Acute encephalopathy with pandemic (H1N1) 2009 virus infection.

OBJECTIVES

In April 2009, a novel influenza A (H1N1) pdm virus was identified in Mexico and spread quickly around the world. However, the clinical features of acute encephalopathy associated with 2009 pandemic influenza have not yet been elucidated.

METHODS

We treated 8 patients (3 boys and 5 girls) aged 4 to 11 years (average age, 8 y 3 months) with influenza virus-associated encephalopathy, who presented at our 2 hospitals between July 2009 and March 2010. We investigated the clinical characteristics, treatments, and outcomes in the patients.

RESULTS

In all patients, brain computed tomography showed mild to severe diffuse cerebral edema, and electroencephalography revealed diffuse high-voltage slow waves. They were all treated with oseltamivir and methylprednisolone pulse therapy. Six patients recovered without any sequelae; however, the remaining 2 had residual neurological sequelae. These 2 patients presented with severe disturbance of consciousness, and their central nervous system symptoms appeared within 12 hours after the onset of fever. One patient had periventricular leukomalacia and symptomatic epilepsy by perinatal brain hypoxia, and the other patient had 1 complex febrile and 2 febrile seizures.

CONCLUSIONS

This study showed that patients with influenza-associated encephalopathy caused by influenza A (H1N1) pdm infection were all older than those with seasonal influenza. Underlying neurological disease or history may be associated with poor prognosis.