Novel Programming Features Help Alleviate Subthalamic Nucleus Stimulation‐Induced Side Effects

Imaging-Guided Subthalamic Nucleus Deep Brain Stimulation Programming for Parkinson Disease: A Real-Life Pilot Study

Background and Objectives

Deep brain stimulation (DBS) is a well-established treatment for Parkinson disease (PD), with programming methods continually evolving. This study aimed to compare the efficacy and patient burden between conventional ring-mode programming (CP-RM) and image-guided volume of tissue activated (IG-VTA) programming for subthalamic nucleus (STN) DBS in PD.

Methods

In this retrospective study, patients with PD who underwent STN-DBS between 2011 and 2014 (CP-RM group) and 2019 and 2021 (IG-VTA group) were evaluated. The primary outcome was the improvement in the UPDRS III score from preoperative OFF to postoperative ON state without medication at one-year follow-up. Secondary outcomes included hospital stay duration and programming sessions.

Results

A total of 26 patients were analyzed (IG-VTA: n = 12, CP-RM: n = 14). Both groups showed similar improvements in UPDRS III scores (IG-VTA: 43.62, CP-RM: 41.29). However, the IG-VTA group experienced shorter immediate postoperative hospital stays and fewer hospitalizations after discharge.

Discussion

IG-VTA programming preserved the clinical efficacy of STN-DBS over 1 year and reduced the patient and clinician burden of hospital stay and programming sessions. However, conclusions drawn must consider the limitations of retrospective design, differing time epochs, and evolving clinical practices. Further multicentric and prospective studies are warranted to validate these findings in the evolving field of neurostimulation.

Trial Registration Information

The trial is registered on clinicaltrials.gov (NCT05103072).

Directional deep brain stimulation electrodes in Parkinson's disease: meta-analysis and systematic review of the literature

BACKGROUND

Since their introduction in 2015, directional leads have practically replaced conventional leads for deep brain stimulation (DBS) in Parkinson's disease (PD). Yet, the benefits of directional DBS (dDBS) over omnidirectional DBS (oDBS) remain unclear. This meta-analysis and systematic review compares the literature on dDBS and oDBS for PD.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Database searches included Pubmed, Cochrane (CENTRAL) and EmBase, using relevant keywords such as 'directional', 'segmented', 'brain stimulation' and 'neuromodulation'. The screening was based on the title and abstract.

RESULTS

23 papers reporting on 1273 participants (1542 leads) were included. The therapeutic window was 0.70 mA wider when using dDBS (95% CI 0.13 to 1.26 mA, p=0.02), with a lower therapeutic current (0.41 mA, 95% CI 0.27 to 0.54 mA, p=0.01) and a higher side-effect threshold (0.56 mA, 95% CI 0.38 to 0.73 mA, p<0.01). However, there was no relevant difference in mean Unified Parkinson's Disease Rating Scale III change after dDBS (45.8%, 95% CI 30.7% to 60.9%) compared with oDBS (39.0%, 95% CI 36.9% to 41.2%, p=0.39), in the medication-OFF state. Median follow-up time for dDBS and oDBS studies was 6 months and 3 months, respectively (range 3-12 for both). The use of directionality often improves dyskinesia, dysarthria, dysesthesia and pyramidal side effects. Directionality was used in 55% of directional leads at 3-6 months, remaining stable over time (56% at a mean of 14.1 months).

CONCLUSIONS

These findings suggest that stimulation parameters favour dDBS. However, these do not appear to have a significant impact on motor scores, and the availability of long-term data is limited. dDBS is widely accepted, but clinical data justifying its increased complexity and cost are currently sparse.

PROSPERO REGISTRATION NUMBER

CRD42023438056.

