[A case of Hashimoto's encephalopathy showing improvement in higher brain functions after a low-dose steroid therapy].

Here, we describe a case involving an 83-year-old woman who was admitted to our hospital for rehabilitation after pseudogout treatment. She had temporal and spatial disorientation. Neuropsychological assessment revealed frontal dysfunction, memory impairment, and executive dysfunction, in addition to general cognitive impairment. Subsequent laboratory examination revealed euthyroid status and elevated titers of anti-thyroid autoantibodies. MRI of the brain revealed no abnormal finding. However, electroencephalography revealed diffuse slowness. We diagnosed Hashimoto's encephalopathy on the basis of the clinical symptoms and laboratory findings. Administration of low-dose prednisolone (5 mg/day) alleviated general cognitive impairment and the laboratory findings; however, memory impairment and construction disorder remained. Previous studies suggest that the characteristics and clinical course of higher brain-function disorder associated with Hashimoto's encephalopathy vary on an individual basis, wherein some patients may respond well to low-dose steroid therapy. Here, we also encountered such a case, that showed good response to a low-dose steroid therapy.