Long-Term Clinical Experience with Directional Deep Brain Stimulation Programming: A Retrospective Review

A Bioelectric Router for Adaptive Isochronous Neurostimulation

Objective

Multipolar intracranial electrical brain stimulation (iEBS) is a method that has potential to improve clinical applications of mono- and bipolar iEBS. Current tools for researching multipolar iEBS are proprietary, can have high entry costs, lack flexibility in managing different stimulation parameters and electrodes, and can include clinical features unnecessary for the requisite exploratory research. This is a factor limiting the progress in understanding and applying multipolar iEBS effectively. To address these challenges, we developed the Bioelectric Router for Adaptive Isochronous Neuro stimulation (BRAINS) board.

Approach

The BRAINS board is a cost-effective and customizable device designed to facilitate multipolar stimulation experiments across a 16-channel electrode array using common research electrode setups. The BRAINS board interfaces with a microcontroller, allowing users to configure each channel for cathodal or anodal input, establish a grounded connection, or maintain a floating state. The design prioritizes ease of integration by leveraging standard tools like a microcontroller and an analog signal isolators while providing options to customize setups according to experimental conditions. It also ensures output isolation, reduces noise, and supports remote configuration changes for rapid switching of electrode states. To test the efficacy of the board, we performed bench-top validation of monopolar, bipolar, and multipolar stimulation regimes. The same regimes were tested in vivo in mouse primary visual cortex and measured using Neuropixel recordings.

Main Results

The BRAINS board demonstrates no meaningful differences in Root Mean Square Error (RMSE) noise or signal-to-noise ratio compared to the baseline performance of the isolated stimulator alone. The board supports configuration changes at a rate of up to 600 Hz without introducing residual noise, enabling high-frequency switching necessary for temporally multiplexed multipolar stimulation.

Significance

The BRAINS board represents a significant advancement in exploratory brain stimulation research by providing a user-friendly, customizable, open source, and cost-effective tool capable of conducting sophisticated, reproducible, and finely controlled stimulation experiments. With a capacity for effectively real-time information processing and efficient parameter exploration the BRAINS board can enhance both exploratory research on iEBS and enable improved clinical use of multipolar and closed-loop iEBS.

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.

Minimising the rate of vascular complications in Deep Brain Stimulation surgery for the management of Parkinson's disease: a single-centre 600-patient case series

Objectives

Deep Brain Stimulation (DBS) is an effective, yet underused therapy for people living with Parkinson's disease (PD) in whom tremor, motor fluctuations and/or dyskinesia are not satisfactorily controlled by oral medical therapy. Fear of vascular complications related to the operative procedure remains a strong reason for both the referrer and patient reluctance. We review the incidence of vascular complications in the first 600 patients with Parkinson's disease treated at our centre by a single neurologist/neurosurgical team.

Methods

Surgical data routinely collected for patients who underwent DBS implantation for the management of PD between the years 2001-2023 was retrospectively reviewed. Incidences of vascular complication were analysed in detail, examining causal factors.

Results

Including reimplantations, 600 consecutive DBS patients underwent implantation with 1222 DBS electrodes. Three patients (0.50%) experienced vascular complications.

Conclusion

This vascular complication rate is at the low end of that reported in the literature. Risk mitigation strategies discussed include a consistent neurosurgical team, dual methodology target and trajectory planning, control of cerebrospinal fluid egress during the procedure, use of a specialised microelectrode recording (MER)/macrostimulation electrode without an introducing brain cannula and low number of MER passes. A reduced vascular complication rate may improve the acceptability of DBS therapy for both patients and referrers.

Single-center experience of utilization and clinical efficacy of segmented leads for subthalamic deep brain stimulation in Parkinson's disease

Background

Segmented electrodes for deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson's disease (PD) enable directional current steering leading to expanded programming options.

Objective

This retrospective study covering a longitudinal period of up to 7 years compares the efficacy of segmented and non-segmented leads in motor symptom alleviation and reduction of dopaminergic medication in PD patients treated in a specialized center and assesses the long-term use of directional steering in clinical routine.

Methods

Demographic data and clinical scores before surgery and at 12-month follow-up (12MFU) as well as stimulation parameters at 12MFU and last follow-up (LFU) were assessed in all patients implanted with segmented leads between 01/2016 and 12/2019 and non-segmented leads in a corresponding time-period. Patients were classified as very good (>60 %), good (30-60 %) and poor (<30 %) responders according to DBS-induced motor improvement.

