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The 9th International Congress of Parkinson's Disease and Movement Disorders - Part Four: Programming following Deep Brain Stimulation

The Parkinson Alliance/DBS-STN Research Team

The Principles of Programming was discussed by Dr. Michele Tagliati from Mount Sanai Medical Center in New York and Dr. Jens Volkmann from Christian-Albrechts-Universitaet Zu Kiel in Germany. The presentation included discussion about optimizing successful Deep Brain Stimulation (DBS) therapy, challenges in utilizing DBS, guidelines for initial parameter settings, the impact of DBS on medication usage, trouble shooting strategies, and their pearls of wisdom.

Drs. Tagliati and Volkmann stated that successful DBS therapy can be achieved by obtaining accurate patient selection, utilizing surgical procedures that allow for proper target and precise electrode placement, accurate medication adjustments, managing side effects, and educating and supporting the patient. Furthermore, the importance of effective treatment was reiterated and elaborated upon in a recent article by Okun and colleagues (Okun et al., 2005). These clinicians stated that successful DBS therapy is most likely to ensue when there are 1. appropriate screening procedures, 2. trained healthcare professionals performing DBS surgery, 3. trained personnel providing DBS programming, 4. access to DBS programming, 5. an interdisciplinary team approach, and 6. education for treatment providers to identify and treat complications of DBS.

Drs. Tagliati and Volkmann noted that what currently makes DBS challenging are multiple anatomical targets (trying to locate the best target for the patient's presenting problems), thousands of parameter setting combinations (12, 964 combinations of Pulse Width, Frequency, and Voltage), numerous contact configurations (65 combinations with unknown stimulation effects), and multiple time-dependent effects of stimulation (the effects of the stimulation can occur immediately or weeks or months later). Of note, "pulse width" is the duration of each stimulation.

At this point, the goal of DBS treatment [in the context of efficient placement] is to deliver DBS therapy to the brain target of interest while minimizing stimulation of surrounding structures. The lead electrode closest to the desired target provides maximal benefit and minimizes stimulation-induced adverse effects. Again, what makes this challenging is that there are multiple anatomical targets that can treat similar symptoms. As such, it is important to standardize procedures while trying to find out which site would be best suited for the individual patient. To further complicate matters, researchers and clinicians are attempting to discern whether specific cells within these anatomical structures or the fibers around and within the structures are responsible for the clinical effects seen following the high frequency stimulation.
The principle guidelines for the initial parameter settings include:

  • set frequency to 130 hz
  • set pulse width to 60 micro seconds (for STN)
  • test the therapeutic window for each contact in monopolar mode (determining the threshold for the therapeutic benefit; determine the threshold for side effects)
  • choose the contact with lowest threshold for clinical benefit and largest therapeutic width for chronic stimulation

They also addressed adjustment of medications following DBS therapy. They began by stating that there is little agreement on how to adjust medications during DBS therapy. The approach of medication modification varies from institution to institution across the United States and other parts of the world. One philosophy believes that on the day of the first DBS-STN programming, one can reduce medications or even discontinue them. Other philosophies subscribe to reducing the medications gradually and temper the reduction by observations of bodily reactions; and others still, do not reduce medications. Furthermore, the question arose, "Which is better, dose reduction or increasing intervals between doses?" Drs. Tagliati and Volkmann reportedly prefer to increase the space between dosages.

In this context, two other important points emerged. First, if levadopa/dopamine agonists are not decreased, additive side effects may present themselves. These side effects include dyskinesia, hypomania (elevated mood, increased activity, decreased need for sleep, grandiosity, racing thoughts, and the like), and/or sedation or confusion. It was mentioned that it is of great import to avoid decreasing the medications too rapidly. The second point emphasized that adverse effects may result form excessively decreasing medication. Specifically, excessively decreasing medication can lead to apathy, depression, akinesia (absence of movement), freezing of gait, and restless leg syndrome. Of note, restless leg syndrome has occurred following DBS after cutting down on levodopa in a small but significant amount of the patients.
Drs. Tagliati and Volkmann also addressed "trouble shooting strategies" for common symptoms following DBS:

1. If there is an absence of stimulation effect or sudden loss of stimulation efficacy:

  • check the status of the stimulation (accidental turning off; battery failure/end of battery life?)
  • check the integrity of electrical circuit
  • impedance measurement of the electrode, which may indicate a connection problem, broken cable, lead fracture (this will require the use of x-rays) (impedance is defined as resistance, inductive reactance, and capacitive reactance in a given electrical circuit); if the patient has normal impedance readings, it may be a short circuit outside of the electrode or misplaced or dislocated lead outside of the STN

2. If there are persistent freezing or gait problems:

 

  • most of the time it is a failure in good patient selection
  • levodopa resistant freezing is not improved by DBS-STN
  • try increasing levodopa
  • implement intensive gait training and use of walking aids (e.g., external cues)

3. Speech dysfunction:

  • speech disturbance is a frequent problem in patients with DBS-STN
  • it is important to distinguish between stimulation induced symptoms, inadequate stimulation/excessive medication reduction (unmasking the parkinsonism speech abnormalities), and levodopa/DBS refractory parkinsonian speech disorders
  • examination of the patients in stimulation off/medication off condition
    • if speech worsens in stimulation "on" situation, then it is stimulation-induced dysarthria (slurred speech)
    • if speech improves in medication "on" situation, then it is inadequate stimulation
    • if speech is not changed by medication or stimulation, then it can be considered an unresponsive parkinsonian speech disorder (hastening, freezing of speech; then refer to speech therapist)

4. depression/anhedonia/apathy: there are multiple reasons for postoperative depression, reduced drive, exhaustion, and anhedonia

  • consider comorbidity between patients with Parkinson's disease and depression/anxiety
  • reduction of dopaminergic medication too rapidly
  • increased independence postoperatively with loss of primary and secondary illness gains (what some consider the burden of normality)

5. Postural instability

  • most of time, it is attributable to failure in good patient selection
  • levodopa resistant postural imbalance is not improved by DBS-STN
  • likelihood of falling increases after surgery because of improved mobility
  • intensive gait and balance training; use of walking aids

Drs. Tagliati and Volkmann concluded by sharing the following pearls of wisdom:

1. There should be close collaboration between the neurologist and the programmer in adjusting the medications and simulation.

2. Clinicians should minimize re-programming for short-term exacerbations. It is recommended to work through the short-term changes (wait a few days, as the changes could be due to extraneous variables e.g., the weather).

3. Follow-up programming visits should include reviewing interim changes (e.g., symptom response, medication changes, and adverse effects), interrogating the device (check the impedance), and assessing the stimulation parameters making sure they are within the therapeutic window.

4. The goal is to maximize the benefit of DBS therapy, not to get the patient off medications entirely.

5. With regard to the course of the stimulation effects, there is quite a bit of variability. Motor symptoms may improve within seconds to minutes after the stimulation is activated, but there may be a delay of hours to days until the therapeutic effects are obvious or maximal. Of note, the stimulation-induced adverse effects are mostly evident immediately.

6. The patients should keep a diary of symptoms and exacerbations.

7. Remember, each patient is different.



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