Parkinson’s disease and essential tremor (a more common, but lesser known, movement disorder) afflict more than 1.5 million Americans, often with debilitating, disabling symptoms. For many years, treatment options have been limited primarily to drug therapy, whose effectiveness can decrease over time and whose side effects can be significant.
Supplementing the range of traditional drug therapies, several surgical interventions that reduce tremor and bradykinesia (slowness of movement) are now available. In addition to addressing the symptoms of Parkinson’s disease, some of these surgeries can alleviate the side effects that patients experience after prolonged use of the drugs typically prescribed for the disease - side effects such as dyskinesias (uncontrollable movements), gait problems, and balance disorders.
Why surgery?
Approximately 40 years ago, neurologists and neurosurgeons found that making a lesion - essentially, a microscopic interruption that alters signaling in the brain - in the basal ganglia or thalamus helped relieve some of the symptoms of Parkinson’s disease. Procedures such as thalamotomy and pallidotomy, which destroyed non-essential portions of the thalamus and globus pallidus (part of the basal ganglia), were noted to be rather effective in treating some of the symptoms of Parkinson’s. These procedures were quite common in the 1950s and 1960s until the discovery of levodopa (L-Dopa), the first drug that demonstrated significant benefit for Parkinson’s patients.
Despite the advent of pharmacological therapies for Parkinson’s disease, a population of patients became less responsive over time to the medications, while still others experienced disabling side effects. In the late 1970s and early 1980s, neurosurgical procedures (thalamotomy and pallidotomy) once again began increasing in number to address the needs of these patients. As mentioned, these procedures involved making a permanent destructive lesion in a specified location of the brain. In the mid-1980s, a number of neurosurgeons began using electrical stimulation instead of lesioning.
Neurosurgeons had always used electrical stimulation during the course of lesioning surgery in order to guide the lesion placement, and had found that stimulation using high- frequency electrical signals could abolish tremor. Since deep brain stimulation is a reversible and adjustable technique, it has become increasingly popular as opposed to the irreversible lesioning procedures.
What treatments are offered?
Deep Brain Stimulation (DBS) is the preferred surgical procedure for tremor, primarily because it is reversible and does virtually no damage to brain tissue. In addition, it can be used to treat symptoms other than tremor.
In DBS, the neurosurgeon implants twin electrodes deep within the brain, aided by computer guidance and 3-D physiological mapping. Each electrode is connected to a thin, insulated wire that is threaded under the skin from the top of the skull to the chest. That wire leads to a battery-operated pulse generator (like that used in a pacemaker), which is implanted beneath the skin in the chest. The electrodes send mild electrical pulses to stimulate the brain and block the signals that cause tremor. Using a hand-held magnet, the patient can control the stimulation, turning it on and off.
The surgical placement of the electrodes determines their effect, so that they may treat tremor alone (which is all that is needed for a patient with essential tremor), or they may address the range of debilitating symptoms experienced by Parkinson’s patients. In addition to tremor, these may include rigidity, bradykinesia, dyskinesia, and gait and balance problems.
Surgeons may recommend the application of DBS to one of three areas of the brain: the thalamus, the subthalamic nucleus, or the globus pallidus.
1. Thalamic Stimulation, electrical stimulation applied to the thalamus, eliminates tremor in more than 80 percent of patients. Most people experience almost complete relief from tremor on the side of the body that corresponds to the stimulation. A small number of patients, however, may receive no benefit.
2. Subthalamic Nucleus Stimulation (STN) is the most promising of the surgical procedures for Parkinson’s disease. It is used to treat not only tremor, but all of the cardinal symptoms of Parkinson’s disease. In addition, it can virtually eliminate the side effects often caused by anti-parkinsonian drugs. On average, patients can cut their medication dosages in half.
3. Globus Pallidal Stimulation. Is when a patient has already had a unilateral pallidotomy (pallidotomy on one side of the brain), but continues to have dyskinesias on both sides of the body, the surgeon may recommend stimulation of the globus pallidus with a deep brain stimulator. This is a conservative alternative to a bilateral pallidotomy (pallidotomy on both sides of the brain), which destroys brain tissue and risks the permanent impairment of cognition and language function.
The technology and expertise is available for other neurosurgical procedures, too (including stereotactic thalamotomy and stereotactic pallidotomy), but in most cases, DBS is the preferred procedure, for both safety reasons and the ability to make post-surgical adjustments.
What are the Risks?
Any surgical procedure involves a certain amount of risk, but patients are often reassured to learn how low the risks are in DBS surgery. In addition to the routine surgical risks related to bleeding, anesthesia, and possible infection, DBS presents a small risk of neurological complications such as stroke. Other possible side effects, such as difficulty with eyelid opening or double vision, can be alleviated by adjusting stimulation settings.
Who are appropriate candidates?
Initially, patients are treated with medications, which are modified or supplemented as needed to control symptoms. Deep brain stimulation is for patients who no longer respond to medication in a satisfactory manner, or those who develop side effects after years of taking medications. The treatment may also help patients who are taking medications but continue to have disabling symptoms.
