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A 51-year-old man developed acute disturbances in consciousness and psychiatric symptoms one month prior to admission. He was referred and admitted to the Department of Psychiatry of our hospital and transferred to the neurology department because diffuse white matter lesions were found on his brain during MRI. 123 I-IMP-SPECT showed extensive cerebral hypoperfusion mainly in the frontal lobes. Anti-Tg, anti-TPO, and anti-NAE antibodies were positive. These findings led to a diagnosis of Hashimoto's encephalopathy. The patient responded to steroid pulse therapy, high-dose steroid therapy, and intravenous immunoglobulin therapy, showing improvement in symptoms and imaging findings. Hashimoto's encephalopathy often presents with MRI findings similar to those of limbic encephalitis, when the patient presents with acute consciousness disturbance and psychiatric symptoms. However, this case showed diffuse white matter lesions, which may be clinically important for the differential diagnosis.

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.

Hashimoto's encephalopathy has been described as an autoimmune disorder which demonstrates favorable response to corticosteroid therapy. However, steroid-resistant cases which require additional treatment are frequently reported, and there is no consensus how such cases should be treated. We present a 69 years-old man, who progressed cognitive dysfunction in the past three months. Anti-thyroid and anti-NH 2 terminal of alpha-enolase antibodies were positive. Because initial corticosteroid therapy was ineffective, cyclophosphamide (CPA) pulse therapy was added, and his cognitive function was immediately improved. He had no relapse after tapering dose of corticosteroid for three years. CPA pulse therapy should be considered for steroid-resistant Hashimoto's encephalopathy.