Dementia is an umbrella term. It describes the symptoms that occur when the brain is affected by certain diseases or conditions. There are many different types of dementia although some are far more common than others. They are often named according to the pathology that has caused the dementia. Some of the more common types include: Alzheimer's disease, Vascular dementia, Dementia with Lewy bodies, Fronto-temporal dementia, Creutzfeldt-Jakob disease and Korsakoff's syndrome.