Modeling the volume of tissue activated in deep brain stimulation and its clinical influence: a review

Deep brain stimulation (DBS) is a neuromodulatory therapy that has been FDA approved for the treatment of various disorders, including but not limited to, movement disorders (e.g., Parkinson's disease and essential tremor), epilepsy, and obsessive-compulsive disorder. Computational methods for estimating the volume of tissue activated (VTA), coupled with brain imaging techniques, form the basis of models that are being generated from retrospective clinical studies for predicting DBS patient outcomes. For instance, VTA models are used to generate target-and network-based probabilistic stimulation maps that play a crucial role in predicting DBS treatment outcomes. This review defines the methods for calculation of tissue activation (or modulation) including ones that use heuristic and clinically derived estimates and more computationally involved ones that rely on finite-element methods and biophysical axon models. We define model parameters and provide a comparison of commercial, open-source, and academic simulation platforms available for integrated neuroimaging and neural activation prediction. In addition, we review clinical studies that use these modeling methods as a function of disease. By describing the tissue-activation modeling methods and highlighting their application in clinical studies, we provide the neural engineering and clinical neuromodulation communities with perspectives that may influence the adoption of modeling methods for future DBS studies.

Programming Algorithm for the Management of Speech Impairment in Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease

OBJECTIVES

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease (PD) has an ambiguous relation to speech. Speech impairment can be a stimulation-induced side effect, and parkinsonian dysarthria can improve with STN-DBS. Owing to the lack of an up-to-date and evidence-based approach, DBS reprogramming for speech impairment is largely blind and greatly relies on the physician's experience. In this study, we aimed to establish an evidence- and experience-based algorithm for managing speech impairment in patients with PD treated with STN-DBS.

MATERIALS AND METHODS

We performed a single-center retrospective study to identify patients with STN-DBS and speech impairment. Onset of speech impairment, lead localization, and assessment of DBS-induced nature of speech impairment were collected. When DBS settings were adjusted for improving speech, the magnitude and duration of effect were collected. We also performed a systematic literature review to identify studies describing the effects of parameter adjustments aimed at improving speech impairment in patients with PD receiving STN-DBS.

RESULTS

In the retrospective study, 245 of 631 patients (38.8%) with STN-DBS had significant speech impairment. The probability of sustained marked improvement upon reprogramming was generally low (27.9%). In the systematic review, 23 of 662 identified studies were included. Only two randomized controlled trials have been performed, providing evidence for interleaving-interlink stimulation only. Considerable methodologic heterogeneity precluded the conduction of a meta-analysis.

CONCLUSIONS

Speech impairment in STN-DBS for PD is frequent, but high-quality evidence regarding DBS parameter adjustments is scarce, and the probability of sustained improvement is low. To improve this outcome, we propose an evidence- and experience-based approach to address speech impairment in STN-DBS that can be used in clinical practice.

Image-guided programming deep brain stimulation improves clinical outcomes in patients with Parkinson's disease

Deep brain stimulation (DBS) is an effective treatment for patients with Parkinson's disease (PD). However, some patients may not respond optimally to clinical programming adjustments. Advances in DBS technology have led to more complex and time-consuming programming. Image-guided programming (IGP) could optimize and improve programming leading to better clinical outcomes in patients for whom DBS programming is not ideal due to sub-optimal response. We conducted a prospective single-center study including 31 PD patients with subthalamic nucleus (STN) DBS and suboptimal responses refractory to clinical programming. Programming settings were adjusted according to the volumetric reconstruction of the stimulation field using commercial postoperative imaging software. Clinical outcomes were assessed at baseline and at 3-month follow-up after IGP, using motor and quality of life (QoL) scales. Additionally, between these two assessment points, follow-up visits for fine-tuning amplitude intensity and medication were conducted at weeks 2, 4, 6, and 9. After IGP, twenty-six patients (83.9%) experienced motor and QoL improvements, with 25.8% feeling much better and 38.7% feeling moderately better according to the patient global impression scale. Five patients (16.1%) had no clinical or QoL changes after IGP. The MDS-UPDRS III motor scale showed a 21.9% improvement and the DBS-IS global score improved by 41.5%. IGP optimizes STN-DBS therapy for PD patients who are experiencing suboptimal clinical outcomes. These findings support using IGP as a standard tool in clinical practice, which could save programming time and improve patients' QoL.

