Deep brain stimulation holds promise for a growing number of neurologic disorders

April 12, 2018 Swedish Blogger


Key Points:

  • Deep brain stimulation, or DBS, is a therapy that offers relief from various movement disorders such as Parkinson’s disease, essential tremor and dystonia.
  • Recent studies suggest DBS may help with symptoms associated with Alzheimer’s disease, Tourette’s syndrome, and obsessive-compulsive disorder.
  • Potential DBS candidates must first obtain an accurate diagnosis. 

The human brain is often considered one of the last real medical mysteries or frontiers to be explored. Although by weight our brain only accounts for about 2 percent of our total body weight, as the “command center” of our nervous system, the brain controls nearly all of the activities of the body, and typically contains up to 100 billion nerve cells (neurons).  Medical science has invested heavily in researching the brain, and one promising area that has garnered well-deserved attention is the increasing success of a medical procedure known as deep brain stimulation or DBS.

What is DBS?

DBS is a way to modulate parts of the brain that cause disabling conditions such as Parkinson's disease without damaging the brain. Electrodes are placed within certain regions of the brain known to control movement, such as in the thalamus (to treat essential tremor and other forms of tremor) or in the globus pallidus (for Parkinson's disease and dystonia). These electrodes are then connected by small wires to a battery-powered device called an impulse generator, which is surgically implanted under the skin of the chest wall, just below the collarbone. When activated, the impulse generator sends electrical pulses to the target areas in the brain, blocking the brain’s own impulses that cause tremors or other involuntary movement symptoms. 

The expanding applications of DBS

Ryder Gwinn, MD, a neurosurgeon at the Swedish Neuroscience Institute, explains that DBS was initially designed to help those suffering from Essential Tremor and Parkinson’s disease, but has since been found to help people with other movement disorders such as Tourette’s syndrome, and dystonia. “In the conversations about how DBS can or should be used, it’s important to distinguish between what is and is not an FDA-approved condition for DBS. The approved indications for DBS are Parkinson’s disease and essential tremor, but there is actually an area referred to as the humanitarian device exemption, or HDE, that helps facilitate the procedure in cases where the FDA won’t approve DBS because there is not yet a large well-controlled study to show its efficacies. Because the FDA feels there is such a small population with these other, non-FDA approved conditions, it at times gives its stamp of approval via an institutional review board that allows an individual hospital to perform the DBS procedure under the HDE exemption.”

Rewiring the brain with DBS

Put simply, the brain is composed of three main parts-- the cerebrum, cerebellum, and brainstem. Within these key sections, there is a left and right hemisphere, gray matter, white matter, connecting fibers, and those 100 billion neurons. One of the benefits of studies in brain mapping and DBS includes a newfound ability to explore and manipulate different regions and parts of the brain.

Dr. Gwinn says, “The use and success of DBS, particularly with essential tremor and Parkinson’s disease, has really helped us understand the brain and given us the capability to interact with individual circuits within the brain, and change the function of those circuits. Our ability to do this with DBS is really a revolutionary idea to help treat brain disorders. Before DBS, treatment involved creating lesions in areas of the brain, which permanently destroys these areas, and then assessing what happened to the brain function afterwards. There is a certain amount of risk associated with that, and we don’t necessarily learn much about the networks when we destroy certain parts of the brain. With DBS, we can either essentially shut down certain networks of the brain or actually activate individual nodes within brain’s network to see how that changes. Plus, with DBS we now have the ability to make literally thousands of adjustments to the impulses sent to the brain.”

It is now possible to safely implant the DBS electrodes virtually anywhere in the brain. “It’s really a very exciting time to be in this field,” says Dr. Gwinn, “because we have a tool which enables us to interact with individual networks and nodes within those networks that we think contribute to many of the chronic neurologic problems we see in conditions like Alzheimer’s, depression, obsessive-compulsive disorder, Parkinson’s or dystonia.” 

What to consider when reading popular accounts of DBS studies

In view of the successes achieved with DBS, research in the field is expanding. Popular news stories about DBS studies may focus on optimistic conclusions but can overlook important aspects of DBS that need to be considered. Dr. Gwinn says there are definitely certain characteristics he looks for in these studies. “The first thing I look for is FDA approval, which is not really a study but more of a governmental permission. Since the FDA has only approved DBS for Parkinson’s and essential tremors, you really have to look closely at studies in order to justify using DBS in other areas. When we don’t have government approval, we have to look at these individual studies to help guide our decision-making process. Unfortunately, a lot of these newer indications for deep brain stimulation don’t have any studies that look at DBS in a comprehensive way. What I look for mostly are well designed, larger studies that have been controlled in some way. In general, I look for studies that have at least 50 patients enrolled in the study in order to have a good level of trust that the outcome is actually real. I then look for a controlled arm of the study, which means the study was consistent in delivering the same therapy to the patient groups and accurately interpreted the validity of it. The best studies are those we call ‘blinded’ studies, when both the attending physicians and the patients are unaware, by design, as to whether the patient is getting the therapy or a placebo.”

