Influenza-associated encephalopathy

Abstract

Influenza encephalopathy encompasses a wide range of syndromes. The conditions presumed to be involved in its pathogenesis include metabolic derangement, the systemic inflammatory response, and excitotoxicity. Imaging findings are important for the diagnosis of influenza encephalopathy. Acute necrotizing encephalopathy is characterized by bilateral thalamic lesions. Acute encephalopathy with biphasic seizures and late reduced diffusion is characterized by reduced diffusion in the subcortical white matter (bright tree appearance). Clinically, mild encephalitis/encephalopathy with a reversible splenial lesion is characterized by reduced diffusion in the splenium of the corpus callosum and it may be associated with symmetrical lesions in the deep white matter. Hemorrhagic shock and encephalopathy syndrome are characterized by rapidly progressing, extensive cerebral edema. Acute fulminant cerebral edema is a recently proposed disease entity, and its imaging findings are not yet well established. Although each imaging finding is characteristic, a comprehensive diagnosis, which includes the evaluation of clinical symptoms and other factors, should always be made.