Moving forward: advances in the treatment of movement disorders with deep brain stimulation

Treatment of wound infections linked to neurosurgical implants

As neurosurgery has advanced technologically, more and more neurosurgical implants are being employed on an aging patient population with several comorbidities. As a result, there is a steady increase in the frequency of infections linked to neurosurgical implants, which causes serious morbidity and mortality as well as abnormalities of the skull and inadequate brain protection. We discuss infections linked to internal and external ventricular and lumbar cerebrospinal fluid drainages, neurostimulators, craniotomies, and cranioplasty in this article. Biofilms, which are challenging to remove, are involved in all implant-associated illnesses. It takes a small quantity of microorganisms to create a biofilm on the implant surface. Skin flora bacteria are implicated in the majority of illnesses. Microorganisms that cause disruptions in wound healing make their way to the implant either during or right after surgery. In about two thirds of patients, implant-associated infections manifest early (within the first month after surgery), whereas the remaining infections present later as a result of low-grade infections or by direct extension from adjacent infections (per continuitatem) to the implants due to soft tissue damage. Except for ventriculo-atrial cerebrospinal fluid shunts, neurosurgical implants are rarely infected by the haematogenous route. This research examines established and clinically validated principles that are applicable to a range of surgical specialties using implants to treat biofilm-associated infections in orthopaedic and trauma cases. Nevertheless, there is little evidence and no evaluation in sizable patient populations to support the success of this extrapolation to neurosurgical patients. An optimal microbiological diagnostic, which includes sonicating removed implants and extending culture incubation times, is necessary for a positive result. Additionally, a strategy combining surgical and antibiotic therapy is needed. Surgical procedures involve a suitable debridement along with implant replacement or exchange, contingent on the biofilm's age and the state of the soft tissue. A protracted biofilm-active therapy is a component of antimicrobial treatment, usually lasting 4-12 weeks. This idea is appealing because it allows implants to be changed or kept in place for a single surgical procedure in a subset of patients. This not only enhances quality of life but also lowers morbidity because each additional neurosurgical procedure increases the risk of secondary complications like intracerebral bleeding or ischemia.

Deep brain stimulation for movement disorders after stroke: a systematic review of the literature

OBJECTIVE

Stroke remains the leading cause of disability in the United States. Even as acute care for strokes advances, there are limited options for improving function once the patient reaches the subacute and chronic stages. Identification of new therapeutic approaches is critical. Deep brain stimulation (DBS) holds promise for these patients. A number of case reports and small case series have reported improvement in movement disorders after strokes in patients treated with DBS. In this systematic review, the authors have summarized the patient characteristics, anatomical targets, stimulation parameters, and outcomes of patients who have undergone DBS treatment for poststroke movement disorders.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. The PubMed, Scopus, and SpringerLink databases were searched for the keywords "DBS," "stroke," "movement," and "recovery" to identify patients treated with DBS for movement disorders after a stroke. The Joanna Briggs Institute Critical Appraisal checklists for case reports and case series were used to systematically analyze the quality of the included studies. Data collected from each study included patient demographic characteristics, stroke diagnosis, movement disorder, DBS target, stimulation parameters, complications, and outcomes.

RESULTS

The authors included 29 studies that described 53 patients who underwent placement of 82 total electrodes. Movement disorders included tremor (n = 18), dystonia (n = 18), hemiballism (n = 6), spastic hemiparesis (n = 1), chorea (n = 1), and mixed disorders (n = 9). The most common DBS targets were the globus pallidus internus (n = 32), ventral intermediate nucleus of thalamus (n = 25), and subthalamic area/subthalamic nucleus (n = 7). Monopolar stimulation was reported in 43 leads and bipolar stimulation in 13. High-frequency stimulation was used in 57 leads and low-frequency stimulation in 6. All patients but 1 had improvement in their movement disorders. Two complications were reported: speech impairment in 1 patient and hardware infection in another. The median (interquartile range) duration between stroke and DBS treatment was 6.5 (2.1-15.8) years.

