Deep Brain Stimulation Programming for Movement Disorders: Current Concepts and Evidence-Based Strategies

Device profile of the percept PC deep brain stimulation system for the treatment of Parkinson's disease and related disorders

INTRODUCTION

Several software and hardware advances in the field of deep brain stimulation (DBS) have been realized in recent years and devices from three manufacturers are available. The Percept™ PC platform (Medtronic, Inc.) enables brain sensing, the latest innovation. Clinicians should be familiar with the differences in devices, and with the latest technologies to deliver optimized patient care.Areas covered: In this device profile, the sensing capabilities of the Percept™ PC platform are described, and the system capabilities are differentiated from other available platforms. The development of the preceding Activa™ PC+S research platform, an investigational device to simultaneously sense brain signals and provide therapeutic stimulation, is provided to place Percept™ PC in the appropriate context.Expert opinion: Percept™ PC offers unique sensing and diary functions as a means to refine therapeutic stimulation, track symptoms and correlate them to neurophysiologic characteristics. Additional features enhance the patient experience with DBS, including 3 T magnetic resonance imaging compatibility, wireless telemetry, a smaller and thinner battery profile, and increased battery longevity. Future work will be needed to illustrate the clinical utility and added value of using sensing to optimize DBS therapy. Patients implanted with Percept™ PC will have ready access to future technology developments.

Tardive Blepharospasm May Respond to Bilateral Pallidal Deep Brain Stimulation

Background

To date, there have been no reports of tardive blepharospasm being treated with deep brain stimulation (DBS), though there have been two reports of focal blepharospasm responding favorably to bilateral pallidal DBS.

Case

A 34 year old man with tardive blepharospasm that was refractory to oral medications as well as botulinum toxin types A and B underwent bilateral pallidal DBS under general anesthesia. He had significant improvement of his severe blepharospasm by one and half months post-DBS which was sustained at last follow-up 30 months post-DBS. The best programming parameters included pulse widths of 90-100 µsec, frequencies of 140-150 Hz, and stimulating the ventral contacts in each side.

Conclusion

Our case represents the first report of medically refractory tardive blepharospasm responding favorably to bilateral pallidal DBS.

Non-monotonic kilohertz frequency neural block thresholds arise from amplitude- and frequency-dependent charge imbalance

Reversible block of nerve conduction using kilohertz frequency electrical signals has substantial potential for treatment of disease. However, the ability to block nerve fibers selectively is limited by poor understanding of the relationship between waveform parameters and the nerve fibers that are blocked. Previous in vivo studies reported non-monotonic relationships between block signal frequency and block threshold, suggesting the potential for fiber-selective block. However, the mechanisms of non-monotonic block thresholds were unclear, and these findings were not replicated in a subsequent in vivo study. We used high-fidelity computational models and in vivo experiments in anesthetized rats to show that non-monotonic threshold-frequency relationships do occur, that they result from amplitude- and frequency-dependent charge imbalances that cause a shift between kilohertz frequency and direct current block regimes, and that these relationships can differ across fiber diameters such that smaller fibers can be blocked at lower thresholds than larger fibers. These results reconcile previous contradictory studies, clarify the mechanisms of interaction between kilohertz frequency and direct current block, and demonstrate the potential for selective block of small fiber diameters.

Neuromodulation of the cerebellum rescues movement in a mouse model of ataxia

Deep brain stimulation (DBS) relieves motor dysfunction in Parkinson's disease, and other movement disorders. Here, we demonstrate the potential benefits of DBS in a model of ataxia by targeting the cerebellum, a major motor center in the brain. We use the Car8 mouse model of hereditary ataxia to test the potential of using cerebellar nuclei DBS plus physical activity to restore movement. While low-frequency cerebellar DBS alone improves Car8 mobility and muscle function, adding skilled exercise to the treatment regimen additionally rescues limb coordination and stepping. Importantly, the gains persist in the absence of further stimulation. Because DBS promotes the most dramatic improvements in mice with early-stage ataxia, we postulated that cerebellar circuit function affects stimulation efficacy. Indeed, genetically eliminating Purkinje cell neurotransmission blocked the ability of DBS to reduce ataxia. These findings may be valuable in devising future DBS strategies.

