Parkinson’s Disease


What Is It?

Parkinson’s disease is a disease of the central nervous system that causes problems with body motions, including tremor (shakiness), rigidity (muscle stiffness), slowed body movements, unstable posture and difficulty walking. It happens when nerve cells (neurons) in a part of the brain called the substantia nigra gradually die. These cells normally produce dopamine, a chemical that helps to relay messages between areas of the brain that control body movement. The death of cells in this area of the brain leads to abnormally low levels of dopamine, which makes it difficult for a person with Parkinson’s disease to control muscle tension and muscle movement, both at rest and during periods of activity.

Parkinson’s disease affects about 1 million people in the United States, with approximately 50,000 new cases diagnosed each year. It usually occurs in middle age, typically beginning around age 60. However, about 5 percent of patients have early-onset Parkinson’s disease and are younger than 40 years old when symptoms begin. Internationally, Parkinson’s disease affects about one to two of every 1,000 people. It affects Europeans and North Americans more frequently than Asians or Africans. It is more common in men than in women.

So far, scientists have not determined the reason why some people develop Parkinson’s disease and others do not. The genetics are complex and the influence of family history depends upon the age of onset. A person who has a parent or sibling that was diagnosed with the disease at a younger age is at higher risk of getting Parkinson’s, but not if the affected family member was older when diagnosed.


Parkinson’s disease usually begins as a slight tremor or stiffness involving the arm or leg on one side of the body. The tremor is prominent at rest and is regular, typically occurring at a rate of three to six times per second. The Parkinson’s disease tremor usually worsens under stress, improves when the arm or leg is moved voluntarily, and may disappear entirely during sleep. In the earliest stages, Parkinson’s disease may be evident only as a tremor involving the thumb and index finger. This tremor sometimes is called “pill-rolling” tremor because it looks as if the person is manipulating a small object such as a pill.

As the illness progresses, the tremor may become more widespread, and eventually affect limbs on both sides of the body. Handwriting may become small, shaky and eventually illegible. In addition to the classic tremor, Parkinson’s disease often causes stiffness or rigidity in the muscles of the arms or legs and a slowing of body movements (bradykinesia).

The rigidity and bradykinesia can be the most disabling aspects of the disease. They can impair the person’s ability to walk and to perform activities of daily living, such as washing, dressing or using eating utensils. Problems with unsteady balance and posture may make it hard for a person with Parkinson’s disease to sit down in a chair or to rise from one. Walking is accomplished with small, shuffling steps and a stooped posture, usually without the normal arm-swinging motions. Bradykinesia can affect the facial muscles, decreasing spontaneous facial expressions and normal eye blinking.

Other symptoms of Parkinson’s disease may include:

  • Depression
  • Anxiety
  • Disturbed sleep
  • Memory loss
  • Slurred or abnormally soft speech
  • Difficulty chewing or swallowing
  • Constipation
  • Impaired bladder control
  • Abnormal regulation of body temperature
  • Sexual dysfunction
  • Cramps, numbness, tingling or pain in the muscles


Your doctor will examine you, with extra attention given to the neurological examination. He or she will look for symptoms of Parkinson’s disease, especially for the classic Parkinson’s disease tremor, slowness of movement, rigidity and gait problems.

There is no specific diagnostic procedure or laboratory test to establish the diagnosis of Parkinson’s disease. For this reason, doctors diagnose Parkinson’s disease based on the symptoms and results of physical and neurological examinations. If a patient’s symptoms improve once he or she receives medication for Parkinson’s disease, the diagnosis is probably correct.

Expected Duration

Parkinson’s disease is a long-lasting (chronic), often progressive illness. In most patients, 70 percent to 80 percent of brain cells in the substantia nigra are already lost by the time symptoms first appear.


Because doctors are not sure what causes Parkinson’s disease, there is no way to prevent it.


