Presented by: Melanie Lising, MD
Clinical Assistant Professor, Neurology and Neurological Sciences
Laurice Yang, MD
Clinical Assistant Professor, Neurology and Neurological Sciences
March 10, 2016
Deep brain stimulation has been used as a treatment for Parkinson’s disease for the last 25 years. Yet this modern medical therapy has roots in remedies used in first-century A.D. Rome.
In 46 A.D., a physician for the Roman emperor discovered that when people touched an electric ray, they would get intermittent relief from pain. “The physician would then put electric rays on patient’s heads and that’s how he treated headaches,” said Laurice Yang, MD, at a presentation for the Stanford Health Library on the past, present, and future of deep brain stimulation. “We have come a long way since then.”
“Centuries of efforts to build on that discovery have led to the modern medical treatment of deep brain stimulation for Parkinson’s disease,” said Dr. Yang, a clinical assistant professor of neurology and neurological sciences at Stanford University Medical Center. Parkinson’s disease is a neurological disorder that causes tremors and movement disorders including slowness, rigidity, and unstable or stooped posture.
Before deep brain stimulation could be developed, physicians had to pinpoint how electricity could be used as medical therapy. Animal studies in the 1800s showed that electrifying specific areas of the brain would trigger muscle twitches. By the 1950s, Dr. Wilder Penfield, a neurosurgeon, developed a map of the brain showing which areas of the brain were linked to which part of the body. “This map of the brain is still used today,” said Dr. Yang.
Perhaps the most dramatic example of how the brain can be stimulated by electricity to control motor movement came from the experiments of Dr. Jose Delgado, a Spanish neuroscientist. In 1952, he implanted electrodes into the brain of a bull that could be activated by external remote control. Once the bull was released into a bullfighting ring, “He could drive a certain electrical impulse via a remote control into the bull’s brain and could interrupt and even stop the charging bull in its tracks,” Dr. Yang said.
Over the next few decades, physicians began implanting electrodes into the brains of Parkinson’s patients to “ablate,” or destroy, small amounts of tissue in a way that stopped the tremors, a hallmark symptom of Parkinson’s disease. When doctors realized patients were developing other problems with speech, swallowing, and cognition, they developed newer methods that would aim to rebalance dysfunctional electrical activity in the brain tissue rather than destroying it.
“That evolution has brought the practice of deep brain stimulation to the forefront as a therapy for Parkinson’s disease,” said Melanie Lising, MD, a clinical assistant professor of neurology and neurological sciences at Stanford. Parkinson’s affects 1 million people in the United States and 5 million people worldwide. Its prevalence increases with age, affecting 1 percent of those over age 60 and 4 percent of those over age 80.
Drugs like levodopa are usually prescribed for treating Parkinson’s disease. Many patients find their symptoms improve with levodopa or similar prescription drugs. “Eventually, however, their effectiveness may wear off,” Dr. Lising said. Even with levodopa, patients may eventually experience the return of their bradykinesia, tremor, and rigidity—or develop a side effect of the levodopa such as frequent involuntary movements called dyskinesias.
“When they find themselves taking frequent higher doses without consistent help, that’s the time to consider getting deep brain stimulation,” Dr. Lising said. To date, about 100,000 people worldwide have had deep brain stimulation. The procedure has been approved by the FDA.
“It’s not a cure for Parkinson’s disease,” Dr. Lising said. It won’t stop the progression of the disease. “But it will improve the motor symptoms of Parkinson’s and quality of life” she said.
It’s important that Parkinson’s patients not wait too long to get deep brain stimulation once their medicine becomes less effective, Dr. Lising said. “If you wait too long, there is a time when that window will close and deep brain stimulation will not be an option.”
“Deep brain stimulation doesn’t help every Parkinson’s patient,” Dr. Lising said. Studies have found it works best in patients who have previously been helped by levodopa, but who have developed motor fluctuations or dyskinesia. Deep brain stimulation doesn’t work as well in patients who haven’t been helped by levodopa.
To deliver deep brain stimulation, surgery is done to implant small electrodes in the brain that send electrical signals to specific areas that control movement. The currents block excessive brain activity that otherwise causes disabling movement problems. Once implanted, the electrodes can be adjusted in voltage, pulse and rate of frequency so it’s tailored to each individual’s needs. In addition to the brain electrodes, a battery-operated device called a neurostimulator that delivers electrical signals to the brain is implanted in the chest.
“It is basically like a pacemaker for the brain,” Dr. Lising said.
Deep brain stimulation can ease the tremors, rigidity, slowness, and shuffling that come from Parkinson’s. It doesn’t help problems with non-motor symptoms such as constipation. It’s also more difficult to treat “midline symptoms” affecting speech or swallowing, balance, or the freezing of gait, a phenomena where patients may “feel like their feet are stuck to the ground,” Dr. Lising said.
The surgery to implant deep brain stimulation also has some risks. The rate of infection is about 3 to 4 percent, though it can be higher for those with diabetes, old age, or those taking steroids. The risk of hemorrhage is about 1 to 2 percent, and those with cognitive impairment are at higher risk of postoperative delirium.
Patients must undergo medical evaluation before surgery for deep brain stimulation to make sure they have the kinds of problems that will be helped. After the comprehensive evaluation that involves meeting with the neurologist, neuropsychologist, and neurosurgeon, the case is discussed at a multidisciplinary review board for approval, so the entire process can take weeks to months, Dr. Lising said.
But the long evaluation can be worth it because studies show the benefits of deep brain stimulation continue to last. “One study found 42 percent of Parkinson’s patients were still getting help from deep brain stimulation 9 years after they started,” Dr. Lising said, and the studies are continuing to follow these patients for even longer periods now.
“Researchers are working on improvements for deep brain stimulation,” Dr. Yang said. In the future, smaller size batteries will be available that some people hope may last up to 25 years, rather than the current 3 to 5 years.
Other future developments in deep brain stimulation may include the potential to program the device wirelessly and the ability for the brain-stimulation unit to autonomously program itself in a closed loop fashion.
“It is also very exciting to see that the use of deep brain stimulation is now being used in other fields of medicine,” Dr. Yang said. “Neuroscientists are exploring the potential for deep brain stimulation to treat chronic pain, epilepsy, depression and obsessive-compulsive disorders.”
Furthermore, researchers are also discovering ways to use what we know about brain function and applying it to clinical practice. Scientists are now using sensors implanted in the brain of people who have lost limbs. These sensors are then connected to an artificial limb and patients are now able to move these robotic limbs “simply by thinking,” said Dr. Yang.
For people who want to consider surgery for deep brain stimulation, Stanford University Medical Center holds monthly informational sessions to answer questions. Those interested can contact Carlos Rodriguez at (650) 736-0514.
“The decision to do deep brain stimulation or not is very much a family decision,” Dr. Yang said. “This affects everyone.”
About the Speakers
Dr. Melanie Lising received her medical degree from Chicago Medical School. She completed a residency in neurology at the University of Southern California (USC). She also completed a clinical fellowship in movement disorders at UCSF and the SF VA medical center. She is board-certified in neurology by the American Board of Psychiatry and Neurology.
Dr. Laurice Yang received her medical degree from the University of Vermont College of Medicine and completed a Masters in Health Administration and a residency in neurology at the University of Southern California (USC). She completed fellowship training in movement disorders at the University of Los Angeles (UCLA). She is board-certified in neurology by the American Board of Psychiatry and Neurology.
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