Beneficial impact of visual stimulation-based digital therapeutics on blood pressure control in non-hypertensive individuals

Hypertension-related diseases occur in both hypertensive and non-hypertensive individuals. However, few studies to date have explored blood pressure (BP) control in non-hypertensive individuals. This before-after study aimed to examine the impact of visual stimulation-based digital therapeutics (VS-DTx) on BP and heart rate (HR). Eighty-three eligible non-hypertensive participants were included in this study. The McNemar test and Paired Samples Wilcoxon Signed Rank Test were employed to assess decline rates and differences in BP and HR between the control phase and the intervention (using VS-DTx) phase. Pairwise correlation analysis was used to analyze the correlation between the two phases. This study found the systolic BP (SBP) and mean arterial pressure (MAP) in the VS-DTx phase showed a downward trend (66.2% vs 49.3%; 68.7% vs 55.4%). The mean SBP decreased from 114.73 mm Hg to 111.18 mm Hg, and the mean MAP decreased from 87.96 mm Hg to 84.88 mm Hg in the VS-DTx phase. Paired Samples Wilcoxon Test showed differences in both ΔSBP (Z = -3.296; P < 0.01) and ΔMAP (Z = -2.386; P < 0.05) (Δ is defined as the difference between baseline and post-stimulus). The pairwise correlations analysis revealed that VS-DTx affected the MAP reduction (r = 0.33; P < 0.01) between the browsing digital devices phase and the VS-DTx phase. The results indicated that VS-DTx may have a certain effect on BP, including SBP and MAP. This study preliminarily explored the possible effects of VS-DTx on BP, providing certain useful insights for future research in digital BP management.

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.

Characterization of an Algorithm for Autonomous, Closed-Loop Neuromodulation During Motor Rehabilitation

BACKGROUND

Recent evidence demonstrates that manually triggered vagus nerve stimulation (VNS) combined with rehabilitation leads to increased recovery of upper limb motor function after stroke. This approach is premised on studies demonstrating that the timing of stimulation relative to movements is a key determinant in the effectiveness of this approach.

OBJECTIVE

The overall goal of the study was to identify an algorithm that could be used to automatically trigger VNS on the best movements during rehabilitative exercises while maintaining a desired interval between stimulations to reduce the burden of manual stimulation triggering.

METHODS

To develop the algorithm, we analyzed movement data collected from patients with a history of neurological injury. We applied 3 different algorithms to the signal, analyzed their triggering choices, and then validated the best algorithm by comparing triggering choices to those selected by a therapist delivering VNS therapy.

RESULTS

The dynamic algorithm triggered above the 95th percentile of maximum movement at a rate of 5.09 (interquartile range [IQR] = 0.74) triggers per minute. The periodic algorithm produces stimulation at set intervals but low movement selectivity (34.05%, IQR = 7.47), while the static threshold algorithm produces long interstimulus intervals (27.16 ± 2.01 seconds) with selectivity of 64.49% (IQR = 25.38). On average, the dynamic algorithm selects movements that are 54 ± 3% larger than therapist-selected movements.

CONCLUSIONS

This study shows that a dynamic algorithm is an effective strategy to trigger VNS during the best movements at a reliable triggering rate.

Efficacy of Vagal nerve stimulation on anxiety among elderly retired teachers during COVID-19 pandemic

BACKGROUND

Excessive fear, worry and behavioral disturbances define anxiety, with particular significance attributed to vagal nerve, a crucial transmitter of information to the brain regions governing anxiety. Highlighting the importance of vagal nerve, transcutaneous auricular vagal nerve stimulation (TaVNS) emerges as a tolerable and safe technique. The success of non-invasive vagal nerve stimulation in alleviating anxiety underscores the pivotal role of the vagal nerve.

OBJECTIVES

The purpose of this study was to assess the effectiveness of physiotherapy interventions in mitigating anxiety among retired teachers during the COVID-19 pandemic, emphasizing the relevance of targeting the vagal nerve for improved mental well-being.

METHODS

60 retired teachers diagnosed with anxiety were chosen through random allocation. Participants were divided into two groups: Group A (Experimental group) received transcutaneous auricular vagal nerve stimulation (TaVNS), and Group B (Control group) underwent the Jacobson relaxation technique. Intervention period spanned 4 weeks, with four sessions per week, lasting 30 minutes. The outcome measures included Generalized Anxiety Disorder-7 (GAD-7) questionnaire and salivary cortisol levels.

