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DBS surgery

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Dear Doctor:


Can you please clarify for me who are the best candidates for DBS surgery? Is it always successfull? What are the drawbacks or side effects? Who would not be a candidate? Thanks.

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This is from a recent article our group wrote and I hope you find it helpful. I always recommend a multidisciplinary workup by an experienced center before serious consideration of DBS as not everyone is a candidate. There is also a segment at mdc.mbi.ufl.edu DBS AM I A CANDIDATE, and the NPF on their main website www.parkinson.org has a free book for download. I hope this assists you with what you need.


Over the past several years, deep brain stimulation (DBS) has become established as a safe and effective treatment for select patients with medication refractory Parkinson’s disease (PD)(1-3). DBS commonly results in marked reduction in disability due to Parkinsonian symptoms and dramatic improvement in quality of life for appropriately selected patients(1, 4, 5). Identifying those patients who are likely to benefit from DBS is a critically important first step toward successful surgical intervention. The majority of patients with PD are diagnosed and followed by primary care physicians(5). Therefore it is critical that the essential knowledge regarding recent advances in the surgical treatment of PD be clearly and effectively transferred into the primary care setting. In this article we will review the necessary information a primary care physician would require to screen his or her patients as potential DBS candidates. The recent introduction of the Florida Surgical Questionnaire for PD (FLASQ-PD)(4) now enables a primary care physician to diagnose and screen potential surgical candidates in ten minutes or less.


What is Deep Brain Stimulation?


Chronic DBS is a relatively new procedure introduced in the late 1980’s(6). It utilizes an implantable electrode, which may be used in place of, or in conjunction with, ablative brain procedures such as pallidotomy or thalamotomy (thermal burning of the globus pallidus or thalamus). Patients with PD, tremor, dystonia, or OCD with or without Tourette who are medically refractory to therapy, and who have no cognitive difficulties or “minimal” cognitive dysfunction may be appropriate candidates.

The procedure is FDA approved and the currently available device is manufactured by the Medtronic corporation. The device has four electrode contacts (quadrapolar), and depending on the disorder and/or the target one may use variably sized contacts with different spacing arrangements. Each contact can be activated utilizing monopolar or bipolar stimulation, and multiple settings can be adjusted for individual patient needs. These settings include the pulse width, frequency, and amplitude of stimulation. The DBS electrode is implanted into a specific target within the brain, and is attached to a programmable pulse generator (Figure 1). The pulse generator, or neurostimulator, is implanted in a subcutaneous pocket below the clavicle and connected to the DBS electrode in the brain via a tunneled extension cable that passes subcutaneously over the clavicle, and across the posterior aspect of the neck and skull.

Careful patient selection is the first and most important step for the success of DBS. There are no standardized criteria for choosing candidates, and criteria may differ depending on the targeted symptom or disorder.

Selecting Surgical Candidates

PD, is a slowly progressive neurodegenerative disorder (cardinal manifestations- resting tremor, bradykinesia, rigidity, gait disorder), and can present many challenges for the primary care physician. Ten to twenty percentage of patients may be eligible for surgical procedures such as DBS. Some patients following medical optimization and disease progression may become future candidates. Finally, a third group of patients will despite best medical optimization be poor DBS candidates. Understanding who are the “best” candidates, and preparing those who will be future candidates should be a primary aim of physicians treating PD.

Although there are no set criteria for surgical candidacy, recently a triage questionnaire was validated for this purpose. The FLASQ-PD(4) is a 5-section screener that includes: (A) criteria for the diagnosis of “probable” idiopathic PD, (B) potential contraindications to PD surgery, © general patient characteristics, (D) favorable/unfavorable characteristics, and (E) medication trial information subscores. The scoring system was designed to assign higher scores to better surgical candidates. The highest/best possible FLASQ-PD score is 34 with 0 red flags, and the lowest/worse possible FLASQ-PD score is 0 with 8 red flags. A red flag is a sign or symptom that would automatically put a patient at high risk for a complication of surgery. A score of approximately 25 without red flags indicates a potentially good surgical candidate. This questionnaire can be filled out and scored by a general practitioner, advanced clinical nurse practitioner, a physican assistant, or trained nurse.

