Parkinson's disease is a slow, progressive, chronic condition involving tremor, muscle rigidity and impaired movement. It is caused by the accumulation of alpha-synuclein in the brain in the form of Lewy bodies.
The disease affects regions of the brain that regulate involuntary functions such as blood pressure and heart activity. Dementia occurs in about 20 percent of cases. It affects 50 percent more men than women.
These structures are enervated by dopamine. Parkinsons patients lose 60 to 80 percent or more of dopamine producing cells in the substantia nigra, a pigmented section of the midbrain, by the time symptoms appear. The disease is caused by death of dopamine producing neurons.