It is caused by the loss of specialised nerve cells and their connections within certain areas of the brain. These cells produce chemicals called dopamine, which is involved in many functions (relating to movement, control and co-ordination) and noradrenaline, a hormone similar to adrenaline.

In addition to losing these specialised cells, tiny grainy structures called Lewy bodies are found in the brain neurons of people with Parkinson's. Lewy bodies are small spherical deposits of proteins and are also found in a kind of dementia that becomes more common as we get older (Dementia with Lewy bodies).

Is Parkinson's hereditary?

There is no conclusive proof that Parkinson's is hereditary - however there does seem to be a genetic susceptibility to the disease.

People with siblings or parents who developed Parkinson's at a younger age have a higher risk of developing it themselves. This suggests it could be passed on in some families - if for example they both come into contact with other factors such as a certain kind of food, or a particular chemical or virus. In which case environmental and lifestyle factors will interact with the genetic susceptibility, to trigger the development of Parkinson's.

Relatives of people who were older when they developed the disease have the same average risk for Parkinson's as the rest of the population.