Parkinson's Disease: When to Consider Deep Brain Stimulation
Brain surgery for Parkinson's
With Parkinson’s disease, is brain surgery a routine procedure?
Brain surgery doesn't cure Parkinson's disease, but it can bring marked relief for certain patients who've developed disabling complications from drug therapy.
Nowadays the surgical procedure of choice is deep brain stimulation (DBS). But the decision to have it isn't trivial: This is brain surgery, after all, and carries significant risks. It also demands a major commitment in time, energy, and travel for medical appointments. Medicare and most private insurers cover the expensive treatment, which is approved by the Food and Drug Administration.
When should someone with Parkinson's disease think about brain surgery?
The typical surgery candidate is a midstage Parkinson's patient five to ten years or more into the disease, who's struggling with side effects from long-term use of levodopa medication. The pill brings on dyskinesias: excessive, uncontrollable twisting and fidgeting movements of the torso, limbs, or other body parts. Symptom relief from the drug wears off and swings unpredictably between "on" and "off." If these so-called motor fluctuations are ruining a person’s quality of life, he may wish to consider surgery.
Two types of brain surgery can treat Parkinson's disease
In Parkinson's disease, dopamine-producing cells die in a key part of the brain. One consequence is that nerve cells in certain other brain areas can become hyperactive and fire off abnormal patterns of electrical activity, causing some Parkinson's symptoms. Two kinds of surgical procedures aim to eliminate or correct that excessive irregular activity:
- Deep brain stimulation (DBS). Neurosurgeons drill a hole through the skull to implant a thin metal electrode in the subthalamic nucleus (STN) or, less often, the globus pallidus (GPi). (The patient is awake during electrode placement but receives local anesthesia.) The electrode is hooked up, via wires threaded down inside the neck, to a small, battery-run neurostimulator unit, also implanted under the skin in the chest.
Like a pacemaker, the neurostimulator is computer-programmed to send a stream of tiny electrical pulses that alter or override abnormal activity in the STN or GPi. The stimulation therapy is adjustable and reversible -- it can be switched on and off with a remote control -- and the surgery can be done for both sides of the brain. Multiple follow-up medical visits are usually required to fine-tune the neurostimulator programming during the first six months.
- Brain lesioning. Surgeons insert a slender probe into the brain to heat and destroy an area in the GPi. This older technique, known as pallidotomy, is rarely used now because it creates permanent brain lesions. Its main advantage is that it requires no follow-up medical visits. It remains an option for patients who come for surgery from overseas or who live in developing countries where it would be difficult to receive the postoperative care needed with DBS.
Outcomes for Parkinson's surgery
How good is DBS at alleviating Parkinson's symptoms?
Studies show that neurostimulation reduces Parkinson's motor symptoms -- tremor, rigidity, slowness of movement, and a short, shuffling gait -- by roughly 30 to 60 percent compared with how a patient does when off medication. Such a difference could free him from having to use a walker or depending heavily on a caregiver for help with the basic chores of living. However, DBS probably won't improve his symptoms beyond his best results from past drug therapy.
Perhaps the biggest benefit to patients is that DBS can virtually eliminate medication side effects, says Philip Starr, a neurosurgeon who specializes in movement disorders at the University of California, San Francisco: "They basically have no more motor fluctuations and no dyskinesia." That's partly because they can cut back on medicine: With STN stimulation on both sides of the brain, he says, patients decrease their doses of levodopa and dopamine agonists by about half, on average.
Be advised that neurostimulation doesn't effectively treat troubles with speech, balance, freezing of gait, or cognitive dysfunction. Despite these caveats, many patients hope that these problems will get better and end up disappointed, says Starr.
How long do the benefits of DBS last?
Because DBS is relatively new, researchers are still tracking long-term outcomes. A French study published in the New England Journal of Medicine in 2003 showed that benefits persist from STN stimulation on both sides of the brain. Because DBS doesn't seem to slow Parkinson's disease, patients did show some decline in functioning ability as their disorder progressed. However, after five years, compared with when patients were off medication, neurostimulation still improved motor symptoms by around 50 percent.
