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What is Parkinson’s disease?

Parkinson's disease is a progressive neurological condition caused by a decrease in the number of nerve cells in the part of the basal ganglia of the brain (the substantia nigra), which is responsible for the coordination of movement. These nerve cells are responsible for the production of dopamine, and so there is consequently a decrease in the amount of dopamine available to the body.

The symptoms of Parkinson's disease appear when the level of dopamine falls below 20% of normal levels, causing a lack of coordination and control of body movement that often appears as a tremor, stiff muscles and joints, and/or difficulty moving. It can also cause difficulty with speech. The dopamine levels continue to fall slowly over many years. People with Parkinson's disease tend to move slowly, shuffling their feet, and find it difficult to initiate movement, and develop a mask-like facial expression.

Parkinson's disease is most common in the elderly (approximately 1 in 400 of the population over 65, and slightly more common in males than in females), and is caused by either atherosclerosis (hardening of the arteries) or unknown degenerative changes. When found in younger people, it is usually caused by poisoning or encephalitis (inflammation of the brain).

Reference: Clinically Oriented Anatomy, Moore

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