Overview of Parkinson's Disease
Parkinson's disease is a chronic, progressive neurodegenerative movement disorder. Tremors, rigidity, slow movement (bradykinesia), poor balance, and difficulty walking (called parkinsonian gait) are characteristic primary symptoms of Parkinson's disease.
Idiopathic Parkinson's disease is the most common form of parkinsonism, which is a group of movement disorders that have similar features and symptoms. Parkinson's disease also is called idiopathic Parkinson's because the cause for the condition is unknown. In the other forms of parkinsonism, a cause is known or suspected.
Parkinson's results from the degeneration of nuclei in a number of dopamine-producing nerve cells in the brainstem. Dopamine is a neurotransmitter that stimulates motor neurons, which are nerve cells that control the muscles.
When dopamine production is depleted, the motor system nerves are unable to control movement and coordination. Parkinson's disease patients have lost 80 percent or more of their dopamine-producing cells by the time symptoms appear. In searching for a cause for Parkinson's disease, most of the attention has focused on areas of the brain called the substantia nigra and the locus coeruleus.