Vagus nerve stimulation inhibits cortical spreading depression

Auricular Vagus Nerve Stimulation Mitigates Inflammation and Vasospasm in Subarachnoid Hemorrhage: A Randomized Trial

Background

Inflammation contributes to morbidity following subarachnoid hemorrhage (SAH). Transauricular vagus nerve stimulation (taVNS) offers a noninvasive approach to target the inflammatory response following SAH.

Methods

In this prospective, triple-blinded, randomized, controlled trial, twenty-seven patients were randomized to taVNS or sham stimulation. Blood and cerebrospinal fluid (CSF) were collected to quantify inflammatory markers. Cerebral vasospasm severity and functional outcomes (modified Rankin Scale, mRS) were analyzed.

Results

No adverse events occurred. Radiographic vasospasm was significantly reduced (p = 0.018), with serial vessel caliber measurements demonstrating a more rapid return to normal than sham (p < 0.001). In the taVNS group, TNF-α was significantly reduced in both plasma (days 7 and 10) and CSF (day 13); IL-6 was also significantly reduced in plasma (day 4) and CSF (day 13) (p < 0.05). Patients receiving taVNS had higher rates of favorable outcomes at discharge (38.4% vs 21.4%) and first follow-up (76.9% vs 57.1%), with significant improvement from admission to first follow-up (p = 0.014), unlike the sham group (p = 0.18). The taVNS group had a significantly lower rate of discharge to skilled nursing facility or hospice (p = 0.04).

Conclusion

taVNS is a non-invasive method of neuro- and systemic immunomodulation. This trial supports that taVNS following SAH can mitigate the inflammatory response, reduce radiographic vasospasm, and potentially improve functional and neurological outcomes. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT04557618.

Non-Invasive Vagal Nerve Stimulation Pre-Treatment Reduces Neurological Dysfunction After Closed Head Injury in Mice

Non-invasive vagus nerve stimulation (nVNS) has recently been suggested as a potential therapy for traumatic brain injury (TBI). We previously demonstrated that nVNS inhibits cortical spreading depolarization, the electrophysiological event underlying migraine aura, and is relevant to TBI. Our past work also suggests a role for interleukin-1 beta (IL-1β) in cognitive deficits after closed head injury (CHI) in mice. We show that nVNS pre-treatment suppresses CHI-associated spatial learning and memory impairment and prevents IL-1β activation in injured neurons, but not endothelial cells. In contrast, nVNS administered 10 min after CHI was ineffective. These data suggest that nVNS prophylaxis might ameliorate neuronal dysfunction associated with CHI in populations at high risk for concussive TBI.

Vagus nerve stimulation inhibits cortical spreading depression via glutamate-dependent TrkB activation mechanism in the nucleus tractus solitarius

BACKGROUND

Vagus nerve stimulation (VNS) was recently found to inhibit cortical spreading depression (CSD), the underlying mechanism of migraine aura, through activation of the nucleus tractus solitarius (NTS), locus coeruleus (LC) and dorsal raphe nucleus (DRN). The molecular mechanisms underlying the effect of VNS on CSD in these nuclei remain to be explored. We hypothesized that VNS may activate glutamate receptor-mediated tropomyosin kinase B (TrkB) signaling in the NTS, thereby facilitating the noradrenergic and serotonergic neurotransmission to inhibit CSD.

METHODS

To investigate the role of TrkB and glutamate receptors in non-invasive VNS efficacy on CSD, a validated KCl-evoked CSD rat model coupled with intra-NTS microinjection of selective antagonists, immunoblot and immunohistochemistry was employed.

RESULTS

VNS increased TrkB phosphorylation in the NTS. Inhibition of intra-NTS TrkB abrogated the suppressive effect of VNS on CSD and CSD-induced cortical neuroinflammation. TrkB was found colocalized with glutamate receptors in NTS neurons. Inhibition of glutamate receptors in the NTS abrogated VNS-induced TrkB activation. Moreover, the blockade of TrkB in the NTS attenuated VNS-induced activation of the LC and DRN.

