Alternative Names: Paralysis agitans, Shaking palsy.
Parkinson's disease (PD) is a progressive, neurological disease that mainly affects movement. Parkinson's disease results from the destruction of nerve cells in a part of the brain called the basal ganglia.
Different parts of the brain work together by sending signals to each other to coordinate all of our thoughts, movements, emotions, and senses. When we want to move, a signal is sent from the basal ganglia to the thalamus and then to the cerebral cortex, all different parts of the brain. Nerve cells in the brain communicate by using chemicals. A chemical (neurotransmitter) called dopamine is produced in a group of cells called the substantia nigra and is essential for normal movement. When the cells die they can no longer produce and send dopamine so the signal to move doesn't get communicated. Another chemical in the brain, acetylcholine, is controlled by dopamine. When there is not enough dopamine, there is too much acetylcholine, causing the tremors and muscle stiffness that many people with PD experience.
People with Parkinson's often exhibit a "shuffling" gait, tremor of the arms and legs when they are resting, muscle stiffness, and stooped posture. Some individuals also have cognitive (thinking, judgment, memory) problems.
Estimates regarding the number of people in the United States with Parkinson's range from 500,000 to 1,500,000 with 50,000 new cases reported annually. Since Parkinson's is more common in people 60 years old and older, it is expected that the incidence of Parkinson's will increase with the aging of the baby boomers. Although PD is more common in older persons, some people do begin to show symptoms before they are 40 years old.
Usually, Parkinson's disease begins subtly and progresses gradually. In about two thirds of people, tremors are the first symptom. In others, the first symptom is usually problems with movement or a reduced sense of smell.
Parkinson's disease typically causes the following symptoms:
Tremors: Tremors are coarse and rhythmic. They usually occur in one hand while the hand is at rest (a resting tremor). The tremor is called a pill-rolling tremor because the hand moves as if it is rolling small objects around. The tremor decreases when the hand is moving purposefully and disappears completely during sleep. Emotional stress or fatigue may worsen the tremor. The tremor may eventually progress to the other hand, the arms, and the legs. A tremor may also affect the jaws, tongue, forehead, and eyelids, but not the voice. In some people, a tremor never develops.
Stiffness (rigidity): Muscles become stiff, impairing movement. When the forearm is bent back or straightened out by another person, the movement may feel stiff and ratchet-like (called cogwheel rigidity).
Slowed movements: Movements become slow and difficult to initiate, and people tend to move less. Thus, mobility decreases.
Difficulty maintaining balance and posture: Posture becomes stooped, and balance is difficult to maintain, leading to a tendency to fall forward or backward. Because movements are slow, people often cannot move their hands quickly enough to break a fall.
Causes and Risk factors:
Parkinson's disease occurs when the nerve cells in the part of the brain that controls muscle movement are gradually destroyed. The damage gets worse with time. The exact reason that the cells of the brain waste away 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-signaling 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
The diagnosis is likely if the person has fewer, slow movements and either the characteristic tremor or muscle rigidity. Mild, early disease may be difficult for doctors to diagnose because it usually begins subtly. Diagnosis is especially difficult in older people because aging can cause some of the same problems as Parkinson's disease, such as loss of balance, slow movements, muscle stiffness, and stooped posture. To exclude other causes of the symptoms, doctors ask about previous disorders, exposure to toxins, and use of drugs that could cause parkinsonism.
No tests or imaging procedures can directly confirm the diagnosis. However, computed tomography (CT) and magnetic resonance imaging (MRI) may be done to look for a structural disorder that may be causing the symptoms. Single-photon emission computed tomography (SPECT) and positron emission tomography (PET) can detect brain abnormalities typical of the disease. However, SPECT and PET are currently used only in research facilities.
If the diagnosis is unclear, doctors may give the person levodopa, a drug used to treat Parkinson's disease. If levodopa results in clear improvement, Parkinson's disease is likely.
There is no known cure for Parkinson's disease. The goal of treatment is to control symptoms.
If the disease progresses beyond minor symptoms, drug treatment may be indicated. Drug therapy for Parkinson's typically provides relief for 10-15 years or more. The most commonly prescribed medication is L-dopa (levodopa) which helps replenish some of the lost dopamine in the brain. Sinemet, a combination of levodopa and carbidopa, is the drug most doctors use to treat Parkinson's disease. Recent clinical studies have suggested that the class of drugs called "dopamine agonist" should be used prior to levodopa (Sinemet) except in patients with cognitive problems or hallucinations. In those older than 75, dopamine agonists should be used cautiously because of an added risk of hallucinations. Other drugs are also used and new drugs are continually being tested. It is common for multiple drugs to be prescribed because many of them work well together to control symptoms and reduce side effects.
