Parkinson's disease is a progressive disorder of the nervous system that affects movement. It develops gradually, sometimes starting with a barely noticeable tremor in just one hand. But while a tremor may be the most well-known sign of Parkinson's disease, the disorder also commonly causes stiffness or slowing of movement.
In the early stages of Parkinson's disease, your face may show little or no expression, or your arms may not swing when you walk. Your speech may become soft or slurred. Parkinson's disease symptoms worsen as your condition progresses over time.
Although Parkinson's disease can't be cured, medications may markedly improve your symptoms. In occasional cases, your doctor may suggest surgery to regulate certain regions of your brain and improve your symptoms.
Parkinson's disease symptoms and signs may vary from person to person. Early signs may be mild and may go unnoticed. Symptoms often begin on one side of your body and usually remain worse on that side, even after symptoms begin to affect both sides.
Parkinson's signs and symptoms may include:
- Tremor. A tremor, or shaking, usually begins in a limb, often your hand or fingers. You may notice a back-and-forth rubbing of your thumb and forefinger, known as a pill-rolling tremor. One characteristic of Parkinson's disease is a tremor of your hand when it is relaxed (at rest).
- Slowed movement (bradykinesia). Over time, Parkinson's disease may reduce your ability to move and slow your movement, making simple tasks difficult and time-consuming. Your steps may become shorter when you walk, or you may find it difficult to get out of a chair. Also, you may drag your feet as you try to walk, making it difficult to move.
- Rigid muscles. Muscle stiffness may occur in any part of your body. The stiff muscles can limit your range of motion and cause you pain.
- Impaired posture and balance. Your posture may become stooped, or you may have balance problems as a result of Parkinson's disease.
- Loss of automatic movements. In Parkinson's disease, you may have a decreased ability to perform unconscious movements, including blinking, smiling or swinging your arms when you walk.
- Speech changes. You may have speech problems as a result of Parkinson's disease. You may speak softly, quickly, slur or hesitate before talking. Your speech may be more of a monotone rather than with the usual inflections.
- Writing changes. It may become hard to write, and your writing may appear small.
When to see a doctor
See your doctor if you have any of the symptoms associated with Parkinson's disease — not only to diagnose your condition but also to rule out other causes for your symptoms.
In Parkinson's disease, certain nerve cells (neurons) in the brain gradually break down or die. Many of the symptoms are due to a loss of neurons that produce a chemical messenger in your brain called dopamine. When dopamine levels decrease, it causes abnormal brain activity, leading to signs of Parkinson's disease.
The cause of Parkinson's disease is unknown, but several factors appear to play a role, including:
Your genes. Researchers have identified specific genetic mutations that can cause Parkinson's disease, but these are uncommon except in rare cases with many family members affected by Parkinson's disease.
However, certain gene variations appear to increase the risk of Parkinson's disease but with a relatively small risk of Parkinson's disease for each of these genetic markers.
- Environmental triggers. Exposure to certain toxins or environmental factors may increase the risk of later Parkinson's disease, but the risk is relatively small.
Researchers have also noted that many changes occur in the brains of people with Parkinson's disease, although it's not clear why these changes occur. These changes include:
- The presence of Lewy bodies. Clumps of specific substances within brain cells are microscopic markers of Parkinson's disease. These are called Lewy bodies, and researchers believe these Lewy bodies hold an important clue to the cause of Parkinson's disease.
- Alpha-synuclein is found within Lewy bodies. Although many substances are found within Lewy bodies, scientists believe an important one is the natural and widespread protein called alpha-synuclein (A-synuclein). It's found in all Lewy bodies in a clumped form that cells can't break down. This is currently an important focus among Parkinson's disease researchers.
Risk factors for Parkinson's disease include:
- Age. Young adults rarely experience Parkinson's disease. It ordinarily begins in middle or late life, and the risk increases with age. People usually develop the disease around age 60 or older.
- Heredity. Having a close relative with Parkinson's disease increases the chances that you'll develop the disease. However, your risks are still small unless you have many relatives in your family with Parkinson's disease.
- Sex. Men are more likely to develop Parkinson's disease than are women.
- Exposure to toxins. Ongoing exposure to herbicides and pesticides may put you at a slightly increased risk of Parkinson's disease.
Parkinson's disease is often accompanied by these additional problems, which may be treatable:
- Thinking difficulties. You may experience cognitive problems (dementia) and thinking difficulties, which usually occur in the later stages of Parkinson's disease. Such cognitive problems aren't very responsive to medications.
