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Parkinson’s disease (PD) is a progressive neurological disorder. It first presents with problems of movement.
Smooth and coordinated muscle movements of the body are made possible by a substance in the brain called dopamine. Dopamine is produced in a part of the brain called the "substantia nigra." In PD, the cells of the substantia nigra start to die. When this happens, dopamine levels are reduced. When they have dropped 60 to 80 percent, symptoms of PD start to appear.
There’s no cure for PD. This disorder is chronic and worsens over time. More than 50,000 new cases are reported in the U.S. each year. The actual incidence may be even higher, since PD is often misdiagnosed. The Center of Disease Control and Prevention’s National Center for Health Statistics reports that PD complications are the 14th major cause of death in the United States. (CDC)
The exact cause of PD is unknown. It may have both genetic and environmental components. Some scientists think that viruses can trigger PD as well.
Low levels of dopamine and norepinephrine, a substance that regulates dopamine, have been linked with PD. Abnormal proteins called Lewy bodies have also been found in the brains of people with PD. Scientists do not know what role, if any, Lewy bodies play a role in the development of PD.
Certain groups of people have an increased risk of PD.
Men are one and a half times more likely to get PD than women.
Whites are more likely to get PD than African-Americans or Asians.
PD usually appears between the ages of 50 and 60. It only occurs before the age of 40 in five to 10 percent of cases. People with a family history are more likely to develop this disorder.
Some of the earliest symptoms of PD are decreased ability to smell (anosmia) and constipation. These symptoms can precede motor problems by several years.
The four major motor problems seen in PD are:
Secondary symptoms of PD include:
Other, more extreme, symptoms of PD are:
There is no specific test for PD. Diagnosis is made based on health history and a physical and neurological exam. Tests such as CAT scan or MRI may be used to rule out other conditions.
Adequate rest, exercise, and a balanced diet are important. Speech therapy, occupational therapy, and physical therapy can also help to improve communication and self care.
Surgical interventions are reserved for people who don’t respond to medication, therapy, and lifestyle changes. So are procedures such as deep brain stimulation (DBS).
In almost all cases of PD, medication will be required to help control the various physical and mental health symptoms associated with the disease.
A number of different drugs can be used to treat PD.
Levodopa is the most common treatment for PD. It helps to replenish dopamine. About 75 percent of cases respond to levodopa, but not all symptoms are improved. Levodopa is generally given with carbidopa. Carbidopa delays the breakdown of levodopa which in turn increases the availability of levodopa at the blood-brain barrier.
Dopamine agonistscan imitate the action of dopamine in the brain. Dopamine agonists are less effective than levodopa. However, they can be useful as bridge medications when levodopa is less effective. Drugs in this class include bromocriptine, pramipexole, and ropinirole.
Anticholinergics are used to block the parasympathetic nervous system. They can help with rigidity. Side effects may include impaired memory, dry eyes, dry mouth, and constipation. Benztropine (Cogentin) and trihexyphenidyl are anticholinergics used to treat PD.
Amantadine (Symmetrel) can be used along with carbidopa-levodopa. It is a glutamate blocking drug (NMDA). It offers short-term relief for the involuntary movements (dyskinesia) that can be a side effect of levodopa. Side effects of amantadine include hallucinations and patchy skin color.
Catechol O-methyltransferase (COMT) inhibitorsprolong the effect of levodopa. Entacapone (Comtan) and tolcapone (Tasmar) are examples of COMT inhibitors. Tolcapone can cause liver damage. It is usually saved for patients who don’t respond to other therapies. Ectacapone doesn’t cause liver damage. Stalevo is a drug that combines ectacapone and carbidopa-levodopa in one pill.
MAO B inhibitorsinhibit the enzyme monoamine oxidase B. This enzyme breaks down dopamine in the brain. Side effects don’t occur often, but they can include headache, dizziness, confusion, and hallucinations. Selegiline (Eldepryl) and rasagiline (Azilect) are examples of MAO B inhibitors. Talk with your doctor before taking any other medications with MAO B inhibitors. They can interact with many drugs, including:
Over time, the effectiveness of PD medications can decrease. However, they may still provide adequate control of symptoms.
People with PD have problems with activities of daily living. Doctors at the Mayo Clinic have recommended a number of very simple steps to help patients with PD move around and walk more safely.
To improve walking:
To avoid falling:
When getting dressed:
Written by: Verneda Lights and Elizabeth Boskey, PhD
Medically reviewed on: Jul 25, 2012: Brenda B. Spriggs, MD, MPH, FACP
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