An unexpectedly high rate of revisions and removals in deep brain stimulation surgery: Analysis of multiple databases

Stereo-electroencephalography in the setting of a preexisting deep brain stimulation device: illustrative case

BACKGROUND

Deep brain stimulation (DBS) and responsive neurostimulation are increasingly being used to treat drug-resistant epilepsy (DRE). However, patients who experience partial or limited improvement in seizure control could require additional surgical interventions or refinement of their epilepsy network characterization, including further stereo-electroencephalography (SEEG) investigations. SEEG in the setting of previously implanted hardware demonstrates a myriad of technical challenges. The authors present the first reported demonstration of SEEG electrode implantation with a preexisting DBS device.

OBSERVATIONS

The patient was a 36-year-old male with a history of severe DRE with focal impaired awareness seizures beginning at 7 years of age. Despite having a bilateral DBS device for the anterior nucleus of the thalamus, he continued to have 1-2 seizures per day and was offered SEEG. The patient tolerated the surgery well without any morbidity, with a successfully improved definition of his epilepsy network. SEEG allowed the medical team to titrate stimulation settings while following intracranial electrographic response.

LESSONS

SEEG in the setting of preexisting DBS can be performed safely without damage to functioning hardware, and the authors obtained characterization and localization of the epilepsy network. Further follow-up will be needed to assess the efficacy outcomes of additional intervention in this patient. https://thejns.org/doi/10.3171/CASE24854.

Lesioning Through a Directional Deep Brain Stimulation Lead in the Subthalamic Nucleus

Clinical Vignette

A 59-year-old woman with a previous subthalamic nucleus deep brain stimulation (DBS) implanted for Parkinson's disease developed a hardware related infection.

Clinical Dilemma

Wound dehiscence and infection developed and necessitated removal of the DBS system. The patient experienced excellent therapeutic benefit from her DBS and expressed concern about device removal.

Clinical Solution

The patient was offered the option of a lesioning procedure which could be performed during hardware explantation. An operative procedure was conducted where the intracranial DBS lead was connected to a radiofrequency system in a deliberate effort to create a targeted subthalamotomy through the existing DBS lead. A multilevel lesion was generated using the contacts on the directional DBS lead. Following the lesion the DBS lead and hardware were removed.

Gap in Knowledge

Creating a lesion through a DBS lead using radiofrequency ablation is a therapeutic option for patients not interested in later re-implantation or for those with a history of multiple DBS related infections. Lesioning through segmented leads introduces more complexity into the procedure.

Subjective patient rating as a novel feedback signal for DBS programming in Parkinson's disease

BACKGROUND

Deep brain stimulation of the subthalamic nucleus (STN-DBS) effectively alleviates motor fluctuations in Parkinson's disease (PD). Optimal electrode placement and effective programming significantly influence outcomes. From a patient's perspective, DBS should relieve motor symptoms while avoiding side effects. However, there is a lack of programming routines that consider patients' subjective feedback for parameter adjustment.

OBJECTIVE

This study assessed the usefulness of patients' subjective ratings as feedback for DBS programming.

METHODS

We analyzed 260 DBS settings from 11 STN-DBS patients, pairing each volume of tissue activated (VTA) with a subjective rating measured by a visual analogue scale (VAS). We performed sweet spot mapping and connectivity analyses, utilizing voxel-wise and nonparametric permutation statistics to identify neuroanatomical regions and connectivity profiles associated with the highest VAS ratings. To validate our findings, we cross-validated the results in an independent test dataset of 6 patients (189 settings) to determine if the sweet spot and connectivity profile could predict the subjective patient perception.

RESULTS

VTAs with the highest VAS scores were localized to the dorsolateral STN, consistent with published sweet spots derived from clinical data. Connectivity with the supplementary motor area (SMA) and primary motor cortex (M1) was associated with a more positive subjective perception. Connectivity profiles derived from one dataset successfully predicted outcomes in an independent dataset, as validated through leave-one-cohort-out cross-validation.

CONCLUSIONS

Mapping patients' subjective perceptions using VAS yields conclusive anatomical results that align with objective clinical and imaging measures. VAS-guided programming could provide an additional feedback mechanism for both acute and chronic DBS parameter adjustments.

A Meta-Analysis of Medication Reduction and Motor Outcomes After Awake Versus Asleep Deep Brain Stimulation for Parkinson Disease

BACKGROUND AND OBJECTIVES

There remains significant debate regarding the performance of deep brain stimulation (DBS) procedures for Parkinson disease (PD) under local or general anesthesia. The aim of this meta-analysis was to compare the clinical outcomes between "asleep" DBS (general anesthesia) and "awake" DBS (local anesthesia) for PD.

METHODS

We conducted a comprehensive literature review of all published studies on DBS for PD following PRISMA guideline on PubMed and Cochrane library from January 2004 to April 2023. Inclusion criteria included cohort ≥15 patients, clinical outcomes data which included Unified Parkinson's Disease Rating Scale (UPDRS) score and levodopa equivalent daily dosage (LEDD), and ≥3 months of follow-up. Analysis was conducted using Stata software.

RESULTS

There were 18 articles that met inclusion criteria. On meta-analysis, there were no significant differences between awake or asleep DBS with regard to percent change in UPDRS III "off" med/"on" DBS condition ( P = .6) and LEDD score ( P = .99). On subgroup analysis, we found that the choice of target had no significant effect on improvement of UPDRS III ( P = 1.0) or LEDD ( P = .99) change for the asleep vs awake operative approach. There were also no statistically significant differences between microelectrode recording (MER) use and no MER use in postoperative UPDRS III ( P = 1.0) or LEDD improvement ( P = .90) between awake and asleep surgery.

CONCLUSION

There was no significant difference in the primary motor outcomes and LEDD improvement between asleep vs awake DBS. The variables of target selection and MER use had no statistically significant impact on outcome. We find that asleep techniques are both safe and effective compared with the awake technique.

A General Framework for Characterizing Inaccuracy in Stereotactic Systems

BACKGROUND AND OBJECTIVES

Identifying and characterizing sources of targeting error in stereotactic procedures is essential to maximizing accuracy, potentially improving surgical outcomes. We aim to describe a generic framework which characterizes sources of stereotactic inaccuracy.

METHODS

We assembled a list of stereotactic systems: ROSA, Neuromate, Mazor Renaissance, ExcelsiusGPS, Cirq, STarFix (FHC), Nexframe, ClearPoint, CRW, and Leksell. We searched the literature for qualitative and quantitative work identifying and quantifying potential sources of inaccuracy and describing each system's implementation using Standards for Reporting Qualitative Research guidelines. Our literature search spanned 1969 to 2024, and various studies were included, with formats ranging from phantom studies to systematic reviews. Keyword searches were conducted, and the details about each system were used to create a framework for identifying and describing the unique targeting error profile of each system.

RESULTS

We describe and illustrate the details of various sources of stereotactic inaccuracies and generate a framework to unify these sources into a single framework. This framework entails 5 domains: imaging, registration, mechanical accuracy, target planning and adjustment, and trajectory planning and adjustment. This framework was applied to 10 stereotactic systems.

CONCLUSION

This framework provides a rubric to analyze the sources of error for any stereotactic system. Illustrations allow the reader to understand sources of error conceptually so that they may apply them to their practice.

Is the Subthalamic Nucleus Sleeping Under Nitrous Oxide-Ketamine General Anesthesia?

Nitrous oxide is a common gaseous anesthetic used in a wide range of medical procedures due to its desirable combination of anesthetic and analgesic properties. Deep brain stimulation surgery, a well-established treatment for movement disorders like Parkinson's disease, often requires precise microelectrode recordings of the awake brain's electrical signals for optimal results. However, the influence of anesthetics on these brain signals remains a critical consideration. This study investigated how nitrous oxide general anesthesia supplemented by ketamine affects the electrophysiology of the subthalamic nucleus compared to awake and low-dose ketamine sedation during deep brain stimulation procedures targeting the subthalamic nucleus of Parkinson's disease patients. Spectral analysis of subthalamic nucleus electrophysiological characteristics and statistical analysis of its electrophysiological dimensions were performed on retrospective data from three medical centers. Our findings revealed that nitrous-ketamine general anesthesia allows electrophysiological subthalamic nucleus identification, despite a slight decrease in overall activity level. Nevertheless, nitrous-ketamine showed significantly lower beta frequency power inside the nucleus compared to the ketamine and awake groups. At the group level, and in many trajectories, delineation of subthalamic nucleus subdomains can be achieved by detection of changes in the delta frequency oscillations. Notably, no differences in electrophysiological nucleus dimensions were found between the three groups. These findings suggest that it is possible to recognize the entrance and exit of the subthalamic nucleus with high confidence under nitrous oxide-ketamine anesthesia. However, the motor subregion of the nucleus is more difficult to delineate under nitrous anesthesia than ketamine sedation or awake, which may affect outcome.

