Parkinson’s Disease

Neurology

BY: PHYSICIANS COMMITTEE FOR RESPONSIBLE MEDICINE

Parkinson’s disease (also known as idiopathic paralysis agitans) is a chronic and progressive movement disorder that affects as many as 1 million Americans. It occurs when groups of neurons in specific areas of the brain (known as the substantia nigra and locus ceruleus) malfunction and die.

As a result, the brain does not produce enough dopamine, a chemical messenger that is important for movement and coordination. Without enough dopamine, Parkinson’s disease patients have difficulty with movements and activities of daily life, and may have mood and memory problems.

The cause is unknown, but researchers think that both genetic and environmental factors are involved. However, Parkinson’s-like symptoms can occur in individuals who are exposed to several toxins (such as pesticides; MPTP, which is a contaminant of opioid narcotics; and high levels of the mineral manganese), infections of the brain and spinal cord, head trauma, or certain medications that affect dopamine receptors (such as antinausea medications, antipsychotic medications, and reserpine).

Parkinson’s disease affects approximately 1 percent of Americans over age 50. The typical age of onset is the late 50s, although 10 percent of cases occur in people under 40.

Symptoms

The symptoms of Parkinson’s disease usually appear gradually and increase in severity over the course of years. Patients tend to have slowed movements (called bradykinesia) and appear stiff or rigid. They may have a tremor at rest, usually in the hand or thumb.

As the disease progresses, patients have more and more difficulty maintaining balance, walking, talking, and completing daily activities (such as eating, writing, dressing, and combing their hair).

Patients with Parkinson’s disease often experience some degree of depression, and may have other psychologic symptoms, including hallucinations. This may occur due to the disease itself or as a side effect of medications. Also, dementia is common in people with Parkinson’s disease, occurring in about one-third of cases.

Diagnosis

Parkinson’s disease is usually diagnosed clinically when an experienced neurologist observes the characteristic physical and neurologic symptoms. There are no tests to definitively confirm the disease but testing, such as a CT scan, MRI, or spinal tap, may be useful to rule out other diseases.

If the diagnosis is in doubt, a doctor may begin a trial of a Parkinson’s medication to see if it improves symptoms. If so, Parkinson’s disease is diagnosed.

Treatment

There is no known cure for Parkinson’s, but medical and nutritional therapies can decrease the symptoms and may slow the course of the disease.

The first step is to eliminate any drugs or medications that may be causing symptoms of Parkinson’s disease. These include antinausea medications, antipsychotic medications, reserpine, and others.

The most common medical drugs used to treat Parkinson’s disease are medications that mimic the effects of dopamine in the brain, most commonly levodopa (Sinemet). Other medications may also be useful, including bromocriptine, pergolide, entacapone, tolcapone, and selegeline.

Medications are also available to treat some of the specific symptoms of Parkinson’s disease. For example, benztropine may be effective to treat tremors. Clozapine or quetiapine may decrease hallucinations.

Physical, occupational, and speech therapies are usually very helpful for patients to improve activities of daily living, achieve or maintain independence, and interact better with their environment. Outside of therapy sessions, patients should try to maintain as active a lifestyle as possible.

There has been some coverage in the media of surgical treatments for Parkinson’s disease. While these may be helpful in treating advanced disease or in patients with specific symptoms (such as severe tremor or rigidity), they are not considered useful for most patients.

Parkinson’s Disease: Nutritional Considerations

Nutritional Considerations for Reducing Risk

Although there is no known cure for Parkinson’s disease, research studies are investigating whether dietary changes decrease the risk of disease. The following steps are under consideration:

  • Avoiding animal fat: Some studies have shown that Parkinson’s disease is more common in people who eat high levels of animal fat and saturated fat. Avoiding animal fat brings other benefits, of course, such as lower cholesterol and reduced risk of heart disease.
  • Avoiding dairy products: A large study (called the Health Professionals Follow-Up Study) found a higher risk for Parkinson’s disease in men who had high intake of dairy products. Researchers think this may be due to chemicals found in dairy products called tetrahydroisoquinolines. Further, dopamine neurons may be damaged by other chemicals in dairy products, including beta-carbolines, pesticides, and polychlorinated biphenyls.
  • Drinking caffeinated beverages: Some studies have found that people who drink several cups of coffee or tea daily have a lowered risk of developing Parkinson’s disease. This may be related to the high levels of antioxidants in both tea and coffee.

Nutritional Considerations for More Effective Treatment

Dietary changes may also improve the effectiveness of medical treatment. In some patients, the standard levodopa medication may not successfully improve symptoms. If so, there are several nutritional changes that may help.

  • Eating a low-protein diet during the daytime can be helpful because protein may decrease the availability of levodopa to the brain.
  • In addition, vitamin supplements and foods high in vitamin B6 (such as fortified cereals and grains, beans, meat, poultry, potatoes, and sweet potatoes) may also decrease the availability of levodopa to the brain. Therefore, limiting these foods and supplements may be useful.
  • Parkinson’s disease often causes weight loss. Patients should try to maintain a healthy body weight by eating regular meals and between-meal snacks that have sufficient calories from whole grains (100 percent whole oats, oat bran, bulgur, barley, brown rice), fruits, 100 percent fruit juices, and vegetables.
  • Patients may want to consult with a nutritionist for help in making healthy food choices.

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