Medical, surgical, and physical treatments for Parkinson's disease

Although dopamine replacement therapy remains a core component of Parkinson's disease treatment, the onset of motor fluctuations and dyskinetic movements might require a range of medical and surgical approaches from a multidisciplinary team, and important new approaches in the delivery of dopamine replacement are becoming available. The more challenging, wide range of non-motor symptoms can also have a major impact on the quality of life of a patient with Parkinson's disease, and requires careful multidisciplinary management using evidence-based knowledge, as well as appropriately tailored strategies according to the individual patient's needs. Disease-modifying therapies are urgently needed to prevent the development of the most disabling refractory symptoms, including gait and balance difficulties, cognitive impairment and dementia, and speech and swallowing impairments. In the third paper in this Series, we present the latest evidence supporting the optimal treatment of Parkinson's disease, and describe an expert approach to many aspects of treatment choice where an evidence base is insufficient.

Directional deep brain stimulation in the management of Parkinson's disease: efficacy and constraints-an analytical appraisal

Deep brain stimulation (DBS) is a widely employed treatment for Parkinson's disease. However, conventional DBS utilizing ring-shaped leads can often result in undesirable side effects by stimulating nearby brain structures, thus limiting its effectiveness. To address this issue, a novel DBS electrode was developed to allow for directional stimulation, avoiding neighboring structures. This literature review aims to analyze the disparities between conventional and directional DBS and discuss the benefits and limitations associated with this innovative electrode design, focusing on the stimulation-induced side effects it can or cannot mitigate. A comprehensive search was conducted in MEDLINE/PubMed, ScienceDirect, and EBSCO databases using the Boolean search criteria: "Deep brain stimulation" AND "Parkinson" AND "Directional." Following the application of inclusion and exclusion criteria, the selected articles were downloaded for full-text reading. Subsequently, the results were organized and analyzed to compose this article. Numerous studies have demonstrated that directional DBS effectively reduces side effects associated with brain stimulation, prevents the stimulation of non-targeted structures, and expands the therapeutic window, among other advantages. However, it has been observed that directional DBS may be more challenging to program and requires higher energy consumption. Furthermore, there is a lack of standardization among different manufacturers of directional DBS electrodes. Various stimulation-induced side effects, including dysarthria, dyskinesia, paresthesias, and symptoms of pyramidal tract activation, have been shown to be mitigated with the use of directional DBS. Moreover, directional electrodes offer a wider therapeutic window and a reduced incidence of undesired effects, requiring the same or lower minimum current for symptom relief compared to conventional DBS. The utilization of directional leads in DBS offers numerous advantages over conventional electrodes without significant drawbacks for patients undergoing directional DBS therapy.

Deep brain stimulation with short versus conventional pulse width in Parkinson's disease and essential tremor: A systematic review and meta-analysis

BACKGROUND

To maximize clinical benefit and minimize stimulation-induced side effects, optimising deep brain stimulation (DBS) parameters is paramount. Recent literature suggests a potential benefit of short pulse width DBS (spDBS; ≤40 μs) over conventional pulse width DBS (cDBS; ≥60 μs) in movement disorders.

OBJECTIVE

To compare therapeutic window (TW), therapeutic and side effects and energy consumption of spDBS and cDBS in movement disorders.

METHODS

We systematically searched Medline, Embase, Cochrane Library and Web of Science. Appropriate paired analyses were performed.

RESULTS

Nine Parkinson's disease (PD) (143 patients), 4 essential tremor (ET) (26 patients) and no dystonia studies were included in the meta-analysis. TW defined as therapeutic amplitude range was larger with spDBS vs. cDBS in PD (standardized mean difference (SMD) = -1.04, p < 0.001) and ET (SMD = -0.71, p < 0.001), but the TW in terms of charge per pulse (CPP) did not differ. In PD, no differences were found in therapeutic and side effects (MDS-UPDRS-III, speech and gait, dyskinesia, non-motor symptoms and quality of life). In ET, Fahn-Tolosa-Marin Tremor Rating Scale was lower with spDBS vs. cDBS (SMD = 0.36, p < 0.001). A qualitative analysis suggested fewer stimulation-induced side effects with spDBS. CPP was lower with spDBS vs. cDBS in PD (SMD = 0.79, p < 0.001) and ET (MD = 46.46 nC, p < 0.001), but real-world data on battery longevity are lacking.

CONCLUSION

Although spDBS enlarges the TW as a wider amplitude range in both PD and ET, it does not alter TW defined by CPP. The therapeutic efficacy of spDBS is not different from cDBS in PD, but spDBS apparently induces more tremor reduction in ET.

