[Hashimoto's encephalitis and sleep disorders].

Hashimoto's encephalitis is a rare cause of encephalitis which is improved by corticosteroid treatment. We report the case of a 42-year-old woman who developed progressive dementia associated with episodes of recurrent discorders of consciousness which rapidly improved with corticosteroids. During these episodes, no sleep activity was recorded on the holter EEG. These discorders were reversible with treatment and a normal EEG sleep pattern reappeared. At physical examination, Hashimoto's encephalitis can mimic Creutzfeld-Jakob disease. Systematic sleep-EEG recordings can be helpful for diagnosis of sleep disorders related Hashimoto's encephalitis. This case illustrates the importance of searching for antithyroid antibodies in patients with unexplained encephalitis.