CONCLUSIONS

VNS induces the activation of glutamate receptor-mediated TrkB signaling in the NTS, which might modulate serotonergic and norepinephrinergic innervation to the cerebral cortex to inhibit CSD and cortical inflammation.

Spreading depolarization suppression from inter-astrocytic gap junction blockade assessed with multimodal imaging and a novel wavefront detection scheme

Spreading depolarizations (SDs) are an enigmatic and ubiquitous co-morbidity of neural dysfunction. SDs are propagating waves of local field depolarization and increased extracellular potassium. They increase the metabolic demand on brain tissue, resulting in changes in tissue blood flow, and are associated with adverse neurological consequences including stroke, epilepsy, neurotrauma, and migraine. Their occurrence is associated with poor patient prognosis through mechanisms which are only partially understood. Here we show in vivo that two (structurally dissimilar) drugs, which suppress astroglial gap junctional communication, can acutely suppress SDs. We found that mefloquine hydrochloride (MQH), administered IP, slowed the propagation of the SD potassium waveform and intermittently led to its suppression. The hemodynamic response was similarly delayed and intermittently suppressed. Furthermore, in instances where SD led to transient tissue swelling, MQH reduced observable tissue displacement. Administration of meclofenamic acid (MFA) IP was found to reduce blood flow, both proximal and distal, to the site of SD induction, preceding a large reduction in the amplitude of the SD-associated potassium wave. We introduce a novel image processing scheme for SD wavefront localization under low-contrast imaging conditions permitting full-field wavefront velocity mapping and wavefront parametrization. We found that MQH administration delayed SD wavefront's optical correlates. These two clinically used drugs, both gap junctional blockers found to distinctly suppress SDs, may be of therapeutic benefit in the various brain disorders associated with recurrent SDs.

Vagus Nerve Stimulation in Ischemic Stroke

PURPOSE OF REVIEW

Vagus nerve stimulation (VNS) has emerged as a potential therapeutic approach for neurological and psychiatric disorders. In recent years, there has been increasing interest in VNS for treating ischemic stroke. This review discusses the evidence supporting VNS as a treatment option for ischemic stroke and elucidates its underlying mechanisms.

RECENT FINDINGS

Preclinical studies investigating VNS in stroke models have shown reduced infarct volumes and improved neurological deficits. Additionally, VNS has been found to reduce reperfusion injury. VNS may promote neuroprotection by reducing inflammation, enhancing cerebral blood flow, and modulating the release of neurotransmitters. Additionally, VNS may stimulate neuroplasticity, thereby facilitating post-stroke recovery. The Food and Drug Administration has approved invasive VNS (iVNS) combined with rehabilitation for ischemic stroke patients with moderate to severe upper limb deficits. However, iVNS is not feasible in acute stroke due to its time-sensitive nature. Non-invasive VNS (nVNS) may be an alternative approach for treating ischemic stroke. While the evidence from preclinical studies and clinical trials of nVNS is promising, the mechanisms through which VNS exerts its beneficial effects on ischemic stroke are still being elucidated. Therefore, further research is needed to better understand the efficacy and underlying mechanisms of nVNS in ischemic stroke. Moreover, large-scale randomized clinical trials are necessary to determine the optimal nVNS protocols, assess its long-term effects on stroke recovery and outcomes, and identify the potential benefits of combining nVNS with other rehabilitation strategies.

Effect of transcutaneous cervical vagus nerve stimulation on declarative and working memory in patients with Posttraumatic Stress Disorder (PTSD): A pilot study

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with changes in multiple neurophysiological systems, including verbal declarative memory deficits. Vagus Nerve Stimulation (VNS) has been shown in preliminary studies to enhance function when paired with cognitive and motor tasks. The purpose of this study was to analyze the effect of transcutaneous cervical VNS (tcVNS) on attention, declarative and working memory in PTSD patients.

METHODS

Fifteen PTSD patients were randomly assigned to active tcVNS (N = 8) or sham (N = 7) stimulation in a double-blinded fashion. Memory assessment tests including paragraph recall and N-back tests were performed to assess declarative and working memory function when paired with active/sham tcVNS once per month in a longitudinal study during which patients self-administered tcVNS/sham twice daily.

