Surgical implantation of STN-DBS leads using intraoperative MRI guidance: technique, accuracy, and clinical benefit at 1-year follow-up

Optimizing neuroscience data management by combining REDCap, BIDS and SQLite: a case study in Deep Brain Stimulation

Neuroscience studies entail the generation of massive collections of heterogeneous data (e.g. demographics, clinical records, medical images). Integration and analysis of such data in research centers is pivotal for elucidating disease mechanisms and improving clinical outcomes. However, data collection in clinics often relies on non-standardized methods, such as paper-based documentation. Moreover, diverse data types are collected in different departments hindering efficient data organization, secure sharing and compliance to the FAIR (Findable, Accessible, Interoperable, Reusable) principles. Henceforth, in this manuscript we present a specialized data management system designed to enhance research workflows in Deep Brain Stimulation (DBS), a state-of-the-art neurosurgical procedure employed to treat symptoms of movement and psychiatric disorders. The system leverages REDCap to promote accurate data capture in hospital settings and secure sharing with research institutes, Brain Imaging Data Structure (BIDS) as image storing standard and a DBS-specific SQLite database as comprehensive data store and unified interface to all data types. A self-developed Python tool automates the data flow between these three components, ensuring their full interoperability. The proposed framework has already been successfully employed for capturing and analyzing data of 107 patients from 2 medical institutions. It effectively addresses the challenges of managing, sharing and retrieving diverse data types, fostering advancements in data quality, organization, analysis, and collaboration among medical and research institutions.

Evolution of Deep Brain Stimulation Techniques for Complication Mitigation

Complication mitigation in deep brain stimulation has been a topic matter of much discussion in the literature. In this article, we examine how neurosurgeons as individuals and as a field generated and adapted techniques to prevent infection, lead fracture/lead migration, and suboptimal outcomes in both the acute period and longitudinally. The authors performed a MEDLINE search inclusive of articles from 1987 to June 2023 including human studies written in English. Using the Rayyan platform, two reviewers (J.P. and R.M.) performed a title screen. Of the 776 articles, 252 were selected by title screen and 172 from abstract review for full-text evaluation. Ultimately, 124 publications were evaluated. We describe the initial complications and inefficiencies at the advent of deep brain stimulation and detail changes instituted by surgeons that reduced them. Furthermore, we discuss the trend in both undesired short-term and long-term outcomes with emphasis on how surgeons recognized and modified their practice to provide safer and better procedures. This scoping review adds to the literature as a guide to both new neurosurgeons and seasoned neurosurgeons alike to understand better what innovations have been trialed over time as we embark on novel targets and neuromodulatory technologies.

STN-DBS electrode placement accuracy and motor improvement in Parkinson's disease: systematic review and individual patient meta-analysis

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective neurosurgical treatment for Parkinson's disease. Surgical accuracy is a critical determinant to achieve an adequate DBS effect on motor performance. A two-millimetre surgical accuracy is commonly accepted, but scientific evidence is lacking. A systematic review and meta-analysis of study-level and individual patient data (IPD) was performed by a comprehensive search in MEDLINE, EMBASE and Cochrane Library. Primary outcome measures were (1) radial error between the implanted electrode and target; (2) DBS motor improvement on the Unified Parkinson's Disease Rating Scale part III (motor examination). On a study level, meta-regression analysis was performed. Also, publication bias was assessed. For IPD meta-analysis, a linear mixed effects model was used. Forty studies (1391 patients) were included, reporting radial errors of 0.45-1.86 mm. Errors within this range did not significantly influence the DBS effect on motor improvement. Additional IPD analysis (206 patients) revealed that a mean radial error of 1.13±0.75 mm did not significantly change the extent of DBS motor improvement. Our meta-analysis showed a huge publication bias on accuracy data in DBS. Therefore, the current literature does not provide an unequivocal upper threshold for acceptable accuracy of STN-DBS surgery. Based on the current literature, DBS-electrodes placed within a 2 mm range of the intended target do not have to be repositioned to enhance motor improvement after STN-DBS for Parkinson's disease. However, an indisputable upper cut-off value for surgical accuracy remains to be established. PROSPERO registration number is CRD42018089539.

Deep Brain Stimulation: Emerging Tools for Simulation, Data Analysis, and Visualization

Deep brain stimulation (DBS) is a well-established neurosurgical procedure for movement disorders that is also being explored for treatment-resistant psychiatric conditions. This review highlights important consideration for DBS simulation and data analysis. The literature on DBS has expanded considerably in recent years, and this article aims to identify important trends in the field. During DBS planning, surgery, and follow up sessions, several large data sets are created for each patient, and it becomes clear that any group analysis of such data is a big data analysis problem and has to be handled with care. The aim of this review is to provide an update and overview from a neuroengineering perspective of the current DBS techniques, technical aids, and emerging tools with the focus on patient-specific electric field (EF) simulations, group analysis, and visualization in the DBS domain. Examples are given from the state-of-the-art literature including our own research. This work reviews different analysis methods for EF simulations, tractography, deep brain anatomical templates, and group analysis. Our analysis highlights that group analysis in DBS is a complex multi-level problem and selected parameters will highly influence the result. DBS analysis can only provide clinically relevant information if the EF simulations, tractography results, and derived brain atlases are based on as much patient-specific data as possible. A trend in DBS research is creation of more advanced and intuitive visualization of the complex analysis results suitable for the clinical environment.