RESULTS

Following the 4-week intervention, both groups exhibited a significant reduction in Generalized Anxiety Disorder-7 (GAD-7) scores and salivary cortisol levels (P <  0.001). Notably, Group A demonstrated a significantly higher effectiveness rate compared to Group B.

CONCLUSION

The study concludes that transcutaneous auricular vagal nerve stimulation (TaVNS) is effective in reducing anxiety among retired teachers. Transcutaneous auricular vagal nerve stimulation (TaVNS) proves to be a powerful and effective intervention in alleviating anxiety among retired teachers, emphasizing its potential significance in enhancing mental well-being.

Noninvasive Transcutaneous Auricular Vagal Nerve Stimulation Improves Gastric Slow Waves Impaired by Cold Stress in Healthy Subjects

BACKGROUND/AIMS

Stress is known to inhibit gastric motility. The aim of this study was to investigate the effects and autonomic mechanisms of transcutaneous auricular vagal nerve stimulation (taVNS) on cold stress (CS)-induced impairment in gastric motility that are relevant to the brain-gut interactions in healthy volunteers.

MATERIALS AND METHODS

Healthy volunteers (eight women; age 28.2 ± 1.8 years) were studied in four randomized sessions (control, CS, CS + taVNS, and CS + sham-electrical stimulation [sham-ES]). Each session was composed of 30 minutes in the fasting state and 30 minutes after a standard test meal. CS was induced during minutes 10 to 30 after the meal, whereas taVNS or sham-ES was performed during minutes 0 to 30 after the meal. The electrogastrogram and electrocardiogram were recorded for assessing gastric slow waves and autonomic functions, respectively.

RESULTS

First, CS decreased the percentage of normal gastric slow waves (59.7% ± 9.8% vs 85.4% ± 4.5%, p < 0.001 vs control); this impairment was dramatically improved by taVNS (75.5% ± 6.3% vs 58.4% ± 12.5%, p < 0.001 vs sham-ES). Second, CS increased the symptom score (22.0 ± 12.1 vs 39.3 ± 11.5, p = 0.001 vs control); taVNS, but not sham-ES, reduced the symptom score (26.0 ± 12.2 vs 38.3 ± 21.6, p = 0.026 vs sham-ES). Third, CS decreased vagal activity assessed from the spectral analysis of heart rate variability (0.21 ± 0.10 vs 0.26 ± 0.11, p < 0.05 vs control) and increased the sympathovagal ratio (4.89 ± 1.94 vs 3.74 ± 1.32, p = 0.048 vs control); taVNS normalized CS-induced suppression in vagal activity (0.27 ± 0.13 vs 0.22 ± 0.10, p = 0.049 vs sham-ES; p > 0.05 vs control) and CS-induced increase in the sympathovagal ratio (3.28 ± 1.61 vs 4.28 ± 2.10, p = 0.042 vs sham-ES; p > 0.05 vs control).

CONCLUSION

The noninvasive taVNS improves the CS-induced impairment in gastric pace-making activity, possibly by reversing the detrimental effect of CS on autonomic functions. taVNS may have a therapeutic potential for stress-induced gastric dysmotility.

Vagus Nerve Stimulation Must Occur During Tactile Rehabilitation to Enhance Somatosensory Recovery

Chronic sensory loss is a common and undertreated consequence of many forms of neurological injury. Emerging evidence indicates that vagus nerve stimulation (VNS) delivered during tactile rehabilitation promotes recovery of somatosensation. Here, we systematically varied the timing of VNS relative to tactile rehabilitation to determine the paradigm that yields the greatest degree of somatosensory recovery after peripheral nerve injury (PNI). The medial and ulnar nerves in rats were transected, causing chronic sensory loss. Eight weeks after injury, rats were given a VNS implant followed by four weeks of tactile rehabilitation sessions consisting of repeated mechanical stimuli to the previously denervated forepaw. Rats received VNS before, during, or after tactile rehabilitation. Delivery of VNS during rehabilitative training generates robust, significant recovery compared to rehabilitative training without stimulation (56 ± 14% improvement over sham stimulation). A matched amount of VNS before training, immediately after training, or two hours after training is significantly less effective than VNS during rehabilitative training and fails to improve recovery compared to rehabilitative training alone (5 ± 10%, 4 ± 11%, and -7 ± 22% improvement over sham stimulation, respectively). These findings indicate that concurrent delivery of VNS during rehabilitative training is most effective and illustrate the importance of considering stimulation timing for clinical implementation of VNS therapy.

