Intraoperative MRI for optimizing electrode placement for deep brain stimulation of the subthalamic nucleus in Parkinson disease

Intraoperative MRI: A Review of Applications Across Neurosurgical Specialties

Intraoperative MRI (iMRI) made its debut to great fanfare in the mid-1990s. However, the enthusiasm for this technology with seemingly obvious benefits for neurosurgeons has waned. We review the benefits and utility of iMRI across the field of neurosurgery and present an overview of the evidence for iMRI for multiple neurosurgical disciplines: tumor, skull base, vascular, pediatric, functional, and spine. Publications on iMRI have steadily increased since 1996, plateauing with approximately 52 publications per year since 2011. Tumor surgery, especially glioma surgery, has the most evidence for the use of iMRI contributing more than 50% of all iMRI publications, with increased rates of gross total resection in both adults and children, providing a potential survival benefit. Across multiple neurosurgical disciplines, the ability to use a multitude of unique sequences (diffusion tract imaging, diffusion-weighted imaging, magnetic resonance angiography, blood oxygenation level-dependent) allows for specialization of imaging for various types of surgery. Generally, iMRI allows for consideration of anatomic changes and real-time feedback on surgical outcomes such as extent of resection and instrument (screw, lead, electrode) placement. However, implementation of iMRI is limited by cost and feasibility, including the need for installation, shielding, and compatible tools. Evidence for iMRI use varies greatly by specialty, with the most evidence for tumor, vascular, and pediatric neurosurgery. The benefits of real-time anatomic imaging, a lack of radiation, and evaluation of surgical outcomes are limited by the cost and difficulty of iMRI integration. Nonetheless, the ability to ensure patients are provided by a maximal yet safe treatment that specifically accounts for their own anatomy and highlights why iMRI is a valuable and underutilized tool across multiple neurosurgical subspecialties.

Long-term efficacy of deep brain stimulation of the subthalamic nucleus in patients with pharmacologically intractable epilepsy: A case series of six patients

OBJECTIVE

Epilepsy is one of the widespread neurological illnesses, and about 20%-40% of epilepsy patients are pharmacoresistant. We aimed to assess the long-term efficacy of subthalamic nucleus (STN) deep brain stimulation (DBS) for drug-resistant epilepsy.

METHODS

We included pharmacologically intractable epilepsy patients who had STN-DBS at the Chinese People's Liberation Army General Hospital between June 2016 and December 2018. We retrospectively evaluated pre- and postoperative clinical outcomes, including seizure frequency, seizure type, anti-seizure medication, cognitive function, anatomical target coordinates, stimulation parameters, and adverse events following the surgical procedure. Six patients with a mean follow-up of 49.3 ± 10.2 months, were included.

RESULTS

Seizure frequency decreased by an average of 64.0% after STN-DBS at last year follow-up (p = .046), and one patient (1/6) achieved seizure-free status. For seizure type, anti-seizure medication, and cognitive function, there were no significant differences between pre-and post-operation (p > .05). In terms of stimulation parameters, the pulse width, amplitude, and frequency were 58.3 ± 9.4 μs, 2.5 ± .7 V, and 122.5 ± 15.7 Hz, respectively. None of the patients showed normal electroencephalography during the electroencephalography reexamination. There were no surgery-related complications, and chronic STN stimulation was generally well tolerated in five patients. However, one patient (1/6) had a difficulty of dyskinesia in the right arm.

SIGNIFICANCE

In conclusion, neuromodulation of the STN by DBS is a promising option for patients with pharmacologically intractable epilepsy, especially for whose epileptic zone originates mainly from the frontoparietal region and who are unsuitable for resective surgery. Further prospective multicenter studies with a larger sample size are necessary for further exploration.

A Novel Portable, Mobile MRI: Comparison with an Established Low-Field Intraoperative MRI System

Background  MRI (magnetic resonance imaging) using low-magnet field strength has unique advantages for intraoperative use. We compared a novel, compact, portable MR imaging system to an established intraoperative 0.15 T system to assess potential utility in intracranial neurosurgery. Methods  Brain images were acquired with a 0.15 T intraoperative MRI (iMRI) system and a 0.064 T portable MR system. Five healthy volunteers were scanned. Individual sequences were rated on a 5-point (1 to 5) scale for six categories: contrast, resolution, coverage, noise, artifacts, and geometry. Results  Overall, the 0.064 T images (M = 3.4, SD = 0.1) had statistically higher ratings than the 0.15 T images (M = 2.4, SD = 0.2) ( p  < 0.01). All comparable sequences (T1, T2, T2 FLAIR and SSFP) were rated significantly higher on the 0.064 T and were rated 1.2 points (SD = 0.3) higher than 0.15 T scanner, with the T2 fluid-attenuated inversion recovery (FLAIR) sequences showing the largest increment on the 0.064 T with an average rating difference of 1.5 points (SD = 0.2). Scanning time for the 0.064 T system obtained images more quickly and encompassed a larger field of view than the 0.15 T system. Conclusions  A novel, portable 0.064 T self-shielding MRI system under ideal conditions provided images of comparable quality or better and faster acquisition times than those provided by the already well-established 0.15 T iMR system. These results suggest that the 0.064 T MRI has the potential to be adapted for intraoperative use for intracranial neurosurgery.

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.