Weight Change After Subthalamic Nucleus Deep Brain Stimulation in Patients With Isolated Dystonia

Purpose: Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an effective treatment method for advanced Parkinson's disease (PD) and isolated dystonia and provides marked improvement of major motor symptoms. In addition, non-motor effects have been reported including weight gain (WG) in patients with PD after STN-DBS. However, it is still unclear whether patients with isolated dystonia also experience WG.

Methods: Data from 47 patients with isolated dystonia who underwent bilateral STN-DBS surgery between October 2012 and June 2019 were retrospectively collected. The severity of dystonia was assessed via the Burke–Fahn–Marsden Dystonia Rating Scale (BFMDRS). Changes in the body mass index (BMI) and BFMDRS score were analyzed using paired Student's t-tests. Regression analysis was performed to identify factors that affected the BMI after surgery.

Results: Postoperative WG was observed in 78.7% of patients. The percentage of overweight and obese patients increased from 25.5% (before STN-DBS) to 48.9% (at the last follow-up). The mean BMI and mean percentage change in BMI increased by 1.32 ± 1.83 kg/m² (P < 0.001) and 6.28 ± 8.34%, respectively. BMI increased more in female than in male patients. At the last follow-up, BFMDRS movement and disability scores improved by 69.76 ± 33.23% and 65.66 ± 31.41%, respectively (both P < 0.001). The final regression model analysis revealed that sex and preoperative BMI alone were independently associated with BMI change (P < 0.05).

Conclusions: STN-DBS is associated with postoperative WG with patients with isolated dystonia. WG is more prominent in female patients and is associated with preoperative weight but not with the efficacy of STN-DBS on motor symptoms.

Establishment of a Visual Analog Scale for DBS Programming (VISUAL-STIM Trial)

Background: Deep brain stimulation (DBS) has become a standard treatment for advanced stages of Parkinson's disease, essential tremor, and dystonia. In addition to the correct surgical device implantation, effective programming is regarded to be the most important factor for clinical outcome. Despite established strategies for adjusting neurostimulation, DBS programming remains time- and resource-consuming. Although kinematic and neuronal biosignals have recently been examined as potential feedback for closed-loop DBS (CL-DBS), there is an ongoing need for programming strategies to adapt the stimulation parameters and electrode configurations accurately and effectively.

Methods: Here, we tested the usefulness of a patient-rated visual analog scale (VAS) for real-time adjustment of DBS parameters. The stimulation parameters (contact and amplitude) in Parkinson's patients with STN-DBS (n = 17) were optimized based on the patient's subjective VAS rating. A Minkowski distance (M_d) was calculated to compare the individual combination of contact selection and amplitude to the stimulation parameters that resulted from classical programming based on clinical signs and symptoms.

Results: We found no statistically significant difference between VAS-based and classical programming in regard to the specific contact or amplitude used or in regard to the clinical disease severity (UPDRS).

Conclusions: Our data suggest that VAS-based and classical programming strategies both lead to similar short-term results. Although further research will be required to assess the validity of VAS-based DBS programming, our results support the investigation of the patient's subjective rating as an additional and valid feedback signal for individualized DBS adjustment.

Deep brain stimulation by optimized stimulators in a phenotypic model of dystonia: Effects of different frequencies