Nonlinear Closed-Loop Predictive Control of Heart Rate and Blood Pressure Using Vagus Nerve Stimulation: An In Silico Study

We propose a nonlinear model-based control technique for regulating the heart rate and blood pressure using vagus nerve neuromodulation. The closed-loop framework is based on an in silico model of the rat cardiovascular system for the simulation of the hemodynamic response to multi-location vagal nerve stimulation. The in silico model is derived by compartmentalizing the various physiological components involved in the closed-loop cardiovascular system with intrinsic baroreflex regulation to virtually generate nominal and hypertension-related heart dynamics of rats in rest and exercise states. The controller, using a reduced cycle-averaged model, monitors the outputs from the in silico model, estimates the current state of the reduced model, and computes the optimum stimulation locations and the corresponding parameters using a nonlinear model predictive control algorithm. The results demonstrate that the proposed control strategy is robust with respect to its ability to handle setpoint tracking and disturbance rejection in different simulation scenarios.

Selective efferent vagal stimulation in heart failure

Patients diagnosed with heart failure have high rates of mortality and morbidity. Based on promising preclinical studies, vagal nerve stimulation has been trialled in these patients using whole nerve electrical stimulation, but the results have been mixed. This is, at least in part, due to an inability to selectively recruit the activity of specific fibres within the vagus with whole nerve electrical stimulation, as well as not knowing which the 'therapeutic' fibres are. This symposium review focuses on a population of cardiac-projecting efferent vagal fibres with cell bodies located within the dorsal motor nucleus of the vagus nerve and a new method of selectively targeting these projections as a potential treatment in heart failure. NEW FINDINGS: What is the topic of this review? Selective efferent vagal stimulation in heart failure. What advances does it highlight? Selectively targeting a population of cardiac-projecting efferent vagal fibres with cell bodies within the dorsal motor nucleus of the vagus using optogenetics slows the progression of heart failure in rats.

Vagal Nerve Stimulation Reduces Ventricular Arrhythmias and Mitigates Adverse Neural Cardiac Remodeling Post-Myocardial Infarction

This study sought to evaluate the impact of chronic vagal nerve stimulation (cVNS) on cardiac and extracardiac neural structure/function after myocardial infarction (MI). Groups were control, MI, and MI + cVNS; cVNS was started 2 days post-MI. Terminal experiments were performed 6 weeks post-MI. MI impaired left ventricular mechanical function, evoked anisotropic electrical conduction, increased susceptibility to ventricular tachycardia and fibrillation, and altered neuronal and glial phenotypes in the stellate and dorsal root ganglia, including glial activation. cVNS improved cardiac mechanical function and reduced ventricular tachycardia/ventricular fibrillation post-MI, partly by stabilizing activation/repolarization in the border zone. MI-associated extracardiac neural remodeling, particularly glial activation, was mitigated with cVNS.

Effective Delivery of Vagus Nerve Stimulation Requires Many Stimulations Per Session and Many Sessions Per Week Over Many Weeks to Improve Recovery of Somatosensation

BACKGROUND

Chronic sensory loss is a common and undertreated consequence of many forms of neurological injury. Emerging evidence indicates that vagus nerve stimulation (VNS) delivered during tactile rehabilitation promotes recovery of somatosensation.

OBJECTIVE

Here, we characterize the amount, intensity, frequency, and duration of VNS therapy paradigms to determine the optimal dosage for VNS-dependent enhancement of recovery in a model of peripheral nerve injury (PNI).

METHODS

Rats underwent transection of the medial and ulnar nerves in the forelimb, resulting in chronic sensory loss in the paw. Eight weeks after injury, rats were implanted with a VNS cuff and received tactile rehabilitation sessions consisting of repeated mechanical stimulation of the previously denervated forepaw paired with short bursts of VNS. Rats received VNS therapy in 1 of 6 systematically varied dosing schedules to identify a paradigm that balanced therapy effectiveness with a shorter regimen.

