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Parkinson’s Disease (PD)

Last updated March 14, 2018

Approved by: Maulik P. Purohit MD, MPH

Parkinson’s Disease (PD) is a progressive neurodegenerative disorder that results from depletion of the neurotransmitter dopamine in the brain.

What are the other Names for this Condition? (Also known as/Synonyms)

  • Atherosclerotic Parkinsonism
  • Parkinson Disease
  • PD (Parkinson’s Disease) 

What is Parkinson’s Disease? (Definition/Background Information)

  • Parkinson’s Disease (PD) is a progressive neurodegenerative disorder that results from depletion of the neurotransmitter dopamine in the brain. It mostly affects elderly adults over the age of 55
  • Patients with PD experience mainly motor symptoms including impaired movement and posture. Cognitive, psychiatric, sensory, and autonomic symptoms may also be present
  • Some forms of PD are familial (due to genetic factors), while most are idiopathic (where the factors are not known). Parkinsonism may also develop due to secondary causes, such as injury to the brain or an infection
  • A diagnosis of Parkinson’s Disease may be made by recognizing the classical signs and symptoms and through a neurological evaluation
  • Currently, there is no cure for the condition, but the symptoms of PD may be treated using medications and physiotherapy. This can also slow the progression of the condition
  • The prognosis of Parkinson’s Disease depends on many factors. Some forms of PD are better controlled than others. For a majority of people, Parkinsonism may progress slowly and appear over time, but for some unknown reason, symptoms may rapidly progress in others

Who gets Parkinson’s Disease? (Age and Sex Distribution)

  • Parkinson’s Disease is common and typically occurs in middle-age and older adults. The average age of symptom onset is 55-65 years, although 5% of the cases are observed to occur in adults younger than 40 years
  • As many as 15% of the individuals between ages 65 and 74, and 50% of the individuals over age 85 have symptoms of Parkinson’s Disease
  • Men have a slightly higher incidence of the condition than women
  • PD is seen worldwide in all racial and ethnic groups 

What are the Risk Factors for Parkinson’s Disease? (Predisposing Factors)

The risk factors of Parkinson’s Disease include the following:

  • The main risk factor for PD is advanced age
  • There is also some genetic susceptibility, as first degree relatives of patients diagnosed with PD are twice as likely to develop the condition
  • Environmental risk factors include exposure to certain toxins and medications, living in rural areas, drinking well water, working with pesticides, and working in wood/paper mills. These risk factors are not yet well categorized and are still being studied.  
  • Repeated head trauma and a prior brain infection 

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Parkinson’s Disease? (Etiology)

  • The cause of the symptoms of Parkinson’s Disease is a result of the death of neurons (brain cells) in localized brain structures, called the substantia nigra and locus coeruleus. These neurons normally produce dopamine, a neurotransmitter that acts as a chemical signal to brain regions responsible for motor activity
  • As a consequence, fewer dopaminergic neurons result in decreased excitation of the brain regions that initiate and coordinate movement. The underlying cause of dopaminergic neuron loss is unknown in most cases. PD due to unknown causes is termed as Idiopathic Parkinsonism or Primary Parkinsonism, which is the most common form of PD
  • 5% of the cases are due to inherited familial forms of PD (due to genetic mutations) that tend to have an earlier onset of symptoms (before age 45) and a longer course of illness. PD due to genetic factors is known as Hereditary Parkinsonism
  • Secondary Parkinson’s Disease can however result from vascular diseases, AIDS, and other infections
  • In some patients, toxins (such as copper, iron, lead, manganese, cyanide, methanol, and carbon monoxide) and certain medications (such as antipsychotics, antiseizure, and anti-nausea) may be the cause of Parkinson-like symptoms

What are the Signs and Symptoms of Parkinson’s Disease?

  • Patients may experience weakness, fatigue, aches, and shoulder pain early in the course of the disease.  The classic signs and symptoms of Parkinson’s Disease include:
    • Tremors
    • Muscular rigidity     
    • Slow movement (bradykinesia)
    • Shuffling gait
    • Stooped posture
  • Tremors are usually worse at rest and begin in the hands or feet on one side of the body. A continuous ‘pill-rolling’ motion of the hand and wrist is very common. Later in the disease course, tremors of the lips, tongue, and chin may develop.
  • Many patients have a flexed posture when standing due to increased muscular rigidity
  • Initiation of voluntary movements and fine motor movements, such as handwriting, are often impaired
  • Walking without swinging the arms and shuffling the feet are common features
  • Facial expressions may be decreased and voice changes may occur
  • Patients may also develop anxiety, depression, sleep problems, blurry vision, and decreased sense of smell (anosmia)

How is Parkinson’s Disease Diagnosed?