Are you a candidate?

Dr. Gwinn emphasizes that greater awareness of DBS is needed to increase utilization for people who can benefit from it. “It’s estimated that only 10 to 15 percent of people with severe refractory Parkinson’s disease who would benefit from DBS actually ever get referred for evaluation and surgical treatment. The percentages are similar for people living with essential tremor.”

If you suffer from a condition that may be improved by DBS, the crucial first step is diagnosis. “For whatever condition we’re talking about, whether it’s essential tremor, Parkinson’s, dystonia, or one of these newer indications, the most important consideration is to have a specialist make an accurate diagnosis,” says Dr. Gwinn. “This may sound simple and straightforward, but many of these conditions have overlap with other conditions, so there can be other medical issues that cloud our ability to help treat the primary issue.”

Seeing the right specialist is absolutely essential. People with a movement disorder should consult a neurologist for a thorough patient evaluation. Next, be sure you have received adequate medical or non-interventional treatment for your condition. Dr. Gwinn says, “For many conditions, such as Parkinson’s, there are several medications that can help alleviate the symptoms for extended periods of time. We don’t want to perform invasive surgery on a patient who would benefit greatly just by taking medication.”

Additionally, you should align with a well-qualified neurologist and a medical team that specializes in DBS because there will be a need for ongoing monitoring and there are a multitude of adjustments that may need to be made on an ongoing basis to ensure the best outcome. For example, between the various pulse widths, frequencies, amplitudes and voltage settings, there are literally thousands of possible parameter combinations that can be programmed for the patient. So, it’s vital to make sure you have access to excellent continuity of care with a specialized team that has a solid track record of success in DBS. 

Looking to the future

Thanks in part to ongoing research, new applications for DBS are appearing on the horizon, offering hope to many who suffer from involuntary movement disorders and even certain forms of depression. Dr. Gwinn says, “Right now I think there are several conditions that would respond well to deep brain stimulation, such as epilepsy. Although it is not yet approved by the FDA here in the U.S., it is approved for use in Europe. One of the newly emerging areas that I’m excited about is in the area of memory impairment. There are some initial indications that stimulating a part of the brain called the medial temporal lobe can help to improve memory performance. There are not yet a lot of well-controlled studies on this DBS application, but there is significant interest in this area for those who have traumatic brain injury with memory disorder, or for those with Alzheimer’s who may benefit from DBS.”

Patients come first at Swedish Neuroscience Institute

Swedish practices a multi-disciplinary, patient-centered approach in treating neurological conditions. For example, says Dr. Gwinn, “We have a comprehensive epilepsy center that includes teams of neuropsychologists, epileptologists, neurosurgeons, and neuroradiologists. The same is true for essential tremor or Parkinson’s disease where we have a team approach with movement disorder neurologists and other specialists. I truly believe that a group consensus with specialized expertise is the ideal way to get the best outcome for a patient. At Swedish Neuroscience Institute, we’ve been doing deep brain stimulation for over 14 years and we’ve established a great track record for people living with essential tremor, Parkinson’s disease, epilepsy, and dystonia. We also have a fellowship program where we train graduates of neurosurgery programs specifically in this area so they can become experts in the field. And we have highly skilled staff who are well-experienced in the programming intricacies of DBS to keep patients at the very top levels of their performance.”

Neurosurgery became Dr. Gwinn’s path when he saw that neurosurgeons are the only people who have the privilege of physically interacting with the brain on a regular basis. In that light, Dr. Gwinn finds great professional satisfaction in seeing the positive results of DBS. “It’s an honor to be able to see the change for the better in patients who undergo the DBS procedure. During surgery, we can see first-hand the improvements when we place and activate these deep brain stimulating electrodes. In fact, oftentimes when we have a patient with essential tremor, the patient is awake in the operating room. We’ll implant the electrodes, turn it on, and the tremors stop right there. It is a dramatic experience to see the patient’s worst problem just melt away right there in the operating room.”

Swedish neurologists and neurosurgeons stand on the leading edge of clinical care and clinical research for diseases of the nervous system. Learn more about the Swedish Neuroscience Institute.

Also recommended for you:
Deep Brain Stimulation for Dystonia
The Benefits of DBS and Neuromodulation: Helping Patients

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