Parkinson's Disease Tremor Differentially Responds to Levodopa and Subthalamic Stimulation

Background

Tremor in Parkinson's disease (PD) has an inconsistent response to levodopa and subthalamic deep brain stimulation (STN-DBS).

Objectives

To identify predictive factors of PD tremor responsiveness to levodopa and STN-DBS.

Material and Methods

PD patients with upper limb tremor who underwent STN-DBS were included. The levodopa responsiveness of tremor (overall, postural, and rest sub-components), was assessed using the relevant Unified Parkinson's Disease Rating Scale-III items performed during the preoperative assessment. Post-surgical outcomes were similarly assessed ON and OFF stimulation. A score for the rest/postural tremor ratio was used to determine the influence of rest and postural tremor severity on STN-DBS outcome. Factors predictive of tremor responsiveness were determined using multiple linear regression modeling. Volume of tissue activated measurement coupled to voxel-based analysis was performed to identify anatomical clusters associated with motor symptoms improvement.

Results

One hundred and sixty five patients were included in this study. Male gender was negatively correlated with tremor responsiveness to levodopa, whereas the ratio of rest/postural tremor was positively correlated with both levodopa responsiveness and STN-DBS tremor outcome. Clusters corresponding to improvement of tremor were in the subthalamic nucleus, the zona incerta and the thalamus, whereas clusters corresponding to improvement for akinesia and rigidity were located within the subthalamic nucleus.

Conclusion

More severe postural tremor and less severe rest tremor were associated with both poorer levodopa and STN-DBS response. The different locations of clusters associated with best correction of tremor and other parkinsonian features suggest that STN-DBS effect on PD symptoms is underpinned by the modulation of different networks.

Identification and Management of Persistent Stimulation-Induced Dyskinesia Associated with STN DBS: The See-Saw Dilemma

Clinical vignette

A 73-year-old woman with Parkinson's disease (PD) underwent implantation of bilateral subthalamic nucleus deep brain stimulators (STN-DBS) to address bilateral upper extremity medication-refractory tremor. Post-operatively, she experienced a "see-saw effect" where small increases in stimulation resulted in improvement in one symptom (tremor) with concurrent worsening in another (dyskinesia).

Clinical dilemma

SID is usually considered a positive predictor of DBS outcome. However, there are cases where SID cannot be optimized. Lead location and pre-operative characteristics may contribute to this adverse effect. If the combination of programming and medication adjustments fails to resolve SID, what can be done to "rescue" the outcome?

Clinical solution

Management of SID requires a gradual and steadfast programming approach. Post-operative lead localization can guide advanced programming and decision-making. Rescue surgical interventions may be considered.

Gap in knowledge

In cases where SID is persistent despite deploying persistent optimization strategies, there is limited guidance on next steps.

Essential Tremor - Deep Brain Stimulation vs. Focused Ultrasound

INTRODUCTION

Essential Tremor (ET) is one of the most common tremor syndromes typically presented as action tremor, affecting mainly the upper limbs. In at least 30-50% of patients, tremor interferes with quality of life, does not respond to first-line therapies and/or intolerable adverse effects may occur. Therefore, surgery may be considered.

AREAS COVERED

In this review, the authors discuss and compare unilateral ventral intermedius nucleus deep brain stimulation (VIM DBS) and bilateral DBS with Magnetic Resonance-guided Focused Ultrasound (MRgFUS) thalamotomy, which comprises focused acoustic energy generating ablation under real-time MRI guidance. Discussion includes their impact on tremor reduction and their potential complications. Finally, the authors provide their expert opinion.

EXPERT OPINION

DBS is adjustable, potentially reversible and allows bilateral treatments; however, it is invasive requires hardware implantation, and has higher surgical risks. Instead, MRgFUS is less invasive, less expensive, and requires no hardware maintenance. Beyond these technical differences, the decision should also involve the patient, family, and caregivers.

Efficacy of short pulse and conventional deep brain stimulation in Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

Deep brain stimulation (DBS) is a common treatment for Parkinson's disease. However, the clinical efficacy of short pulse width DBS (spDBS) compared with conventional DBS (cDBS) is still unknown.