RESULTS

Active tcVNS stimulation resulted in a significant improvement in paragraph recall performance following pairing with paragraph encoding for PTSD patients at two months (p < 0.05). It resulted in a 91 % increase in paragraph recall performance within group (p = 0.03), while sham tcVNS exhibited no such trend in performance improvement. In the N-back study, positive deviations in accuracy, precision and recall measures on different day visits (7,34,64,94) of patients with respect to day 1 revealed a pattern of better performance of the active tcVNS population compared to sham VNS which did not reach statistical significance.

LIMITATIONS

Our sample size was small.

CONCLUSIONS

These preliminary results suggest that tcVNS improves attention, declarative and working memory, which may improve quality of life and productivity for patients with PTSD. Future studies are required to confirm these results.

Aura phenomena do not initiate migraine attacks-Findings from neuroimaging

OBJECTIVES/BACKGROUND

As cortical spreading depolarization (CSD) has been suggested to be the cause of migraine aura and as CSD can activate trigeminal nociceptive neurons in animals, it has been suggested that CSD may be the cause of migraine attacks. This raises the question of how migraine pain is generated in migraine attacks without aura and has led to the hypothesis that CSD may also occur in subcortical regions in the form of "silent" CSDs, and accordingly "silent auras".

METHODS

In this case study, we provide evidence for common neuronal alterations preceding headache attacks with and without aura in a male patient with migraine, who underwent daily event-correlated functional magnetic resonance imaging of trigeminal nociception for a period of 30 days. During these days the man experienced migraine attacks with and without aura.

RESULTS

Comparing the preictal phases between both attack types revealed a common hyperactivation of the hypothalamus (p < 0.01), which was already present 2 days before the actual attack.

CONCLUSION

The time frame of the central pathophysiological orchestration of migraine attacks, irrelevant of the presence of later aura, strongly suggests that the aura is an epiphenomenon that is unrelated and does not initiate headache attacks.

Non-Invasive Vagus Nerve Stimulation Improves Brain Lesion Volume and Neurobehavioral Outcomes in a Rat Model of Traumatic Brain Injury

Abstract Traumatic brain injury (TBI) continues to be a major cause of death and disability worldwide. This study assessed the effectiveness of non-invasive vagus nerve stimulation (nVNS) in reducing brain lesion volume and improving neurobehavioral performance in a rat model of TBI. Animals were randomized into three experimental groups: (1) TBI with sham stimulation treatment (Control), (2) TBI treated with five lower doses (2-min) nVNS, and (3) TBI treated with five higher doses (2 × 2-min) nVNS. We used the gammaCore nVNS device to deliver stimulations. Magnetic resonance imaging studies were performed 1 and 7 days post-injury to confirm lesion volume. We observed smaller brain lesion volume in the lower dose nVNS group compared with the control group on days 1 and 7. The lesion volume for the higher dose nVNS group was significantly smaller than either the lower dose nVNS or the control groups on days 1 and 7 post-injury. The apparent diffusion coefficient differences between the ipsilateral and contralateral hemispheres on day 1 were significantly smaller for the higher dose (2 × 2 min) nVNS group than for the control group. Voxel-based morphometry analysis revealed an increase in the ipsilateral cortical volume in the control group caused by tissue deformation and swelling. On day 1, these abnormal volume changes were 13% and 55% smaller in the lower dose and higher dose nVNS groups, respectively, compared with the control group. By day 7, nVNS dampened cortical volume loss by 35% and 89% in the lower dose and higher dose nVNS groups, respectively, compared with the control group. Rotarod, beam walking, and anxiety performances were significantly improved in the higher-dose nVNS group on day 1 compared with the control group. The anxiety indices were also improved on day 7 post-injury compared with the control and the lower-dose nVNS groups. In conclusion, the higher dose nVNS (five 2 × 2-min stimulations) reduced brain lesion volume to a level that further refined the role of nVNS therapy for the acute treatment of TBI. Should nVNS prove effective in additional pre-clinical TBI models and later in clinical settings, it would have an enormous impact on the clinical practice of TBI in both civilian and military settings, as it can easily be adopted into routine clinical practice.