RESULTS

Delivering 200 VNS pairings a day 4 days a week for 4 weeks produced the greatest percent improvement in somatosensory function compared to any of the 6 other groups (One Way analysis of variance at the end of therapy, F[4 70] P = .005).

CONCLUSIONS

Our findings demonstrate that an effective VNS therapy dosage delivers many stimulations per session, with many sessions per week, over many weeks. These results provide a framework to inform the development of VNS-based therapies for sensory restoration.

Transcutaneous electrical stimulation of auricular branch of the vagus nerve effectively and rapidly modulates the EEG patterns in patients with possible electrographic status epilepticus

BACKGROUND

Invasive vagal nerve stimulation (iVNS) is a known treatment approach for patients with refractory epilepsy. Transcutaneous auricular vagus nerve stimulation (tVNS) was developed to overcome the side effects and surgical complications of iVNS. tVNS is proven beneficial in refractory epilepsy. The effectiveness of tVNS, however, has never been studied in patients with Status Epilepticus. In this study, we explored the effect of tVNS in three patients with possible electrographic status epilepticus.

OBJECTIVES

To compare the EEG pattern before, during and after tVNS in three patients with possible electrographic status epilepticus.

METHODS

Three consecutive patients with possible electrographic status epilepticus were included after due consenting process. In addition to the standard care, tVNS was applied on the left ear over the cymba concha in two sessions, 6 h apart, with each session for 45 min. Continuous EEG monitoring was performed as standard of care and the findings before, during and after tVNS were documented.

RESULTS

The duration of status epilepticus at the time of inclusion of Patients 1, 2, and 3 was 6 weeks, 7 days, and 5 days respectively. All were in coma and on multiple antiseizure medications. Patient 1 and 3 were on anesthetic infusions. Before stimulation, one patient had burst suppression pattern and two had generalized periodic discharges at 1 Hz frequency. We observed a significant reduction/resolution of ongoing EEG patterns in all three patients during the stimulation. The abnormal patterns re-emerged approximately 20 min post cessation of tVNS. No stimulation-related side effects were detected. There was no change in clinical status, but all three patients had severe underlying conditions.

SIGNIFICANCE

Transcutaneous auricular Vagus Nerve Stimulation (tVNS) is a potential noninvasive adjuvant therapy that can modulate EEG patterns in patients with Status epilepticus. Larger studies in early SE are needed to assess its clinical benefits.

Acceleration of postoperative recovery with brief intraoperative vagal nerve stimulation mediated via the autonomic mechanism

Introduction

Postoperative recovery is largely dependent on the restoration of gastrointestinal motility. The aim of this study was to investigate the effects and mechanisms of intraoperative vagus nerve stimulation (iVNS) on postoperative recovery from abdominal surgery in rats.

Methods

The Nissen fundoplication surgery was performed on two groups of rats: sham-iVNS group and iVNS group (VNS was performed during surgery). Animal's behavior, eating, drinking and feces' conditions were monitored at specific postoperative days. Gastric slow waves (GSWs) and electrocardiogram (ECG) were recorded; blood samples were collected for the assessment of inflammatory cytokines.

Results

(1) iVNS shortened initiate times to water and food intake (p = 0.004) and increased the number of fecal pellets (p < 0.05, vs. sham-iVNS) and the percentage of water content in fecal pellets (p < 0.05). (2) iVNS improved gastric pace-making activity at 6 h after surgery reflected as a higher percentage of normal slow waves (p = 0.015, vs. sham-iVNS). (3) iVNS suppressed inflammatory cytokines at 24 h after surgery compared to sham-iVNS (TNF-α: p = 0.001; IL-1β: p = 0.037; IL-6: p = 0.002). (4) iVNS increased vagal tone compared to sham-iVNS group at 6 h and 24 h after the surgery (p < 0.05). Increased vagal tone was correlated with a faster postoperative recovery to start water and food intake.

Conclusion

Brief iVNS accelerates postoperative recovery by ameliorating postoperative animal behaviors, improving gastrointestinal motility and inhibiting inflammatory cytokines mediated via the enhanced vagal tone.

