Intraoperative and perioperative complications with a vagus nerve stimulation device

Vagus nerve stimulation and gut microbiota interactions: A novel therapeutic avenue for neuropsychiatric disorders

The rising prevalence of treatment-resistant neuropsychiatric disorders underscores the need for innovative and effective treatment strategies. The gut microbiota (GM) plays a pivotal role in the progression of these diseases, influencing the brain and mental health through the gut-brain axis (GBA). The vagus nerve plays a significant role in the GBA, making it a key area of focus for potential novel therapeutic interventions. Vagus nerve stimulation (VNS) was introduced and approved as a treatment for refractory forms of some neuropsychological disorders, such as depression and epilepsy. Considering its impact on several brain regions that play a vital part in mood, motivation, affection, and cognitive function, the VNS has shown significant therapeutic potential for treating a variety of neuropsychiatric disorders. Using VNS to target the bidirectional communication pathways linking the GM and the VN could present an exciting and novel approach to treating neuropsychological disorders. Imbalances in the GM, such as dysbiosis, can impair the communication pathways between the gut and the brain, contributing to the development of neuropsychological disorders. VNS shows potential for modulating these interconnected systems, helping to restore balance. Interestingly, the composition of the GM may also influence the effectiveness of VNS, as it has the potential to modify the brain's response to this therapeutic approach. This study provides a comprehensive analysis of a relatively unexplored but noteworthy interaction between VNS and GM in the treatment of neuropsychiatric disorders. In addition, we discussed the mechanisms, therapeutic potential, and clinical implications of VNS on the GBA across neuropsychiatric disorders.

Acute transcutaneous auricular vagus nerve stimulation modulates presynaptic SV2A density in healthy rat brain: An in vivo microPET study

Vagus nerve stimulation (VNS) is the subject of exploration as an adjunct treatment for neurological disorders such as epilepsy, chronic migraine, pain, and depression. A non-invasive form of VNS is transcutaneous auricular VNS (taVNS). Combining animal models and positron emission tomography (PET) may lead to a better understanding of the elusive mechanisms of taVNS. We evaluated the acute effect of electrical stimulation of the left vagus nerve via the ear on brain synaptic vesicle glycoprotein 2A (SV2A) as a measure of presynaptic density and glucose metabolism in naïve rats. Female Sprague-Dawley rats were imaged with [11C]UCB-J (n = 11) or [18F]fluorodeoxyglucose ([18F]FDG) PET (n = 13) on two separate days, (1) at baseline, and (2) after acute unilateral left taVNS or sham stimulation (30 min). We calculated the regional volume of distribution (VT) for [11C]UCB-J and standard uptake values (SUV) for [18F]FDG. We observed regional reductions of [11C]UCB-J binding in response to taVNS ranging from 36% to 59%. The changes in taVNS compared to baseline were significantly larger than those induced by sham stimulation. The differences were observed bilaterally in the frontal cortex, striatum, and midbrain. The [18F]FDG PET uptake remained unchanged following acute taVNS or sham stimulation compared to baseline values. This proof-of-concept study shows for the first time that acute taVNS for 30 min can modulate in vivo synaptic SV2A density in cortical and subcortical regions of healthy rats. Preclinical disease models and PET ligands of different targets can be a powerful combination to assess the therapeutic potential of taVNS.

Vagus nerve stimulation: a physical therapy with promising potential for central nervous system disorders

The diseases of the central nervous system (CNS) often cause irreversible damage to the human body and have a poor prognosis, posing a significant threat to human health. They have brought enormous burdens to society and healthcare systems. However, due to the complexity of their causes and mechanisms, effective treatment methods are still lacking. Vagus nerve stimulation (VNS), as a physical therapy, has been utilized in the treatment of various diseases. VNS has shown promising outcomes in some CNS diseases and has been approved by the Food and Drug Administration (FDA) in the United States for epilepsy and depression. Moreover, it has demonstrated significant potential in the treatment of stroke, consciousness disorders, and Alzheimer's disease. Nevertheless, the exact efficacy of VNS, its beneficiaries, and its mechanisms of action remain unclear. This article discusses the current clinical evidence supporting the efficacy of VNS in CNS diseases, providing updates on the progress, potential, and potential mechanisms of action of VNS in producing effects on CNS diseases.

Influence of a 2-week transcutaneous auricular vagus nerve stimulation on memory: findings from a randomized placebo controlled trial in non-clinical adults

PURPOSE

Memory plays an essential role in daily life and is one of the first functions to deteriorate in cognitive impairment and dementia. Transcutaneous vagus nerve stimulation (tVNS) is a promising therapeutic method; however, its ability to enhance memory is underexplored, especially considering long-term stimulation. We aimed to investigate the effect of a 2-week course of auricular tVNS (taVNS) on memory in a non-clinical population.

METHODS

This single-blind randomized placebo-wait-list controlled trial recruited 76 participants (30 men; mean age 48.32 years) and randomized them into four groups: early active/sham taVNS and late active/sham taVNS. Participation in the study lasted 4 weeks; early groups underwent 2 weeks intervention immediately following the first study site visit (days 0-13) and late groups 2 weeks after the first study site visit (days 14-27). Active and sham taVNS included 2 weeks of daily 4-h neurostimulation at the tragus or earlobe, respectively. To assess memory, we used the Rey Auditory Verbal Learning Test.

RESULTS

Two weeks of active taVNS, but not sham taVNS, improved immediate recall and short-term memory score both in early and late groups. Furthermore, the improvements persisted over subsequent follow-up in early active taVNS. Importantly, the effect of active taVNS was superior to sham for immediate recall in both early and late groups. There were no statistical differences in delayed recall.

CONCLUSION

Our findings suggest that taVNS has potential to improve memory, particularly immediate recall, and may be an effective method in preventing memory loss and mitigating cognitive aging.

Vagus Nerve Stimulation Therapy in Epilepsy: An Overview of Technical and Surgical Method, Patient Selection, and Treatment Outcomes

Epilepsy affects over 65 million people worldwide. One-third of people with epilepsy do not respond to medication and may benefit from surgery. Vagus nerve stimulation (VNS) is the first neuromodulation therapy for the treatment of drug-resistant epilepsy. This method is used in combination with anti-seizure medications in adults and in the pediatric population. VNS has also been demonstrated to have benefits for some epilepsy comorbidities, such as depression, and can be used in combination with other neuromodulation therapies in epilepsy. The authors present an overview of VNS physiology, patient selection, surgery and risks, neuromodulation therapy, and application to epilepsy comorbidities.