Potential candidates who score well on this questionnaire may require medical optimization with a neurologist (preferably a movement disorders neurological specialist if one is available), a neurosurgeon trained in DBS, a neuropsychologist, and maybe a psychiatrist, particularly if there is a history of or the patient has currently active psychiatric disease. A special MRI for targeting the brain (“fusable” and very thin slices) will be required, and therefore an image does not need to be ordered by the primary care physician (it will probably be reordered if one is sought too early in the process). Some patients may require a speech and swallowing evaluation, and possibly even physical and occupational therapy.

The best PD surgical candidates have idiopathic PD (not parkinsonism which includes other diagnoses such as multiple system atrophy, progressive supranuclear palsy, Lewy body disease, corticobasal degeneration), tend to be younger (below age 69, but may be older), have a great response to medication (at least 30% improvement, but preferably higher), be medication refractory to symptoms (wearing off of medications prior to the next dose, on-off fluctuations, dyskinesias, etc.), and have no or little cognitive dysfunction. Perhaps the most controversial aspect of patient selection is defining unacceptable cognitive dysfunction, especially since many PD patients suffer from frontal and memory deficits, but are quite functional in their daily lives. A general rule is that PD patients with a lot of memory or cognitive problems, and those who get disoriented frequently are poor candidates and can be made worse from surgery. The neuropsychologist can help by performing a full screening visit including tests of memory and cognition. Patients will need to be cognitively intact enough to participate in an awake surgery, and in multiple programming visits and medication adjustments.

Tips for the Primary Care Physician in Picking Parkinson Disease Surgical Candidates

Each of the items and subscales of the FLASQ-PD offers insight for choosing which patients will be appropriate for DBS surgery. A commonly held misconception is that PD patients who cannot walk and are severely demented, make up the best pool of patients for DBS. This is not the case. The best patients for DBS are not demented ambulatory, and those that still respond well to parkinsonian medications (1, 4, 7, 8). Below is a review of the subscales of the FLASQ-PD with particular attention to characteristics that are important for primary care physicians and geriatricians to consider in PD surgical candidacy.

Diagnosis of Parkinson’s Disease

There are strict criteria for the diagnosis of idiopathic levodopa responsive PD. It is important that patients selected for DBS meet these criteria. Diagnosis (section A) is contingent upon the following: 1- presence of bradykinesia (slowness of movement with a loss of amplitude and often fatigue with finger taps, rapid alternating movements, and foot taps), 2- presence of two of the following: rigidity, 4-6 Hz resting tremor, and postural instability not due to visual, vestibular, cerebellar, or proprioceptive dysfunction, and 3- three of the following: unilateral onset, resting tremor, progressive disorder, asymmetry of symptoms, clear responsiveness to levodopa, dopamine related dyskinesia, clinical course for at least five years, and responsiveness to levodopa for at least five years.

Red Flags- Absolute Contraindications for DBS Surgery

The “red flags” (section B) are a collection of signs and symptoms that may represent contraindications to surgery. These include 1- the presence of primitive reflexes (Glabellar tap, palmar grasp, snout, suck, and palmomental reflexes that may all indicate early or latter stage dementia), 2- supranuclear gaze palsy (trouble moving the eyes in a vertical direction which may indicate progressive supranuclear palsy), 3- ideomotor apraxia (inability to know how to perform skilled movements such as the use of tools e.g. a hammer, scissors or scrambling eggs- this may indicate dementia, corticobasal degeneration or another neurodegenerative condition), 4- autonomic dysfunction (early erectile dysfunction in the first year of illness, problems with orthostasis, digestion, or constipation can be signs of multiple system atrophy or Shy-Drager syndrome- idiopathic levodopa responsive PD can have some autonomic dysfunction so one must be careful with this judgement), 5- wide-based gait (can indicate ataxia, cerebellar dysfunction, olivopontocerebellar degeneration or another form of parkinsonism), 6- more than mild dementia (this can be worsened by surgery, and patients may not be able to adequately participate in the feedback needed for their care), 7- severe psychosis (often a sign of dementia, and can be made worse by surgery if not treated and controlled), and 8- unresponsiveness or naivity to levodopa (a good response to dopamine replacement defines PD, and what responds to medications responds to surgery, so this factor is a must for almost all candidates).