Short- and Long-Term Efficacy and Safety of Deep-Brain Stimulation in Parkinson's Disease Patients aged 75 Years and Older

Objective: The aim of this study was to investigate the efficacy and safety of deep-brain stimulation (DBS) in the treatment of patients with Parkinson’s disease aged 75 years and older. Methods: From March 2013 to June 2021, 27 patients with Parkinson’s disease (≥75 years old) who underwent DBS surgery at the First Medical Center of the PLA General Hospital were selected. The Unified Parkinson’s Disease Rating Scale Part 3 (UPDRS-III), 39-item Parkinson’s Disease Questionnaire (PDQ-39), and Barthel Index for Activities of Daily Living (BI) scores were used to evaluate motor function and quality of life before surgery and during on and off periods of DBS at 1 year post operation and at the final follow-up. A series of non-motor scales were used to evaluate sleep, cognition, and mood, and the levodopa equivalent daily dose (LEDD) was also assessed. Adverse events related to surgery were noted. Results: The average follow-up time was 55.08 (21−108) months. Symptoms were significantly improved at 1 year post operation. The median UPDRS-III score decreased from 35 points (baseline) to 19 points (improvement of 45.7%) in the stimulation-on period at 1 year post operation (t = 19.230, p < 0.001) and to 32 points (improvement of 8.6%) at the final follow-up (t = 3.456, p = 0.002). In the stimulation-off period, the median score of UPDRS-III increased from 35 points to 39 points (deterioration of −11.4%) at 1 year post operation (Z = −4.030, p < 0.001) and 45 points (deterioration of −28.6%) at the final follow-up (Z = −4.207, p < 0.001). The PDQ-39 overall scores decreased from 88 points (baseline) to 55 points (improvement of 37.5%) in the stimulation-on period at 1 year post operation (t = 11.390, p < 0.001) and 81 points (improvement of 8.0%) at the final follow-up (t = 2.142, p = 0.044). In the stimulation-off period, the median PDQ-39 score increased from 88 points to 99 points (deterioration of −12.5%) at the final follow-up (Z = −2.801, p = 0.005). The ADL-Barthel Index score increased from 25 points (baseline) to 75 points (improvement of 66.7%) at 1 year post operation (Z = −4.205, p < 0.001) and to 35 points (improvement of 28.6%) at the final follow-up (Z = −4.034, p < 0.001). In the stimulation-off period, BI scores decreased from 25 points to 15 points (deterioration of −40%) at 1 year post operation (Z = −3.225, p = 0.01) and to 15 points (deterioration of −40%) at the final follow-up (Z = −3.959, p = 0.001). Sleep, cognition, and mood were slightly improved at 1 year post operation (p < 0.05), and LEDD was reduced from 650 mg (baseline) to 280 mg and 325 mg at 1 year post operation and the final follow-up, respectively (p < 0.05). One patient had a cortical hemorrhage in the puncture tract on day 2 after surgery, five patients had hallucinations in the acute stage after surgery, and one patient had an exposed left-brain electrode lead at 4 months post operation; there were no infections or death. Conclusion: DBS showed efficacy and safety in treating older patients (≥75 years old) with Parkinson’s disease. Motor function, quality of life, activities of daily living, LEDD, and sleep all showed long-term improvements with DBS; short-term improvements in emotional and cognitive function were also noted.

Long-term efficacy, prognostic factors, and safety of deep brain stimulation in patients with refractory Tourette syndrome: A single center, single target, retrospective study

BACKGROUND

To evaluate the long-term efficacy, prognostic factors, and safety of posteroventral globus pallidus internus deep brain stimulation (DBS) in patients with refractory Tourette syndrome (RTS).

METHODS

This retrospective study recruited 61 patients with RTS who underwent posteroventral globus pallidus internus (GPi) DBS from January 2010 to December 2020 at the Chinese People's Liberation Army General Hospital. The Yale Global Tic Severity Scale (YGTSS), Yale-Brown Obsessive-Compulsive Scale (YBOCS), Beck Depression Inventory (BDI), Gilles de la Tourette Syndrome Quality-of-Life Scale (GTS-QOL) were used to evaluate the preoperative and postoperative clinical condition in all patients. Prognostic factors and adverse events following surgery were analyzed.

RESULTS

Patient follow up was conducted for an average of 73.33 ± 28.44 months. The final postoperative YGTSS (32.39 ± 22.34 vs 76.61 ± 17.07), YBOCS (11.26 ± 5.57 vs 18.31 ± 8.55), BDI (14.36 ± 8.16 vs 24.79 ± 11.03) and GTS-QOL (39.69 ± 18.29 vs 78.08 ± 14.52) scores at the end of the follow-up period were significantly lower than those before the surgery (p < 0.05). While age and the duration of follow-up were closely related to prognosis, the disease duration and gender were not. No serious adverse events were observed and only one patient exhibited symptomatic deterioration.

CONCLUSIONS

Posteroventral-GPI DBS provides long-term effectiveness, acceptable safety and can improve the quality of life in RTS patients. Moreover, DBS is more successful among younger patients and with longer treatment duration.

Empirically Comparing Magnetic Needle Steering Models Using Expectation-Maximization

Straight-line needle insertion is a prevalent tool in surgical interventions in the brain, such as Deep Brain Stimulation and Convection-Enhanced Delivery, that treat a range of conditions from Alzheimer’s disease to brain cancer. Using a steerable needle to execute curved trajectories and correct positional deviation could enable more intervention possibilities, while reducing the risk of complication in these procedures. This paper experimentally identifies model parameters using an expectation-maximization (EM) algorithm for two different steerable needle models. The results compared a physically motivated model to the established bicycle needle model and found the former to be preferred for modeling soft brain tissue needle insertion. The results also supported the experimentally parameterized models’ use in future applications such as needle steering control.

