Parkinson's disease, which mostly affects older people but can occur at any age, results from the gradual degeneration of nerve cells in the portion of the midbrain that controls body movements. The first signs are likely to be barely noticeable -- a feeling of weakness or stiffness in one limb, perhaps, or a fine trembling of one hand when it is at rest. Eventually, the shaking worsens and spreads, muscles tend to stiffen, and balance and coordination deteriorate. Depression, cognitive issues, and other mental or emotional problems are common as well.

Parkinson's disease usually begins between the ages of 50 and 65, striking about 1% of the population in that age group; it is slightly more common in men than in women. Medication can treat its symptoms, and the disorder is not directly life-threatening.

• What Causes Parkinson's Disease?

Body movements are regulated by a portion of the brain called the basal ganglia, whose cells require a proper balance of two substances called dopamine and acetylcholine, both involved in the transmission of nerve impulses. In Parkinson's, cells that produce dopamine begin to degenerate, throwing off the balance of these two neurotransmitters. Researchers believe that genetics sometimes plays a role in this cellular breakdown. In rare instances, Parkinson's disease may be caused by a viral infection or by exposure to environmental toxins such as pesticides, carbon monoxide, or the metal manganese. But in the great majority of Parkinson's cases, the cause is unknown.

Parkinson's disease is a form of parkinsonism. This is a more general term used to refer to the set of symptoms that is commonly associated with Parkinson's disease but sometimes stems from other causes. The distinction is important because these other causes of parkinsonism may be treatable, while others do not respond to treatment or medication. Other causes of parkinsonism include:

* An adverse reaction to prescription drugs.
* Use of illegal drugs.
* Exposure to environmental toxins.
* Stroke.
* Thyroid and parathyroid disorders.
* Repeated head trauma (for example, the trauma associated with boxing).
* Brain tumor.
* An excess of fluid around the brain (called hydrocephalus).
* Brain inflammation (encephalitis) resulting from infection.

• The Stages of Parkinson's Disease

Parkinson's disease strikes people in many different ways, leaving them to experience a broad range of symptoms. Though symptoms may be mild or severe or occur frequently or infrequently, Parkinson's disease appears to have five different stages. The time spent at each stage varies, and the skipping of stages, from stage one to stage three, for example, is not uncommon.

Parkinson's disease stages include:

Stage one: During this initial phase of the disease, a patient usually experiences mild symptoms. These symptoms may inconvenience the day-to-day tasks the patient would otherwise complete with ease. Typically these symptoms will include the presence of tremors or experiencing shaking in one of the limbs.Also during stage one, friends and family can usually detect changes in the Parkinson's patient including poor posture, loss of balance, and abnormal facial expressions.

Stage two: In the second stage of Parkinson's disease, the patients symptoms are bilateral, affecting both limbs and both sides of the body. The patient usually encounters problems walking or maintaining balance, and the inability to complete normal physical tasks becomes more apparent.

Stage three: Stage three symptoms of Parkinson's disease can be rather severe and include the inability to walk straight or to stand. There is a noticeable slowing of physical movements in stage three.

Stage four: This stage of the disease is accompanied by severe symptoms of Parkinson's. Walking may still occur, but it is often limited and rigidity and bradykinesia are often visible. During this stage, most patients are unable to complete day-to-day tasks, and usually cannot live on their own. The tremors or shakiness that take over during the earlier stages however, may lessen or become non-existent for unknown reasons during this time.

Stage five: The last or final stage of Parkinson's disease usually takes over the patients physical movements. The patient is usually unable to take care of himself or herself and may not be able to stand or walk during this stage. A patient at stage five usually requires constant one-on-one nursing care.

• Understanding Parkinson's Symptoms

Parkinson's disease is a movement disorder that progresses slowly. Some people will first notice a sense of weakness, difficulty walking, and stiff muscles. Others may notice a tremor of the head or hands. Parkinson's is a progressive disorder and the symptoms gradually worsen. The general symptoms of Parkinson's disease include:

* Slowness of voluntary movements, especially in the initiation of such movements as walking or rolling over in bed.
* Decreased facial expression, monotonous speech, and decreased eye blinking.
* A shuffling gait with poor arm swing and stooped posture.
* Unsteady balance; difficulty rising from a sitting position.
* Continuous "pill-rolling" motion of the thumb and forefinger.
* Abnormal tone or stiffness in the trunk and extremities.
* Swallowing problems in later stages.