Deep brain stimulation (DBS) of the globus pallidus internus (GPi, entopeduncular nucleus, EPN, in rodents) has become important for the treatment of generalized dystonia, a severe and often intractable movement disorder. It is unclear if lower frequencies of GPi-DBS or stimulations of the subthalamic nucleus (STN) are of advantage. In the present study, the main objective was to examined the effects of bilateral EPN-DBS at different frequencies (130 Hz, 40 Hz, 15 Hz) on the severity of dystonia in the dt^sz mutant hamster. In addition, STN stimulations were done at a frequency, proven to be effective by the present EPN-DBS in dystonic hamsters. In order to obtain precise bilateral electrical stimuli with magnitude of 50 μA, a pulse width of 60 μs and defined frequencies, it was necessary to develop a new optimized stimulator prior to the experiments. Since the individual highest severity of dystonic episodes is known to be reached within three hours after induction in dt^sz hamsters, the duration of DBS was 180 min. During DBS with 130 Hz the severity of dystonia was significantly lower within the third hour than without DBS in the same animals (p < 0.05). DBS with 40 Hz tended to exert antidystonic effects after three hours, while 15 Hz stimulations of the EPN and 130 Hz stimulations of the STN failed to show any effects on the severity. DBS of the EPN at 130 Hz was most effective against generalized dystonia in the dt^sz mutant. The response to EPN-DBS confirms that the dt^sz mutant is suitable to further investigate the effects of long-term DBS on severity of dystonia and neuronal network activities, important to give insights into the mechanisms of DBS.

An individual patient analysis of the efficacy of using GPi-DBS to treat Huntington's disease

OBJECTIVE

The efficacy of globus pallidus internus-deep brain stimulation (GPi-DBS) for the treatment of Huntington's disease (HD) has not been validated in large-scale studies. We conducted an individual patient analysis to pool outcomes of all of the published HD-GPi-DBS studies.

METHODS

PubMed, Embase and the Cochrane Library were searched for relevant articles. The Unified Huntington's Disease Rating Scale (UHDRS)-motor and UHDRS-chorea improvements were analyzed during different follow-up periods. Secondary outcomes, including UHDRS-motor subitem scores and functional assessment results, were also analyzed. Correlation and regression analyses were conducted to find improvement predictors. This study was registered in PROSPERO (CRD42018105995).

RESULTS

Eighteen studies including 39 patients with 124 visits were analyzed. GPi-DBS significantly improved the UHDRS-motor score in <3 months (p = 0.001), 3-9 months (p < 0.001), and 9-12 months (p < 0.001), but did not continue in later follow-ups. UHDRS-chorea was significantly improved even in the >30-month follow-up (p = 0.003). Functional assessment was not improved 12 months postoperatively (p = 0.196). The Westphal variant of HD (W-HD) gained no motor benefits 6 months postoperatively (p = 0.178). The Westphal variant was the only risk factor for DBS efficacy (p = 0.044). The rate of stimulation-related adverse events was 87.2%.

CONCLUSIONS

GPi-DBS has a stable effect on chorea symptoms in HD patients. Chorea-dominant patients may be the best candidates for surgery, while attention should be paid to postoperative stimulation-related complications. Given that GPi-DBS has limited effects on other motor symptoms, W-HD patients are not surgical candidates.

Novel Recessed Electrode Geometries to Minimize Tissue Damage with Directional Selectivity in Deep Brain Stimulation

Deep brain stimulation (DBS) involves activation of targeted brain tissue through implantable electrodes to treat neurological disorders. In this study, two novel electrode designs, recessed flat-contact and recessed curvature-contact models were developed where the electrode contacts were recessed to a specified depth to improve directional selectivity. Furthermore, the contact geometry was also modified for the recessed curvature-contact model in order to obtain a hemispherical configuration that will help increase current steering and reduce the propensity of tissue damage. The predicted tissue damage produced by these models were compared to the standard array model using the Shannon tissue damage model criteria. Furthermore, the volume of tissue activated by each of the electrode models was analyzed, and the radial projection relative to the total projection of each geometry was determined as a measure of directional selectivity. Based on the trends observed in the current density, tissue damage, and volume of tissue activated (VTA) analyses, it is inferred that the recessed contact electrode geometries help improve directional selectivity and safety of DBS.