BOLD Monitoring in the Neural Simulator ANNarchy

Multi-scale network models that simultaneously simulate different measurable signals at different spatial and temporal scales, such as membrane potentials of single neurons, population firing rates, local field potentials, and blood-oxygen-level-dependent (BOLD) signals, are becoming increasingly popular in computational neuroscience. The transformation of the underlying simulated neuronal activity of these models to simulated non-invasive measurements, such as BOLD signals, is particularly relevant. The present work describes the implementation of a BOLD monitor within the neural simulator ANNarchy to allow an on-line computation of simulated BOLD signals from neural network models. An active research topic regarding the simulation of BOLD signals is the coupling of neural processes to cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO2). The flexibility of ANNarchy allows users to define this coupling with a high degree of freedom and thus, not only allows to relate mesoscopic network models of populations of spiking neurons to experimental BOLD data, but also to investigate different hypotheses regarding the coupling between neural processes, CBF and CMRO2 with these models. In this study, we demonstrate how simulated BOLD signals can be obtained from a network model consisting of multiple spiking neuron populations. We first demonstrate the use of the Balloon model, the predominant model for simulating BOLD signals, as well as the possibility of using novel user-defined models, such as a variant of the Balloon model with separately driven CBF and CMRO2 signals. We emphasize how different hypotheses about the coupling between neural processes, CBF and CMRO2 can be implemented and how these different couplings affect the simulated BOLD signals. With the BOLD monitor presented here, ANNarchy provides a tool for modelers who want to relate their network models to experimental MRI data and for scientists who want to extend their studies of the coupling between neural processes and the BOLD signal by using modeling approaches. This facilitates the investigation and model-based analysis of experimental BOLD data and thus improves multi-scale understanding of neural processes in humans.

Microstimulation Is a Promising Approach in Achieving Better Lead Placement in Subthalamic Nucleus Deep Brain Stimulation Surgery

Background: The successful application of subthalamic nucleus (STN) deep brain stimulation (DBS) surgery relies mostly on optimal lead placement, whereas the major challenge is how to precisely localize STN. Microstimulation, which can induce differentiating inhibitory responses between STN and substantia nigra pars reticulata (SNr) near the ventral border of STN, has indicated a great potential of breaking through this barrier. Objective: This study aims to investigate the feasibility of localizing the boundary between STN and SNr (SSB) using microstimulation and promote better lead placement. Methods: We recorded neurophysiological data from 41 patients undergoing STN-DBS surgery with microstimulation in our hospital. Trajectories with typical STN signal were included. Microstimulation was applied near the bottom of STN to determine SSB, which was validated by the imaging reconstruction of DBS leads. Results: In most trajectories with microstimulation (84.4%), neuronal firing in STN could not be inhibited by microstimulation, whereas in SNr long inhibition was observed following microstimulation. The success rate of localizing SSB was significantly higher in trajectories with microstimulation than those without. Moreover, results from imaging reconstruction and intraoperative neurological assessments demonstrated better lead location and higher therapeutic effectiveness in trajectories with microstimulation and accurately identified SSB. Conclusion: Microstimulation on microelectrode recording is an effective approach to localize the SSB. Our data provide clinical evidence that microstimulation can be routinely employed to achieve better lead placement.

Estimating the Risk of Deep Brain Stimulation in the Modern Era: 2008 to 2020

BACKGROUND

Deep brain stimulation (DBS) was first approved by the United States Food and Drug Administration in 1997. Although the fundamentals of DBS remain the same, hardware, software, and imaging have evolved significantly.

OBJECTIVE

To test our hypothesis that the aggregate complication rate in the medical literature in the past 12 years would be lower than what is often cited based on early experience with DBS surgery.

METHODS

PubMed, PsycINFO, and EMBASE were queried for studies from 2008 to 2020 that included patients treated with DBS from 2007 to 2019. This yielded 34 articles that evaluated all complications of DBS surgery, totaling 2249 patients.

RESULTS

The overall complication rate in this study was 16.7% per patient. There was found to be a systemic complication rate of 0.89%, intracranial complication rate of 2.7%, neurological complication rate of 4.6%, hardware complication rate of 2.2%, and surgical site complication rate of 3.4%. The infection and erosion rate was 3.0%.

CONCLUSION

This review suggests that surgical complication rates have decreased since the first decade after DBS was first FDA approved. Understanding how to minimize complications from the inception of a technique should receive more attention.

Vertical open-bore MRI scanners generate significantly less radiofrequency heating around implanted leads: A study of deep brain stimulation implants in 1.2T OASIS scanners versus 1.5T horizontal systems

PURPOSE

Patients with active implants such as deep brain stimulation (DBS) devices are often denied access to MRI due to safety concerns associated with the radiofrequency (RF) heating of their electrodes. The majority of studies on RF heating of conductive implants have been performed in horizontal close-bore MRI scanners. Vertical MRI scanners which have a 90° rotated transmit coil generate fundamentally different electric and magnetic field distributions, yet very little is known about RF heating of implants in this class of scanners. We performed numerical simulations as well as phantom experiments to compare RF heating of DBS implants in a 1.2T vertical scanner (OASIS, Hitachi) compared to a 1.5T horizontal scanner (Aera, Siemens).

METHODS

Simulations were performed on 90 lead models created from post-operative CT images of patients with DBS implants. Experiments were performed with wires and commercial DBS devices implanted in an anthropomorphic phantom.

