Parkinson's disease is a progressive disorder caused by the degeneration of certain nerve cells in the brain. The degeneration of these nerve cells causes decreased levels of a brain chemical called dopamine. Dopamine levels are low in Parkinson's patients compared to the rest of the population.
Dopamine is essential in the chemical process which transmits signals from one group of brain cells to another to facilitate movement. As dopamine-producing cells are lost, many types of regular movement are affected. By the time symptoms of Parkinson's disease appear, approximately half or more of these cells have been lost.
For more information about Parkinson's disease, or to schedule an appointment, call (206) 341-1900.
BJ Swensson discusses deep brain stimulation and Parkinson's disease.
Though no one knows exactly what causes the degeneration of nerve cells that leads to Parkinson's, risk factors for Parkinson's disease include:
- Age - Parkinson's typically affects people in middle or later life, and the risk increases with age.
- Heredity - Having one or more close relatives with Parkinson's increases the chances that you'll also develop the disease, although your risk is still less than 5 percent. Recent evidence suggests a crucial role for small contributions from many different genes that program brain architecture.
- Sex - Men are more likely to develop Parkinson's disease than women are.
- Exposure to toxins - Ongoing exposure to herbicides and pesticides puts you at slightly increased risk of Parkinson's.
Early signs of Parkinson's disease may be hard to detect. Individual symptoms vary and can be present in a mild form for months or years before a patient seeks diagnosis. Frequently symptoms will first affect one side of the body. Parkinson's symptoms may include:
- Tremor - Shaking or tremor may begin in one hand. Other movements, such as a back-and-forth rubbing of the thumb and forefinger, are also common. However, many people who have Parkinson's disease do not develop substantial tremor.
- Slowed motion (bradykinesia) - Parkinson's disease may progressively reduce the ability to initiate voluntary movement, including walking. Steps may become short and shuffling. Sometimes freezing occurs, making it hard to take a step or roll over in bed.
- Rigid muscles - Muscle stiffness in the limbs or neck is a common symptom of Parkinson's disease.
- Problems with posture - Posture may become stooped as a result of Parkinson's disease. In later stages of the disease balance can also be affected.
- Impairment of automatic movements - Facial expressions and movements, such as blinking and smiling may be diminished or lost as a result of Parkinson's. Other automatic movements can be affected as well, including gesturing while talking.
- Speech changes - Parkinson's can affect speech. Some patients develop rapid speech, repeat words or speak in a monotone.
- Dementia - Signs of memory problems or confusion may surface in the later stages of Parkinson's disease. Alzheimer's drugs have shown some benefit in reducing these symptoms in certain patients.
Because there is no specific test to confirm Parkinson's, it can be difficult to diagnose, especially in the early stages. In addition, there are other medical problems that can cause symptoms similar to Parkinson's, including:
- Stroke - Stroke can cause impairment that resembles the symptoms of Parkinson's.
- Other neurological disorders - Other conditions such as dementia, essential tremor and others have signs and symptoms that are similar to Parkinson's.
- Medication - Drugs that block the brain chemical dopamine can temporarily cause the signs of Parkinson's. These symptoms, however, are reversible when the drug is stopped.
- Head trauma - Although rare, head injuries can leave the brain susceptible to the conditions leading to Parkinson's.
A neurological examination and taking a medical history form the basis of a Parkinson's disease diagnosis. Family history and current medications are considered, as well as a neurological work-up to assess things like coordination, signs of muscle rigidity or tremor, and the prevalence of symptoms on one side of the body.
In addition to combating the symptoms of Parkinson's with lifestyle changes such as exercise and/or physical therapy, medication therapy can help control Parkinson's symptoms. Because people with the disease have low levels of dopamine, the main drug therapy is based on increasing dopamine levels in the brain.
The drug levodopa contains a substance that occurs naturally in the body. When taken, the drug is converted to dopamine when it reaches the brain. Levodopa is combined with another substance to ensure it does not convert to dopamine before reaching the brain.
As Parkinson's disease progresses, the benefit from levodopa may become less reliable. In addition, levodopa side effects can include confusion, delusions and hallucinations, as well as involuntary movements called dyskinesia. The dose can be reduced to mitigate these side effects, but sometimes at the expense of losing the benefits of symptom control.
Other types of drugs can be used in combination with levodopa to prolong its beneficial effects. Some of these drugs work by blocking the enzymes known to break down dopamine, whether created naturally in the brain or by levodopa. Other types of medication, including anticholinergics and antivirals, are sometimes used to control physical symptoms such as tremor and involuntary movement. However, patients may find that their limited benefits do not offset the sometimes serious side effects.
Deep brain stimulation (DBS) is the most common surgical procedure to treat Parkinson's disease. During the surgery, the neurosurgeon places electrodes in a particular part of the brain. The electrodes are connected by slender wires to a type of pacemaker device called an impulse generator which is implanted under the skin on the chest, below the collarbone.
When the device is activated, a low-level electrical current is sent to the brain, blocking the impulses that cause involuntary movement and tremors. The patient feels no pain with the placement of the electrodes. Sometimes patients undergo two separate surgeries, one for the right side of the brain and another for the left side. The system can be turned on and off by the patient.
DBS is most often used for people who have advanced Parkinson's disease or whose response to medications has decreased or destabilized. Tremor is especially responsive to DBS, however, it doesn't benefit those who have a history of not responding to the drug levodopa. DBS does not treat dementia, and may actually make the condition worse.
Like any other surgery, DBS has risks - such as stroke-like hemorrhaging in the brain. If infection occurs additional procedures may be needed. The unit beneath the skin of the chest contains a battery which must be surgically replaced every few years.
DBS can dramatically change the lives of patients with uncontrollable movement and tremors. Normal activities, such as eating and dressing, can be restored to help patients have more active and fulfilling lives.
Benaroya Research Institute's neurology research program is committed to the discovery of innovative treatments and diagnostic tools for neurological diseases.
A Parkinson's Disease Support Group meets regularly at Horizon House at 900 University Street, across the street from the Health Resources Building in the Virginia Mason Seattle Main Clinic. For more information, please call (206) 230-0166.
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