Role of Vagus Nerve Stimulation in the Treatment of Chronic Pain

Vagus nerve stimulation (VNS) can modulate vagal activity and neuro-immune communication. Human and animal studies have provided growing evidence that VNS can produce analgesic effects in addition to alleviating refractory epilepsy and depression. The vagus nerve (VN) projects to many brain regions related to pain processing, which can be affected by VNS. In addition to neural regulation, the anti-inflammatory property of VNS may also contribute to its pain-inhibitory effects. To date, both invasive and noninvasive VNS devices have been developed, with noninvasive devices including transcutaneous stimulation of auricular VN or carotid VN that are undergoing many clinical trials for chronic pain treatment. This review aimed to provide an update on both preclinical and clinical studies of VNS in the management for chronic pain, including fibromyalgia, abdominal pain, and headaches. We further discuss potential underlying mechanisms for VNS to inhibit chronic pain.

Migraine and treatment-resistant depression

Migraine and major depressive disorders (MDD) or treatment resistant depression (TRD) represent a significant global burden and are often comorbid, further complicating diagnosis and treatment. Epidemiological studies have demonstrated a bidirectional relationship between migraine and MDD/TRD, with patients suffering from one disorder exhibiting a heightened risk of developing the other. This association is believed to result from shared genetic factors, neurotransmitter dysregulation, inflammation, hormonal alteration, and other conditions comorbid with both disorders. Emerging evidence suggests that therapeutics targeting common pathways in both disorders may be beneficial for comorbid patients. Novel therapeutics for migraine or MDD/TRD, such as calcitonin gene-related peptide (CGRP)-targeting therapy, onabotulinumtoxinA, ketamine/esketamine, vagus nerve stimulation or transcranial magnetic stimulation, may be helpful in selected patients with comorbid migraine-MDD/TRD. Nevertheless, continued efforts are needed to improve early detection and intervention, to better understand the complex interplay between genetic, environmental, and psychosocial factors contributing to this comorbidity, to identify novel therapeutic targets, and ultimately, to alleviate the disease burden caused by this comorbidity.

Nonpharmacological modulation of cortical spreading depolarization

AIMS

Cortical spreading depolarization (CSD) is a wave of pathologic neuronal dysfunction that spreads through cerebral gray matter, causing neurologic disturbance in migraine and promoting lesion development in acute brain injury. Pharmacologic interventions have been found to be effective in migraine with aura, but their efficacy in acutely injured brains may be limited. This necessitates the assessment of possible adjunctive treatments, such as nonpharmacologic methods. This review aims to summarize currently available nonpharmacological techniques for modulating CSDs, present their mechanisms of action, and provide insight and future directions for CSD treatment.

MAIN METHODS

A systematic literature review was performed, generating 22 articles across 3 decades. Relevant data is broken down according to method of treatment.

KEY FINDINGS

Both pharmacologic and nonpharmacologic interventions can mitigate the pathological impact of CSDs via shared molecular mechanisms, including modulating K⁺/Ca²⁺/Na⁺/Cl^- ion channels and NMDA, GABA_A, serotonin, and CGRP ligand-based receptors and decreasing microglial activation. Preclinical evidence suggests that nonpharmacologic interventions, including neuromodulation, physical exercise, therapeutic hypothermia, and lifestyle changes can also target unique mechanisms, such as increasing adrenergic tone and myelination and modulating membrane fluidity, which may lend broader modulatory effects. Collectively, these mechanisms increase the electrical initiation threshold, increase CSD latency, slow CSD velocity, and decrease CSD amplitude and duration.

SIGNIFICANCE

Given the harmful consequences of CSDs, limitations of current pharmacological interventions to inhibit CSDs in acutely injured brains, and translational potentials of nonpharmacologic interventions to modulate CSDs, further assessment of nonpharmacologic modalities and their mechanisms to mitigate CSD-related neurologic dysfunction is warranted.

Noninvasive vagus nerve stimulation for migraine: a systematic review and meta-analysis of randomized controlled trials

Background

Medication is commonly used to treat migraine. However, patients may experience adverse events or fail to respond to medication. In recent years, neuromodulation techniques have emerged as potential non-pharmacological therapy for migraine. This article focuses on a systematic review and meta-analysis of randomized controlled trials of non-invasive vagus nerve stimulation (n-VNS) for migraine to determine the efficacy, safety and tolerability of n-VNS.