Adverse Events and Complications Associated With Vagal Nerve Stimulation: An Analysis of the Manufacturer And User Facility Device Experience Database

OBJECTIVE

Drug-resistant epilepsy (DRE) can have devastating consequences for patients and families. Vagal nerve stimulation (VNS) is used as a surgical adjunct for treating DRE not amenable to surgical resection. Although VNS is generally safe, it has its inherent complications. With the increasing number of implantations, adequate patient education with discussion of possible complications forms a critical aspect of informed consent and patient counseling. There is a lack of large-scale reviews of device malfunction, patient complaints, and surgically related complications available to date.

MATERIALS AND METHODS

Complications associated with VNS implants performed between 2011 and 2021 were identified through a search of the United States Food and Drug Administration Manufacturer And User Facility Device Experience (MAUDE) data base. We found three models on the data base, CYBERONICS, INC pulse gen Demipulse 103, AspireSR 106, and SenTiva 1000. The reports were classified into three main groups, "Device malfunction," "Patient complaints," and "Surgically managed complications."

RESULTS

A total of 5888 complications were reported over the ten-year period, of which 501 reports were inconclusive, 610 were unrelated, and 449 were deaths. In summary, there were 2272 reports for VNS 103, 1526 reports for VNS 106, and 530 reports for VNS 1000. Within VNS 103, 33% of reports were related to device malfunction, 33% to patient complaints, and 34% to surgically managed complications. For VNS 106, 35% were related to device malfunction, 24% to patient complaints, and 41% to surgically managed complications. Lastly, for VNS 1000, 8% were device malfunction, 45% patient complaints, and 47% surgically managed complications.

CONCLUSION

We present an analysis of the MAUDE data base for adverse events and complications related to VNS. It is hoped that this description of complications and literature review will help promote further improvement in its safety profile, patient education, and management of both patient and clinician expectations.

Transcutaneous vagus nerve stimulation: a new strategy for Alzheimer's disease intervention through the brain-gut-microbiota axis?

Transcutaneous vagus nerve stimulation (tVNS) is an emerging non-invasive technique designed to stimulate branches of the vagus nerve distributed over the body surface. Studies suggest a correlation between the brain-gut-microbiota (BGM) axis and the pathogenesis of Alzheimer's disease (AD). The BGM axis represents a complex bidirectional communication system, with the vagus nerve being a crucial component. Therefore, non-invasive electrical stimulation of the vagus nerve might have the potential to modify-most of the time probably in a non-physiological way-the signal transmission within the BGM axis, potentially influencing the progression or symptoms of AD. This review explores the interaction between percutaneous vagus nerve stimulation and the BGM axis, emphasizing its potential effects on AD. It examines various aspects, such as specific brain regions, gut microbiota composition, maintenance of intestinal environmental homeostasis, inflammatory responses, brain plasticity, and hypothalamic-pituitary-adrenal (HPA) axis regulation. The review suggests that tVNS could serve as an effective strategy to modulate the BGM axis and potentially intervene in the progression or treatment of Alzheimer's disease in the future.

Vagus Nerve Visualization Using Fused Images of 3D-CT Angiography and MRI as Preoperative Evaluation for Vagus Nerve Stimulation

Vagus nerve stimulation (VNS) is an effective surgical option for intractable epilepsy. Although the surgical procedure is not so complicated, vagus nerve detection is sometimes difficult due to its anatomical variations, which may lead to surgical manipulation-associated complications. Thus, this study aimed to visualize the vagus nerve location preoperatively by fused images of three-dimensional computed tomography angiography (3D-CTA) and magnetic resonance imaging (MRI). This technique was applied to two cases. The neck 3D-CTA and MRI were performed, and the fused images were generated using the software. The vagus nerve and its anatomical relationship with the internal jugular vein (IJV) and common carotid artery were clearly visualized. The authors predicted that the vagus nerve was detected by laterally pulling the IJV according to the images. Intraoperatively, the vagus nerve was located as the authors predicted. The time of the surgery until the vagus nerve detection was <60 min in both cases. This novel radiological technique for visualizing the vagus nerve is effective to quickly detect the vagus nerve, which has anatomical variations, during the VNS.

Perianaesthetic challenges in patients undergoing vagus nerve stimulation (VNS) placement

Patients with medically refractory epilepsy (MRE) are indicated for vagus nerve stimulation (VNS) placement. Anaesthesia for VNS placement is extremely challenging and requires several considerations. We present a man in his 20s with MRE who successfully underwent VNS placement. We review the mechanism of action of VNS, anaesthetic challenges and measures to prevent seizures.

Safety and Management of Implanted Epilepsy Devices for Imaging and Surgery

Permanently implanted devices that deliver electrical stimulation are increasingly used to treat patients with drug-resistant epilepsy. Primary care physicians, neurologists, and epilepsy clinicians may encounter patients with a variety of implanted neuromodulation devices in the course of clinical care. Due to the rapidly changing landscape of available epilepsy-related neurostimulators, there may be uncertainty related to how these devices should be handled during imaging procedures and perioperative care. We review the safety and management of epilepsy-related implanted neurostimulators that may be encountered during imaging and surgery. We provide a summary of approved device labeling and recommendations for the practical management of these devices to help guide clinicians as they care for patients treated with bioelectronic medicine.

Research advances in the application of vagus nerve electrical stimulation in ischemic stroke

Stroke seriously endangers human well-being and brings a severe burden to family and society. Different post-stroke dysfunctions result in an impaired ability to perform activities of daily living. Standard rehabilitative therapies may not meet the requirements for functional improvement after a stroke; thus, alternative approaches need to be proposed. Currently, vagus nerve stimulation (VNS) is clinically applied for the treatment of epilepsy, depression, cluster headache and migraine, while its treatment of various dysfunctions after an ischemic stroke is still in the clinical research stage. Recent studies have confirmed that VNS has neuroprotective effects in animal models of transient and permanent focal cerebral ischemia, and that its combination with rehabilitative training significantly improves upper limb motor dysfunction and dysphagia. In addition, vagus-related anatomical structures and neurotransmitters are closely implicated in memory–cognition enhancement processes, suggesting that VNS is promising as a potential treatment for cognitive dysfunction after an ischemic stroke. In this review, we outline the current status of the application of VNS (invasive and non-invasive) in diverse functional impairments after an ischemic stroke, followed by an in-depth discussion of the underlying mechanisms of its mediated neuroprotective effects. Finally, we summarize the current clinical implementation challenges and adverse events of VNS and put forward some suggestions for its future research direction. Research on VNS for ischemic stroke has reached a critical stage. Determining how to achieve the clinical transformation of this technology safely and effectively is important, and more animal and clinical studies are needed to clarify its therapeutic mechanism.

Predictors of vagus nerve stimulation complications among pediatric patients with drug-resistant epilepsy

OBJECTIVE

Complications from vagus nerve stimulator (VNS) procedures are common and can have important implications for morbidity and seizure control, yet predictors of complications are poorly understood. The objective of this study was to assess clinical factors associated with minor and major complications from VNS procedures among pediatric patients with drug-resistant epilepsy.

