Symptoms, Causes and Risk Factors of Parkinson's Disease
Parkinson's disease is a disorder that affects nerve cells, or neurons, in a part of the brain that controls muscle movement. In Parkinson's disease, neurons that make dopamine, a chemical that sends signals that help coordinate movements, die or become impaired. The cause of the neuron damage is unknown. Symptoms of Parkinson's disease may include:
- Trembling of hands, arms, legs, jaw and face
- Stiffness of the arms and legs
- Slowness of movement
- Poor balance and coordination
As symptoms get worse, people with the disease may have trouble walking, talking or doing simple tasks. They may also have problems such as depression, sleep problems or trouble chewing, swallowing or speaking.
Parkinson's disease usually begins around age 60, but it can start earlier. It is more common in men than in women. Parkinson's disease symptoms persist over a long period of time while also growing worse over time. It is not contagious and most cases show the disease is not hereditary.
Symptoms of Parkinson's Disease
Friends or family members may be the first to notice changes in someone with early Parkinson's disease. They may see that the person's face lacks expression and animation or that the person does not move an arm or leg normally. They also may notice that the person seems stiff, unsteady or unusually slow.
The shaking or tremor that affects the majority of Parkinson's disease patients may begin to interfere with daily activities. Patients may not be able to hold utensils steady or they may find that the shaking makes reading a newspaper difficult. Tremor is usually the symptom that makes people seek medical help.
People with Parkinson's disease often have a tendency to lean forward, take small quick steps as if hurrying forward and reduced swinging of the arms. They also may have trouble initiating movement and they may stop suddenly as they walk. Parkinson's disease does not affect everyone the same way, and the rate of progression differs among patients.
The four primary symptoms of Parkinson's disease are:
The tremor associated with Parkinson's disease has a characteristic appearance. Typically, the tremor takes the form of a rhythmic back-and-forth motion. Tremor often begins in a hand, although sometimes a foot or the jaw is affected first. It is most obvious when the hand is at rest or when a person is under stress. For example, the shaking may become more pronounced a few seconds after the hands are rested on a table.
Resistance to movement affects most people with Parkinson's disease. A major principle of body movement is that all muscles have an opposing muscle. Movement is possible not just because one muscle becomes more active, but because the opposing muscle relaxes. In Parkinson's disease, rigidity comes about when the balance of opposing muscles is disturbed. The muscles remain constantly tensed and contracted so that the person aches or feels stiff or weak. The rigidity becomes obvious when another person tries to move the patient's arm, which will move only in ratchet-like or short, jerky movements known as "cogwheel" rigidity.
Slowing down and loss of spontaneous and automatic movement makes simple tasks somewhat difficult. The person cannot rapidly perform routine movements. Activities once performed quickly and easily, such as washing or dressing, may take several hours.
Impaired balance causes patients to fall easily. Affected people also may develop a stooped posture in which the head is bowed and the shoulders are drooped.
Causes of Parkinson's Disease
Parkinson's disease occurs when nerve cells die or become impaired. Normally, these neurons produce an important brain chemical known as dopamine, which is responsible for transmitting signals between in the brain. Loss of dopamine causes abnormal nerve patterns within the brain that cause impaired movement. Studies have shown that most Parkinson's disease patients have lost 60 to 80 percent or more of the dopamine-producing cells by the time symptoms appear.
Recent studies have shown that people with Parkinson's disease also have loss of the nerve endings that produce the neurotransmitter norepinephrine. Norepinephrine is the main chemical messenger of the sympathetic nervous system which controls many automatic functions of the body, such as pulse and blood pressure. The loss of norepinephrine could help explain several of the non-motor features seen in Parkinson's, including fatigue and abnormalities of blood pressure regulation.
Getting an accurate count of the number of cases of Parkinson's disease may be impossible because many people in the early stages of the disease assume their symptoms are the result of normal aging and do not seek help from a physician. About 50,000 Americans are diagnosed with Parkinson's disease each year, according to The National Institute of Neurological Disorders and Stroke. Diagnosis can also be difficult because other conditions may produce symptoms of Parkinson's disease and there is no definitive test for the disease.
One clear risk factor for Parkinson's disease is age. The average age of onset is 60 years with increasing chance as age increases. However, about five to 10 percent of people with Parkinson's disease have "early-onset" disease that begins before the age of 50. Early-onset of the disease is often inherited and some have been linked to specific gene mutations. People with one or more close relatives who have Parkinson's disease have an increased risk of developing the disease themselves, but the total risk is still just two to five percent unless the family has a known gene mutation for the disease.