Methods

We searched PUBMED, EMBASE, and Cochrane Center Register of Controlled Trials databases up to July 15, 2022. Primary outcomes were monthly reduced migraine/headache days, and pain-free rates within 2 h. Secondary outcomes were  ≥ 50% responder rate, headache intensity, monthly acute medication reduction days, and adverse events.

Results

Meta-analysis shows that non-invasive cervical vagus nerve stimulation (n-cVNS) significantly impacted ≥50% responder rate (OR, 1.64; 95% CI, 1.1 to 2.47; p = 0.02), but had no significant effect on reducing migraine days (MD, -0.46; 95% CI, -1.21 to 0.29; p = 0.23) and headache days (MD, -0.68; 95% CI, -1.52 to 0.16; p = 0.11). In contrast, low-frequency non-invasive auricular vagus nerve stimulation (n-aVNS) was found to significantly reduce the number of migraine days (MD, -1.8; 95% CI, -3.34 to -0.26; p = 0.02) and headache intensity (SMD, -0.7; 95% CI, -1.23 to -0.17; p = 0.009), but not the number of acute medication days per month (MD, -1.1; 95% CI, -3.84 to 1.64; p = 0.43). In addition, n-cVNS was found safe and well-tolerated in most patients.

Conclusion

These findings show that n-VNS is a promising method for migraine management.

Migraine: from pathophysiology to treatment

Migraine is an extremely disabling, common neurological disorder characterized by a complex neurobiology, involving a series of central and peripheral nervous system areas and networks. A growing increase in the understanding of migraine pathophysiology in recent years has facilitated translation of that knowledge into novel treatments, which are currently becoming available to patients in many parts of the world and are substantially changing the clinical approach to the disease. In the first part of this review, we will provide an up to date overview of migraine pathophysiology by analyzing the anatomy and function of the main regions involved in the disease, focusing on how these give rise to the plethora of symptoms characterizing the attacks and overall disease. The second part of the paper will discuss the novel therapeutic agents that have emerged for the treatment of migraine, including molecules targeting calcitonin gene-related peptide (gepants and monoclonal antibodies), serotonin 5-HT_1F receptor agonists (ditans) and non-invasive neuromodulation, as well as providing a brief overview of new evidence for classic migraine treatments.

Non-invasive neuromodulation of the cervical vagus nerve in rare primary headaches

Primary headache disorders can be remarkably disabling and the therapeutic options available are usually limited to medication with a high rate of adverse events. Here, we discuss the mechanism of action of non-invasive vagal nerve stimulation, as well as the findings of the main studies involving patients with primary headaches other than migraine or cluster headache, such as hemicrania continua, paroxysmal hemicrania, cough headache, or short-lasting neuralgiform headache attacks (SUNCT/SUNA), in a narrative analysis. A bibliographical search of low-prevalence disorders such as rare primary headaches retrieves a moderate number of studies, usually underpowered. Headache intensity, severity, and duration showed a clinically significant reduction in the majority, especially those involving indomethacin-responsive headaches. The lack of response of some patients with a similar diagnosis could be due to a different stimulation pattern, technique, or total dose. The use of non-invasive vagal nerve stimulation for the treatment of primary headache disorders represents an excellent option for patients with these debilitating and otherwise refractory conditions, or that cannot tolerate several lines of preventive medication, and should always be considered before contemplating invasive, non-reversible stimulation techniques.

Novel Migraine Treatments: A Review

Aims: To present a review of the mechanisms of action, available clinical data, and safety profiles of novel migraine therapeutics to inform practice. Methods: PubMed, Medline, and Google Scholar were searched for randomized controlled trials (24 publications), review articles (15 publications), and other pertinent literature (16 publications) discussing the novel migraine therapeutics available between the years 2010 and 2021. All publications were reviewed to assess the mechanism of action, relevant clinical data, and side effect profile for each novel treatment. Therapeutic gain was also recorded in studies that included a placebo arm. Results: A total of 55 studies were included in the final analysis. In the preventive treatment of migraine, novel medications target calcitonin gene-related peptide (CGRP) and fall into either the monoclonal anti-CGRP or gepant class. For the acute treatment of migraine, novel medications fall into either the ditan or gepant class. Several medical devices have been developed for the acute and preventive treatment of migraine. Conclusion: Novel therapeutics are available for both the prevention and acute treatment of migraine headaches. These new medications and neuromodulatory devices appear overall to be safe and effective in the management of migraine headaches.

