Episode 72: What is Deep Brain Stimulation?

Dan Keller 0:08

Welcome to this episode of Substantial Matters: Life and Science of Parkinson's. I'm your host, Dan Keller. At the Parkinson's Foundation, we want all people with Parkinson's and their families to get the care and support they need. Better care starts with better research and leads to better lives. In this podcast series, we highlight the fruits of that research—the treatments and techniques that can help you live a better life now, as well as research that can bring a better tomorrow. One of these techniques, Deep Brain Stimulation, or DBS, is a surgical treatment for Parkinson's disease. In DBS, electrodes are placed precisely within certain brain structures and connected to a small implantable pulse generator, or IPG, usually implanted under the skin of the chest. The electrical pulses block abnormal nerve signals that cause Parkinson's motor symptoms. The treatment can provide significant relief for many people with PD, but it is not for everyone. For this podcast, I spoke by phone with neurosurgeon Dr. Nader Pouratian of the University of California, Los Angeles. He told me how well the surgery works really depends on patients' understanding of what benefits it can provide and realistic expectations of outcomes. We talked about who are good candidates for the therapy, how the device works, how the surgery is performed, success rates, and short-term and long-term outcomes, as well as possible complications. He also gave his expert view of developments in DBS to look forward to. To start, he focused on what's available today, comparing DBS to a cardiac pacemaker.

Dr. Nader Pouratian 2:02

As everyone knows, the cardiac pacemaker is intended to help the heart have a more normal rhythm when it is sick or diseased, and when that sickness or disease of the heart causes it to have an abnormal rhythm. And Deep Brain Stimulation is very similar in that it's basically the same technology, but instead of stimulating the heart, it's sending those pulses or that electrical activity deep into the brain, into very specific regions, and it's modulating electrical activity in the brain in order to try and make the brain function more normally and try to treat the symptoms of disease.

Dan Keller 2:42

How's it done? How do you actually do Deep Brain Stimulation?

Dr. Nader Pouratian 2:47

The surgery is a very precise surgery. As the saying goes in real estate, location matters, and so it also matters in the brain. And so the most important, most difficult part of the surgery is making sure that the electrodes—the stimulators that are placed in the brain—are placed in the correct position. Traditionally, that's done with a device that's called a stereotactic device. It's most often a frame, or it's like a box that's fixed to the skull, and that allows us to know exactly where our implant is going inside the brain. We most often do this surgery across most centers with the patient awake so that we can map out the brain activity, know very well where the electrode or the stimulator is going, and then we're able to turn the device on during the surgery to test the patient and their symptoms and make sure that the electrode is providing a therapeutic response—or it's actually improving the patient's symptoms—and also to make sure that there aren't too many side effects. But in more recent times, as medical technology has improved with more advanced imaging, and the ability to have imaging technologies in the operating room, some centers are using that advanced imaging to guide the therapy. So people are able to stay asleep for the surgery at some centers, and the surgeon is confident that they have the electrode in the right place by getting really high-resolution images during the surgery to confirm accurate placement of that electrode.

Dan Keller 4:22

Who are good candidates for Deep Brain Stimulation? I assume this is not the first sort of therapy they would turn to.

