Central Nervous System Manifestations in Pediatric Patients With Influenza A H1N1 Infection During the 2009 Pandemic

BACKGROUND: A novel H1N1 influenza A virus (A(H1N1)pdm09) particularly affected individuals <24 years of age during the 2009 pandemic. This study sought to better understand the risks and outcomes of central nervous system complications associated with pandemic influenza in the pediatric population. METHODS: Retrospective review of patients with laboratory-confirmed influenza A(H1N1)pdm09 infection and central nervous system manifestations at Texas Children's Hospital between April 2009 and June 2010. RESULTS: Among 365 patients with influenza A(H1N1)pdm09, 32 (8.8%) had central nervous system manifestations at a median age of 4 years. Eight (25.0%) were previously healthy, and 12 (37.5%) had neurological pre-existing conditions. Of the 32 cases of influenza with neurological complications, seizure (n = 17; 53.1%) was the most common central nervous system manifestation, followed by encephalitis (n = 4; 12.5%), meningitis (n = 4; 12.5%), encephalopathy (n = 3; 9.4%), meningismus (n = 3; 9.4%), focal hemorrhagic brain lesions (n = 2; 6.3%), brain infarction (n = 1; 3.1%), and sensorineural hearing loss (n = 1; 3.1%). Two patients demonstrated two or more types of central nervous system complications. One patient had abnormal cerebrospinal fluid with pleocytosis. Almost two thirds of the children with central nervous system manifestations required intensive care unit admission and nearly half required mechanical ventilation. There were no deaths. CONCLUSIONS: Patients with pre-existing neurological conditions were at greater risk for central nervous system manifestations during pandemic influenza infection. Patients with central nervous system manifestations were more likely to experience severe illness, characterized by intensive care unit admission and mechanical ventilation, although overall outcomes were good. Influenza prevention in patients with underlying medical conditions, particularly those with neurological conditions, is important.