A Comparative Review of Vagal Nerve Stimulation Versus Baroreceptor Activation Therapy in Cardiac Diseases

Sympathetic imbalance coupled with impairment of baroreceptor control is a key factor responsible for hemodynamic abnormalities in congestive heart failure. Vagal nerve stimulation (VNS) and baroreceptor activation therapy (BAT) are two novel interventions for the same. In this paper, we review the role of sympathovagal alterations in cardiac diseases like heart failure, arrhythmia, hypertension (HTN), etc. Studies like neural cardiac therapy for heart failure (NECTAR-HF), autonomic regulation therapy to enhance myocardial function and reduce progression of heart failure (ANTHEM-HF), and baroreflex activation therapy for heart failure (BEAT-HF), which comprise the history, efficacy, limitations, and current protocols, were extensively analyzed in contrast to one another. Vagal nerve stimulation reverses the reflex inhibition of cardiac vagal efferent activity, which is caused as a result of sympathetic overdrive during the course for heart failure. It has shown encouraging results in certain pre-clinical studies; however, there is also a possibility of serious cardiovascular adverse events if given in higher than the recommended dosage. Attenuated baroreflex sensitivity is attributed to cardiac arrhythmogenesis during heart failure. Baroreceptor activation therapy reverses this phenomenon. However, the surgical procedure for baroreceptor stimulation can have unwarranted complications, including worsening heart failure and hypertension. Considering the effectiveness of the given modalities and taking into account the inconclusive evidence of their adverse events, more clinical trials are needed for establishing the future prospects of these interventional approaches.

The effects of transcutaneous auricular vagal nerve stimulation on cortical GABA-ergic and cholinergic circuits: a transcranial magnetic stimulation study

Neurophysiological evidence that transcutaneous auricular vagal nerve stimulation (taVNS) affects neuronal signaling at the cortical level is sparse. We used transcranial magnetic stimulation to assess the effect of taVNS on the excitability of intracortical GABA-ergic and cholinergic circuits. In this within-subject, double-blind study on 30 healthy participants, we used TMS paradigms to assess the effect of a single session of taVNS at 100Hz and sham earlobe VNS (sVNS) on short-interval intracortical inhibition (SICI) curve and short-latency afferent inhibition (SAI). Control experiment was performed on additional 15 participants using the same experimental settings, but delivering no stimulation (xVNS). Bayesian statistics were used to assess the differences, producing % values that reflect the certainty that the values of interest were decreased during or after stimulation compared to baseline. taVNS increased SICI (96.3%), whereas sVNS decreased SICI (1.2 %). SAI was not affected by taVNS, while it was decreased during sVNS (1.34% and 9.1 %, for interstimulus intervals 20 and 24ms, respectively). The changes in TMS parameters detected during sVNS were present in the same direction in the control experiment with no stimulation. Our study provides evidence that taVNS increases the activity of cortical GABA-A-ergic system, leaving cortical cholinergic circuits unaffected. Changes in intracortical cortical excitability during sVNS, which were also observed in the control experiment with no stimulation were likely the effect of expectation related to participation in an interventional study.

Vagal Nerve Stimulation: A Bibliometric Analysis of Current Research Trends

BACKGROUND

Vagal nerve stimulation (VNS) has become established as an effective tool for the management of various neurologic disorders. Consequently, a growing number of VNS studies have been published over the past four decades. This study presents a bibliometric analysis investigating the current trends in VNS literature.

MATERIALS AND METHODS

Using the Web of Science collection data base, a search was performed to identify literature that discussed applications of VNS from 2000 to 2021. Analysis and visualization of the included literature were completed with VOSviewer.

RESULTS

A total of 2895 publications were identified. The number of articles published in this area has increased over the past two decades, with the most citations (7098) occurring in 2021 and the most publications (270) in 2020. The h-index, i-10, and i-100 were 97, 994, and 91, respectively, with 17.0 citations per publication on average. The highest-producing country and institution of VNS literature were the United States and the University of Texas, respectively. The most productive journal was Epilepsia. Epilepsy was the predominant focus of VNS research, with the keyword "epilepsy" having the greatest total link strength (749) in the keyword analysis. The keyword analysis also revealed two major avenues of VNS research: 1) the mechanisms by which VNS modulates neural circuitry, and 2) therapeutic applications of VNS in a variety of diseases beyond neurology. It also showed a significant prevalence of noninvasive VNS research. Although epilepsy research appears more linked to implanted VNS, headache and depression specialists were more closely associated with noninvasive VNS.