Frameless Robot-Assisted vs Frame-Based Awake Deep Brain Stimulation Surgery: An Evaluation of Technique and New Challenges

BACKGROUND

Methodological approaches to deep brain stimulation (DBS) continue to evolve from awake frame-based to asleep frameless procedures with robotic assistance, primarily directed to optimize operative efficiency, lead accuracy, and patient comfort. Comparison between the 2 is scarce.

OBJECTIVE

To analyze the impacts of methodological differences on operative efficiency and stereotactic accuracy using a frame compared with a frameless robotic platform while maintaining the awake state and use of multiple microelectrode recording (MER) trajectories.

METHODS

Thirty-four consecutive patients who underwent bilateral awake frameless robot-assisted DBS were compared with a previous cohort of 30 patients who underwent frame-based surgery. Patient demographics, operative times, and MER data were collected for both cohorts. Two-dimensional radial errors of lead placements were calculated.

RESULTS

Preoperative setup, surgical, and total operating room times were all significantly greater for the robot-assisted cohort (P < .001). The need for computed tomography imaging when referencing the robotic fiducials led to increased setup duration because of patient transport, unnecessary for the frame-based cohort. Multiple simultaneous MER trajectories increased surgical time (mean 26 min) for the robot-assisted cohort only. The mean radial errors in the robot-assisted and frame cohorts were 0.98 ± 0.66 and 0.74 ± 0.49 mm (P = .03), respectively.

CONCLUSION

The use of a truly frameless robotic platform such as the Mazor Renaissance (Mazor Robotics Ltd) presented challenges when implementing techniques used during awake frame-based surgery. Maintaining good accuracy, intraoperative reference imaging, and limited MER trajectories will help integrate frameless robot assistance into the awake DBS surgical workflow.

Clinical Outcome of "Asleep" Deep Brain Stimulation for Parkinson Disease Using Robot-Assisted Delivery and Anatomic Targeting of the Subthalamic Nucleus: A Series of 152 Patients

BACKGROUND

Recent advances in methods used for deep brain stimulation (DBS) include subthalamic nucleus electrode implantation in the "asleep" patient without the traditional use of microelectrode recordings or intraoperative test stimulation.

OBJECTIVE

To examine the clinical outcome of patients who have undergone "asleep" DBS for the treatment of Parkinson disease using robot-assisted electrode delivery.

METHODS

This is a retrospective review of clinical outcomes of 152 consecutive patients. Their outcomes at 1 yr postimplantation are reported; these include Unified Parkinson's Disease Rating Scale (UPDRS) assessment, Tinetti Mobility Test, Parkinson's Disease Questionnaire (PDQ)-39 quality of life assessment, Mattis Dementia Rating Scale, Beck Depression Inventory, and Beck Anxiety. We also report on a new parietal trajectory for electrode implantation.

RESULTS

A total of 152 patients underwent assessment at 1 yr. UPDRS III improved from 39 to 20.5 (47%, P < .001). The total UPDRS score improved from 67.6 to 36.4 (46%, P < .001). UPDRS II scores improved from 18.9 to 10.5 (44%, P < .001) and UPDRS IV scores improved from 7.1 to 3.6 (49%, P < .001). There was a significant reduction in levodopa equivalent daily dose after surgery (mean: 35%, P < .001). PDQ-39 summary index improved by a mean of 7.1 points. There was no significant difference found in clinical outcomes between the frontal and parietal approaches.

CONCLUSION

"Asleep" robot-assisted DBS of the subthalamic nucleus demonstrates comparable outcomes with traditional techniques in the treatment of Parkinson disease.

CT and MRI Image Fusion Error: An Analysis of Co-Registration Error Using Commercially Available Deep Brain Stimulation Surgical Planning Software

INTRODUCTION

During deep brain stimulation (DBS) surgery, computed tomography (CT) and magnetic resonance imaging (MRI) scans need to be co-registered or fused. Image fusion is associated with the error that can distort the location of anatomical structures. Co-registration in DBS surgery is usually performed automatically by proprietary software; the amount of error during this process is not well understood. Here, our goal is to quantify the error during automated image co-registration with FrameLink™, a commonly used software for DBS planning and clinical research.

METHODS

This is a single-center retrospective study at a quaternary care referral center, comparing CT and MR imaging co-registration for a consecutive series of patients over a 12-month period. We collected CT images and MRI scans for 22 patients with Parkinson's disease requiring placement of DBS. Anatomical landmarks were located on CT images and MRI scans using a novel image analysis algorithm that included a method for capturing the potential error inherent in the image standardization step of the analysis. The distance between the anatomical landmarks was measured, and the error was found by averaging the distances across all patients.

RESULTS

The average error during co-registration was 1.25 mm. This error was significantly larger than the error resulting from image standardization (0.19 mm) and was worse in the anterior-posterior direction.

CONCLUSIONS

The image fusion errors found in this analysis were nontrivial. Although the estimated error may be inflated, it is sig-nificant enough that users must be aware of this potential inaccuracy, and developers of proprietary software should provide details about the magnitude and direction of co-registration errors.

