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BCM - Baylor College of Medicine

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Parkinson's Disease Center and Movement Disorders Clinic

Deep Brain Stimulation (DBS)

Illustration of deep brain stimulation

While medications, such as propranolol, primidone, levodopa, dopamine agonists, botulinum toxin, and other drugs are helpful, many patients with Parkinson's disease (PD), tremor, dystonia and other movement disorders continue to experience embarrassing, troublesome or even disabling symptoms. Patients who do not obtain satisfactory response from optimal medical therapy may be considered candidates for surgical intervention. In the past, the neurosurgical treatments consisted chiefly of procedures that produced lesions to selected areas of the brain in order to control the movement disorder ("ablative surgery"). These procedures involve an incision in the scalp and drilling a hole through the skull. The surgeon than uses a "probe" (electrode) and advances it into the portion of the brain that is thought to be functioning abnormally. An electrical current is then used to heat the tip of the electrode which results in a lesion in the target brain area (nucleus). This is usually associated with a reduction of the abnormal or involuntary movement on the opposite side of the body. Although effective in most cases, there is a risk of stroke resulting in weakness on the opposite side of the body, numbness, poor coordination, speech disturbance and other complications. These potential risks are compounded when the procedure is performed bilaterally (on both sides).

In the late 1980s it was discovered that tremor can be relieved not only by a destructive lesion, but also by a high frequency stimulation of certain brain structures. This technique, called deep brain stimulation (DBS), is has replaced the traditional ablative procedures, as the surgical treatment of choice for a variety of movement disorders such as Parkinson's disease, tremors, dystonia, and tics. In this procedure, the DBS lead, which actually contains four electrodes, is surgically inserted into the desired target and fixed to the skull with a ring and cap. An extension wire passes from the scalp area under the skin to the chest and is connected to an implantable pulse generator (IPG), a pacemaker-like device, which can deliver pulses with a variety of parameters, modes, and polarities to the target brain area. The IPG is surgically implanted under the skin in the upper chest area near the collar bone or under the skin in the lower abdomen. The patient can activate or deactivate the DBS system by placing a magnet over the chest area that contains the IPG. IPG is a metal "box" about two inches in diameter and about 1/2 inch thick, similar to a cardiac pacemaker. It contains a small battery and produces the electrical pulses needed for stimulation. The typical battery life is expected to be approximately five years, but this may vary depending on the individual settings and hours of use per day. The battery cannot be replaced without replacing the entire IPG. Replacing the IPG involves minor surgery. This needs to be done every 3-4 years. Recently the Activa® RC Neurostimulator (Medtronic) is available and it is the first rechargeable DBS neurostimulator. It has an expected battery life of 4-9 years and patients can choose daily or weekly battery recharge options.

The major advantage of DBS over the traditional ablative procedures is that the stimulating electrodes and parameters (frequency of stimulation, pulse width, and voltage) can be adjusted and "customized" to the needs of the individual patients. Potential risks, such as hemorrhage, stroke or infection, are rare, but should be considered when making a final decision about this treatment option. Side effects, if they occur, are usually reversible, but may include weakness, speech and swallowing difficulties, and abnormal sensations.

As a result of improved understanding of the anatomy and function of the basal ganglia, (the part of the brain involved in Parkinson's disease and other movement disorders), coupled with refinements in imaging and surgical techniques, DBS is gaining wide acceptance as a chronic treatment of not only tremor, but also other symptoms of Parkinson's disease, complications related to levodopa therapy, such as motor fluctuations and dyskinesias, and other movement disorders such as dystonia. DBS is currently being used in selected centers around the world, including at Baylor College of Medicine, to treat a variety of movement disorders. In collaboration with Dr. Richard Simpson from the Department of Neurosurgery, Houston Methodist, we have implanted over 500 DBS devices.