RESULTS

We found significant reduction of 0.1 g-averaged specific absorption rate (30-fold, P < 1 × 10^-5 ) and RF heating (9-fold, P < .026) in the 1.2T vertical scanner compared to the 1.5T conventional scanner.

CONCLUSION

Vertical MRI scanners appear to generate lower RF heating around DBS leads, providing potentially heightened safety or the flexibility to use sequences with higher power levels than on conventional systems.

Intraoperative MRI versus 5-ALA in high-grade glioma resection: a network meta-analysis

OBJECTIVE

High-grade gliomas (HGGs) continue to carry poor prognoses, and patient outcomes depend heavily on the extent of resection (EOR). The utility of conventional image-guided surgery is limited by intraoperative brain shift. More recent techniques to maximize EOR, including intraoperative imaging and the use of fluorescent dyes, combat these limitations. However, the relative efficacy of these two techniques has never been systematically compared. Thus, the authors performed an exhaustive systematic review in conjunction with quantitative network meta-analyses to evaluate the comparative effectiveness of 5-aminolevulinic acid (5-ALA) and intraoperative MRI (IMRI) in optimizing EOR in HGG. They secondarily analyzed associated progression-free and overall survival and performed subgroup analyses by level of evidence.

METHODS

PubMed, Embase, Cochrane Central, and Web of Science were searched for studies evaluating conventional neuronavigation, IMRI, and 5-ALA in HGG resection. The primary study endpoint was the proportion of patients attaining gross-total resection (GTR), defined as 100% elimination of contrast-enhancing lesion on postoperative MRI. Secondary endpoints included overall and progression-free survival and subgroup analyses for level of evidence. Comparative efficacy analysis of IMRI and 5-ALA was performed using Bayesian network meta-analysis models.

RESULTS

This analysis included 11 studies. In a classic meta-analysis, both IMRI (OR 4.99, 95% CI 2.65-9.39, p < 0.001) and 5-ALA (OR 2.866, 95% CI 2.127-3.863, p < 0.001) were superior to conventional navigation in achieving GTR. Bayesian network analysis was employed to indirectly compare IMRI to 5-ALA, and no significant difference in GTR was found between the two (OR 1.9 favoring IMRI, 95% CI 0.905-3.989, p = 0.090). A handful of studies additionally suggested that the use of either IMRI (2 and 4 studies, respectively) or 5-ALA (2 and 2 studies, respectively) improves progression-free and overall survival.

CONCLUSIONS

IMRI and 5-ALA are individually superior to conventional neuronavigation for achieving GTR of HGG. Between IMRI and 5-ALA, neither method is clearly more effective. Future studies evaluating the comparative cost and surgical time associated with IMRI and 5-ALA will better inform any cost-benefit analysis.

Deep Brain Stimulation in Alzheimer's Disease: Targeting the Nucleus Basalis of Meynert

Alzheimer's disease (AD) is becoming a prevalent disease in the elderly population. Past decades have witnessed the development of drug therapies with varying targets. However, all drugs with a single molecular target fail to reverse or ameliorate AD progression, which ultimately results in cortical and subcortical network dysregulation. Deep brain stimulation (DBS) has been proven effective for the treatment of Parkinson's disease, essential tremor, and other neurological diseases. As such, DBS has also been gradually acknowledged as a potential therapy for AD. The current review focuses on DBS of the nucleus basalis of Meynert (NBM). As a critical component of the cerebral cholinergic system and the Papez circuit in the basal ganglia, the NBM plays an indispensable role in the subcortical regulation of memory, attention, and arousal state, which makes the NBM a promising target for modulation of neural network dysfunction and AD treatment. We summarized the intricate projection relations and functionality of the NBM, current approaches for stereotactic localization and evaluation of the NBM, and the therapeutic effects of NBM-DBS both in patients and animal models. Furthermore, the current shortcomings of NBM-DBS, such as variations in cortical blood flow, increased temperature in the target area, and stimulation-related neural damage, were presented.

O-Arm Stereotactic Imaging in Deep Brain Stimulation Surgery Workflow: A Utility and Cost-Effectiveness Analysis

INTRODUCTION

Deep brain stimulation (DBS) surgery is an established treatment for movement disorders. Advances in neuroimaging techniques have resulted in improved targeting accuracy that may improve clinical outcomes. This study aimed to evaluate the safety and feasibility of using the Medtronic O-arm device for the acquisition of intraoperative stereotactic imaging, targeting, and localization of DBS electrodes compared with standard stereotactic MRI or computed tomography (CT).

METHODS

Patients were recruited prospectively into the study. Routine frame-based stereotactic DBS surgery was performed. Intraoperative imaging was used to facilitate and verify the accurate placement of the intracranial electrodes. The acquisition of coordinates and verification of the position of the electrodes using the O-arm were evaluated and compared with conventional stereotactic MRI or CT. Additionally, a systematic review of the literature on the use of intraoperative imaging in DBS surgery was performed.

RESULTS

Eighty patients were included. The indications for DBS surgery were dystonia, Parkinson's disease, essential tremor, and epilepsy. The globus pallidus internus was the most commonly targeted region (43.7%), followed by the subthalamic nucleus (35%). Stereotactic O-arm imaging reduced the overall surgical time by 68 min, reduced the length of time of acquisition of stereotactic images by 77%, reduced patient exposure to ionizing radiation by 24.2%, significantly reduced operating room (OR) costs per procedure by 31%, and increased the OR and neuroradiology suite availability.