Deep Brain Stimulation Electrode Deviations are Associated With Brain Stiffness Interfaces Measured by Magnetic Resonance Elastography

BACKGROUND AND OBJECTIVES

The efficacy of deep brain stimulation (DBS) relies on accurate electrode placement. Unfortunately, electrode deviation poses a persistent problem, with most electrodes demonstrating some degree of bending. Although such bending does not always result in target deviation, an estimated 3% to 8% of patients still require revision surgery to address suboptimal electrode placement. DBS electrode deviation may occur at mechanical tissue interfaces, with denser internal capsule (IC) fibers being the most likely factor. Based on basic principles of physics, we hypothesized that the angle of a planned trajectory relative to tissue interfaces created by the IC induces deviation.

METHODS

Ten patients with Parkinson disease scheduled for DBS surgery underwent preoperative 3T magnetic resonance elastography (MRE) using synchronized external vibrations to measure brain tissue stiffness. The IC stiffness interface (ICSI) was defined as the transition between the corona radiata and IC on MRE. The rate of transition was calculated as the change in stiffness across the ICSI. Postoperative computed tomography was used to measure target deviation. The angle of approach was calculated as the angle between the planned trajectory and the normal vector to the ICSI. Pearson correlations and t-tests were performed to evaluate associations between the angle of approach and target deviation.

RESULTS

Twenty-one electrode trajectories were analyzed. The mean electrode deviation was 1.27 ± 0.63 mm. A significant correlation (r = 0.57, 95% CI [0.18, 0.80], P = .007) was found between angle of approach and target deviation, with larger angles associated with greater deviations. The rate of transition did not correlate with deviation (P = .874).

CONCLUSION

MRE effectively quantifies in vivo brain tissue stiffness in Parkinson disease. The angle between the planned trajectory and the ICSI correlates with target deviation, supporting the hypothesis that tissue mechanics influence electrode bending. MRE has potential to quantify the likelihood of DBS electrode deviation, which could reduce revision surgeries and enhance clinical outcomes.

Microelectrode Recording During Deep Brain Stimulation Does Not Consistently Represent Lead Trajectory

BACKGROUND AND OBJECTIVES

Long-term outcomes in deep brain stimulation (DBS) depend on accuracy of lead placement. Microelectrode recording (MER) is a long-used adjunct to leverage neurophysiological information to confirm satisfactory trajectory of implanted electrodes. The goal of this study was to evaluate the consistency in which electrodes are placed in sampled microelectrode trajectories.

METHODS

This is a retrospective study using intraoperative computed tomography to measure final electrode deviation from MER probe placement during the DBS insertion targeting subthalamic nucleus. Fifteen patients had 29 DBS leads placed using MER assistance. Radial distance between the probe and the lead were measured for each patient using intraoperative imaging. In addition, the preoperative target to final lead error was measured in 14 patients undergoing subthalamic nucleus implants without the use of MER and compared with the 15 patients in which MER was used as an adjunct.

RESULTS

There was no significant difference in the mean radial target error (1.2 vs 1.0 mm, P = .156) when comparing the leads placed with or without MER assistance, respectively. The mean difference in final position of microelectrode compared with DBS lead was 0.9 ± 0.1 (range 0.4-2.0 mm). Of all MER-assisted electrodes placed, 44.8% (13) of electrode final positions radially deviated 1.0 mm or more from the MER probe.

CONCLUSION

Electrode placement may deviate significantly from MER trajectories. Given the concern that physiological data may not be representative of the final electrode trajectory, surgeons should consider using intraoperative imaging or other adjunctive techniques during DBS to confirm accuracy and satisfactory trajectory of DBS leads.

Disruption Driving Innovation: Optimising Efficiency in Functional Neurosurgery

INTRODUCTION

Rising NHS waiting lists are a major problem following the COVID-19 pandemic. In our institution, surgical waiting time for elective functional neurosurgical procedures, such as deep brain stimulation (DBS) and radiofrequency ablation (RFA), reached >1.5 years by the end of 2022. During 2023, reduced operating room availability, intraoperative MRI (iMRI) suite closure for refurbishment, and ongoing strikes threatened to increase waiting times further.

METHODS

Our previous surgical workflow for DBS and RFA procedures was examined. Several aspects were identified, and changes implemented to increase efficiency. Procedure numbers, waiting times, lead placement accuracy, and complication rates before and after these changes were compared.

RESULTS

Prior to 2023, an average of 0.8 new procedures were performed per surgical list. Introduction of a new workflow in 2023 allowed an average of 1.6 new procedures per surgical list (100% increase in productivity). In 2023, 95 DBS and 31 RFA procedures were performed on 79 surgical lists. This represents a 52% increase over "pre-pandemic" activity in 2019 (74 DBS, 9 RFA) on 102 available surgical lists. Mean (SD) targeting accuracy (0.8 [0.4] mm) was comparable to previous years (0.9[0.3] mm). In 2023, there were no infections requiring hardware removal and only one asymptomatic haemorrhage following an RFA procedure. The surgical waiting time was reduced from >1.5 years to <4 months by the end of 2023.

CONCLUSION

Changes in surgical workflow, with neurosurgeons working in parallel, maximise surgical efficiency and productivity, significantly increasing the number of DBS and RFA procedures without compromising accuracy and safety.

INTRODUCTION

Rising NHS waiting lists are a major problem following the COVID-19 pandemic. In our institution, surgical waiting time for elective functional neurosurgical procedures, such as deep brain stimulation (DBS) and radiofrequency ablation (RFA), reached >1.5 years by the end of 2022. During 2023, reduced operating room availability, intraoperative MRI (iMRI) suite closure for refurbishment, and ongoing strikes threatened to increase waiting times further.

METHODS

Our previous surgical workflow for DBS and RFA procedures was examined. Several aspects were identified, and changes implemented to increase efficiency. Procedure numbers, waiting times, lead placement accuracy, and complication rates before and after these changes were compared.

RESULTS

Prior to 2023, an average of 0.8 new procedures were performed per surgical list. Introduction of a new workflow in 2023 allowed an average of 1.6 new procedures per surgical list (100% increase in productivity). In 2023, 95 DBS and 31 RFA procedures were performed on 79 surgical lists. This represents a 52% increase over "pre-pandemic" activity in 2019 (74 DBS, 9 RFA) on 102 available surgical lists. Mean (SD) targeting accuracy (0.8 [0.4] mm) was comparable to previous years (0.9[0.3] mm). In 2023, there were no infections requiring hardware removal and only one asymptomatic haemorrhage following an RFA procedure. The surgical waiting time was reduced from >1.5 years to <4 months by the end of 2023.

CONCLUSION

Changes in surgical workflow, with neurosurgeons working in parallel, maximise surgical efficiency and productivity, significantly increasing the number of DBS and RFA procedures without compromising accuracy and safety.

What was first and what is next in selecting device-aided therapy in Parkinson's disease? Balancing evidence and experience

Parkinson's disease (PD) progresses with motor fluctuations emerging several years after treatment initiation. Initially managed with oral medications, these fluctuations may later necessitate device-aided therapy (DATs). Globally, various DATs options are available, including continuous subcutaneous apomorphine infusion, deep brain stimulation, levodopa-carbidopa intestinal gel, levodopa-entacapone-carbidopa intestinal gel, and subcutaneous foslevodopa/foscarbidopa infusion, each with its complexities. Hence, matching complex patients with suitable therapy is critical. This review offers practical insights for physicians managing complex PD cases. Balancing evidence and experience is vital to select the most suitable DATs, considering factors like disease stage and patient preferences. Comparative analysis of DATs benefits and risks provides essential insights for clinicians and patients. Treatment sequences vary based on availability, patient needs, and disease progression. Less invasive options like apomorphine are often preferred initially, followed by other DATs if needed. Patient selection requires comprehensive evaluations, including motor function and cognitive status. Follow-up care involves symptom monitoring and adjusting medications. Customized treatment plans are essential for optimizing PD management with DATs.