Data-driven evolution of neurosurgical gene therapy delivery in Parkinson's disease

Loss of nigrostriatal dopaminergic projection neurons is a key pathology in Parkinson's disease, leading to abnormal function of basal ganglia motor circuits and the accompanying characteristic motor features. A number of intraparenchymally delivered gene therapies designed to modify underlying disease and/or improve clinical symptoms have shown promise in preclinical studies and subsequently were evaluated in clinical trials. Here we review the challenges with surgical delivery of gene therapy vectors that limited therapeutic outcomes in these trials, particularly the lack of real-time monitoring of vector administration. These challenges have recently been addressed during the evolution of novel techniques for vector delivery that include the use of intraoperative MRI. The preclinical development of these techniques are described in relation to recent clinical translation in an adeno-associated virus serotype 2-mediated human aromatic L-amino acid decarboxylase gene therapy development programme. This new paradigm allows visualisation of the accuracy and adequacy of viral vector delivery within target structures, enabling intertrial modifications in surgical approaches, cannula design, vector volumes and dosing. The rapid, data-driven evolution of these procedures is unique and has led to improved vector delivery.

Frameless Robot-Assisted Deep Brain Stimulation Surgery: An Initial Experience

BACKGROUND

Modern robotic-assist surgical systems have revolutionized stereotaxy for a variety of procedures by increasing operative efficiency while preserving and even improving accuracy and safety. However, experience with robotic systems in deep brain stimulation (DBS) surgery is scarce.

OBJECTIVE

To present an initial series of DBS surgery performed utilizing a frameless robotic solution for image-guided stereotaxy, and report on operative efficiency, stereotactic accuracy, and complications.

METHODS

This study included the initial 20 consecutive patients undergoing bilateral robot-assisted DBS. The prior 20 nonrobotic, frameless cohort of DBS cases was sampled as a baseline historic control. For both cohorts, patient demographic and clinical data were collected including postoperative complications. Intraoperative duration and number of Microelectrode recording (MER) and final lead passes were recorded. For the robot-assisted cohort, 2D radial errors were calculated.

RESULTS

Mean case times (total operating room, anesthesia, and operative times) were all significantly decreased in the robot-assisted cohort (all P-values < .02) compared to frameless DBS. When looking at trends in case times, operative efficiency improved over time in the robot-assisted cohort across all time assessment points. Mean radial error in the robot-assisted cohort was 1.40 ± 0.11 mm, and mean depth error was 1.05 ± 0.18 mm. There was a significant decrease in the average number of MER passes in the robot-assisted cohort (1.05) compared to the nonrobotic cohort (1.45, P < .001).

CONCLUSION

This is the first report of application of frameless robotic-assistance with the Mazor Renaissance platform (Mazor Robotics Ltd, Caesarea, Israel) for DBS surgery, and our findings reveal that an initial experience is safe and can have a positive impact on operative efficiency, accuracy, and safety.

Bilateral Subthalamic Nucleus Deep Brain Stimulation under General Anesthesia: Literature Review and Single Center Experience

Bilateral subthalamic nucleus (STN) Deep brain stimulation (DBS) is a well-established treatment in patients with Parkinson's disease (PD). Traditionally, STN DBS for PD is performed by using microelectrode recording (MER) and/or intraoperative macrostimulation under local anesthesia (LA). However, many patients cannot tolerate the long operation time under LA without medication. In addition, it cannot be even be performed on PD patients with poor physical and neurological condition. Recently, it has been reported that STN DBS under general anesthesia (GA) can be successfully performed due to the feasible MER under GA, as well as the technical advancement in direct targeting and intraoperative imaging. The authors reviewed the previously published literature on STN DBS under GA using intraoperative imaging and MER, focused on discussing the technique, clinical outcome, and the complication, as well as introducing our single-center experience. Based on the reports of previously published studies and ours, GA did not interfere with the MER signal from STN. STN DBS under GA without intraoperative stimulation shows similar or better clinical outcome without any additional complication compared to STN DBS under LA. Long-term follow-up with a large number of the patients would be necessary to validate the safety and efficacy of STN DBS under GA.

Comparison of Awake and Asleep Deep Brain Stimulation for Parkinson's Disease: A Detailed Analysis Through Literature Review

OBJECTIVES

Deep brain stimulation (DBS) for Parkinson's disease (PD) has been applied to clinic for approximately 30 years. The goal of this review is to explore the similarities and differences between "awake" and "asleep" DBS techniques.

METHODS

A comprehensive literature review was carried out to identify relevant studies and review articles describing applications of "awake" or "asleep" DBS for Parkinson's disease. The surgical procedures, clinical outcomes, costs and complications of each technique were compared in detail through literature review.

RESULTS

The surgical procedures of awake and asleep DBS surgeries rely upon different methods for verification of intended target acquisition. The existing research results demonstrated that the stereotactic targeting accuracy of lead placement obtained by either method is reliable. There were no significant differences in clinical outcomes, costs, or complications between the two techniques.

CONCLUSION

The surgical and clinical outcomes of asleep DBS for PD are comparable to those of awake DBS.

Frameless ROSA® Robot-Assisted Lead Implantation for Deep Brain Stimulation: Technique and Accuracy

BACKGROUND

Frameless robotic-assisted surgery is an innovative technique for deep brain stimulation (DBS) that has not been assessed in a large cohort of patients.

