Influenza-associated encephalopathy in Japan.

Although the clinical entity of influenza-associated encephalopathy (influenza encephalopathy) has not gained universal recognition, it has been reported frequently as a complication of influenza in Japanese children. The influenza type A (H3N2) virus was detected in most cases. Most of the patients have been young children. Influenza encephalopathy typically is associated with a sudden onset of high fever, severe convulsions, rapidly progressive coma, and death within 2 or 3 days. Influenza encephalopathy reported in Japan is distinct from Reye syndrome, and one-fourth of patients exhibit bilateral thalamic necrosis on neuroimaging. Similar encephalopathic symptoms probably occur in North America and European countries.