Since the early 1990s, clinicians from around the world, including those at Baylor College of Medicine, began to explore different brain targets to control the various movement disorders. The current data, based on the extensive experience at Baylor and abroad, provide compelling evidence that chronic, high-frequency stimulation of the ventral intermediate (VIM) nucleus of the thalamus, subthalamic nucleus (STN) and globus pallidus (GPi) improves essential tremor and Parkinson's disease. STN and GPi control not only tremor, but also motor slowness, rigidity, gait, and, most importantly, levodopa-related motor fluctuations and dyskinesias in patients with moderately advanced Parkinson's disease.

Patients interested in being evaluated to determine whether they are candidates for VIM, STN, GPi DBS, or other surgical treatments, should contact the Parkinson's Disease Center and Movement Disorders Clinic, Baylor College of Medicine, Department of Neurology (713) 798-7438.

The initial programming session after DBS surgery can last around one hour. During this session the different electrodes are tested to determine the settings that provide the most benefit with the least side effects. Patients should be aware that DBS is not a cure for Parkinson's disease and the IPG settings need to be adjusted in subsequent programming sessions. During the follow-up DBS visits, there will be a fee for the adjustment and reprogramming of pulse generator (CPT code 95971, 95974, 95975) for stimulator adjustment and for a routine follow-up visit. It is our policy that we require payment at the time of service (except for Medicare patients). We do, however, provide assistance in filing for Medicare/Third Party Payer reimbursement.

Risks and Benefits

Activa Parkinson's Control Therapy. Patients should always discuss the potential risks and benefits with a physician.

Indications. Bilateral stimulation of the GPi or the STN using Medtronic Activa Parkinson's Control Therapy is indicated for adjunctive therapy in reducing some of the symptoms of advanced, levodopa-responsive Parkinson's disease that are not adequately controlled with medication.

Contraindications. Contraindications include patients who will be exposed to MRI using a full body radio-frequency (RF) coil or a head transmit coil that extends over the chest area, patients for whom test stimulation is unsuccessful, or patients who are unable to properly operate the neurostimulator. Also, diathermy (e.g., shortwave diathermy, microwave diathermy or therapeutic ultrasound diathermy) is contraindicated because diathermy's energy can be transferred through the implanted system (or any of the separate implanted components), which can cause tissue damage and can result in severe injury or death. Diathermy can damage parts of the neurostimulation system.

Warnings/Precautions/Adverse Events. There is a potential risk of tissue damage using stimulation parameter settings of high amplitudes and wide pulse widths. Extreme care should be used with lead implantation in patients with a heightened risk of intracranial hemorrhage. Do not place the lead-extension connector in the soft tissues of the neck. Placement in this location has been associated with an increased incidence of lead fracture. Theft detectors and security screening devices may cause stimulation to switch ON or OFF, and may cause some patients to experience a momentary increase in perceived stimulation. Although some MRI procedures can be performed safely with an implanted Activa System, clinicians should carefully weigh the decision to use MRI in patients with an implanted Activa System. MRI can cause induced voltages in the neurostimulator and/or lead possibly causing uncomfortable, jolting, or shocking levels of stimulation. MRI image quality may be reduced for patients who require the neurostimulator to control tremor, because the tremor may return when the neurostimulator is turned off.

Severe burns could result if the neurostimulator case is ruptured or pierced. The Activa System may be affected by or adversely affect medical equipment such as cardiac pacemakers or therapies, cardioverter/defibrillators, external defibrillators, ultrasonic equipment, electrocautery, or radiation therapy. Safety and effectiveness has not been established for patients with neurological disease other than Parkinson's disease, previous surgical ablation procedures, dementia, coagulopathies, or moderate to severe depression; or for patients who are pregnant, under 18 years or over 75 years of age. Adverse events related to the therapy, device, or procedure can include: stimulation not effective, cognitive disorders, pain, dyskinesia, dystonia, speech disorders including dysarthria, infection, paresthesia, intracranial hemorrhage, electromagnetic interference, cardiovascular events, visual disturbances, sensory disturbances, device migration, paresis/asthenia, abnormal gait, incoordination, headaches, lead repositioning, thinking abnormal, device explant, hemiplegia, lead fracture, seizures, respiratory events, and shocking or jolting stimulation.

