[Hashimoto's encephalopathy with bilateral pallidal lesions presenting memory disturbance and executive dysfunction]

A 76-year-old man began to mistake his family for another person, and fall asleep easily while watching TV. He was treated with donepezil but without any effect. He was referred to our hospital on June. On admission, his consciousness was alert. Cranial nerves and motor functions were normal, but pathological reflexes were positive bilaterally. Serological examinations revealed high titers of antibodies against thyroglobulin and TPO, and antibody against alpha-enolase was positive. Total protein level in CSF was 40 mg/dl and cell counts were normal. On MRI, localized symmetrical lesions were observed in bilateral pallidum to genu of internal capsule. SPECT revealed hypoperfusion areas in bilateral striate bodies and frontal lobes. Neuropsychological examinations indicated impairment of executive function and procedural memory. The diagnosis of Hashimoto's encephalopathy was made and we treated the patient with oral prednisolone 60 mg/day followed by gradual tapering. After the treatment, clinical symptom as well as neuropsychological function improved. Neuropsychological impairment in this case was probably due to the disconnection of the thalamo-frontal projection. This case provides interesting suggestions that Hashimoto's encephalopathy may present with vasculitic infarctions in bilateral MCA perforators, and that this disease should be included in one of the differential diagnoses of cerebral infarctions of unknown etiology.