OBJECTIVE

To evaluate accuracy of DBS lead placement using the ROSA® robot (Zimmer Biomet) and a frameless registration.

METHODS

All patients undergoing DBS surgery in our institution between 2012 and 2016 were prospectively included in an open label single-center study. Accuracy was evaluated by measuring the radial error (RE) of the first stylet implanted on each side and the RE of the final lead position at the target level. RE was measured on intraoperative telemetric X-rays (group 1), on intraoperative O-Arm® (Medtronic) computed tomography (CT) scans (group 2), and on postoperative CT scans or magnetic resonance imaging (MRI) in both groups.

RESULTS

Of 144 consecutive patients, 119 were eligible for final analysis (123 DBS; 186 stylets; 192 leads). In group 1 (76 patients), the mean RE of the stylet was 0.57 ± 0.02 mm, 0.72 ± 0.03 mm for DBS lead measured intraoperatively, and 0.88 ± 0.04 mm for DBS lead measured postoperatively on CT scans. In group 2 (43 patients), the mean RE of the stylet was 0.68 ± 0.05 mm, 0.75 ± 0.04 mm for DBS lead measured intraoperatively; 0.86 ± 0.05 mm and 1.10 ± 0.08 mm for lead measured postoperatively on CT scans and on MRI, respectively No statistical difference regarding the RE of the final lead position was found between the different intraoperative imaging modalities and postoperative CT scans in both groups.

CONCLUSION

Frameless ROSA® robot-assisted technique for DBS reached submillimeter accuracy. Intraoperative CT scans appeared to be reliable and sufficient to evaluate the final lead position.

The interventional magnetic resonance imaging suite: Experience in the design, development, and implementation in a pre-existing radiology space and review of concepts

BACKGROUND

Intraoperative magnetic resonance imaging (ioMRI) has led to significant advancements in neurosurgery with improved accuracy, assessment of the extent of resection, less invasive surgical alternatives, and real-time confirmation of targeting as well delivery of therapies. The costs associated with developing ioMRI units in the surgical suite have been obstacles to the expansion of their use. More recently, the development of hybrid interventional MRI (iMRI) units has become a viable alternative. The process of designing, developing, and implementing operations for these units requires the careful integration of environmental, technical, and safety elements of both surgical and MR practices. There is a paucity of published literature providing guidance for institutions looking to develop a hybrid iMRI unit, especially with a limited footprint in the radiology department.

METHODS

The experience of designing, developing, and implementing an iMRI in a preexisting space for neurosurgical procedures at a single institution in light of available options and the literature is described.

RESULTS

The development of the unit was accomplished through the engagement of a multidisciplinary team of stakeholders who utilized existing guidelines and recommendations and their own professional experience to address issues including physical layout, equipment selection, operations planning, infection control, and oversight/review, among others.

CONCLUSION

Successful creation of an iMRI program requires multidisciplinary collaboration in integrating surgical and MR practice. The authors' aim is that the experience described in this article will serve as an example for facilities or neurosurgical departments looking to navigate the same process.

Hemorrhagic complications seen on immediate intraprocedural stereotactic computed tomography imaging during deep brain stimulation implantation

BACKGROUND

We present our operative experience of patients with movement disorders who developed intracerebral hemorrhage (ICH), which was identified on intraprocedural stereotactic computed tomography (CT) imaging performed immediately after deep brain stimulation (DBS) lead placement and prior to the implantation of further components of the DBS hardware.

METHODS

Patients who underwent DBS lead implantation from January 2009 through December 2017 were included in the present study. Most of the surgeries were performed in a staged fashion. All patients were operated using identical surgical and intraprocedural imaging techniques, and no microelectrode recordings were done. Leksell Stereotactic G frame and neuronavigation software was utilized for all surgeries. Intraprocedural stereotactic CT was performed to confirm the precise position of the implanted DBS lead and to rule out any hemorrhagic complications.

RESULTS

Overall, 222 patients underwent 322 DBS lead implantations during 316 stereotactic procedures. Six patients exhibited early ICH recognized on intraprocedural stereotactic CT performed immediately after DBS lead placement; in addition, two patients developed delayed ICH due to large venous infarction. Four patients with ICH were asymptomatic. The ICH rate was 2.5% per electrode and 3.6% per patient; the permanent deficit rate was 1.2% per electrode and 1.8% per patient. The death rate due to ICH in our cohort was 0.6% per electrode and 0.9% per patient.

CONCLUSIONS

Intraprocedural stereotactic CT can not only visualize the implanted DBS lead in the stereotactic space but also rule out early ICH. Identified predisposing factors for development of ICH include patient's age, hypertension, and previous antiplatelet therapy. Careful planning of stereotactic trajectories plays a paramount role in reducing the rate of ICH in DBS surgery.

