In 1993, French scientists first reported that electrodes implanted into the brains of people with Parkinson’s disease could drastically improve motor function and slow disease progression. And in the intervening two decades, this surgical technique, known as deep brain stimulation (DBS), has been used in around 60,000 people with the neurodegenerative disease. But given the brief availability of DBS, researchers have a poor understanding of how well the treatment works in the long-term. A new study, however, suggests that the treatment can improve the symptoms of Parkinson’s disease patients even up to a decade after doctors first implant electrodes.
“DBS is one of the only options for people more advanced with the disease, so the fact that it continues to be a good option for people in the long-term is certainly newsworthy,” says Brian Fiske, director of research programs at the New York–based Michael J. Fox Foundation for Parkinson’s Research.
The dopamine-precursor levodopa is the most common treatment for Parkinson’s disease. Yet, after just a few years, people often develop resistance to the drug as the brain learns to compensate for the extra neurotransmitters. This resistance leads to side effects, including an involuntary movement disorder known as dyskinesia. Thus, researchers have long sought longer-term fixes for the motor neuron disease, and DBS — first developed in the 1980s to treat pain — provides an attractive option.
DBS isn’t a perfect treatment, though. Some people complain of hallucinations, depression and cognitive dysfunction. Additionally, the technology is expensive and requires regular surgery for upkeep, thereby increasing risk for brain bleeding or infection. What’s more, in the longest trial to date, which lasted 8 years, researchers from the Sacro Cuore Catholic University in Rome found that the intervention loses its efficacy over time, leading experts to question whether the approach actually lives up to its early promise.
The latest study, published online today in the Archives of Neurology, indicates that it does. In the report, a team led by Anna Castrioto from the University of Perugia in Italy tracked 18 people who underwent electrode implantation surgery in the mid- to late-1990s. After one, five and ten years, the researchers assessed each study subject’s motor skills, day-to-day tasks and behavior while receiving stimulation or not. Participants performed significantly better overall when stimulated at each time point, even after 10 years, the researchers found. Their motor skills in particular improved, although posture and balance declined.
These results don’t indicate that DBS prevents decline in Parkinson’s patients. But they suggest that DBS slows the decline and improves symptoms. The authors note caveats including the high drop-out rate, small sample size and lack of control group. In particular, the lack of control subjects weakens the conclusion, as study subjects could be responding to withdrawal from DBS and not to its beneficial effects alone.
Image: Wikimedia Commons via Hellerhoff