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Medications for Parkinson's control symptoms but don't slow progression

Tuesday April 24, 2012

chicago tribune.com - DEAR MAYO CLINIC: What are the latest findings on Parkinson's disease? Are there any new medications? I've heard a lot about CoQ10 as a promising alternative for those with Parkinson's. Is there any truth to this?

ANSWER: CoQ10 initially seemed to be a promising therapy for Parkinson's in early research involving small numbers of patients. However, follow-up studies using larger numbers and higher doses have failed to confirm benefit from this drug.

The medications currently available for Parkinson's are directed at controlling symptoms. They can be very effective. Unfortunately, despite decades of intensive research, no drugs have been proven to slow the progression of Parkinson's disease.

Parkinson's disease is a disorder of the nervous system that develops gradually over time. The hallmark symptoms include tremor, muscle rigidity and slowness of movements. In later stages, new symptoms may develop that include difficulties with memory and thinking, as well as bladder and bowel problems and, in some people, low blood pressure.

In the 1960s, researchers discovered that the brains of people with Parkinson's disease are low in a brain chemical called dopamine. This was a huge step forward in understanding and treating the disease. After that, researchers began to focus Parkinson's treatment on replenishing dopamine. The early result of those efforts was a medication known as carbidopa-levodopa, which effectively restores brain dopamine and typically reduces many Parkinson's symptoms. Four decades later, carbidopa-levodopa is still the best drug available for Parkinson's. Although it does not treat the cause, carbidopa-levodopa does restore some of the normal brain chemistry.

Unfortunately, as Parkinson's advances, levodopa and related medications often become less effective in controlling symptoms, and the problems caused by the disease tend to get worse. Thus, with advancing Parkinson's disease, the problems go beyond brain dopamine.

Understanding the cause of Parkinson's disease is the crucial first step to finding a way to slow or halt disease progression. A variety of environmental factors have been identified that influence the risk of developing Parkinson's disease. However, these account for only a small part of this risk. Genetics have also been extensively studied and remain a strong focus among researchers.

Initial genetic studies investigated rare families in which many members had Parkinson's disease. Although gene mutations were identified to explain the cause in many of these families, these same gene mutations were not found to cause Parkinson's disease in general. Known gene mutations account for just a small percent of typical Parkinson's disease. However, these genetic studies shed light on processes that appear to play important roles in causing Parkinson's disease.

One important genetic finding surfaced early in these studies of familial Parkinson's disease. In selected Parkinson's disease families from Italy and Greece, the cause turned out to be the gene coding for alpha synuclein. This gene mutation was not found in run-of-the-mill Parkinson's disease, but led to another important discovery. People with typical Parkinson's disease were found to have deposits of alpha synuclein in affected brain cells, suggesting that this molecule might play an important role in all Parkinson's disease.

Of further interest has been the recognition that people with a disease somewhat similar to Parkinson's but associated with early dementia, called dementia with Lewy bodies, also is marked by brain alpha synuclein deposits. Researchers are now studying the relationship between these two disorders, which appear to have a common link.

Although we do not have a drug that halts the progression of Parkinson's disease, that should not be reason for pessimism. After all, before you can fix either a car or a body, you have to know how it works. That is certainly true for Parkinson's disease. Once we fully understand what causes it, new treatment should quickly follow. -- J. Eric Ahlskog, M.D., Ph.D., Neurology, Mayo Clinic, Rochester, Minn.

(Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care. E-mail a question to medicaledge@mayo.edu , or write: Medical Edge from Mayo Clinic, c/o TMS, 2010 Westridge Drive, Irving, TX 75038. For more information, visit www.mayoclinic.org.)

http://www.chicagotribune.com/health/sns-201204191700--tms--mayoclnctnmc-b20120419apr19,0,7597433.story

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