Deep brain stimulation outcomes in patients implanted under general anesthesia with frame-based stereotaxy and intraoperative MRI

OBJECTIVEThe authors' aim in this study was to evaluate placement accuracy and clinical outcomes in patients who underwent implantation of deep brain stimulation devices with the aid of frame-based stereotaxy and intraoperative MRI after induction of general anesthesia.METHODSThirty-three patients with movement disorders (27 with Parkinson's disease) underwent implantation of unilateral or bilateral deep brain stimulation systems (64 leads total). All patients underwent the implantation procedure with standard frame-based techniques under general anesthesia and without microelectrode recording. MR images were acquired immediately after the procedure and fused to the preoperative plan to verify accuracy. To evaluate clinical outcome, different scales were used to assess quality of life (EQ-5D), activities of daily living (Unified Parkinson's Disease Rating Scale [UPDRS] part II), and motor function (UPDRS part III during off- and on-medication and off- and on-stimulation states). Accuracy was assessed by comparing the coordinates (x, y, and z) from the preoperative plan and coordinates from the tip of the lead on intraoperative MRI and postoperative CT scans.RESULTSThe EQ-5D score improved or remained stable in 71% of the patients. When in the off-medication/on-stimulation state, all patients reported significant improvement in UPDRS III score at the last follow-up (p < 0.001), with a reduction of 25.2 points (46.3%) (SD 14.7 points and 23.5%, respectively). There was improvement or stability in the UPDRS II scores for 68% of the Parkinson's patients. For 2 patients, the stereotactic error was deemed significant based on intraoperative MRI findings. In these patients, the lead was removed and replaced after correcting for the error during the same procedure. Postoperative lead revision was not necessary in any of the patients. Based on findings from the last intraoperative MRI study, the mean difference between the tip of the electrode and the planned target was 0.82 mm (SD 0.5 mm, p = 0.006) for the x-axis, 0.67 mm (SD 0.5 mm, p < 0.001) for the y-axis, and 0.78 mm (SD 0.7 mm, p = 0.008) for the z-axis. On average, the euclidian distance was 1.52 mm (SD 0.6 mm). In patients who underwent bilateral implantation, accuracy was further evaluated comparing the first implanted side and the second implanted side. There was a significant mediolateral (x-axis) difference (p = 0.02) in lead accuracy between the first (mean 1.02 mm, SD 0.57 mm) and the second (mean 0.66 mm, SD 0.50 mm) sides. However, no significant difference was found for the y- and z-axes (p = 0.10 and p = 0.89, respectively).CONCLUSIONSFrame-based DBS implantation under general anesthesia with intraoperative MRI verification of lead location is safe, accurate, precise, and effective compared with standard implantation performed using awake intraoperative physiology. More clinical trials are necessary to directly compare outcomes of each technique.

A novel re-attachable stereotactic frame for MRI-guided neuronavigation and its validation in a large animal and human cadaver model

OBJECTIVE

Stereotactic frame systems are the gold-standard for stereotactic surgeries, such as implantation of deep brain stimulation (DBS) devices for treatment of medically resistant neurologic and psychiatric disorders. However, frame-based systems require that the patient is awake with a stereotactic frame affixed to their head for the duration of the surgical planning and implantation of the DBS electrodes. While frameless systems are increasingly available, a reusable re-attachable frame system provides unique benefits. As such, we created a novel reusable MRI-compatible stereotactic frame system that maintains clinical accuracy through the detachment and reattachment of its stereotactic devices used for MRI-guided neuronavigation.

APPROACH

We designed a reusable arc-centered frame system that includes MRI-compatible anchoring skull screws for detachment and re-attachment of its stereotactic devices. We validated the stability and accuracy of our system through phantom, in vivo mock-human porcine DBS-model and human cadaver testing.

MAIN RESULTS

Phantom testing achieved a root mean square error (RMSE) of 0.94  ±  0.23 mm between the ground truth and the frame-targeted coordinates; and achieved an RMSE of 1.11  ±  0.40 mm and 1.33  ±  0.38 mm between the ground truth and the CT- and MRI-targeted coordinates, respectively. In vivo and cadaver testing achieved a combined 3D Euclidean localization error of 1.85  ±  0.36 mm (p  <  0.03) between the pre-operative MRI-guided placement and the post-operative CT-guided confirmation of the DBS electrode.

SIGNIFICANCE

Our system demonstrated consistent clinical accuracy that is comparable to conventional frame and frameless stereotactic systems. Our frame system is the first to demonstrate accurate relocation of stereotactic frame devices during in vivo MRI-guided DBS surgical procedures. As such, this reusable and re-attachable MRI-compatible system is expected to enable more complex, chronic neuromodulation experiments, and lead to a clinically available re-attachable frame that is expected to decrease patient discomfort and costs of DBS surgery.

Deep brain stimulation for seizure control in drug-resistant epilepsy

Antiepileptic drugs prevent morbidity and death in a large number of patients suffering from epilepsy. However, it is estimated that approximately 30% of epileptic patients will not have adequate seizure control with medication alone. Resection of epileptogenic cortex may be indicated in medically refractory cases with a discrete seizure focus in noneloquent cortex. For patients in whom resection is not an option, deep brain stimulation (DBS) may be an effective means of seizure control. Deep brain stimulation targets for treating seizures primarily include the thalamic nuclei, hippocampus, subthalamic nucleus, and cerebellum. A variety of stimulation parameters have been studied, and more recent advances in electrical stimulation to treat epilepsy include responsive neurostimulation. Data suggest that DBS is effective for treating drug-resistant epilepsy.