Common Questions about DBS Surgery

1. What are the benefits and limitations of surgery?

In patients with Parkinson's disease (PD), surgery is generally recommended at a time when medications cannot adequately control symptoms. Patients are most often referred for deep brain stimulation (DBS) surgery when they have experienced problems with dyskinesias (excessive involuntary movements that occur as a consequence of PD medications) and fluctuations (the effects of medications do not last long enough between doses). When there really are no further adjustments that can be made with medications because of these problems, surgery may be a way to limit complications from medications, and improve motor function. However, it is important to note that surgery will NOT work any better than medications ever did. The major benefits of DBS surgery in this case are to decrease "off" time and to reduce or eliminate dyskinesias. In addition, many patients report that their quality of life improves substantially after DBS. Medications can be gradually reduced after DBS, but this is not always the case and may depend on many factors.

Less frequently, PD patients are referred for surgery when their tremor is not adequately controlled despite multiple medication trials. In these cases, surgery may be the only way to control tremor, with even better results than with medications. Rarely, surgery is used as the last or only resort in patients who are unable to tolerate levodopa.

In PD, any motor PD symptoms (tremor, rigidity, slowness/incoordination, walking/balance problems) that do not get better with medications will generally not get better following DBS surgery. The only exception is when the surgery is being primarily done to control tremor. Additionally, DBS is NOT a cure for PD, and it probably does not slow or stop the underlying progression. Some symptoms such as balance difficulties, speech problems, swallowing difficulties, and cognitive decline develop or worsen as PD progresses, and cannot be addressed with DBS adjustment. Finally, the non-motor complications of PD, such as depression, problems with thinking or memory, constipation, urinary changes, or pain, are also not likely to be markedly improved by DBS. It is absolutely imperative that patients have realistic expectations and a clear understanding about the anticipated outcomes and potential risks before consenting to the procedure.

Patient with essential tremor (ET) or dystonia (including cervical dystonia or torticollis) should expect that their tremors or involuntary muscle contractions or postures are better controlled than with medications alone. However, there may be several factors that influence how well this can be done, including individual patient characteristics, duration of disease, and distribution of symptoms. DBS surgery will not help with balance problems or other associated features such as neuropathy or hearing loss.

Tremors of the head or trunk are more difficult to treat but can improve.

Patients undergoing treatment for Tourette syndrome (TS) should be aware that DBS in this condition is still under investigation and there are no guarantees about the outcome. In our experience to date in five patients, tics can substantially improve, but they do not go away completely. There may also be some improvements in co-morbidities such as obsessive-compulsive disorder and attention deficit disorder. Surgery is generally reserved for severe cases in which all medical and psychological therapies have been exhausted and unsuccessful.

2. What are the risks associated with DBS surgery?

There are potential risks associated with any brain surgery, including infection, intracerebral bleeding, leaks of the fluid surrounding the brain (cerebrospinal fluid), strokes, headaches seizures, weakness, sensory changes, technical problems, wound healing problems, disfiguring scars, prolonged hospitalization, and need for additional surgery. Additionally, there may be potential risks associated with receiving anesthesia. The percentage of patients who report or experience these complications is low, but may be different according to the surgeon that is performing the procedure. It is a good idea for patients to discuss individual complications rates with their neurosurgeon.

In addition, there may be potential risks related to the programming of the DBS device, which begins a couple of weeks after the surgical process is complete. When making adjustments to the DBS, there may be immediate short-lived side effects such as tingling, tightening sensations, visual changes, or speech problems. Much of the time, these may be eliminated by further DBS adjustment. However, certain effects may not become apparent until hours or days after the adjustment. These may include any of the above symptoms, but also mood or behavior changes, involuntary movements, worsening of the underlying symptoms, or walking and balance problems, including falls. Patients undergoing DBS for ET, especially if the procedure is done on both sides of the brain, are particularly prone to developing problems with speech or gait/balance changes. It is important that these problems are communicated to the Neurologist if they occur so that they can be rectified as soon as possible. There may be several ways that these problems can be addressed, but it is possible that the changes required to minimize such side effects will lead to less symptom control.