Depression and emotional changes. People with Parkinson's disease may experience depression. Receiving treatment for depression can make it easier to handle the other challenges of Parkinson's disease.
You may also experience other emotional changes, such as fear, anxiety or loss of motivation. Doctors may give you medications to treat these symptoms.
- Swallowing problems. You may develop difficulties with swallowing as your condition progresses. Saliva may accumulate in your mouth due to slowed swallowing, leading to drooling.
Sleep problems and sleep disorders. People with Parkinson's disease often have sleep problems, including waking up frequently throughout the night, waking up early or falling asleep during the day.
People may also experience rapid eye movement sleep behavior disorder, which involves acting out your dreams. Medications may help your sleep problems.
- Bladder problems. Parkinson's disease may cause bladder problems, including being unable to control urine or having difficulty urinating.
- Constipation. Many people with Parkinson's disease develop constipation, mainly due to a slower digestive tract.
You may also experience:
- Blood pressure changes. You may feel dizzy or lightheaded when you stand due to a sudden drop in blood pressure (orthostatic hypotension).
- Smell dysfunction. You may experience problems with your sense of smell. You may have difficulty identifying certain odors or the difference between odors.
- Fatigue. Many people with Parkinson's disease lose energy and experience fatigue, and the cause isn't always known.
- Pain. Many people with Parkinson's disease experience pain, either in specific areas of their bodies or throughout their bodies.
- Sexual dysfunction. Some people with Parkinson's disease notice a decrease in sexual desire or performance.
You're likely to first see your primary care doctor. However, you may then be referred to a doctor trained in nervous system disorders (neurologist).
Because there's often a lot to discuss, it's a good idea to prepare for your appointment. Here's some information to help you get ready for your appointment and what to expect from your doctor.
What you can do
- Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
- Write down key personal information, including any major stresses or recent life changes.
- Make a list of all medications, vitamins and supplements that you're taking.
- Ask a family member or friend to come with you, if possible. Sometimes it can be difficult to remember all of the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
- Write down questions to ask your doctor.
Your time with your doctor is limited, so preparing a list of questions ahead of time will help you make the most of your time together. For Parkinson's disease, some basic questions to ask your doctor include:
- What's the most likely cause of my symptoms?
- Are there other possible causes?
- What kinds of tests do I need? Do these tests require any special preparation?
- How does Parkinson's disease usually progress?
- Will I eventually need long-term care?
- What treatments are available, and which do you recommend for me?
- What types of side effects can I expect from treatment?
- If the treatment doesn't work or stops working, do I have additional options?
- I have other health conditions. How can I best manage these conditions together?
- Are there any brochures or other printed material that I can take home with me? What websites do you recommend?
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions that occur to you during your appointment.
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:
- When did you first begin experiencing symptoms?
- Do you have symptoms all the time or do they come and go?
- Does anything seem to improve your symptoms?
- Does anything seem to make your symptoms worse?
No specific test exists to diagnose Parkinson's disease. Your doctor trained in nervous system conditions (neurologist) will diagnose Parkinson's disease based on your medical history, a review of your signs and symptoms, and a neurological and physical examination.
Your doctor may order tests, such as blood tests, to rule out other conditions that may be causing your symptoms.
Imaging tests — such as MRI, ultrasound of the brain, SPECT and PET scans — may also be used to help rule out other disorders. Imaging tests aren't particularly helpful for diagnosing Parkinson's disease.
In addition to your examination, your doctor may give you carbidopa-levodopa, a Parkinson's disease medication. You must be given a sufficient dose to show the benefit, as low doses for a day or two aren't reliable. Significant improvement with this medication will often confirm your diagnosis of Parkinson's disease.
Sometimes it takes time to diagnose Parkinson's disease. Doctors may recommend regular follow-up appointments with neurologists trained in movement disorders to evaluate your condition and symptoms over time and diagnose Parkinson's disease.
Parkinson's disease can't be cured, but medications can help control your symptoms, often dramatically. In some later cases, surgery may be advised.
Your doctor may also recommend lifestyle changes, especially ongoing aerobic exercise. In some cases, physical therapy that focuses on balance and stretching also is important. A speech-language pathologist may help improve your speech problems.
Medications may help you manage problems with walking, movement and tremor. These medications increase or substitute for dopamine, a specific signaling chemical (neurotransmitter) in your brain.