Assessment of safety and feasibility of non-invasive vagus nerve stimulation for treatment of acute stroke

BACKGROUND

Non-invasive vagus nerve stimulation (nVNS) using a hand-held stimulator placed on the neck is an FDA-approved treatment for primary headache disorders. The safety of nVNS is unknown in stroke patients.

OBJECTIVE

To assess the safety and feasibility of nVNS for the acute treatment of stroke.

METHODS

TR-VENUS (clinicaltrials.gov identifier NCT03733431) was a randomized, sham-controlled, open-label, multicenter trial conducted in patients with acute ischemic stroke (IS) or intracerebral hemorrhage (ICH). Patients were randomly assigned to standard-dose nVNS, high-dose nVNS, or sham stimulation. The primary endpoint was a composite safety outcome defined as bradycardia or reduction in mean arterial blood pressure during treatment or progression of neurological or death within 24 h of treatment. The feasibility endpoints were the proportion of eligible subjects receiving nVNS within 6 h of symptom onset and the proportion completing all pre-specified treatment doses. Efficacy assessments included infarct growth from baseline to 24 h after treatment.

RESULTS

Sixty-nine patients (61 IS, 8 ICH) completed the study. The composite safety outcome was achieved in 32.0% in sham and 47.7% in nVNS group (p = 0.203). Treatment was initiated in all but two randomized patients. All dosed subjects received 100% of prespecified stimulations. A non-significant reduction in infarct growth was observed in the high-dose nVNS group (184.2% in sham vs. 63.3% in high-dose nVNS; p = 0.109).

CONCLUSIONS

The results of this study suggest that nVNS may be safe and feasible in the setting of acute stroke. These findings support further development of nVNS as a potential treatment for acute ischemic stroke.

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.

Short-pulsed micro-magnetic stimulation of the vagus nerve

Vagus nerve stimulation (VNS) is commonly used to treat drug-resistant epilepsy and depression. The therapeutic effect of VNS depends on stimulating the afferent vagal fibers. However, the vagus is a mixed nerve containing afferent and efferent fibers, and the stimulation of cardiac efferent fibers during VNS may produce a rare but severe risk of bradyarrhythmia. This side effect is challenging to mitigate since VNS, via electrical stimulation technology used in clinical practice, requires unique electrode design and pulse optimization for selective stimulation of only the afferent fibers. Here we describe a method of VNS using micro-magnetic stimulation (µMS), which may be an alternative technique to induce a focal stimulation, enabling a selective fiber stimulation. Micro-coils were implanted into the cervical vagus nerve in adult male Wistar rats. For comparison, the physiological responses were recorded continuously before, during, and after stimulation with arterial blood pressure (ABP), respiration rate (RR), and heart rate (HR). The electrical VNS caused a decrease in ABP, RR, and HR, whereas µM-VNS only caused a transient reduction in RR. The absence of an HR modulation indicated that µM-VNS might provide an alternative technology to VNS with fewer heart-related side effects, such as bradyarrhythmia. Numerical electromagnetic simulations helped estimate the optimal coil orientation with respect to the nerve to provide information on the electric field’s spatial distribution and strength. Furthermore, a transmission emission microscope provided very high-resolution images of the cervical vagus nerve in rats, which identified two different populations of nerve fibers categorized as large and small myelinated fibers.

The antinociceptive effect of manual acupuncture in the auricular branch of the vagus nerve in visceral and somatic acute pain models and its laterality dependence

AIMS

The vagus nerve provides an important route to the central nervous system, and its brain projections are involved in nociceptive control and pain perception. We investigated the effect of ABVN stimulation on the inhibition of nociceptive signaling and the role of the cholinergic system in its neurobiological effects in models of visceral-somatic pain in rats, as well as the potential difference in stimulus laterality.

