What Is Parkinson's Disease?

Parkinson’s disease (PD) is a disorder that affects the nervous system. It is a chronic condition that slowly worsens over time. Parkinson’s disease causes symptoms that impact a person’s ability to move (motor symptoms) such as tremor at rest, stiffness of the limbs, difficulty walking, and impaired balance.1

Other motor symptoms can also include small handwriting, stooped posture, softness of voice, and problems swallowing. PD also affects other brain functions (non-motor symptoms) causing symptoms such as reduced ability to smell, sleep disturbances such as acting out dreams, constipation, and low blood pressure when standing up.1

It is important to point out the disease is unique to each individual, and not everyone has the same symptoms.The exact cause of PD is not known, although scientists believe it results from a combination of genetic and environmental factors.1

Although rare, sometimes PD runs in families, which suggests a hereditary factor; however, most cases of PD are sporadic, occurring in people without a family history of the disease.1

Characteristics of Parkinson’s disease

PD is classified as a movement disorder and is the most common form of parkinsonism, a group of conditions that are noted by four typical symptoms:

  • Tremor at rest, such as a slight tremor in one hand or foot
  • Rigidity of limbs, neck, or shoulders
  • Postural instability (impaired balance) when standing up, which contributes to falls
  • Bradykinesia (slowness of movement)

Bradykinesia/slowness of movement is a gradual loss of spontaneous movement. Examples can include difficulty making rapid, repetitive movements, reduced arm swing while walking, difficulty initiating movements, or difficulty buttoning a shirt.1

Symptoms of PD generally are mild at the beginning of the condition and may appear as difficulty standing after sitting, some stiffness in the limbs, or moving more slowly. As the condition progresses, more classic and obvious movement symptoms may appear.1

In addition to the motor symptoms, people with PD may also experience symptoms of difficulty swallowing or chewing, changes to their speech, urinary problems, constipation, skin problems, sleep problems, pain, depression, anxiety, and cognitive problems, such as problems planning and executing tasks, difficulty focusing, difficulty remembering the name of words, or problems with navigating around familiar areas such as the house or neighborhood.1

How does Parkinson’s disease affect the body?

In PD, the nerve cells (neurons) in the brain die or become damaged. While there are multiple areas of the brain that are affected, the primary motor symptoms in PD are mainly caused by loss of neurons in the substantia nigra, an area near the base of the brain.1,2

Neurons in the substantia nigra produce dopamine, a chemical messenger that transmits signals that produce smooth, purposeful movement. The loss of dopamine due to the damage and death of the neurons causes impaired movement. Research has shown that people with PD have lost 60-80 percent or more of the neurons that produce dopamine by the time symptoms appear.1,2

Lewy bodies are another primary characteristic of Parkinson’s disease. Lewy bodies, are collections or “blobs” of the protein alpha-synuclein. These Lewy bodies are found throughout the brain and contribute to the loss of neurons or dysfunction of the neurons.1,2

How is Parkinson’s disease treated?

While there is no known cure for PD, medications such as levadopa, which increases levels of dopamine, in the brain help control the symptoms. Another treatment is deep brain stimulation, which requires surgery to implant a probe in the brain that helps control the activity of the neurons in brain areas that control movement.

These treatments can often manage or improve the motor symptoms. However, much more scientific research is needed to find treatments that stop the progression of the disease and treatments that help alleviate the non-motor symptoms.

It is also important to note that all the above-mentioned symptoms can be found in other diseases. Therefore, it is critical to visit a doctor, especially a movement disorders specialist, to diagnose and treat PD.

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Written by: Emily Downward | Last reviewed: March 2017