People with Parkinson's disease have low brain dopamine concentrations. However, dopamine can't be given directly, as it can't enter your brain.
You may have significant improvement of your symptoms after beginning Parkinson's disease treatment. Over time, however, the benefits of drugs frequently diminish or become less consistent, although symptoms usually can continue to be fairly well-controlled.
Medications your doctor may prescribe include:
Carbidopa-levodopa. Levodopa, the most effective Parkinson's disease medication, is a natural chemical that passes into your brain and is converted to dopamine.
Levodopa is combined with carbidopa (Rytary, Sinemet), which protects levodopa from premature conversion to dopamine outside your brain, which prevents or lessens side effects such as nausea.
Side effects may include nausea or lightheadedness (orthostatic hypotension).
After years, as your disease progresses, the benefit from levodopa may become less stable, with a tendency to wax and wane ("wearing off").
Also, you may experience involuntary movements (dyskinesia) after taking higher doses of levodopa. Your doctor may lessen your dose or adjust the times of your doses to control these effects.
Carbidopa-levodopa infusion. The U.S. Food and Drug administration approved a drug called Duopa in 2015. This medication is made up of carbidopa and levodopa. However, it's administered through a feeding tube that delivers the medication in a gel form directly to the small intestine.
Duopa is for patients with more advanced Parkinson's who still respond to carbidopa-levodopa, but who have a lot of fluctuations in their response. Because Duopa is continually infused, blood levels of the two drugs remain constant.
Placement of the tube requires a small surgical procedure. Risks associated with having the tube include the tube falling out or infections at the infusion site.
Dopamine agonists. Unlike levodopa, dopamine agonists don't change into dopamine. Instead, they mimic dopamine effects in your brain.
They aren't as effective as levodopa in treating your symptoms. However, they last longer and may be used with levodopa to smooth the sometimes off-and-on effect of levodopa.
Dopamine agonists include pramipexole (Mirapex), ropinirole (Requip) and rotigotine (given as a patch, Neupro). A short-acting injectable dopamine agonist, apomorphine (Apokyn), is used for quick relief.
Some of the side effects of dopamine agonists are similar to the side effects of carbidopa-levodopa, but also include hallucinations, sleepiness and compulsive behaviors such as hypersexuality, gambling and eating. If you're taking these medications and you behave in a way that's out of character for you, talk to your doctor.
MAO-B inhibitors. These medications include selegiline (Eldepryl, Zelapar) and rasagiline (Azilect). They help prevent the breakdown of brain dopamine by inhibiting the brain enzyme monoamine oxidase B (MAO-B). This enzyme metabolizes brain dopamine. Side effects may include nausea or insomnia.
When added to carbidopa-levodopa, these medications increase the risk of hallucinations.
These medications are not often used in combination with most antidepressants or certain narcotics due to potentially serious but rare reactions. Check with your doctor before taking any additional medications with a MAO-B inhibitor.
Catechol-O-methyltransferase (COMT) inhibitors. Entacapone (Comtan) is the primary medication from this class. This medication mildly prolongs the effect of levodopa therapy by blocking an enzyme that breaks down dopamine.
Side effects, including an increased risk of involuntary movements (dyskinesias), mainly result from an enhanced levodopa effect. Other side effects include diarrhea or other enhanced levodopa side effects.
Tolcapone (Tasmar) is another COMT inhibitor that is rarely prescribed due to a risk of serious liver damage and liver failure.
Anticholinergics. These medications were used for many years to help control the tremor associated with Parkinson's disease. Several anticholinergic medications are available, including benztropine (Cogentin) or trihexyphenidyl.
However, their modest benefits are often offset by side effects such as impaired memory, confusion, hallucinations, constipation, dry mouth and impaired urination.
Amantadine. Doctors may prescribe amantadine alone to provide short-term relief of symptoms of mild, early-stage Parkinson's disease. It may also be given with carbidopa-levodopa therapy during the later stages of Parkinson's disease to control involuntary movements (dyskinesias) induced by carbidopa-levodopa.
Side effects may include a purple mottling of the skin, ankle swelling or hallucinations.
Deep brain stimulation. In deep brain stimulation (DBS), surgeons implant electrodes into a specific part of your brain. The electrodes are connected to a generator implanted in your chest near your collarbone that sends electrical pulses to your brain and may reduce your Parkinson's disease symptoms.
