The most common clinical signs include unexplained or epilepsy-like seizures resistant to anti-convulsive treatment, confusion, headaches, hallucinations, stroke-like episodes, coma, impairment of cognitive function, behavioral and mood disturbance, focal neurological deficits, disturbance of consciousness, ataxia, and presenile dementia, together with the presence of high thyroid antibody levels, especially against thyroperoxidase (TPOab). This evidence concerns the gene TPO and dementia.