Parkinson's Disease

Parkinson's disease is the second most common neurodegenerative disorder and the most common movement disorder. It is characterized by progressive loss of muscle control, which leads to trembling of the limbs and head while at rest, stiffness, slowness, and impaired balance. As symptoms worsen, it may become difficult to walk, talk, and complete simple tasks.

The progression of Parkinson's disease and the degree of impairment vary from individual to individual. Many people with Parkinson's disease live long productive lives, whereas others become disabled much more quickly. Premature death is usually due to complications such as falling-related injuries or pneumonia.

In the United States, about 1 million people are affected by Parkinson's disease and worldwide about 5 million. Most individuals who develop Parkinson's disease are 60 years of age or older. Parkinson's disease occurs in approximately 1% of individuals aged 60 years and in about 4% of those aged 80 years. Since overall life expectancy is rising, the number of individuals with Parkinson's disease will increase in the future. Adult-onset Parkinson's disease is most common, but early-onset Parkinson's disease (onset between 21-40 years), and juvenile-onset Parkinson's disease (onset before age 21) also exist.

Descriptions of Parkinson's disease date back as far as 5000 BC. Around that time, an ancient Indian civilization called the disorder Kampavata and treated it with the seeds of a plant containing therapeutic levels of what is today known as levodopa. Parkinson's disease was named after the British doctor James Parkinson, who in 1817 first described the disorder in great detail as "shaking palsy."

A substance called dopamine acts as a messenger between two brain areas - the substantia nigra and the corpus striatum - to produce smooth, controlled movements. Most of the movement-related symptoms of Parkinson's disease are caused by a lack of dopamine due to the loss of dopamine-producing cells in the substantia nigra. When the amount of dopamine is too low, communication between the substantia nigra and corpus striatum becomes ineffective, and movement becomes impaired; the greater the loss of dopamine, the worse the movement-related symptoms. Other cells in the brain also degenerate to some degree and may contribute to non-movement related symptoms of Parkinson's disease.

Although it is well known that lack of dopamine causes the motor symptoms of Parkinson's disease, it is not clear why the dopamine-producing brain cells deteriorate. Genetic and pathological studies have revealed that various dysfunctional cellular processes, inflammation, and stress can all contribute to cell damage. In addition, abnormal clumps called Lewy bodies, which contain the protein alpha-synuclein, are found in many brain cells of individuals with Parkinson's disease. The function of these clumps in regards to Parkinson's disease is not understood. In general, scientists suspect that dopamine loss is due to a combination of genetic and environmental factors.

Source: MedicineNet.com
http://www.medicinenet.com/parkinsons_disease/article.htm