Influenza-associated central nervous system dysfunction: a literature review.

CONTEXT: Influenza is a viral pathogen that imposes an under-recognized burden of central nervous system (CNS) disease.
OBJECTIVE: To describe the epidemiology, clinical features and etiology of the CNS disease entities associated with influenza. DATA SOURCES: English-language publications from MEDLINE. DATA EXTRACTION: Articles were identified using "influenza, human"[Mesh] AND "nervous system diseases"[Mesh] and screened for inclusion based on relevance and scientific rigor.
RESULTS: Febrile seizure is the most frequently encountered influenza-associated CNS complication, with one in five children hospitalized with influenza experiencing one or more events. In most instances, symptoms resolve without neurological sequelae, although the risk for subsequent afebrile seizure may be increased. Influenza-associated encephalitis/encephalopathy is a less common but potentially more serious complication that is widely reported in Japanese populations, although cases from other East Asian countries, North America, and Europe have been described. Clinical manifestations are diverse, and typically involve febrile seizures and abnormal behaviors in mild cases, with rapid evolution through decreased consciousness to coma in severe forms. In cases of serious disease, the prognosis is often poor, with outcomes including death or severe neurological sequelae. Influenza is also a known trigger for a number of rarely encountered, yet often serious, CNS diseases, including the encephalopathic condition of Reye's syndrome, the peripheral neuropathy known as Guillain-Barré syndrome, and the lesser known complaints of Kleine-Levin syndrome and post-encephalitic Parkinson's disease.
CONCLUSIONS: Influenza imposes a sizeable burden of CNS disease. Increased awareness and monitoring of CNS function is indicated, especially in infants and young children.