Neurostimulation Devices for the Treatment of Neurologic Disorders

Accessibility and Ease of Use in Neuromodulation Devices

BACKGROUND

The utilization of neuromodulation therapy continues to grow as therapeutic indications expand. These conditions often present with comorbid physical, visual, and auditory impairments. Patients with disabilities in these categories may have difficulty operating their devices. Thus, reviewing the accessibility and inclusive design of neuromodulation devices is imperative to ensure equal access for patients of all ability levels. To date, the literature provides little insight into this topic.

MATERIALS AND METHODS

Manufacturers of Food and Drug Administration-approved neuromodulation devices in the United States completed our electronic survey to assess neuromodulation device features, universal/inclusive design guidelines, and methods used to make the device accessible to patients with disabilities.

RESULTS

We assessed 11 devices from seven manufacturers. Of those, there were six spinal cord, two peripheral nerve, and three deep brain stimulators. Of all respondents, 91% used universal inclusive design guidelines. Of the studied devices, 91% have an interface that uses visual feedback, and 82% have an interface that uses auditory feedback. All surveyed devices were reported to have an interface that requires physical handling.

DISCUSSION

Our study found that most devices incorporate auditory signals, buttons with raised indentations, speech commands, or other useful features to assist those with visual disabilities. Visual interfaces may be sufficient for a patient with hearing impairment to use all the surveyed devices. However, dual sensory impairment presents a significant limitation in all devices surveyed. Furthermore, the biggest barrier to using neuromodulation devices was physical impairment because all surveyed devices require physical handling.

CONCLUSIONS

Manufacturers have awareness of universal inclusive design principles. However, our study was unable to find a device that is accessible to all users regardless of ability. As such, it is critical to involve universal design principles to ensure that inclusive devices are available to improve patient adherence, treatment efficacy, and outcomes.

Mapping the hotspots and future trends of electrical stimulation for peripheral nerve injury: A bibliometric analysis from 2002 to 2023

Peripheral nerve injuries often result in severe personal and social burden, and even with surgical treatment, patients continue to have poor clinical outcomes. Over the past two decades, electrical stimulation has been shown to promote axonal regeneration and alleviate refractory neuropathic pain. The aim of this study was to analyse this field using a bibliometric approach. Literature was searched through Web of Science Core Collection (WOSCC) for the years 2002-2023. Literature analysis included: (1) Describing publication trends in the field. (2) Exploring collaborative network relationships. (3) Finding research advances and research hotspots in the field. (4) Summarizing research trends in the field. With the number of studies in this field still increasing, a total of 693 publications were included in the analysis. This field of research is interdisciplinary in nature. Research hotspots include peripheral nerve regeneration, the treatment of neuropathic pain, materials for nerve injury repair, and the restoration of sensory function in patients with peripheral nerve injury. Correspondingly, the development of nerve conduits and systems for peripheral nerve electrical stimulation, clinical trials of peripheral nerve electrical stimulation, and tactile recovery and movement for amputees have shown significant promise as future research trends in this field.

Disrupting abnormal neuronal oscillations with adaptive delayed feedback control

Closed-loop neuronal stimulation has a strong therapeutic potential for neurological disorders such as Parkinson's disease. However, at the moment, standard stimulation protocols rely on continuous open-loop stimulation and the design of adaptive controllers is an active field of research. Delayed feedback control (DFC), a popular method used to control chaotic systems, has been proposed as a closed-loop technique for desynchronisation of neuronal populations but, so far, was only tested in computational studies. We implement DFC for the first time in neuronal populations and access its efficacy in disrupting unwanted neuronal oscillations. To analyse in detail the performance of this activity control algorithm, we used specialised in vitro platforms with high spatiotemporal monitoring/stimulating capabilities. We show that the conventional DFC in fact worsens the neuronal population oscillatory behaviour, which was never reported before. Conversely, we present an improved control algorithm, adaptive DFC (aDFC), which monitors the ongoing oscillation periodicity and self-tunes accordingly. aDFC effectively disrupts collective neuronal oscillations restoring a more physiological state. Overall, these results support aDFC as a better candidate for therapeutic closed-loop brain stimulation.

A retrospective, naturalistic study of deep brain stimulation and vagal nerve stimulation in young patients

INTRODUCTION

Invasive neuromodulation interventions such as deep brain stimulation (DBS) and vagal nerve stimulation (VNS) are important treatments for movement disorders and epilepsy, but literature focused on young patients treated with DBS and VNS is limited. This retrospective study aimed to examine naturalistic outcomes of VNS and DBS treatment of epilepsy and dystonia in children, adolescents, and young adults.

METHODS

We retrospectively assessed patient demographic and outcome data that were obtained from electronic health records. Two researchers used the Clinical Global Impression scale to retrospectively rate the severity of neurologic and psychiatric symptoms before and after patients underwent surgery to implant DBS electrodes or a VNS device. Descriptive and inferential statistics were used to examine clinical effects.

RESULTS

Data from 73 patients were evaluated. Neurologic symptoms improved for patients treated with DBS and VNS (p < .001). Patients treated with DBS did not have a change in psychiatric symptoms, whereas psychiatric symptoms worsened for patients treated with VNS (p = .008). The frequency of postoperative complications did not differ between VNS and DBS groups.

CONCLUSION

Young patients may have distinct vulnerabilities for increased psychiatric symptoms during treatment with invasive neuromodulation. Child and adolescent psychiatrists should consider a more proactive approach and greater engagement with DBS and VNS teams that treat younger patients.

Neurodiagnostic and neurotherapeutic potential of graphene nanomaterials

Graphene has emerged as a highly promising nanomaterial for a variety of advanced technologies, including batteries, energy, electronics, and biotechnologies. Its recent contribution to neurotechnology is particularly noteworthy because its superior conductivity, chemical resilience, biocompatibility, thermal stability, and scalable nature make it well-suited for measuring brain activity and plasticity in health and disease. Graphene-mediated compounds are microfabricated in two central methods: chemical processes with natural graphite and chemical vapor deposition of graphene in a film form. They are widely used as biosensors and bioelectronics for neurodiagnostic and neurotherapeutic purposes in several brain disorders, such as Parkinson's disease, stroke, glioma, epilepsy, tinnitus, and Alzheimer's disease. This review provides an overview of studies that have demonstrated the technical advances of graphene nanomaterials in neuroscientific and clinical applications. We also discuss current limitations and future demands in relation to the clinical application of graphene, highlighting its potential technological and clinical significance for treating brain disorders. Our review underscores the potential of graphene nanomaterials as powerful tools for advancing the understanding of the brain and developing new therapeutic strategies.

Neural population dynamics reveals disruption of spinal circuits' responses to proprioceptive input during electrical stimulation of sensory afferents

While neurostimulation technologies are rapidly approaching clinical applications for sensorimotor disorders, the impact of electrical stimulation on network dynamics is still unknown. Given the high degree of shared processing in neural structures, it is critical to understand if neurostimulation affects functions that are related to, but not targeted by, the intervention. Here, we approach this question by studying the effects of electrical stimulation of cutaneous afferents on unrelated processing of proprioceptive inputs. We recorded intraspinal neural activity in four monkeys while generating proprioceptive inputs from the radial nerve. We then applied continuous stimulation to the radial nerve cutaneous branch and quantified the impact of the stimulation on spinal processing of proprioceptive inputs via neural population dynamics. Proprioceptive pulses consistently produce neural trajectories that are disrupted by concurrent cutaneous stimulation. This disruption propagates to the somatosensory cortex, suggesting that electrical stimulation can perturb natural information processing across the neural axis.