CONCLUSION

VNS may serve as a promising intervention for rehabilitation beyond neurologic applications, with an expanding base of literature over the past two decades. Although epilepsy researchers have produced most current literature, other fields have begun to explore VNS as a potential treatment, likely owing to the rise of noninvasive forms of VNS.

Dynamic accentuated antagonism of heart rate control during different levels of vagal nerve stimulation intensity in rats

Accentuated antagonism refers to a phenomenon in which the vagal effect on heart rate (HR) is augmented by background sympathetic tone. The dynamic aspect of accentuated antagonism remains to be elucidated during different levels of vagal nerve stimulation (VNS) intensity. We performed VNS on anesthetized rats (n = 8) according to a binary white noise signal with a switching interval of 500 ms at three different stimulation rates (low-intensity: 0-10 Hz, moderate-intensity: 0-20 Hz, and high-intensity: 0-40 Hz). The transfer function from VNS to HR was estimated with and without concomitant tonic sympathetic nerve stimulation (SNS) at 5 Hz. The asymptotic low-frequency (LF) gain (in beats/min/Hz) of the transfer function increased with SNS regardless of the VNS rate [low-intensity: 3.93 ± 0.70 vs. 5.82 ± 0.65 (P = 0.021), moderate-intensity: 3.87 ± 0.62 vs. 5.36 ± 0.53 (P = 0.018), high-intensity: 4.77 ± 0.85 vs. 7.39 ± 1.36 (P = 0.011)]. Moreover, SNS slightly increased the ratio of high-frequency (HF) gain to the LF gain. These effects of SNS were canceled by the pretreatment of ivabradine, an inhibitor of hyperpolarization-activated cyclic nucleotide-gated channels, in another group of rats (n = 6). Although background sympathetic tone antagonizes the vagal effect on mean HR, it enables finer HR control by increasing the dynamic gain of the vagal HR transfer function regardless of VNS intensity. When interpreting the HF component of HR variability, the augmenting effect from background sympathetic tone needs to be considered.

Immediate Effects of Vagal Nerve Stimulation in Drug-Resistant Epilepsy Revealed by Magnetoencephalographic Recordings

Objective: Vagus nerve stimulation (VNS) has been a neuromodulatory option for treating drug-resistant epilepsy (DRE), but its mechanism remains unclear. To obtain insight into the mechanism by which VNS reduces epileptic seizures, the immediate effects of VNS in brain networks of DRE patients were investigated when the patients' vagal nerve stimulators were turned on. Methods: The brain network properties of 14 DRE patients with a vagal nerve stimulator and 14 healthy controls were evaluated using magnetoencephalography recordings for 6 main frequency bands. Results: Compared with healthy controls, DRE patients exhibited significant increases in functional connectivity in the theta, alpha, beta, and gamma bands and significant reductions in the small-world measure in the theta and beta bands. During periods when patients' vagal nerve stimulators were turned on, DRE patients showed significant reductions in functional connectivity in the theta and alpha bands and a significant increase in the small-world measure in the theta band when compared with periods when patients' vagal nerve stimulators were turned off. Conclusions: Our results indicate that the brain networks of DRE patients were pathologically hypersynchronous and instantaneous VNS can decrease the synchronization of brain networks of epileptic patients, which might play a key role in the mechanism by which VNS reduces epileptic seizures. In the theta band, instantaneous VNS can increase the network efficiency of DRE patients, and the increment in network efficiency may be helpful for improving brain cognitive function in epileptic patients. Impact statement For the first time, we investigated the immediate effects of vagus nerve stimulation (VNS) in the brain networks of drug-resistant epilepsy patients using magnetoencephalography. Our results show that instantaneous VNS can decrease the hypersynchronization of epileptic networks and increase the network efficiency of epileptic patients. Our results are helpful in understanding the mechanism of action by which VNS reduces epileptic seizures and improves the cognitive function in epileptic patients and the brain network reorganization caused by long-term VNS.

The Clinical Impact of Vagal Nerve Stimulator Implantation on Laryngopharyngeal Function in Children: A Single-Center Experience

OBJECTIVE

A vagal nerve stimulator (VNS) has been established as the treatment of choice for children with refractory epilepsy. The outcomes of the procedure have been well documented in adults but are less clear in children. The goal of our study was to review laryngopharyngeal (LP) function following VNS implantation in children.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary-care children's hospital.

