Deep within the human brain is the substantia nigra where a chemical called dopamine is made. (See image) This chemical helps send messages from the brain to the muscles. The substantia nigra deteriorates and less dopamine is produced as people get older. The difference in those with Parkinson disease is that the loss is much greater. As dopamine levels decrease, the person has increasing loss of muscle control. When dopamine is reduced by 70 to 80 per cent the symptoms of Parkinson disease appear.
The Parkinson Society of Southern Alberta
Calgary: Phone 403-243-9901
Toll-free Alberta only 1-800-561-1911
British Columbia Parkinson Disease Association
Vancouver: Phone 604-3240
Toll-free B.C. only 1-800-668-3330
Saskatchewan Parkinson's Disease Foundation
Saskatoon: Phone 306-966-8160
The Parkinson Foundation of Canada
(Supports chapters in Eastern Canada, including Manitoba)
Toll-free phone 1-800-565-3000
Internet web site: www.parkinson.ca
Other internet Web sites have useful information.
Parkinson disease becomes more common with increasing age and affects men and women almost equally. It does not seem to run in families but research is being done to determine if some people carry a gene that makes them more at risk of the disease. Research is also aimed at trying to learn if some factors in the environment may be involved in the cause of the disease.
People affected at an early age may only have one troublesome symptom such as a tremor. Even though this may be in just one limb, for someone who depends on that particular limb the effect can be devastating. The good news is younger people have a better opportunity to be candidates for surgery. Unfortunately, they also tend to progress to advanced disease at an earlier age.
The early symptoms of Parkinson disease are familiar to many people while some of the later ones are less well known.
Since there is no one drug that will help everyone, several may need to be tried, either alone or in combination. Some drugs are effective at first but lose their benefit over time. For this reason, and to reduce side effects, medication treatment usually is not started until the symptoms disrupt daily living.
One aim of medication treatment is to protect the neurons in the brain that produce dopamine. This is aimed at preventing further damage and slowing progression of the disease. Initial treatment is best done using the least potent drug at the lowest possible dose.
A medication called selegiline (Eldepryl™) holds dopamine at the nerve endings where it is needed to help relay brain messages. For some people this medication has delayed the need for additional drugs by 12 months or more. However, its use and safety remain controversial.
The medication that is most commonly used when additional drugs are needed is levodopa. This is a dopamine replacer. It is converted to dopamine within the brain. It is usually prescribed in combination with another medication which reduces the action of levodopa on nerve endings in the rest of the body. Thus, it has its effect just in the brain where it is needed. Sinemet™ or Prolopa ™ are the commonest of these combinations and the former is also available as a slow release preparation Sinemet CR™.
Within five years of starting levodopa about 50 per cent of people will have complications. The benefits from the drug can wear off, muscle movements may be difficult to control, the person may have periods where movement freezes, or a complication may occur called on-off phenomenon.
At this stage, the addition of a medication called a COMT inhibitor, such as Entacapone™, may help. This drug blocks an enzyme that breaks down levodopa thus prolonging its effect. There was another COMT inhibitor, Tolcapone ™ on the market but it was removed from circulation due to concerns over harm to the liver.
Drugs known as dopamine agonists, which prevent the destruction of levodopa (Requip™, Pramipexole ™, Parlodel™, Permax™), are frequently used as initial therapy. They are also used to supplement the action of levodopa. They do have side-effects and their benefits are not immediate. If the major symptom is tremor, Artane™ and Cogentin™ may be used.
These drugs are rarely given to older people, as side-effects are more common. A group of drugs called anti-oxidants are thought to protect the body against various diseases. Research has been done into possible beneficial effects of the anti-oxidants Vitamins C and E on Parkinson disease but these do not seem to slow progression of the disease.
Surgery used to be common before levodopa was available and it is being used more often again. With MRI scans that help pinpoint areas of the brain, and new techniques, there are improved options. However, risks of injury to the brain, long-term side effects (far greater in the elderly), and death must be weighed against the possible benefits. So far, these operations will only improve one side of the body, that opposite to the surgery.
Generally, surgery in the elderly tends to be for very advanced Parkinson disease that does not respond to medication. The ideal patient is young and has a long-standing one-sided tremor that does not respond to medication. There should be no health-related conditions that affect the person's fitness for surgery.
Thalotomy may stop the disabling tremors for some people. A thin wire is implanted in a part of the brain called the thalamus. This wire is connected to a stimulator similar to a heart pacemaker. When the stimulator is turned on, high frequencies stop the tremor. The stimulator is turned off at night. An advantage of the procedure is the fact that it does not destroy brain tissue.
Pallidotomy is done to ease the slowed movement and rigidity. Again a wire is used and placed deep within an area of the brain called the pallidum. The tissue at the tip of the wire is destroyed and the symptoms relieved. On the down side, this procedure does have the risk of causing a stroke or loss of vision.
Parkinson disease is at the centre of much research. One breakthrough has been the ability to perform surgical procedures on both sides of the brain. Another is experimental work being done to implant fetal tissue (that produces dopamine) into the brain to reduce the need for treatment with levodopa. There is hope that in the future, genetic changes can be made to cells so they produce dopamine. These altered cells will be implanted in the brain. New nuclear scans such as SPECT and PET are being studied and may increase the understanding of this disease and how to treat it.
If you or a loved one has Parkinson disease, there are a few hints to help with necessary adjustments in daily living.