Hyperacute reversible encephalopathy related to cytokine storm following influenza vaccine

ABSTRACT

Case Report A 62-year-old previously healthy male presented to the ED for confusion and single episode of epilepsy. A week earlier he received influenza vaccine. At admission, he had fever and agitation without meningeal irritation or neurological focal signs. Diagnostic tests including brain contrast-enhanced CT scan, MRI, nasopharyngeal SARS-CoV-2 swabs and lumbar puncture resulted unremarkable except for slightly increased CRP and increase of CSF and serum IL-6. On the 3°day, after hydration, steroids and antibiotic therapy, the patient presented a normal mental status, though amnesic for the previous 72 hours. A EEG on the 5°day and serum levels of IL-6 on the 8°day were normal. The patient was discharged at 10°day in good clinical conditions. Discussion: The acute onset after vaccination in absence of other documented etiologies, the overproduction of intrathecal neuroinflammatory mediators, the downward trend of cytokines and the prompt recovery after corticosteroid therapy, seem the typical picture of a brain dysfunction associated to cytokine storm. Recently, a unifying definition of cytokine storm-associated encephalopathy (CySE) was proposed. CySE origins from the massive release of cytokines promoting blood-brain barrier disruption and microglia/ astrocyte activation which support neuroinflammation in a synergistic act. Conclusions: We documented the first hyperacute reversible encephalopathy following influenza vaccination, suggesting cytokine storm as its causative mechanism, and highlighting the need to deepen our knowledge on this immune-mediated phenomenon.