METHODS

The authors performed an 11-year retrospective review of patients who underwent VNS procedures for drug-resistant epilepsy at age < 21 years. The primary outcome was complications (minor or major) following VNS surgery. Preoperative and surgery characteristics were compared between patients who developed versus those who did not develop complications. Multivariable Poisson regression was performed to determine the association between preoperative characteristics and infection.

RESULTS

Of 686 surgeries, 48 complications (7.0%) developed; there were 7 minor complications (1.0%) and 41 major complications (6.0%). Surgeries with minor complications were an average of 68 minutes longer than those without minor complications (p < 0.001). The incidence rate of infection was 1 per 100 person-years, with 3% of procedures complicated by infection. Poisson regression revealed that after adjusting for age at surgery, duration of surgery, and primarily motor seizure semiology, the incident rate of infection for revision surgeries preceded by ≥ 2 procedures was 19 times that of first-time revisions.

CONCLUSIONS

The overall minor complication rate was 1% and the overall major complication rate was 6% for VNS procedures. Longer surgery duration was associated with the development of minor complications but not major complications. Repeat incisions to the VNS pocket may be associated with higher incident rate of infection, highlighting a need for longer-lasting VNS pulse generator models.

Autonomic Neural Circuit and Intervention for Comorbidity Anxiety and Cardiovascular Disease

Anxiety disorder is a prevalent psychiatric disease and imposes a significant influence on cardiovascular disease (CVD). Numerous evidence support that anxiety contributes to the onset and progression of various CVDs through different physiological and behavioral mechanisms. However, the exact role of nuclei and the association between the neural circuit and anxiety disorder in CVD remains unknown. Several anxiety-related nuclei, including that of the amygdala, hippocampus, bed nucleus of stria terminalis, and medial prefrontal cortex, along with the relevant neural circuit are crucial in CVD. A strong connection between these nuclei and the autonomic nervous system has been proven. Therefore, anxiety may influence CVD through these autonomic neural circuits consisting of anxiety-related nuclei and the autonomic nervous system. Neuromodulation, which can offer targeted intervention on these nuclei, may promote the development of treatment for comorbidities of CVD and anxiety disorders. The present review focuses on the association between anxiety-relevant nuclei and CVD, as well as discusses several non-invasive neuromodulations which may treat anxiety and CVD.

Effects of Long-Term Vagus Nerve Electrical Stimulation Therapy on Acute Cerebral Infarction and Neurological Function Recovery in Post MCAO Mice

Background

Vagus nerve stimulation therapy is proven to produce neuroprotective effects against central nervous system diseases and reduce neurological injury, having a positive effect on the recovery of neurological functions in mouse model of stroke.

Objective

This study was aimed at exploring a wider time window for VNS treatment, investigating the long-term behavioral improvement of long-term VNS in mice after pMCAO, and exploring the antiapoptotic properties of VNS and its role in autophagy, all of which may be a permanent deficiency potential mechanism of neuroprotection in hemorrhagic stroke.

Methods

Permanent focal cerebral ischemia and implantation of vagus nerve stimulator were performed through intracavitary occlusion of the right middle cerebral artery (MCA). The vagus nerve stimulation group received five times vagus nerve stimulation from 6 h after surgery for 5 days. Adhesive removal test and NSS neurological score were used to evaluate the neurological deficit of mice. TTC staining of mouse brain tissue was performed one week after surgery in order to assess the area of cerebral infarction. Additionally, frozen sections were stained with Fluoro-Jade B to observe the apoptotic cells in the ischemic penumbra of brain tissue. Finally, Western blot was used to detect the changes in the levels of apoptosis-related proteins such as cleaved-caspase3 and Bcl-2 and autophagy-related proteins such as mTOR, Beclin-1, and LC3-II in brain tissue.

Results

VNS can effectively reduce the behavioral score of pMCAO mice; TTC results showed that VNS could effectively reduce the infarct area after pMCAO (P < 0.05). After VNS intervention of the pMCAO group compared with the pMCAO+VNI group, the FJB-positive cells in the VNS group were significantly decreased (P < 0.05); Western Blot analysis showed that the expression of cleaved-caspase3 in the brain tissue of mice increased after pMCAO (P < 0.05), and the expression of Bcl-2 decreased (P < 0.05). This change could be effectively reversed after VNS intervention (P < 0.05).

Conclusion

VNS could effectively improve the behavioral performance of mice after permanent stroke in addition to significantly reducing the infarct size of the brain tissue. The mechanism may be related to the effective reduction of cell apoptosis and excessive autophagy after pMCAO by VNS.

Control of inflammation using non-invasive neuromodulation: past, present and promise

The nervous system has been increasingly recognized as a novel and accessible target in the regulation of inflammation. The use of implantable and invasive devices targeting neural circuits has yielded successful results in clinical settings but does have some risk or adverse effects. Recent advances in technology and understanding of mechanistic pathways have opened new avenues of non-invasive neuromodulation. Through this review we discuss the novel research and outcomes of major modalities of non-invasive neuromodulation in the context of inflammation including transcutaneous electrical, magnetic and ultrasound neuromodulation. In addition to highlighting the scientific observations and breakthroughs, we discuss the underlying mechanisms and pathways for neural regulation of inflammation.

Vagal Neuromodulation in Chronic Heart Failure With Reduced Ejection Fraction: A Systematic Review and Meta-Analysis

Objectives: The aim of this study was to evaluate the effects of invasive vagal nerve stimulation (VNS) in patients with chronic heart failure (HF) and reduced ejection fraction (HFrEF).

Background: Heart failure is characterized by autonomic nervous system imbalance and electrical events that can lead to sudden death. The effects of parasympathetic (vagal) stimulation in patients with HF are not well-established.

Methods: From May 1994 to July 2020, a systematic review was performed using PubMed, Embase, and Cochrane Library for clinical trials, comparing VNS with medical therapy for the management of chronic HFrEF (EF ≤ 40%). A meta-analysis of several outcomes and adverse effects was completed, and GRADE was used to assess the level of evidence.

Results: Four randomized controlled trials (RCT) and three prospective studies, totalizing 1,263 patients were identified; 756 treated with VNS and 507 with medical therapy. RCT data were included in the meta-analysis (fixed-effect distribution). Adverse effects related to VNS were observed in only 11% of patients. VNS was associated with significant improvement (GRADE = High) in the New York Heart Association (NYHA) functional class (OR, 2.72, 95% CI: 2.07–3.57, p < 0.0001), quality of life (MD −14.18, 95% CI: −18.09 to −10.28, p < 0.0001), a 6-min walk test (MD, 55.46, 95% CI: 39.11–71.81, p < 0.0001) and NT-proBNP levels (MD −144.25, 95% CI: −238.31 to −50.18, p = 0.003). There was no difference in mortality (OR, 1.24; 95% CI: 0.82–1.89, p = 0.43).

