Muhammad Ali in 1970. (Associated Press)

There's nothing like the involvement of a celebrity to raise the profile of a disease. In 1984, one of the most recognizable people on the planet was diagnosed with Parkinson's disease. Muhammad Ali was 42 at the time.

A report by the Canadian Institute for Health Information estimates that neurological conditions — like stroke, Alzheimer's and Parkinson's — cost Canada nearly $9 billion a year. That's almost seven per cent of the total attributable cost of illness in Canada in 2000-01. The report warned that the health-care system may not be able to handle the increased burden of an aging population.

Here was a man who held the world heavyweight boxing title three times and just three years after his retirement as a pro athlete, he was diagnosed with a disease that most people associated with old people who are confined to wheelchairs.

When actor Michael J. Fox revealed in 1998 that he had been diagnosed with the Parkinson's seven years earlier, it underlined the fact that the disease could strike anyone — even in the prime of their lives. Fox was 30 when he was diagnosed — 37 when he made that diagnosis public.

He retired from his role in a highly-rated weekly television series in 2000 and began devoting much of his time to the Michael J. Fox Foundation for Parkinson's Research that he had set up.

Fox became an advocate for the search for a cure for the disease. During the 2006 mid-term U.S. election campaign, he came under fire from conservatives for his support of a Missouri measure that would provide constitutional protection for stem cell research. Many researchers believe that Parkinson's disease could well be treated using stem cell transplantation.

What is Parkinson's disease?

It is a degenerative brain disorder that was first identified by the English surgeon James Parkinson in 1817. The chronic neurological condition affects a small area of cells in the mid-brain known as the substantia nigra. Gradual degeneration of these cells causes a reduction in a vital chemical known as dopamine, which acts as a messenger between the brain cells that control movement.

The decrease in dopamine can produce one or more of the classic signs of the disease:

• Resting tremor on one side of the body (an arm or a leg shakes even when the muscles are at rest and you are completely relaxed).
• Generalized slowness of movement.
• Stiffness of limbs (rigidity).
• Gait or balance problems (postural dysfunction).

The disease progresses slowly — people often can function well for several years after they are diagnosed. But as it progresses, the disease's effects become more pronounced and — eventually — Parkinson's can leave people incapacitated.

What causes Parkinson's disease?

The cause remains unknown. What is known is what happens. Cells begin to die in the substantia nigra region of the brain. As the cells degenerate, the amount of dopamine in the brain decreases. Symptoms of Parkinson's appear when about 80 per cent of the cells have died. It's unclear why the cells die in some people, but not in others.

On Jan. 22, 2007, a team of researchers reported that there may be a strong link between Parkinson's and low levels of "bad" cholesterol. The researchers were so worried about the results that they launched a study to see if people taking statins — cholesterol-lowering drugs — were at higher risk of developing Parkinson's disease.

How common is Parkinson's?

It's estimated that approximately 100,000 Canadians have Parkinson's disease.

Are there risk factors?

Age is the major risk factor. Symptoms usually appear after 60, but they can show up in much younger people, although it is quite rare.

Parkinson's affects about one per cent of people over the age of 65 and about two per cent of those over 70. Around 15 per cent of cases are diagnosed in people under the age of 50.

Other risk factors include:

Heredity: if one or more of your relatives has the disease, the chance that you will develop it will increase — but your risk is still no more than five per cent.

Sex: men are more likely to develop Parkinson's than women.

Exposure to pesticides: ongoing exposure to pesticides and herbicides can increase your risk.

Reduced estrogen levels: menopausal women who do not receive hormone therapy and women who have had hysterectomies may face an increased risk.

How do I know if I have Parkinson's?

There is no definitive test that will confirm a case of Parkinson's. Research is increasingly looking at genetics in the search for what causes the disease.

In a study released on Jan. 12, 2007, researchers reported a pattern of abnormal functioning in 22 genes. The researchers hope the so-called molecular marker could eventually lead to a test to help diagnose the disease.

The diagnosis is based on your medical history, observation of your symptoms and a neurological examination.

In older people, signs and symptoms of the disease can be dismissed as the natural effects of aging.

Some other signs and symptoms of the disease include:

• Small, cramped handwriting.
• Lack of arm swing on the affected side.
• Decreased facial expression.
• Lowered voice volume.
• Feelings of depression or anxiety.
• Episodes of feeling "stuck in place" when trying to take a step.
• Slight foot drag on the affected side.
• Increase in dandruff or oily skin.
• Less frequent blinking and swallowing.
• Dementia also occurs in about half of Parkinson's patients and depression is common.

Is there a cure for Parkinson's

No, but it is treatable — and it isn't fatal. The goal of treatment is to maximize the patient's quality of life. Options include medication, physical therapy and surgery.

Many of the symptoms can be controlled through drugs. Levodopa has been the most frequently prescribed drug for Parkinson's since it was introduced in the 1960s. It is a natural substance found in plants and animals. It is converted into dopamine by nerve cells in the brain. The increase in dopamine may reverse many of the disabling symptoms of Parkinson's disease.

As the disease progresses, the levodopa generally becomes less effective and may have to be replaced by other drugs.

The goal of physical therapy is to help improve mobility, range of motion and muscle tone.

Surgery for Parkinson's patients is not as common as it used to be.

Thalamotomy has been used to reduce tremors in people with Parkinson's by destroying small amounts of tissue in the thalamus — a section of the brain used for relaying messages and transmitting sensations.

Pallidotomy uses an electric current to destroy a small amount of tissue in the pallidum — a part of the brain responsible for many symptoms of the disease. The procedure may reduce tremors, rigidity and slowed movement by interrupting the neural pathway between the pallidum and the thalamus.

In deep brain stimulation, a brain implant transmits electric pulses through a wire to tiny electrodes inserted deep within the brain. The brain centre targeted — the subthalamic nucleus — controls many aspects of motor function.

American researchers have also had some encouraging results using gene therapy. In a small trial, researchers used a virus to inject a gene directly into the brain cells of 11 men and one woman with Parkinson's with an average age of 58. They had severe Parkinson's for at least five years, and current therapies no longer worked for them.

The therapy was intended to calm the excessive firing of neurons that occurs in Parkinson's. The researchers said the participants showed some improvement within three months of the procedure. The researchers said gene therapy avoids implants, adjustments and risk of infection that come with deep-brain stimulation.

What are the complications from Parkinson's?

Among the major ones is depression — and it's not caused by the physical limitations that the disease may cause for the patient. Often, depression can occur months or years before a diagnosis of Parkinson's is made. It's believed the depression is due to underlying changes in the brain associated with the disease.

The medications prescribed for Parkinson's can also lead to several complications like involuntary twitching, hallucinations, fatigue and a drop in blood pressure.

Other problems can include difficulty chewing or swallowing, urinary incontinence or urinary retention, constipation, restless sleep and a decrease in sexual desire.

And dementia — a condition that can include memory loss, impaired judgment and personality changes — affects as many as half of all Parkinson's patients.