A case of influenza A virus associated encephalopathy with bilateral thalamic hemorrhage

A three-year old girl was hospitalized in a semi-conscious state following a febrile convulsion. She did not recover despite treatment and died 16 days after admission. Influenza A virus (H3N2) was detected from a throat swab from the patient, and serum hemagglutinin-inhibiting antibodies to the virus elevated from less than 8 to 256. Brain CT revealed bilateral thalamic hemorrhage and peripheral low density. Subarachnoid hemorrhage was also observed thereafter. Based on clinical manifestations and neuroimaging, this patient was diagnosed as an atypical case of acute necrotizing encephalopathy associated with influenza A virus infection. Such rapid progressive encephalopathies may occur due to intracranial vascular injury including vasculitis or spasms. Although it is clear that influenza A virus triggered this case, we cannot confirm that it was a pathogen. Also, it might be advisable to consider other possible contributing factors such as drugs administered before hospitalization.