Biomimetic computer-to-brain communication enhancing naturalistic touch sensations via peripheral nerve stimulation

Artificial communication with the brain through peripheral nerve stimulation shows promising results in individuals with sensorimotor deficits. However, these efforts lack an intuitive and natural sensory experience. In this study, we design and test a biomimetic neurostimulation framework inspired by nature, capable of "writing" physiologically plausible information back into the peripheral nervous system. Starting from an in-silico model of mechanoreceptors, we develop biomimetic stimulation policies. We then experimentally assess them alongside mechanical touch and common linear neuromodulations. Neural responses resulting from biomimetic neuromodulation are consistently transmitted towards dorsal root ganglion and spinal cord of cats, and their spatio-temporal neural dynamics resemble those naturally induced. We implement these paradigms within the bionic device and test it with patients (ClinicalTrials.gov identifier NCT03350061). He we report that biomimetic neurostimulation improves mobility (primary outcome) and reduces mental effort (secondary outcome) compared to traditional approaches. The outcomes of this neuroscience-driven technology, inspired by the human body, may serve as a model for advancing assistive neurotechnologies.

Heart rate variability and cold-induced vascular dilation after stimulation of two different areas of the ear: a prospective, single-blinded, randomized crossover study

BACKGROUND

Both noninvasive transauricular vagus nerve stimulation (taVNS) and traditional medical practice (TMP), such as auriculotherapy, use the auricle as a starting point for stimulation, but with two different conceptual frameworks: taVNS depends on vagal afferences to account for its effects, whereas TMP requires stimulation of the ear with high topographical accuracy regardless of the afferent nerves. The aim of this study was to measure heart rate variability (HRV) and cold water-induced vasodilation (CIVD) after puncturing two different ear points with the same afference but that should have opposite effects according to TMP.

METHODS

Ten healthy subjects were investigated in this single-blinded crossover study over three sessions. In the first session, sympathetic activation was performed via cold water immersion of the right hand, with recordings taken from multiple fingers. HRV was assessed in the time domain (square root of the mean squared differences of NN intervals (RMSSD)) and frequency domain (low (LF) and high frequencies (HF)). In the second and third sessions, the same skin immersion test was performed, and mechanical stimulation was applied to the ear at two different points on the internal surface of the antitragus, one with alleged parasympathetic activity and the other with alleged sympathetic activity. The stimulation was done with semipermanent needles.

RESULTS

Stimulation of the point with alleged parasympathetic activity immediately resulted in a significant decrease in RMSSD in 75% of the subjects and in LF in 50% of the subjects, while stimulation of the point with alleged sympathetic activity resulted in an increase in HF and RMSSD in 50% of the subjects. Stimulation of these points did not affect the CIVD reflex. The 20 min cold water immersion induced an immediate decrease in LF and the LF/HF ratio and an increase in HF. The skin temperature of the nonimmersed medius significantly decreased when the contralateral hand was immersed, from 34.4 °C to 31.8 °C.

CONCLUSIONS

Stimulation of two different ear points innervated by the same afferent nerves elicited different HRV responses, suggesting somatotopy and a vagal effect beyond vagal afferences. These results are not in accordance with the claims of TMP.

TRIAL REGISTRATION

NCT04130893 (18/10/2019) clinicaltrials.com.

Personalized inference for neurostimulation with meta-learning: a case study of vagus nerve stimulation

Objective. Neurostimulation is emerging as treatment for several diseases of the brain and peripheral organs. Due to variability arising from placement of stimulation devices, underlying neuroanatomy and physiological responses to stimulation, it is essential that neurostimulation protocols are personalized to maximize efficacy and safety. Building such personalized protocols would benefit from accumulated information in increasingly large datasets of other individuals' responses.Approach. To address that need, we propose a meta-learning family of algorithms to conduct few-shot optimization of key fitting parameters of physiological and neural responses in new individuals. While our method is agnostic to neurostimulation setting, here we demonstrate its effectiveness on the problem of physiological modeling of fiber recruitment during vagus nerve stimulation (VNS). Using data from acute VNS experiments, the mapping between amplitudes of stimulus-evoked compound action potentials (eCAPs) and physiological responses, such as heart rate and breathing interval modulation, is inferred.Main results. Using additional synthetic data sets to complement experimental results, we demonstrate that our meta-learning framework is capable of directly modeling the physiology-eCAP relationship for individual subjects with much fewer individually queried data points than standard methods.Significance. Our meta-learning framework is general and can be adapted to many input-response neurostimulation mapping problems. Moreover, this method leverages information from growing data sets of past patients, as a treatment is deployed. It can also be combined with several model types, including regression, Gaussian processes with Bayesian optimization, and beyond.

Fascicle-Selective Ultrasound-Powered Bidirectional Wireless Peripheral Nerve Interface IC

This paper presents an innovative, minimally invasive, battery-free, wireless, peripheral nervous system (PNS) neural interface, which seamlessly integrates a millimeter-scale, fascicle-selective integrated circuit (IC) with extraneural recording and stimulating channels. The system also incorporates a wearable interrogator equipped with integrated machine-learning capabilities. This PNS interface is specifically tailored for adaptive neuromodulation therapy, targeting individuals with paralysis, amputation, or chronic medical conditions. By employing a neural pathway classifier and temporal interference stimulation, the proposed interface achieves precise deep fascicle selectivity for recording and stimulation without the need for nerve penetration or compression. Ultrasonic energy harvesters facilitate wireless power harvesting and data reception, enhancing the usability of the system. Key circuit performance metrics encompass a 2.2 μVrms input-referred noise, 14-bit ENOB, and a 173 dB Schreier figure of merit (FOM) for the neural analog-to-digital converter (ADC). Additionally, the ultra-low-power radio-frequency (RF) transmitter boasts a remarkable 1.38 pJ/bit energy efficiency. In vivo experiments conducted on rat sciatic nerves provide compelling evidence of the interface's ability to selectively stimulate and record neural fascicles. The proposed PNS neural interface offers alternative treatment options for diagnosing and treating neurological disorders, as well as restoring or repairing neural functions, improving the quality of life for patients with neurological and sensory deficits.

Beyond Tissue replacement: The Emerging role of smart implants in healthcare

Smart implants are increasingly used to treat various diseases, track patient status, and restore tissue and organ function. These devices support internal organs, actively stimulate nerves, and monitor essential functions. With continuous monitoring or stimulation, patient observation quality and subsequent treatment can be improved. Additionally, using biodegradable and entirely excreted implant materials eliminates the need for surgical removal, providing a patient-friendly solution. In this review, we classify smart implants and discuss the latest prototypes, materials, and technologies employed in their creation. Our focus lies in exploring medical devices beyond replacing an organ or tissue and incorporating new functionality through sensors and electronic circuits. We also examine the advantages, opportunities, and challenges of creating implantable devices that preserve all critical functions. By presenting an in-depth overview of the current state-of-the-art smart implants, we shed light on persistent issues and limitations while discussing potential avenues for future advancements in materials used for these devices.