Dr. Nader Pouratian 4:29

That's a great question, and it's a question that we deal with most often when we're evaluating patients for this therapy. In fact, most patients with Parkinson's disease are not good candidates for Deep Brain Stimulation. It's really a select number of people who are candidates for this therapy. I think the first and foremost important thing that people need to know is that medical therapy—meaning medications like carbidopa-levodopa, dopamine agonists, and other therapies that neurologists use—are the first-line and mainstay therapies for Parkinson's disease. We only really consider Deep Brain Stimulation for those people whose disease advances and they start developing side effects from their medications. And those side effects can be the extra movements of Parkinson's disease that we call dyskinesias when people have taken their medications, or it might be that the medications wear off too quickly, so that they have what we call motor fluctuations, where they're "on" and moving really well, but then suddenly, within an hour and a half or two hours, they are "off," and people are relying on their medications every couple of hours. The most important thing that we tell people is that this is not a surgery or a therapy for people who feel like their medications just don't work. In fact, it's for people in whom the medications do work, but that those side effects that we're talking about or that they just don't last long enough. And so the counseling we give people is that it's for people who need to spend more time in their best "on" condition—that when the medications work, they're great, they just wish that they worked a bit longer. And those are the people we can help the most. I want to highlight two additional points, which is that Deep Brain Stimulation only really treats the motor symptoms of Parkinson's disease. And as those living with Parkinson's disease know, there are a lot of symptoms beyond just movement. There can be GI issues, or gastrointestinal issues; there can be balance issues, memory issues, cognitive issues—those things don't get better with Deep Brain Stimulation. What we really are treating with Deep Brain Stimulation are the slowness, which we call bradykinesia, rigidity or stiffness, tremor, and dyskinesias, as we talked about. So it's really for those select patients who have problems with those motor symptoms that we choose Deep Brain Stimulation or we recommend this therapy. The other caveat that people should know about is that there's a group of patients who have tremor-dominant Parkinson's disease. That is, that tremor is a major part of their Parkinson's disease, and in some people, the tremor doesn't respond to medications, but it will respond to Deep Brain Stimulation. So that's another subgroup of patients that when they have medication-refractory—meaning when their tremor doesn't respond to medications—we do also consider Deep Brain Stimulation to help them. Again, though, only for those motor symptoms.

Dan Keller 7:35

For people who are a good candidate and have a Deep Brain Stimulator implant, what proportion of those patients actually find optimal or satisfactory improvement?

Dr. Nader Pouratian 7:48

Of those people who we deem to be good candidates based on having a good response to carbidopa-levodopa or Sinemet—and I'll add the extra note that of those people who have reasonable expectations of what they're going to get out of the surgery—I would say the vast majority of people, 90-plus percent of people, will get a benefit from surgery. It's those people who are expecting more than what the surgery can do, or those people who just weren't selected appropriately for the surgery, that experience the greatest disappointment from having undergone the surgery.

Dan Keller 8:27

I know, with hearing aids, it takes some period of getting them tuned up and things like that. Does this need to be adjusted? And when could someone expect to get the best results that they're going to get? How long would that take?

Dr. Nader Pouratian 8:41

So that, too, is a great question, because it's a process. We often joke that once you get implanted with a Deep Brain Stimulator, it's like marrying into our treatment family, because it's both a blessing and a challenge. It's a stimulation in that as soon as you turn the stimulation off, the therapy goes away—meaning, if your battery goes dead, the therapy goes away. But in terms of how soon you get a benefit, most people experience a benefit as soon as the device is turned on. But the brain gets used to the stimulation. It adjusts to the stimulation. And what we find is that if we have people come back about once a month when they're initially getting programmed and their stimulation settings are being updated, usually by about three to four months they achieve a stable response. So just to clarify, that people will get a response the first time we turn them on, and it's not uncommon for them to call us about a week later and say, "We were doing great, but now it's starting to fade. It's not as good as it was." And what will happen is that they'll come back in and we'll turn the device up a little bit, we'll adjust it a little bit, until they get a good response. And this will happen a few times until they get to that steady state where they have a consistent response to the stimulation.

Dan Keller 10:02

Can people get off their medication or reduce it? How does this kind of work with medication or without?

Dr. Nader Pouratian 10:10

We are a very strong advocate of thinking about Deep Brain Stimulation as one of the many treatments and therapies that we use to manage the symptoms of Parkinson's disease. In fact, it's different than other treatments—it's different than the medications that people are used to, because with medications, people are used to just taking a pill. This is, though, just another treatment; it just happens to be a brain surgery. And just as people know that earlier on in their disease, where they might be taking one medication or two medications, or one might be increased while the other is decreased, you can expect the same thing after undergoing Deep Brain Stimulation. Once you have the implant, you can expect that your other medications may be decreased. Now the amount that it gets decreased really depends on multiple factors. It depends on what your symptoms are. It depends on how much medication you needed before the surgery. It also depends on which target the Deep Brain Stimulator is placed in the brain. There's one target called the subthalamic nucleus, where medications generally are reduced more than when we put the electrodes in another target called the globus pallidus. But that comes at a slight expense; there's probably a slightly increased risk of having other side effects with subthalamic nucleus stimulation. So deciding which target to put it in, and deciding whether medication reduction is actually a goal of the surgery, is something that you have to have an individual conversation with your surgeon and your neurologist to figure out what's best for you.

