Presenile dementia: a case of Hashimoto's encephalopathy.

Hashimoto's encephalopathy may present with a variety of neurological symptoms and signs, including myoclonus, epileptic seizures, disturbance of consciousness, psychosis, ataxia, and presenile dementia. This report is of a 57-year-old woman with a history of thyroid disease who was investigated for generalised seizures, rapid decline in cognitive function, increasing dependency, and gradual change in personality. High thyroid autoantibody titres confirmed the diagnosis of Hashimoto's encephalopathy and her symptoms improved with treatment with prednisolone. The differential diagnosis of presenile dementia, aetiology and pathogenesis of Hashimoto's encephalomyelitis, and treatment options are discussed. Hashimoto's encephalomyelitis should be considered in the differential diagnosis of presenile dementia, particularly in patients with a history of thyroid disease.