Implantable microfluidics: methods and applications

Implantable microfluidics involves integrating microfluidic functionalities into implantable devices, such as medical implants or bioelectronic devices, revolutionizing healthcare by enabling personalized and precise diagnostics, targeted drug delivery, and regeneration of targeted tissues or organs. The impact of implantable microfluidics depends heavily on advancements in both methods and applications. Despite significant progress in the past two decades, continuous advancements are still required in fluidic control and manipulation, device miniaturization and integration, biosafety considerations, as well as the development of various application scenarios to address a wide range of healthcare issues. In this review, we discuss advancements in implantable microfluidics, focusing on methods and applications. Regarding methods, we discuss progress made in fluid manipulation, device fabrication, and biosafety considerations in implantable microfluidics. In terms of applications, we review advancements in using implantable microfluidics for drug delivery, diagnostics, tissue engineering, and energy harvesting. The purpose of this review is to expand research ideas for the development of novel implantable microfluidic devices for various healthcare applications.

A Comprehensive Review of Emerging Trends and Innovative Therapies in Epilepsy Management

Epilepsy is a complex neurological disorder affecting millions worldwide, with a substantial number of patients facing drug-resistant epilepsy. This comprehensive review explores innovative therapies for epilepsy management, focusing on their principles, clinical evidence, and potential applications. Traditional antiseizure medications (ASMs) form the cornerstone of epilepsy treatment, but their limitations necessitate alternative approaches. The review delves into cutting-edge therapies such as responsive neurostimulation (RNS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS), highlighting their mechanisms of action and promising clinical outcomes. Additionally, the potential of gene therapies and optogenetics in epilepsy research is discussed, revealing groundbreaking findings that shed light on seizure mechanisms. Insights into cannabidiol (CBD) and the ketogenic diet as adjunctive therapies further broaden the spectrum of epilepsy management. Challenges in achieving seizure control with traditional therapies, including treatment resistance and individual variability, are addressed. The importance of staying updated with emerging trends in epilepsy management is emphasized, along with the hope for improved therapeutic options. Future research directions, such as combining therapies, AI applications, and non-invasive optogenetics, hold promise for personalized and effective epilepsy treatment. As the field advances, collaboration among researchers of natural and synthetic biochemistry, clinicians from different streams and various forms of medicine, and patients will drive progress toward better seizure control and a higher quality of life for individuals living with epilepsy.

Knowledge and Perception Toward Neuromodulation Devices Among Medical Students at Umm Al-Qura University

Introduction Neurologic and psychiatric disorders affect many people worldwide and are crucial to medical care. It is crucial to note that primary care doctors initially evaluate patients who will eventually require neuromodulation (NM) therapy. There is a growing concern about the extent of medical students' knowledge regarding NM therapy. Insufficient education and limited exposure of future doctors to different treatment approaches can limit their ability to refer patients promptly and appropriately, thereby impeding access to necessary treatment. Methods The study employed a non-probability stratified snowball sampling technique to recruit participants. The population consisted of undergraduate medical students (excluding interns) at Umm Al-Qura University (UQU) in Saudi Arabia. Data collection was conducted through an online questionnaire. Results The sample comprised 301 medical students, with an average age of 21.62±1.54 years (ranging from 18 to 25). The majority were female (65.1%), and in the clinical years (57.8%), a considerable portion of respondents (57.5%) lacked awareness that NM devices are approved by the FDA for treatment. Both pre-clinical and clinical-year students exhibited insufficient knowledge (91.3% and 91.4%, respectively). Females showed a higher proportion (95.9%) of poor attitudes toward NM compared to males (83.8%). Notably, preclinical students showed a higher level of knowledge (11.0%) compared to clinical students (6.3%). Conclusions The study revealed a significant lack of knowledge among medical students regarding NM devices. This is concerning given the growing prevalence of NM devices in clinical practice. To ensure optimal patient care, it is crucial to provide comprehensive education on NM devices to medical students.

No laughing white matter: Reduced integrity of the cortical cholinergic pathways in Parkinson's disease-related cognitive impairment

BACKGROUND

Approximately one third of recently diagnosed Parkinson's disease (PD) patients experience cognitive decline. The nucleus basalis of Meynert (NBM) degenerates early in PD and is crucial for cognitive function. The two main NBM white matter pathways include a lateral and medial trajectory. However, research is needed to determine which pathway, if any, are associated with PD-related cognitive decline.

METHODS

Thirty-seven PD patients with no mild cognitive impairment (MCI) were included in this study. Participants either developed MCI at 1-year follow up (PD MCI-Converters; n = 16) or did not (PD no-MCI; n = 21). Mean diffusivity (MD) and fractional anisotropy (FA) of the medial and lateral NBM tracts were extracted using probabilistic tractography. Between-group differences in MD and FA for each tract was compared using ANCOVA, controlling for age, sex, and disease duration. Control comparisons of the internal capsule MD and FA were also performed. Associations between baseline MD or FA and cognitive outcomes (working memory, psychomotor speed, delayed recall, and visuospatial function) were assessed using linear mixed models.

RESULTS

PD MCI-Converters had significantly greater MD and lower FA (p < .001) of both NBM tracts compared to PD no-MCI. No difference was found in the MD (p = .06) or FA (p = .31) of the control region. Trends were identified between: 1) lateral tract MD and FA with working memory decline; and 2) medial tract MD and reduced psychomotor speed.

CONCLUSIONS

Reduced integrity of the NBM tracts is evident in PD patients up to one year prior to the development of MCI. Thus, deterioration of the NBM tracts in PD may be an early marker of those at risk of cognitive decline.

Toward a New Generation of Bio-Scaffolds for Neural Tissue Engineering: Challenges and Perspectives

Neural tissue engineering presents a compelling technological breakthrough in restoring brain function, holding immense promise. However, the quest to develop implantable scaffolds for neural culture that fulfill all necessary criteria poses a remarkable challenge for material science. These materials must possess a host of desirable characteristics, including support for cellular survival, proliferation, and neuronal migration and the minimization of inflammatory responses. Moreover, they should facilitate electrochemical cell communication, display mechanical properties akin to the brain, emulate the intricate architecture of the extracellular matrix, and ideally allow the controlled release of substances. This comprehensive review delves into the primary requisites, limitations, and prospective avenues for scaffold design in brain tissue engineering. By offering a panoramic overview, our work aims to serve as an essential resource, guiding the creation of materials endowed with bio-mimetic properties, ultimately revolutionizing the treatment of neurological disorders by developing brain-implantable scaffolds.

No Laughing White Matter: Cortical Cholinergic Pathways and Cognitive Decline in Parkinson's Disease

Background

Approximately one third of recently diagnosed Parkinson's disease (PD) patients experience cognitive decline. The nucleus basalis of Meynert (NBM) degenerates early in PD and is crucial for cognitive function. The two main NBM white matter pathways include a lateral and medial trajectory. However, research is needed to determine which pathway, if any, are associated with PD-related cognitive decline.

