In this condition factsheet:
The Facts on Parkinson's Disease
Parkinson's disease is a slowly progressing disease of the nervous system that causes people to lose control over their muscles.
About 1 in 250 people over the age of 40, and about 1 in 100 people aged 65 or older, are affected by Parkinson's disease. Although the average age of onset is 57, Parkinson's occasionally appears in childhood. Men are more likely to develop Parkinson's than women.
Parkinson's is not a fatal condition. However, the end stage of the disease can lead to pneumonia, choking, severe depression, and death.
Causes of Parkinson's Disease
Although the brain cells that control movement (the motor neurons) are located along the top of the brain, they rely on a chemical called dopamine that's manufactured in an area of the brain called the substantia nigra.
In Parkinson's, dopamine-producing cells in the substantia nigra are lost. In most cases, we don't know why. Primary Parkinsonism is the diagnosis in the majority of cases where the doctor doesn't know why these cells are dying. One thing researchers do know is that in the majority of people with Parkinson's disease, a protein called synuclein accumulates to form protein deposits called Lewy bodies. Researchers believe that Parkinson's disease is a late complication of protein accumulation, where the protein can accumulate in other areas of the brain and in the intestinal tract.
Secondary Parkinsonism is due to some disease (e.g., nervous system conditions, heart disease, brain tumours, viruses) or chemical interfering with or damaging dopamine-producing cells in the brainstem. The most common cause is side effects of medication for other problems. Medications that can cause secondary Parkinsonism include:
- haloperidol* and other medications used to treat hallucinations
- metoclopramide (an antinausea medication)
Less common causes of secondary Parkinsonism include poisoning by carbon monoxide or manganese (a type of mineral), lesions and tumours in the brainstem, and a rare illicit drug called N-MPTP. An outbreak between 1918 and 1924 of a disease called von Economo's encephalitis left thousands of people across North America with Parkinson's.
A number of genetic mutations have recently been identified, suggesting that Parkinson's may run in some families. However, a major US twin study suggested that environment plays a larger role than inheritance. The current consensus is that genetic factors are dominant only in Parkinson's that appears before age 50.
Symptoms and Complications of Parkinson's Disease
The main symptoms of Parkinson's disease are:
- tremor, shaking, or trembling
- slowed movement
- stiff or rigid arms, legs, and trunk
- balance trouble that can lead to falls
Tremors only appear at rest and not when the person is making purposeful movements. Later, the arms and legs may be affected. About 15% of people with Parkinson's don't have tremors; rather, they find their limbs or other areas turning stiff or rigid. Most people, however, have both. The rigidity becomes worse as the disease progresses, making movement difficult.
Slowed movement is another symptom of Parkinson's disease. People may also experience trouble starting movement (e.g., starting to walk) and will move much slower than normal. When balance reflexes become impaired, it makes it difficult to turn quickly or negotiate narrow corners and doorways.
Other symptoms that are common in Parkinson's (though no one person will have all of them) include:
- abnormal walking
- decreased arm swing
- excessive salivation
- feelings of depression or anxiety
- increase in dandruff or oily skin
- lack of facial expression (hypomimia)
- less frequent blinking and swallowing
- lowered voice volume (hypophonia)
- slight foot drag
- small cramped handwriting (micrographia)
- stooped posture
- trouble sleeping
- decreased sense of smell
- muscle aches
Depression is common in people with Parkinson's. Psychotic symptoms, such as visual or auditory hallucinations, may occur in up to 50% of cases. People with Parkinson's also run a higher risk of developing dementia, which often results in problems with memory or concentration similar to what is seen in Alzheimer's disease.