Neurologic and Muscular Complications of the 2009 Influenza A (H1N1) Pandemic

Abstract

In the spring of 2009 a new triple-reassortant of influenza A (H1N1) virus appeared in Mexico and rapidly spread around the world, becoming a pandemic that primarily infected children and uncommonly older adults. Accompanying the pandemic were associated neurologic and muscular syndromes that affected primarily children and included febrile seizures, encephalopathy/encephalitis with or without seizures, delirium, focal neurologic syndromes, Guillain-Barré syndrome, myositis, and myocarditis. Neither the frequency nor the severity of these syndromes appears different from those recognized during periods of infections of previous influenza A viruses. I review the clinical, laboratory, neuroimaging, and pathologic characteristics of the associated syndromes appearing in the first wave of the pandemic, compare them to similar cases occurring in previous years, and explore several theories of pathogenesis.

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

“…Influenza-related neurological complications are rare in immunocompetent adults with variable clinical signs and pathology. These complications include encephalitis, Reye syndrome, GuillainBarré syndrome, transverse myelitis and acute disseminated encephalomyelitis (ADEM) [3]. In March 2010, almost all countries reported cases of influenza A (H1N1) and more than 17,700 deaths (laboratory confirmed cases) had been documented [1].…”

Pediatric neurological complications associated with the A(H1N1)pdm09 influenza infection

“…Febrile seizure was the most frequent complication in our study in accordance with previous studies reporting a higher frequency for influenza A positive children than those with other respiratory viruses. 10,22 In regards to our results, we particularly would like to underline the occurrence of uncommon and severe INC: a case of vertebro-basilar ischemic stroke leading to a locked-in syndrome, and a severe case of encephalopathy with necrotizing injuries and refractory intracranial hypertension leading to death in a child who had already presented with encephalitic symptoms during two previous ILIs. At the time being, it is unclear if this child had recurrent events of ANE or successive decompensations of a mitochondrial disorder in the context of ILI.…”

“…4,5 During the 2009 A(H1N1) pandemic, neurological presentations were also reported in few series and in many case reports worldwide. [6][7][8][9][10] Severe cases with high morbidity and mortality have been described such as cerebral injuries, 11 acute necrotizing encephalopathy (ANE) 12 or intracranial hypertension. 13 In France, a single pandemic wave was observed between week 43 and 52/2009 with a peak at week 48.…”

Guillain–Barré syndrome associated with the D222E variant of the 2009 pandemic influenza A (H1N1) virus: Case report and review of the literature

“…Davies reviewed the characteristics of the associated neurological syndromes appearing in the first wave of the pandemic. The spectrum of central nervous system complications included, besides seizures, encephalopathy syndrome, delirium, acute myositis and myocarditis, and one case of acute necrotizing encephalopathy which had a fatal outcome [17]. Despite great concern prompted by memories of the 1976 influenza A/H1N1 outbreak and the US mass vaccination programme, which was stopped because of the emergence of increasing cases of GBS among vaccine recipients, only few cases of influenza A(H1N1)2009-related GBS have been reported to date [11,12].…”