March 21 (UPI) -- A new brain operation may reduce the severity of motor problems in people with Parkinson's disease and decrease the amount of medication they need, a new study says.
This treatment helped Parkinson's patients reduce their medication by up to 42 percent, according to findings published Wednesday in the Annals of Neurology.
It also gave patients three extra hours a day of "on-time," the period where medication doesn't cause involuntary muscle movements. This condition is a common side effect called dyskinesia, which is brought on due to long-term medication use.
"This is the first gene therapy trial for Parkinson's disease trial in which intra-operative MRI-guided monitoring was used," Chad Christine, a researcher at the University of California at San Francisco Department of Neurology and study first author, said in a news release. "This allowed us to visualize and guide the infusion of the treatment into the brain in real time, to ensure delivery to the area that should provide maximum benefit."
The drug levodopa helps stabilize symptoms in people with Parkinson's by creating dopamine. Over time, the Parkinson's symptoms -- like shuffling walk, poor balance and falling, and trouble swallowing -- become more severe and prevent levodopa from producing enough dopamine.
The researchers developed a method of gene therapy for increasing an enzyme called AADC, which converts the drug into dopamine. Using an inactive virus, the researchers injected the gene into a part of the brain called the putamen.
For the study, researchers recruited 15 patients between age 40 and 70, dividing them into three groups to receive some form of the experimental therapy.
The first two groups got equal concentrations of gene therapy, but the second group received twice the volume of the infusion, allowing the putamen to spread further. The third group received three times the concentration as the other groups and the same volume as the second group.
Group one saw 1.6 hours of on-time and a 15 percent reduction in medicine, while group two got 3.3 hours and a 33 percent reduction in medicine. Group three got 1.5 hours on-time and a 42 percent reduction in drugs.
"We have evidence from a previous study that the gene therapy results in stable expression of the AADC enzyme," Christine said. "We believe that this treatment will allow these patients to more efficiently convert levodopa into dopamine, thereby obtaining greater improvements in mobility with each dose. Since many patients were able to substantially reduce the amount of Parkinson's medications, this gene therapy treatment may also help patients by reducing dose-dependent side effects, such as sleepiness and nausea."
About 50,000 people are diagnosed with Parkinson's disease in the U.S. each year, according to the National Institutes of Health.
"While results of this phase I trial are promising, there are a number of non-motor features of Parkinson's disease that may develop over time, such as depression, as well as cognitive changes," said Christine. "These conditions do not respond to levodopa and we do not believe that gene therapy will address them."