General Characteristics

There are several general characteristics (section C) that if present will improve surgical candidacy. Age is relative with regard to being a positive or negative attribute(9). Younger patients tend to do better with brain surgeries, and DBS(1), However, we the average age of patients with PD is in their sixties, making “age” criteria relative. In general there is literature suggesting that age above 69 may impart increased cognitive risk for patients(10). We routinely operate on patients into the mid 70’s, and we consider other older candidates based on total surgical risk (we may not exclude based on age). The older you are, the more atrophy you have in your brain, and the more likely you are to hemorrhage. Also, older patients may have friable skin that if too thin will erode and expose the implanted device to infection and other complications.

We usually choose patients who have had PD for 5 or more years. Many PD syndromes, can mimic idiopathic cases, and show levodopa responsiveness early in the course of the disease. Waiting five years will eliminate most of these cases from the surgical pool. Also, a five year period is a reasonable mimimal amount of time for attempting to treat with medications, prior to consideration of surgery. In our experience, most, but not all candidates will have had PD for seven or more years prior to DBS.

On-off fluctuations are a side effect of PD that may occur when a patient takes their medication (usually dopamine or a dopamine agonist), and the response either has a delay to effect (minutes to hours), and/or a wearing off prior to the next dose. Sometimes this problem can be addressed by adding other medications, adding doses, increasing doses, or moving intervals closer together. When the neurodegenerative process progresses to a state where the buffer for levodopa in the brain is depleted, side effects of medications may occur. When the therapeutic window is small (which usually is seen in moderate to severe PD), patients may experience dance like movements when the PD medicine is “on,” and be stiff and rigid when the medicine has worn off. This situation is referred to as on-off fluctuations with dyskinesias (hyperkinetic dance like movements). Sometimes patients can develop postures where agonist muscles co-contract against antagonist muscles, and result in abnormal and often painful foot turning, hand clenching, or other manifestations. On-off fluctuations, dyskinesias, and dystonia are all general characteristics that if present respond well to DBS.

One general characteristic not included on the FLASQ-PD, but important to consider is well controlled hypertension. Hypertension increases the surgical risks of bleeding when microelectrodes are utilized for mapping the brain(11).

Favorable-Unfavorable Characteristics

There are a number of favorable/unfavorable characteristics (section D) of a PD patient that the primary physician should be aware of when choosing candidates for DBS. Patients with PD may shuffle when walking, freeze, or even chase their center of gravity when ambulating (festination). These problems may lead to falling. In addition, patients may have balance dysfunction. If these symptoms do not respond to the best “on” response from levodopa and/or dopamine agonists when medications have been optimized, they will not respond to DBS. Checking whether these troubling symptoms respond to medications, and having a frank discussion with the patient about perceived outcomes can ensure better selection of candidates.

Blood thinners such as warfarin are relative contraindications to DBS surgery. They will increase the intra-operative bleeding risk, and depending on individual circumstances, decisions will need to be made regarding the safety of temporary discontinuation prior to surgery and reinstitution following the procedure. We have operated on high risk patients who need to be hospitalized pre-operatively, converted to heparin, and then restarted on coumadin following DBS.

