Claustrum Sign in Hashimoto Encephalopathy Presenting With New Onset Refractory Status Epilepticus (NORSE): First Report of a Rare Phenotype.

The presence of the bilateral claustrum sign in new-onset refractory status epilepticus (NORSE) should prompt consideration of Hashimoto's encephalopathy, even without thyroid dysfunction. Early recognition and corticosteroid therapy can be lifesaving, emphasizing an autoimmune-inflammatory mechanism underlying this rare presentation.