Conclusions: A high grade of evidence demonstrated that vagal nerve stimulation improves NYHA functional class, a 6-min walk test, quality of life, and NT-proBNP levels in patients with chronic HFrEF, with no differences in mortality.

Complete section of the left vagus nerve does not preclude the efficacy of vagus nerve stimulation: illustrative case

BACKGROUND

Vagus nerve stimulation (VNS) represents a valid therapeutic option for patients with medically intractable seizures who are not candidates for epilepsy surgery. Even when complete section of the nerve occurs, stimulation applied cranially to the involved nerve segment does not preclude the efficacy of VNS. Complete vagus nerve section with neuroma causing definitive left vocal cord palsy has never been previously reported in the literature.

OBSERVATIONS

Eight years after VNS implant, the patient experienced worsening of seizures; the interrogation of the generator revealed high impedance requiring surgical revision. On surgical exploration, complete left vagus nerve section and a neuroma were found. Vocal cord atrophy was found at immediate postoperative laryngeal inspection as a confirmation of a longstanding lesion. Both of these events might have been caused by direct nerve injury during VNS surgery, and they presented in a delayed fashion.

LESSONS

VNS surgery may be complicated by direct damage to the left vagus nerve, resulting in permanent neurological deficits. A complete section of the nerve also enables an efficacious stimulation if applied cranially to the involved segment. Laryngeal examination should be routinely performed before each VNS surgery to rule out preexisting vocal cord dysfunction.

Management and outcome of vagus nerve stimulator implantation: experience of an otolaryngeal/neuropediatric cooperation

OBJECTIVE

Vagus nerve stimulator (VNS) implantation is an established therapy for pharmacoresistant epilepsy that is not amenable to curative epilepsy surgery. Historically, VNS implantation has been performed by neurosurgeons, but otolaryngologist involvement is increasingly common. In this retrospective study, we aimed to evaluate the efficacy and safety of VNS implantation in children and adolescents from the otolaryngologists' perspective.

METHODS

This study included children and adolescents who had undergone VNS implantation at the study center between 2014 and 2018. Patient files were analyzed with regards to the durations of device implantation and hospitalization, postoperative complications, and clinical outcome, including seizure frequency, clinical global impression of improvement (CGI-I) score, and quality of life (QoL).

RESULTS

A total of 73 children underwent VNS surgery. The median age at implantation was 9.3 ± 4.6 years, and median epilepsy duration before VNS surgery was 6 ± 4 years. Lennox-Gastaut syndrome was the most common syndrome diagnosis (62.3%), and structural abnormalities (49.3%) the most frequent etiology. Operation times ranged from 30 to 200 min, and median postoperative hospitalization length was 2 ± 0.9 days. No complications occurred, except for four revisions and two explantations due to local infections (2.7%). Among our patients, 76.7% were responders (≥ 50% reduction in seizure frequency), 72.1% showed improved CGI-I scores, and 18.6-60.5% exhibited considerable improvements in the QoL categories energy, emotional health, and cognitive functions.

CONCLUSION

Our results indicate that VNS implantation is a highly effective and safe treatment option for children and adolescents with AED-refractory epilepsies who are not candidates for curative epilepsy surgery.

Transcranial Auricular Vagus Nerve Stimulation (taVNS) and Ear-EEG: Potential for Closed-Loop Portable Non-invasive Brain Stimulation

No matter how hard we concentrate, our attention fluctuates – a fact that greatly affects our success in completing a current task. Here, we review work from two methods that, in a closed-loop manner, have the potential to ameliorate these fluctuations. Ear-EEG can measure electric brain activity from areas in or around the ear, using small and thus portable hardware. It has been shown to capture the state of attention with high temporal resolution. Transcutaneous auricular vagus nerve stimulation (taVNS) comes with the same advantages (small and light) and critically current research suggests that it is possible to influence ongoing brain activity that has been linked to attention. Following the review of current work on ear-EEG and taVNS we suggest that a combination of the two methods in a closed-loop system could serve as a potential application to modulate attention.

Transcutaneous vagus nerve stimulation in patients with attention-deficit/hyperactivity disorder: A viable option?

Individuals with attention-deficit/hyperactivity disorder (ADHD) suffer from a range of cognitive and behavioral problems that severely impair their educational and occupational attainment. ADHD symptoms have been linked to structural and functional changes within and between different brain regions, particularly the prefrontal cortex. At the system level, reduced availability of the neurotransmitters dopamine (DA) and norepinephrine (NE) but also γ-aminobutyric acid (GABA) have been repeatedly demonstrated. Recently, non-invasive brain stimulation (NIBS) techniques have been explored as treatment alternatives to alter dysfunctional activation patterns in specified brain areas or networks. In the current paper, we introduce transcutaneous vagus nerve stimulation (tVNS) as a systemic approach to directly affect NE and GABA neurotransmission. TVNS is a non-drug intervention with low risk and proven efficacy in improving cognitive particularly executive functions. It is easy to apply and therefore well-suited to provide home-based or mobile treatment options allowing a significant increase in treatment intensity and providing easier access to medical care for individuals who are unable to regularly visit a clinician. We describe in detail the underlying mechanisms of tVNS and current fields of application and discuss its potential as an adjuvant treatment for ADHD.

Overview of therapeutic applications of non-invasive vagus nerve stimulation: a motivation for novel treatments for systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disorder that commonly affects the skin, joints, kidneys, and central nervous system. Although great progress has been made over the years, patients still experience unfavorable secondary effects from medications, increased economic burden, and higher mortality rates compared to the general population. To alleviate these current problems, non-invasive, non-pharmacological interventions are being increasingly investigated. One such intervention is non-invasive vagus nerve stimulation, which promotes the upregulation of the cholinergic anti-inflammatory pathway that reduces the activation and production of pro-inflammatory cytokines and reactive oxygen species, culpable processes in autoimmune diseases such as SLE. This review first provides a background on the important contribution of the autonomic nervous system to the pathogenesis of SLE. The gross and structural anatomy of the vagus nerve and its contribution to the inflammatory response are described afterwards to provide a general understanding of the impact of stimulating the vagus nerve. Finally, an overview of current clinical applications of invasive and non-invasive vagus nerve stimulation for a variety of diseases, including those with similar symptoms to the ones in SLE, is presented and discussed. Overall, the review presents neuromodulation as a promising strategy to alleviate SLE symptoms and potentially reverse the disease.

Sex Differences in Vagus Nerve Stimulation Effects on Rat Cardiovascular and Immune Systems

Background

Investigations into the benefits of vagus nerve stimulation (VNS) through pre-clinical and clinical research have led to promising findings for treating several disorders. Despite proven effectiveness of VNS on conditions such as epilepsy and depression, understanding of off-target effects and contributing factors such as sex differences can be beneficial to optimize therapy design.

