Ask the MD: Expanded Indication for DBS in Parkinson’s
Last week, the U.S. Food and Drug Administration (FDA) expanded the approved use of deep brain stimulation (DBS) in people with Parkinson's. The surgical therapy is now also indicated for those who have had Parkinson's disease (PD) for at least four years and have recently developed motor complications —"off" times when medication doesn't work well to control symptoms and/or dyskinesia (uncontrolled, involuntary movements). Previously, DBS was offered to people who had Parkinson's for at least five years, so this therapy now will be available at an earlier point in the disease.
DBS Is a Symptomatic Treatment
DBS was initially approved for PD tremor in 1996 and then for advanced Parkinson's in 2002. Like all currently available therapies, DBS is symptomatic. It isn't a cure and won't change the course of the underlying disease. It's also not for everyone because it doesn't work for all of the symptoms of Parkinson's (like balance problems or freezing while walking) and could even make some non-motor symptoms, such as memory or speech problems, worse.
However, in the right candidate, DBS may:
- lessen motor symptoms, such as slowness, stiffness and tremor,
- decrease medication usage (and therefore limit side effects, including motor complications),
- enhance ability to perform routine activities of daily living, and
- improve quality of life.
A 2013 trial published in the New England Journal of Medicine showed that for people with PD who developed motor complications early in the disease course, quality of life improved for those treated with DBS and medication as compared to those treated with medication alone. These results were part of the reason for broadening the indications for use of DBS in Parkinson's.
Choosing and Undergoing DBS Therapy Requires a Complex Process
People considering DBS should have an evaluation by a movement disorder specialist (a neurologist who has extra training in Parkinson's) and a neurosurgeon, who performs the surgery. These doctors review current symptoms and medication history. They also conduct extensive testing, including physical examinations both on and off medications, brain imaging and detailed memory testing (to detect any memory/thinking problems that could worsen with DBS).
Talking through this option with one's loved ones and physicians is important. Although the procedure is generally safe, it is brain surgery and comes with certain risks (e.g., infection, bleeding). Every individual's response to DBS is dependent on his or her symptoms and situation so discussing expectations of benefits prior to the procedure is also key.
In the actual surgery, thin wires called electrodes are implanted in to one or both sides of the brain in the areas that control movement — either the subthalamic nucleus or the globus pallidus. The wires are then connected to a small device in the chest, a pulse generator (much like a pacemaker), which sends electrical signals through the wires into the brain.
A few weeks after surgery, settings tailored to each person are programmed into the DBS device by a movement disorder specialist. These are gradually tweaked over time to give the most benefit and fewest side effects, and medications are usually adjusted at the same time. Finding the right combination of DBS settings and medications can take months or even up to a year. Every five to 10 years, depending on the type of pulse generator and the settings, the battery may need to be replaced.
Currently, the only DBS system available is made by the company Medtronic, but others are in development.
DBS Works by Affecting Abnormal Brain Signaling Patterns
Although the mechanisms are not completely clear, DBS is thought to work by regulating abnormal signaling patterns in the brain. In order to control movement and other normal bodily functions, brain cells communicate with each other using electrical signals (and brain chemicals). In PD, these electrical signals become irregular and uncoordinated, and people experience motor (and other) symptoms. DBS affects disjointed signals to allow the cells to communicate more smoothly and thereby lessen symptoms.
Studies Are Working to Improve and Expand DBS
Researchers are working to improve the experience of DBS systems and expand its use for even more people and more symptoms. One example is DBS targeting a different area of the brain (the pedunculopontine nucleus) to treat the walking and balance problems that don't typically improve with current DBS approaches. Another is the development of so-called "smart" DBS devices. These record a person's unique brain activity and then deliver electrical stimulation only when needed, such as when symptoms return, rather than continuously, as the current systems do. This improvement may help avoid some of the side effects of stimulation (e.g., numbness/tingling, speech problems) and lengthen battery life of the pulse generator, reducing the need for replacement procedures.
In addition, investigators are working to determine if DBS would be effective — work better than medication, improve quality of life, delay development of motor complications — in even earlier stages of Parkinson's. A small trial of people with early-stage Parkinson's demonstrated that DBS was safe and tolerated so now a larger clinical trial of DBS in people who, among other criteria, have been taking medication for four years or less is in the works. All participants will have the DBS system implanted and continue PD medications, but for the first two years only half of the volunteers will have the DBS turned on. For the second two years, all participants will receive DBS plus medications. MJFF is supporting the efforts to complete the planning phases (including a grant proposal to the National Institutes of Health for full funding) so that this pivotal trial can launch. Along with providing financial support, MJFF was able to aid researchers in collecting information regarding individuals' willingness to volunteer for a trial like this using Fox Insight (an online tool that allows people with PD to submit data on their Parkinson's experience).
The recent FDA approval of DBS with Parkinson's disease for four years or more expands the population of people with PD who can potentially benefit from therapy. Ongoing and future research endeavors will hopefully continue to broaden this group and the potential uses of this treatment.
Read more about deep brain stimulation.
Watch a webinar on DBS to learn more about ongoing research in this area and hear one patient's story.
Find studies testing DBS and other therapies on the MJFF clinical research matching tool Fox Trial Finder.
The "Ask the MD" series is supported by Acorda Therapeutics. While our generous sponsors make the "Ask the MD" program possible, their support does not influence MJFF's content or perspective.
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