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Parkinson's disease

Paralysis Agitans, Parkinsonism, Shaking Palsy, Idiopathic Parkinson's

What is Parkinson's disease?

Parkinson's disease is chronic, progressive disease, which means it is a long-term condition in which the symptoms worsen over time. It causes several characteristic symptoms, including tremors, slowness of movement (bradykinesia) and limb and trunk rigidity. It is a motor system disorder. As symptoms progress, patients with Parkinson's disease may have difficulty performing basic tasks, including talking and walking.

The condition was identified in 1817 by James Parkinson, a British physician who first described the principal symptoms of the disease.

Parkinson's disease is the second most common neurodegenerative disease after Alzheimer's disease, according to the National Parkinson Foundation (NPF). Some estimates suggest that roughly 1 million people in the United States have Parkinson's disease. However, the disease is often not diagnosed or misdiagnosed, so this figure may not be accurate. The NPF estimates that Parkinson's disease affects one in every 100 people over the age of 60, and the average age of onset is 60. The National Institute of Neurological Disorders and Stroke (NINDS) estimates that “early-onset” (in which symptoms develop before the age of 50) Parkinson's disease occurs in about 5 to 10 percent of people with Parkinson's disease. These cases are often inherited, and scientists have linked several cases to identified gene mutations. In rare cases, symptoms may appear in people under 20, a condition known as juvenile parkinsonism.

For unknown reasons, more men than women are affected. The NINDS estimates that 50 percent more men than women have Parkinson's disease.

In healthy people, cells within a small region of the brain stem known as the substantia nigra produce and release a neurotransmitter called dopamine, which controls movement and balance in the body. Dopamine is vital to proper central nervous system functioning and helps electrochemical signals move from one neuron to another.

However, patients with Parkinson's disease experience a destruction of the cells in the substantia nigra. By the time 60 to 80 percent of these cells are destroyed, there is a sharp decline in dopamine production triggering the symptoms of Parkinson's disease.

Recent studies also have found that destruction of the nerve endings that produce the neurotransmitter norepinephrine may contribute to many of the nonmotor-related symptoms of Parkinson's disease. These include fatigue and blood pressure problems. Norepinephrine is the chief chemical messenger within the sympathetic nervous system (the part of the autonomic nervous system that controls automatic functions in the body).

Some patients who appear to have Parkinson's disease may actually have a separate disorder that mimics Parkinson's disease. These disorders may be grouped with Parkinson's disease and are collectively known as parkinsonism. Examples of non-Parkinson's disease parkinsonism include:

  • Drug-induced parkinsonism. Caused by taking certain medications, including antipsychotics, calcium-channel blockers, the dopamine blocker metoclopramide and the blood pressure medication reserpine.
  • Vascular parkinsonism. Results from blockage of small blood vessels to the brain.
  • Essential tremor. A progressive condition that tends to run in families and usually affects both hands, particularly when the hands are moving. It may affect the head as well. Patients with this condition usually do not have other parkinsonian features.
  • Lewy body dementia. Condition marked by early dementia, hallucinations and fluctuations in cognitive status.
  • Multiple system atrophy. An illness that causes symptoms similar to Parkinson's disease, but it is much less common and tends to develop more rapidly. The cause of this neurodegenerative disease is unknown.
  • Other conditions. Parkinsonian symptoms may appear in patients with other neurological disorders, including Wilson's disease, Huntington's disease, Alzheimer's disease, spinocerebellar ataxias and Creutzfeldt-Jakob disease.
Without treatment, patients with Parkinson's disease usually experience a steady worsening of symptoms and a corresponding decline in quality of life. However, both the nature and severity of symptoms vary significantly from patient to patient, and overall prognosis usually is difficult to predict. Generally, most people with Parkinson's disease have a similar life expectancy to healthy people. However, some of the symptoms of Parkinson's disease (e.g., difficulties chewing and swallowing) may cause choking and aspiration pneumonia, which can be fatal.

How is it diagnosed?

In diagnosing Parkinson's disease, a physician will compile a thorough medical history and perform a complete physical examination. To date, no blood tests or other laboratory tests have been shown to accurately diagnose Parkinson's disease.

