Neuroscience experts at University of Minnesota Health are improving the care of patients with Parkinson’s disease, essential tremor and dystonia through deep brain stimulation.
Michael C. Park, MD, PHD, with University of Minnesota Health, uses deep brain stimulation to treat patients with neurological conditions.
Deep brain stimulation has become one of the most trusted treatment methods for patients with movement disorders who have not been able to maintain ongoing symptom control through medical management. Worldwide, the procedure has helped more than 100,000 individuals find relief from motor issues that can be disabling.
“Patients are very satisfied with the outcomes of deep brain stimulation; often they develop complete control of their symptoms,” says Michael C. Park, MD, PhD, Assistant Professor of Neurosurgery and Neurology and MnDRIVE Neuromodulation Scholar and Director of Stereotactic and Functional Neurosurgery, Department of Neurosurgery and Neurology, University of Minnesota Medical School. “People with Parkinson’s disease will tell me they used to be embarrassed to eat in public or go to other people’s houses, and that their quality of life improved dramatically when their symptoms became controlled after surgery.”
Working collaboratively and utilizing the specific expertise of Dr. Park, whose rich background in the area of neuromodulation has helped shape the program, the University of Minnesota Health team implants a device that sends electronic signals to the area of the brain that is part of the uncontrolled movement circuitry. Neurosurgeons place an electrode and a generator during separate procedures, aided by the neurologists who diagnose these patients and radiologists who provide high-definition imaging. Once placed, the device, called a neuromodulator, begins intercepting the disabling brain messages that contribute to movement disorders. For the right patient, the results can be life changing.
The Patient Selection Process
University of Minnesota Health patients who undergo evaluation for deep brain stimulation have typically undergone therapy for movement disorders for some time. Many have tried medication combinations at various doses and frequencies but have experienced distressing side effects or have not been able to maintain control of their symptoms because the medication wears off too quickly. Nevertheless, patients who have some response to medication are typically better candidates for deep brain stimulation.
University of Minnesota Health clinic staff
“If primary care physicians or neurologists have patients that they think may be candidates for deep brain stimulation, we can provide a full evaluation that may lead to treatments sooner, which can result in more rapid improvement in quality of life,” Dr. Park says. “We work closely with local physicians, and, once patients go through implantation, are surgically recovered and the device is programmed, we send them back to keep receiving care from their primary doctors. Together, we do what is best for each patient.”
The University of Minnesota Health patient evaluation process is specialized from the beginning. A neurologist who focuses on movement disorders follows the progress of each patient over a period of time, using on-and-off medication testing to monitor the effects these changes have on symptoms. Patients will undergo brain imaging to determine if additional neurological disorders are complicating their condition and to detect any lesions or other anatomical difficulties that could render surgery too great of a risk. A neuropsychological evaluation is also conducted to determine whether the patient is experiencing cognitive dysfunction.
“Patients can typically complete the evaluation process in one or two days, depending on their needs,” Dr. Park says. “For patients who travel great distances, we schedule multiple appointments on a single day, including time with neurologists, psychologists and the imaging team. After we’ve analyzed the clinical information, we work together across disciplines to determine whether the patient is a candidate for deep brain stimulation.”
Two-part Device Implantations
Patients who qualify for deep brain stimulation have the medical devices implanted during separate procedures, one for the electrode and a second for the generator. Surgeons place the electrode in the brain to send the signals to the targeted brain area and implant the generator under the skin, typically against the chest wall, to power the device. The electrode implantation is more complex and takes place first.
Michael C. Park, MD, PhD
The patient is awake during a certain part of the electrode implantation procedure. By keeping the brain fully active, the University of Minnesota Health specialized surgical team, which includes neurologists experienced in brain mapping, locates the ideal destination for the electrode using microelectrode recording (MER). This electrophysiological mapping “confirms the borders of the target nucleus and helps identify sensorimotor territories,” according to a 2015 study in Neurology that concluded intraoperative MER is a “safe and effective” technique for guiding deep brain stimulation device implantation.
“We listen to the brain in and around the target area to get a better idea of what the brain looks like before determining where to place the electrode,” Dr. Park says. “As imaging capabilities and stereotactic targeting improves, some facilities are relying more on image-based implantation of the electrode. While that may save time, we feel it is less exact than MER, which is why we continue to use MER as our standard of care.”
