Until recently, influenza-associated acute encephalopathy (IAE) had been rare in Europe and the United States. Recently, however, some investigators from these regions have reported on IAE. This severe complication of influenza is more common in Japan and is often fatal. The mortality rate is 30% and the rate of severe neurological sequelae is 30%. Since 2002, we have included intracranial pressure (ICP) monitoring in the management of infants with IAE in our center. This report summarizes our experience with ICP monitoring of IAE.
We describe four infants aged 1–5 years (two boys and two girls) who were pyrexial and comatose or who had convulsions. Three were healthy prior to admission but one had a craniopharyngioma. Antibodies to influenza A virus were detected in all four patients. ICP monitoring was started as soon as possible after admission.
The patients' cerebral perfusion pressure (CPP) was maintained above 50 mmHg. In three cases, the ICP was maintained below 25 mmHg. In these cases, the ICP was controlled with antipyretic therapy and pentobarbital infusion. In each of these cases, a computerised tomography (CT) scan of the brain showed bilateral thalamic hemorrhage and slight edema on the day of admission. In the other patient, the ICP suddenly increased to more than 50 mmHg, and a vasoconstrictor infusion (noradrenaline 0.5 μg/kg/min) was needed to maintain the CPP on the second hospital day. The brain CT and magnetic resonance imaging (MRI) demonstrated severe cortical brain edema, similar to that described in the hemorrhagic shock and encephalopathy syndrome (HSES) in Europe. All the patients survived; two made remarkable recoveries, including the patient who needed the vasoconstrictor infusion.
Before instituting ICP monitoring, it was difficult to determine the most appropriate therapy for severe IAE and survivors usually had significant neurological sequelae. (1) The control of CPP in patients with IAE is just as important as it is in the management of patients with severe head injuries. (2) Based on the ICP, the CT and MRI scans, IAE could be divided into two groups. (3) One type of IAE seen in Japan may be related to the HSES described in Europe.