While diagnosis may be difficult, a neurological examination may provide clues to the presence of the illness. The physician will also look for at least two of the following three signs: tremor when the patient is at rest, slowness of movement (bradykinesia) or rigidity. Various tests can be used to reveal the presence of these symptoms. For example, patients may be asked to tap a finger and thumb together or tap their foot to look for signs of bradykinesia. Meanwhile, postural instability is tested by asking patients to retain their balance while they are pulled backwards by the physician.

Physicians may recommend a brain scan, using imaging technology such as magnetic resonance imaging (MRI), to rule out other conditions that can cause similar symptoms.

Parkinson's disease is diagnosed when a combination of a patient's medical history, symptoms and test results indicate illness that cannot be explained by other factors or diseases.

How is Parkinson's disease treated?

There is no cure for Parkinson's disease. Medications are usually recommended and can substantially reduce a patient's symptoms. Most medications are aimed at increasing the levels or reducing the breakdown of dopamine in the brain. However, it is not possible to take dopamine in pill form because the chemical is broken down before it can reach the brain.

Most patients receive a combination of the drugs levodopa and carbidopa to treat the symptoms of Parkinson's disease. Neurons inside the body convert levodopa to dopamine, and carbidopa helps to ensure that this process does not happen until the levodopa reaches the brain. Carbidopa also helps reduce side effects that are associated with levodopa, such as nausea and vomiting. Other side effects of levodopa include dyskinesia (uncontrollable movements), sudden sleep onset, hallucinations and psychosis.

Most patients who take this medication gain some benefit from it, according to the National Institute of Neurological Disorders and Stroke (NINDS). Usually, these drugs have the most significant impact on rigidity and slowness of movement. They are also effective in reducing tremors. However, they may have little or no effect on other symptoms, such as postural instability or nonmotor-related symptoms. They also do not repair or replace damaged nerve cells in the brain, nor do they stop progression of the disease.

The benefits of levodopa therapy are usually experienced soon after beginning the medication, although the dosage may be gradually increased over time in order to be most effective. Levodopa can dramatically increase the quality of life for people with Parkinson's disease. However, it is not a cure for Parkinson's disease and cannot slow the progression of the disease. Eventually, the effectiveness of levodopa therapy may decrease, in which case patients usually experience a gradual worsening of symptoms (called the “wearing off effect”) or periodic attacks of more severe symptoms (called the “on-off effect”).

Other drugs may be used to treat the symptoms of Parkinson's disease or increase the effectiveness of levodopa. These may include:

Dopamine agonists

These drugs treat Parkinson's disease by mimicking the effects of dopamine on target cells. They are sometimes used in conjunction with levodopa. Although they are generally considered safe, the side effects from this type of medication can include sleep disorders, hallucinations, confusion and nightmares. They have also been linked to compulsive behavior (e.g., gambling, hypersexuality, excessive shopping) in some patients.

COMT inhibitors and MAO-B inhibitors

These drugs inhibit the breakdown of dopamine caused by the enzymes catechol-O-methyltransferase (COMT) and monoamine oxidase B (MAO-B). They are often used to extend the effectiveness of levodopa. The most common side effect from these medications is diarrhea. People who are taking certain other drugs (e.g., the antidepressant fluoxetine or the pain medication mepiridine) should consult their physician before taking certain MAO-B inhibitors as they may have harmful interactions.

Anticholinergics

These drugs are primarily used to treat tremors and muscle rigidity. They work by reducing the effects of the neurotransmitter acetylcholine. It is thought that excess levels of acetylcholine increase neuron activity in the brain and that, by reducing these levels, anticholinergics may be effective in controlling tremors and muscle rigidity. However, anticholinergics are only effective in roughly half of the patients who use them, according to the NINDS. Even for people who respond well to anticholinergics, the medication usually offers limited benefits for a short period of time. Side effects may include dry mouth, constipation, urinary retention, hallucinations and delirium.

