Hashimoto's encephalopathy is a rare disease, with a reported prevalence of 2.1 per 100 000. Clinical manifestations include confusion, decreased state of consciousness, cognitive deficit, seizures, myoclonus, ataxia, and focal neurological deficits. Due to the wide variety of signs and symptoms, clinical diagnostic suspicion is essential. Diagnosis is based on three pillars: the presence of neurological clinical manifestations after ruling out other causes of encephalopathy. 2) Presence of increased antithyroid antibodies. 3) Significant clinical improvement after the administration of immunomodulation. The treatment of Hashimoto's encephalopathy pursues two objectives: to control the autoimmune process and to control the complications of the disease. Although in most cases recovery is complete with treatment, the risk of relapse can range from 12.5 to 40% in follow-ups to 2 years.