Neurology of the H1N1 pandemic in Singapore: a nationwide case series of children and adults

Abstract

Neurologic complications have long been associated with influenza. A novel strain of influenza A (H1N1) first described in humans to have outbreak potential in 2009 in Mexico went on to become the first influenza pandemic of this century. We evaluated the neurologic complications of the novel influenza A (H1N1) 2009 in children and adults admitted to all public hospitals in Singapore during the influenza A (H1N1) 2009 pandemic between May 2009 and March 2010. All patients were positive for novel H1N1 infection and presented with neurologic symptoms prior to oseltamivir treatment. Ninety-eight patients (median age 6.6 years, range 0.4-62.6) were identified; 90 % were younger than 18 years; 32 % suffered from preexisting neurological, respiratory, or cardiac disease; and 66 % presented with seizures. Of those presenting with seizures, new onset seizures were the most common manifestation (n = 40, 61.5 %), followed by breakthrough seizures (n = 18, 27.7 %) and status epilepticus (n = 7, 10.8 %). Influenza-associated encephalopathy occurred in 20 %. The majority of children (n = 88) presented with seizures (n = 63, 71.6 %), encephalopathy (n = 19, 21.6 %), and syncope (n = 4, 4.5 %). Among adults, a wider range of neurological conditions were seen, with half of them presenting with an exacerbation of their underlying neurological disease. The neurological symptoms developed at a median of 2 days after the onset of systemic symptoms. The median length of hospital stay was 3 days, and 79 % were monitored in general wards. Neurologic complications associated with the novel influenza A (H1N1) 2009 strain were generally mild and had a good outcome. They occurred more frequently in patients with underlying neurological disorders. Seizures and encephalopathy were the most common manifestations, similar to other influenza virus strains.

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

“…While mostly diagnosed in children, neurological complications of pandemic influenza A (H1N1) pdm09 may also affect adults with occasional fatal consequences [6]. Neurological manifestations may affect any level of the neuraxis with varying severity and prognosis.…”

Neuroimaging in Zoonotic Outbreaks Affecting the Central Nervous System: Are We Fighting the Last War?

“…Notably, several reports described bilateral thalamic lesions, some with DWI high signal and focal hemorrhage, consistent with acute necrotizing encephalopathy (Fig 6), as well as patients with meningeal enhancement. 54,55 New-onset seizures and encephalopathy were found to commonly occur in patients with underlying neurologic disorders, with swelling of bilateral basal ganglia and thalami and cerebral edema and tonsillar herniation noted on MR imaging. 56 Overall, viruses remain the most likely class of organisms resulting in zoonotic outbreaks affecting the CNS.…”

“…Multifocal tiny white matter and others 52a Influenza A H1N1 virus Bilateral thalamus (with hemorrhage) and others 54a Meningeal enhancement 55…”

H1N1-Related Encephalitis in the Postpandemic Era

“…H1N1 often presents with a febrile disease with mild respiratory symptoms and rarely causes severe cardiac, pulmonary and neurologic complications (2). H1N1 causes neurologic complications such as encephalopathy, encephalitis, seizures, ischemic stroke, benign intracranial hypertension, myelitis, Reye syndrome, and Guillain-Barre syndrome, more than seasonal influenza (3,4).…”