Randomized crossover trial on motor and non-motor outcome of directional deep brain stimulation in Parkinson's disease

Deep brain stimulation (DBS) with electric field steering may avoid areas responsible for side effects. This prospective randomized cross-over trial compared omnidirectional (OS) and directional (DS) subthalamic DBS in 19 patients. Electromyographically measured rigidity was the primary outcome. Motor and non-motor scores were secondary outcomes. There were no significant differences between OS and DS. In the acute setting, both conditions improved motor scores compared to no stimulation. Motor symptoms improved after 3 weeks of OS relative to acute measurements, whereas they worsened under DS. The more ventral the active contact, and the less the motor improvement sweet spot was stimulated, the greater the benefit of DS over OS for executive function. Accurate OS of the dorsal subthalamic nucleus ensures motor and non-motor improvements. While DS can mitigate executive decline stemming from off-target stimulation, it may lead to worse motor outcomes. Larger, long-term studies are needed to confirm these findings. (Registration: subthalamic steering for therapy optimization in Parkinson's Disease ClinicalTrials.gov: NCT03548506, 2018-06-06).

Modeling electrical impedance in brain tissue with diffusion tensor imaging for functional neurosurgery applications

Objective.Decades ago, neurosurgeons used electrical impedance measurements in the brain for coarse intraoperative tissue differentiation. Over time, these techniques were largely replaced by more refined imaging and electrophysiological localization. Today, advanced methods of diffusion tensor imaging (DTI) and finite element method (FEM) modeling may permit non-invasive, high-resolution intracerebral impedance prediction. However, expectations for tissue-impedance relationships and experimentally verified parameters for impedance modeling in human brains are lacking. This study seeks to address this need.Approach.We used FEM to simulate high-resolution single- and dual-electrode impedance measurements along linear electrode trajectories through (1) canonical gray and white matter tissue models, and (2) selected anatomic structures within whole-brain patient DTI-based models. We then compared intraoperative impedance measurements taken at known locations along deep brain stimulation (DBS) surgical trajectories with model predictions to evaluate model accuracy and refine model parameters.Main results.In DTI-FEM models, single- and dual-electrode configurations performed similarly. While only dual-electrode configurations were sensitive to white matter fiber orientation, other influences on impedance, such as white matter density, enabled single-electrode impedance measurements to display significant spatial variation even within purely white matter structures. We compared 308 intraoperative single-electrode impedance measurements in five DBS patients to DTI-FEM predictions at one-to-one corresponding locations. After calibration of model coefficients to these data, predicted impedances reliably estimated intraoperative measurements in all patients (R=0.784±0.116,n=5). Through this study, we derived an updated value for the slope coefficient of the DTI conductance model published by Tuchet al,k=0.0649 S⋅smm-3 (originalk=0.844), for use specifically in humans at physiological frequencies.Significance.This is the first study to compare impedance estimates from imaging-based models of human brain tissue to experimental measurements at the same locationsin vivo. Accurate, non-invasive, imaging-based impedance prediction has numerous applications in functional neurosurgery, including tissue mapping, intraoperative electrode localization, and DBS.

Phantom-Enhanced High Mechanical Accuracy for Frame-Based Deep Brain Stimulation

Deep brain stimulation (DBS) is a neurosurgical procedure that depends on high-accuracy targeting of structures to implant electrodes within the brain. The positioning of these electrodes in the brain determines the long-term efficacy of treating diseases such as Parkinson's disease, essential tremor, or dystonia. Misplaced electrodes in DBS can lead to poor efficacy and stimulation-induced side effects. Widespread targeting errors and variability have been published throughout the literature. As such, improvement in targeting accuracy is needed to enhance the quality of the procedures. A stereotactic phantom was utilized to test and adjust targeting before the surgical placement in the brain for 91 sequential electrodes. The tip of the microelectrode, the first rigid point in time, was measured and compared to the planned target. The technique utilized a to-target cannula with an XY stage that allowed x-axis and y-axis adjustments and correction for inaccuracies relative to the phantom. A calculation was developed to convert anatomical angles (sagittal and coronal) provided by commercial planning stations to spherical angles to calculate points along a trajectory. Error calculations included each dimensional axis, Euclidean error, and radial error. Bends in the cannula and microelectrode were observed and corrected by referencing the phantom. All 91 first-pass tracks traversed the intended target, and three electrodes required a second mapping track beyond the first penetration due to neurophysiological and intraoperative testing. The results showed overall ultra-high (0-0.5 mm) to high (>0.5-1 mm) accuracy, an average Euclidean error of 0.66±0.30 mm, and a radial error of 0.45±0.28 mm with dimensional errors of less than 0.5 mm per axis. The utilization of a stereotactic phantom is an important tool to enhance the stereotactic targeting before insertion into the brain. This phantom technique yielded ultra-high to high accuracy in error calculations. Future methods and studies should focus on error minimization to enhance these DBS mechanical accuracy and correlations with clinical outcomes.

STN localization using local field potentials based on wavelet packet features and stacking ensemble learning

BACKGROUND

DBS entails the insertion of an electrode into the patient brain, enabling Subthalamic nucleus (STN) stimulation. Accurate delineation of STN borders is a critical but time-consuming task, traditionally reliant on the neurosurgeon experience in deciphering the intricacies of microelectrode recording (MER). While clinical outcomes of MER have been satisfactory, they involve certain risks to patient safety. Recently, there has been a growing interest in exploring the potential of local field potentials (LFP) due to their correlation with the STN motor territory.

METHOD

A novel STN detection system, integrating LFP and wavelet packet transform (WPT) with stacking ensemble learning, is developed. Initial steps involve the inclusion of soft thresholding to increase robustness to LFP variability. Subsequently, non-linear WPT features are extracted. Finally, a unique ensemble model, comprising a dual-layer structure, is developed for STN localization. We harnessed the capabilities of support vector machine, Decision tree and k-Nearest Neighbor in conjunction with long short-term memory (LSTM) network. LSTM is pivotal for assigning adequate weights to every base model.

RESULTS

Results reveal that the proposed model achieved a remarkable accuracy and F1-score of 89.49% and 91.63%.

COMPARISON WITH EXISTING METHODS

Ensemble model demonstrated superior performance when compared to standalone base models and existing meta techniques.

CONCLUSION

This framework is envisioned to enhance the efficiency of DBS surgery and reduce the reliance on clinician experience for precise STN detection. This achievement is strategically significant to serve as an invaluable tool for refining the electrode trajectory, potentially replacing the current methodology based on MER.

Interleaved Propofol-Ketamine Maintains DBS Physiology and Hemodynamic Stability: A Double-Blind Randomized Controlled Trial

BACKGROUND

The gold standard anesthesia for deep brain stimulation (DBS) surgery is the "awake" approach, using local anesthesia alone. Although it offers high-quality microelectrode recordings and therapeutic-window assessment, it potentially causes patients extreme stress and might result in suboptimal surgical outcomes. General anesthesia or deep sedation is an alternative, but may reduce physiological testing reliability and lead localization accuracy.

OBJECTIVES

The aim is to investigate a novel anesthesia regimen of ketamine-induced conscious sedation for the physiological testing phase of DBS surgery.

METHODS

Parkinson's patients undergoing subthalamic DBS surgery were randomly divided into experimental and control groups. During physiological testing, the groups received 0.25 mg/kg/h ketamine infusion and normal saline, respectively. Both groups had moderate propofol sedation before and after physiological testing. The primary outcome was recording quality. Secondary outcomes included hemodynamic stability, lead accuracy, motor and cognitive outcome, patient satisfaction, and adverse events.

RESULTS

Thirty patients, 15 from each group, were included. Intraoperatively, the electrophysiological signature and lead localization were similar under ketamine and saline. Tremor amplitude was slightly lower under ketamine. Postoperatively, patients in the ketamine group reported significantly higher satisfaction with anesthesia. The improvement in Unified Parkinson's disease rating scale part-III was similar between the groups. No negative effects of ketamine on hemodynamic stability or cognition were reported perioperatively.