Less commonly, and in the long term, there may be device complications that include loss of effect, unexpected side effects, fracture or breakage of the wiring, change of position of the electrode within the brain, or infection. Some of these problems, if they develop, may require removal of the device or portions of the device.

3. How is it determined if I am a good candidate for DBS?

There is a preoperative process that all patients being considered for surgery should go through, but this differs according to the condition being treated.

Parkinson's disease 
Patients and their neurologist will decide together when it is time to consider DBS. All patients will undergo an "on/off" evaluation in which their PD symptoms are assessed under conditions of no medication, and again with the full/maximal effect of medications. This is done by asking the patient to come in for evaluation first thing in the morning without having taken any PD medications. The neurologist will make an assessment of symptoms, and then will ask the patient to take their usual first dose of medications. Once this dose has "kicked in" another assessment of symptoms will occur. This is done in order to gain a better understanding of which motor symptoms do or don't improve with medications, to help guide patient expectations of outcomes after DBS, and to ensure that DBS really does have some benefit to offer an individual. Patients are also required to undergo a neuropsychological assessment to gain a better understanding of their baseline thinking skills and psychological state. Symptoms of depression or anxiety should be appropriately addressed before undergoing brain surgery. The presence of cognitive problems, depending on their severity, may indicate a patient who is at risk of further declines after DBS. The results of these preoperative tests will help determine which part of the brain is the safest to stimulate to control symptoms. Neuropsychological evaluation before surgery also provide an important baseline assessment; in cases where cognitive or emotional problems occur after surgery, the testing can be repeated and compared to preoperative scores to help determine the cause of the problems.

Essential tremor 
Preoperative assessment of tremor severity by formal scales is usually done so that the neurologist has a baseline against which to measure the response to DBS. ET patients are also asked to undergo preoperative neuropsychological assessments for the same reasons.

Dystonia 
Preoperative assessments of dystonia symptoms are done for reasons similar to those in ET patients. Neuropsychological assessments may also be considered.

Tourette syndrome 
Preoperative video evaluation, tic rating scales, and neuropsychological assessments are obtained before surgery. In some cases, a psychiatric evaluation is required. These and other factors related to a patient's social or psychological state and support network are considered together in determining if DBS is appropriate.

Finally, all cases are reviewed at a consensus conference attended by the treating neurologist, neuropsychologist, and neurosurgeon, at which recommendations are made for or against surgery, and regarding which brain location should be stimulated. All patients will receive a follow-up call from their neurologist explaining whether surgery was recommended or not, and which location of stimulation was thought to be most beneficial. Patients will have an opportunity to ask further questions at this point before proceeding with actual surgical appointments.

4. How long will I need to stay in the hospital and what is the recovery time?

If DBS is planned for both sides of the brain, there will be two surgeries approximately 7-14 days apart. The total time for the first day is typically 6-8 hours, and includes anesthesia evaluation, placement of a halo (see #5 below), brain imaging, surgical planning, placing the electrodes, and time in the recovery room. An overnight stay in the intensive care unit is required for monitoring. The next morning, a brain scan is performed to check for complications and electrode location. Patients are discharged home provided they are feeling well and there are no problems seen on the scan. If any difficulties are experienced, the hospital stay may be extended by an extra night or two, or longer, depending on the cause.

The second surgery is to implant the pulse generator (IPG) which also contains the battery and connect it the wires that are already in the brain. This is typically done 1-2 weeks later as an outpatient day surgery, and takes about two hours. Patients go home that same afternoon or evening.

If a unilateral (one-sided) surgery is planned, the entire procedure (electrode implantation and battery placement) can be done on a single day, and will take about 4-6 hours.

There are no formal recovery or rehabilitation recommendations after DBS surgery. The surgeon will provide care instructions for the incision sites, prophylactic medications, and activity restrictions at the time of discharge after each procedure. Patients are advised to "take it easy" and to use common sense and their best judgment about returning to work or other usual activities.