Physicians make use of a battery of tests, including neurological examination, neuropsychological examination, and MRI and PET scanning to identify appropriate candidates for each procedure. Surgical recommendations are made only after a careful analysis of all possible benefits and risks.
What does the surgery entail?
Please note that not all neurosurgeons perform DBS in the same way. If you are considering DBS, please ask your surgeon how he/she performs the procedure. The following is Dr. Patrick Kelly's protocol:
After the patient’s admission to the hospital the morning of or the night before the procedure, a halo-like frame known as a stereotactic headframe is placed on the head. With the headframe on, the patient gets an MRI scan and then is brought to the operating room for the painless procedure known as electrophysiologic mapping.
In electrophysiologic mapping, neurophysiologists use sophisticated microphones, which are inserted through a small surgical opening in the skull, literally to listen to amplified noises made by the activity of the neurons, or nerve cells, in the brain. By listening to this activity, the neurophysiologist determines precisely where to place the electrode. This painless procedure involves co-operation between the patient, who remains awake, and the surgical team. For example, the physicians may ask if the patient feels a tingling in a part of the body, and if so, in what part. Since the brain contains a map of the body, the exact location of the electrode can be determined from such responses.
Once the desired location has been determined, a permanent electrode is placed. Surgeons then repeat the procedure on the opposite side of the brain, using the same method.
Once both electrodes have been placed, the anesthesiologist administers general anesthesia to make the patient sleep through the placement of the pacemaker-like stimulators. Once the procedure is completed, the patient is awakened and taken to the recovery room.
How long is the hospital stay?
Most patients stay in the hospital for two to three days, longer only if complications arise.
What happens after surgery?
From the recovery room, the patient is taken to the Intensive Care Unit for 24 hours of observation. A CT scan of the brain is performed the day of or the day following surgery to visualize placement of the electrode. After the first 24 hours, the majority of patients are moved to a private or a semiprivate room for one to two more days before discharge.
How soon after surgery will my symptoms improve?
Patients who undergo DBS often experience short-term benefit from the surgery itself, but the full benefit of the procedure is not apparent until the stimulator is turned on. Because the local swelling that results from any surgery prevents an accurate assessment of the surgery’s success, patients must heal from the surgery before the doctors can fine-tune the electrodes and the pulses that they send. Then, the team of neurophysiologists can activate the stimulator.
After the healing process - usually ten days (again this depends on the DBS team) - patients meet with a neurologist, who determines the correct type and level of electrical impulse that should be used to stimulate the thalamus, the subthalamic nucleus, or the globus pallidus. For thalamic stimulation, this determination takes less than one hour. For subthalamic stimulation, it usually takes two to four hours.
How long is the recuperation period?
Following discharge, patients are told to refrain from strenuous physical activity or heavy lifting for three weeks. Sutures are typically removed seven to ten days after surgery. In some cases, patients may return to sedentary work one to two weeks following surgery. Patients who do heavy physical activity in the course of their employment are, for disability insurance purposes, considered totally disabled for as long as three months after the surgery.
Who turns on the stimulator?
The movement disorder team activates the stimulator and determines the correct settings to obtain the maximum clinical benefit with minimal side effects. Over the first few months, patients may need a number of adjustments to determine the best settings. Once the optimal settings have been determined, patients can turn stimulation on and off with a small magnet, which is held over the pulse generator for one or two seconds.
How long does the stimulator’s battery last?
Battery longevity varies depending upon the parameter settings and number of hours the stimulator is turned on each day. The average battery lasts about five years at typical settings, with 16 hours of daily use. When the stimulator battery needs to be replaced, the surgeons implant a new one into the chest. This is usually done under local anesthesia. The delicate brain surgery involved in placing the electrodes is never repeated. The extension and lead are not replaced.
Will people notice the stimulator?
All components, with the exception of the hand held magnet, are inside the body. The stimulator may bulge slightly under the skin, but it isn’t noticeable under clothes. There also may be a slight bump on the top of the head, but it usually isn’t visible under the hair.
Can I have this done at my community hospital?
While the results of such neurosurgery are often dramatic and immediate, the surgery is by no means routine. The complexity of the pre-operative evaluation, the intra-operative monitoring, and the surgery itself demands a comprehensive team approach, requiring personnel and resources that are devoted solely to this type of surgery. Few facilities can offer this level of specialization, which is critical to ensuring both a safe procedure and a successful outcome.
Is this treatment covered by insurance?
All of the necessary testing, clinical evaluations, the surgery itself, and follow-up care are covered by most insurers.
What is the role of the referring neurologist?
Many patients are referred by community-based or network neurologists. At NYU Medical Center, the goal is to return each patient to the referring physician after the surgical intervention has been performed. Of course, the Center’s team provides all the necessary adjustments for patients implanted with deep brain stimulators, and its physicians are always available to help out with questions or problems that arise.
Can you summarize the benefits of DBS?
DBS has significantly improved the quality of life for many patients, allowing them to regain independence and resume many normal activities. In clinical studies, nine out of ten Parkinson’s disease patients experienced a significant improvement in functional ability with DBS.