Methods

Thirty-seven PD patients with no mild cognitive impairment (MCI) were included in this study. Participants either developed MCI at 1-year follow up (PD MCI-Converters; n=16) or did not (PD no-MCI; n=21). Mean diffusivity (MD) of the medial and lateral NBM tracts were extracted using probabilistic tractography. Between-group differences in MD for each tract was compared using ANCOVA, controlling for age, sex, and disease duration. Control comparisons of the internal capsule MD were also performed. Associations between baseline MD and cognitive outcomes (working memory, psychomotor speed, delayed recall, and visuospatial function) were assessed using linear mixed models.

Results

PD MCI-Converters had significantly greater MD of both NBM tracts compared to PD no-MCI (p<.001). No difference was found in the control region (p=.06). Trends were identified between: 1) lateral tract MD, poorer visuospatial performance (p=.05) and working memory decline (p=.04); and 2) medial tract MD and reduced psychomotor speed (p=.03).

Conclusions

Reduced integrity of the NBM tracts is evident in PD patients up to one year prior to the development of MCI. Thus, deterioration of the NBM tracts in PD may be an early marker of those at risk of cognitive decline.

Sulfobetaine-based ultrathin coatings as effective antifouling layers for implantable neuroprosthetic devices

Foreign body response (FBR), inflammation, and fibrotic encapsulation of neural implants remain major problems affecting the impedance of the electrode-tissue interface and altering the device performance. Adhesion of proteins and cells (e.g., pro-inflammatory macrophages, and fibroblasts) triggers the FBR cascade and can be diminished by applying antifouling coatings onto the implanted devices. In this paper, we report the deposition and characterization of a thin (±6 nm) sulfobetaine-based coating onto microfabricated platinum electrodes and cochlear implant (CI) electrode arrays. We found that this coating has stable cell and protein-repellent properties, for at least 31 days in vitro, not affected by electrical stimulation protocols. Additionally, its effect on the electrochemical properties relevant to stimulation (i.e., impedance, charge injection capacity) was negligible. When applied to clinical CI electrode arrays, the film was successful at inhibiting fibroblast adhesion on both the silicone packaging and the platinum/iridium electrodes. In vitro, in fibroblast cultures, coated CI electrode arrays maintained impedance values up to five times lower compared to non-coated devices. Our studies demonstrate that such thin sulfobetaine containing layers are stable and prevent protein and cell adhesion in vitro and are compatible for use on CI electrode arrays. Future in vivo studies should be conducted to investigate its ability to mitigate biofouling, fibrosis, and the resulting impedance changes upon long-term implantation in vivo.

From disabled tourists to impaired cyborg tourists: What would it take to transform?

Despite the media reports and governments promoting tourism as a fundamental right for everyone, traveling is still not accessible for disabled people. This study has highlighted the need to make tourists with disabilities accessable for inaccessible destinations. Cyborg products in the form of technological implants can make tourists with disabilities accessable for inaccessible destinations. Since tourists with a mobility disability (TMD) will be one of the primary beneficiaries of technological implants, little is known about their acceptance of technological implants during traveling.Therefore, this study assesses the willingness of TMD to use technological implants during traveling through a qualitative research approach. The results from thematic analysis identified two main themes: the use of assistive devices during traveling with four sub-themes (freedom of traveling, physical and attitudinal barriers, cost, and additional assistance and battery issues), and drivers of impaired cyborg tourists with seven sub-themes (independence, improved well-being, convenience/ease of use, social inclusion, positive emotions, motivation, and other issues). The study contributed to the literature by introducing drivers of impaired cyborg tourists along with previously identified concepts. The results also provided implications for the stakeholders of the tourism industry.

Adding a single pulse into high-frequency pulse stimulations can substantially alter the following episode of neuronal firing in rat hippocampus

Background. High-frequency stimulation (HFS) sequences of electrical pulses are commonly utilized in many types of neuromodulation therapies. The temporal pattern of pulse sequences characterized by varying inter-pulse intervals (IPI) has emerged as an adjustable dimension to generate diverse effects of stimulations to meet the needs for developing the therapies.Objective:To explore the hypothesis that a simple manipulation of IPI by inserting a pulse in HFS with a constant IPI can substantially change the neuronal responses.Approach. Antidromic HFS (A-HFS) and orthodromic HFS (O-HFS) sequences were respectively applied at the alveus (the efferent axons) and the Schaffer collaterals (the afferent axons) of hippocampal CA1 region in anesthetized ratsin-vivo. The HFS sequences lasted 120 s with a pulse frequency of 100 Hz and an IPI of 10 ms. In the late steady period (60-120 s) of the HFS, additional pulses were inserted into the original pulse sequences to investigate the alterations of neuronal responses to the changes in IPI. The amplitudes and latencies of antidromic/orthodromic population spikes (APS/OPS) evoked by pulses were measured to evaluate the alterations of the evoked firing of CA1 pyramidal neurons caused by the pulse insertions.Main Results. During the steady period of A-HFS at efferent axons, the evoked APSs were suppressed due to intermittent axonal block. Under this situation, inserting a pulse to shorten an IPI was able to redistribute the following neuronal firing thereby generating an episode of oscillation in the evoked APS sequence including APSs with significantly increased and decreased amplitudes. Also, during the steady period of O-HFS without obvious OPS, a pulse insertion was able to generate a large OPS, indicating a synchronized firing of a large population of post-synaptic neurons induced by a putative redistribution of activations at the afferent axons under O-HFS.Significance. This study firstly showed that under the situation of HFS-induced axonal block, changing an IPI by a single-pulse insertion can substantially redistribute the evoked neuronal responses to increase synchronized firing of neuronal populations during both antidromic and O-HFS with a constant IPI originally. The finding provides a potential way to enhance the HFS action on neuronal networks without losing some other functions of HFS such as generating axonal block.

A computational roadmap to electronic drugs

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

Focal electrical stimulation on an alcohol disorder model using magnetic resonance imaging-compatible chronic neural monopolar carbon fiber electrodes

Neuromodulation interventions, such as Deep Brain Stimulation (DBS) and repeated transcranial magnetic stimulation (rTMS), are proposed as possible new complementary therapies to treat substance use disorders (SUD) such as alcohol use disorder (AUD). It is hypothesized that neuromodulation may induce neural plasticity in the reward and frontostriatal systems via electrical field induction, possibly reducing symptoms. Preclinical self-administration rodent models of AUD may help us gain insight into the effects of neuromodulation therapies on different pathology, as well as the neural mechanisms behind the positive effects. DBS, or any type of brain stimulation using intracranial electrodes in rodents, would benefit from the use of magnetic resonance imaging (MRI) to study the longitudinal effects and mechanisms of stimulation as well as novel targets, as it is a non-invasive technique that allows the analysis of structural and functional changes in the brain. To do this, there is a need for MRI-compatible electrodes that allow for MRI acquisition with minimal distortion of the magnetic field. In this protocol, we present a method for the construction and surgery of chronically implantable monopolar carbon electrodes for use in rats. Unlike conventional electrodes, carbon electrodes are resistant to high temperatures, flexible, and generate fewer artifacts in MRI compared to conventional ones. We validated its use by using a focal electrical stimulation high-frequency (20 Hz) protocol that lasted ∼10 sessions. We propose that this technique can also be used for the research of the neurophysiological bases of the neuromodulatory treatment in other preclinical substance use disorders (SUD) models.

