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News In Brief

Study on Deep Brain Stimulation Shows Benefits and Risks

A new report published in the Journal of the American Medical Association on January 7, shows that the surgical technique known as deep brain stimulation (DBS) is more effective than currently available medications in easing many motor symptoms of advanced Parkinson’s disease (PD), but also presents a greater risk of complications.

This study, led by Frances M. Weaver, Ph.D., of the US Department of Veterans Affairs and her colleagues from the CSP 468 Study Group, is the largest and most comprehensive investigation ever conducted on the use of DBS.

The double-blind, placebo-controlled trial studied 255 people with PD — over 80 percent of whom were male — between 2002 and 2005 at 13 hospitals across the US.  Half of these individuals underwent deep brain stimulation, while the other half received “best medical therapy” — that is, currently-available PD medications that were adjusted throughout the study by neurologists specializing in Parkinson’s.  The participants had an average age of 62 years and had been taking PD medications for an average of 12 years.  One fourth of the participants were aged 70 years or older.   

To study the effects of DBS, Dr. Weaver’s team collected information from each person at the beginning of the study and at three months and six months after surgery.  Using standard rating scales, they measured changes in motor symptoms and quality of life.  They also recorded medication usage and finger tapping speed and conducted tests of mood and thinking ability.  The primary study results came from daily diaries, in which participants recorded the amount of time they spent each day in an “on” state, when their medications were most effective and their mobility was at its best.

While both groups reported clinically meaningful improvement in their ability to function, individuals who had DBS experienced an increase in “on” time by almost five hours a day, as compared to those who used medication alone.  The improvement in the amount of daytime mobility was accompanied by a decrease in dyskinesias, which are medication-induced twisting and writhing movements.  These improvements held for people over 70 years of age and those who were younger.

However, the study found that those in the surgery group experienced a higher number of adverse events, such as confusion, headache, speech problems, gait disturbances and falling.  For most people, these complications proved temporary and were resolved after six months.

The results of this large study confirm the findings of prior, smaller studies, and reinforce the current standards of medical practice (see PDF’s 2008 booklet, Deep Brain Stimulation for Parkinson’s Disease, Third Edition).  DBS remains the most significant advance in the treatment of PD over the last decade, but many questions remain unanswered, including the optimal timing of surgery and its long-term outcome. 

Christopher Goetz, M.D., Chair of PDF’s Medical Policy Committee, said of the new report, “The amount of increased “on” time in the surgically treated group was substantial (almost five hours), which is much greater than that demonstrated with new medications for Parkinson’s motor fluctuations.  The disturbing reality, however, is that serious adverse events were much higher in the group that received DBS than in the group that received the best available medical therapies.  Therefore, clinicians and patients must weigh the risks of surgery carefully as they consider surgery or continued medical treatment for Parkinson's disease.” 

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Trial of Promising Experimental Medication Fails to Show Efficacy

In late November, a report of the results of a Phase II clinical trial of CERE-120, a potential new treatment for Parkinson’s disease (PD), showed no evidence that the treatment is effective.  CERE-120 is composed of a viral vector carrying the gene for neurturin, a naturally occurring protein that helps neurons to remain alive and healthy.  Researchers had hoped to use it to repair and protect the neurons lost and damaged by Parkinson’s, potentially easing the symptoms of PD.  

Ceregene Inc., the manufacturer of CERE-120, reported that the trial, “did not demonstrate an appreciable difference” between people with PD treated with CERE-120 and the members of a control group who received sham surgery.  Data from the trial have not yet been released.

The double-blind and placebo-controlled trial involved 58 people with advanced Parkinson’s, enrolled in nine US centers.  Each participant in the treatment group received one dose of CERE-120 through a surgical procedure, and was observed for a period of 12 months.  Members of both the treatment group and the control group showed similar levels of improvement in symptoms.  However, while the medication did appear to be safe and well tolerated, there was no evidence to show that CERE-120 contributed to any of the improvements in the treatment group. 

PDF looks forward to reviewing data from this trial when it becomes available, at which point we will update you via our website and newsletter.  While the reported results are disappointing for the PD community, doctors working with PDF note that there are other promising medications in the pipeline.  To learn about these, take a look at two articles that appeared recently in News & Review.  These are: Medications for Parkinson’s Disease: What’s on the Horizon?, from the Fall 2008 issue, authored by David Sommer, M.D., M.P.H., and Mark Stacy M.D., of Duke University; and A New Generation of Anti-Parkinson Treatments: Are We There Yet?, from the Spring 2008 issue, authored by Marina Emborg M.D., Ph.D., of the University of Wisconsin.  Visit www.pdf.org to view these or call us at (800) 457-6676 to request copies. 