Your doctor may adjust your settings as necessary to treat your condition. Surgery involves risks, including infections, stroke or brain hemorrhage. Some people experience problems with the DBS system or have complications due to stimulation, and your doctor may need to adjust or replace some parts of the system.
Deep brain stimulation is most often offered to people with advanced Parkinson's disease who have unstable medication (levodopa) responses. DBS can stabilize medication fluctuations, reduce or halt involuntary movements (dyskinesias), reduce tremor, reduce rigidity, and improve slowing of movement.
DBS is effective in controlling erratic and fluctuating responses to levodopa or for controlling dyskinesias that don't improve with medication adjustments.
However, DBS isn't helpful for problems that don't respond to levodopa therapy apart from tremor. A tremor may be controlled by DBS even if the tremor isn't very responsive to levodopa.
Although DBS may provide sustained benefit for Parkinson's symptoms, it doesn't keep Parkinson's disease from progressing.
If you've received a diagnosis of Parkinson's disease, you'll need to work closely with your doctor to find a treatment plan that offers you the greatest relief from symptoms with the fewest side effects. Certain lifestyle changes may also help make living with Parkinson's disease easier.
While there's no food or combination of foods proven to help in Parkinson's disease, some foods may help ease some of the symptoms. For example, eating foods high in fiber and drinking an adequate amount of fluids can help prevent constipation that is common in Parkinson's disease.
A balanced diet also provides nutrients, such as omega-3 fatty acids, that may be beneficial for people with Parkinson's disease.
Exercising may increase your muscle strength, flexibility and balance. Exercise can also improve your well-being and reduce depression or anxiety.
Your doctor may suggest you work with a physical therapist to learn an exercise program that works for you. You may also try exercises such as walking, swimming, gardening, dancing, water aerobics or stretching.
Parkinson's disease can disturb your sense of balance, making it difficult to walk with a normal gait. Exercise may improve your balance. These suggestions may also help:
- Try not to move too quickly.
- Aim for your heel to strike the floor first when you're walking.
- If you notice yourself shuffling, stop and check your posture. It's best to stand up straight.
- Look in front of you, not directly down, while walking.
In the later stages of the disease, you may fall more easily. In fact, you may be thrown off balance by just a small push or bump. The following suggestions may help:
- Make a U-turn instead of pivoting your body over your feet.
- Distribute your weight evenly between both feet, and don't lean.
- Avoid carrying things while you walk.
- Avoid walking backward.
Daily living activities
Daily living activities — such as dressing, eating, bathing and writing — can be difficult for people with Parkinson's disease. An occupational therapist can show you techniques that make daily life easier.
Some types of alternative medicine may help people with Parkinson's disease, including:
- Coenzyme Q10. Early research suggested that high doses of coenzyme Q10 — a readily available supplement — may be beneficial for people in the early stages of Parkinson's disease. However, the benefits appear to depend on taking the supplement for 16 months or longer.
- Massage. Massage therapy can reduce muscle tension and promote relaxation. These services, however, are rarely covered by health insurance.
- Acupuncture. During an acupuncture session, a trained practitioner inserts tiny needles into many specific points on your body, which may reduce your pain.
Tai chi. An ancient form of Chinese exercise, tai chi employs slow, flowing motions that may improve flexibility, balance and muscle strength. Tai chi may also prevent falls. Several forms of tai chi are tailored for people of any age or physical condition.
A study showed tai chi may improve the balance of people with mild to moderate Parkinson's disease more than stretching and resistance training.
- Yoga. In yoga, gentle stretching movements and poses may increase your flexibility and balance. You may modify most poses to fit your physical abilities.
- Alexander technique. This technique — which focuses on muscle posture, balance and thinking about how you use muscles — may reduce muscle tension and pain.
- Meditation. In meditation, you quietly reflect and focus your mind on an idea or image. Meditation may reduce stress and pain and improve your sense of well-being.
- Music or art therapy. Music or art therapy may help you to relax. Music therapy helps some people with Parkinson's disease to improve their walking and speech. Participating in art therapy, such as painting or ceramics, may improve your mood and help you relax.
- Pet therapy. Having a dog or cat may increase your flexibility and movement and improve your emotional health.
Living with any chronic illness can be difficult, and it's normal to feel angry, depressed or discouraged at times. Parkinson's disease, in particular, can be profoundly frustrating, as walking, talking and even eating become more difficult and time-consuming.
Depression is common in people with Parkinson's disease. But antidepressant medications can help ease the symptoms of depression, so talk with your doctor if you're feeling persistently sad or hopeless.