New Methods

In this article, we assessed longitudinal effects of VNS on cardiovascular and immune systems, and studied potential sex differences using a rat model of long-term VNS. Rats were implanted with cuff electrodes around the left cervical vagus nerve for VNS, and wireless physiological monitoring devices for continuous monitoring of cardiovascular system using electrocardiogram (ECG) signals. ECG morphology and heart rate variability (HRV) features were extracted to assess cardiovascular changes resulting from VNS in short-term and long-term timescales. We also assessed VNS effects on expression of inflammatory cytokines in blood during the course of the experiment. Statistical analysis was performed to compare results between Treatment and Sham groups, and between male and female animals from Treatment and Sham groups.

Results

Considerable differences between male and female rats in cardiovascular effects of VNS were observed in multiple cardiovascular features. However, the effects seemed to be transient with approximately 1-h recovery after VNS. While short-term cardiovascular effects were mainly observed in male rats, females in general showed more significant long-term effects even after VNS stopped. We did not observe notable changes or sex differences in systemic cytokine levels resulting from VNS.

Comparison With Existing Methods

Compared to existing methods, our study design incorporated wireless physiological monitoring and systemic blood cytokine level analysis, along with long-term VNS experiments in unanesthetized rats to study sex differences.

Conclusion

The contribution of sex differences for long-term VNS off-target effects on cardiovascular and immune systems was assessed using awake behaving rats. Although VNS did not change the concentration of inflammatory biomarkers in systemic circulation for male and female rats, we observed significant differences in cardiovascular effects of VNS characterized using ECG morphology and HRV analyses.

Learnings from 30 years of reported efficacy and safety of vagus nerve stimulation (VNS) for epilepsy treatment: A critical review

Three decades after its introduction as an adjuvant therapeutic option in the management of selective drug-resistant epilepsy cases (DRE), vagus nerve stimulation (VNS) retains growing interest. An implantable device was first approved for epilepsy in Europe in 1994 and in the United States (US) in 1997. Subsequent modifications improved the safety and the efficacy of the system. The most recent application of vagal neurostimulation is represented by transcutaneous devices that are claimed to have strong therapeutic potential. In this review, we sought to analyze the most meaningful available data describing the indications, safety and efficacy of the different approaches of VNS in clinical practice. Therefore, we identified studies reporting VNS efficacy and/or safety in epilepsy and its comorbidities from January 1990 to February 2020 from various databases including PubMed, Scopus, Cochrane, US government databases and VNS manufacturer published resources. In general, VNS efficacy becomes optimal around the sixth month of treatment and a 50-100 % seizure frequency reduction is achieved in approximately 45-65 % of the patients. However, some clinically relevant differences have been reported with specific factors such as epilepsy etiology or type, patient age as well as the delay of VNS therapy onset. VNS efficacy on seizure frequency has been demonstrated in both children and adults, in lesional and non-lesional cases, in focal and generalized epilepsies, on both seizures and epilepsy comorbidities. Regarding the latter, VNS can lead to an improvement of about 25-35 % in depression scores, 35 % in anxiety scores and 25 % in mood assessment scores. If non-invasive devices are undeniably safer, their efficacy is limited due to the scarcity of large cohort studies and the disparity of methodological approaches (study design and stimulation parameters). Overall, we believe that there is a progress margin for improving the safety of implantable devices and, above all, the effectiveness of the various VNS approaches.

Critical Review of Transcutaneous Vagus Nerve Stimulation: Challenges for Translation to Clinical Practice

Several studies have illustrated that transcutaneous vagus nerve stimulation (tVNS) can elicit therapeutic effects that are similar to those produced by its invasive counterpart, vagus nerve stimulation (VNS). VNS is an FDA-approved therapy for the treatment of both depression and epilepsy, but it is limited to the management of more severe, intervention-resistant cases as a second or third-line treatment option due to perioperative risks involved with device implantation. In contrast, tVNS is a non-invasive technique that involves the application of electrical currents through surface electrodes at select locations, most commonly targeting the auricular branch of the vagus nerve (ABVN) and the cervical branch of the vagus nerve in the neck. Although it has been shown that tVNS elicits hypo- and hyperactivation in various regions of the brain associated with anxiety and mood regulation, the mechanism of action and influence of stimulation parameters on clinical outcomes remains predominantly hypothetical. Suppositions are largely based on correlations between the neurobiology of the vagus nerve and its effects on neural activity. However, tVNS has also been investigated for several other disorders, including tinnitus, migraine and pain, by targeting the vagus nerve at sites in both the ear and the neck. As most of the described methods differ in the parameters and protocols applied, there is currently no firm evidence on the optimal location for tVNS or the stimulation parameters that provide the greatest therapeutic effects for a specific condition. This review presents the current status of tVNS with a focus on stimulation parameters, stimulation sites, and available devices. For tVNS to reach its full potential as a non-invasive and clinically relevant therapy, it is imperative that systematic studies be undertaken to reveal the mechanism of action and optimal stimulation modalities.

Vagus nerve stimulation for drug-resistant epilepsy

Vagus nerve stimulation (VNS) is a neuromodulatory therapeutic option for drug-resistant epilepsy. In randomised controlled trials, VNS implantation has resulted in over 50% reduction in seizure frequency in 26%-40% of patients within 1 year. Long-term uncontrolled studies suggest better responses to VNS over time; however, the assessment of other potential predictive factors has led to contradictory results. Although initially designed for managing focal seizures, its use has been extended to other forms of drug-resistant epilepsy. In this review, we discuss the evidence supporting the use of VNS, its impact on seizure frequency and quality of life, and common adverse effects of this therapy. We also include practical guidance for the approach to and the management of patients with VNS in situ.