CONCLUSIONS

The use of the O-arm in DBS surgery workflow significantly reduced the duration of image acquisition, the exposure to ionizing radiation, and costs when compared with standard stereotactic MRI or CT, without reducing accuracy.

Intraoperative Neurophysiologic Assessment in Deep Brain Stimulation Surgery and its Impact on Lead Placement

OBJECTIVES

 While the efficacy of deep brain stimulation (DBS) to treat various neurological disorders is undisputed, the surgical methods differ widely and the importance of intraoperative microelectrode recording (MER) or macrostimulation (MS) remains controversially debated. The objective of this study is to evaluate the impact of MER and MS on intraoperative lead placement.

PATIENTS AND METHODS

 We included 101 patients who underwent awake bilateral implantation of electrodes in the subthalamic nucleus with MER and MS for Parkinson's disease from 2009 to 2017 in a retrospective observational study. We analyzed intraoperative motor outcomes between anatomically planned stimulation point (PSP) and definite stimulation point (DSP), lead adjustments and Unified Parkinson's Disease Rating Scale Item III (UPDRS-III), levodopa equivalent daily dose (LEDD), and adverse events (AE) after 6 months.

RESULTS

 We adjusted 65/202 leads in 47/101 patients. In adjusted leads, MS results improved significantly when comparing PSP and DSP (p < 0.001), resulting in a number needed to treat of 9.6. After DBS, UPDRS-III and LEDD improved significantly after 6 months in adjusted and nonadjusted patients (p < 0.001). In 87% of leads, the active contact at 6 months still covered the optimal stimulation point during surgery. In total, 15 AE occurred.

CONCLUSION

 MER and MS have a relevant impact on the intraoperative decision of final lead placement and prevent from a substantial rate of poor stimulation outcome. The optimal stimulation points during surgery and chronic stimulation strongly overlap. Follow-up UPDRS-III results, LEDD reductions, and DBS-related AE correspond well to previously published data.

A comparative study of asleep and awake deep brain stimulation robot-assisted surgery for Parkinson's disease

To compare the differences between asleep and awake robot-assisted deep brain stimulation (DBS) surgery for Parkinson’s Disease (PD), we conducted this retrospective cohort study included 153 PD patients undergoing bilateral robot-assisted DBS from June 2017 to August 2019, of which 58 cases were performed under general anesthesia (GA) and 95 cases under local anesthesia (LA). Procedure duration, stimulation parameters, electrode implantation accuracy, intracranial air, intraoperative electrophysiological signal length, complications, and Unified PD Rating Scale (UPDRS) measurements were recorded and compared. The clinical evaluation was conducted by two raters who were blinded to the choice of anesthesia. Procedure duration was significantly shorter in the GA group, while on stimulation off medication motor scores (UPDRS-III) were significantly improved in both the GA and LA group. ANCOVA covariated for the baseline UPDRS-III and levodopa challenge exhibited no significant differences. In terms of amplitude, frequency, and pulse width, the stimulation parameters used for DBS power-on were similar. There were no significant differences in electrode implantation accuracy, intraoperative electrophysiological signal length, or intracerebral hemorrhage (no occurrences in either group). The pneumocephalus volume was significantly smaller in the GA group. Six patients exhibited transient throat discomfort associated with tracheal intubation in the GA group. The occurrence of surgical incision infection was similar in both groups. Compared with the awake group, the asleep group exhibited a shorter procedure duration with a similar electrode implantation accuracy and short-term motor improvement. Robot-assisted asleep DBS surgery is a promising surgical method for PD.

Stimulation-Induced Dyskinesia After Subthalamic Nucleus Deep Brain Stimulation in Patients With Meige Syndrome

OBJECTIVES

Deep brain stimulation of the subthalamic nucleus (STN-DBS) is increasingly used to treat Meige syndrome (MS) and markedly improves symptoms. Stimulation-induced dyskinesia (SID), which adversely affects surgical outcomes and patient satisfaction, may, however, occur in some patients. This study attempts to explore possible causes of SID.

MATERIALS AND METHODS

Retrospectively collected clinical data on 32 patients who underwent STN-DBS between October 2016 and April 2019 were analyzed. Clinical outcomes were assessed pre- and post-surgery, using the Burke-Fahn-Marsden dystonia rating scale (BFMDRS). Patients were divided into a dyskinesia group and a non-dyskinesia group, according to whether or not they experienced persistent SID during follow-up. The coordinates of the active contacts were calculated from post-operative computerized tomography or magnetic resonance imaging, using the inter-commissural line as a reference. At final follow-up, the main stimulatory parameters for further study included pulse width, voltage, and frequency.

RESULTS

At final follow-up (mean = 16.3 ± 7.2 months), MS patients had improved BFMDRS total scores compared with pre-surgical scores (mean improvement = 79.0%, p < 0.0001). The mean improvement in BFMDRS total scores in the dyskinesia (n = 10) and non-dyskinesia (n = 22) groups were 81.6 ± 8.8% and 77.9 ± 14.2%, respectively. The mean minimum voltage to induce dyskinesia was 1.7 ± 0.3 V. The programmed parameters of both groups were similar. When compared with the non-dyskinesia group, active stimulatory contact coordinates in the dyskinesia group were inferior (mean left side: z = -2.3 ± 1.7 mm vs. z = -1.2 ± 1.5 mm; p = 0.0282; mean right side: z = -2.7 ± 1.9 mm vs. z = -2.3 ± 1.7 mm; p = 0.0256). The x and y coordinates were similar.