METHODS

Voice, swallowing, and sleep apnea symptoms were extracted from the charts of children who underwent VNS implantation between 2013 and 2021. A questionnaire was sent to parents of implanted children to ascertain the degree of the social and functional impact of the implant.

RESULTS

There were 69 patients, aged 2.3 to 21.4 years old, who met the inclusion criteria. LP symptoms were most common during the first year following implantation; 26 patients (37.6%) demonstrated at least 1 symptom (voice alteration, chronic cough, sleep-disordered breathing, or dysphagia), and 15 patients required adjustments to their implant settings. The incidence of symptoms and the need to adjust VNS settings significantly dropped during years 2 to 5 and 6 to 8 (22% vs 7% and 5%, respectively, p = .0002). The mean score of the Pediatric Voice Handicap Index differed greatly from a normal control group on each subscale and the total score.

CONCLUSION

LP dysfunction in children following VNS implantation is comparable to adults, with the most burden noticed during the first year after implantation. The presence of voice alterations did not correlate with the presence of dysphagia and sleep-disordered breathing. Thorough evaluation, preferably by a multidisciplinary team, is required to assess LP dysfunction postoperatively.

Transcutaneous vagal nerve stimulation to treat disorders of consciousness: Protocol for a double-blind randomized controlled trial

Background

Patients with disorders of consciousness (DoC) are a challenging population prone to misdiagnosis with limited effective treatment options. Among neuromodulation techniques, transcutaneous auricular vagal nerve stimulation (taVNS) may act through a bottom-up manner to modulate thalamo-cortical connectivity and promote patients’ recovery. In this clinical trial, we aim to (1) assess the therapeutic clinical effects of taVNS in patients with DoC; (2) investigate the neural mechanisms underlying the effects of its action; (3) assess the feasibility and safety of the procedure in this challenging population; (4) define the phenotype of clinical responders; and (5) assess the long-term efficacy of taVNS in terms of functional outcomes.

Methods

We will conduct a prospective parallel randomized controlled double-blind clinical trial investigating the effects of taVNS as a treatment in DoC patients. Forty-four patients in the early period post-injury (7 to 90 days following the injury) will randomly receive 5 days of either active bilateral vagal stimulation (45 min duration with 30s alternative episodes of active/rest periods; 3mA; 200-300μs current width, 25Hz.) or sham stimulation. Behavioural (i.e., Coma Recovery Scale-Revised, CRS-R) and neurophysiological (i.e., high-density electroencephalography, hd-EEG) measures will be collected at baseline and at the end of the 5-day treatment. Analyses will seek for changes in the CRS-R and the EEG metrics (e.g., alpha band power spectrum, functional connectivity) at the group and individual (i.e., responders) levels.

Discussion

These results will allow us to investigate the vagal afferent network and will contribute towards a definition of the role of taVNS for the treatment of patients with DoC. We aim to identify the neural correlates of its action and pave the way to novel targeted therapeutic strategies.

Clinical trial registration

Clinicaltrials.gov n° NCT04065386.

Leveraging Accelerometry as a Prognostic Indicator for Increase in Opioid Withdrawal Symptoms

Treating opioid use disorder (OUD) is a significant healthcare challenge in the United States. Remaining abstinent from opioids is challenging for individuals with OUD due to withdrawal symptoms that include restlessness. However, to our knowledge, studies of acute withdrawal have not quantified restlessness using involuntary movements. We hypothesized that wearable accelerometry placed mid-sternum could be used to detect withdrawal-related restlessness in patients with OUD. To study this, 23 patients with OUD undergoing active withdrawal participated in a protocol involving wearable accelerometry, opioid cues to elicit craving, and non-invasive Vagal Nerve Stimulation (nVNS) to dampen withdrawal symptoms. Using accelerometry signals, we analyzed how movements correlated with changes in acute withdrawal severity, measured by the Clinical Opioid Withdrawal Scale (COWS). Our results revealed that patients demonstrating sinusoidal-i.e., predominantly single-frequency oscillation patterns in their motion almost exclusively demonstrated an increase in the COWS, and a strong relationship between the maximum power spectral density and increased withdrawal over time, measured by the COWS (R = 0.92, p = 0.029). Accelerometry may be used in an ambulatory setting to indicate the increased intensity of a patient's withdrawal symptoms, providing an objective, readily-measurable marker that may be captured ubiquitously.