Although friends and family can be your best allies, the understanding of people who know what you're going through can be especially helpful. Support groups aren't for everyone. However, for many people with Parkinson's disease and their families, support groups can be a good resource for practical information about Parkinson's disease.
Also, groups offer a place for you to find people who are going through similar situations and can support you.
To learn about support groups in your community, talk to your doctor, a Parkinson's disease social worker or a local public health nurse. Or contact the National Parkinson Foundation or the American Parkinson Disease Association.
You and your family may also benefit from talking to a mental health professional (psychologist) or social worker trained in working with people who have chronic conditions.
Because the cause of Parkinson's is unknown, proven ways to prevent the disease also remain a mystery. However, some research has shown that caffeine — which is found in coffee, tea and cola — may reduce the risk of developing Parkinson's disease. Green tea also may reduce the risk of developing Parkinson's disease.
Some research has shown that regular aerobic exercise may reduce the risk of Parkinson's disease.
Expertise and experience. Mayo Clinic doctors have expertise and experience in evaluating and treating people with Parkinson's disease and other nervous system (neurological) conditions. Doctors trained in movement disorders evaluate and treat people with Parkinson's disease and other movement disorders.
Mayo Clinic doctors evaluate and treat about 4,400 people with Parkinson's disease each year.
- Teamwork. Mayo Clinic doctors trained in nervous system conditions (neurologists), nervous system surgery (neurosurgeons) and other areas collaborate to provide your care.
Treatment expertise. Parkinson's disease can't be cured, but your doctor will work with you to help you manage your condition. Your doctor will tailor your treatment to your individual needs depending on the severity of your condition, your age and the presence of other medical conditions.
Mayo Clinic doctors have expertise treating Parkinson's disease with several options, including medications and deep brain stimulation.
- Research leaders. Mayo Clinic movement disorder specialists study genetics, diagnosis, and treatment options for people with Parkinson's disease and other movement disorders. You may have the opportunity to participate in research studies.
Mayo Clinic in Rochester, Minn., ranks No. 1 for neurology and neurosurgery in the U.S. News & World Report Best Hospitals rankings. Mayo Clinic in Scottsdale, Ariz., and Mayo Clinic in Jacksonville, Fla., are ranked among the Best Hospitals for neurology and neurosurgery by U.S. News & World Report. Mayo Clinic also ranks among the Best Children's Hospitals for neurology and neurosurgery.
Mayo Clinic works with hundreds of insurance companies and is an in-network provider for millions of people. In most cases, Mayo Clinic doesn't require a physician referral. Some insurers require referrals or may have additional requirements for certain medical care. All appointments are prioritized on the basis of medical need.
Doctors trained in neurology and neurosurgery diagnose and treat people with Parkinson's disease at Mayo Clinic in Phoenix/Scottsdale, Arizona. The staff of the Parkinson's Disease and Movement Disorders Clinic also treats people with Parkinson's disease.
For appointments or more information, call the Central Appointment Office at 800-446-2279 (toll-free) 8 a.m. to 5 p.m. Mountain Standard Time, Monday through Friday or complete an online appointment request form.
- U.S. Patients
- International Patients
Doctors trained in neurology and neurosurgery diagnose and treat people with Parkinson's disease at Mayo Clinic in Jacksonville, Florida. Staff in the Movement Disorders Program evaluates and treats people with Parkinson's disease and other movement disorders.
For appointments or more information, call the Central Appointment Office at 904-953-0853 8 a.m. to 5 p.m. Eastern time, Monday through Friday or complete an online appointment request form.
- U.S. Patients
- International Patients
Doctors trained in neurology and neurosurgery diagnose and treat people with Parkinson's disease at Mayo Clinic in Rochester, Minnesota. Members of the Movement Disorders Subspecialty Group also treat people with Parkinson's disease and other movement disorders.
For appointments or more information, call the Central Appointment Office at 507-538-3270 7 a.m. to 6 p.m. Central time, Monday through Friday or complete an online appointment request form.
- U.S. Patients
- International Patients
See information on patient services at the three Mayo Clinic locations, including transportation options and lodging.
Mayo Clinic doctors trained in nervous system conditions (neurologists) and other specialties conduct extensive research in genetics, causes, new diagnostic tests, and treatments for Parkinson's disease and other movement disorders. For example, Mayo researchers have found that testing a person's saliva gland may be helpful in confirming a diagnosis of Parkinson's disease, and as a tool for researchers to understand how Parkinson's disease develops.
