Hashimoto’s encephalopathy (HE) is currently considered to be a rare recurrent or progressive encephalopathy mediated by autoimmunity, closely related to Hashimoto’s thyroiditis, and first reported by Brain in 1966. It is clinically characterized by acute or subacute episodes of confusion or psychotic-like episodes with varying degrees of cognitive dysfunction, confusion, muscle clonus or convulsions. Patients usually have very high titers of antithyroid peroxidase autoantibodies (TPOAb) in their blood. The disease responds well to glucocorticoid therapy and is therefore also known as steroid response encephalopathy (SRE). 1. Etiology and pathogenesis: The etiology and pathogenesis of HE are not known, and although some patients have subclinical or clinical hypothyroidism, changes in thyroid function alone are not a direct cause of HE. Similarly, although it is not certain that high titers of thyroid autoantibodies are associated with nerve damage, it is basically clear that autoimmunity is the culprit of HE. In contrast, primary demyelination, vasculitis, immune complex deposition and direct antibody-mediated neuronal damage are possible pathogenic mechanisms. 2. Clinical manifestations: The incidence of HE is significantly higher in women than in men, with a male-to-female ratio of about 1:4 and a relatively high prevalence in the middle-aged population. The clinical manifestations are complex and non-specific, and the proportion of HE patients with other autoimmune diseases such as systemic lupus erythematosus, dry syndrome, and type 1 diabetes mellitus is significantly higher. Both types may present with seizures, myoclonus, tremor, coma, extrapyramidal symptoms and cerebellar ataxia. About half of the patients with HE will present with nonspecific changes on MRI. 3. Diagnosis: Because of the absence of specific symptoms, signs, and ancillary findings in HE, the rate of clinical underdiagnosis and misdiagnosis is high. Therefore, for unexplained encephalopathy, the possibility of HE should be thought of and thyroid autoantibody testing should be performed. In 2007, Mocelli suggested that the diagnosis of HE should be based on at least the following criteria: (1) an encephalopathy with impaired cognitive function or neuropsychiatric symptoms; (2) a significantly elevated titer of antithyroid antibodies; and (3) laboratory and imaging tests that exclude infectious, toxic, metabolic, neoplastic, and paraneoplastic etiologies. In addition, EEG showing diffuse slow waves, increased protein content in cerebrospinal fluid, non-specific changes in cranial MRI, and good response to glucocorticoid therapy are helpful for diagnosis. However, no response to hormone therapy does not exclude HE. 4. Treatment: In acute or subacute attacks of HE, high-dose glucocorticoid shock therapy should be used, such as prednisone 50-150 mg/d orally for 10-15 d, or intravenous methylprednisolone 1 g/d for 3-7 d, followed by oral prednisone therapy. The total duration of treatment should be 6 months to 2 years to prevent recurrence. For patients with recurrent seizures, ineffective glucocorticoids alone or unable to apply them routinely due to side effects, other immunotherapies may be used. Patients with hypothyroidism or seizures should be treated with thyroid hormones and antiepileptic drugs accordingly.