CONCLUSION

STN-DBS is an effective intervention for MS, providing marked improvements in clinical symptoms; SID may, however occur in the subsequent programming control process. Comparing patients with/without dyskinesia, the active contacts were located closer to the inferior part of the STN in patients with dyskinesia, which may provide an explanation for the dyskinesia.

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.

Image Guidance in Deep Brain Stimulation Surgery to Treat Parkinson's Disease: A Comprehensive Review

Deep brain stimulation (DBS) is an effective therapy as an alternative to pharmaceutical treatments for Parkinson's disease (PD). Aside from factors such as instrumentation, treatment plans, and surgical protocols, the success of the procedure depends heavily on the accurate placement of the electrode within the optimal therapeutic targets while avoiding vital structures that can cause surgical complications and adverse neurologic effects. Although specific surgical techniques for DBS can vary, interventional guidance with medical imaging has greatly contributed to the development, outcomes, and safety of the procedure. With rapid development in novel imaging techniques, computational methods, and surgical navigation software, as well as growing insights into the disease and mechanism of action of DBS, modern image guidance is expected to further enhance the capacity and efficacy of the procedure in treating PD. This article surveys the state-of-the-art techniques in image-guided DBS surgery to treat PD, and discusses their benefits and drawbacks, as well as future directions on the topic.

A Review on Advances in Intra-operative Imaging for Surgery and Therapy: Imagining the Operating Room of the Future

With the advent of Minimally Invasive Surgery (MIS), intra-operative imaging has become crucial for surgery and therapy guidance, allowing to partially compensate for the lack of information typical of MIS. This paper reviews the advancements in both classical (i.e. ultrasounds, X-ray, optical coherence tomography and magnetic resonance imaging) and more recent (i.e. multispectral, photoacoustic and Raman imaging) intra-operative imaging modalities. Each imaging modality was analyzed, focusing on benefits and disadvantages in terms of compatibility with the operating room, costs, acquisition time and image characteristics. Tables are included to summarize this information. New generation of hybrid surgical room and algorithms for real time/in room image processing were also investigated. Each imaging modality has its own (site- and procedure-specific) peculiarities in terms of spatial and temporal resolution, field of view and contrasted tissues. Besides the benefits that each technique offers for guidance, considerations about operators and patient risk, costs, and extra time required for surgical procedures have to be considered. The current trend is to equip surgical rooms with multimodal imaging systems, so as to integrate multiple information for real-time data extraction and computer-assisted processing. The future of surgery is to enhance surgeons eye to minimize intra- and after-surgery adverse events and provide surgeons with all possible support to objectify and optimize the care-delivery process.

Intraoperative fiber optic guidance during chronic electrode implantation in deep brain stimulation neurosurgery: proof of concept in primates

OBJECTIVE

The clinical outcome of deep brain stimulation (DBS) surgery relies heavily on the implantation accuracy of a chronic stimulating electrode into a small target brain region. Most techniques that have been proposed to precisely target these deep brain regions were designed to map intracerebral electrode trajectory prior to chronic electrode placement, sometimes leading to positioning error of the final electrode. This study was designed to create a new intraoperative guidance tool for DBS neurosurgery that can improve target detection during the final implantation of the chronic electrode.

METHODS

Taking advantage of diffuse reflectance spectroscopy, the authors developed a new surgical tool that senses proximal brain tissue through the tip of the chronic electrode by means of a novel stylet, which provides rigidity to DBS leads and houses fiber optics.

RESULTS

As a proof of concept, the authors demonstrated the ability of their noninvasive optical guidance technique to precisely locate the border of the subthalamic nucleus during the implantation of commercially available DBS electrodes in anesthetized parkinsonian monkeys. Innovative optical recordings combined to standard microelectrode mapping and detailed postmortem brain examination allowed the authors to confirm the precision of optical target detection. They also show the optical technique's ability to detect, in real time, upcoming blood vessels, reducing the risk of hemorrhage during the chronic lead implantation.

CONCLUSIONS

The authors present a new optical guidance technique that can detect target brain regions during DBS surgery from within the implanted electrode using a proof of concept in nonhuman primates. The technique discriminates tissue in real time, contributes no additional invasiveness to the procedure by being housed within the electrode, and can provide complementary information to microelectrode mapping during the implantation of the chronic electrode. The technique may also be a powerful tool for providing direct anatomical information in the case of direct implantations wherein microelectrode mapping is not performed.

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.

Early detection of cerebral ischemic events on intraoperative magnetic resonance imaging during surgical procedures for deep brain stimulation

BACKGROUND

Although intracerebral hemorrhage is the most feared complication of deep brain stimulation (DBS) surgery, cerebral ischemic events in association with DBS surgery have only rarely been described. We therefore evaluated the role of intraoperative MRI (iMRI) for early identification of cerebral ischemic events during DBS procedures and determined how ischemic infarctions affect patients over acute and long-term periods.

METHODS

Between January 2010 and December 2017, 1160 DBS electrodes were implanted in 595 patients at Chinese People's Liberation Army General Hospital, with the help of iMRI. The iMRI was performed in all patients after implantation, to define the accuracy of lead placement and detect complications. A CT scan was performed on postoperative days 1 to 7.