Dan Keller 11:48

What are some potential adverse effects or complications?

Dr. Nader Pouratian 11:53

So we don't have people always lining up at our door to have Deep Brain Stimulation surgery, because it is brain surgery, after all, and it's what we consider an elective surgery. It's not elective like cosmetic surgery, but it's not a surgery that someone absolutely has to have in order to survive. And I think the reason why is because people are afraid of having brain surgery. And what they're afraid of is having brain injury. What that translates into as a surgeon is trying to understand what the risk of bleeding in the brain would be from this type of surgery. We've had many studies in this area, and so we know what the risks are fairly well. The risk of having a permanent deficit—some kind of bleed that would leave you permanently changed from this type of surgery—is about 1%. And to clarify, that means 99% of people do just fine, but that 1% will experience a real deficit. And so it's a risk that people need to be cognizant of, and you need to feel that that risk is justified to undergo the surgery. But while we spend a lot of time dealing with people's concern about bleeding, the bigger risk that most of us recognize in the field of Deep Brain Stimulation is actually the risk of infection. Studies as well as individual theories from particular institutions, even leading institutions, really show that infection rates are somewhere around 3 to 4%. And that's not an infection in the brain; it's not usually a life-threatening infection. It's usually an infection under the skin, but it's a big hassle, and in most cases, management of that infection requires removing the device, treating the infection, and then people can be reimplanted, usually somewhere about two to three months after the original infection is recognized. So those are the two big ones: the risk of bleeding in the brain and the risk of infection. But of course, we talk about other risks. In general, we're putting a device in the body. That device can have failures; it's an electronic circuit. The wires can break, they can get stretched, the battery can run out—all those things are things that we have to anticipate and try and manage proactively. There's also just the general risk of having a major surgery. As easy as the surgery is—you know, it's usually just a one-night stay in the hospital—it's still a major stress on the body. So people who have heart disease are at risk for heart attacks, blood clots in the legs or lungs, pneumonia, urinary tract infection—all these things that can go wrong with a major surgery. It's one of the big reasons why we try and get people up and walking and out of the hospital as soon as possible, so that they are not sedentary and they have a decreased risk for developing those other medical complications.

Dan Keller 14:32

If someone does have a successful implant and it's working well, what are the long-term prospects? Number one, does it slow progression of Parkinson's disease? And also, do the electrodes ever need to be replaced—being in kind of a salty environment, do they corrode? Do they need replacement at any point?

Dr. Nader Pouratian 14:54

So two important questions. One is: does this actually change the disease? Unfortunately, not. There are some people and investigators who are interested in trying to understand whether Deep Brain Stimulation actually changes the disease. There's one decent study out of Vanderbilt University that suggests that it slows down the progression of tremor in patients who undergo Deep Brain Stimulation. But in general, most people would say that Deep Brain Stimulation is not a disease-modifying therapy, meaning it doesn't change the progression of disease. It's merely a symptomatic treatment. As soon as you turn the device off, you will be the way you would have been without the therapy, whether or not you had the implant done, which means the disease will progress as Parkinson's disease will do. So 10 years after implant: is someone better with the implant on than with the implant off? Yes. But are they as good as they were when they were first implanted? No. The disease will have progressed. In terms of the longevity of the electrodes and the device, the electrodes in the brain are tested over and over again with respect to corrosion and the environment in the body. So they usually do not have any kind of rusting or any other problems that you might think of from a salty environment. But they are electrical wires, and the wires can break or they can short circuit. It's not common, but it can happen. In those rare cases, the electrodes might need to be replaced in the brain, but that's not a very common thing to have happen. The more common event is that the battery pack or the generator that's placed in the chest does run out of power at some point, or it starts lowering in power. Hopefully we replace it before it runs out of power. And that could be anywhere from every couple of years to every five years, depending on various parameters. So that is the most likely thing that needs to be replaced over time.

