Published: Oct. 17, 2006
Updated: Apr. 28, 2010
Learn about current clinical trials for patients with Parkinson's Disease
The death of the Pope John Paul II, who suffered from Parkinson's disease (PD), and the ongoing struggles of Muhammad Ali, Janet Reno, and Michael J. Fox have raised awareness of PD, which affects about 1.5 million Americans.
PD originates in the substantia nigra, an area deep in the brain that produces dopamine, a chemical that helps coordinate movement and muscle control. In Parkinson's, the cells that produce dopamine die off, leading to the gradual onset of stiffness and rigidity, tremors, and problems with balance.
PD is most commonly diagnosed in people in their 50s and 60s, although the disease can strike anyone from their 30s to their 70s. Some 60,000 new cases are diagnosed each year nationwide.
While there is currently no cure for PD, recent advances have helped stabilize symptoms of the movement disorder and improved the quality of life for Parkinson's patients. "When I discuss a PD diagnosis with anyone," says neurologist Mark Stacy, MD, director of Duke's Movement Disorders Program, "I emphasize the clinical data demonstrating that most people with the disease will do extremely well for many years."
The drug levodopa (also called L-dopa), which is converted to dopamine in the brain, has been the standard treatment for PD since it was introduced more than 30 years ago. Dopamine agonist therapies (drugs that stimulate the brain cells that require dopamine), provided by drugs such as ropinirole (Requip) or pramipexole (Mirapex), are also often prescribed for many newly diagnosed patients.
"More recently, drugs such as entacapone and tolcapone have been shown to enhance levodopa's benefit," Stacy says. "Entacapone, combined with carbidopa/levodopa, is now marketed under the trade name Stalevo."
As Parkinson's disease progresses, the brain makes less and less dopamine, and patients require greater amounts of medication to manage the condition. Drug regimens can become more complicated and dosage levels can fluctuate, leading to ineffective treatment and negative side effects.
In addition to new treatment strategies, Duke neurologists are testing new imaging techniques -- including one known as an altropane SPECT brain scan -- that may help visualize neurologic changes caused by PD much earlier in the disease process.
"If we could do that," says Burton Scott, MD, a neurologist who specializes in movement disorders, "we could give people neuroprotective drugs early on to slow progress of disease. Patients with any type of tremor are needed for this study, as we're trying to differentiate the brains of people who have Parkinson's tremors from those of people with tremors that aren't caused by PD."
Duke physician-scientists are also making significant advances in teasing out the secrets of Parkinson's as a first step in the development of new treatments. Within Duke's Deane Laboratories, chief of neurology Warren Strittmatter, MD, leads efforts to use new understanding to identify potential targets for drug discovery.
Physical therapy is vitally important to living better with PD, says Linda Cates, a senior physical therapist with the movement disorders program at Duke. "The decrease in activity and movement associated with Parkinson's disease can lead to a loss of flexibility, poor endurance, or weakness," says Cates. "An active lifestyle, including exercise, can substantially improve quality of life. This is a disease where the adage 'Use it or lose it' truly applies."
Occupational therapy is another quality-of-life cornerstone for PD patients. Patients learn new or safer ways to perform activities of daily living such as bathing, dressing, eating, grooming, and driving, "We help people learn ways to conserve their energy and maximize their endurance," says Fay Tripp, a senior occupational therapist at Duke. "We also help Parkinson's patients find and use adaptive equipment such as special utensils, braces, and tub benches, which can enable them to live independently for as long as possible."
Even as today's PD patients have access to a range of effective treatments and supportive strategies to manage their condition, innovative therapies are showing great promise. Some of Scott's patients have had good results from deep brain stimulation. Approved for use to treat Parkinson's disease in 2002, the therapy uses an implanted device known as a neurostimulator to stimulate centers in the brain and thus counter the brain signals that cause symptoms. "This approach can be a good option for people who have had PD for awhile and are no longer responding sufficiently well to their medications," Scott says.
Clinical trials are a key part of the equation. "The medications we use now to control Parkinson's symptoms were developed with the help of patients who were willing to use them experimentally," Scott says. "So we're always looking for patients who can help us test new approaches. The only way to continue developing better treatments is by testing them in clinical trials -- ideally with a diverse patient population. We want to make sure that the treatments we're developing will be helpful for all people who have Parkinson's, and you can't do that unless you have different ethnic groups participating in the research.
"People who are willing to participate in these studies sometimes choose to do so for noble reasons -- for the patients that come after them," Scott adds. "And sometimes the new therapies improve the lives of the study participants themselves."
"The resources we've assembled at Duke to fight movement disorders such as Parkinson's are very complementary," says Stacy. "Together, we have the tools we need to find a cure."