Parkinson Disease (PD)

Medical Code: SGM-FS-008
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Condition: Parkinson Disease (PD)

Prevalence: 1 million in US, 60,000 new cases/year

Layman’s Definition: A progressive loss of control over muscle movement and balance caused by the gradual death of cells that play a key role in coordinating and smoothly controlling muscle movement.

Typical Age of Symptom Onset: Over 65 years

Primary Symptoms: At early stages, Parkinson’s Disease primarily affects muscle control and balance. The condition is characterized by problems initiating movement, involuntary shaking, or tremors in arms and/or legs at rest, as well as problems with balance.

Individuals with Parkinson’s Disease commonly exhibit jerky arm, leg, and head movements, often with shaking or twitching at rest. They also frequently stumble or fall. (Symptoms of lack of control over voluntary muscles are collectively referred to as dystonia.  See also Fact Sheet Dystonia.)

The head or body of a person with Parkinson’s disease may be markedly tilted without the person being aware of their unusual posture. The earliest symptoms of the condition often involve subtle changes in facial expression or movement patterns, which may start first on only one side of the body, and can be difficult to distinguish from a minor stroke. As there is currently no definitive test for Parkinson’s Disease, the diagnosis is made primarily on the basis of the results of a detailed neurological examination and the exclusion of other possible causes for the person’s symptoms.   

The early symptoms of Parkinson’s Disease may be similar those of essential tremor, except that individuals with essential tremor rarely show tremors at rest, while individuals with Parkinson’s Disease usually have more pronounced shaking at rest.

Secondary Symptoms: At later stages, individuals with Parkinson’s Disease may undergo personality changes and/or develop memory problems. The individual may exhibit depression, anxiety, or irritability, or experience hallucinations. Individuals with advanced Parkinson’s Disease may have difficulty concentrating or remembering things. The medications used to treat the disease’s symptoms can cause hallucinations if dopamine levels are increased too much.

Cause(s)/Risk Factor(s): The primary symptoms of Parkinson’s Disease are caused by the death of a group of dopamine-producing neurons in a part of the brain called the cerebellum that act like pacemakers. (The later symptoms of Parkinson’s Disease are due to losses of other neurons.) The pacemaker function allows the cerebellum to closely coordinate the timing of contraction and relaxation of individual muscles to produce smooth and precise movements. In the absence of such close coordination, arms and legs are constantly overshooting their mark and then overcorrecting, or simply fighting one another so the person has trouble moving at all. The main risk factors for Parkinson’s Disease are increased age and prior head trauma.

Standard Treatment(s):  L-Dopa or a similar type of drug is commonly prescribed to boost the amount of the neurotransmitter dopamine, which is produced by the surviving dopamine-producing cells in the cerebellum. This effectively allows the subtle pacemaker signal to be “heard” by more of the cells that need to hear it.

Other drugs used to treat Parkinson’s Disease increase the efficiency of dopamine signaling in slightly different ways. However, drug treatments for the disease do not prevent ongoing cell loss, and the drugs tend to become less effective over time as more and more of these critical neurons are lost.

Deep brain stimulation, (implanting an electrode into the cerebellum to reproduce the pacemaker signal), is becoming accepted as a treatment in otherwise healthy people with Parkinson’s Disease for whom medications have ceased to reduce symptoms.   

Secondary symptoms may be treated with medications on a case-by-case basis as they arise.

Occupational therapy or assistance devices may be recommended to maximize the independence of individuals with Parkinson’s Disease who have difficulty performing routine tasks.

For an excellent source of information about Parkinson disease symptoms and treatments, see:  http://www.parkinson.org

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