Neurological Complications of Novel Influenza A (H1N1) pdm09 Infection: Report of Two Cases and a Systematic Review of the Literature

Background: Neurological complications of Influenza A (H1N1) pdm09 in adults are rarely reported in the literature. The aim of this study is to report a case of Influenza A (H1N1) pdm09 acute necrotizing encephalitis (ANE) and another case of acute hemorrhagic leukoencephalopathy (AHLE) and to review the neurological complications of this disorder in adults. Methods: We conducted a search on Medline, Ovid, EMBASE, ProQuest and PubMed databases using the key words (neurological complications of H1N1 in adults). We also added to the search results those articles which were not found in the search but exist in the literature under different search words. Only papers written in English published from March 2009 to December 2015 were included. Demographic data and clinical diagnosis of neurological complications and outcomes in adults including death, neurological sequalea or recovery after influenza A (H1N1) pdm09 infection have been reviewed. Results: we included 37 articles presenting a total of 261 adult patients with neurologic complications following Influenza A (H1N1) pdm09 infection. In addition, a case of influenza A (H1N1) pdm09 acute necrotizing encephalitis (ANE) and another case of acute hemorrhagic leukoencephalopathy (AHLE) arising from our own neurological practice were also included. Conclusion: In conclusion, this study demonstrates that influenza A (H1N1) pdm09 is both a pandemic and a seasonal (sporadic) disease. We speculate that most of the neurological complications are immune mediated and calling for further studies to test for the potential benefits of early steroids use in the disease. We are calling for an international collaboration and registry for Influenza A (H1N1) pdm09 infection.