Subthalamic Nucleus Deep Brain Stimulation in Post-Infarct Dystonia

Dystonia secondary to cerebral infarcts presents months to years after the initial insult, is usually unilateral and causes significant morbidity. Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is established as the most frequent target in the management of the dystonic symptoms. We report our experience with subthalamic nucleus (STN) DBS in 3 patients with post-infarct dystonia, in whom GPi DBS was not confidently possible due to the presence of striatal infarcts. Two patients had unilateral STN DBS implantation, whereas the third patient had bilateral STN DBS implantation for bilateral dystonic symptoms. Prospectively collected preoperative and postoperative functional assessment data including imaging, medication and neuropsychology evaluations were analyzed with regard to symptom improvement. Median follow-up period was 38.3 months (range 26–43 months). All patients had clinically valuable improvements in dystonic symptoms and pain control despite variable improvements in the Burke-Fahn-Marsden dystonia rating scores. In our series, we have demonstrated that STN DBS could be an alternative in the management of post-infarct dystonia in patients with abnormal striatal anatomy which precludes GPi DBS. A multidisciplinary team-based approach is essential for patient selection and management.

Should We Consider Deep Brain Stimulation Discontinuation in Late-Stage Parkinson's Disease?

BACKGROUND

Subthalamic deep brain stimulation (STN-DBS) effects may decrease with Parkinson's disease (PD) progression. There is no indication if, when, and how to consider the interruption of DBS treatment in late-stage PD. The objective of the current study was to investigate the percentage of "poor stimulation responders" among late-stage PD patients for elaborating an algorithm to decide whether and when DBS discontinuation may be considered.

METHODS

Late-stage PD patients (Hoehn Yahr stage ≥4 and Schwab and England Scale <50 in medication on/stimulation on condition) treated with STN-DBS for at least 5 years underwent a crossover, double-blind, randomized evaluation of acute effects of stimulation. Physicians, caregivers, and patients were blinded to stimulation conditions. Poor stimulation responders (MDS-UPDRS part III change <10% between stimulation on/medication off and stimulation off/medication off) maintained the stimulation off/medication on condition for 1 month for open-label assessment.

RESULTS

Thirty-six patients were included. The acute effect of stimulation was significant (17% MDS-UPDRS part III), with 80% of patients classified as "good responders." Seven patients were classified as "poor stimulation responders," and the stimulation was switched off, but in 4 cases the stimulation was switched back "on" because of worsening of parkinsonism and dysphagia with a variable time delay (up to 10 days). No serious adverse effects occurred.

CONCLUSIONS

The vast majority of late-stage PD patients (92%) show a meaningful response to STN-DBS. Effects of stimulation may take days to disappear after its discontinuation. We present a safe and effective decisional algorithm that could guide physicians and caregivers in making challenging therapeutic decisions in late-stage PD. © 2020 International Parkinson and Movement Disorder Society.

Comparison of 3T and 7T MRI for the visualization of globus pallidus sub-segments

The success of deep brain stimulation (DBS) targeting the internal globus pallidus (GPi) depends on the accuracy of electrode localization inside the GPi. In this study, we sought to compare visualization of the medial medullary lamina (MML) and accessory medullary lamina (AML) between proton density-weighted (PDW) and T2-weighted (T2W) sequences on 3T and 7T MRI scanners. Eleven healthy participants (five men and six women; age, 19–28 years; mean, 21.5) and one 61-year-old man were scanned using two-dimensional turbo spin-echo PDW and T2W sequences on 3T and 7T MRI scanners with a 32-channel receiver head coil and a single-channel transmission coil. Profiles of signal intensity were obtained from the pixel values of straight lines over the GP regions crossing the MML and AML. Contrast ratios (CRs) for GPe/MML, GPie/MML, GPie/AML, and GPii/AML were calculated. Qualitatively, 7T visualized both the MML and AML, whereas 3T visualized the MML less clearly and hardly depicted the AML. The T2W sequence at 7T yielded significantly higher CRs for GPie/MML, GPie/AML, and GPii/AML than the PDW sequence at 7T or 3T. The T2W sequence at 7T allows visualization of the internal structures of GPi segments with high signal intensity and contrast.