Results

Clinical data at 12MFU was available for 61/96 patients with segmented (SEG) and 42/53 with non-segmented leads (N-SEG). Mean DBS-induced motor improvement and reduction of medication at 12MFU did not differ significantly between SEG and N-SEG groups or in a subgroup analysis of steering modes. There was a lower proportion of poor responders in the SEG compared with the N-SEG group (23% vs. 31%), though not statistically significant. At LFU, the percentage of patients set at directional steering increased from 54% to 70%.

Conclusion

Efficacy in reduction of motor symptoms and medication does not differ between electrode types for STN-DBS at 12 months follow-up. The use of directional steering increases over time and may account for a lower proportion of poor responders.

Directional Deep Brain Stimulation Programming: Is the Segment Clearly Identifiable and Stable Over Time?

BACKGROUND

In our early experience programming directional deep brain stimulation (d-DBS) in PD, we found the optimal directional segment changed over time in some patients. To determine the frequency/reasons for this we examined whether (1) different programmers would identify the same segment as "optimal"; and (2) the same programmer would select the same "optimal" segment over time. We hypothesized there would be a moderately high level of agreement on optimal electrode selection between different assessors and repeated assessments by the same evaluator.

METHODS

This was a prospective, double-blind investigation evaluating the reliability and stability of programming d-DBS. Each patient underwent a mono-polar survey four times (2 time points by 2 separate assessors). The primary aim was the inter-rater agreement of selecting the optimal electrode at 1 and 6 months. The secondary aim was to determine the intra-rater agreement of selecting the optimal electrode from 1 to 6 months.

RESULTS

Twenty-one patients were enrolled. There was fair inter-rater agreement at 1 month and moderate at 6 months. There was minimal intra-rater agreement between 1 and 6 months.

DISCUSSION

The data refuted our hypothesis. Potential reasons for low agreement include (1) the arduous/subjective nature of identifying the optimal electrode in d-DBS systems, especially in well-placed electrodes; and/or (2) acute changes to the location of stimulation delivery offering temporary improvement in symptoms. Key takeaways gathered were it may, (1) behoove the programmer to explore different electrode montages after a period of time; and (2) be more efficient to review the directional electrode montage only when dictated by clinical symptoms/disease progression.

An Institutional Experience of Directional Deep Brain Stimulation and a Review of the Literature

INTRODUCTION

Directional deep brain stimulation (dDBS) has been suggested to have a similar therapeutic effect when compared with the traditional omnidirectional DBS, but with an improved therapeutic window that yields optimized clinical effect owing to the ability to better direct, or "steer," electric current. We present our single-center, retrospective analysis of our experience in the use of dDBS in patients with movement disorders and provide a review of the literature.

MATERIALS AND METHODS

We identified all patients with Parkinson disease (PD) and essential tremor (ET) who received a dDBS system between 2018 and 2022 and retrospectively examined characteristics of their longitudinal treatment. A total of 70 leads were identified across 42 patients (28 PD, 14 ET).

RESULTS

Three types of systems were implemented (single-segment activation, 45.2% of patients; multiple independent current control, 50.0%; and local field potential sensing-enabled, 4.7%). The subthalamic nucleus or globus pallidus internus was targeted in PD, and the ventral intermediate nucleus of the thalamus in ET. Across the entire cohort (n = 70 leads), at initial programming, 54.2% of leads (n = 38) were programmed using directional stimulation. At the most recent reprogramming, 58.6% of leads (n = 41) implemented directionality. In patients with PD, the average decrease in levodopa-equivalent daily dose at six months after implantation was 35.4% ± 39.2%. Despite the ability to steer current to relieve stimulation-induced side effects, ten leads in six patients required surgical revision owing to electrode malposition.

CONCLUSIONS

We show wide adaptability and implementation of directional stimulation, adding to the growing compendium of real-world uses of dDBS therapy. We used directionality to improve clinical response in both patients with PD and patients with ET and found that its programming flexibility was used at high rates long after implantation and initial programming. In patients with PD, dDBS led to a significant reduction in dopaminergic medication, suggesting sustained clinical improvement. Nonetheless, accurate surgical placement remains necessary to ensure optimal clinical outcomes.

Seeing Is Believing: Photon Counting Computed Tomography Clearly Images Directional Deep Brain Stimulation Lead Segments and Markers After Implantation

BACKGROUND AND OBJECTIVES

Directional deep brain stimulation (DBS) electrodes are increasingly used, but conventional computed tomography (CT) is unable to directly image segmented contacts owing to physics-based resolution constraints. Postoperative electrode segment orientation assessment is necessary because of the possibility of significant deviation during or immediately after insertion. Photon-counting detector (PCD) CT is a relatively novel technology that enables high resolution imaging while addressing several limitations intrinsic to CT. We show how PCD CT can enable clear in vivo imaging of DBS electrodes, including segmented contacts and markers for all major lead manufacturers.

