Recurrent partial seizures with ictal yawning as atypical presentation of Hashimoto's encephalopathy (steroid-responsive encephalopathy associated with autoimmune thyroiditis)

Hashimoto's encephalopathy (HE), also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), is a rare condition whose pathogenesis is unknown, though autoimmune-mediated mechanisms are thought to be involved. The prevalent neurological manifestations of this disorder are epileptic seizures and psychocognitive disorders associated with EEG alterations. High anti-thyroid antibody titers (particularly in cerebrospinal fluid) and the effectiveness of steroid therapy are usually considered to be crucial elements in the diagnostic process. We describe a 19-year-old female patient who had been referred to the psychiatric unit because of behavioral disorders characterized predominantly by delirium with sexual content. She developed recurrent focal seizures characterized by atypical ictal semiology (repetitive forceful yawning) and a rare EEG pattern (recurrent seizures arising from the left temporal region without evident “encephalopathic” activity). The presence of anti-thyroperoxidase antibodies in her cerebrospinal fluid and a good response to steroids confirmed the diagnosis of HE. The atypical presentation in the case we describe appears to widen the electroclinical spectrum of HE and highlights its importance for differential diagnosis purposes in the neuropsychiatric setting.