Hashimoto's encephalopathy in the elderly: relationship to cognitive impairment.

Hashimoto's encephalopathy (HE) is a steroid-responsive encephalopathy associated with high titers of antithyroid antibodies. To date, 57 pediatric-, adult-, and elderly-onset cases have been described in the literature. The clinical picture is pleomorphic, and cognitive impairment is a frequently reported symptom. We report the case of a patient with slowly progressive cognitive impairment possibly caused by HE. The issue of the differential diagnosis with primary dementia is discussed. A review of cases of HE showing cognitive deterioration is also presented, and factors possibly related to characteristics of cognitive impairment and outcome after therapy are considered.