CONCLUSIONS

This is the first systematic review of DBS for poststroke movement disorders. Overall, most studies to date have been case reports and small series reporting heterogeneous patients and surgical strategies. This review suggests that DBS for movement disorders after a stroke has the potential to be effective and safe for diverse patients, and DBS may be a feasible option to improve function even years after a stroke.

Neurophysiological Basis of Deep Brain Stimulation and Botulinum Neurotoxin Injection for Treating Oromandibular Dystonia

Oromandibular dystonia (OMD) induces severe motor impairments, such as masticatory disturbances, dysphagia, and dysarthria, resulting in a serious decline in quality of life. Non-invasive brain-imaging techniques such as electroencephalography (EEG) and magnetoencephalography (MEG) are powerful approaches that can elucidate human cortical activity with high temporal resolution. Previous studies with EEG and MEG have revealed that movements in the stomatognathic system are regulated by the bilateral central cortex. Recently, in addition to the standard therapy of botulinum neurotoxin (BoNT) injection into the affected muscles, bilateral deep brain stimulation (DBS) has been applied for the treatment of OMD. However, some patients' OMD symptoms do not improve sufficiently after DBS, and they require additional BoNT therapy. In this review, we provide an overview of the unique central spatiotemporal processing mechanisms in these regions in the bilateral cortex using EEG and MEG, as they relate to the sensorimotor functions of the stomatognathic system. Increased knowledge regarding the neurophysiological underpinnings of the stomatognathic system will improve our understanding of OMD and other movement disorders, as well as aid the development of potential novel approaches such as combination treatment with BoNT injection and DBS or non-invasive cortical current stimulation therapies.

Past, Present, and Future of Deep Brain Stimulation: Hardware, Software, Imaging, Physiology and Novel Approaches

Deep brain stimulation (DBS) has advanced treatment options for a variety of neurologic and neuropsychiatric conditions. As the technology for DBS continues to progress, treatment efficacy will continue to improve and disease indications will expand. Hardware advances such as longer-lasting batteries will reduce the frequency of battery replacement and segmented leads will facilitate improvements in the effectiveness of stimulation and have the potential to minimize stimulation side effects. Targeting advances such as specialized imaging sequences and “connectomics” will facilitate improved accuracy for lead positioning and trajectory planning. Software advances such as closed-loop stimulation and remote programming will enable DBS to be a more personalized and accessible technology. The future of DBS continues to be promising and holds the potential to further improve quality of life. In this review we will address the past, present and future of DBS.

Randomized, Double-Blind Assessment of LFP Versus SUA Guidance in STN-DBS Lead Implantation: A Pilot Study

Background: The efficacy of deep brain stimulation (DBS) therapy in Parkinson's disease (PD) patients is highly dependent on the precise localization of the target structures such as subthalamic nucleus (STN). Most commonly, microelectrode single unit activity (SUA) recordings are performed to refine the target. This process is heavily experience based and can be technically challenging. Local field potentials (LFPs), representing the activity of a population of neurons, can be obtained from the same microelectrodes used for SUA recordings and allow flexible online processing with less computational complexity due to lower sampling rate requirements. Although LFPs have been shown to contain biomarkers capable of predicting patients' symptoms and differentiating various structures, their use in the localization of the STN in the clinical practice is not prevalent. Methods: Here we present, for the first time, a randomized and double-blinded pilot study with intraoperative online LFP processing in which we compare the clinical benefit from SUA- versus LFP-based implantation. Ten PD patients referred for bilateral STN-DBS were randomly implanted using either SUA or LFP guided targeting in each hemisphere. Although both SUA and LFP were recorded for each STN, the electrophysiologist was blinded to one at a time. Three months postoperatively, the patients were evaluated by a neurologist blinded to the intraoperative recordings to assess the performance of each modality. While SUA-based decisions relied on the visual and auditory inspection of the raw traces, LFP-based decisions were given through an online signal processing and machine learning pipeline. Results: We found a dramatic agreement between LFP- and SUA-based localization (16/20 STNs) providing adequate clinical improvement (51.8% decrease in 3-month contralateral motor assessment scores), with LFP-guided implantation resulting in greater average improvement in the discordant cases (74.9%, n = 3 STNs). The selected tracks were characterized by higher activity in beta (11-32 Hz) and high-frequency (200-400 Hz) bands (p < 0.01) of LFPs and stronger non-linear coupling between these bands (p < 0.05). Conclusion: Our pilot study shows equal or better clinical benefit with LFP-based targeting. Given the robustness of the electrode interface and lower computational cost, more centers can utilize LFP as a strategic feedback modality intraoperatively, in conjunction to the SUA-guided targeting.