Brain Shift and Pneumocephalus Assessment During Frame-Based Deep Brain Stimulation Implantation With Intraoperative Magnetic Resonance Imaging

BACKGROUND

Brain shift and pneumocephalus are major concerns regarding deep brain stimulation (DBS).

OBJECTIVE

To report the extent of brain shift in deep structures and pneumocephalus in intraoperative magnetic resonance imaging (MRI).

METHODS

Twenty patients underwent bilateral DBS implantation in an MRI suite. Volume of pneumocephalus, duration of procedure, and 6 anatomic landmarks (anterior commissure, posterior commissure, right fornix [RF], left fornix [LF], right putaminal point, and left putaminal point) were measured.

RESULTS

Pneumocephalus varied from 0 to 32 mL (median = 0.6 mL). Duration of the procedure was on average 195.5 min (118-268 min) and was not correlated with the amount of pneumocephalus. There was a significant posterior displacement of the anterior commissure (mean = -1.1 mm, P < .001), RF (mean = -0.6 mm, P < .001), LF (mean = -0.7 mm, P < .001), right putaminal point (mean = -0.9 mm, P = .001), and left putaminal point (mean = -1.0 mm, P = .001), but not of the posterior commissure (mean = 0.0 mm, P = .85). Both RF (mean = -.7 mm, P < .001) and LF (mean = -0.5 mm, P < .001) were posteriorly displaced after a right-sided burr hole. There was a correlation between anatomic landmarks displacement and pneumocephalus after 2 burr holes (rho = 0.61, P = .007), but not after 1 burr hole (rho = 0.16, P = .60).

CONCLUSION

Better understanding of how pneumocephalus displaces subcortical structures can significantly enhance our intraoperative decision making and overall targeting strategy.

Awake versus Asleep Deep Brain Stimulation Surgery: Technical Considerations and Critical Review of the Literature

Advancements in neuroimaging have led to a trend toward direct, image-based targeting under general anesthesia without the use of microelectrode recording (MER) or intraoperative test stimulation, also referred to as “asleep” deep brain stimulation (DBS) surgery. Asleep DBS, utilizing imaging in the form of intraoperative computed tomography (iCT) or magnetic resonance imaging (iMRI), has demonstrated reliable targeting accuracy of DBS leads implanted within the globus pallidus and subthalamic nucleus while also improving clinical outcomes in patients with Parkinson’s disease. In lieu, of randomized control trials, retrospective comparisons between asleep and awake DBS with MER have shown similar short-term efficacy with the potential for decreased complications in asleep cohorts. In lieu of long-term outcome data, awake DBS using MER must demonstrate more durable outcomes with fewer stimulation-induced side effects and lead revisions in order for its use to remain justifiable; although patient-specific factors may also be used to guide the decision regarding which technique may be most appropriate and tolerable to the patient.

Comparison of General and Local Anesthesia for Deep Brain Stimulator Insertion: A Systematic Review

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) has become a standard treatment for many patients with Parkinson's disease (PD). The reported clinical outcome measures for procedures done under general anesthesia (GA) compared to traditional local anesthetic (LA) technique are quite heterogeneous and difficult to compare. The aim of this systematic review and metaanalysis was to determine whether the clinical outcome after STN-DBS insertion under GA is comparable to that under LA in patients with Parkinson's disease.

METHODS

The databases of Medline Embase, Cochrane library and Pubmed were searched for eligible studies (human trials, English language, published between 1946 and January of 2016). The primary outcome of this study was to assess the postoperative improvement in the symptoms, evaluated using either Unified Parkinson's Disease Rating Scale (UPDRS) scores or levodopa equivalent dosage (LEDD) requirement.

RESULTS

The literature searches yielded 395 citations and six retrospective cohort studies with a sample size of 455 (194 in GA and 261 in LA) were included in the analysis. Regarding the clinical outcomes, there were no significant differences in the postoperative Unified Parkinson's disease rating scale and levodopa equivalent drug dosage between the GA and the LA groups. Similarly, the adverse events and target accuracy were also comparable between the groups.

CONCLUSIONS

This systematic review and meta-analysis shows that currently there is no good quality data to suggest equivalence of GA to LA during STN-DBS insertion in patients with PD, with some factors trending towards LA. There is a need for a prospective randomized control trial to validate our results.

Intraoperative clinical testing overestimates the therapeutic window of the permanent DBS electrode in the subthalamic nucleus

BACKGROUND

Intraoperative test stimulation is established to optimize target localization in STN DBS, but requires a time-consuming awake surgery in off-medication state. The aim of this study was to compare the thresholds of stimulation-induced effects of test stimulation and the permanent electrode.

METHODS

Fifty-nine PD patients receiving bilateral STN DBS were clinically examined with stepwise increasing monopolar stimulation during surgery and DBS programming at matched stimulation depths. Thresholds of therapeutic and side effects were obtained from standardized examination protocols.

RESULTS

Postoperative stimulation via the permanent electrode caused side effects at a significantly lower threshold than predicted during intraoperative test stimulation (P < 0.001); whereas sufficient therapeutic effects were achieved at significantly higher thresholds (P < 0.001).