CONCLUSIONS

Ketamine-induced conscious sedation provided high quality microelectrode recordings comparable with awake conditions. Additionally, it seems to allow superior patient satisfaction and hemodynamic stability, while maintaining similar post-operative outcomes. Therefore, it holds promise as a novel alternative anesthetic regimen for DBS. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Neuroimaging of Parkinson's disease by quantitative susceptibility mapping

Parkinson's disease (PD) is a common neurodegenerative disease, and apart from a few rare genetic causes, its pathogenesis remains largely unclear. Recent scientific interest has been captured by the involvement of iron biochemistry and the disruption of iron homeostasis, particularly within the brain regions specifically affected in PD. The advent of Quantitative Susceptibility Mapping (QSM) has enabled non-invasive quantification of brain iron in vivo by MRI, which has contributed to the understanding of iron-associated pathogenesis and has the potential for the development of iron-based biomarkers in PD. This review elucidates the biochemical underpinnings of brain iron accumulation, details advancements in iron-sensitive MRI technologies, and discusses the role of QSM as a biomarker of iron deposition in PD. Despite considerable progress, several challenges impede its clinical application after a decade of QSM studies. The initiation of multi-site research is warranted for developing robust, interpretable, and disease-specific biomarkers for monitoring PD disease progression.

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.

Surgical Advances in Parkinson's Disease

While symptomatic pharmacological therapy remains the main therapeutic strategy for Parkinson's disease (PD), over the last two decades, surgical approaches have become more commonly used to control levodopa-induced motor complications and dopamine-resistant and non-motor symptoms of PD. In this paper, we discuss old and new surgical treatments for PD and the many technological innovations in this field. We have initially reviewed the relevant surgical anatomy as well as the pathological signaling considered to be the underlying cause of specific symptoms of PD. Subsequently, early attempts at surgical symptom control will be briefly reviewed. As the most well-known surgical intervention for PD is deep brain stimulation, this subject is discussed at length. As deciding on whether a patient stands to benefit from DBS can be quite difficult, the different proposed paradigms for precisely this are covered. Following this, the evidence regarding different targets, especially the subthalamic nucleus and internal globus pallidus, is reviewed as well as the evidence for newer proposed targets for specific symptoms. Due to the rapidly expanding nature of knowledge and technological capabilities, some of these new and potential future capabilities are given consideration in terms of their current and future use. Following this, we have reviewed newer treatment modalities, especially magnetic resonance-guided focused ultrasound and other potential surgical therapies, such as spinal cord stimulation for gait symptoms and others. As mentioned, the field of surgical alleviation of symptoms of PD is undergoing a rapid expansion, and this review provides a general overview of the current status and future directions in the field.

Mediation of Tremor Control by the Decussating and Nondecussating Part of the Dentato-Rubro-Thalamic Tract in Deep Brain Stimulation in Essential Tremor: Which Part Should Be Stimulated?

OBJECTIVES

The dentato-rubro-thalamic tract (DRTT) has been found to play a major role in the mechanisms of tremor alleviation by deep brain stimulation (DBS) in essential tremor (ET). Still, the influence of the two different parts of the DRTT, consisting of crossing and nondecussating fibers, is not yet clear with respect to tremor reduction. The aim of this study was to assess the influence of the crossing and the nondecussating part of the DRTT on tremor control in ET.

MATERIALS AND METHODS

We investigated 80 electrode contacts in ten patients with ET who received bilateral DBS of the Nucleus ventralis intermedius of the thalamus (VIM). Preoperatively and with patients under general anesthesia, 3T magnetic resonance imaging scans were performed, including Diffusion Tensor Imaging scans with 64 gradient directions. We calculated the course of the two parts of the DRTT based on a workflow for probabilistic fiber tracking including protocols for correction of susceptibility- and eddy current-induced distortions. Distances of electrode contacts were correlated with clinical data from neurologic single pole testing.

RESULTS

Voltage- and current-steered systems were analyzed separately. Regarding postural tremor, effective contacts showed significantly lower distances to both parts of the DRTT (crossing p < 0.001, nondecussating p < 0.05) in voltage-steered systems. Regarding intentional tremor, significant results were only found for the crossing part (p < 0.01). Regarding both tremor types, effective contacts were closer to the crossing part, unlike less effective contacts. Nonlinear regression analyses using a logistic model showed higher coefficients for the crossing part of the DRTT. Multivariate regression models including distances to both parts of the DRTT showed a significant influence of only the crossing part. Analysis of current-steered systems showed unstable data, probably because of the small number of analyzed patients.

CONCLUSIONS

Our data suggest an involvement of both parts of the DRTT in tremor reduction, indicating mediation of DBS effects by both fiber bundles, although the crossing part showed stronger correlations with good clinical responses. Nevertheless, special attention should be paid to methodologic aspects when using probabilistic tractography for patient-specific targeting to avoid uncertain and inaccurate results.

The Five-Factor Modified Frailty Index as a Predictor of Outcomes in Deep Brain Stimulation Surgery for Parkinson's Disease

Introduction Parkinson's disease (PD) is one of the most common neurodegenerative diseases worldwide. Though there are many pharmacological therapeutics approved today for PD, surgical interventions such as deep brain stimulation (DBS) have shown convincing symptom mitigation and minimal complication rates in aggregate. Recently, the concept of frailty - defined as reduced physiologic reserve and function affecting multiple systems throughout the patient - has gained traction as a predictor of short-term postoperative morbidity and mortality. As such, the Modified Frailty Index-5 (mFI-5) is a postoperative morbidity predictor based on five factors and has been used in neurosurgical subspecialties such as tumor, vascular, and spine. Yet, there is minimal literature assessing frailty in the field of functional neurosurgery. With the prevalence of DBS in PD, this study evaluated the mFI-5 as a predictor of postoperative complications in a selected patient population. Methods The American College of Surgeons National Surgical Quality Improvement Program 2010-2019 Database was queried for Current Procedural Terminology (CPT) codes, as well as the International Classification of Diseases (ICD)-9 and ICD-10 codes pertaining to DBS procedures in PD patients. Each patient was scored by the mFI-5 protocol and stratified into groups of No Frailty (mFI-5=0), Moderate Frailty (mFI-5=1), and Significant Frailty (mFI-5≥2). The No Frailty group was used as a reference in multivariate and univariate analyses of the groups. Results A total of 1,645 subjects were included in the study and were subcategorized into groups of No Frailty (N=877), Moderate Frailty (N=561), and Significant Frailty (N=207) based on their frailty scores. The subjects' mean age was 65.8±9.4 years. Overall, 1,161 (70.6%) were male, while 484 (29.4%) were female. With reference to the No Frailty group in multivariate analysis, patients with moderate frailty experienced greater unplanned readmission (OR 2.613, 95% CI 1.143-5.973, p=0.023), while those with significant frailty experienced greater unplanned readmission (OR 3.723, 95% CI 1.376-10.073, p=0.010), any readmission (OR 2.396, 95% CI 1.098-5.230, p=0.028), non-home discharge (OR 4.317, 95% CI 1.765-10.562, p<0.001), and complications in aggregate (OR 2.211, 95% CI 1.285-3.806, p=0.004). Conclusions Until now, the available clinical tools were limited in providing accurate predictions with minimal information for postoperative outcomes in DBS for PD patients. Our data give clinicians insight into the relationship between frailty and surgical outcomes and will assist physicians in preparing for postoperative care by predicting outcomes of significantly frail PD patients receiving DBS therapy.

Two-photon microendoscope for label-free imaging in stereotactic neurosurgery

We demonstrate a gradient refractive index (GRIN) microendoscope with an outer diameter of ∼1.2 mm and a length of ∼186 mm that can fit into a stereotactic surgical cannula. Two photon imaging at an excitation wavelength of 900 nm showed a field of view of ∼180 microns and a lateral and axial resolution of 0.86 microns and 9.6 microns respectively. The microendoscope was tested by imaging autofluorescence and second harmonic generation (SHG) in label-free human brain tissue. Furthermore, preliminary image analysis indicates that image classification models can predict if an image is from the subthalamic nucleus or the surrounding tissue using conventional, bench-top two-photon autofluorescence.