MATERIALS AND METHODS

Male and female Wistar rats were pretreated with auricular acupuncture in the ABVN and submitted to the visceral-somatic nociception model by acetic acid or somatic nociception by formalin. Vagotomy and pharmacological tools were used to verify the participation of the cholinergic system in the experiments.

KEY FINDINGS

Acupuncture on the left, but not the right, in the ABVN inhibited nociceptive signaling in the visceral-somatic nociception model in male and female rats. Acupuncture on the left ABVN reduced the response time in the formalin test. The cervical vagotomy of the left branch, but not the right, also inhibited nociceptive signaling in the visceral-somatic nociception model and reduced the effect of ABVN stimulation. Furthermore, cholinergic antagonists reduced the left ABVN stimulation effects in the same model.

SIGNIFICANCE

Our data show that only the stimulation in the left ABVN is capable of producing antinociceptive effect in acute pain models in rats, and that it is dependent on the activation of the vagus nerve caudal to the nodose ganglion, as well as the muscarinic and nicotinic cholinergic receptors.

Neuromodulation Strategies to Reduce Inflammation and Improve Lung Complications in COVID-19 Patients

Since the outbreak of the COVID-19 pandemic, races across academia and industry have been initiated to identify and develop disease modifying or preventative therapeutic strategies has been initiated. The primary focus has been on pharmacological treatment of the immune and respiratory system and the development of a vaccine. The hyperinflammatory state (“cytokine storm”) observed in many cases of COVID-19 indicates a prognostically negative disease progression that may lead to respiratory distress, multiple organ failure, shock, and death. Many critically ill patients continue to be at risk for significant, long-lasting morbidity or mortality. The human immune and respiratory systems are heavily regulated by the central nervous system, and intervention in the signaling of these neural pathways may permit targeted therapeutic control of excessive inflammation and pulmonary bronchoconstriction. Several technologies, both invasive and non-invasive, are available and approved for clinical use, but have not been extensively studied in treatment of the cytokine storm in COVID-19 patients. This manuscript provides an overview of the role of the nervous system in inflammation and respiration, the current understanding of neuromodulatory techniques from preclinical and clinical studies and provides a rationale for testing non-invasive neuromodulation to modulate acute systemic inflammation and respiratory dysfunction caused by SARS-CoV-2 and potentially other pathogens. The authors of this manuscript have co-founded the International Consortium on Neuromodulation for COVID-19 to advocate for and support studies of these technologies in the current coronavirus pandemic.

Cortical Anoxic Spreading Depolarization During Cardiac Arrest is Associated with Remote Effects on Peripheral Blood Pressure and Postresuscitation Neurological Outcome

BACKGROUND

Spreading depolarizations (SDs) are self-propagating waves of neuronal and glial depolarizations often seen in neurological conditions in both humans and animal models. Because SD is thought to worsen neurological injury, the role of SD in a variety of cerebral insults has garnered significant investigation. Anoxic SD is a type of SD that occurs because of anoxia or asphyxia. Although asphyxia leading to a severe drop in blood pressure may affect cerebral hemodynamics and is widely known to cause anoxic SD, the effect of anoxic SD on peripheral blood pressure in the extremities has not been investigated. This relationship is especially important to understand for conditions such as circulatory shock and cardiac arrest that directly affect both peripheral and cerebral perfusion in addition to producing anoxic SD in the brain.

METHODS

In this study, we used a rat model of asphyxial cardiac arrest to investigate the role of anoxic SD on cerebral hemodynamics and metabolism, peripheral blood pressure, and the relationship between these variables in 8- to 12-week-old male rats. We incorporated a multimodal monitoring platform measuring cortical direct current simultaneously with optical imaging.

RESULTS

We found that during anoxic SD, there is decoupling of peripheral blood pressure from cerebral blood flow and metabolism. We also observed that anoxic SD may modify cerebrovascular resistance. Furthermore, shorter time difference between anoxic SDs measured at different locations in the same rat was associated with better neurological outcome on the basis of the recovery of electrocorticography activity (bursting) immediately post resuscitation and the neurological deficit scale score 24 h post resuscitation.