OBJECTIVE

This meta-analysis investigated the effectiveness of spDBS versus cDBS in patients with PD.

METHODS

Four databases (PubMed, Cochrane, Web of Science, and Embase) were independently searched until October 2021 by two reviewers. We utilized the following scales and items: therapeutic windows (TW), efficacy threshold, side effect threshold, Movement Disorder Society-Sponsored Revision Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III off-medication score, Speech Intelligence Test (SIT), and Freezing of Gait Questionnaire (FOG-Q).

RESULTS

The analysis included seven studies with a total of 87 patients. The results indicated that spDBS significantly widened the therapeutic windows (0.99, 95% CI = 0.61 to 1.38) while increasing the threshold amplitudes of side effects (2.25, 95% CI = 1.69 to 2.81) and threshold amplitudes of effects (1.60, 95% CI = 0.84 to 2.36). There was no statistically significant difference in UPDRS part III, SIT, and FOG-Q scores between spDBS and cDBS groups, suggesting that treatment with both cDBS and spDBS may result in similar effects of improved dysarthria and gait disorders.

CONCLUSIONS

Compared with cDBS, spDBS is effective in expanding TW. Both types of deep brain stimulation resulted in improved gait disorders and speech intelligibility.

Utility of Postoperative Imaging Software for Deep Brain Stimulation Targeting in Patients with Movement Disorders

OBJECTIVE

The objective of this study was to evaluate the accuracy of the SureTune3 postoperative imaging software in determining the location of a deep brain stimulation (DBS) electrode based on clinical outcomes and the adverse effects (AEs) observed.

METHODS

Twenty-six consecutive patients with Parkinson disease (n = 17), essential tremor (n = 8), and dystonia (n = 1) who underwent bilateral DBS surgery (52 electrodes) were included in this study. Presurgical assessments were performed in all patients prior to surgery and at 3 and 6 months after surgery, using quality-of-life and clinical scales in each case. The SureTune3 software was used to evaluate the anatomical positioning of the DBS electrodes.

RESULTS

Following DBS surgery, motor and quality-of-life improvement was observed in all patients. Different AEs were detected in 12 patients, in 10 of whom (83.3%) SureTune3 related the symptoms to the positioning of an electrode. A clinical association was observed with SureTune3 for 48 of 52 (92.3%) electrodes, whereas no association was found between the AEs or clinical outcomes and the SureTune3 reconstructions for 4 of 52 electrodes (7.7%) from 4 different patients. In 2 patients, the contact chosen was modified based on the SureTune3 data, and in 2 cases, the software helped determine that second electrode replacement surgery was necessary.

CONCLUSIONS

The anatomical position of electrodes analyzed with SureTune3 software was strongly correlated with both the AEs and clinical outcomes. Thus, SureTune3 may be useful in clinical practice, and it could help improve stimulation parameters and influence decisions to undertake electrode replacement surgery.

A Randomized, Double-Blinded Crossover Trial of Short Versus Conventional Pulse Width Subthalamic Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) is a well-established treatment for patients with Parkinson's disease. Previous acute challenge studies suggested that short pulse widths might increase the therapeutic window while maintaining motor symptom control with a decrease in energy consumption. However, only little is known about the effect of short pulse width stimulation beyond the setting of an acute challenge.

OBJECTIVE

To compare 4 weeks of STN-DBS with conventional pulse width stimulation (60 μs) to 4 weeks of STN-DBS with short pulse width stimulation (30 μs) regarding motor symptom control.

METHODS

This study was a monocentric, double-blinded, randomized crossover non-inferiority trial investigating whether short pulse width stimulation with 30 μs maintains equal motor control as conventional 60 μs stimulation over a period of 4 weeks (German Clinical Trials Register No. DRKS00017528). Primary outcome was the difference in motor symptom control as assessed by a motor diary. Secondary outcomes included energy consumption measures, non-motor effects, side-effects, and quality of life.

RESULTS

Due to a high dropout rate, the calculated sample size of 27 patients was not met and 24 patients with Parkinson's disease and STN-DBS were included in the final analysis. However, there were no differences in any investigated outcome parameter between the two treatment conditions.