MER and increased operative time are not risk factors for the formation of pneumocephalus during DBS

Although only recently directional leads have proven their potential to compensate for sub-optimally placed electrodes, optimal lead positioning remains the most critical factor in determining Deep Brain Stimulation (DBS) outcome. Pneumocephalus is a recognized source of error, but the factors that contribute to its formation are still a matter of debate. Among these, operative time is one of the most controversial. Because cases of DBS performed with Microelectrode Recordings (MER) are affected by an increase in surgical length, it is useful to analyze whether MER places patients at risk for increased intracranial air entry. Data of 94 patients from two different institutes who underwent DBS for different neurologic and psychiatric conditions were analyzed for the presence of postoperative pneumocephalus. Operative time and use of MER, as well as other potential risk factors for pneumocephalus (age, awake vs. asleep surgery, number of MER passages, burr hole size, target and unilateral vs. bilateral implants) were examined. Mann-Whitney U and Kruskal-Wallis tests were utilized to compare intracranial air distributions across groups of categorical variables. Partial correlations were used to assess the association between time and volume. A generalized linear model was created to predict the effects of time and MER on the volume of intracranial air, controlling for other potential risk factors identified: age, number of MER passages, awake vs. asleep surgery, burr hole size, target, unilateral vs. bilateral surgery. Significantly different distributions of air volume were noted between different targets, unilateral vs. bilateral implants, and number of MER trajectories. Patients undergoing DBS with MER did not present a significant increase in pneumocephalus compared to patients operated without (p = 0.067). No significant correlation was found between pneumocephalus and time. Using multivariate analysis, unilateral implants exhibited lower volumes of pneumocephalus (p = 0.002). Two specific targets exhibited significantly different volumes of pneumocephalus: the bed nucleus of the stria terminalis with lower volumes (p < 0.001) and the posterior hypothalamus with higher volumes (p = 0.011). MER, time, and other parameters analyzed failed to reach statistical significance. Operative time and use of intraoperative MER are not significant predictors of pneumocephalus during DBS. Air entry is greater for bilateral surgeries and may be also influenced by the specific stimulated target.

Accuracy, precision, and safety of stereotactic, frame-based, intraoperative MRI-guided and MRI-verified deep brain stimulation in 650 consecutive procedures

OBJECTIVE

Suboptimal lead placement is one of the most common indications for deep brain stimulation (DBS) revision procedures. Confirming lead placement in relation to the visible anatomical target with dedicated stereotactic imaging before terminating the procedure can mitigate this risk. In this study, the authors examined the accuracy, precision, and safety of intraoperative MRI (iMRI) to both guide and verify lead placement during frame-based stereotactic surgery.

METHODS

A retrospective analysis of 650 consecutive DBS procedures for targeting accuracy, precision, and perioperative complications was performed. Frame-based lead placement took place in an operating room equipped with an MRI machine using stereotactic images to verify lead placement before removing the stereotactic frame. Immediate lead relocation was performed when necessary. Systematic analysis of the targeting error was calculated.

RESULTS

Verification of 1201 DBS leads with stereotactic MRI was performed in 643 procedures and with stereotactic CT in 7. The mean ± SD of the final targeting error was 0.9 ± 0.3 mm (range 0.1-2.3 mm). Anatomically acceptable lead placement was achieved with a single brain pass for 97% (n = 1164) of leads; immediate intraoperative relocation was performed in 37 leads (3%) to obtain satisfactory anatomical placement. General anesthesia was used in 91% (n = 593) of the procedures. Hemorrhage was noted after 4 procedures (0.6%); 3 patients (0.4% of procedures) presented with transient neurological symptoms, and 1 experienced delayed cognitive decline. Two bleeds coincided with immediate relocation (2 of 37 leads, 5.4%), which contrasts with hemorrhage in 2 (0.2%) of 1164 leads implanted on the first pass (p = 0.0058). Three patients had transient seizures in the postoperative period. The seizures coincided with hemorrhage in 2 of these patients and with immediate lead relocation in the other. There were 21 infections (3.2% of procedures, 1.5% in 3 months) leading to hardware removal. Delayed (> 3 months) retargeting of 6 leads (0.5%) in 4 patients (0.6% of procedures) was performed because of suboptimal stimulation benefit. There were no MRI-related complications, no permanent motor deficits, and no deaths.

CONCLUSIONS

To the authors' knowledge, this is the largest series reporting the use of iMRI to guide and verify lead location during DBS surgery. It demonstrates a high level of accuracy, precision, and safety. Significantly higher hemorrhage was encountered when multiple brain passes were required for lead implantation, although none led to permanent deficit. Meticulous audit and calibration can improve precision and maximize safety.

Magnetic Resonance-Guided focused ultrasound surgery for Parkinson's disease: A mini-review and comparison between deep brain stimulation

Magnetic resonance-guided focused ultrasound (MRgFUS) is a new surgical treatment for Parkinson's disease (PD). Previous experience with radiofrequency lesionectomy and deep brain stimulation (DBS) has identified several candidate targets for MRgFUS intended to alleviate the motor symptoms of PD. The main advantage of MRgFUS is that it is incisionless. MRgFUS has certain limitations and is associated with adverse effects. The present study reviews the literature on conventional surgical interventions for PD, discusses recent studies on MRgFUS, and the comparison between DBS and MRgFUS for PD. The reviews aims to provide an essential reference for neurologists to select the appropriate treatments for patients with PD.

Interactive mobile application for Parkinson's disease deep brain stimulation (MAP DBS): An open-label, multicenter, randomized, controlled clinical trial

INTRODUCTION

Deep brain stimulation (DBS) is an effective treatment for Parkinson's disease (PD), but its efficacy is tied to DBS programming, which is often time consuming and burdensome for patients, caregivers, and clinicians. Our aim is to test whether the Mobile Application for PD DBS (MAP DBS), a clinical decision support system, can improve programming.

METHODS

We conducted an open-label, 1:1 randomized, controlled, multicenter clinical trial comparing six months of SOC standard of care (SOC) to six months of MAP DBS-aided programming. We enrolled patients between 30 and 80 years old who received DBS to treat idiopathic PD at six expert centers across the United States. The primary outcome was time spent DBS programming and secondary outcomes measured changes in motor symptoms, caregiver strain and medication requirements.

RESULTS

We found a significant reduction in initial visit time (SOC: 43.8 ± 28.9 min n = 37, MAP DBS: 27.4 ± 13.0 min n = 35, p = 0.001). We did not find a significant difference in total programming time between the groups over the 6-month study duration. MAP DBS-aided patients experienced a significantly larger reduction in UPDRS III on-medication scores (-7.0 ± 7.9) compared to SOC (-2.7 ± 6.9, p = 0.01) at six months.

CONCLUSION

MAP DBS was well tolerated and improves key aspects of DBS programming time and clinical efficacy.

Complications Related to Deep Brain Stimulation Lead Implantation: A Single-Surgeon Case Series

BACKGROUND

Deep brain stimulation (DBS) is the mainstay of surgical treatment for movement disorders, yet previous studies have shown widely varying complication rates. Given the elective nature of DBS surgery, minimizing surgical complications is imperative.

OBJECTIVE

To evaluate short-term and long-term complications related to DBS lead implantation surgeries performed by an experienced surgeon and provide an updated benchmark comparison for other DBS centers and alternative therapies.

METHODS

A retrospective chart review of patients who underwent DBS lead implantation surgery by a single surgeon at our institution between 2012 and 2020 was conducted. Demographic and clinical data including surgical complications were collected. A Kaplan-Meier survival analysis was used to evaluate the cumulative risk of lead revision or removal over time. Associations between patient characteristics and various complications were evaluated.

RESULTS

Four hundred fifty-one DBS leads were placed in 255 patients. Thirteen leads and 11 patients required revision. In total, 3.6% (95% CI [1.3%-5.9%]) of patients required revision at 1 year and 4.8% (95% CI [1.9%-7.6%]) at 5 years, with per-lead revision rates of 2.3% (95% CI [0.9%-3.6%]) and 3.3% (95% CI [1.5%-5.1%]), respectively. Less common diagnoses such as Tourette syndrome, post-traumatic tremor, and cluster headache trended toward association with lead revision or removal.

CONCLUSION

DBS performed by an experienced surgeon is associated with extremely low complication rates.

Localization of deep brain stimulation trajectories via automatic mapping of microelectrode recordings to MRI

Objective. Suboptimal electrode placement during subthalamic nucleus deep brain stimulation (STN DBS) surgery may arise from several sources, including frame-based targeting errors and intraoperative brain shift. We present a computer algorithm that can accurately localize intraoperative microelectrode recording (MER) tracks on preoperative magnetic resonance imaging (MRI) in real-time, thereby predicting deviation between the surgical plan and the MER trajectories.Approach. Random forest (RF) modeling was used to derive a statistical relationship between electrophysiological features on intraoperative MER and voxel intensity on preoperative T2-weighted MR imaging. This model was integrated into a larger algorithm that can automatically localize intraoperative MER recording tracks on preoperative MRI in real-time. To verify accuracy, targeting error of both the planned intraoperative trajectory ('planned') and the algorithm-derived trajectory ('calculated') was estimated by measuring deviation from the final DBS lead location on postoperative high-resolution computed tomography ('actual').Main results. MR imaging and MERs were obtained from 24 STN DBS implant trajectories. The cross-validated RF model could accurately distinguish between gray and white matter regions along MER trajectories (AUC 0.84). When applying this model within the localization algorithm, thecalculatedMER trajectory estimate was found to be significantly closer to theactualDBS lead when compared to theplannedtrajectory recorded during surgery (1.04 mm vs 1.52 mm deviation,p< 0.002), with improvement shown in 19/24 cases (79%). When applying the algorithm to simulated DBS trajectory plans with randomized targeting error, up to 4 mm of error could be resolved to <2 mm on average (p< 0.0001).Significance. This work presents an automated system for intraoperative localization of electrodes during STN DBS surgery. This neuroengineering solution may enhance the accuracy of electrode position estimation, particularly in cases where high-resolution intraoperative imaging is not available.