CONCLUSIONS

Intraoperative testing may lead to an overestimation of the therapeutic window. The two different electrodes lead to distinct spreading of the electric field in the STN and surrounding tissues that causes different volume of tissue activated (VTA). Clinicians involved in DBS surgery and programming should be aware of the differences in both stimulation settings, concerning electrodes geometry, stimulation modes as well as the impact of time. Therapeutic and side effects of permanent stimulation are not predictable by intraoperative test stimulation. Test stimulation may be an orientating test for very low thresholds of side effects instead.

MRI-guided stereotactic neurosurgical procedures in a diagnostic MRI suite: Background and safe practice recommendations

The development of navigation technology facilitating MRI-guided stereotactic neurosurgery has enabled neurosurgeons to perform a variety of procedures ranging from deep brain stimulation to laser ablation entirely within an intraoperative or diagnostic MRI suite while having real-time visualization of brain anatomy. Prior to this technology, some of these procedures required multisite workflow patterns that presented significant risk to the patient during transport. For those facilities with access to this technology, safe practice guidelines exist only for procedures performed within an intraoperative MRI. There are currently no safe practice guidelines or parameters available for facilities looking to integrate this technology into practice in conventional MRI suites. Performing neurosurgical procedures in a diagnostic MRI suite does require precautionary measures. The relative novelty of technology and workflows for direct MRI-guided procedures requires consideration of safe practice recommendations, including those pertaining to infection control and magnet safety issues. This article proposes a framework of safe practice recommendations designed for assessing readiness and optimization of MRI-guided neurosurgical interventions in the diagnostic MRI suite in an effort to mitigate patient risk. The framework is based on existing clinical evidence, recommendations, and guidelines related to infection control and prevention, health care-associated infections, and magnet safety, as well as the clinical and practical experience of neurosurgeons utilizing this technology.

Improving the accuracy of microelectrode recording in deep brain stimulation surgery with intraoperative CT

Microelectrode recording (MER) is used to confirm electrophysiological signals within intended anatomic targets during deep brain stimulation (DBS) surgery. We describe a novel technique called intraoperative CT-guided extrapolation (iCTE) to predict the intended microelectrode trajectory and, if necessary, make corrections in real-time before dural opening. Prior to dural opening, a guide tube was inserted through the headstage and rested on dura. Intraoperative CT (iCT) was obtained, and a trajectory was extrapolated along the path of the guide tube to target depth using targeting software. The coordinates were recorded and compared to initial plan coordinates. If needed, adjustments were made using the headstage to correct for error. The guide tube was then inserted and MER ensued. At target, iCT was performed and microelectrode tip coordinates were compared with planned/adjusted track coordinates. Radial error between MER track and planned/adjusted track was calculated. For comparison, MER track error prior to the iCTE technique was assessed retrospectively in patients who underwent MER using iCT, whereby iCT was performed following completion of the first MER track. Forty-seven MER tracks were analyzed prior to iCTE (pre-iCTE), and 90 tracks were performed using the iCTE technique. There was no difference between radial error of pre-iCTE MER track and planned trajectory (2.1±0.12mm) compared to iCTE predicted trajectory and planned trajectory (1.76±0.13mm, p>0.05). iCTE was used to make trajectory adjustments which reduced radial error between the newly corrected and final microelectrode tip coordinates to 0.84±0.08mm (p<0.001). Inter-rater reliability was also tested using a second blinded measurement reviewer which showed no difference between predicted and planned MER track error (p=0.53). iCTE can predict and reduce trajectory error for microelectrode placement compared with the traditional use of iCT post MER.

Innovations in Functional Neurosurgery and Anesthetic Implications

Functional neurosurgery has undergone rapid growth over the last few years fueled by advances in imaging technology and novel treatment modalities. These advances have led to new surgical treatments using minimally invasive and precise techniques for conditions such as Parkinson's disease, essential tremor, epilepsy, and psychiatric disorders. Understanding the goals and technological issues of these procedures is imperative for the anesthesiologist to ensure safe management of patients presenting for functional neurosurgical procedures. In this review, we discuss the advances in neurosurgical techniques for deep brain stimulation, focused ultrasound and minimally invasive laser-based treatment of refractory epilepsy and provide a guideline for anesthesiologists caring for patients undergoing these procedures.

Proceedings of the Fourth Annual Deep Brain Stimulation Think Tank: A Review of Emerging Issues and Technologies

This paper provides an overview of current progress in the technological advances and the use of deep brain stimulation (DBS) to treat neurological and neuropsychiatric disorders, as presented by participants of the Fourth Annual DBS Think Tank, which was convened in March 2016 in conjunction with the Center for Movement Disorders and Neurorestoration at the University of Florida, Gainesveille FL, USA. The Think Tank discussions first focused on policy and advocacy in DBS research and clinical practice, formation of registries, and issues involving the use of DBS in the treatment of Tourette Syndrome. Next, advances in the use of neuroimaging and electrochemical markers to enhance DBS specificity were addressed. Updates on ongoing use and developments of DBS for the treatment of Parkinson's disease, essential tremor, Alzheimer's disease, depression, post-traumatic stress disorder, obesity, addiction were presented, and progress toward innovation(s) in closed-loop applications were discussed. Each section of these proceedings provides updates and highlights of new information as presented at this year's international Think Tank, with a view toward current and near future advancement of the field.