Deep Brain Stimulation for Addictive Disorders-Where Are We Now?

In the face of a global epidemic of drug addiction, neglecting to develop new effective therapies will perpetuate the staggering human and economic costs of substance use. This review aims to summarize and evaluate the preclinical and clinical studies of deep brain stimulation (DBS) as a novel therapy for refractory addiction, in hopes to engage and inform future research in this promising novel treatment avenue. An electronic database search (MEDLINE, EMBASE, Cochrane library) was performed using keywords and predefined inclusion criteria between 1974 and 6/18/2021 (registered on Open Science Registry). Selected articles were reviewed in full text and key details were summarized and analyzed to understand DBS' therapeutic potential and possible mechanisms of action. The search yielded 25 animal and 22 human studies. Animal studies showed that DBS of targets such as nucleus accumbens (NAc), insula, and subthalamic nucleus reduces drug use and seeking. All human studies were case series/reports (level 4/5 evidence), mostly targeting the NAc with generally positive outcomes. From the limited evidence in the literature, DBS, particularly of the NAc, appears to be a reasonable last resort option for refractory addictive disorders. We propose that future research in objective electrophysiological (e.g., local field potentials) and neurochemical (e.g., extracellular dopamine levels) biomarkers would assist monitoring the progress of treatment and developing a closed-loop DBS system. Preclinical literature also highlighted the prefrontal cortex as a promising DBS target, which should be explored in human research.

Chronic electrical stimulation of peripheral nerves via deep-red light transduced by an implanted organic photocapacitor

Implantable devices for the wireless modulation of neural tissue need to be designed for reliability, safety and reduced invasiveness. Here we report chronic electrical stimulation of the sciatic nerve in rats by an implanted organic electrolytic photocapacitor that transduces deep-red light into electrical signals. The photocapacitor relies on commercially available semiconducting non-toxic pigments and is integrated in a conformable 0.1-mm³ thin-film cuff. In freely moving rats, fixation of the cuff around the sciatic nerve, 10 mm below the surface of the skin, allowed stimulation (via 50-1,000-μs pulses of deep-red light at wavelengths of 638 nm or 660 nm) of the nerve for over 100 days. The robustness, biocompatibility, low volume and high-performance characteristics of organic electrolytic photocapacitors may facilitate the wireless chronic stimulation of peripheral nerves.

Three-dimensional multilayer concentric bipolar electrodes restrict spatial activation in optic nerve stimulation

OBJECTIVE

Intraneural nerve interfaces often operate in a monopolar configuration with a common and distant ground electrode. This configuration leads to a wide spreading of the electric field. Therefore, this approach is suboptimal for intraneural nerve interfaces when selective stimulation is required.

APPROACH

We designed a multilayer electrode array embedding three-dimensional concentric bipolar electrodes. First, we validated the higher stimulation selectivity of this new electrode array compared to classical monopolar stimulation using simulations. Next, we compared them in-vivo by intraneural stimulation of the rabbit optic nerve and recording evoked potentials in the primary visual cortex.

MAIN RESULTS

Simulations showed that three-dimensional concentric bipolar electrodes provide a high localisation of the electric field in the tissue so that electrodes are electrically independent even for high electrode density. Experiments in-vivo highlighted that this configuration restricts spatial activation in the visual cortex due to the fewer fibres activated by the electric stimulus in the nerve.

SIGNIFICANCE

Highly focused electric stimulation is crucial to achieving high selectivity in fibre activation. The multilayer array embedding three-dimensional concentric bipolar electrodes improves selectivity in optic nerve stimulation. This approach is suitable for other neural applications, including bioelectronic medicine.

An Anodic Phase Can Facilitate Rather Than Weaken a Cathodic Phase to Activate Neurons in Biphasic-Pulse Axonal Stimulations

Electrical pulses have been promisingly utilized in neural stimulations to treat various diseases. Usually, charge-balanced biphasic pulses are applied in the clinic to eliminate the possible side effects caused by charge accumulations. Because of its reversal action to the preceding cathodic phase, the subsequent anodic phase has been commonly considered to lower the activation efficiency of biphasic pulses. However, an anodic pulse itself can also activate axons with its “virtual cathode” effect. Therefore, we hypothesized that the anodic phase of a biphasic pulse could facilitate neuronal activation in some circumstances. To verify the hypothesis, we compared the activation efficiencies of cathodic pulse, biphasic pulse, and anodic pulse applied in both monopolar and bipolar modes in the axonal stimulation of alveus in rat hippocampal CA1 region in vivo. The antidromically evoked population spikes (APS) were recorded and used to evaluate the amount of integrated firing of pyramidal neurons induced by pulse stimulations. We also used a computational model to investigate the pulse effects on axons at various distances from the stimulation electrode. The experimental results showed that, with a small pulse intensity, a cathodic pulse recruited more neurons to fire than a biphasic pulse. However, the situation was reversed with an increased pulse intensity. In addition, setting an inter-phase gap of 100 μs was able to increase the activation efficiency of a biphasic pulse to exceed a cathodic pulse even with a relatively small pulse intensity. Furthermore, the latency of APS evoked by a cathodic pulse was always longer than that of APS evoked by a biphasic pulse, indicating different initial sites of the neuronal firing evoked by the different types of pulses. The computational results of axon modeling showed that the subsequent anodic phase was able to relieve the hyperpolarization block in the flanking regions generated by the preceding cathodic phase, thereby increasing rather than decreasing the activation efficiency of a biphasic pulse with a relatively great intensity. These results of both rat experiments and computational modeling firstly reveal a facilitation rather than an attenuation effect of the anodic phase on biphasic-pulse stimulations, which provides important information for designing electrical stimulations for neural therapies.

The Visual Cortical Responses to Sinusoidal Transcorneal Electrical Stimulation

Retinal stimulation has become a widely utilized approach to restore visual function for individuals with retinal degenerative diseases. Although the rectangular electrical pulse is the primary stimulus waveform used in retinal neuromodulation, it remains unclear whether alternate waveforms may be more effective. Here, we used the optical intrinsic signal imaging system to assess the responses of cats' visual cortex to sinusoidal electrical stimulation through contact lens electrode, analyzing the response to various stimulus parameters (frequency, intensity, pulse width). A comparison between sinusoidal and rectangular stimulus waveform was also investigated. The results indicated that the optimal stimulation frequency for sinusoidal electrical stimulation was approximately 20 Hz, supporting the hypothesis that low-frequency electrostimulation induces more responsiveness in retinal neurons than high-frequency electrostimulation in case of sinusoidal stimulation. We also demonstrated that for low-frequency retinal neuromodulation, sinusoidal pulses are more effective than rectangular ones. In addition, we found that compared to current intensity, the effect of the sinusoidal pulse width on cortical responses was more prominent. These results suggested that sinusoidal electrical stimulation may provide a promising strategy for improved retinal neuromodulation in clinical settings.

