive Diseases

“…Influenza virus is the most frequent cause at approximately one fourth [1][2][3]. Large amounts of inflammatory cytokines, such as interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α), are produced in influenza-associated encephalopathy [1,4].…”