A Retrospective Cohort Study of Implantable Pulse Generator Surgical Site Infections After Deep Brain Stimulation Surgery With an Antibacterial Envelope

INTRODUCTION

Deep brain stimulation (DBS) surgery is an established treatment for many patients with neurologic disease, and a common complication of DBS is surgical site infection (SSI). In 2016, neurosurgeons at our institution began enclosing implantable pulse generators (IPGs) within fully absorbable, antibacterial envelopes in patients who underwent initial DBS implantation. We sought to determine whether the use of antibacterial envelopes reduced IPG-related SSIs.

MATERIALS AND METHODS

We performed a retrospective chart review of all adult patients who underwent initial DBS implantation at Stanford Hospital between November 14, 2012, and November 9, 2020. Operative details, perioperative antibiotics, comorbidities, and postoperative complications were extracted for all patients. Univariate and multivariate logistic regression were used to identify factors associated with SSIs within three months of surgery, and interrupted time-series analysis was performed to assess whether the departmental adoption of the antibacterial envelope led to a reduction in IPG SSIs.

RESULTS

Of 344 patients who underwent initial IPG implantation with the antibacterial envelope, one developed an SSI within three months of surgery (0.3%), compared with six of 204 patients (2.9%) who underwent the same procedure without the antibacterial envelope (odds ratio: 0.10, 95% CI: 0.01-0.80, p = 0.031). Univariate logistic regression revealed that the antibacterial envelope and 2000-mg intravenous cefazolin perioperatively were associated with reduced SSI risk, whereas no other factors reached statistical significance. After adjusting for comorbidities, no association remained statistically significant. Interrupted time-series analysis showed a reduction in SSIs after 2016, but the effect was not significant.

CONCLUSIONS

The adoption of antibacterial envelopes was found to reduce IPG SSIs at the univariate level, but this association did not remain significant after controlling for confounding variables including perioperative antibiotic administration. Although encouraging, this study does not conclusively establish that the use of antibacterial pouches in patients who underwent initial DBS implantation reduces the incidence of IPG SSIs. Future prospective studies that control for confounding variables are necessary to determine the efficacy of antibacterial envelopes in reducing post-DBS infections at the IPG site before clear recommendations can be made.

Off-time Treatment Options for Parkinson's Disease

Motor fluctuations (MF) are deemed by patients with Parkinson's disease (PD) as the most troublesome disease feature resulting from the increasing impairment in responsiveness to dopaminergic drug treatments. MF are characterized by the loss of a stable response to levodopa over the nychthemeron with the reappearance of motor (and non-motor) parkinsonian clinical signs at various moments during the day and night. They normally appear after a few years of levodopa treatment and with a variable, though overall increasing severity, over the disease course. The armamentarium of first-line treatment options has widened in the last decade with new once-a-daily compounds, including a catechol O-methyltransferase inhibitor - Opicapone-, two MAO-B inhibitors plus channel blocker - Zonisamide and Safinamide and one amantadine extended-release formulation - ADS5012. In addition to apomorphine injection or oral levodopa dispersible tablets, which have been available for a long time, new on-demand therapies such as apomorphine sublingual or levodopa inhaled formulations have recently shown efficacy as rescue therapies for Off-time treatment. When the management of MF becomes difficult in spite of oral/on-demand options, more complex therapies should be considered, including surgical, i.e. deep brain stimulation, or device-aided therapies with pump systems delivering continuous subcutaneous or intestinal levodopa or subcutaneous apomorphine formulation. Older and less commonly used ablative techniques (radiofrequency pallidotomy) may also be effective while there is still scarce data regarding Off-time reduction using a new lesional approach, i.e. magnetic resonance-guided focused ultrasound. The choice between the different advanced therapies options is a shared decision that should consider physician opinion on contraindication/main target symptom, patients' preference, caregiver's availability together with public health systems and socio-economic environment. The choice of the right/first add-on treatment is still a matter of debate as well as the proper time for an advanced therapy to be considered. In this narrative review, we discuss all the above cited aspects of MF in patients with PD, including their phenomenology, management, by means of pharmacological and advanced therapies, on-going clinical trials and future research and treatment perspectives.

Microscale multicircuit brain stimulation: Achieving real-time brain state control for novel applications

Neurological and psychiatric disorders typically result from dysfunction across multiple neural circuits. Most of these disorders lack a satisfactory neuromodulation treatment. However, deep brain stimulation (DBS) has been successful in a limited number of disorders; DBS typically targets one or two brain areas with single contacts on relatively large electrodes, allowing for only coarse modulation of circuit function. Because of the dysfunction in distributed neural circuits - each requiring fine, tailored modulation - that characterizes most neuropsychiatric disorders, this approach holds limited promise. To develop the next generation of neuromodulation therapies, we will have to achieve fine-grained, closed-loop control over multiple neural circuits. Recent work has demonstrated spatial and frequency selectivity using microstimulation with many small, closely-spaced contacts, mimicking endogenous neural dynamics. Using custom electrode design and stimulation parameters, it should be possible to achieve bidirectional control over behavioral outcomes, such as increasing or decreasing arousal during central thalamic stimulation. Here, we discuss one possible approach, which we term microscale multicircuit brain stimulation (MMBS). We discuss how machine learning leverages behavioral and neural data to find optimal stimulation parameters across multiple contacts, to drive the brain towards desired states associated with behavioral goals. We expound a mathematical framework for MMBS, where behavioral and neural responses adjust the model in real-time, allowing us to adjust stimulation in real-time. These technologies will be critical to the development of the next generation of neurostimulation therapies, which will allow us to treat problems like disorders of consciousness and cognition.

Application of the robot-assisted implantation in deep brain stimulation

INTRODUCTION

This work aims to assess the accuracy of robotic assistance guided by a videometric tracker in deep brain stimulation (DBS).

METHODS

We retrospectively reviewed a total of 30 DBS electrode implantations, assisted by the Remebot robotic system, with a novel frameless videometric registration workflow. Then we selected 30 PD patients who used stereotactic frame surgery to implant electrodes during the same period. For each electrode, accuracy was assessed using radial and axial error.

RESULTS

The average radial error of the robot-assisted electrode implantation was 1.28 ± 0.36 mm, and the average axial error was 1.20 ± 0.40 mm. No deaths or associated hemorrhages, infections or poor incision healing occurred.

CONCLUSION

Robot-assisted implantation guided by a videometric tracker is accurate and safe.

Deep brain stimulation for Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative illness with both motor and nonmotor symptoms. Deep brain stimulation (DBS) is an established safe neurosurgical symptomatic therapy for eligible patients with advanced disease in whom medical treatment fails to provide adequate symptom control and good quality of life, or in whom dopaminergic medications induce severe side effects such as dyskinesias. DBS can be tailored to the patient's symptoms and targeted to various nodes along the basal ganglia-thalamus circuitry, which mediates the various symptoms of the illness; DBS in the thalamus is most efficient for tremors, and DBS in the pallidum most efficient for rigidity and dyskinesias, whereas DBS in the subthalamic nucleus (STN) can treat both tremors, akinesia, rigidity and dyskinesias, and allows for decrease in doses of medications even in patients with advanced stages of the disease, which makes it the preferred target for DBS. However, DBS in the STN assumes that the patient is not too old, with no cognitive decline or relevant depression, and does not exhibit severe and medically resistant axial symptoms such as balance and gait disturbances, and falls. Dysarthria is the most common side effect of DBS, regardless of the brain target. DBS has a long-lasting effect on appendicular symptoms, but with progression of disease, nondopaminergic axial features become less responsive to DBS. DBS for PD is highly specialised; to enable adequate selection and follow-up of patients, DBS requires dedicated multidisciplinary teams of movement disorder neurologists, functional neurosurgeons, specialised DBS nurses and neuropsychologists.

