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Parkinson's Disease

Medically reviewed by Last updated on Mar 21, 2024.

What is Parkinson's Disease?

Harvard Health Publishing

Parkinson's disease (PD) is a disease of the central nervous system. It causes problems with body motions, including:

PD develops when certain nerve cells (neurons) in the brain die. These are neurons that produce a chemical called dopamine. Dopamine helps relay messages between areas of the brain that control body movement.

When these neurons die, abnormally low levels of dopamine are produced. This makes it difficult to control muscle tension and muscle movement.

Having a parent or sibling diagnosed with the disease at a younger age increases your risk of getting PD. The same is not true if the affected family member was older when diagnosed.PD usually occurs in middle age. It typically begins around age 60. A small number of patients have early onset PD. They are younger than 40 years old when symptoms begin.


PD usually begins as a slight tremor or stiffness. It occurs in the arm or leg on one side of the body. The tremor is most obvious at rest. It is regular, typically occurring three to six times per second.

The PD tremor:

At first, PD may be evident only as a tremor involving the thumb and index finger. It looks as if the person is manipulating a small object.

As the illness worsens, tremors may become more widespread. They eventually affect limbs on both sides of the body. Handwriting may become small, shaky and eventually illegible.

PD often causes stiffness or rigidity in the arms or legs. In addition, there is a slowing of body movements, called bradykinesia.

Rigidity and bradykinesia can be the most disabling aspects of the disease. They can impair the person's ability to walk. They can make it difficult to perform daily activities. These may include washing, dressing or using utensils.

Problems with unsteady balance and posture may make it hard to sit down in a chair, or to rise from one. Walking is accomplished with small, shuffling steps and a stooped posture.

Bradykinesia can affect the facial muscles. It can decrease spontaneous facial expressions and normal eye blinking.

Other symptoms of PD may include:


Your doctor will examine you. He or she will pay extra attention to the neurological examination.

Your doctor will look for symptoms of PD, especially:

There is no specific diagnostic procedure or laboratory test to establish a Parkinson's diagnosis. Doctors diagnose the disease based on the symptoms and physical and neurological exams.

If a patient's symptoms improve after taking PD medication, the diagnosis is probably correct.

Expected Duration

PD is a chronic, often progressive illness.


Doctors are not sure what causes PD. There is no known way to prevent it.


There is no cure for PD. But its symptoms can be treated with several different types of medication.

When symptoms are not overly troublesome, medication may not be necessary. Early treatment may even increase the chance of developing side effects and other complications later.

Treatment usually is started when:

Medications used to treat PD either:


The most commonly used medication for PD is levodopa. Levodopa is converted to dopamine in the brain.

Levodopa usually is prescribed in combination with another drug called carbidopa. The second drug increases the amount of active drug that reaches the brain. It also limits side effects. The two drugs, levodopa and carbidopa, are combined in one pill (Sinemet).

Nearly all patients with PD improve after they start taking levodopa. However, long-term use eventually causes side effects and complications. Doctors often need to adjust the frequency and dose of levodopa so the person can continue taking it.

Several medications can be used either alone or in combination with levodopa to treat symptoms.

For mild symptoms in early PD, amantadine (Symmetrel) helps release stored dopamine in the brain.

Anticholinergic medications also help relieve mild symptoms in early PD. There are several choices, including trihexyphenidyl (Artane, Trihexane, Trihexy), benztropine (Cogentin), biperiden(Akineton), or procyclidine(Kemadrin). Anticholinergic drugs are particularly effective against tremor. But they can cause side effects. These include confusion and hallucinations, especially in elderly patients.

Another treatment option for early PD is a monoamine oxidase-B (MAO-B) inhibitor, such as selegiline (Carbex, Eldepryl) or rasagiline (Azilect). MAO-B inhibitors boost the effectiveness of the dopamine that the brain is still making. They may delay the need for stronger drugs. Eventually, though, people taking an MAO-B inhibitor will need a levodopa-containing drug.

Dopamine agonists mimic the effects of dopamine. Some of the commonly used dopamine agonists are pramipexole (Mirapex), ropinirole (Requip) and transdermal rotigotine (Neupro)—may be used to delay the need for levodopa. Older patients can be especially sensitive to these drugs. They can cause confusion, hallucinations and weakness due to low blood pressure. Also some people develop impulse control disorder, such as a new gambling problem.

Drugs called COMT inhibitors also can be used in combination with levodopa. COMT inhibitors, such as entacapone (Comtan) and tolcapone (Tasmar), prolong the action of dopamine in the brain. They also increase 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 PD. Many patients can benefit from treatment with antidepressant medications.

Regular exercise and a balanced diet also may help to improve a patient's overall sense of well-being and body control.

Surgery is considered when patients stop responding well enough to medications. Surgical options include:

Treatment options

The following list of medications are related to or used in the treatment of this condition.

View more treatment options

When To Call A Professional

Call your doctor if you develop any of the symptoms of PD.

Also call if you:


There is no cure for PD. But a well-constructed treatment plan allows many patients to lead active lives.

Additional Info

National Parkinson Foundation

American Academy of Neurology


Learn more about Parkinson's Disease

Treatment options guides (external)

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.