The DBS is turned on at the first programming session, about four weeks after the electrode implantation to allow for any potential swelling to subside. Early activation before return to an established postoperative state may result in insufficient programming or side effects.

5. How long do I have to wear the halo?

A "halo" is a metal frame placed on the head that is required by the neurosurgeon to optimize placement of the electrodes inside the brain. This is typically attached to the skull the morning of the surgery and is kept in place until the electrode placement surgery is complete. If patients are uncomfortable with the halo, the Anesthesiologist can administer medications to ease the discomfort.

6. Will I be awake for the surgery?

Most patients are kept in a state of conscious sedation so that they are comfortable during the procedure. However, this sedation is lifted during the time that the electrodes are being placed in the brain so that the neurosurgeon can hear the electrical activity of the brain (microelectrode recording). After the target brain structure is reached, the targeted brain structure will be stimulated with electricity while the patient is asked to perform simple tasks to assess the degree of symptom control and for side effects. These steps are also essential to ensuring that the electrodes are placed in the best location to address the condition.

In some cases, it may be recommended that the electrode surgery be performed under general anesthesia. Additionally, patients participating in certain research protocols may also undergo the surgery under general anesthesia, and with MRI guidance only. No testing or microelectrode recording are performed in these situations.

During the surgery where the battery is placed and connected, general anesthesia is used.

7. Does the surgery hurt?

The brain is the only part of the body that has no sensation, so even though conscious sedation is used, patients do not feel the electrode being inserted. There may be some sensations of pressure as the holes are made in the skull through which the electrodes are placed. However, most people say that the most uncomfortable part of the procedure is when the halo is placed. There will likely be some soreness over the incision sites after each surgical procedure.

8. Will I need to shave my head for the surgery?

At minimum, a portion of the scalp will need to be shaved on either side in order to ensure clean access to the brain for the neurosurgeon and to prevent infections. Some patients and some surgeons prefer to shave the whole scalp, but this can be discussed on an individual basis with the neurosurgeon.

9. When do I return after the DBS surgery?

If staples are placed, these will need to be removed by the neurosurgeon about two weeks after the surgery. This appointment will be coordinated before hospital discharge. In some cases, absorbable sutures may be used and such an appointment will not be necessary.

The first programming session in the neurologist's office takes place about four weeks after the electrode surgery, and is scheduled once the OR date is finalized. It is imperative for patients with PD to present to the neurologist's office OFF all PD medications only since midnight the night before for ALL programming sessions. This is the only way to assure that effects and side effects are coming from the DBS alone.

We will make every effort to coordinate visits for our out-of-town patients.

10. Will my medicines change when I leave the hospital?

Medications for the neurologic condition or general health issues will not change after surgery. Patients are usually given an antibiotic and possibly a medication to prevent seizures after brain surgery. PD medications are not adjusted until after the first programming session.

11. Are there any restrictions after surgery?

Immediately following surgery, the surgical area should be kept dry until after the stitches or staples are removed. Heavy lifting or over-strenuous activities should be avoided. Specific care instructions for the surgical sites will be provided at the time of hospital discharge.

Once the electrodes and battery are implanted, it is not safe for patients to undergo body MRI scans. Brain MRIs can be performed safely under specialized protocols. The appropriate specifications are in place at the Baylor Clinic Radiology suite, but are not reliably in place elsewhere. Please contact us directly if such scanning is requested by other doctors.

Patients should not undergo diathermy after DBS implantation. Diathermy is a technique used in physical therapy in which deep heating of tissues is accomplished by a high frequency electrical current. Ultrasonic treatments or investigations without diathermy can be performed. Patients should check with their neurologist first if a therapist is recommending this type of treatment.