It is very important for people with PD to work closely with their physicians. Many of the drugs used to treat Parkinson's become less effective over time so physicians will often try different combinations of drugs as the disease progresses. People with Parkinson's respond differently to drugs so they may need to work with their physician to find the drug or combination of drugs that work for them. It may take several weeks or months before a drug begins to work. Many Parkinson's drugs can also "wear off" in between doses during the day so people with PD need to pay close attention to the times they take their medications and to plan their activities carefully.
Side effects of medications can also be a problem. For some medications the side effects are most severe when the person first begins taking the drug and gradually disappear or lessen. For other medications, side effects may appear after several years. For example, long-term levodopa use may result in large uncontrollable movements (nodding, twitching or jerking) called "dyskinesia" or "on-off" attacks where the person will become frozen (can't move) for a few seconds or minutes. Confusion may develop as a side effect after about eight years.
Surgery: Surgery for the treatment of Parkinson's is used when symptoms become very disabling and are not responding to drug therapy. Additionally, people that undergo surgery must be in good health overall, younger than 70, and mentally competent (no cognitive symptoms or dementia). Different symptoms are improved depending on the area of the brain that is targeted. Surgery on the left side of the brain will improve symptoms on the right side of the body and surgery on the right side will improve symptoms on the left side of the body. There are three types of surgery for PD: lesioning (ablative), deep brain stimulation (DBS), and restorative (transplants).
In lesioning surgery, a very small part of the brain is destroyed. Deep brain stimulation involves the implantation of a small wire in the brain through which high frequency stimulation can be sent by the person to control his or her symptoms. Surgery can be performed bilaterally (both sides) or unilaterally (one side). In most cases, it is recommended that individuals undergo surgery on only one side to begin with and, if successful, their physician may recommend DBS on the other side if needed.
In restorative surgery, new nerve cells are implanted in the brain to take the place of the nerve cells that have died. In the United States, lesioning surgery and one form of DBS (stimulation of the thalamus) have been approved as treatments. Two other forms of DBS and restorative surgery are still considered experimental.
The surgery for both lesioning and DBS is similar. The person's head is secured in a frame to keep it from moving and imaging is done so that the surgeon has a clear picture of the brain. A small hole is made in the skull and a very thin wire is inserted into the brain. The surgeon uses several methods to determine when the wire is exactly in place, including having the individual move and observing how the wire affects symptoms. For this reason, the person is awake during the surgery.
In lesioning surgery, once the physician has located the specific area for treatment, an electrical current is sent down the wire and a small area of nerve cells is destroyed. In DBS, the wire is left in the brain and is attached to a small device implanted under the skin on the individual's chest (similar to a pacemaker). Using a magnet, the person can then turn the stimulator on or off. The amount of stimulation can be programmed by the physician to provide the maximum amount of symptom relief. DBS is usually done as two separate surgeries, one to implant the generator and one to implant the wire.
Restorative surgery is still experimental. Two types of restorative surgery are currently being tested, one using human fetal tissue and the other using fetal tissue from pigs. The goal of the surgery is to implant cells (dopamine-producing nerve cells) that will replace those that have died. Several studies have been done and the operations seem to have been successful for some individuals. These surgical options have the added risk of possible tissue rejection. In the future, surgeons may be able to transplant genetically engineered cells from the person's own body and thus lower the risk of rejection. As in drug therapy for PD, new techniques and ideas for the surgical treatment of PD are continually arising.
Lesioning & DBS Surgery
Thalamotomy: Lesioning surgery in which a small portion of the thalamus is destroyed.
Pallidotomy - Lesioning surgery in which a portion of the globus pallidus is destroyed. Long-term studies indicate that the improvements may last for five years or longer.
Improves: Dyskinesia, Rigidity, Tremor.
STN DBS — Deep brain stimulation of the subthalamus nucleus. May be the most promising surgery. Not approved by FDA.
Improves: Slowness, Rigidity, Tremor, Dyskinesia, "On-Off" problems, Increases "On" time, Reduction in levodopa needed.
Thalamus DBS — Deep brain stimulation of the thalamus.
GPi DBS - Deep brain stimulation of the globus pallidus, pars interns. Usually done bilaterally. Not approved by FDA.
Medicine and medications:
The following are the medications used in the treatment of Parkinson's Disease. Each will be considered below.
Levodopa with carbidopa: Sinemet TM, Sinemet CRTM.
Levodopa with benserazide: Prolopa TM.
COMT Inhibitors: Entacapone (Comtan TM), Tasmar TM.
Dopamine agonists: Pramipexole Mirapex TM, ropinerole (Requip TM), bromocriptine (Parlodel TM), pergolide (Permax TM).
Other medications: Amantadine (Symmetrel TM), benztropine (Cogentin TM), trihexyphenydil (Artane TM), deprenyl (Eldepryl TM).
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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