The anatomical basis for transcutaneous auricular vagus nerve stimulation

The array of end organ innervations of the vagus nerve, coupled with increased basic science evidence, has led to vagus nerve stimulation (VNS) being explored as a management option in a number of clinical disorders, such as heart failure, migraine and inflammatory bowel disease. Both invasive (surgically implanted) and non-invasive (transcutaneous) techniques of VNS exist. Transcutaneous VNS (tVNS) delivery systems rely on the cutaneous distribution of vagal afferents, either at the external ear (auricular branch of the vagus nerve) or at the neck (cervical branch of the vagus nerve), thus obviating the need for surgical implantation of a VNS delivery device and facilitating further investigations across a wide range of uses. The concept of electrically stimulating the auricular branch of the vagus nerve (ABVN), which provides somatosensory innervation to several aspects of the external ear, is relatively more recent compared with cervical VNS; thus, there is a relative paucity of literature surrounding its operation and functionality. Despite the increasing body of research exploring the therapeutic uses of auricular transcutaneous VNS (tVNS), a comprehensive review of the cutaneous, intracranial and central distribution of ABVN fibres has not been conducted to date. A review of the literature exploring the neuroanatomical basis of this neuromodulatory therapy is therefore timely. Our review article explores the neuroanatomy of the ABVN with reference to (1) clinical surveys examining Arnold's reflex, (2) cadaveric studies, (3) fMRI studies, (4) electrophysiological studies, (5) acupuncture studies, (6) retrograde tracing studies and (7) studies measuring changes in autonomic (cardiovascular) parameters in response to auricular tVNS. We also provide an overview of the fibre composition of the ABVN and the effects of auricular tVNS on the central nervous system. Cadaveric studies, of which a limited number exist in the literature, would be the 'gold-standard' approach to studying the cutaneous map of the ABVN; thus, there is a need for more such studies to be conducted. Functional magnetic resonance imaging (fMRI) represents a useful surrogate modality for discerning the auricular sites most likely innervated by the ABVN and the most promising locations for auricular tVNS. However, given the heterogeneity in the results of such investigations and the various limitations of using fMRI, the current literature lacks a clear consensus on the auricular sites that are most densely innervated by the ABVN and whether the brain regions secondarily activated by electrical auricular tVNS depend on specific parameters. At present, it is reasonable to surmise that the concha and inner tragus are suitable locations for vagal modulation. Given the therapeutic potential of auricular tVNS, there remains a need for the cutaneous map of the ABVN to be further refined and the effects of various stimulation parameters and stimulation sites to be determined.

Brainstem neuroimaging of nociception and pain circuitries

The brainstem is known to be an important brain area for nociception and pain processing, and both relaying and coordinating signaling between the cerebrum, cerebellum, and spinal cord. Although preclinical models of pain have characterized the many roles that brainstem nuclei play in nociceptive processing, the degree to which these circuitries extend to humans is not as well known. Unfortunately, the brainstem is also a very challenging region to evaluate in humans with neuroimaging. The challenges for human brainstem imaging arise from the location of this elongated brain structure, proximity to cardiorespiratory noise sources, and the size of its constituent nuclei. These challenges can require dedicated approaches to brainstem imaging, which should be adopted when study hypotheses are focused on brainstem processing of nociception or modulation of pain perception. In fact, our review will highlight many pain neuroimaging studies that have reported some brainstem involvement in nociceptive processing and chronic pain pathology. However, we note that with recent advances in neuroimaging leading to improved spatial and temporal resolution, more studies are needed that take advantage of data collection and analysis methods focused on the challenges of brainstem neuroimaging.

Attenuation of hypertension by C-fiber stimulation of the human median nerve and the concept-based novel device

High blood pressure (BP) is a highly controllable risk factor for cardiovascular diseases; however, awareness of this condition and the rates of controlled hypertension are low. Experimental animal studies have shown that stimulation of the median nerve or PC6 acupoint over the wrist has effects on cardiovascular activities, including reductions in systolic and diastolic BPs. A proof-of-concept study was conducted in humans to investigate whether stimulation of median nerve near PC6 acupoint decreased high BP, identify the optimal stimulation parameters for the BP-lowering effects of median nerve stimulation, and determine the specific peripheral nerves or types of afferent fibers mediating the BP-lowering effects. Median nerve stimulation was carried out bilaterally or unilaterally with different stimulation parameters, and the BP and heart rate were monitored. The afferent mechanisms underlying the effects of median nerve stimulation on hypertension were investigated via microneurography, A-fiber blocking experiments, and localized chemical or electrical stimulation. Bilateral median nerve stimulation at either low or high frequencies produced profound but transient reductions in systolic BP, which were elicited when median nerve stimulation was unilaterally applied at interelectrode distances of 2 and 4 cm. Systolic BP was also reduced by electrical stimulation of the thumb on the palm side. Although microneurographic recordings revealed the excitation of both A- and C-fibers following median nerve stimulation, the median nerve-mediated reductions in BP were not affected by A-fiber blockade, and they were mimicked by the activation of C-fibers with capsaicin. The present results indicate that activation of C-fibers in the median nerve generates BP-lowering effects in humans. Based on our clinical study, an optimized median nerve stimulator was built and combined with a wrist BP monitor for simultaneous BP measurements and median nerve stimulation.

Modulation of brainstem activity and connectivity by respiratory-gated auricular vagal afferent nerve stimulation in migraine patients

Migraine pathophysiology includes altered brainstem excitability, and recent neuromodulatory approaches aimed at controlling migraine episodes have targeted key brainstem relay and modulatory nuclei. In this study, we evaluated the impact of respiratory-gated auricular vagal afferent nerve stimulation (RAVANS), a novel neuromodulatory intervention based on an existing transcutaneous vagus nerve stimulation approach, in the modulation of brainstem activity and connectivity in migraine patients. We applied 3T-functional magnetic resonance imaging with improved in-plane spatial resolution (2.62 × 2.62 mm) in episodic migraine (interictal) and age- and sex-matched healthy controls to evaluate brain response to RAVANS (gated to either inhalation or exhalation) and sham stimulation. We further investigated RAVANS modulation of tactile trigeminal sensory afference response in the brainstem using air-puff stimulation directed to the forehead during functional magnetic resonance imaging. Compared with sham and inhalatory-gated RAVANS (iRAVANS), exhalatory-gated RAVANS (eRAVANS) activated an ipsilateral pontomedullary region consistent with nucleus tractus solitarii (NTS). During eRAVANS, NTS connectivity was increased to anterior insula and anterior midcingulate cortex, compared with both sham and iRAVANS, in migraine patients. Increased connectivity was inversely correlated with relative time to the next migraine attack, suggesting clinical relevance to this change in connectivity. Poststimulation effects were also noted immediately after eRAVANS, as we found increased activation in putative pontine serotonergic (ie, nucleus raphe centralis) and noradrenergic (ie, locus coeruleus) nuclei in response to trigeminal sensory afference. Regulation of activity and connectivity of brainstem and cortical regions involved in serotonergic and noradrenergic regulation and pain modulation may constitute an underlying mechanism supporting beneficial clinical outcomes for eRAVANS applied for episodic migraine.