Steerable Microinvasive Probes for Localized Drug Delivery to Deep Tissue

Enhanced understanding of neuropathologies has created a need for more advanced tools. Current neural implants result in extensive glial scarring and are not able to highly localize drug delivery due to their size. Smaller implants reduce surgical trauma and improve spatial resolution, but such a reduction requires improvements in device design to enable accurate and chronic implantation in subcortical structures. Flexible needle steering techniques offer improved control over implant placement, but often require complex closed-loop control for accurate implantation. This study reports the development of steerable microinvasive neural implants (S-MINIs) constructed from borosilicate capillaries (OD = 60 µm, ID = 20 µm) that do not require closed-loop guidance or guide tubes. S-MINIs reduce glial scarring 3.5-fold compared to prior implants. Bevel steered needles are utilized for open-loop targeting of deep-brain structures. This study demonstrates a sinusoidal relationship between implant bevel angle and the trajectory radius of curvature both in vitro and ex vivo. This relationship allows for bevel-tipped capillaries to be steered to a target with an average error of 0.23 mm ± 0.19 without closed-loop control. Polished microcapillaries present a new microinvasive tool for chronic, predictable targeting of pathophysiological structures without the need for closed-loop feedback and complex imaging.

Deep Brain Stimulation and Drug-Resistant Epilepsy: A Review of the Literature

Introduction: Deep brain stimulation is a safe and effective neurointerventional technique for the treatment of movement disorders. Electrical stimulation of subcortical structures may exert a control on seizure generators initiating epileptic activities. The aim of this review is to present the targets of the deep brain stimulation for the treatment of drug-resistant epilepsy. Methods: We performed a structured review of the literature from 1980 to 2018 using Medline and PubMed. Articles assessing the impact of deep brain stimulation on seizure frequency in patients with DRE were selected. Meta-analyses, randomized controlled trials, and observational studies were included. Results: To date, deep brain stimulation of various neural targets has been investigated in animal experiments and humans. This article presents the use of stimulation of the anterior and centromedian nucleus of the thalamus, hippocampus, basal ganglia, cerebellum and hypothalamus. Anterior thalamic stimulation has demonstrated efficacy and there is evidence to recommend it as the target of choice. Conclusion: Deep brain stimulation for seizures may be an option in patients with drug-resistant epilepsy. Anterior thalamic nucleus stimulation could be recommended over other targets.

Mapping the experiences and needs of deep brain stimulation for people with Parkinson’s disease and their family members

Background

Deep brain stimulation (DBS) is an effective treatment for the motor symptoms of Parkinson’s disease (PD). The lived experience of people with PD suggests a process of adjustment follows. This study aimed to explore the adjustment and associated education and support needs of people with PD undergoing DBS and their family members across the continuum of the DBS experience.

Method

A structured qualitative description study including semi-structured interviews with people with PD (n = 14), family members (n = 10) and clinicians (n = 11) was conducted to explore lived experiences, needs, perspectives and clinical considerations. Inductive analysis indicated common temporal stages related to undergoing DBS, and the related experiences and needs were mapped.

Findings

Four stages, each with unique needs, emerged: Considering DBS involved needs for peer-based education and realistic, meaningful goal setting; Surgery and Support shifted to clinical support related to the surgery and support for the person and their family around immediate changes experienced; Seeking Stability focused on timely clinical and practical support for the person and family around new changes and challenges to symptoms, behaviours and roles; and Next Steps involved direction and support for reengagement in the self-management of the condition, and current and future changes related to PD.