Other imaging techniques are also utilized to plan, carry out and assess the success of the procedure. The neurosurgeons have access to a 3-D brain model on the targeting computer, which they use to plan the procedure. Patients have the option of obtaining brain MRI from a 7 Tesla MRI facility, which is unique to the University of Minnesota. Additionally, when patients arrive at the operating room, the surgical team places a reference frame around the head, takes a CT scan and merges it with the presurgical MRI.
“Once we have all the coordinates, we sedate the patient and begin our surgery,” Dr. Park says. “The procedure requires a small incision and an opening in the skull about the size of a dime, through which we access the brain. Once the opening is created, the anesthetist wakes the patient so brain function can be monitored. The neurologists who are experts in brain mapping are there in the operating room for the mapping portion of the surgery. They guide us to the right location, and we place the electrode in the area and at the depth that will target the signals for motor dysfunction.”
The team then connects the electrode to an external stimulator and tests the effect of the signals. Dr. Park likens the testing to placing a powerful stereo in an apartment. In his analogy, the neighbors should only come knocking when the sound is cranked up, just as side effects should only occur when stimulation occurs at a high power level.
“If you only get to three out of 10 before your neighbor comes around, you know you’re not in a good spot,” Dr. Park explains. “If the electrode is in the right location, when you stimulate someone at the low power setting, the tremor will go away. If it requires high power to generate unexpected side effects, we know we can treat the tremor.”
Once patients have had the electrode placed, they are sedated again, and neurosurgeons repair the scalp and remove the head frame. It takes careful placement and approximately five to six hours to successfully complete the procedures. Most patients go home the next day and return in a week for the generator implantation.
The second surgery requires approximately 90 minutes and is typically performed on an outpatient basis. Neurosurgeons connect a wire from the electrode to an extension wire that is tunneled from the scalp to the generator in the chest.
“Most patients who have symptoms on both sides of the body come in to get the worse side taken care of initially, and after they see the dramatic improvement in their symptoms, they come back to have the procedure again for the other side,” Dr. Park says. “When patients who have had the procedure ask to have it on the other side of their brain, I think that speaks for itself in terms of how effective this treatment is.”
A Pioneer in Deep Brain Stimulation
The success of deep brain stimulation at University of Minnesota Health goes back many years. The treatment initially required destroying the tissue in the target area. Alim Louis Benabid, MD, of France is credited with first using stimulation to eliminate tremors, and tissue preservation has been part of the therapy ever since. With medical device company Medtronic headquartered in Minnesota, University of Minnesota Health physicians were early adopters of this unique therapy.
“While it is never too late to have a patient with Parkinson’s disease or another movement disorder evaluated for deep brain stimulation, sooner is definitely better. So many patients tell me they wish they’d had the treatment sooner. It often provides a significant improvement in their quality of life.”
— Michael C. Park, MD, PhD, Assistant Professor of Neurosurgery and Neurology and MnDRIVE Neuromodulation Scholar and Director of Stereotactic and Functional Neurosurgery, Department of Neurosurgery and Neurology, University of Minnesota Medical School
A long history of providing and pioneering deep brain stimulation has allowed the team to develop its practices and protocols over time, establishing a world-class destination for this therapy. The University of Minnesota Health team has an experimental protocol in place for use of 7 Tesla MRI scans, which allow imaging specialist and researcher Noam Harel, PhD, to outline the target area for stimulation. According to Dr. Park, 7 Tesla MRI has proven extremely accurate, with results that are mirrored and confirmed with MER mapping.
“Our imaging capabilities, surgical facility and broad group of specialists working together make our program special,” Dr. Park says. “Patients are not bouncing back and forth between specialists. When they come to see us, we all work with them from start to finish — the interaction between departments is very important. That’s part of why the surgery takes such a long time; we’re working together throughout the procedure to meticulously map the brain. We’re all there for the patient through the workup, in surgery and during postoperative care.”
The University of Minnesota Health deep brain stimulation team is always looking to the future and working to advance the application and accuracy of the therapy. Neurosurgeons and neurologists collaborate with researchers performing animal research, basic science research and technological research to find better devices, surgical programming techniques and methods of implantation. Dr. Park and his colleagues are monitoring studies that examine the benefits of intermittent stimulation and different delivery methods for deep brain stimulation. In the future, these research programs will likely find a home at University of Minnesota Health, and patients across the region will continue to benefit from this elite program.
For information about referring a patient with a movement disorder to University of Minnesota Health specialists, visit mhealth.org/care/treatments/deep-brain-stimulation-adult or call 612-672-7000.