Acute influenza virus-associated encephalitis and encephalopathy in adults: a challenging diagnosis

Abstract

Background: Acute influenza-associated encephalopathy/encephalitis (IAE) in adults is a rare but well-known complication of influenza virus infection. The diagnosis is difficult to make due to the absence of distinctive clinical symptoms and validated diagnostic criteria. We present an illustrative case and a case review on acute IAE in adults.Methods: We performed a Medline search of the English literature using the terms influenz*, encephal* and adult, and constructed a database of detailed descriptions of patients with influenza virus infection with influenza-like symptoms at the onset of neurological symptoms.Results: A total of 44 patients were included. Confusion and seizures were the most prevalent neurological symptoms, present in 12 (27 %) and 10 (23 %) patients, respectively. Magnetic resonance imaging (MRI) was performed in 21 patients and anomalies were found in 13 (62 %), with lesions located throughout the brain. Influenza virus RNA was detected in cerebrospinal fluid (CSF) in 5 (16 %) of 32 patients. Eight (18 %) of the forty-four patients died. The benefits of antiviral and immunomodulatory therapy have not been well studied.Discussion: Our results show that many different neurological symptoms can be present in patients with acute onset IAE. Therefore, the diagnosis should be considered in patients with fever and neurological symptoms, especially during the influenza season. Laboratory diagnosis consists of demonstration of influenza virus RNA in brain tissue, CSF or respiratory samples, and demonstration of intrathecal antibody production against influenza virus. The presence of brain lesions in MRI and influenza virus in CSF appear to be of prognostic value.

Influenza B-related meningoencephalitis in adults

“…CSF samples in previous case reports were negative for influenza B virus, as in our patient. Meijer et al reported that influenza virus RNA in CSF was detected in 16% of cases, which may be explained by viral CSF concentrations of influenza virus being too low for detection by regular diagnostic tests 10. Otherwise, CSF may reveal lymphocytosis or raised protein, which was similar to our patient.…”

Acute-onset Flu Encephalopathy in an Adolescent Female

“…Her normal magnetic resonance imaging (MRI) and her subsequent full recovery are consistent with the prior finding, in adult patients, that a normal MRI is of prognostic value [3]. …”

“…Influenza is difficult to detect on cerebral spinal fluid PCRs and is only positive in approximately 16% of patients [3]. After excluding immediate life threats with a typical AMS evaluation (including CT/LP, toxicologic studies, evaluation for trauma), additional diagnostic testing for flu encephalopathy typically includes an MRI/MRA and EEG.…”

“…The syndrome has been best described in Asian countries and less often in Caucasian children [2]. The incidence of the disease is low (estimated at 0.21 per million cases), but it has globally increased since the hemagglutinin one neuraminidase one (H1N1) epidemic [3]. Though the pathophysiology is still not well-understood, it has been ascribed to serum pro-inflammatory cytokine burden [4-5].…”

Prevention and treatment of respiratory viral infections: Presentations on antivirals, traditional therapies and host-directed interventions at the 5th ISIRV Antiviral Group conference

“…Oseltamivir treatment for influenza is associated with significant decrease in the risk of recurrent cardiovascular events in subjects with a history of cardiovascular disease (Casscells et al, 2009). Neurological complications of influenza include febrile convulsion, encephalitis, encephalopathy and Guillain Barre Syndrome (Meijer et al, 2016;Tomas et al, 2015). Influenza associated encephalitis is more common in pediatric patients but has been reported in 4% of hospitalized adults, with a mortality rate of 21% while 25% of patients may have residual neurological deficits (Sellers et al, 2017).…”