All participants with PD and their family members in this study indicated that overall their experiences with DBS had led to positive changes in their symptoms and lives. Consideration of different needs at different times in the process may be applied within clinical practice to support adjustment.

Modulation of Parkinsonian State With Uncertain Disturbance Based on Sliding Mode Control

Parkinson's disease (PD) is a degenerative disorder of central nervous system that endangers the olds' health seriously. The motor symptoms of PD can be attributed to the distorted relay reliability of thalamus to cortical sensorimotor input that results from the increase of inhibitory input from internal segment of the globus pallidum (GPi). Based on this, we construct the GPi-thalamocortical computational model to generate the normal and pathological firing patterns by varying GPi spike train input. A kind of closed-loop deep brain stimulation (DBS) strategy is proposed here. Our control objective is to make the controlled membrane potential of the thalamic neuron return to the normal firing pattern. The control input that directly acts on the thalamus is the DBS waveform, which is adjusted in real time according to the feedback signal. Aimed at a certain system without the change of object parameters or stochastic disturbance, the input-output feedback linearization method is able to eliminate the error between the system output and the desired output. When uncertain elements taken into consideration in the system, the simulation results indicate that sliding mode control scheme provides better effectiveness and higher robustness.

Computational Modeling and Neuroimaging Techniques for Targeting during Deep Brain Stimulation

Accurate surgical localization of the varied targets for deep brain stimulation (DBS) is a process undergoing constant evolution, with increasingly sophisticated techniques to allow for highly precise targeting. However, despite the fastidious placement of electrodes into specific structures within the brain, there is increasing evidence to suggest that the clinical effects of DBS are likely due to the activation of widespread neuronal networks directly and indirectly influenced by the stimulation of a given target. Selective activation of these complex and inter-connected pathways may further improve the outcomes of currently treated diseases by targeting specific fiber tracts responsible for a particular symptom in a patient-specific manner. Moreover, the delivery of such focused stimulation may aid in the discovery of new targets for electrical stimulation to treat additional neurological, psychiatric, and even cognitive disorders. As such, advancements in surgical targeting, computational modeling, engineering designs, and neuroimaging techniques play a critical role in this process. This article reviews the progress of these applications, discussing the importance of target localization for DBS, and the role of computational modeling and novel neuroimaging in improving our understanding of the pathophysiology of diseases, and thus paving the way for improved selective target localization using DBS.

Long-term outcome of globus pallidus internus deep brain stimulation in patients with Tourette syndrome

OBJECTIVE

To evaluate the effectiveness of deep brain stimulation (DBS) of the globus pallidus internus (GPi) on tic severity and common comorbidities in patients with severe Tourette syndrome that is refractory to pharmacological treatment and psychotherapy.

PATIENTS AND METHODS

We retrospectively assessed the long-term clinical outcomes of 13 patients with treatment-refractory Tourette syndrome who underwent DBS targeting the GPi at the Beijing Tiantan Hospital from January 1, 2006, through May 31, 2013. The primary outcome was a change in tic severity as measured by the Yale Global Tic Severity Scale, and the secondary outcome was a change in associated behavioral disorders and mood as measured by the Gilles de la Tourette Syndrome-Quality of Life Scale assessment.

RESULTS

Compared with baseline, the mean reduction in the total Yale Global Tic Severity Scale scores at last follow-up (mean, 41.9 months; range, 13-80 months) was 52.1% (range, 4.3%-83.6%), and the mean improvement rates at 1 month, 6 months, 12 months, 18 months, 24 months, 30 months, and 36 or more months were 11.8%, 20.0%, 26.8%, 36.7%, 44.7%, 49.0%, and 56.7%, respectively. A paired-sample t test revealed significant improvement of tic symptoms after 6 months of DBS programming (P<.05). The Gilles de la Tourette Syndrome-Quality of Life Scale score improved by a mean of 45.7% (range, 11.0%-77.2%).

