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What is Parkinson’s Disease?

Published on Feb 25, 2016
Authored by Pfizer Medical Team

Parkinson's disease (PD) is a chronic and progressive neurodegenerative movement disorder, meaning the symptoms worsen over time. The most well-known symptom is tremor, but PD can also cause slowness of movements, limb stiffness, and difficulties with gait and balance. Interestingly, the major symptoms of PD may be different from person to person. About one million Americans living with PD, and approximately 50,000 are diagnosed each year with the disease.

What Causes It? And Who’s at Risk?

PD occurs when nerve cells (called neurons) in the mid-brain become damaged or begin to die. Normally, these neurons produce dopamine, a chemical that sends messages to other parts of the brain that are responsible for controlling the body’s movements. While the exact cause of PD is unknown, both genetics and environmental factors play a role in causing the disease.

Though PD can affect anyone, it is a disease most commonly occurring in older people (usually over age 60). PD can even occur in young adults as young as 18. The disease is more common in men than in women, and in those with a family history of PD (about 15% to 25% of people with PD have a relative with the disease). Studies suggest that repeated exposure to certain chemicals, such as pesticides, may increase the risk for PD; however, the risk of exposure to these environmental toxins is not fully understood.

What are the Signs and Symptoms of PD?

PD signs and symptoms vary from person to person, and generally worsen as the disease progresses over time. The primary symptoms of PD include the following:

  • Tremor. Uncontrollable “back and forth” movement that affects a limb when at rest. Tremor often begins in the hand (also called pill rolling), with a foot or jaw is affected first. It is more obvious when the hand is at rest or when the person is under stress. Tremor is usually the first reason most people seek medical attention.
  • Rigidity. Stiffness of in any part of the body, but usually occurs in the limbs. The person aches or feels stiff because muscles remain constantly tense and contracted. Limbs will move only in ratchet-like or jerky movements known as “cogwheel” rigidity.
  • Slow movement (also called bradykinesia). Slowing down of activities the person once performed quickly and easily. Can cause limited movement and difficulty washing or dressing and is usually identified by a decrease in facial expressions.
  • Poor or unsteady balance (also called postural instability). Impaired balance that can cause a person to fall easily.

Secondary symptoms can include loss of facial expression due to rigidity of facial muscles (called hypomimia), and low voice volume or muffled speech (called hypophonia). People with PD may also experience vision problems, speech, and swallowing problems, drooling, or excessive saliva due to slow swallowing. Other symptoms can include depression (common) and anxiety, sleep problems, and cognitive changes such as slowing of thought, language and memory difficulties, personality changes, and dementia. Medications that treat PD can cause hallucinations, delusions, agitation and mania.

The different stages of PD are mild, moderate and advanced. People with mild PD may have movement symptoms that are inconvenient, but do not affect daily activities. Movement symptoms typically occur on one side of the body, and are generally well controlled with medication use. Moderate PD occurs when movement symptoms affect both sides of the body. The body moves more slowly and it may become more difficult to maintain balance or move around. This is the stage in which most people with PD begin to experience side effects caused by their PD medications. People with advanced PD are usually confined to a wheelchair and are not able to live alone; however, the symptoms can be eased with medication use.

How Do You Diagnose and Treat PD?

Unfortunately, there is no standard test to diagnose Parkinson’s disease. Diagnosis is based on medical history, a physical and neurological exam, and a review of signs and symptoms.

The doctor may check whether or not you:

  • Have animated facial expressions.
  • Have tremors.
  • Have stiffness in limbs or neck.
  • Can rise from a chair easily.
  • Can walk normally.
  • Can regain balance quickly.

You may be asked to undergo specific tests (e.g., CT, MRI) so that your doctor can rule out other conditions that could be causing your symptoms. As a result, getting a PD diagnosis may take some time. Still, if you or a loved one might have PD, it’s important to a see a doctor (or neurologist, a doctor who specializes in treating the nervous system).

As far as PD treatment, there is no cure. Symptoms are managed with medications that work to increase dopamine levels in your brain. For people whose symptoms do not improve with medication, a surgical procedure called deep brain stimulation may be recommended. However, as the disease progresses, most people with PD will have symptoms that worsen even with treatment.

What You Can Do

Managing PD effectively is important whether you have PD or are caring for someone with PD. Here are a few important things to keep in mind:

  • Work closely with the doctor to find a medication that is the best approach based on the range of symptoms. Monitor symptoms and report them to the doctor. Medication regimens may need to be changed as they usually become less effective over time and patients’ motor symptoms are not as well controlled.
  • Maintain a healthy lifestyle. Though there is no special diet for PD, eating healthy foods with plenty of nutrients can help your body work more efficiently. Drinking plenty of fluids can help reduce constipation. Regular exercise can keep your muscles strong and flexible, and improve balance.
  • If you are a caregiver for a loved one with PD, it’s important to understand and prepare for the different stages of the disease.

PD Research

Research trials for PD are available in major medical institutions across the country. These include trials testing medicines to delay, prevent, and reverse the disease, as well as those exploring possible genetic and environmental links to the disease. Research to identify an accurate “biological” marker to indicate the presence of PD is also underway to improve diagnosis of the disease.

If you would like to know more, or find a study near you, information is available at: Parkinson's Disease Research, Michael J. Fox Foundation, and Pfizer: Find a Trial.

[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]


  • 1. Parkinson’s Disease Foundation. Understanding Parkinson’s. Accessed February 3, 2016.
  • 2. National Institute of Neurological Disorders and Stroke. Parkinson’s disease: Hope through research. Accessed February 3, 2016.
  • 3. National Institute of Environmental Health Sciences. Parkinson’s disease and environmental factors. Accessed February 3, 2016.
  • 4. The Michael J. Fox Foundation For Parkinson’s Research. Parkinson’s disease causes. Accessed February 3, 2016.
  • 5. The Michael J. Fox Foundation For Parkinson’s Research. Parkinson’s disease symptoms. Accessed February 3, 2016.
  • 6. National Parkinson Foundation. Motor symptoms. Accessed February 3, 2016.
  • 7. National Parkinson Foundation. Non-motor symptoms. Accessed February 3, 2016.
  • 8. Menza MA. Psychiatric symptoms associated with Parkinson disease. Psychiatric Times Web site. Accessed February 24, 2016.
  • 9. Parkinson’s Disease Foundation. Progression. Accessed February 3, 2016.
  • 10. Parkinson’s Disease Foundation. Diagnosis. Accessed February 3, 2016.
  • 11. National Institute of Neurological Disorders and Stroke. NINDS Parkinson’s disease information page. Accessed February 3, 2016.
  • 12. Parkinson’s Disease Foundation. Find the right doctor. Accessed February 3, 2016.
  • 13. The Michael J. Fox Foundation For Parkinson’s Research. Parkinson’s disease medications. Accessed February 3, 2016.
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