[A case of Hashimoto's encephalopathy associated with Graves' disease]

A 23-year-old woman with Graves' disease was first admitted to a hospital because of generalized convulsion, consciousness disturbance, and tachycardia. Investigations showed biochemical hyperthyroidism and positive thyroid binding inhibitory immunoglobulin (TBII). She was treated with anticonvulsant and antithyroid therapy. One month later the patient developed the second episode of generalized convulsion, followed by cognitive deficits especially concerning short-term memory, when she was transferred to our hospital. Although thyroid function was normalized at that time, anti-thyroid peroxidase (TPO) antibodies level were elevated to 5,850 U/ml in the serum, and 4.9 IU/ml in CSF. CSF protein was elevated to 133 mg/dl. Brain SPECT showed global decrease of cerebral perfusion, and EEG demonstrated diffuse slowing of the background rhythm without any signs of epileptic activity, although brain MRI was normal. Based on a diagnosis of Hashimoto's encephalopathy associated with Graves' disease, therapy with steroids was started, which definitely improved her clinical symptoms. Anti-TPO antibodies disappeared in CSF and decreased in the serum after the treatment. Hashimoto's encephalopathy should always be kept in mind in patients with Hashimoto's disease and Graves' disease.