[Electrophysiological tests in a case of Hashimoto's encephalopathy].

Hashimoto's encephalopathy is regarded as an autoimmune disorder that appears in patients with anti thyroid antibodies. The thyroid function tests of the patients are not necessarily abnormal, which sometimes makes the diagnosis difficult. Since most of the patients show consciousness disturbance, psychiatric symptoms, and cognitive function decline, Hashimoto's encephalopathy must be distinguished from other disorders showing dementia. We performed the electrophysiological tests on a 38 year old woman with Hashimoto's encephalopathy. Event-related potentials showed impaired cognitive function, and somatosensory evoked potentials and motor evoked potentials showed abnormalities of central nervous system. Although the steroid pulse therapy with the following oral prednisolone treatment resulted in the remission of symptoms, results of electrophysiological tests remained unimproved. Thus the disease course of the patient should carefully be monitored, and the clinical importance of these tests in Hashimoto's encephalopathy may be further considered.