Anti-inflammatory effects of vagal nerve stimulation with a special attention to intestinal barrier dysfunction

The vagus nerve (VN), the longest nerve of the organism innervating the gastrointestinal tract, is a mixed nerve with anti-inflammatory properties through its afferents, activating the hypothalamic-pituitary adrenal axis, and its efferents through the cholinergic anti-inflammatory pathway inhibiting the release of pro-inflammatory cytokines (e.g., TNFα) by splenic and gut macrophages. In addition, the VN is also able to modulate the permeability of the intestinal barrier although the VN does not innervate directly the intestinal epithelium. Targeting the VN through VN stimulation (VNS) has been developed in experimental model of intestinal inflammation and in inflammatory bowel disease (IBD) and might be of interest to decrease intestinal permeability in gastrointestinal disorders with intestinal barrier defect such as IBD, irritable bowel syndrome (IBS), and celiac disease. In this issue of neurogastroenterology and motility, Mogilevski et al. report that a brief non-invasive transcutaneous auricular VNS in healthy volunteers consistently reduces the permeability of the small intestine induced by intravenous administration of the stress peptide corticotropin releasing hormone, known to increase intestinal permeability and to inhibit the VN. In this review, we outline the mechanistic underpinning the effect of stress, of the VN and VNS on intestinal permeability. In particular, the VN can act on intestinal permeability through enteric nerves, and/or cells such as enteric glial cells. We also review the existing evidence of the effects VNS on intestinal permeability in models such as burn intestinal injury and traumatic brain injury, which pave the way for future clinical trials in IBD, IBS, and celiac disease.

Proarrhythmic Effects of Sympathetic Activation Are Mitigated by Vagal Nerve Stimulation in Infarcted Hearts

OBJECTIVES

The goal of this study was to evaluate whether intermittent VNS reduces electrical heterogeneities and arrhythmia inducibility during sympathoexcitation.

BACKGROUND

Sympathoexcitation increases the risk of ventricular tachyarrhythmias (VT). Vagal nerve stimulation (VNS) has been antiarrhythmic in the setting of ischemia-driven arrhythmias, but it is unclear if it can overcome the electrophysiological effects of sympathoexcitation in the setting of chronic myocardial infarction (MI).

METHODS

In Yorkshire pigs after chronic MI, a sternotomy was performed, a 56-electrode sock was placed over the ventricles (n = 17), and a basket catheter was positioned in the left ventricle (n = 6). Continuous unipolar electrograms from sock and basket arrays were obtained to analyze activation recovery interval (ARI), a surrogate of action potential duration. Bipolar voltage mapping was performed to define scar, border zone, or viable myocardium. Hemodynamic and electrical parameters and VT inducibility were evaluated during sympathoexcitation with bilateral stellate ganglia stimulation (BSS) and during combined BSS with intermittent VNS.

RESULTS

During BSS, global epicardial ARIs shortened from 384 ± 59 milliseconds to 297 ± 63 milliseconds and endocardial ARIs from 359 ± 36 milliseconds to 318 ± 40 milliseconds. Dispersion in ARIs increased in all regions, with the greatest increase observed in scar and border zone regions. VNS mitigated the effects of BSS on border zone ARIs (from -18.3% ± 6.3% to -2.1% ± 14.7%) and ARI dispersion (from 104 ms² [1 to 1,108 ms²] to -108 ms² [IQR: -588 to 30 ms²]). VNS reduced VT inducibility during sympathoexcitation (from 75%-40%; P < 0.05).

CONCLUSIONS

After chronic MI, VNS overcomes the detrimental effects of sympathoexcitation by reducing electrophysiological heterogeneities exacerbated by sympathetic stimulation, decreasing VT inducibility.

Asystole During Elective Cervical Spine Surgery: A Case Study

A 52-year-old, ASA class II patient was scheduled for anterior cervical discectomy and fusion at the C3 - C4 level. During the surgery when the surgeon was placing retractors the patient developed an instant onset of asystole. This case review will discuss potential reasons for asystole during cervical spinal surgery, as well as anatomical considerations when confronted with asystole during surgical dissection and retraction. Many complications resulting from asystole have poor prognosis. This case study will review what was done in a timely manner to recognize and treat this life-threatening event.

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.