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 - Northwestern Memorial Hospital - Chicago

Parkinson's Disease

Parkinson's disease is a progressive degenerative disorder that affects nerve cells, or neurons, in the part of the brain that controls movement. In Parkinson's disease, a certain group of nerve cells in the brain that produce the chemical dopamine dies. The lack of dopamine causes the cardinal symptoms of Parkinson's disease—tremor, slowness of movement, muscle stiffness, and balance problems.


The exact reason the neurons deteriorate is not known. Some possibilities are:

  • Toxins: exposure to fluorocarbons, herbicides, pesticides or certain heavy metals
  • Genetic predisposition
  • Repeated head injury
  • Viral infections
  • Advanced age

The symptoms of Parkinson's disease appear when at least 80 percent of the dopamine-producing neurons are damaged.

Incidence of Parkinson's Disease

More than 1 million (and perhaps closer to 1.5 million) people in the United States have Parkinson's disease. Here are some facts about Parkinson’s disease:

  • It affects 1 in 100 Americans over the age of 60
  • The average age of onset is 60
  • 5 to 10 percent are diagnosed prior to age 40 with young-onset Parkinson's
  • It affects slightly more men than women
  • Early symptoms are subtle, and people may think their symptoms are "normal aging"
  • The symptoms of Parkinson's are similar to symptoms of other diseases; the first diagnosis may not be Parkinson's disease

Symptoms of Parkinson's Disease

Primary or Cardinal Features of Parkinson's disease

  1. Bradykinesia (slowness of movement)
  2. Rigidity or stiffness (difficulty bending arms or legs)
  3. Postural instability (stooped, slumped posture) or loss of balance
  4. Resting tremor (shaking of hand or foot when the muscles are relaxed)

The presence of at least two of the above four cardinal features is necessary for the diagnosis of Parkinson's disease.

Secondary Features of Parkinson's Disease

  • Depression 
  • Sleep disturbances
  • Anxiety and compulsive behaviors
  • Loss of facial expression
  • Urinary problems
  • Constipation  
  • Soft or monotone speech
  • Difficulties swallowing
  • Smaller, cramped handwriting
  • Sexual problems
  • Loss of sense of smell
  • Pain, numbness, tingling
  • Dementia or confusion
Last UpdateDecember 3, 2013