Ethical Considerations in the Implantation of Neuromodulatory Devices

OBJECTIVES

Neuromodulatory devices are increasingly used by neurosurgeons to manage a variety of chronic conditions. Given their potential benefits, it is imperative to create clear ethical guidelines for the use of these devices. We present a tiered ethical framework for neurosurgeon recommendations for the use of neuromodulatory devices.

MATERIALS AND METHODS

We conducted a literature review to identify factors neurosurgeons should consider when choosing to offer a neuromodulatory device to a patient.

RESULTS

Neurosurgeons must weigh reductions in debilitating symptoms, improved functionality, and preserved quality of life against risks for intraoperative complications and adverse events due to stimulation or the device itself. Neurosurgeons must also evaluate whether patients and families will maintain responsibility for the management of neuromodulatory devices. Consideration of these factors should occur on an axis of resource allocation, ranging from provision of neuromodulatory devices to those with greatest potential benefit in resource-limited settings to provision of neuromodulatory devices to all patients with indications in contexts without resource limitations. Neurosurgeons must also take action to promote device effectiveness throughout the duration of care.

CONCLUSIONS

Weighing risks and benefits of providing neuromodulatory devices and assessing ability to remain responsible for the devices on the level of the individual patient indicate which patients are most likely to achieve benefit from these devices. Consideration of these factors on an axis of resource allocation will allow for optimal provision of neuromodulatory devices to patients in settings of varied resources. Neurosurgeons play a primary role in promoting the effectiveness of these devices.

In vivo application of an implantable tri-anchored methylene blue-based electrochemical pH sensor

The development of robust implantable sensors is important in the successful advancement of personalised medicine as they have the potential to provide in situ real-time data regarding the status of health and disease and the effectiveness of treatment. Tissue pH is a key physiological parameter and herein, we report the design, fabrication, functionalisation, encapsulation and protection of a miniaturised, self-contained, electrochemical pH sensor system and characterisation of sensor performance. Notably for the first time in this environment the pH sensor was based on a methylene blue redox reporter which showed remarkable robustness, accuracy and sensitivity. This was achieved by encapsulation of a self-assembled monolayer containing methylene blue entrapped within a Nafion layer. Another powerful feature was the incorporation, within the same implanted device, of a fabricated on-chip Ag/AgCl reference electrode - vital in any electrochemical sensor, but often ignored. When utilised in vivo, the sensor allowed accurate tracking of externally induced pH changes within a naturally occurring ovine lung cancer model, and correlated well with single point laboratory measurements made on extracted arterial blood, whilst enabling in vivo time-dependent measurements. The sensors functioned robustly whilst implanted, and maintained in vitro function once extracted and together, these results demonstrate proof-of-concept of the ability to sense real-time intratumoral tissue pH changes in vivo.

Different Transcutaneous Auricular Vagus Nerve Stimulation Parameters Modulate the Anti-Inflammatory Effects on Lipopolysaccharide-Induced Acute Inflammation in Mice

Vagus nerve stimulation (VNS) is considered a potential method for anti-inflammation due to the involvement of the VN in the cholinergic anti-inflammatory pathway (CAP) formation of a connection between the central nervous system and peripheral immune cells that help relieve inflammation. However, whether a non-invasive transcutaneous auricular VNS (taVNS) modulates the inflammation levels via altering the parameter of taVNS is poorly understood. This study aimed to determine the differential inhibitory effects of taVNS on lipopolysaccharide (LPS)-induced systemic inflammation using electrical stimulation parameters such as pulse frequency and time. The taVNS-promoted CAP activity significantly recovered LPS-induced tissue injuries (lung, spleen, and intestine) and decreased inflammatory cytokine levels and tissue-infiltrated immune cells. Interestingly, the anti-inflammatory capacity of taVNS with 15 Hz was much higher than that of taVNS with 25 Hz. When a cytokine array was used to investigate the changes of inflammation and immune response-related cytokines/chemokines expression in taVNS with 15 Hz or 25 Hz treatment in LPS-induced endotoxemia in mice, most of the expression of cytokines/chemokines associated with pro-inflammation was severely decreased in taVNS with 15 Hz compared to 25 Hz. This study demonstrated that the taVNS parameter could differentially modulate the inflammation levels of animals, suggesting the importance of taVNS parameter selection for use in feasible interventions for acute inflammation treatment.

Soft Devices for High-Resolution Neuro-Stimulation: The Interplay Between Low-Rigidity and Resolution

The field of neurostimulation has evolved over the last few decades from a crude, low-resolution approach to a highly sophisticated methodology entailing the use of state-of-the-art technologies. Neurostimulation has been tested for a growing number of neurological applications, demonstrating great promise and attracting growing attention in both academia and industry. Despite tremendous progress, long-term stability of the implants, their large dimensions, their rigidity and the methods of their introduction and anchoring to sensitive neural tissue remain challenging. The purpose of this review is to provide a concise introduction to the field of high-resolution neurostimulation from a technological perspective and to focus on opportunities stemming from developments in materials sciences and engineering to reduce device rigidity while optimizing electrode small dimensions. We discuss how these factors may contribute to smaller, lighter, softer and higher electrode density devices.

Dorsal root entry zone procedure and other surgeries for pain

Pain is a very common symptom that often serves a protective function. It is typically treated medically. When pain becomes chronic and intractable, it no longer serves a protective function and often requires more aggressive forms of treatment. Many types of surgeries can be performed for the management of pain. These surgeries can involve ablation (destruction) or augmentation (stimulation or facilitation) of some part of the nervous system. In many of these surgeries, neurophysiologic intraoperative monitoring (NIOM) is not needed, however, in others neuromonitoring serves a mapping and monitoring purpose. The prototype of pain surgery for this chapter is the dorsal root entry zone (DREZ) procedure. Both mapping and monitoring can help improve lesioning precision and outcomes in this surgery. In this chapter, the DREZ procedures and other surgeries for primarily pain relief in which NIOM is used are discussed. Surgeries, such as spinal stenosis, in which pain relief is important but not the sole purpose, are not discussed here and are covered elsewhere.

Protocol for deep brain stimulation in the fimbria-fornix of freely moving mice

Deep brain stimulation (DBS) entails neurosurgery to implant electrodes in specific brain structures to modulate the behavior of a particular neural circuit. DBS is best known for treating advanced Parkinson disease and can potentially be applicable to other motor and even cognitive dysfunctions. Here, we describe a detailed protocol allowing for electrode preparation, surgical procedures, stimulation delivery, and field potential recordings in both anesthetized and behaving mice, and the benefit evaluation of DBS at the fimbria-fornix by using a fear conditioning test. For complete details on the use and execution of this protocol, please refer to Hao et al. (2015).

Non-invasive brain stimulation for treating neurogenic dysarthria: A systematic review

BACKGROUND

Although non-invasive central and peripheral stimulations are accruing support as promising treatments in different neurological conditions, their effects on dysarthria have not been systematically investigated.

OBJECTIVE

The purpose of this review was to examine the evidence base of non-invasive stimulation for treating dysarthria, identify which stimulation parameters have the most potential for treatment and determine safety risks.