The diagnosis of Parkinson’s Disease may involve the following:

  • Physical examination and medical history evaluation: The condition is diagnosed by the presence of clinical symptoms in adults experiencing tremor, slow or stiff movements, and balance or gait problems
  • Thorough neurological examination by a qualified healthcare professional
  • There are no specific laboratory tests or imaging studies to aid a diagnosis. Diagnosis early in the disease course, when symptoms are mild, can be difficult
  • The individual’s family members may be the first to notice the appearance of symptoms, which may be subtle

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Parkinson’s Disease?

The complications of Parkinson’s Disease may include:

  • Depression and anxiety occur in 50% of the individuals; it can be treated though
  • Dementia is common with advanced PD
  • Symptoms of autonomic dysfunction, such as urinary incontinence and constipation, excessive sweating, orthostatic hypotension (feeling lightheaded upon standing), and sexual dysfunction may develop
  • Postural instability and balance problems may lead to falls and related injuries/fractures.  Injuries from falls are a major cause of hospitalization and death.

How is Parkinson’s Disease Treated?

  • There is no cure for Parkinson’s Disease. Currently, there are no medications available that can slow the disease progression or completely restore normal movement. The symptoms of PD are treated so that the affected individuals can continue to work and maintain a good quality of life.
  • There are many different types of medications for Parkinson’s Disease.
  • Overall, tremors, rigidity, and bradykinesia respond better to treatment than cognitive and autonomic symptoms
  • Drugs that are precursors to dopamine or that mimic dopamine often provide good symptom relief
  • Other types of medications can help by increasing the production and release of dopamine, or by preventing its breakdown
  • Almost all available medications (may) have side effects, so adjustments are often required to find optimal doses
  • Following prolonged treatment, patient responses to medications may decrease over time

Most specialists believe that medications should be started when symptoms begin to interfere with normal functioning. Regular physical exercise is also very important to maintain strength, range of motion and balance, and to prevent further disability related to a sedentary lifestyle.

Occasionally, surgery is done to relieve symptoms that do not respond to medication. Tremors that are resistant to medication have been treated with high-frequency stimulation of particular brain areas with implanted electrodes. Current research is focused on gene therapy and stem cell transplantation to replace the dying dopaminergic neurons, as well as neuro-protective strategies to prevent neuron loss.

How can Parkinson’s Disease be Prevented?

Currently, there are no specific methods or guidelines to prevent most cases of Parkinson’s Disease. However, recognition of the following factors may be helpful with respect to PD:

  • Avoidance of repeated head trauma, certain toxins, and occupations and medications known to be associated with PD may be beneficial
  • Early diagnosis with close monitoring and treatment of PD is important. Prompt treatment and early recognition of the condition will help in having optimal outcomes
  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help to better the understanding of the risks during pregnancy
  • If there is a family history of the condition, then genetic counseling will help assess risks before planning for a child 

What is the Prognosis of Parkinson’s Disease? (Outcomes/Resolutions)

  • Parkinson’s Disease is a degenerative disorder affecting the brain and nervous system that cannot be cured, but only managed through proper treatment (that includes medication, exercises, and surgery in some cases). This can help decline the progression of the condition
  • The symptoms of PD progress and worsen over many months to years. A slow increase in impairment may occur over 10 to 25 years
  • In some PD patients, the disease slowly progresses, while for others, the symptom progression is rapid.  Research is still being done to understand why this occurs

Additional and Relevant Useful Information for Parkinson’s Disease:

  • After Alzheimer’s disease, Parkinson’s Disease is recognized as the second most common neurodegenerative condition affecting millions of individuals around the world
  • Consumption of coffee/caffeine, smoking, use of NSAIDs (non-steroidal anti-inflammatory drugs), and postmenopausal estrogen replacement therapy are all factors that are associated with decreased risk of the condition

What are some Useful Resources for Additional Information?

References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: April 11, 2015
Last updated: March 14, 2018