Parkinson's disease was first described in 1817 by an English physician, Sir James Parkinson. It belongs to the group of so-called "neurodegenerative" diseases. Its exact origin is still unknown despite much research. It is due to too early a loss of nerve cells (neurons) of a small structure located deep in the brain, called substantia nigra (or substantia nigra or locus niger). This region owes its name to the presence of a dark brown pigment: melanin (pigment identical to that of the skin). These neurons manufacture a neurotransmitter, dopamine, which is involved in controlling and carrying out many body movements, mainly so-called "automatic" movements. The decrease in dopamine is the cause of the three main motor signs of the disease: slowness of movement (akinesia), stiffness of the muscles (hypertonia), tremor. The main effect of medical treatment is to compensate for this brain dopamine deficit. However, it's not just motor skills that are affected. Other non-motor signs can appear more or less early. These are neurovegetative disorders (constipation, sweating, etc.), sensory disorders (pain, tingling, etc.) or neuropsychic disorders (anxiety, depression, attention difficulties, etc.).