Dementia is among the most typical neurodegenerative diseases which specifically arise due to neuron death. It is now becoming evident that neurodegenerative diseases have a biochemical basis. Many neurodegenerative diseases are inherited. Their genes are known and DNA-based diagnosis (including prenatal diagnosis) is available. Loss of neurons is accompanied by specific histopathological findings such as Alzheimer's plaques and Lewy bodies. Some neurodegenerative diseases engage specific anatomical systems or adjoining sets of neurons.