Improvement of Olfactory Function With High Frequency Non-invasive Auricular Electrostimulation in Healthy Humans

In past literature on animal models, invasive vagal nerve stimulation using high frequencies has shown to be effective at modulating the activity of the olfactory bulb (OB). Recent advances in invasive vagal nerve stimulation in humans, despite previous findings in animal models, used low frequency stimulation and found no effect on the olfactory functioning. The present article aimed to test potential effects of non-invasive, high and low frequency vagal nerve stimulation in humans, with supplementary exploration of the orbitofrontal cortex using near-infrared spectroscopy (NIRS). Healthy, male adult participants (n = 18) performed two olfactory tests [odor threshold test (OTT) and supra-threshold test (STT)] before and after receiving high-, low frequency vagal nerve stimulation and placebo (no stimulation). Participant's olfactory functioning was monitored using NIRS, and assessed with two behavioral olfactory tests. NIRS data of separate stimulation parameters were statistically analyzed using repeated-measures ANOVA across different stages. Data from olfactory tests were analyzed using paired parametric and non-parametric statistical tests. Only high frequency, non-invasive vagal nerve stimulation was able to positively modulate the performance of the healthy participants in the STT (p = 0.021, Wilcoxon sign-ranked test), with significant differences in NIRS (p = 0.014, post-hoc with Bonferroni correction) recordings of the right hemispheric, orbitofrontal cortex. The results from the current article implore further exploration of the neurocircuitry involved under vagal nerve stimulation and the effects of non-invasive, high frequency, vagal nerve stimulation toward olfactory dysfunction which showcase in Parkinson's and Alzheimer's Diseases. Despite the sufficient effect size (moderate effect, correlation coefficient (r): 0.39 for the STT) of the current study, future research should replicate the current findings with a larger cohort.

Challenges and opportunities for brainstem neuroimaging with ultrahigh field MRI

The human brainstem plays a central role in connecting the cerebrum, the cerebellum and the spinal cord to one another, hosting relay nuclei for afferent and efferent signaling, and providing source nuclei for several neuromodulatory systems that impact central nervous system function. While the investigation of the brainstem with functional or structural magnetic resonance imaging has been hampered for years due to this brain structure's physiological and anatomical characteristics, the field has seen significant advances in recent years thanks to the broader adoption of ultrahigh-field (UHF) MRI scanning. In the present review, we focus on the advantages offered by UHF in the context of brainstem imaging, as well as the challenges posed by the investigation of this complex brain structure in terms of data acquisition and analysis. We also illustrate how UHF MRI can shed new light on the neuroanatomy and neurophysiology underlying different brainstem-based circuitries, such as the central autonomic network and neurotransmitter/neuromodulator systems, discuss existing and foreseeable clinical applications to better understand diseases such as chronic pain and Parkinson's disease, and explore promising future directions for further improvements in brainstem imaging using UHF MRI techniques.

Vagus Nerve Stimulator Placement in Dogs: Surgical Implantation Technique, Complications, Long-Term Follow-Up, and Practical Considerations

OBJECTIVE

To describe a modified implantation procedure of a vagus nerve stimulation (VNS) device in dogs and to report short- and long-term complications.

STUDY DESIGN

Descriptive, experimental study.

ANIMALS

Healthy, adult Beagle dogs (n = 10).

METHODS

A VNS Therapy(®) System was implanted in the left cervical region of anesthetized dogs. During and within 48 hours after surgery, electrocardiography (ECG) and impedance testing of the system were performed. Dogs were monitored daily and the impedance of the system was determined regularly until VNS devices were surgically removed 3 years after implantation.

RESULTS

The implantation procedure was successful in all dogs without intraoperative complications. ECG monitoring and impedance tests were within normal limits during and within 48 hours after surgery. Postoperative seroma formation was common (70%). One dog developed an irreversible Horner's syndrome leading to removal of the device 5 months after implantation. Another dog developed trauma-induced damage of the lead requiring surgical revision. The device could be safely removed in all dogs; however, electrodes were left in place to avoid nerve damage. At removal, the anchor tether was dislodged in 40% of dogs and the lead was twisted in 50% of dogs.

CONCLUSION

Implantation of a VNS Therapy(®) System is safe and feasible in dogs; however, seroma formation, twisting of the lead, and dislodgement of the anchor tether were common. Practical improvements in the technique include stable device placement, use of a compression bandage, and exercise restriction. Regular evaluation of lead impedance is important, as altered values can indicate serious complications.

The heart side of brain neuromodulation

Neuromodulation refers to invasive, minimally invasive or non-invasive techniques to stimulate discrete cortical or subcortical brain regions with therapeutic purposes in otherwise intractable patients: for example, thousands of advanced Parkinsonian patients, as well as patients with tremor or dystonia, benefited by deep brain stimulation (DBS) procedures (neural targets: basal ganglia nuclei). A new era for DBS is currently opening for patients with drug-resistant depression, obsessive-compulsive disorders, severe epilepsy, migraine and chronic pain (neural targets: basal ganglia and other subcortical nuclei or associative fibres). Vagal nerve stimulation (VNS) has shown clinical benefits in patients with pharmacoresistant epilepsy and depression. Non-invasive brain stimulation neuromodulatory techniques such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are also being increasingly investigated for their therapeutic potential in several neurological and psychiatric disorders. In this review, we first address the most common neural targets of each of the mentioned brain stimulation techniques, and the known mechanisms of their neuromodulatory action on stimulated brain networks. Then, we discuss how DBS, VNS, rTMS and tDCS could impact on the function of brainstem centres controlling vital functions, critically reviewing their acute and long-term effects on brain sympathetic outflow controlling heart function and blood pressure. Finally, as there is clear experimental evidence in animals that brain stimulation can affect autonomic and heart functions, we will try to give a critical perspective on how it may enhance our understanding of the cortical/subcortical mechanisms of autonomic cardiovascular regulation, and also if it might find a place among therapeutic opportunities in patients with otherwise intractable autonomic dysfunctions.

Electrical stimulation of the vagus nerve protects against cerebral ischemic injury through an anti-infammatory mechanism

Vagus nerve stimulation exerts protective effects against ischemic brain injury; however, the underlying mechanisms remain unclear. In this study, a rat model of focal cerebral ischemia was established using the occlusion method, and the right vagus nerve was given electrical stimulation (constant current of 0.5 mA; pulse width, 0.5 ms; frequency, 20 Hz; duration, 30 seconds; every 5 minutes for a total of 60 minutes) 30 minutes, 12 hours, and 1, 2, 3, 7 and 14 days after surgery. Electrical stimulation of the vagus nerve substantially reduced infarct volume, improved neurological function, and decreased the expression levels of tumor necrosis factor-α and interleukin-6 in rats with focal cerebral ischemia. The experimental findings indicate that the neuroprotective effect of vagus nerve stimulation following cerebral ischemia may be associated with the inhibition of tumor necrosis factor-α and interleukin-6 expression.

The appropriate use of neurostimulation: stimulation of the intracranial and extracranial space and head for chronic pain. Neuromodulation Appropriateness Consensus Committee

INTRODUCTION

The International Neuromodulation Society (INS) has identified a need for evaluation and analysis of the practice of neurostimulation of the brain and extracranial nerves of the head to treat chronic pain.

