Parkinson’s disease

Definition

Parkinson's disease is a disorder of the brain characterized by shaking (tremor) and difficulty with walking, movement, and coordination. The disease is associated with damage to a part of the brain that is involved with movement.

Causes, incidence, and risk factors

Parkinson's disease was first described in England in 1817 by Dr. James Parkinson. The disease affects approximately 2 of every 1,000 people and most often develops after age 50.  It is one of the most common neurologic disorders of the elderly. Sometimes Parkinson's disease occurs in younger adults, but is rarely seen in children. It affects both men and women.

In some cases, Parkinson's disease occurs within families, especially when it affects young people. Most of the cases that occur at an older age have no known cause.

Parkinson's disease occurs when the nerve cells in the part of the brain that controls muscle movement are gradually destroyed. (The damage is progressive, which means it gets worse with time.) The exact reason that the cells of the brain deteriorate is unknown. The disorder may affect one or both sides of the body, with varying degrees of loss of function.

Nerve cells use a brain chemical called dopamine to help send signals back and forth. Damage in the area of the brain that controls muscle movement causes a decrease in dopamine production. Too little dopamine disturbs the balance between nerve-signalling substances (transmitters). Without dopamine, the nerve cells cannot properly send messages. This results in the loss of muscle function.

Some people with Parkinson's disease become severely depressed. This may be due to loss of dopamine in certain brain areas involved with pleasure and mood. Lack of dopamine can also affect motivation and the ability to make voluntary movements.

Early loss of mental capacities is uncommon. However, persons with severe Parkinson's may have overall mental deterioration (including dementia and hallucinations). Dementia can also be a side effect of some of the medications used to treat the disorder.

Parkinson's in children appears to occur when nerves are not as sensitive to dopamine, rather than damage to the area of brain that produces dopamine. Parkinson's in children is rare.

The term "parkinsonism" refers to any condition that involves a combination of the types of changes in movement seen in Parkinson's disease. Parkinsonism may be caused by other disorders (such as secondary parkinsonism) or certain medications used to treat schizophrenia.

Symptoms

• Muscle rigidity
  • Stiffness
  • Difficulty bending arms or legs
• Unstable, stooped, or slumped-over posture
• Loss of balance
• Gait (walking pattern) changes
• Shuffling walk
• Slow movements
• Difficulty initiating any voluntary movement
  • Difficulty beginning to walk
  • Difficulty getting up from a chair
• Small steps followed by the need to run to maintain balance
• Freezing of movement when the movement is stopped, inability to resume movement
• Muscle aches and pains (myalgia)
• Shaking, tremors (varying degrees, may not be present)
  • Characteristically occur at rest, may occur at any time
  • May become severe enough to interfere with activities
  • May be worse when tired, excited, or stressed
  • Finger-thumb rubbing (pill-rolling tremor) may be present
• Changes in facial expression
  • Reduced ability to show facial expressions
  • "Mask" appearance to face
  • Staring
  • May be unable to close mouth
  • Reduced rate of blinking
• Voice or speech changes
  • Slow speech
  • Low volume
  • Monotone
  • Difficulty speaking
• Loss of fine motor skills
  • Difficulty writing, may be small and illegible
  • Difficulty eating
  • Difficulty with any activity that requires small movements
  • Uncontrolled, slow movement
• Frequent falls
• Decline in intellectual function (may occur, can be severe)
• A variety of gastrointestinal symptoms, mainly constipation.

Note: Initial symptoms may be mild and nonspecific. For instance, the patient may have a mild tremor or a slight feeling that one leg or foot is stiff and dragging.

Additional symptoms that may be associated with this disease:

• Depression
• Confusion
• Dementia
• Seborrhea (oily skin)
• Loss of muscle function or feeling
• Muscle atrophy
• Memory loss
• Drooling
• Anxiety, stress, and tension

Signs and tests

The health care provider may be able to diagnose Parkinson's disease based on the symptoms and physical examination. However, the symptoms may be difficult to assess, particularly in the elderly. For example, the tremor may not appear when the person is sitting quietly with arms in the lap. The posture changes may be similar to osteoporosis or other changes associated with aging. Lack of facial expression may be a sign of depression.