A computational roadmap to electronic drugs

A growing number of complex neurostimulation strategies promise symptom relief and functional recovery for several neurological, psychiatric, and even multi-organ disorders. Although pharmacological interventions are currently the mainstay of treatment, neurostimulation offers a potentially effective and safe alternative, capable of providing rapid adjustment to short-term variation and long-term decline of physiological functions. However, rapid advances made by clinical studies have often preceded the fundamental understanding of mechanisms underlying the interactions between stimulation and the nervous system. In turn, therapy design and verification are largely driven by clinical-empirical evidence. Even with titanic efforts and budgets, it is infeasible to comprehensively explore the multi-dimensional optimization space of neurostimulation through empirical research alone, especially since anatomical structures and thus outcomes vary dramatically between patients. Instead, we believe that the future of neurostimulation strongly depends on personalizable computational tools, i.e. Digital Neuro Twins (DNTs) to efficiently identify effective and safe stimulation parameters. DNTs have the potential to accelerate scientific discovery and hypothesis-driven engineering, and aid as a critical regulatory and clinical decision support tool. We outline here how DNTs will pave the way toward effective, cost-, time-, and risk-limited electronic drugs with a broad application bandwidth.

Robot-Assisted Deep Brain Stimulation: High Accuracy and Streamlined Workflow

BACKGROUND

A number of stereotactic platforms are available for performing deep brain stimulation (DBS) lead implantation. Robot-assisted stereotaxy has emerged more recently demonstrating comparable accuracy and shorter operating room times compared with conventional frame-based systems.

OBJECTIVE

To compare the accuracy of our streamlined robotic DBS workflow with data in the literature from frame-based and frameless systems.

METHODS

We retrospectively reviewed 126 consecutive DBS lead placement procedures using a robotic stereotactic platform. Indications included Parkinson disease (n = 94), essential tremor (n = 21), obsessive compulsive disorder (n = 7), and dystonia (n = 4). Procedures were performed using a stereotactic frame for fixation and the frame pins as skull fiducials for robot registration. We used intraoperative fluoroscopic computed tomography for registration and postplacement verification.

RESULTS

The mean radial error for the target point was 1.06 mm (SD: 0.55 mm, range 0.04-2.80 mm) on intraoperative fluoroscopic computed tomography. The mean operative time for an asleep, bilateral implant without implantable pulse generator placement was 238 minutes (SD: 52 minutes), and skin-to-skin procedure time was 116 minutes (SD: 42 minutes).

CONCLUSION

We describe a streamlined workflow for DBS lead placement using robot-assisted stereotaxy with a comparable accuracy profile. Obviating the need for checking and switching coordinates, as is standard for frame-based DBS, also reduces the chance for human error and facilitates training.

Motor evoked potentials versus Macrostimulation in predicting the postoperative motor threshold in STN Deep brain stimulation

INTRODUCTION

Accuracy is crucial in Deep Brain Stimulation (DBS). Electrophysiological and image-based techniques are used to avoid suboptimal positioning. Macrostimulation is the gold standard to delineate the therapeutic window intraoperatively. Despite this, electrode revision rates due to malpositioning are as high as 17%. The goal was to compare motor evoked potentials (MEPs) with the gold standard of Macrostimulation. We assessed accuracy and precision as well as the correlation in predicting motor side effects at the initial mapping 4 weeks postoperatively.

METHODS

In this prospective study intraoperative MEPs from 94 contacts in 16 patients undergoing STN DBS under local anesthesia were correlated to the postoperative threshold for stimulation-induced motor side effects and compared to intraoperative Macrostimulation. Analysis of accuracy, precision and correlation (Pearson) was performed.

RESULTS

MEPs of the upper extremity had a mean percentage error of 25% (SD 38.8%) and correlated significantly with the motor threshold at postoperative mapping (R=0.235). Macrostimulation was less accurate and precise with a mean percentage error of - 68% (SD 78.8%) but had a higher correlation (R=0.388). MEPs rarely (3%) overestimated the threshold by maximally 1 mA. In contrast, Macrostimulation overestimated the threshold by over 1 mA in 69% leading to a false sense of security.

CONCLUSION

MEPs are feasible in an awake setting during Deep Brain Stimulation in the STN for PD patients. MEPs of the upper extremity are more accurate and precise predicting the motor threshold and avoid a false sense of security in comparison to the gold standard of Macrostimulation.

Clinically-derived oscillatory biomarker predicts optimal subthalamic stimulation for Parkinson's disease

OBJECTIVE

Choosing the optimal electrode trajectory, stimulation location, and stimulation amplitude in subthalamic nucleus deep brain stimulation (STN DBS) for Parkinson's disease (PD) remains a time-consuming empirical effort. In this retrospective study, we derive a data-driven electrophysiological biomarker that predicts clinical DBS location and parameters, and we consolidate this information into a quantitative score that may facilitate an objective approach to STN DBS surgery and programming.

APPROACH

Random-forest feature selection was applied to a dataset of 1046 microelectrode recordings sites across 20 DBS implant trajectories to identify features of oscillatory activity that predict clinically programmed volumes of tissue activation (VTA). A cross-validated classifier was used to retrospectively predict VTA regions from these features. Spatial convolution of probabilistic classifier outputs along MER trajectories produced a biomarker score that reflects the probability of localization within a clinically optimized VTA.

MAIN RESULTS

Biomarker scores peaked within the VTA region and were significantly correlated with percent improvement in postoperative motor symptoms (MDS-UPRDS Part III, R = 0.61, p = 0.004). Notably, the length of STN, a common criterion for trajectory selection, did not show similar correlation (R = -0.31, p = 0.18). These findings suggest that biomarker-based trajectory selection and programming may improve motor outcomes by 9 ± 3 percentage points (p = 0.047) in this dataset.

SIGNIFICANCE

A clinically defined electrophysiological biomarker not only predicts VTA size and location but also correlates well with motor outcomes. Use of this biomarker for trajectory selection and initial stimulation may potentially simplify STN DBS surgery and programming.

Strength-frequency curve for micromagnetic neurostimulation through excitatory postsynaptic potentials (EPSPs) on rat hippocampal neurons and numerical modeling of magnetic microcoil (μcoil)

OBJECTIVE

The objective of this study was to measure the effect of micromagnetic stimulation (μMS) on hippocampal neurons, by using single microcoil (μcoil) prototype, Magnetic Pen (MagPen). MagPen will be used to stimulate the CA3 magnetically and excitatory post synaptic potential (EPSP) measurements will be made from the CA1. The threshold for μMS as a function of stimulation frequency of the current driving the µcoil will be demonstrated. Finally, the optimal stimulation frequency of the current driving the μcoil to minimize power will be estimated.

APPROACH

A biocompatible prototype, MagPen was built, and customized such that it is easy to adjust the orientation of the μcoil over the hippocampal tissue in an in vitro setting. Finite element modeling (FEM) of the μcoil was performed to estimate the spatial profiles of the magnetic flux density (in T) and the induced electric fields (in V/m). The induced electric field profiles generated at different values of current applied to the µcoil whether can elicit a neuron response was validated by numerical modeling. The modeling settings were replicated in experiments on rat hippocampal neurons.

MAIN RESULTS

The preferred orientation of MagPen over the Schaffer Collateral fibers was demonstrated such that they elicit a neuron response. The recorded EPSPs from CA1 due to μMS at CA3 were validated by applying tetrodotoxin (TTX). Finally, it was interpreted through numerical analysis that increasing frequency of the current driving the μcoil, led to a decrease in the current amplitude threshold for μMS.

SIGNIFICANCE

This work reports that μMS can be used to evoke population EPSPs in the CA1 of hippocampus. It demonstrates the strength-frequency curve for µMS and its unique features related to orientation dependence of the µcoils, spatial selectivity and distance dependence. Finally, the challenges related to µMS experiments were studied including ways to overcome them.

The Role of Microelectrode Recording and Stereotactic Computed Tomography in Verifying Lead Placement During Awake MRI-Guided Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease

BACKGROUND

Bilateral deep brain stimulation of the subthalamic nucleus (STN-DBS) has become a cornerstone in the advanced treatment of Parkinson's disease (PD). Despite its well-established clinical benefit, there is a significant variation in the way surgery is performed. Most centers operate with the patient awake to allow for microelectrode recording (MER) and intraoperative clinical testing. However, technical advances in MR imaging and MRI-guided surgery raise the question whether MER and intraoperative clinical testing still have added value in DBS-surgery.

