[Hashimoto's encephalopathy--case report and diagnostic issues in Japan].

We report a patient with Hashimoto's encephalopathy who showed remission and exacerbation 2 times, with a review of previously reported patients in Japan. A 54-year-old woman was admitted to our hospital for various symptoms, such as tremors of the bilateral upper limbs, psychiatric symptoms, consciousness disorder, and convulsion. Steroid pulse therapy and the subsequent oral maintenance therapy resulted in remission. There was no relapse. The patient was positive for anti-thyroid antibody. Electroencephalography showed diffuse slow waves. The responsiveness to steroids suggested Hashimoto's encephalopathy. According to previous studies, clinical symptoms, magnetic resonance imaging (MRI) findings, and the responsiveness to steroids are similar among steroid-reactive encephalopathy, non-herpetic limbic encephalitis, and Hashimoto's encephalopathy. Anti-thyroid antibody levels characteristically increased in patients with Hashimoto's encephalopathy. However, measurement of this parameter in patients with these diseases is rare. In patients with idiopathic encephalopathy/encephalitis, anti-thyroid antibody levels should be measured to facilitate accurate diagnosis.