Teaching NeuroImage: Claustrum Sign in Febrile Infection-Related Epilepsy Syndrome

A 40-year-old woman presented with acute encephalopathy and super-refractory status epilepticus 6 days after a febrile illness. An extensive diagnostic workup was negative. EEG and brain MRI showed right-predominant abnormalities, including claustrum T2/FLAIR hyperintensity, the so-called claustrum sign (Figures 1 and 2). This finding has been described in patients with febrile infection–related epilepsy syndrome,1 a subcategory of new-onset refractory status epilepticus triggered by cytokine storm.2 Because the claustrum sign has been reported also in other cytokine storm-associated disorders, including acute necrotizing encephalopathy, COVID-19-related encephalopathy, and immune effector cell-associated neurotoxicity syndrome,3 it may represent a specific marker of cytokine-mediated neuroinflammation.