METHODS

A systematic review with meta-analysis, when possible, involving publications indexed in MEDLINE, PsychINFO, EMBASE CINHAL the Linguistics and Language Behavioral Abstracts, Web of Science, Cochrane Register of Control Trials and 2 trial registries was completed. Articles were searched in December 2018 and updated in June 2021 using keywords related to brain and electrical stimulation, dysarthria and research design. We included trials with randomised, cross-over or quasi-experimental designs; involving a control group; and investigating treatment of neurogenic dysarthria with non-invasive stimulation. Methodological quality was determined with the Cochrane's Risk of Bias-2 tool.

RESULTS

In total, 6186 studies were identified; 10 studies (6 randomised controlled trials and 4 cross-over studies) fulfilled the inclusion criteria. All 10 trials (268 adults with Parkinson's disease, stroke and neurodegenerative cerebellar ataxia) focused on brain stimulation (6 repetitive transcranial magnetic stimulation; 3 transcranial direct current stimulation; and 1 repetitive transorbital alternating current stimulation). Adjunct speech-language therapy was delivered in 2 trials. Most trials reported one or more positive effects of stimulation on dysarthria-related features; however, given the overall high risk of bias and heterogeneity in participant, trial and outcome measurement characteristics, no conclusions can be drawn. Post-treatment size effects for 2 stroke trials demonstrated no statistically significant differences between active and sham stimulation across 3 dysarthria outcomes.

CONCLUSIONS

Evidence for use of non-invasive brain stimulation in treating dysarthria remains inconclusive. Research trials that provide reliable and replicable findings are required.

Restoring Sensorimotor Function Through Neuromodulation After Spinal Cord Injury: Progress and Remaining Challenges

Spinal cord injury (SCI) is a major disability that results in motor and sensory impairment and extensive complications for the affected individuals which not only affect the quality of life of the patients but also result in a heavy burden for their families and the health care system. Although there are few clinically effective treatments for SCI, research over the past few decades has resulted in several novel treatment strategies which are related to neuromodulation. Neuromodulation-the use of neuromodulators, electrical stimulation or optogenetics to modulate neuronal activity-can substantially promote the recovery of sensorimotor function after SCI. Recent studies have shown that neuromodulation, in combination with other technologies, can allow paralyzed patients to carry out intentional, controlled movement, and promote sensory recovery. Although such treatments hold promise for completely overcoming SCI, the mechanisms by which neuromodulation has this effect have been difficult to determine. Here we review recent progress relative to electrical neuromodulation and optogenetics neuromodulation. We also examine potential mechanisms by which these methods may restore sensorimotor function. We then highlight the strengths of these approaches and remaining challenges with respect to its application.

Neuromodulation in Super-refractory Status Epilepticus

SUMMARY

Status epilepticus (SE) is a severe condition that needs immediate pharmacological treatment to tackle brain damage and related side effects. In approximately 20% of cases, the standard treatment for SE does not control seizures, and the condition evolves to refractory SE. If refractory status epilepticus lasts more than 24 hours despite the use of anesthetic treatment, the condition is redefined as super-refractory SE (srSE). sRSE is a destructive condition, potentially to cause severe brain damage. In this review, we discuss the clinical neuromodulation techniques for controlling srSE when conventional treatments have failed: electroconvulsive therapy, vagus nerve stimulation, transcranial magnetic stimulation, and deep brain stimulation. Data show that neuromodulation therapies can abort srSE in >80% of patients. However, no randomized, prospective, and controlled trials have been completed, and data are provided only by retrospective small case series and case reports with obvious inclination to publication bias. There is a need for further investigation into the use of neuromodulation techniques as an early treatment of srSE and to address whether an earlier intervention can prevent long-term complications.

Altered Regional Homogeneity and Functional Connectivity during Microlesion Period after Deep Brain Stimulation in Parkinson's Disease

Background

Patients with Parkinson's disease (PD) undergoing deep brain electrode implantation experience a temporary improvement in motor symptoms before the electrical stimulation begins. We usually call this the microlesion effect (MLE), but the mechanism behind it is not clear.

Purpose

This study aimed to assess the alterations in brain functions at the regional and whole-brain levels, using regional homogeneity (ReHo) and functional connectivity (FC), during the postoperative microlesion period after deep brain stimulation (DBS) in PD patients.

Method

Resting-state functional MRI data were collected from 27 PD patients before and after the first day of DBS and 12 healthy controls (HCs) in this study. The ReHo in combination with FC analysis was used to investigate the alterations of regional brain activity in all the subjects.

Results

There were increased ReHo in the basal ganglia-thalamocortical circuit (left supplementary motor area and bilateral paracentral lobule), whereas decreased ReHo in the default mode network (DMN) (left angular gyrus, bilateral precuneus), prefrontal cortex (bilateral middle frontal gyrus), and the cerebello-thalamocortical (CTC) circuit (Cerebellum_crus2/1_L) after DBS. In addition, we also found abnormal FC in the lingual gyrus, cerebellum, and DMN.

Conclusion

Microlesion of the thalamus caused by electrode implantation can alter the activity of the basal ganglia-thalamocortical circuit, prefrontal cortex, DMN, and CTC circuit and induce abnormal FC in the lingual gyrus, cerebellum, prefrontal cortex, and DMN among PD patients. The findings of this study contribute to the understanding of the mechanism of MLE.

Transcranial Focal Electrical Stimulation Modifies Biogenic Amines' Alterations Induced by 6-Hydroxydopamine in Rat Brain

Transcranial focal stimulation (TFS) is a non-invasive neuromodulation strategy with neuroprotective effects. On the other hand, 6-hidroxidopamine (6-OHDA) induces neurodegeneration of the nigrostriatal system producing modifications in the dopaminergic, serotoninergic, and histaminergic systems. The present study was conducted to test whether repetitive application of TFS avoids the biogenic amines' changes induced by the intrastriatal injection of 6-OHDA. Experiments were designed to determine the tissue content of dopamine, serotonin, and histamine in the brain of animals injected with 6-OHDA and then receiving daily TFS for 21 days. Tissue content of biogenic amines was evaluated in the cerebral cortex, hippocampus, amygdala, and striatum, ipsi- and contralateral to the side of 6-OHDA injection. Results obtained were compared to animals with 6-OHDA, TFS alone, and a Sham group. The present study revealed that TFS did not avoid the changes in the tissue content of dopamine in striatum. However, TFS was able to avoid several of the changes induced by 6-OHDA in the tissue content of dopamine, serotonin, and histamine in the different brain areas evaluated. Interestingly, TFS alone did not induce significant changes in the different brain areas evaluated. The present study showed that repetitive TFS avoids the biogenic amines' changes induced by 6-OHDA. TFS can represent a new therapeutic strategy to avoid the neurotoxicity induced by 6-OHDA.

Altered Spontaneous Neural Activity and Functional Connectivity in Parkinson's Disease With Subthalamic Microlesion

Background

Transient improvement in motor symptoms are immediately observed in patients with Parkinson's disease (PD) after an electrode has been implanted into the subthalamic nucleus (STN) for deep brain stimulation (DBS). This phenomenon is known as the microlesion effect (MLE). However, the underlying mechanisms of MLE is poorly understood.