The risks of brain surgery for Parkinson's disease
Any brain surgery is an invasive treatment with potential dangers, which a patient should thoroughly discuss with the medical team. Adverse effects range from postoperative headache and confusion to more serious perils, including:
- Stroke. The main risk in DBS surgery (or pallidotomy) is that about 2 out of 100 patients develop a stroke from bleeding in the brain, usually during or soon after the operation, says Starr. Mild weakness, numbness, or problems with vision or slurred speech may result. One in 100 patients have a severe stroke causing death or major permanent disability.
- Infection. With DBS surgery, the second most important risk is infection, which is usually not life-threatening. At UCSF and other brain surgery centers with considerable experience in this procedure, about 4 to 5 out of 100 patients suffer from serious infection that requires returning to the operating room to remove some or all of the device's components.
- Cognitive effects. Some patients experience depression, apathy, and impulsiveness after the surgery. DBS can also sometimes cause mild worsening in memory, thinking, and verbal fluency. These cognitive and behavioral effects tend to arise in older patients or who already had cognitive problems presurgery.
- Stimulation side effects. DBS can cause slurring of speech, blurred vision, and tingling or numbness in the skin, but these effects may lessen with adjustments to the neurostimulator.
- Hardware complications. Parts of the device may eventually erode or break through the skin. The risk of this occurring rises at a rate of about 1 percent for each year of use, says Starr. After 10 to 15 years, it's likely that some component of the DBS system will stop working and need replacing. (The battery runs down after two to five years and must be replaced.)
(For a more thorough discussion of the risks of DBS, see the resources at the end of this article.)
What kind of Parkinson's patient is a good candidate for neurostimulation?
Neurosurgery centers try to select patients who are most likely to benefit from DBS, so the person in your care would have to pass certain screening considerations to qualify.
- Correct diagnosis. An evaluation by a movement disorders neurologist must confirm that he truly has Parkinson's disease, has received optimal drug therapy, and has exhausted the options for managing medication side effects.
- Good response to levodopa. A history of getting a clear benefit from the drug is one of the best predictors of favorable results with DBS. The doctors will check whether Parkinson's medicines still ease the patient’s symptoms, even briefly. Someone who can't walk or move well even while his medication is "on" is a poor surgery candidate.
- Good cognitive function. A patient would go through neuropsychological testing to check for difficulties with memory and thinking. DBS isn't advised for anyone with significant dementia or confusion -- which could worsen from the procedure -- or with other psychiatric disorders such as depression or anxiety. The ideal patient must be able to calmly tolerate being awake during the surgery and cooperate well with medical visits and instructions afterward.
- Good general health. Medical assessments, which may include a brain scan, are needed to review whether a patient has high blood pressure, diabetes, heart disease, peripheral vascular disease, or other conditions that could increase the risk of having a stroke from brain surgery.
At UCSF, Starr says that after age 75 and particularly after 80, the risks from DBS substantially rise while the benefits decrease. But not all neurosurgeons agree, and most brain surgery centers don't use age as a criterion when screening patients.
- Strong social support. Because DBS requires a lot of complex follow-up medical care, patients need to rally their caregiver, spouses, children, or friends -- not just for emotional support, but to drive them to appointments and help them remember instructions from the clinician.
Brain surgery centers for DBS treatment
Find a center with a good track record that ideally performs at least 20 DBS procedures a year, advises Starr. Ask for the neurosurgery group's outcomes data to learn how well its patients fare and what percentage suffered adverse effects. Also ask whether the brain surgeon works closely with the neurologists who help with screening patients, Starr says. A team approach with good integration between specialties makes for better care.
For more information
A Guide to Deep Brain Stimulation Therapy for the Treatment of Parkinson's Disease, National Parkinson Foundation (PDF document)
Deep Brain Stimulation for Parkinson's Disease, Parkinson's Disease Foundation (PDF document)
FAQ for Patients: Deep Brain Stimulation for Parkinson's Disease, Department of Neurosurgery at the University of California, San Francisco
Deep Brain Stimulation, Baylor College of Medicine, Houston
Subthalamic Nucleus Deep Brain Stimulation: Information for Patients and Families, Beth Israel Deaconess Medical Center, Boston