12. How do I activate or adjust the device?

Initial device activation must be performed in the neurologist's office at the first programming sessions. This is not done immediately after surgery to allow time for the brain to recover from the procedure itself. All patients undergoing DBS will have a control device that allows them to turn the system on and off, and check the status of the battery. This capability will be explained at the first programming appointment. Depending on the particular condition and situation, and only with certain battery types, the neurologist may program the device to allow the patient to adjust specific parameters at home.

13. How many programming sessions and follow-up appointments will I need?

After the first programming session, patients should expect to come in every 3-4 weeks for at least 2-3 more visits to optimize DBS settings, then at six months, and then annually. In PD cases, it generally takes about six months to go through the process of DBS and medication adjustment. For ET, this process may be shorter. For dystonia and TS, this process will probably take longer. Each case is different, but regardless of the situation, this process should not be rushed because it may take a few days or weeks to see the full effect of a programming session.

14. Can I get an MRI scan?

As mentioned in #11 above, once the electrodes and battery are implanted, it is not safe for patients to undergo body MRI scans. Brain MRIs can be performed safely under specialized protocols. The appropriate specifications are in place at the Baylor Clinic Radiology suite, but are not reliably in place elsewhere. Please contact us directly if such scanning is requested by other doctors.

A brain MRI scan to check the electrode location is often scheduled at six months or if unexpected difficulties are encountered with programming. These are performed on alternating Friday mornings at the Baylor Clinic.

15. Who do I call if I have questions or problems?

All questions related to preoperative neurological evaluations, programming appointments, DBS adjustment, medication adjustment, and the underlying neurologic condition should be directed to the neurologist's office:

Dr. Joseph Jankovic and Dr. Joohi Jimenez-Shahed
Parkinson's Disease Center and Movement Disorders Clinic
Baylor College of Medicine
Phone: (713) 798-7438

All questions related to surgery scheduling and care of the surgical site should be directed to the appropriate neurosurgeon's office:

Dr. Ashwin Viswanathan
Department of Neurosurgery
Baylor College of Medicine
Phone: (713) 798-4696
Email: ashwinv@bcm.edu

Dr. Richard Simpson
Department of Neurosurgery
Houston Methodist Neurological Institute
Phone: (713) 441-3800

All questions related to preoperative neuropsychological assessments should be directed to the Division of Neuropsychology:

Dr. Michele York and Dr. Adriana Strutt
Division of Neuropsychology
Baylor College of Medicine
Phone: (713) 798-8673

Any technical or service questions related to the device can be directed to the manufacturer:

Medtronic Patient Services
Phone: (800) 510-6735

©2011 Joseph Jankovic, M.D.

Selected References

Ackermans L, Duits A, van der Linden C, et al. Double-blind clinical trial of thalamic stimulation in patients with Tourette syndrome. Brain.134:832-44.

Albanese A, Romito L. Deep brain stimulation for Parkinson's disease: where do we stand? Front Neurol. 2011;2:33.

Baizabal Carvallo JF, Simpson R, Jankovic J. Diagnosis and treatment of complications related to deep brain stimulation hardware. Mov Disord. 2011;26:1398-406.

Benabid AL, Chabardes S, Mitrofanis J, Pollak P. Deep brain stimulation of the subthalamic nucleus for the treatment of Parkinson's disease. Lancet Neurol. 2009;8:67-81.

Cacciola F, Farah JO, Eldridge PR, Byrne P, Varma TK. Bilateral deep brain stimulation for cervical dystonia: long-term outcome in a series of 10 patients. Neurosurgery. 2010;67:957-63.

Diamond A, Jankovic J. Quality of life and cost effectiveness of deep brain stimulation in movement disorders. In: Tarsy D, Vitek J, Starr P,  Okun M, eds. Deep Brain Stimulation for Neurological and Psychiatric Disorders. Current Clinical Neurology Series, Human Press, Totowa, NJ, 2008:495-508.

Diamond A, Shahed J, Azher S, et al: Globus pallidus deep brain stimulation in dystonia. Mov Disord. 2006;21:692-5.

Diamond A, Shahed J, Jankovic J. The effects of subthalamic nucleus deep brain stimulation on parkinsonian tremor. J Neurol Sci. 2007;260:199-203.