METHODS

The INS board of directors chose an expert panel, the Neuromodulation Appropriateness Consensus Committee (NACC), to evaluate the peer-reviewed literature, current research, and clinical experience and to give guidance for the appropriate use of these methods. The literature searches involved key word searches in PubMed, EMBASE, and Google Scholar dated 1970-2013, which were graded and evaluated by the authors.

RESULTS

The NACC found that evidence supports extracranial stimulation for facial pain, migraine, and scalp pain but is limited for intracranial neuromodulation. High cervical spinal cord stimulation is an evolving option for facial pain. Intracranial neurostimulation may be an excellent option to treat diseases of the nervous system, such as tremor and Parkinson's disease, and in the future, potentially Alzheimer's disease and traumatic brain injury, but current use of intracranial stimulation for pain should be seen as investigational.

CONCLUSIONS

The NACC concludes that extracranial nerve stimulation should be considered in the algorithmic treatment of migraine and other disorders of the head. We should strive to perfect targets outside the cranium when treating pain, if at all possible.

Blood pressure control with selective vagal nerve stimulation and minimal side effects

OBJECTIVE

Hypertension is the largest threat to patient health and a burden to health care systems. Despite various options, 30% of patients do not respond sufficiently to medical treatment. Mechanoreceptors in the aortic arch relay blood pressure (BP) levels through vagal nerve (VN) fibers to the brainstem and trigger the baroreflex, lowering the BP. Selective electrical stimulation of these nerve fibers reduced BP in rats. However, there is no technique described to localize and stimulate these fibers inside the VN without inadvertent stimulation of non-baroreceptive fibers causing side effects like bradycardia and bradypnea.

APPROACH

We present a novel method for selective VN stimulation to reduce BP without the aforementioned side effects. Baroreceptor compound activity of rat VN (n = 5) was localized using a multichannel cuff electrode, true tripolar recording and a coherent averaging algorithm triggered by BP or electrocardiogram.

MAIN RESULTS

Tripolar stimulation over electrodes near the barofibers reduced the BP without triggering significant bradycardia and bradypnea. The BP drop was adjusted to 60% of the initial value by varying the stimulation pulse width and duration, and lasted up to five times longer than the stimulation.

SIGNIFICANCE

The presented method is robust to impedance changes, independent of the electrode's relative position, does not compromise the nerve and can run on implantable, ultra-low power signal processors.

Non-invasive neuromodulation to improve gait in chronic multiple sclerosis: a randomized double blind controlled pilot trial

BACKGROUND

This study sought to examine the effect of targeted physical therapy with and without cranial nerve non-invasive neuromodulation (CN-NINM), on the walking ability of people with MS who exhibited a dysfunctional gait. We hypothesized that subjects who received electrical stimulation would have greater improvement than those who had a control device after a 14-week intervention. Gait disturbance is a common problem for people with multiple sclerosis (MS). Current management may include exercise, pharmacology, functional electrical stimulation, compensatory strategies, use of assistive devices, and implanted electrical devices. We have developed an effective rehabilitative strategy using neuromodulation of the cranial nerves via electrical stimulation of the tongue to enhance the plasticity of the brain.

METHODS

The study is a within-subject blinded randomized control design. Twenty chronic MS subjects with an identified gait disturbance were assigned to either an active or control group. Both groups completed a 14-week intervention program using a standardized combination of exercise and a device that provided electrical stimulation to the tongue. Those in the active group received electrical stimulation on the tongue that they could perceive. Those in the control group used a device that did not provide a physiologically significant stimulus and was not perceivable. Subjects were assessed with the Dynamic Gait Index (DGI).

RESULTS

The DGI scores improved for both groups. There were significant between-group differences, with the active group showing statistically greater improvement than the control group mean.

CONCLUSION

People with MS demonstrated improved gait with CN-NINM training in a pilot randomized controlled trial. This study suggests that tongue-based neurostimulation may amplify the benefits of exercise for improving gait in people with chronic MS.

Biologically based treatment approaches to the patient with resistant perinatal depression

This study aims to summarize the current state of knowledge regarding approaches to treatment-resistant depression in pregnancy and the postpartum period and to develop algorithms for ante- and postnatal management in cases of refractory major depression. PubMed, Scopus, Google Scholar, and the Cochrane Library databases were searched without temporal restriction. Search terms included pregnancy and depression, perinatal depression, postnatal depression, treatment resistance and depression, antipsychotics and pregnancy, antidepressants and pregnancy, and mood stabilizers and pregnancy. Abstracts were reviewed for relevance, and further articles were obtained from bibliographic citations. There is a significant subpopulation of patients in pregnancy and postpartum whose depressive symptoms do not respond to first-line treatments. No research studies have focused specifically on this population. Data extracted from studies on women with depressive symptoms in pregnancy suggest that in the absence of evidence on which to base clinical decisions, many are receiving combinations of psychotherapeutic medications that have not been specifically studied for use in pregnancy. Antidepressant use in pregnancy is well studied, but studies specifically addressing the case of the patient who does not respond to first-line treatments are absent. Research in this area is urgently needed. The authors review a number of possible therapeutic approaches to treatment-resistant depression in pregnancy and the postpartum period.

Brain correlates of phasic autonomic response to acupuncture stimulation: an event-related fMRI study

Autonomic nervous system (ANS) response to acupuncture has been investigated by multiple studies; however, the brain circuitry underlying this response is not well understood. We applied event-related fMRI (er-fMRI) in conjunction with ANS recording (heart rate, HR; skin conductance response, SCR). Brief manual acupuncture stimuli were delivered at acupoints ST36 and SP9, while sham stimuli were delivered at control location, SH1. Acupuncture produced activation in S2, insula, and mid-cingulate cortex, and deactivation in default mode network (DMN) areas. On average, HR deceleration (HR-) and SCR were noted following both real and sham acupuncture, though magnitude of response was greater following real acupuncture and inter-subject magnitude of response correlated with evoked sensation intensity. Acupuncture events with strong SCR also produced greater anterior insula activation than without SCR. Moreover, acupuncture at SP9, which produced greater SCR, also produced stronger sharp pain sensation, and greater anterior insula activation. Conversely, acupuncture-induced HR- was associated with greater DMN deactivation. Between-event correlation demonstrated that this association was strongest for ST36, which also produced more robust HR-. In fact, DMN deactivation was significantly more pronounced across acupuncture stimuli producing HR-, versus those events characterized by acceleration (HR+). Thus, differential brain response underlying acupuncture stimuli may be related to differential autonomic outflows and may result from heterogeneity in evoked sensations. Our er-fMRI approach suggests that ANS response to acupuncture, consistent with previously characterized orienting and startle/defense responses, arises from activity within distinct subregions of the more general brain circuitry responding to acupuncture stimuli.