CONCLUSION

This study demonstrates that short pulse width settings (30 μs) provide non-inferior motor symptom control as conventional (60 μs) stimulation without significant differences in energy consumption. Future studies are warranted to evaluate a potential benefit of short pulse width settings in patients with pronounced dyskinesia.

A Randomized, Double-Blinded Crossover Trial of Short Versus Conventional Pulse Width Subthalamic Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) is a well-established treatment for patients with Parkinson's disease. Previous acute challenge studies suggested that short pulse widths might increase the therapeutic window while maintaining motor symptom control with a decrease in energy consumption. However, only little is known about the effect of short pulse width stimulation beyond the setting of an acute challenge.

OBJECTIVE

To compare 4 weeks of STN-DBS with conventional pulse width stimulation (60 μs) to 4 weeks of STN-DBS with short pulse width stimulation (30 μs) regarding motor symptom control.

METHODS

This study was a monocentric, double-blinded, randomized crossover non-inferiority trial investigating whether short pulse width stimulation with 30 μs maintains equal motor control as conventional 60 μs stimulation over a period of 4 weeks (German Clinical Trials Register No. DRKS00017528). Primary outcome was the difference in motor symptom control as assessed by a motor diary. Secondary outcomes included energy consumption measures, non-motor effects, side-effects, and quality of life.

RESULTS

Due to a high dropout rate, the calculated sample size of 27 patients was not met and 24 patients with Parkinson's disease and STN-DBS were included in the final analysis. However, there were no differences in any investigated outcome parameter between the two treatment conditions.

CONCLUSION

This study demonstrates that short pulse width settings (30 μs) provide non-inferior motor symptom control as conventional (60 μs) stimulation without significant differences in energy consumption. Future studies are warranted to evaluate a potential benefit of short pulse width settings in patients with pronounced dyskinesia.

Surgical Strategy for Directional Deep Brain Stimulation

Deep brain stimulation (DBS) is a well-established treatment for drug-resistant involuntary movements. However, the conventional quadripole cylindrical lead creates electrical fields in all directions, and the resulting spread to adjacent eloquent structures may induce unintended effects. Novel directional leads have therefore been designed to allow directional stimulation (DS). Directional leads have the advantage of widening the therapeutic window (TW), compensating for slight misplacement of the lead and requiring less electrical power to provide the same effect as a cylindrical lead. Conversely, the increase in the number of contacts from four to eight and the addition of directional elements has made stimulation programming more complex. For these reasons, new treatment strategies are required to allow effective directional DBS. During lead implantation, the directional segment should be placed in a "sweet spot," and the orientation of the directional segment is important for programming. Trial-and-error testing of a large number of contacts is unnecessary, and efficient and systematic execution of the programmed procedure is desirable. Recent improvements in imaging technologies have enabled image-guided programming. In the future, optimal stimulations are expected to be programmed by directional recording of local field potentials.

Deep brain stimulation fine-tuning in Parkinson's disease: Short pulse width effect on speech

BACKGROUND

subthalamic nucleus deep brain stimulation (STN-DBS) may have a detrimental effect on speech in Parkinson's disease (PD) patients and new stimulation technologies may help in addressing this issue.

OBJECTIVE

to evaluate the STN-DBS acute effect of 30 μs pulse width (30PW) versus conventional 60 μs PW (60PW) on speech and identify the core features of voice modified by 30PW.

METHODS

seven STN-DBS treated PD patients participated into a pilot cross-sectional study. Motor and speech performances were tested by means of both automatic analysis and blinded clinical evaluations in four stimulation conditions: 30PW and 60PW both at the usual amplitude and at an amplitude just below the threshold for stimulation-related side effects.

RESULTS

at the threshold amplitude, 30PW stimulation improved speech intelligibility for both words (p = 0.02) and sentences (p = 0.04), without worsening motor performance. A lower but not statistically significant voice variability and instability and percentage of stuttering disfluencies was also observed. The beneficial effect of 30PW detected by automatic analysis, was confirmed by patients' perception.

CONCLUSIONS

STN-DBS treated patients experiencing low speech intelligibility may benefit from a 30PW stimulation trial at a higher amplitude. Deep characterization of PD speech profiles may help in a better application of recent DBS hardware advances.