Dan Keller 17:00

There's also a model of Deep Brain Stimulation, I think, that can get recharged. People wear sort of a shawl around them that recharges it. Is that right?

Dr. Nader Pouratian 17:10

Yes. So over the last few years, rechargeable devices have been introduced, and that technology is getting better and better with time. Some of the original recharging devices required a fair amount of time to recharge the device and relatively frequent recharging. Now there are systems that are much more efficient at recharging and do not require recharging quite as often, so they're becoming more viable options. But even those rechargeable devices need to be replaced, probably at least every 15 years, so it does save you several battery replacements. It's just a philosophical question of whether we want someone to have to recharge or, as I often say, I like these non-rechargeable devices because I want to be able to have the patient turn it on and live their life and not worry about the fact that they've got a Deep Brain Stimulator on and having to manage or remember to charge it. But you know, as the recharging technology gets better, I think a lot of our opinions are changing about that, and we're becoming more amenable to these rechargeable devices.

Dan Keller 18:15

Besides doing neurosurgery, you're a researcher, I take it. What do you see coming along, either in Deep Brain Stimulation or any other restorative neurosurgical techniques or technologies for people with Parkinson's?

Dr. Nader Pouratian 18:30

I think there are a couple innovations that are coming up that may impact the field. One is actually here and now and available, but we just don't completely understand how valuable it is—although theoretically we know that it's valuable—and that's this idea of an advance in Deep Brain Stimulation technology, which is the use of directional or segmented leads. So for a couple decades, we've been using leads or contacts that go in the brain that are a full circle around the wire. And recently, a couple companies have come out with devices that actually have a bit more resolution and allow us to shoot electricity in one direction or another inside the brain. And we think the advantage of this will be that we're able to target the electricity in the right direction and shoot it away from the parts of the brain that might cause side effects, and that may improve the efficiency of the system. It may improve how effective the therapy is. But the studies are still being done to truly understand whether our conceptual framework of how good this is is actually going to pan out. For sure, it's not worse, and so in general, for most targets that we use in the brain, we think that placing these segmented or directional leads offer an advantage beyond that. I think there's a lot of work being done, including work in my own laboratory, trying to understand exactly how Parkinson's disease affects the brain. For example, during the surgeries that we do, we often will take a few minutes to listen to the brain, to listen to the patterns of neural activity, or brain activity, and understand how that relates to the severity of symptoms in Parkinson's disease. And why that's important is that if we can try and understand that, then we can start designing devices that we call smart devices—or in more technical terms, a "closed-loop" device. So these devices would be able to listen to the brain and decide when the brain was more symptomatic and adjust its therapy based on how sick or how symptomatic it determined that the brain was. So instead of having a constant level of stimulation throughout the day, it can respond to the brain depending on the situation it's in, depending on how much medication the patient has taken, and deliver a more dynamic therapy than we currently have available. And I think that's probably not that far away from happening. The other things that are exciting that go beyond Deep Brain Stimulation: there is a lot of interest in gene therapy trials to try and reverse some of the abnormal activity in the brain. As I said, we're listening to the brain, you know—can we deliver a gene therapy to make those patterns of activity, those what we call oscillations, more normal? But that's much more early phase; it's not something that I would hold my breath to see the results of. It's going to take several years before we see any results from that in the surgical domain.

Dan Keller 21:48

If I'm interpreting what you're saying right, it sounds like not only would the devices be delivering stimulation, but they'd also be monitoring brain activity and adjusting as needed—sort of machine learning of what's happening at each time of day.

Dr. Nader Pouratian 22:04

That would be the ideal, yes. That's what we're targeting for. So again, to put it in terms that people might understand a little bit better, think about an insulin pump, where an insulin pump might monitor the sugar levels in the blood, or the glucose levels in the blood, and deliver a certain amount of insulin depending on how much is determined that the body needs. And so it's what we call a closed-loop system. The same thing in the brain: we want a closed-loop system that listens to the brain, figures out what's going on and says, "Oh, I better adjust what I'm doing and deliver more stimulation or less stimulation," depending on the moment-to-moment needs of the brain. So it becomes a smart system that adjusts in response to the real-time needs of patients and their symptoms.