MATERIALS AND METHODS

We describe postoperative imaging and reconstruction protocols we have developed to enable optimal lead visualization. PCD CT images were obtained of directional leads from the three major manufacturers and fused with preoperative 3T magnetic resonance imaging (MRI). Radiation dosimetry also was evaluated and compared with conventional imaging controls. Orientation estimates from directly imaged leads were compared with validated software-based reconstructions (derived from standard CT imaging artifact analysis) to quantify congruence in alignment and directional orientation.

RESULTS

High-fidelity images were obtained for 15 patients, clearly indicating the segmented contacts and directional markers both on CT alone and when fused to MRI. Our routine imaging protocol is described. Ionizing radiation doses were significantly lower than with conventional CT. For most leads, the directly imaged lead orientations and depths corresponded closely to those predicted by CT artifact-based reconstructions. However, unlike direct imaging, the software reconstructions were susceptible to 180° error in orientation assessment.

CONCLUSIONS

High-resolution photon-counting CT can very clearly image segmented DBS electrode contacts and directional markers and unambiguously determine lead orientation, with lower radiation than in conventional imaging. This obviates the need for further imaging and may facilitate anatomically tailored directional programming.

Directional electrodes in deep brain stimulation: Results of a survey by the European Association of Neurosurgical Societies (EANS)

Introduction

Directional Leads (dLeads) represent a new technical tool in Deep Brain Stimulation (DBS), and a rapidly growing population of patients receive dLeads.

Research question

The European Association of Neurosurgical Societies(EANS) functional neurosurgery Task Force on dLeads conducted a survey of DBS specialists in Europe to evaluate their use, applications, advantages, and disadvantages.

Material and methods

EANS functional neurosurgery and European Society for Stereotactic and Functional Neurosurgery (ESSFN) members were asked to complete an online survey with 50 multiple-choice and open questions on their use of dLeads in clinical practice.

Results

Forty-nine respondents from 16 countries participated in the survey (n = 38 neurosurgeons, n = 8 neurologists, n = 3 DBS nurses). Five had not used dLeads. All users reported that dLeads provided an advantage (n = 23 minor, n = 21 major). Most surgeons (n = 35) stated that trajectory planning does not differ when implanting dLeads or conventional leads. Most respondents selected dLeads for the ability to optimize stimulation parameters (n = 41). However, the majority (n = 24), regarded time-consuming programming as the main disadvantage of this technology. Innovations that were highly valued by most participants included full 3T MRI compatibility, remote programming, and closed loop technology.

Discussion and conclusion

Directional leads are widely used by European DBS specialists. Despite challenges with programming time, users report that dLeads have had a positive impact and maintain an optimistic view of future technological advances.

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.

The role of neurotransmitter systems in mediating deep brain stimulation effects in Parkinson’s disease

Deep brain stimulation (DBS) is among the most successful paradigms in both translational and reverse translational neuroscience. DBS has developed into a standard treatment for movement disorders such as Parkinson’s disease (PD) in recent decades, however, specific mechanisms behind DBS’s efficacy and side effects remain unrevealed. Several hypotheses have been proposed, including neuronal firing rate and pattern theories that emphasize the impact of DBS on local circuitry but detail distant electrophysiological readouts to a lesser extent. Furthermore, ample preclinical and clinical evidence indicates that DBS influences neurotransmitter dynamics in PD, particularly the effects of subthalamic nucleus (STN) DBS on striatal dopaminergic and glutamatergic systems; pallidum DBS on striatal dopaminergic and GABAergic systems; pedunculopontine nucleus DBS on cholinergic systems; and STN-DBS on locus coeruleus (LC) noradrenergic system. DBS has additionally been associated with mood-related side effects within brainstem serotoninergic systems in response to STN-DBS. Still, addressing the mechanisms of DBS on neurotransmitters’ dynamics is commonly overlooked due to its practical difficulties in monitoring real-time changes in remote areas. Given that electrical stimulation alters neurotransmitter release in local and remote regions, it eventually exhibits changes in specific neuronal functions. Consequently, such changes lead to further modulation, synthesis, and release of neurotransmitters. This narrative review discusses the main neurotransmitter dynamics in PD and their role in mediating DBS effects from preclinical and clinical data.