Doctors study potential causes and possible treatments for Parkinson's disease. Doctors also conduct research in deep brain stimulation to treat Parkinson's disease and other movement disorders. You may have the opportunity to participate in research studies or clinical trials.
Read more about research in:
See a list of publications by Mayo Clinic doctors on Parkinson's disease on PubMed, a service of the National Library of Medicine.
Read about Mayo Clinic publications regarding:
- Advancing Parkinson's disease research through the National Brain and Tissue Resource
- Charles H. Adler, M.D., Ph.D.
- J. Eric Ahlskog, M.D., Ph.D.
- Eduardo E. Benarroch, M.D.
- Joanna M. Biernacka, Ph.D.
- James H. Bower, M.D.
- John N. Caviness, M.D.
- Dennis W. Dickson, M.D.
- Erika D. Driver-Dunckley, M.D.
- Julie A. Fields, Ph.D., L.P.
- Anhar Hassan, M.B., B.CH.
- Bryan T. Klassen, M.D.
- Kendall H. Lee, M.D., Ph.D.
- Joseph Y. Matsumoto, M.D.
- Pamela J. McLean, Ph.D.
- Shyamal H. Mehta, M.D., Ph.D.
- Leonard Petrucelli, Ph.D.
- Rosa Rademakers, Ph.D.
- Elliott Richelson, M.D.
- Walter A. Rocca, M.D.
- Owen A. Ross, Ph.D.
- Wolfdieter Springer, Ph.D.
- Ryan J. Uitti, M.D.
- Jay A. Van Gerpen, M.D.
- Robert E. Wharen Jr., M.D.
- Zbigniew K. Wszolek, M.D.
- Shu-Hui C. Yen, Ph.D.
July 07, 2015
- Longo DL, et al. Parkinson's disease and other movement disorders. In: Harrison's Principles of Internal Medicine. 18th ed. New York, N.Y.: The McGraw-Hill Companies; 2012. http://accessmedicine.com. Accessed April 6, 2015.
- Parkinson's disease: Hope through research. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/parkinsons_disease/detail_parkinsons_disease.htm. Accessed April 6. 2015.
- Ferri FF. Parkinson's disease. In: Ferri's Clinical Advisor 2015: 5 Books in 1. Philadelphia, Pa.: Mosby Elsevier; 2015. https://www.clinicalkey.com. Accessed April 6, 2015.
- Chou KL. Diagnosis of Parkinson disease. http://www.uptodate.com/home. Accessed April 6. 2015.
- Tarsy D. Pharmacologic treatment of Parkinson disease. http://www.uptodate.com/home. Accessed April 6. 2015.
- Adler CH, et al. Submandibular gland needle biopsy for the diagnosis of Parkinson disease. Neurology. 2014;82:858.
- Bousquet M, et al. Impact of omega-3 fatty acids in Parkinson's disease. Ageing Research Reviews. 2011;10:453.
- Parkinson's disease: Fitness counts. National Parkinson Foundation. http://www.parkinson.org/Search-Pages/Search.aspx?pKeywords=fitness. Accessed April 9, 2015.
- Parkinson's disease. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed April 6, 2015.
- Tarsy D. Nonpharmacologic management of Parkinson disease. http://www.uptodate.com/home/. Accessed April 6, 2015.
- Complementary therapies and Parkinson's. Parkinson's Disease Society of the United Kingdom. http://www.parkinsons.org.uk/content/complementary-therapies-and-parkinsons-booklet. Accessed April 9, 2015.
- Jankovic J. Etiology and pathogenesis of Parkinson disease. http://www.uptodate.com/home. Accessed April 6, 2015.
- Riggs EA. Decision Support System. Mayo Clinic, Rochester, Minn. April 16, 2015.
- Abbvie announces U.S. approval of duopa (carbidopa and levodopa) enteral suspension for the treatment of motor fluctuations in patients with advanced Parkinson's disease. http://abbvie.mediaroom.com/2015-01-12-AbbVie-Announces-U-S-FDA-Approval-of-DUOPA-carbidopa-and-levodopa-Enteral-Suspension-for-the-Treatment-of-Motor-Fluctuations-in-Patients-with-Advanced-Parkinsons-Disease. Accessed April 20, 2015.
- Bower JH (expert opinion). Mayo Clinic, Rochester, Minn. April 20, 2015.