Diamond A, Kenney C, Almaguer M, Jankovic J. Hyperhidrosis due to deep brain stimulation in a patient with essential tremor. Case report. J Neurosurg. 2007;107:1036-8.

Fahn S, Jankovic J. Principles and Practice of Movement Disorders, Churchill Livingstone, Elsevier, Philadelphia, PA, 2007:1-652. (Accompanied by a DVD of movement disorders.)

Ferrara J, Diamond A, Hunter C, Davidson A, Almaguer M, Jankovic J. Impact of STN-DBS on life and health satisfaction in patients with Parkinson's disease. J Neurol Neurosurg Psychiatry. 2010;81:315-9.

Isaias IU, Alterman RL, Tagliati M. Deep brain stimulation for primary generalized dystonia. Long-term outcomes. Arch Neurol. 2009;66:465-70.

Krauss J, Grossman RG, Jankovic J, eds. Pallidal Surgery for the Treatment of Parkinson's Disease and Movement Disorders, Lippincott-Raven, Philadelphia, PA, 1998;1-324.

Kenney C, Simpson R, Hunter C, Ondo W, Almaguer M, Davidson A, Jankovic J. Short-term and long-term safety of deep brain stimulation in the treatment of movement disorders. J Neurosurg. 2007;106:621-5.

Kenney C, Jankovic J. Surgical treatments of dystonia. In: Hallett M, Poewe W, eds. Therapeutics of Parkinson's Disease and Other Movement Disorders, John Wiley & Sons, Ltd, Chichester, UK, 2008:241-50.

Lyons MK. Deep brain stimulation: current and future clinical applications. Mayo Clin Proc. 2011;86:662-72.

Strutt AM, Lai EC, Jankovic J, Atassi F, Soety EM, Levin HS, Grossman RG, York MK. Five-year follow-up of unilateral posteroventral pallidotomy in Parkinson's disease. Surg Neurol. 2009;71:551-8.

Tagliati M, Jankovic J, Pagan F, Susatia F, Isaias IU, Okun MS; National Parkinson Foundation DBS Working Group. Safety of MRI in patients with implanted deep brain stimulation devices. Neuroimage. 2009;47 Suppl 2:T53-7.

Tan EK, Jankovic J. Patient selection for surgery for Parkinson's disease. Lozano AM, Gildenberg PL, Tasker RR, eds. Textbook of Stereotactic and Functional Neurosurgery, 2nd ed., Springer-Verlag, Heidleberg, Germany, 2009:1529-38.

Vasques X, Cif L, Gonzalez V, Nicholson C, Coubes P. Factors predicting improvement in primary generalized dystonia treated by pallidal deep brain stimulation. Mov Disord. 2009;24:846-53.

Vidailhet M, Vercueil L, Houeto JL, et al. Bilateral, pallidal, deep-brain stimulation in primary generalised dystonia: a prospective 3 year follow-up study. Lancet Neurol. 2007;6:223-9.

Vidailhet M, Yelnik J, Lagrange C, et al.; for the French SPIDY-2 Study Group. Bilateral pallidal deep brain stimulation for the treatment of patients with dystonia-choreoathetosis cerebral palsy: a prospective pilot study. Lancet Neurol. 2009;8:709-17.

Volkmann J, Albanese A, Kulisevsky J, et al. Long-term effects of pallidal or subthalamic deep brain stimulation on quality of life in Parkinson's disease. Mov Disord. 2009;24:1154-61.

Weaver FM, Follett K, Stern M, et al; CSP 468 Study Group. Bilateral deep brain stimulation vs best medical therapy for patients with advanced Parkinson disease: a randomized controlled trial. JAMA. 2009;301:63-73.

York MK, Dulay M, Macias A, Levin HS, Grossman R, Simpson R, Jankovic J. Cognitive declines following bilateral subthalamic nucleus deep brain stimulation for the treatment of Parkinson's disease. J Neurol Neurosurg Psychiatry. 2008;79:789-95.

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