Although there is no cure for Parkinson’s disease, its symptoms can be treated with several different types of medication. The first major decision faced by patients and their physicians is when to start treatment. When symptoms are not overly troublesome, medication may not be immediately necessary, particularly since there is some evidence that early treatment can increase the chance of developing side effects and other complications later. Treatment usually is started when symptoms interfere with work or management of household affairs and other activities, or when difficulty with walking and balance becomes significant.

The medications used to treat Parkinson’s disease either boost the levels of dopamine in the brain or mimic the effects of dopamine. The most commonly used drug therapy for Parkinson’s disease is levodopa, a medication that is converted to dopamine in the brain. Levodopa usually is prescribed in combination with carbidopa (Sinemet) to increase the amount of active drug reaching the brain while helping to limit side effects. Nearly all patients with Parkinson’s disease improve after they start taking levodopa. Unfortunately, long-term use of levodopa causes eventual side effects and complications in 75 percent of patients. Doctors commonly need to adjust the dose of levodopa and time intervals between doses to allow for continuation of the therapy.

Several alternative medications can be used either alone or in combination with levodopa to treat Parkinson’s disease symptoms. For mild symptoms in early Parkinson’s disease, amantadine (Symmetrel) or anticholinergic medications, such as trihexyphenidyl (Artane, Trihexane, Trihexy) or benztropine (Cogentin), may be helpful. Amantadine promotes the release of stored dopamine inside the brain, but it may work only briefly in some patients. Anticholinergic medications are particularly effective against tremor, but they can cause side effects such as confusion and hallucinations, especially in elderly patients. In people with mild Parkinson’s disease, selegiline (Carbex, Eldepryl) may be helpful when taken along with levodopa.

Dopamine agonist medications — such as bromocriptine (Parlodel), pergolide (Permax), pramipexole (Mirapex) and ropinirole (Requip) — may be used alone to delay the need for levodopa, or may be used with levodopa to increase its effectiveness or reduce the amount of levodopa needed. Dopamine agonists function by mimicking the effects of dopamine. Most patients who start with only a dopamine antagonist need to add levodopa within a few years. To minimize side effects, very low doses are used initially and the dose is increased gradually. Older patients can be especially sensitive to these drugs, which can cause symptoms of confusion, hallucinations and feeling weak because of low blood pressure.

Drugs called COMT (catechol-O-methyltransferase) inhibitors also can be used in combination with levodopa. COMT inhibitors, such as entacapone (Comtan) and tolcapone (Tasmar), block the enzyme that breaks down dopamine and levodopa, prolonging the action of dopamine in the brain and increasing the effectiveness of levodopa. When a COMT inhibitor is added, the doctor usually lowers the levodopa dose.

Depression is a fairly common problem among people with Parkinson’s disease, and many patients can benefit from treatment with antidepressant medications. Symptoms of depression include not only depressed mood or tearfulness, but also decreased appetite, disturbed sleep (especially early awakening), decreased interest in pleasurable pursuits or activities, decreased energy level, thoughts of worthlessness, guilt or suicide.

In addition to treatment with medications, some Parkinson’s disease patients find that regular exercise and a balanced diet help to improve their overall sense of well-being and body control.

Surgery is considered when patients stop responding adequately to medications. Surgical options include deep brain stimulation, with electrodes placed after brain mapping, and precise destruction of targeted areas in the brain responsible for the most troubling symptoms. A hotly debated procedure that holds great promise is fetal brain-tissue transplantation. Cells that can make dopamine are either transplanted from a nonviable fetus or from genetically engineered brain tissue grown in culture.

When To Call A Professional

Call your doctor if you develop any of the symptoms of Parkinson’s disease, especially if you notice a persistent tremor or stiffness anywhere in your body, or if you have trouble walking or rising from a chair. You also should call your doctor if you have any of the symptoms of depression.


Although there is no cure for Parkinson’s disease, a well-constructed treatment plan allows many patients to lead active lives.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.