OBJECTIVE

To evaluate the added value of MER and intraoperative clinical testing to determine final lead position in awake MRI-guided and stereotactic CT-verified STN-DBS surgery for PD.

METHODS

29 consecutive patients were analyzed retrospectively. Patients underwent awake bilateral STN-DBS with MER and intraoperative clinical testing. The role of MER and clinical testing in determining final lead position was evaluated. Furthermore, interobserver variability in determining the MRI-defined STN along the planned trajectory was investigated. Clinical improvement was evaluated at 12 months follow-up and adverse events were recorded.

RESULTS

98% of final leads were placed in the central MER-track with an accuracy of 0.88±0.45 mm. Interobserver variability of the MRI-defined STN was 0.84±0.09. Compared to baseline, mean improvement in MDS-UPDRS-III, PDQ-39 and LEDD were 26.7±16.0 points (54%) (p < 0.001), 9.0±20.0 points (19%) (p = 0.025), and 794±434 mg/day (59%) (p < 0.001) respectively. There were 19 adverse events in 11 patients, one of which (lead malposition requiring immediate postoperative revision) was a serious adverse event.

CONCLUSION

MER and intraoperative clinical testing had no additional value in determining final lead position. These results changed our daily clinical practice to an asleep MRI-guided and stereotactic CT-verified approach.

Increased variance in second electrode accuracy during deep brain stimulation and its relationship to pneumocephalus, brain shift, and clinical outcomes: A retrospective cohort study

•

Overall electrode accuracy was 0.22+/-0.4 ​mm with only 3 (4%) electrodes out with 2 ​mm from the intended target.

•

Accuracy was significantly worse in the GPi versus the STN and on the second side implanted.

•

Inaccuracy occurred in the X (lateral) plane but was not related to pneumocephalus or brain shift.

Reduced Risk of Reoperations With Modern Deep Brain Stimulator Systems: Big Data Analysis From a United States Claims Database

Objective: There have been significant improvements in the design and manufacturing of deep brain stimulation (DBS) systems, but no study has considered the impact of modern systems on complications. We sought to compare the relative occurrence of reoperations after de novo implantation of modern and traditional DBS systems in patients with Parkinson's disease (PD) or essential tremor (ET) in the United States.

Design: Retrospective, contemporaneous cohort study.

Setting: Multicenter data from the United States Centers for Medicare and Medicaid Services administrative claims database between 2016 and 2018.

Participants: This population-based sample consisted of 5,998 patients implanted with a DBS system, of which 3,869 patients had a de novo implant and primary diagnosis of PD or ET. Follow-up of 3 months was available for 3,810 patients, 12 months for 3,561 patients, and 24 months for 1,812 patients.

Intervention: Implantation of a modern directional (MD) or traditional omnidirectional (TO) DBS system.

Primary and Secondary Outcome Measures: We hypothesized that MD systems would impact complication rates. Reoperation rate was the primary outcome. Associated diagnoses, patient characteristics, and implanting center details served as covariates. Kaplan–Meier analysis was performed to compare rates of event-free survival and regression models were used to determine covariate influences.

Results: Patients implanted with modern systems were 36% less likely to require reoperation, largely due to differences in acute reoperations and intracranial lead reoperations. Risk reduction persisted while accounting for practice differences and implanting center experience. Risk reduction was more pronounced in patients with PD.

Conclusions: In the first multicenter analysis of device-related complications including modern DBS systems, we found that modern systems are associated with lower reoperation rates. This risk profile should be carefully considered during device selection for patients undergoing DBS for PD or ET. Prospective studies are needed to further investigate underlying causes.

Clinical applications of magnetic resonance imaging based functional and structural connectivity

Advances in computational neuroimaging techniques have expanded the armamentarium of imaging tools available for clinical applications in clinical neuroscience. Non-invasive, in vivo brain MRI structural and functional network mapping has been used to identify therapeutic targets, define eloquent brain regions to preserve, and gain insight into pathological processes and treatments as well as prognostic biomarkers. These tools have the real potential to inform patient-specific treatment strategies. Nevertheless, a realistic appraisal of clinical utility is needed that balances the growing excitement and interest in the field with important limitations associated with these techniques. Quality of the raw data, minutiae of the processing methodology, and the statistical models applied can all impact on the results and their interpretation. A lack of standardization in data acquisition and processing has also resulted in issues with reproducibility. This limitation has had a direct impact on the reliability of these tools and ultimately, confidence in their clinical use. Advances in MRI technology and computational power as well as automation and standardization of processing methods, including machine learning approaches, may help address some of these issues and make these tools more reliable in clinical use. In this review, we will highlight the current clinical uses of MRI connectomics in the diagnosis and treatment of neurological disorders; balancing emerging applications and technologies with limitations of connectivity analytic approaches to present an encompassing and appropriate perspective.

[Deep brain stimulation of the subthalamic nucleus for parkinson's disease: awake vs asleep]

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is known to be an effective and safe neurosurgical procedure for Parkinson's disease (PD). Traditionally, awake implantation of stimulation system is carried out using microelectrode registration and intraoperative stimulation. Development of neuroimaging technologies enables direct STN imaging. Therefore, asleep surgery without additional intraoperative verification is possible. This approach reduces surgery time and can potentially decrease the incidence of hemorrhagic and infectious complications. The advantages of one method or another are being discussed.

OBJECTIVE

To assess the benefits and limitations of various methods for DBS system implantation for bilateral STN stimulation, to study the issues of stereotaxic accuracy, efficiency and safety of asleep and awake electrode implantation into STN.

MATERIAL AND METHODS

We reviewed the articles published in the PubMed database. Searching algorithm included the following keywords: «asleep DBS», «Parkinson's disease», «subthalamic nucleus», «3T MRI», «SWI», «SWAN».

RESULTS

There were 31 articles devoted to asleep DBS of STN including 4 meta-analyses, 3 prospective controlled studies, 13 retrospective controlled studies and 11 studies without a control group.

CONCLUSION

Asleep implantation of electrodes for DBS of STN can be performed only after a clear imaging of STN boundaries with high-quality MRI.

Next generation material interfaces for neural engineering

Neural implant technology is rapidly progressing, and gaining broad interest in research fields such as electrical engineering, materials science, neurobiology, and data science. As the potential applications of neural devices have increased, new technologies to make neural intervention longer-lasting and less invasive have brought attention to neural interface engineering. This review will focus on recent developments in materials for neural implants, highlighting new technologies in the fields of soft electrodes, mechanical and chemical engineering of interface coatings, and remotely powered devices. In this context, novel implantation strategies, manufacturing methods, and combinatorial device functions will also be discussed.

Neuroanatomical considerations for optimizing thalamic deep brain stimulation in Tourette syndrome

OBJECTIVE

Deep brain stimulation (DBS) of the centromedian thalamic nucleus has been reportedly used to treat severe Tourette syndrome, yielding promising outcomes. However, it remains unclear how DBS electrode position and stimulation parameters modulate the specific area and related networks. The authors aimed to evaluate the relationships between the anatomical location of stimulation fields and clinical responses, including therapeutic and side effects.

METHODS

The authors collected data from 8 patients with Tourette syndrome who were treated with DBS. The authors selected the active contact following threshold tests of acute side effects and gradually increased the stimulation intensity within the therapeutic window such that acute and chronic side effects could be avoided at each programming session. The patients were carefully interviewed, and stimulation-induced side effects were recorded. Clinical outcomes were evaluated using the Yale Global Tic Severity Scale, the Yale-Brown Obsessive-Compulsive Scale, and the Hamilton Depression Rating Scale. The DBS lead location was evaluated in the normalized brain space by using a 3D atlas. The volume of tissue activated was determined, and the associated normative connective analyses were performed to link the stimulation field with the therapeutic and side effects.

RESULTS

The mean follow-up period was 10.9 ± 3.9 months. All clinical scales showed significant improvement. Whereas the volume of tissue activated associated with therapeutic effects covers the centromedian and ventrolateral nuclei and showed an association with motor networks, those associated with paresthesia and dizziness were associated with stimulation of the ventralis caudalis and red nucleus, respectively. Depressed mood was associated with the spread of stimulation current to the mediodorsal nucleus and showed an association with limbic networks.

CONCLUSIONS

This study addresses the importance of accurate implantation of DBS electrodes for obtaining standardized clinical outcomes and suggests that meticulous programming with careful monitoring of clinical symptoms may improve outcomes.