RESULTS

The iMRI showed that cerebral ischemic changes happened in nine (1.51% of patients, 0.78% of leads) patients. Only two (0.34%) of nine patients had an ischemic infarction in the basal ganglia, while seven (1.18%) had cortical ischemia. Six (67%) of the nine patients had long-term complications, two with mild hemiparesis, two with seizures, one with language dysfunction, and one with memory loss. Of those with a cortical ischemic infarction, only three (42.86%) of seven patients had no long-term complications. Long-term follow-up imaging showed that not all the patients recovered normal morphological structure in the area of ischemic foci. The factors of sex, age, target, and anesthesia were not related to ischemic events. In six (66.7%) cases, the entry point on the cortex or the path was not ideal.

CONCLUSIONS

Intraoperative ischemic events are not uncommon in DBS surgery. Ischemia can cause serious permanent complications, and regions subject to severe ischemia cannot be restored; it is therefore necessary to pay careful attention to any signs of ischemia. iMRI objectively provides the basis for early diagnosis of intraoperative ischemic infarction, providing guidance for follow-up treatment. The deviation in the entry point on the cortex or in the path resulted in vascular injury; it may be the key cause of ischemic events during DBS procedures.

Neural Circuit and Clinical Insights from Intraoperative Recordings During Deep Brain Stimulation Surgery

Observations using invasive neural recordings from patient populations undergoing neurosurgical interventions have led to critical breakthroughs in our understanding of human neural circuit function and malfunction. The opportunity to interact with patients during neurophysiological mapping allowed for early insights in functional localization to improve surgical outcomes, but has since expanded into exploring fundamental aspects of human cognition including reward processing, language, the storage and retrieval of memory, decision-making, as well as sensory and motor processing. The increasing use of chronic neuromodulation, via deep brain stimulation, for a spectrum of neurological and psychiatric conditions has in tandem led to increased opportunity for linking theories of cognitive processing and neural circuit function. Our purpose here is to motivate the neuroscience and neurosurgical community to capitalize on the opportunities that this next decade will bring. To this end, we will highlight recent studies that have successfully leveraged invasive recordings during deep brain stimulation surgery to advance our understanding of human cognition with an emphasis on reward processing, improving clinical outcomes, and informing advances in neuromodulatory interventions.

Long-term Results for Single Channel-Guided Deep Brain Stimulation Used to Treat Parkinson's Disease

Introduction

The optimal method for targeting the subthalamic nucleus (STN) and positioning the deep brain stimulation (DBS) electrode is still controversial. In this study, single channel-guided stimulations were used in order to determine the most proper way to target the STN. Findings were synthesised for use in clinical situations. This paper presents the long-term results of DBS applied using single-channel guidance.

Methods

We retrospectively reviewed 15 patients who had undergone STN-DBS to treat Parkinson's disease in-between 2010 and 2017. All patients were examined preoperatively, and they were routinely followed-up 2-7 years postoperatively.

Results

The use of single-channel guidance resulted in better outcomes of motor complaints of Parkinson's patients. Moreover, a significantly greater improvement in Unified Parkinson's Disease Rating Scale Score (UPDRS) was achieved in either ON or OFF periods of patients.

Conclusion

Single channel-guided STN-DBS is a safe procedure and it results in improved motor outcomes in advanced Parkinson's Disease.

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.

MR-Guided Functional Neurosurgery: Laser Ablation and Deep Brain Stimulation

Intraoperative magnetic resonance imaging (iMRI) is increasingly implemented for image-guided procedures in functional neurosurgery. iMRI facilitates accurate electrode implantation for deep brain stimulation (DBS) and is currently an alternative method for DBS electrode targeting. The application of iMRI also allows for greater accuracy and precision in laser-induced thermal therapy (LITT). The expanding use of functional neurosurgical procedures makes safety and feasibility of iMRI important considerations, particularly in patients with comorbidities or complex medical histories. We review here the applications of iMRI and discuss its safety, feasibility, and limitations in functional neurosurgery.To motivate discussion of this topic, we also present a 52-year-old patient with an implanted cardioverter-defibrillator (ICD) who successfully underwent iMRI-guided DBS electrode implantation for advanced Parkinson disease (PD). Neither iMRI nor the passage of electrical current through the implanted DBS electrodes demonstrated detectable interference in ICD function. This case demonstrates that, even in complex clinical contexts, iMRI is a promising tool that merits further exploration for procedures requiring highly accurate and precise identification of target structures.

Intra-operative characterisation of subthalamic oscillations in Parkinson's disease

OBJECTIVE

This study aims to use the activities recorded directly from the deep brain stimulation (DBS) electrode to address the focality and distinct nature of the local field potential (LFP) activities of different frequency.

METHODS

Pre-operative and intra-operative magnetic resonance imaging (MRI) were acquired from patients with Parkinson's disease (PD) who underwent DBS in the subthalamic nucleus and intra-operative LFP recording at rest and during cued movements. Images were reconstructed and 3-D visualized using Lead-DBS® toolbox to determine the coordinates of contact. The resting spectral power and movement-related power modulation of LFP oscillations were estimated.

RESULTS

Both subthalamic LFP activity recorded at rest and its modulation by movement had focal maxima in the alpha, beta and gamma bands. The spatial distribution of alpha band activity and its modulation was significantly different to that in the beta band. Moreover, there were significant differences in the scale and timing of movement related modulation across the frequency bands.

CONCLUSION

Subthalamic LFP activities within specific frequency bands can be distinguished by spatial topography and pattern of movement related modulation.

SIGNIFICANCE

Assessment of the frequency, focality and pattern of movement related modulation of subthalamic LFPs reveals a heterogeneity of neural population activity in this region. This could potentially be leveraged to finesse intra-operative targeting and post-operative contact selection.