Convection-enhanced delivery improves MRI visualization of basal ganglia for stereotactic surgery

OBJECTIVE Stereotactic deep brain stimulation surgery is most commonly performed while patients are awake. This allows for intraoperative clinical assessment and electrophysiological target verification, thereby promoting favorable outcomes with few side effects. Intraoperative CT and MRI have challenged this concept of clinical treatment validation. Image-guided surgery is capable of delivering electrodes precisely to a planned, stereotactic target; however, these methods can be limited by low anatomical resolution even with sophisticated MRI modalities. The authors are developing a novel method using convection-enhanced delivery to safely manipulate the extracellular space surrounding common anatomical targets for surgery. By altering the extracellular content of deep subcortical structures and their associated white matter tracts, the MRI visualization of the basal ganglia can be improved to better define the anatomy. This technique could greatly improve the accuracy and success of stereotactic surgery, potentially eliminating the reliance on awake surgery. METHODS Observations were made in the clinical setting where vasogenic and cytotoxic edema improved the MRI visualization of the basal ganglia. These findings were replicated in the experimental setting using an FDA-approved intracerebral catheter that was stereotactically inserted into the thalamus or basal ganglia of 7 swine. Five swine were infused with normal saline, and 2 were infused with autologous CSF. Flow rates varied between 1 μl/min to 6 μl/min to achieve convective distributions. Concurrent MRI was performed at 15-minute intervals to monitor the volume of infusion and observe the imaging changes of the deep subcortical structures. The animals were then clinically observed, and necropsy was performed within 48 hours, 1 week, or 1 month for histological analysis. RESULTS In all animals, the white matter tracts became hyperintense on T2-weighted imaging as compared with basal ganglia nuclei, enabling better definition of the deep brain anatomy. The volume of distribution and infusion (Vd/Vi ratio) ranged from 2.5 to 4.5. There were no observed clinical effects from the infusions. Histological analysis demonstrated mild neuronal effects from saline infusions but no effects from CSF infusions. CONCLUSIONS This work provides the initial foundation for a novel approach to improve the visualization of deep brain anatomy during MRI-guided, stereotactic procedures. Convective infusions of CSF alter the extracellular fluid content of the brain for improved MRI without evidence of clinical or toxic effects.

The use of custom 3D printed stereotactic frames for laser interstitial thermal ablation: technical note

Over the last several years, laser interstitial thermotherapy (LITT) has gained wide acceptance for the treatment of a myriad of cranial lesions. A wide variety of techniques for placement of the laser fiber have been reported with a spectrum of perceived benefits and drawbacks. The authors present the first report of a customized 3D printed stereotactic frame for LITT.

Approximately 1 week prior to surgery, 3–4 skull fiducials were placed after each of 5 patients received a local anesthetic as an outpatient. Radiographs with these fiducials were then used to create a trajectory to the lesion that would be treated with LITT. After the plan was completed, software was used to render a customized frame. On the day of surgery, the frame was attached to the implanted skull fiducials and the LITT catheter was placed. This procedure was carried out in 5 consecutive patients. In 2 patients, a needle biopsy was also performed.

Intraoperative and postoperative imaging studies confirmed the accurate placement of the LITT catheter and the lesion created. Mean operating room time for all patients was 45 minutes but only 26 minutes when excluding the cases in which a biopsy was performed.

To the best of the authors' knowledge, this is the first report of the use of a specific system, the STarFix microTargeting system, for use with LITT and brain biopsy. This system offers several advantages including fast operating times, extensive preoperative planning, no need for cranial fixation, and no need for frame or fiducial placement on the day of surgery. The accuracy of the system combined with these advantages may make this a preferred stereotactic method for LITT, especially in centers where LITT is performed in a diagnostic MRI suite.

Deep brain stimulation for Parkinson's disease: current status and future outlook

Parkinson's disease is a neurodegenerative condition secondary to loss of dopaminergic neurons in the substantia nigra pars compacta. Surgical therapy serves as an adjunct when unwanted medication side effects become apparent or additional therapy is needed. Deep brain stimulation emerged into the forefront in the 1990s. Studies have demonstrated improvement in all of the cardinal parkinsonian signs with stimulation. Frameless and ‘mini-frame’ stereotactic systems, improved MRI for anatomic visualization, and intraoperative MRI-guided placement are a few of the surgical advances in deep brain stimulation. Other advances include rechargeable pulse generators, voltage- or current-based stimulation, and enhanced abilities to ‘steer’ stimulation. Work is ongoing investigating closed-loop ‘smart’ stimulation in which stimulation is predicated on neuronal feedback.

Intraoperative real-time MRI-guided stereotactic biopsy followed by laser thermal ablation for progressive brain metastases after radiosurgery

Stereotactic radiosurgery is one of the treatment options for brain metastases. However, there are patients who will progress after radiosurgery. One of the potential treatments for this subset of patients is laser ablation. Image-guided stereotactic biopsy is important to determine the histopathological nature of the lesion. However, this is usually based on preoperative, static images, which may affect the target accuracy during the actual procedure as a result of brain shift. We therefore performed real-time intraoperative MRI-guided stereotactic aspiration and biopsies on two patients with symptomatic, progressive lesions after radiosurgery followed immediately by laser ablation. The patients tolerated the procedure well with no new neurologic deficits. Intraoperative MRI-guided stereotactic biopsy followed by laser ablation is safe and accurate, providing real-time updates and feedback during the procedure.