An examination may show "cogwheel" rigidity (jerky, stiff movements), tremors of the Parkinson's type, and difficulty initiating or completing voluntary movements. Reflexes are essentially normal.

Tests are not usually specific for Parkinson's, but they may be required to rule out other disorders that cause similar symptoms. See also essential tremor.

Treatment

There is no known cure for Parkinson's disease. The goal of treatment is to control symptoms. 

Medications control symptoms primarily by increasing the levels of dopamine in the brain. The type of medication, the dose, the amount of time between doses, or the combination of medications used may need to be adjusted as symptoms change. Many medications can cause severe side effects, so monitoring and follow-up by the health care provider is important.

Types of medication:

• Deprenyl may provide some improvement to mildly affected patients.
• Amantadine or anticholinergic medications may be used to reduce early or mild tremors.
• Levodopa is a medication that the body converts to a brain transmitter called dopamine. It may be used to increase the body's supply of dopamine, which may improve movement and balance.
• Carbidopa is a medication that reduces the side effects of levodopa and makes it work better.
• Entacapone is a medication used to prevent the breakdown of levodopa.
• Pramipexole and ropinirole are dopamine medications used before or together with levodopa.
• Rasagiline is a medicine recently approved for patients with early Parkinson's disease. It may also be combined with levodopa in patients with more advanced cases of the disease. Rasagiline helps block the breakdown of dopamine.

Additional medications to help reduce symptoms or control side effects of primary treatment medications include antihistamines, antidepressants, dopamine agonists, monoamine oxidase inhibitors (MAOIs), and others.

Good general nutrition and health are important. Exercise should continue, with the level of activity adjusted to meet the changing energy levels that may occur. Regular rest periods and avoidance of stress are recommended, because fatigue or stress can make symptoms worse. Physical therapy, speech therapy, and occupational therapy may help promote function and independence.

Railings or banisters placed in commonly used areas of the house may be of great benefit to the person experiencing difficulties with daily living activities. Special eating utensils may also be helpful.

Social workers or other counseling services may help the patient cope with the disorder and with obtaining assistance (such as Meals-on-Wheels) as appropriate.

Experimental or less common treatments may be recommended. For example, surgery to implant stimulators or destroy tremor-causing tissues may reduce symptoms in some people. Transplantation of adrenal gland tissue to the brain has been attempted, with variable results.

Support Groups

Emotional support for the person with Parkinson's disease and everyone involved may help in coping with the changes caused by the disease. This may include the National Parkinson's Foundation or another group. See Parkinson's disease - support group.

Expectations (prognosis)

Untreated, the disorder progresses to total disability, often accompanied by general deterioration of all brain functions, and may lead to an early death.

Treated, the disorder impairs people in varying ways. Most people respond to some extent to medications. The extent of symptom relief, and how long this control of symptoms lasts, is highly variable. The side effects of medications may be severe.

Complications

• Varying degrees of disability
• Difficulty swallowing or eating
• Difficulty performing daily activities
• Injuries from falls
• Side effects of medications

Calling your health care provider

Call your health care provider if symptoms of Parkinson's disease appear, if symptoms get worse, or if new symptoms occur. Also tell the health care provider about any possible side effects of medications, which may include:

• Involuntary movements
• Nausea and vomiting
• Dizziness
• Changes in alertness, behavior or mood
• Severe confusion or disorientation
• Delusional behavior
• Hallucinations
• Loss of mental functions

References

Goetz, CG. Textbook of Clinical Neurology. 2nd ed. St. Louis, Mo: WB Saunders; 2003: 713-720.

Noble J. Textbook of Primary Care Medicine. 3rd ed. St. Louis, Mo: Mosby; 2001:1612-1618.

Illustrations

Substantia nigra and Parkinson's disease

Central nervous system

Page Content:

Paralysis agitans; Shaking palsy ; paralysis agitans; palsy shaking