Post-Operative Localization of Deep Brain Stimulation Electrodes in the Subthalamus Using Transcranial Sonography

OBJECTIVES

The correct positioning of deep brain stimulation electrodes determines the success of surgery. In this study, we attempt to validate transcranial sonography (TCS) as a method for early postoperative confirmation of electrode location in the subthalamic nucleus (STN).

MATERIALS AND METHODS

Nineteen patients diagnosed with Parkinson's disease were enrolled in the study. Postoperative TCS was applied to measure the distance between the implanted electrodes and the third ventricle in the axial plane. Whether the electrodes were positioned within or outside the substantia nigra (SN) was evaluated through measurements in the coronal plane. The obtained metrics through TCS were compared with those from postoperative computed tomography (CT) and magnetic resonance imaging (MRI).

RESULTS

A statistically significant correlation between distances from electrode to third ventricle by TCS and CT/MRI (r = 0.75, p < 0.01) was observed. Distances from third ventricle to electrodes tips were different when sonographically they showed to be inside or outside the SN (p < 0.01). A cut-off value of 8.85mm in these distances was the most sensitive (100%) and specific (90.5%) to predict if electrodes were positioned inside the SN (CI 95% 0.81-10.30, p = 0.001).

CONCLUSIONS

Transcranial sonography is a useful technique to reliably identify targeted positioning of deep brain stimulation electrodes in or out of the SN.

Image guidance based on MRI for spinal interstitial laser thermotherapy: technical aspects and accuracy

OBJECTIVE

Image guidance for spinal procedures is based on 3D-fluoroscopy or CT, which provide poor visualization of soft tissues, including the spinal cord. To overcome this limitation, the authors developed a method to register intraoperative MRI (iMRI) of the spine into a neuronavigation system, allowing excellent visualization of the spinal cord. This novel technique improved the accuracy in the deployment of laser interstitial thermal therapy probes for the treatment of metastatic spinal cord compression.

METHODS

Patients were positioned prone on the MRI table under general anesthesia. Fiducial markers were applied on the skin of the back, and a plastic cradle was used to support the MRI coil. T2-weighted MRI sequences of the region of interest were exported to a standard navigation system. A reference array was sutured to the skin, and surface matching of the fiducial markers was performed. A navigated Jamshidi needle was advanced until contact was made with the dorsal elements; its position was confirmed with intraoperative fluoroscopy prior to advancement into a target in the epidural space. A screenshot of its final position was saved, and then the Jamshidi needle was exchanged for an MRI-compatible access cannula. MRI of the exact axial plane of each access cannula was obtained and compared with the corresponding screenshot saved during positioning. The discrepancy in millimeters between the trajectories was measured to evaluate accuracy of the image guidance

RESULTS

Thirteen individuals underwent implantation of 47 laser probes. The median absolute value of the discrepancy between the location predicted by the navigation system and the actual position of the access cannulas was 0.7 mm (range 0–3.2 mm). No injury or adverse event occurred during the procedures.

CONCLUSIONS

This study demonstrates the feasibility of image guidance based on MRI to perform laser interstitial thermotherapy of spinal metastasis. The authors' method permits excellent visualization of the spinal cord, improving safety and workflow during laser ablations in the epidural space. The results can be extrapolated to other indications, including biopsies or drainage of fluid collections near the spinal cord.

Altered emotional prosody processing in patients with Parkinson's disease after subthalamic nucleus stimulation

BACKGROUND

Patients with Parkinson's disease (PD) exhibit deficits in recognizing and expressing vocal emotional prosody. The aim of this study was to explore emotional prosody processing in patients with PD shortly after subthalamic nucleus (STN) deep brain stimulation (DBS).

METHODS

Two groups of patients with PD (pre-DBS and post-DBS) and one healthy control (HC) group were recruited as participants. All participants (PD and HC) were assessed using the Montreal Affective Voices database 50 Voices Recognition test. All participants were asked to nonverbally express five basic emotions (happiness, anger, fear, sadness, and neutral) to test emotional prosody expression. Fifteen native Chinese speakers were recruited as raters. We recorded the accuracy rate, reaction time, confidence level, and two acoustic parameters (mean pitch and mean intensity).

RESULTS

The PD groups scored lower than the HC group in recognizing and expressing emotional prosody. STN DBS had no significant effect on the recognition of emotional prosody but had a significant effect on fear prosody expression. Pearson's correlation analysis revealed significant correlations between performance on emotional prosody recognition tests and performance on emotional prosody expression tests in both the pre-DBS PD and post-DBS PD groups.

CONCLUSION

Shortly after STN DBS, the ability to recognize emotional prosody was not altered, but fear expression was impaired. We identified associations between abnormalities in emotional prosody recognition and expression deficits both before and after STN DBS, indicating that the processes involved in recognizing and expressing emotional prosody may share a common system.

Post-operative imaging in deep brain stimulation: A controversial issue

In deep brain stimulation (DBS), post-operative imaging has been used on the one hand to assess complications, such as haemorrhage; and on the other hand, to detect misplaced contacts. The post-operative determination of the accurate location of the final electrode plays a critical role in evaluating the precise area of effective stimulation and for predicting the potential clinical outcome; however, safety remains a priority in postoperative DBS imaging. A plethora of diverse post-operative imaging methods have been applied at different centres. There is neither a consensus on the most efficient post-operative imaging methodology, nor is there any standardisation for the automatic or manual analysis of the images within the different imaging modalities. In this article, we give an overview of currently applied post-operative imaging modalities and discuss the current challenges in post-operative imaging in DBS.