The are several other useful characteristics to keep in mind when choosing DBS candidates. PD patients with swallowing dysfunction will be at risk for aspiration and other co-morbid related complications. Similarly, incontinence will have the potential to increase infection. Severe cognitive problems, untreated affective disorders (depression, anxiety, or other)(12) have the potential worsen or become magnified as a result of the surgery.

Medication Trials

Prior to referring a patient for DBS surgery, a primary care doctor should be sensitive as to whether a patient has had an adequate medical trial (section E). First, and most important is that there is a documented excellent response to levodopa (Sinemet). Absence of this response may indicate another parkinsonian syndrome, and therefore a poor candidate. Many neurologists use a scale called the Unified Parkinson Disease Rating Scale (UPDRS), and perform it when patients are in their practically defined “off medication” state, following 12 hours without medications (usually overnight). Patients are then administered a suprathreshold dose of their medications (an extra 1/2 – 1 sinemet) and repeat motor testing is performed. In general the best surgical candidates have a change of 30% or greater on this scale. Patients with less than a 30% change may not be good surgical candidates. This on-off administration also gives the practitioner a nice starting point for discussing what will and what will not respond to surgery. Only features of PD that respond to medications will respond to surgery. We have developed a mnemonic device to help patients and physicians understand what will and will not respond to surgery (Figure 2)(13). We carefully review this before and after any operation and document the results of the discussion to prevent failures in patient perceived benefits of surgery. It should be noted that it is adequate for a primary care provider to document levodopa responsiveness and then refer to a neurologist or movement disorders neurologist for administration of appropriate screening tools like the UPDRS.

The general practitioner and general neurologist must move beyond two to three times a day dosing of sinemet and/or dopamine agonists. As PD progresses, the medications must be adjusted, especially as the disease course changes. Medication intervals should be moved closer (strict 2, 3,4, or 5 hour intervals as needed). We prefer to define specific times to take medications and to write the schedule for patients at each visit, as opposed to instructing for example q three hours. Doses at each interval of both levodopa and of the dopamine agonist must be increased accordingly, to maximize benefits and to minimize side effects. It is not uncommon for a PD patient to be on carbidopa/levodopa 25/100 1 ½ tablets every 3 hours with 3 mg of requip at each interval. Wearing off can also be addressed by adding a dopamine extender medication like entacapone or tolcapone (COMT inhibitors). Amantadine can be used in cases of severe dyskinesia. If increasing doses and frequency of medications cannot correct on-off fluctuations, dyskinesia, and/or dystonia it may be time to consider a surgical therapy.

Exceptional Circumstances (Medication Refractory Tremor and Dyskinesia)

Occassionally, PD patients will present with very severe tremor, but all other features of their disease will be adequately controlled with medications. In these circumstances we recommend increasing doses and frequency of carbidopa/levodopa, adding a dopamine agonist and an anticholinergic (such as trohexyphenidyl or ethopropazine) for control of the shaking. If this strategy fails to improve the tremor, DBS may be indicated if surgical risk is otherwise acceptable.

Similarly, there are patients who would not otherwise be surgical candidates, but their dykinesia is so severe, and often violent that they should be considered on a case by case basis. Complex medication trials may be best performed in partnership with a neurologist.

STN versus GPi: Choosing Surgical Targets for DBS

Brain target selection in PD depends on many factors, and may include the level of expertise of the center, as well as the specific symptoms of an individual patient. In most cases, the subthalamic nnucleus (STN) and the globus pallidus interna (GPi), (both FDA approved) which improve levodopa responsive symptoms, are the targets of choice.. On occasion, patients with tremor predominant PD, an early disease course, and severe tremor, may be appropriate for thalamic ventralis intermedius (Vim) DBS, with the caveat that tremor will likely be the only symptom treated, and leg tremor may or may not be improved. Most centers implant one DBS on each side of the brain in a single surgical sitting. However, unilateral DBS implantation may be all that is needed in some patients, and will result in lower risk. A staged procedure can be performed if necessary, with the second side implanted only when needed.