Amantadine

This drug may be used to treat the symptoms of Parkinson's disease, as well as some of the side effects of levodopa, such as dyskinesia. Amantadine is an antiviral drug that is sometimes used to treat certain types of influenza. It is not fully understood how the drug works to control symptoms of Parkinson's disease, although it is thought to increase the effects of dopamine. Side effects may include insomnia, mottled skin and hallucinations.
If medications fail to alleviate symptoms, patients with advanced Parkinson's disease may be advised to undergo surgery. One of the most common procedures is a form of surgery called deep brain stimulation. In this procedure, electrodes are placed in the brain and connected to a small electrical device (called a pulse generator) that is surgically implanted in the chest wall. The pulse generator delivers electrical stimulation to specific parts of the brain in order to reduce the patient's symptoms. The device can be controlled by the patient and reprogrammed by a physician as needed.

It is important to note that not all patients are good candidates for surgery. Deep brain stimulation has been shown to be more effective on younger patients with Parkinson's disease and is generally not suitable for patients who are in poor overall health. However, some older patients in good health have benefited from deep brain stimulation.

Another form of surgery, known as a pallidotomy or thalamotomy (depending on the area of the brain targeted), involves the destruction of parts of the brain that are associated with the symptoms of Parkinson's disease. During this procedure, surgeons use radio frequency energy to heat and destroy the globus pallidus (pallidotomy) or the thalamus (thalamotomy). Abnormal activity in these two small areas in the brain is believed to contribute to movement problems in people with Parkinson's disease.

Because of the risks with radiofrequency destruction of the globus pallidus or thalamus, deep brain stimulation is usually a preferred treatment method over pallidotomy and thalamotomy for patients with advanced Parkinson's disease.

Surgery may improve many of the symptoms of Parkinson's disease. However, patients may find that they still have to rely on medication to effectively control symptoms. They may also still have to take medication to treat symptoms that are not affected by surgery, such as nonmotor-related symptoms.

Physical therapy and occupational therapy can help patients learn new ways to cope with their symptoms. Physical therapy includes a mixture of exercise, massage and other treatments to maintain strength and flexibility. A physical therapist is likely to teach the patient exercises that can be performed at home to strengthen and retrain muscles. This helps patients improve balance and reduce fatigue. Occupational therapy is similar to physical therapy, but it focuses on improving patients' fine motor skills so they can better accomplish daily activities, such as dressing and bathing.

Patients are encouraged to engage in complementary or supportive therapies, such as eating a well-balanced diet and exercising regularly. Eating a diet that is high in fiber and consuming plenty of fluids can help reduce constipation, which can be associated with Parkinson's disease. Additionally, patients who remain active may better cope with the disabling nature of the disease.

Finally, some patients and their caregivers may find that support groups or individual counseling are helpful when coping with Parkinson's disease. This type of therapy may be a valuable outlet for both the patient and the patient's caregiver to discuss feelings of frustration or depression.

Medications

Anticholinergics; antihistamines; antidyskinetics; antitremor drugs, such as amantadine; or antiparkinson medications (dopamine stimulators, dopamine precursors), including bromocriptine, levodopa and carbidopa. Selegiline is prescribed to maintain maximal effectiveness of levodopa and carbidopa. All these decrease tremors and reduce muscle rigidity, but they often have significant side effects.

Symmetrel (Amantadine), Seroquel (Quetiapine), Ambien (Zolpidem)

Activity

Remain as active as possible, and rest often. Physical abilities vary greatly between persons with this disease. The only restrictions are those imposed by muscle rigidity.

What might complicate it?

Complications of the disease include difficulty moving and speaking, confusion, depression, aspiration pneumonia, weight loss, and falls and injury.

Predicted outcome

The symptoms of Parkinson's disease can be relieved or controlled. There is, however, no cure, and all individuals will continue to deteriorate. Life expectancy is not significantly reduced unless onset is under 50 years of age.

Alternatives

Differential diagnoses may include Wilson's disease, striatonigral degeneration, essential tremor, Creutzfeldt-Jakob disease, Huntington's disease, Shy-Drager syndrome, progressive supranuclear palsy, cortical basal ganglionic degeneration, stroke, and hydrocephalus.

Type of rehabilitation

Physical therapy, including range of motion exercises (ROM), occupational therapy, and speech therapy may be useful in special cases, one to five times a week, for limited periods.

Appropriate specialists

Neurologist, physical therapist, occupational therapist and speech therapist.

Last updated 3 July 2021