Deep brain stimulation (DBS) can have a life-changing impact on patients with Parkinson’s disease — but not every patient. Parkinson’s is a diverse disease, and patients experience symptoms and respond to treatments in individual ways. For providers, recommending DBS is a question of which patients are likely to benefit and when is the best time to intervene.
“Every patient with Parkinson’s is different,” said Ryan Brennan, DO, neurologist, movement disorders specialist and Medical College of Wisconsin faculty member. “We start with understanding what the goals of therapy are prior to surgery and do a lot of counseling on what’s realistic to achieve and what’s not.” To make care as safe as possible, the team offers patients telehealth visit options when appropriate and provides reassurance about the safety measures in place for in-person care visits.
Levodopa Is First-Line Treatment
The origin of Parkinson’s remains unknown. A progressive disease, it results from loss of dopamine-producing neurons in the substantia nigra, which causes dysfunction in motor control. “It leads to a host of symptoms, including tremors, rigidity and bradykinesia,” Dr. Brennan said. Bradykinesia is slowness of movement, freezing, difficulty initiating movement and loss of facial expressions.
The most potent treatment to relieve the symptoms of Parkinson’s is levodopa. “Once it gets to the brain, it is transformed into dopamine and significantly reduces the symptoms,” Dr. Brennan said. “As the disease progresses, however, the brain reacts differently to the medication and may require more, and patients get off-and-on times where they notice significant fluctuations in their motor symptoms.”
Long-term use of levodopa can produce something of a catch-22 scenario, a side effect called levodopa-induced dyskinesia that causes involuntary, uncontrollable movements other than the typical tremors of Parkinson’s itself.
Making the DBS Determination
When patients get to that stage, typically in the eight- to 12-year range, Dr. Brennan recommends considering DBS. “If they’re having these up and down times, as well as the extra-abnormal movements, DBS allows us to treat the tremors and also the bradykinesia,” he said. “In addition, it allows us to reduce medication, reduce dyskinesias, smooth out those ups and downs and increase more of the up times.”
Prior to surgery, Dr. Brennan performs a thorough assessment to ensure patients are appropriate candidates for DBS. It includes a “challenge test of medication,” an examination on and off levodopa, since a positive response to the medication is known to predict DBS success. The assessment also involves a neuropsychological evaluation for significant mood disorders or other psychiatric conditions. They may not preclude DBS, but should be addressed and well-controlled before the procedure. Patients are also assessed for dementia, as DBS would no longer be an option.
“Once we have all that data, the team meets and reviews cases on an individual basis,” Dr. Brennan said. “What are the patient’s goals, are they realistic, are they likely to receive benefits that exceed the risks of the procedure? If indications are favorable and the patient decides to pursue placement, we then refer to neurosurgery.”
Mapping the Destination
The surgical team uses sophisticated computer brain-mapping technology to plan the procedure with an MRI of the brain. On the day of the surgery, a stereotactic frame is placed around the patient’s head and a CT scan is done. The CT and MRI scans are then merged to determine the three-dimensional coordinates for placing the DBS electrodes.
With the patient lightly sedated and under local anesthesia, the neurosurgeon drills small burr holes in the skull and initially advances the device deep into the areas of the brain where neurons are misfiring. At that point, Dr. Brennan joins the surgery.
“We do microelectrode recording with small electrodes at our preplanned coordinates, listening for neurophysiological signals in the brain,” he said. “It’s a second step at verifying the exact spot more precisely. Once we find that, then we place the actual DBS electrodes.”
The patient is conscious at that point, and Dr. Brennan temporarily turns on the electrodes to test for side effects and to make sure the electrodes are producing benefits. He often sees patients’ symptoms resolve before his eyes — one moment their hands are shaking, and the next, their tremors are gone. If all is well, the neurosurgeon secures the electrodes and closes the opening in the skull with a plastic cap.
DBS requires electrodes on both sides of the brain. Depending on the patient, the procedures may be performed at the same time or a month later. A week after both electrodes are in place, the patient returns for surgery to implant in the upper chest the battery-powered neurotransmitter that will send corrective pulses to the brain and connect it to the electrodes with wires guided under the scalp and the skin of the neck.
Turning the Switch
About three weeks later, Dr. Brennan turns the device on and does the initial programming during an office visit. “We start with smaller settings, gradually increasing them while adjusting medication,” he said. “All in all, the programming and medication process can take six months to a year.”
Today’s advanced DBS technology gives providers more options than ever. “We can change the location of the electrical current, its size, the density of the current or the frequency,” Dr. Brennan said. “Since the electrodes within the brain have four different contact areas, we can choose a combination of contacts or one.”
Calibrations are software-based and done on a tablet that links with the neurotransmitter. Patients get their own programmer on which they can turn the device on and off and use it to make small changes on their own, which is especially convenient if they don’t live nearby. “We may make a smaller adjustment in the clinic and ask them to make another change in two to three weeks,” Dr. Brennan said. “This gives them the ability to do that on their own without having to come to see me.”
New competition from manufactures also enables providers to choose from different devices to maximize therapy. “We’re at the forefront of that and of integrating new technologies and innovations with patient care,” Dr. Brennan said.
With DBS, patients can expect to experience a reduction of tremors, particularly if they were not alleviated by medication, a reduction in rigidity and bradykinesia, improvement in their movement ability and reduced need for medication. “With reduced medication, they’ll have less levodopa-induced dyskinesia, fewer ups and downs, and more time when the Parkinson’s symptoms are better controlled and they can function more normally,” Dr. Brennan said. “For the vast majority, the improvement in quality of life is huge.”
Before the Window Closes
DBS is not a cure for Parkinson’s, so patients need to act in time. “There is a window of opportunity for idiopathic Parkinson’s disease, and once it closes, DBS won’t help,” Dr. Brennan said.
Determining if DBS is right for patients is equally important. “This isn’t for everybody with Parkinson’s,” Dr. Brennan said. “They need to have symptoms significant enough to warrant the procedure, such as fluctuations or tremors that won’t go away with medication. Also, they need to be pretty sharp cognitively, and they can’t have any significant psychiatric or ongoing mood disturbances.”
Other movement disorders that resemble Parkinson’s and do not respond to levodopa, such as atypical Parkinson’s, are not treatable with DBS.
While DBS is a well-established procedure, the added expertise of an academic medical center is an advantage for patients. “Our neurosurgeon has been involved in DBS since its outset, has performed more than 3,000 DBS procedures at Froedtert Hospital,” Dr. Brennan said. “We have fellowship-trained surgeons and neurologists trained in movement disorders who have extensive experience in programming and troubleshooting.”
Dr. Brennan emphasized the flexible ways Froedtert Hospital makes these resources available to community physicians and neurologists. “We can do the surgery and the programming, or we can do the surgery and refer patients back to their referring physician if the doctor wants to follow up with them, monitor the medications and do the programming,” he said. “We can set this up however they want.”
