There is no cure for Parkinson's disease. Since most of the symptoms are due to the lack of dopamine in the brain, effective medications aim at temporarily replenishing or mimicking dopamine's actions. These drugs - levodopa and the dopamine agonists ropinirole, pramipexole, and pergolide - reduce muscle rigidity, improve speed and coordination of movement, and relieve tremor. In addition, many doctors recommend physical therapy or muscle-strengthening exercises to help people handle their daily activities.

In some cases, surgery may be appropriate if the disease doesn't respond to drugs. A therapy called deep brain stimulation (DBS) has now been approved by the U.S. Food and Drug Administration. In DBS, electrodes are implanted into the brain and connected to a small electrical device called a pulse generator that can be externally programmed. DBS can reduce the need for levodopa and related drugs, which in turn decreases the involuntary movements called dyskinesias that are a common side effect of levodopa. It also helps to alleviate fluctuations of symptoms and to reduce tremors, slowness of movements, and gait problems. DBS requires careful programming of the stimulator device in order to work correctly.

At present there is no way to predict or prevent Parkinson's disease. Symptoms usually appear after 80 percent or more of the dopamine-producing neurons in the substantia nigra have died, which significantly narrows the window of opportunity for preventive or protective treatments. Medications can relieve symptoms for a period of time but won't slow or stop the natural progression of the disease. The course of the disease varies widely. Some people have mild symptoms for many years, while others have severe symptoms and a quicker progression.

Hundreds of research studies supported by the NINDS are exploring the basic biomechanisms of Parkinson's disease and looking for ways to stop the degenerative process that causes the disorder. Clinical trials across the country are investigating new medications and therapies to find ways to improve the lives of people with Parkinson's disease. For example:

• Studies are looking at how Lewy bodies - the characteristic dense clumps of abnormal protein that are found in the neurons of people with Parkinson's disease - are involved in the disease process. Some researchers believe Lewy bodies are the cause of neuron death, others see them more as a byproduct of the neurodegenerative process, and still others believe they are a protective mechanism employed by the neuron to lock away abnormal and harmful proteins. Discovering how Lewy bodies work, and why, may open doors to potential interventions that could prevent the cascade of biological events that cause the neurodegeneration of Parkinson's disease.
• Several groups of researchers are exploring new opportunities for drug development by studying neurotrophins, molecules in neurons that support growth and survival. Understanding how neurotrophins work could lead to the development of drugs that stop the degeneration of dopamine cells and heal those that are already damaged. Another avenue of exploration involves neuroprotective substances in cells - molecules that protect neurons from harm. NINDS is currently supporting a series of pilot clinical trials to test the effects of four potential neuroprotectants.
• Cell transplantation is one way of repairing the damage Parkinson's disease causes in the brain. In laboratory experiments, researchers are studying embryonic stem cells, adult stem cells, and other types of promising cells to see if they can be coaxed into turning into dopamine-producing neurons. In studies using animal models, researchers are looking at what these new neurons need to survive, make the proper connections, and become fully functional cells in the brain.