The Cause of Parkinson's Disease

What causes Parkinson's

The exact cause of Parkinson’s disease is unknown. Some researchers put it down to genetics, others blame the environment and some believe it could be viral. Or it could be a combination of these factors. The jury’s still out.

What the scientists generally do agree on is that the symptoms of Parkinson’s occur because deficiency of dopamine in the brain. The main area affected is a small part of the brain called the substantia nigra which transmits messages via neurotransmitters between the brain and nerve cells before passing them onto the muscles. Dopamine is one of these neurotransmitters.

For reasons that baffle researchers, the nerve cells in the substantia nigra become damaged and degenerate and this reduces the amount of dopamine available to the body. With a deficit of dopamine the nerve cells can’t function properly and messages don’t get through to the muscles. The lines of communication become progressively weaker until the brain can no longer control muscle movement effectively.

Studies have shown that people with Parkinson’s have lost about 80% of dopamine producing cells. But why does this happen in some people and not in others?

One theory is that free radicals, which are potentially damaging molecules created by the body’s normal chemical reactions, could lead to the destruction of nerve cells. Free radicals react with other molecules in a process called oxidation. Normally this damage is kept under control by antioxidant chemicals. But certain environmental factors such as pollution, radiation and cigarette smoke are believed to feed the production of these free radicals.

Clinical trials have revealed that people with Parkinson’s disease have very high levels of damaging iron in the substantia nigra and low levels of the protein ferritin which would normally protect the brain by surrounding the iron and isolating it. It’s what known in medical circles as an “oxidative mechanism.”

Could the Cause lie in our Genes?

Genetics could also play a part. In rare cases some families have been found to have a very high incidence of the disease. In Italy back in the 1980s, one family was thought to have inherited Parkinson’s. A blood test among family members revealed a common mutation of a gene called “alpha synuclein.” However, with very few exceptions, this wasn’t found present in other Parkinson’s disease patients.

Geneticists have discovered that someone with Parkinson’s is three times more likely than an unaffected person to have a close relative with the disease. Having a parent with the disease increases your chance of developing it from 2% to 6%. The number of cases like this is very few and no single gene has been found to be the cause.

Some people could have a genetic susceptibility to environmental risk factors such as pesticides or industrial metals. This theory is based on evidence that there are a number of toxins, such as the industrial chemical MPTP, which can rapidly induce Parkinson type symptoms.

Or Parkinson’s could simply be age related in some people. Research has found that as some people get older the natural wearing-out of the dopamine producing neurons speeds up. Once again the cause is a mystery.

Over the past decade many physicians have concluded that the cause of Parkinson’s involves a combination of the above factors. Research is ongoing because pinpointing the exact cause or causes is crucial to finding a way to prevent and cure the disease.


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