Neurologic complications of 2009 influenza A (H1N1)

Each year, respiratory complications of seasonal influenza result in substantial morbidity and mortality. However, evidence continues to accrue suggesting that influenza illness is associated with severe neurologic complications, including the 2009 pandemic influenza A (H1N1) virus infection. In this issue of Neurology ®, Webster et al.1 describe 2 pediatric cases of neurologic illness associated with 2009 H1N1, both with favorable outcomes. Rare cases of influenza-associated neurologic complications have been reported for decades. “Acute encephalopathy” was reported in association with the devastating 1918 “Spanish” influenza A (H1N1) pandemic.2 Recognition of the association of salicylate ingestion in children with influenza and development of Reye syndrome has led to preventive efforts and a dramatic decrease in this complication.3 More recently, a wide range of other neurologic illnesses associated with influenza have been described, including posterior reversible encephalopathy, myelitis, stroke, acute necrotizing encephalitis, and seizures.4–6 However, sorting out a causal role of influenza virus in many of these conditions through careful clinicopathologic investigations combined with epidemiologic studies has been challenging. Much attention has focused on influenza-associated …