There are currently several ongoing surgical studies which will hopefully define which target is appropriate for which symptom in PD(3).


Summary of the Key Points for the Primary Care Provider

The primary care provider should be aware of the potential benefits of DBS surgery, particularly when compared to brain lesion surgery. Advantages and disadvantages are summarized in table 1. Additionally, the primary care physician should be prepared to educate PD patients on which symptoms may respond to DBS (Table 2), and the potential complications of therapy (Table 3).


The advent of DBS for PD has made available to primary care physicians a treatment that can improve the symptoms and quality of life of PD patients that are being followed in primary care practices. Many PD patients do not have a neurologist who treats them on a regular basis, and in many cases both neurologists and patients may be unaware of the symptomatic improvement that can be achieved with DBS therapy. It is therefore important for primary care providers to identify and refer appropriate DBS candidates for multidisciplinary evaluations at experienced DBS centers.



1. Walter BL, Vitek JL. Surgical treatment for Parkinson's disease. Lancet Neurol 2004;3:719-728.

2. Krack P, Batir A, Van Blercom N, et al. Five-year follow-up of bilateral stimulation of the subthalamic nucleus in advanced Parkinson's disease. N Engl J Med 2003;349:1925-1934.

3. Okun MS, Foote KD. Subthalamic nucleus vs globus pallidus interna deep brain stimulation, the rematch: will pallidal deep brain stimulation make a triumphant return? Arch Neurol 2005;62:533-536.

4. Okun MS, Fernandez HH, Pedraza O, et al. Development and initial validation of a screening tool for Parkinson disease surgical candidates. Neurology 2004;63:161-163.

5. Twelves D, Perkins KS, Counsell C. Systematic review of incidence studies of Parkinson's disease. Mov Disord 2003;18:19-31.

6. Benabid AL, Pollak P, Gervason C, et al. Long-term suppression of tremor by chronic stimulation of the ventral intermediate thalamic nucleus. Lancet 1991;337:403-406.

7. Lang AE, Widner H. Deep brain stimulation for Parkinson's disease: patient selection and evaluation. Mov Disord 2002;17 Suppl 3:S94-101.

8. Rodriguez RL, Miller K, Bowers D, et al. Mood and cognitive changes with deep brain stimulation. What we know and where we should go. Minerva Med 2005;96:125-144.

9. Pahwa R, Wilkinson SB, Overman J, Lyons KE. Preoperative clinical predictors of response to bilateral subthalamic stimulation in patients with Parkinson's disease. Stereotact Funct Neurosurg 2005;83:80-83.

10. Saint-Cyr JA, Trepanier LL, Kumar R, Lozano AM, Lang AE. Neuropsychological consequences of chronic bilateral stimulation of the subthalamic nucleus in Parkinson's disease. Brain 2000;123 ( Pt 10):2091-2108.

11. Binder DK, Rau GM, Starr PA. Risk factors for hemorrhage during microelectrode-guided deep brain stimulator implantation for movement disorders. Neurosurgery 2005;56:722-732; discussion 722-732.

12. Voon V, Saint-Cyr J, Lozano AM, Moro E, Poon YY, Lang AE. Psychiatric symptoms in patients with Parkinson disease presenting for deep brain stimulation surgery. J Neurosurg 2005;103:246-251.

13. Okun MS, Foote KD. A mnemonic for Parkinson disease patients considering DBS: a tool to improve perceived outcome of surgery. Neurologist 2004;10:290.

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the doc said that the main frame moved? have you heard of this ,he said it was rare..he wants to do it again in 10 days. is this to soon .

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There is no set time to redo DBS surgery after a frameshift. The most important thing is the swelling is gone. Usually people wait 2-4 weeks but again there is no standard. I would recommend considering a CT scan to be sure edema is gone. They will be able to tell the day of the operation.

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