In the United States, approximately 1 million Americans live with Parkinson’s disease. Although there’s no cure to reverse its effects, there are ways to reduce symptoms such as the tremors, rigidity and bradykinesia.
At UNC Medical Center, a multidisciplinary team of neurologists, neurosurgeons, psychiatrists and social workers are treating these symptoms—and other neural conditions with similar symptoms—through deep brain stimulation (DBS).
“The basic idea is that in certain disease states, like Parkinson’s disease, there is a discrete overactive neural circuit that mediates many symptoms of the disease,” says neurologist Richard Murrow, MD, director of the Deep Brain Stimulation Clinic at UNC Medical Center and the author of a paper about the mechanism of deep brain stimulation.
“If we can disrupt that specific, discrete circuit by a carefully placed electrode and deliver high-frequency electrical stimulation, we can block the symptoms of the disease that were previously being mediated through that circuit.”
Dr. Murrow says deep brain stimulation has been dramatically successful in treating these symptoms if the electrodes are perfectly placed and programmed.
“As you can imagine, the brain is dense in neural circuits, so getting the electrode in exactly the right position with submillimetric accuracy is critical,” he says. “If the electrode is well-placed, it can produce really striking results.” For patients with Parkinson’s, that means electrodes are placed at the subthalamic nucleus.
Other Uses for Deep Brain Stimulation
Although Parkinson’s disease is the most common indication for DBS therapy, other neural conditions can also be treated. The common element is a discrete neural circuit that’s pathologically overactive, Dr. Murrow says. Depending on the condition, the location of electrode placement differs.
For example, patients with obsessive-compulsive disorder who are treatment-refractory (have not responded to medications or cognitive behavioral therapy) also benefit from DBS. Robert McClure, MD, associate professor in the UNC Department of Psychiatry, works with Dr. Murrow and the rest of the UNC team to determine which patients with OCD are good candidates for DBS. After surgery, Dr. McClure programs the device to maximize improvement.
“With regular follow-up, we have had very good results, with up to 50 percent of patients reporting a significant reduction in the severity of their obsessions and compulsions,” Dr. McClure says.
The Best Candidates for Deep Brain Stimulation
While DBS can have significant benefits, managing symptoms without surgery is ideal. Many patients with early Parkinson’s disease manage their symptoms effectively with medication and don’t need DBS. And patients with dementia are also not recommended for the procedure. “If you have a patient with dementia, you wouldn’t want to subject that patient to a craniotomy for fear of exacerbating the dementia,” Dr. Murrow says.
“It’s really only appropriate for those patients in between who are having symptoms that are not adequately controlled with medication but who are not developing any significant cognitive impairment,” he says. “In those patients, it really can be quite effective.”
Parkinson’s is a progressive disease; patients will experience increased severity of symptoms and will need more medication to manage them. Initially, physicians might be able to increase their dosage, but eventually patients might run into adverse effects that can be disabling, Dr. Murrow says. These complications include:
- Severe vomiting
- Severe lightheadedness
- Visual distortions, which can develop into full-blown visual hallucinations
“Many patients require so much medicine they have dyskinesia quite a bit of the time, but often they prefer the dyskinesia to how they feel if they don’t take their medicine, because off their medicine they can’t move,” Dr. Murrow says.
After DBS, the amount of medication required to treat Parkinson’s is dramatically reduced.
“We’ve had a couple dozen patients that we’ve been able to completely get off anti-Parkinson’s medicine after deep brain stimulation,” Dr. Murrow says. “On average, we counsel patients that they’ll usually require a third of the medication they were requiring before DBS after successful deep brain stimulation.”
Patients with advanced Parkinson’s disease might also experience the “on-off phenomenon,” in which medication works well at first but wears off before the next dose. These fluctuations can be problematic as patients switch between mobility and immobility. A patient like that could be a great candidate for DBS, Dr. Murrow says.
“With deep brain stimulation, there is a constant electrical stimulation so the effect is continuous and equal, so you don’t have that fluctuating response.”
The Risks of Deep Brain Stimulation
Because DBS requires implanting a foreign object in the body, there is a risk of infection that would require additional surgery. “If a foreign object gets infected, you can’t just take an antibiotic to get rid of the infection. You have to take the hardware out and replace it later,” Dr. Murrow says.
Brain injury, such as bleeding in the brain, is also a concern. “The good news is that the chance of hemorrhage is very small: less than 1 percent,” he says.
It’s important for patients to understand that DBS therapy treats only the symptoms that were previously mediated through that specific neural circuit—not the disease as a whole.
“Patients with DBS therapy can develop progressive hypophonia. DBS therapy doesn’t help that,” Dr. Murrow says. “Even patients who have successful DBS still may go on to develop a speech impairment.”
DBS also has no effect on postural instability and cognitive impairment, which are other symptoms of Parkinson’s.
Learn more about deep brain stimulation therapy at the Movement Disorders Center at UNC Medical Center, or call (919) 966-5549 to schedule an appointment for your patient.