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Stem Cell Potential in Human Testes 

Researchers have transformed cells taken from human testes — the cells that normally produce sperm cells — and given them the ability to become any type of cell in the body.  According to the study published in the October 8 online issue of Nature, the transformed cells have potential similar to that of human embryonic stem cells (hESCs), but do not raise the same ethical and political controversies.

Lead researcher Thomas Skutella, M.D., along with his fellow researchers at the University of Tubingen in Germany, collected tissue from the testes of 22 men ranging in age from 17 to 81.  From these samples, they isolated the precursor cells of sperm and immersed them in a culture filled with a molecule called leukemia inhibitory factor (LIF).  

Researchers found that after three to four weeks in the culture, the precursor cells had grown into colonies of cells that resembled embryonic stem cells in both make-up and behavior.  They called these new entities “germline stem cells” (GSCs). 

In addition to finding that the GSCs had the ability to become any type of cell in the body (one of the most prized characteristics of an hESC), Dr. Skutella and his colleagues discovered that when they injected the GSCs into animals, the animals developed teratomas, or tumors — which is exactly what embryonic stem cells would produce in the same situation.

From a treatment perspective, the ability of GSCs to become other cell types is crucial because it offers the potential of transforming these into other types of cells lost or damaged by disease.  In the case of Parkinson’s, this would mean coaxing the cells to become neurons and injecting them into the brains of people with Parkinson’s to replace dying brain cells. 

This study is not the first to produce embryonic-like stem cells.  In the past year, teams from Japan and Wisconsin published reports on a different method that derived hESC-like cells from human skin cells.  Dr. Skutella and his team acknowledge these successes, but believe their method is an improvement.  They note that GSCs do not require significant manipulations (the other method, known as iPS, uses viruses to manipulate adult skin cells back to an earlier state) and therefore avoid the risks associated with such manipulations, one of which is cancer.

The authors also note that development of alternative sources of stem cells may encourage research into what they call ‘personalized medicine’ for Parkinson’s —treatments in which a person would be treated with his or her own body cells, eliminating any problems of immune rejection by the body.  While research in this area is only beginning, investigators hope that their promising results will encourage others to study the technique as a means of treating diseases such as Parkinson’s. 

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Low Vitamin D Levels Associated with Parkinson’s Disease

People with Parkinson’s disease (PD) are more likely than people who have Alzheim­er’s disease (AD) or people who are healthy, to experience a deficiency in vitamin D, according to a study published in the October issue of Archives of Neurology.

Lead researcher Marian L. Evatt, M.D., M.S., and her colleagues at Emory University School of Medicine in Atlanta, GA, measured blood levels of vitamin D in nearly 300 people, of whom 100 had Parkinson’s, 97 had Alzheimer’s disease and 99 were healthy.  The participants, who were recruited between 1992 and 2007, had an average age of 66.  The two control groups (that is, the AD group and the healthy group) were matched to the Parkinson’s group for age and other factors.

The researchers defined two levels of low vitamin D.  One was insufficiency and the other, more severe, was deficiency.  They found that more than half of people with Parkinson’s in the study had vitamin D insufficiency and an additional quarter had a vitamin D deficiency.  This was significantly higher than levels shown among the controls, in which only one-third (of both groups) showed insufficiency and only 16 percent (of the AD group) and 10 percent (of the healthy group) showed deficiency.

Researchers found the relationship intriguing, but could not say whether low levels of vitamin D preceded the onset of PD; whether instead they played a role in the development of PD; or whether perhaps the deficiencies developed because of lifestyle changes caused by the disease.  For example, vitamin D levels are increased by exposure to sunlight and people who have been living with PD for a time may have decreased exposure to sunlight.  The study’s authors also noted that they would have to study other groups of people with PD to see if results would be replicated. 

To understand the role of vitamin D in PD, the same researchers are now investigating whether people with Parkinson’s who receive vitamin D, through exposure to sunlight or ingestion of a nutrition supplement, find any change in their symptoms.  They also noted that, regardless of vitamin D’s effects on PD, the vitamin is known to play an important role in bone health, reducing the risk of falls and fractures, and in preventing certain cancers and autoimmune disorders.  Because of this, the authors conclude, most older people should have their vitamin D levels checked routinely. 

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