CONCLUSION

This study is currently the largest reported GPi DBS case series of patients with treatment-refractory TS with the longest follow-up. Our results support the potential beneficial effect of GPi DBS on disabling tic reduction and improvement of quality of life.

Functional MRI reveals frequency-dependent responses during deep brain stimulation at the subthalamic nucleus or internal globus pallidus

Deep brain stimulation (DBS) represents a widely used therapeutic tool for the symptomatic treatment of movement disorders, most commonly Parkinson's disease (PD). High frequency stimulation at both the subthalamic nucleus (STN) and internal globus pallidus (GPi) has been used with great success for the symptomatic treatment of PD, although the therapeutic mechanisms of action remain elusive. To better understand how DBS at these target sites modulates neural circuitry, the present study used functional blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to map global brain responses to DBS at the STN and GPi of the rat. Robust activation centered in the ipsilateral motor cortex was observed during high frequency stimulation at either target site, with peak responses observed at a stimulation frequency of 100Hz. Of note, frequency tuning curves were generated, demonstrating that cortical activation was maximal at clinically-relevant stimulation frequencies. Divergent responses to stimulation were noted in the contralateral hemisphere, with strong cortical and striatal negative BOLD signal during stimulation of the GPi, but not STN. The frequency-dependence of the observed motor cortex activation at both targets suggests a relationship with the therapeutic effects of STN and GPi DBS, with both DBS targets being functionally connected with motor cortex at therapeutic stimulation frequencies.

Pathways of translation: deep brain stimulation

Electrical stimulation of the brain has a 2000 year history. Deep brain stimulation (DBS), one form of neurostimulation, is a functional neurosurgical approach in which a high-frequency electrical current stimulates targeted brain structures for therapeutic benefit. It is an effective treatment for certain neuropathologic movement disorders and an emerging therapy for psychiatric conditions and epilepsy. Its translational journey did not follow the typical bench-to-bedside path, but rather reversed the process. The shift from ancient and medieval folkloric remedy to accepted medical practice began with independent discoveries about electricity during the 19th century and was fostered by technological advances of the 20th. In this paper, we review that journey and discuss how the quest to expand its applications and improve outcomes is taking DBS from the bedside back to the bench.

Emerging subspecialties in neurology: deep brain stimulation and electrical neuro-network modulation

Deep brain stimulation (DBS) is a surgical therapy that involves the delivery of an electrical current to one or more brain targets. This technology has been rapidly expanding to address movement, neuropsychiatric, and other disorders. The evolution of DBS has created a niche for neurologists, both in the operating room and in the clinic. Since DBS is not always deep, not always brain, and not always simply stimulation, a more accurate term for this field may be electrical neuro-network modulation (ENM). Fellowships will likely in future years evolve their scope to include other technologies, and other nervous system regions beyond typical DBS therapy.

Tremor suppression by rhythmic transcranial current stimulation

Tremor can dominate Parkinson’s disease and yet responds less well to dopaminergic medications than do other cardinal symptoms of this condition [1, 2]. Deep brain stimulation can provide striking tremor relief, but the introduction of stimulating electrodes deep in the substance of the brain carries significant risks, including those of hemorrhage [3]. Here, we pioneer an alternative approach in which we noninvasively apply transcranial alternating current stimulation (TACS) over the motor cortex [4, 5] to induce phase cancellation of the rest tremor rhythm. We first identify the timing of cortical oscillations responsible for rest tremor in the periphery by delivering tremor-frequency stimulation over motor cortex but do not couple this stimulation to the on-going tremor—instead, the rhythms simply “drift” in and out of phase alignment with one another. Slow alternating periods of phase cancellation and reinforcement result, informing on the phase alignments that induce the greatest change in tremor amplitude. Next, we deliver stimulation at these specified phase alignments to demonstrate controlled suppression of the on-going tremor. With this technique we can achieve almost 50% average reduction in resting tremor amplitude and in so doing form the basis of a closed-loop tremor-suppression therapy that could be extended to other oscillopathies.