Purpose

We utilized resting state functional MRI (rs-fMRI) to evaluate changes in spontaneous brain activity and networks in PD patients during the microlesion period after DBS.

Method

Overall, 37 PD patients and 13 gender- and age-matched healthy controls (HCs) were recruited for this study. Rs-MRI information was collected from PD patients three days before DBS and one day after DBS, whereas the HCs group was scanned once. We utilized the amplitude of low-frequency fluctuation (ALFF) method in order to analyze differences in spontaneous whole-brain activity among all subjects. Furthermore, functional connectivity (FC) was applied to investigate connections between other brain regions and brain areas with significantly different ALFF before and after surgery in PD patients.

Result

Relative to the PD-Pre-DBS group, the PD-Post-DBS group had higher ALFF in the right putamen, right inferior frontal gyrus, right precentral gyrus and lower ALFF in right angular gyrus, right precuneus, right posterior cingulate gyrus (PCC), left insula, left middle temporal gyrus (MTG), bilateral middle frontal gyrus and bilateral superior frontal gyrus (dorsolateral). Functional connectivity analysis revealed that these brain regions with significantly different ALFF scores demonstrated abnormal FC, largely in the temporal, prefrontal cortices and default mode network (DMN).

Conclusion

The subthalamic microlesion caused by DBS in PD was found to not only improve the activity of the basal ganglia-thalamocortical circuit, but also reduce the activity of the DMN and executive control network (ECN) related brain regions. Results from this study provide new insights into the mechanism of MLE.

Pediatric Movement Disorders and Neuromodulation: An Overview

Pediatric movement disorders are heterogeneous and complex disorders with various aetiologies. These are broadly classified as hypo and hyperkinetic disorders. Genetic causes of basal ganglia dysfunction or direct injuries to the basal ganglia mark the genesis of these abnormal movements. The management of pediatric movement disorders is multidisciplinary with pharmacotherapy as the first line of management along with physical therapy. Patients resistant to medications are candidates for invasive neuromodulation which is an upcoming treatment modality in pediatric movement disorders. Deep brain stimulation of basal ganglia and thalamic nuclei are associated with promising symptomatic benefit with reduction in disability and improvement in quality of life of these children. In this article, we have reviewed the management of pediatric movement disorders with emphasis on neuromodulation i.e., deep brain stimulation.

DeepNavNet: Automated Landmark Localization for Neuronavigation

Functional neurosurgery requires neuroimaging technologies that enable precise navigation to targeted structures. Insufficient image resolution of deep brain structures necessitates alignment to a brain atlas to indirectly locate targets within preoperative magnetic resonance imaging (MRI) scans. Indirect targeting through atlas-image registration is innately imprecise, increases preoperative planning time, and requires manual identification of anterior and posterior commissure (AC and PC) reference landmarks which is subject to human error. As such, we created a deep learning-based pipeline that consistently and automatically locates, with submillimeter accuracy, the AC and PC anatomical landmarks within MRI volumes without the need for an atlas. Our novel deep learning pipeline (DeepNavNet) regresses from MRI scans to heatmap volumes centered on AC and PC anatomical landmarks to extract their three-dimensional coordinates with submillimeter accuracy. We collated and manually labeled the location of AC and PC points in 1128 publicly available MRI volumes used for training, validation, and inference experiments. Instantiations of our DeepNavNet architecture, as well as a baseline model for reference, were evaluated based on the average 3D localization errors for the AC and PC points across 311 MRI volumes. Our DeepNavNet model significantly outperformed a baseline and achieved a mean 3D localization error of 0.79 ± 0.33 mm and 0.78 ± 0.33 mm between the ground truth and the detected AC and PC points, respectively. In conclusion, the DeepNavNet model pipeline provides submillimeter accuracy for localizing AC and PC anatomical landmarks in MRI volumes, enabling improved surgical efficiency and accuracy.

Spinal cord regeneration: A brief overview of the present scenario and a sneak peek into the future

The central nervous system (CNS) portrays appreciable complexity in developing from a neural tube to controlling major functions of the body and orchestrated co-ordination in maintaining its homeostasis. Any insult or pathology to such an organized tissue leads to a plethora of events ranging from local hypoxia, ischemia, oxidative stress to reactive gliosis and scarring. Despite unravelling the pathophysiology of spinal cord injury (SCI) and linked cellular and molecular mechanism, the over exhaustive inflammatory response at the site of injury, limited intrinsic regeneration capability of CNS, and the dual role of glial scar halts the expected accomplishment. The review discusses major current treatment approaches for traumatic SCI, addressing their limitation and scope for further development in the field under three main categories- neuroprotection, neuro-regeneration, and neuroplasticity. We further propose that a multi-disciplinary combinatorial treatment approach exploring any two or all three heads simultaneously might alleviate the inhibitory milieu and ameliorate functional recovery.

Human Body Rhythms in the Development of Non-Invasive Methods of Closed-Loop Adaptive Neurostimulation

The creation and improvement of non-invasive closed-loop brain stimulation technologies represent an exciting and rapidly expanding field of neuroscience. To identify the appropriate way to close the feedback loop in adaptive neurostimulation procedures, it was previously proposed to use on-line automatic sensory stimulation with the parameters modulated by the patient's own rhythmical processes, such as respiratory rate, heart rate, and electroencephalogram (EEG) rhythms. The current paper aims to analyze several recent studies demonstrating further development in this line of research. The advantages of using automatic closed-loop feedback from human endogenous rhythms in non-invasive adaptive neurostimulation procedures have been demonstrated for relaxation assistance, for the correction of stress-induced functional disturbances, for anxiety management, and for the cognitive rehabilitation of an individual. Several distinctive features of the approach are noted to delineate its further development.

Digital Health Integration With Neuromodulation Therapies: The Future of Patient-Centric Innovation in Neuromodulation

Digital health can drive patient-centric innovation in neuromodulation by leveraging current tools to identify response predictors and digital biomarkers. Iterative technological evolution has led us to an ideal point to integrate digital health with neuromodulation. Here, we provide an overview of the digital health building-blocks, the status of advanced neuromodulation technologies, and future applications for neuromodulation with digital health integration.

Two-photon GCaMP6f imaging of infrared neural stimulation evoked calcium signals in mouse cortical neurons in vivo

Infrared neural stimulation is a promising tool for stimulating the brain because it can be used to excite with high spatial precision without the need of delivering or inserting any exogenous agent into the tissue. Very few studies have explored its use in the brain, as most investigations have focused on sensory or motor nerve stimulation. Using intravital calcium imaging with the genetically encoded calcium indicator GCaMP6f, here we show that the application of infrared neural stimulation induces intracellular calcium signals in Layer 2/3 neurons in mouse cortex in vivo. The number of neurons exhibiting infrared-induced calcium response as well as the amplitude of those signals are shown to be both increasing with the energy density applied. By studying as well the spatial extent of the stimulation, we show that reproducibility of the stimulation is achieved mainly in the central part of the infrared beam path. Stimulating in vivo at such a degree of precision and without any exogenous chromophores enables multiple applications, from mapping the brain's connectome to applications in systems neuroscience and the development of new therapeutic tools for investigating the pathological brain.