Dan Keller 22:46

On the topics we've been discussing, have we missed anything important, or is there anything interesting to add?

Dr. Nader Pouratian 22:53

I always like to make a plug for the value of research and innovation. The whole field of Deep Brain Stimulation has been very lucky that the founders of our contemporary field, or therapeutic field, of Deep Brain Stimulation happened to have found the right targets in the brain to make this therapy work. But you know, when I started my career, people would ask me, "How does Deep Brain Stimulation work?" and I would just have to say, "I don't really know." And over the past 10 years, we've made huge strides in our understanding. And the reason why is because we've had the great generosity of patients who undergo surgery, who let us do that special kind of listening to their brain and testing during surgery so that we can understand how Parkinson's disease affects the brain. And almost as important as the fact that it's helped us understand Parkinson's disease better and develop new ways of delivering therapy and leading to these closed-loop therapies, it has really opened doors to trying to treat other diseases as well, as we try and develop Deep Brain Stimulation for diagnoses like chronic pain and depression. And so I guess I would just take this opportunity to say thank you to everyone who does participate in this type of research and encourage other people who might consider undergoing Deep Brain Stimulation to also consider participating in this type of research, because it really is impactful and makes a difference, not for that person individually, but for the greater good.

Dan Keller 24:35

Great. I appreciate it. Thank you.

Dan Keller 24:45

To find out more about Deep Brain Stimulation, visit our PD library at parkinson.org/library and search "Deep Brain Stimulation" or just "DBS." You'll find articles explaining what to expect if you are contemplating DBS, who are good candidates for the procedure, and inspiring stories from people who have DBS. Our National Medical Director, Dr. Michael Okun, has authored several articles on the website discussing what DBS is, how it works, and even what family members need to know about it. Here you'll also find a digital copy of the free resource book, Surgical Options: A Treatment Guide to Parkinson's. You can download or request a free copy in print, either online or through the helpline. You can also visit dbs.ucla.edu to view a video featuring Dr. Pouratian as he explains the DBS procedure and shows how it can help. As always, our PD Information Specialists can answer questions and provide information in English or Spanish about this topic or anything else having to do with Parkinson's. You can reach them at 1-800-4PD-INFO. If you have questions or want to leave feedback on this podcast or any other subject, you can do it at parkinson.org/feedback. If you enjoyed this podcast, be sure to subscribe and rate and review the series on Apple Podcasts or wherever you get your podcasts. At the Parkinson's Foundation, our mission is to help every person diagnosed with Parkinson's live the best possible life. Today, to that end, we'll be bringing you a new episode in this podcast series every other week. Until then, for more information and resources, visit parkinson.org or call our toll-free helpline at 1-800-4PD-INFO, that's 1-800-473-4636. Thank you for listening.

Dr. Nader Pouratian is Professor and Vice-Chair of Academic Affairs in the UCLA Department of Neurosurgery. He is the Chief of Functional Neurosurgery and director of the Neurosurgical Movement Disorders Program. He also serves on the Executive Committee of the Congress of Neurological Surgeons and the American Society of Stereotactic and Functional Neurosurgery. At UCLA, he works with a multidisciplinary team of neurologists, neurosurgeons, psychologists and other experts to provide the best care for each patient, be it medical or surgical. His research aims to use advanced brain mapping techniques to develop, improve, and optimize surgical treatments for neurological and psychiatric diseases. His research spans developing therapies for Parkinson disease, essential tremor, disorders of consciousness, chronic pain, and blindness. He leads and is involved in a number of clinical trials, is the principal investigator for 6 grants from the National Institutes of Health, and works collaboratively with other neurosurgeons, neurologists, and industry to advance the field. He has published over 150 original scientific reports. He is internationally recognized, speaking around the world on advancing the care of patients that can benefit from neurosurgical procedures. But most of all, he is dedicated to delivering the best possible care to each patient.