CONCLUSIONS

To our knowledge, this is the first study to quantify the relationship between peripheral blood pressure, cerebral hemodynamics and metabolism, and neurological outcome in anoxic SD. These results indicate that the characteristics of SD may not be limited to cerebral hemodynamics and metabolism but rather may also encompass changes in peripheral blood flow, possibly through a brain-heart connection, providing new insights into the role of anoxic SD in global ischemia and recovery.

Devices for Episodic Migraine: Past, Present, and Future

PURPOSE OF REVIEW

Historically, therapies for migraine have generally involved pharmacological treatments using non-selective or selective analgesics and preventive treatments. However, for many patients these treatments are not effective, while others prefer to use non-pharmacological-based therapies. To fill this need, over the last 15 years, neuromodulatory devices have entered the market for migraine treatment. Here, we will review the most recent findings for the use of these devices in the treatment of migraine.

RECENT FINDINGS

Non-invasive vagus nerve stimulation and spring-pulse transcranial magnetic stimulation are both cleared for the treatment of migraine, supported by preclinical studies that validate efficacy and mechanism of action, and complemented with clinical trial data. Other options also authorized for use include transcutaneous supraorbital nerve stimulation and remote electrical neuromodulation. Various options are available to treat migraine using authorized neuromodulatory devices. These data support their efficacy in the treatment of episodic migraine, although further studies are necessary to elucidate their mechanism of action and to provide rigor to clinical trial data.

Neuromodulation for Chronic Daily Headache

Purpose of Review

We reviewed the literature that explored the use of central and peripheral neuromodulation techniques for chronic daily headache (CDH) treatment.

Recent Findings

Although the more invasive deep brain stimulation (DBS) is effective in chronic cluster headache (CCH), it should be reserved for extremely difficult-to-treat patients. Percutaneous occipital nerve stimulation has shown similar efficacy to DBS and is less risky in both CCH and chronic migraine (CM). Non-invasive transcutaneous vagus nerve stimulation is a promising add-on treatment for CCH but not for CM. Transcutaneous external trigeminal nerve stimulation may be effective in treating CM; however, it has not yet been tested for cluster headache. Transcranial magnetic and electric stimulations have promising preventive effects against CM and CCH.

Summary

Although the precise mode of action of non-invasive neuromodulation techniques remains largely unknown and there is a paucity of controlled trials, they should be preferred to more invasive techniques for treating CDH.

Efficacy profile of noninvasive vagus nerve stimulation on cortical spreading depression susceptibility and the tissue response in a rat model

Background

Noninvasive vagus nerve stimulation (nVNS) has recently emerged as a promising therapy for migraine. We previously demonstrated that vagus nerve stimulation inhibits cortical spreading depression (CSD), the electrophysiological event underlying migraine aura and triggering headache; however, the optimal nVNS paradigm has not been defined.

Methods

Various intensities and doses of nVNS were tested to improve efficacy on KCl-evoked CSD frequency and electrical threshold of CSD in a validated rat model. Chronic efficacy was evaluated by daily nVNS delivery for four weeks. We also examined the effects of nVNS on neuroinflammation and trigeminovascular activation by western blot and immunohistochemistry.

Results

nVNS suppressed susceptibility to CSD in an intensity-dependent manner. Two 2-minute nVNS 5 min apart afforded the highest efficacy on electrical CSD threshold and frequency of KCl-evoked CSD. Daily nVNS for four weeks did not further enhance efficacy over a single nVNS 20 min prior to CSD. The optimal nVNS also attenuated CSD-induced upregulation of cortical cyclooxygenase-2, calcitonin gene-related peptide in trigeminal ganglia, and c-Fos expression in trigeminal nucleus caudalis.

Conclusions

Our study provides insight on optimal nVNS parameters to suppress CSD and suggests its benefit on CSD-induced neuroinflammation and trigeminovascular activation in migraine treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01384-1.

Migraine

Migraine is a common, chronic, disorder that is typically characterized by recurrent disabling attacks of headache and accompanying symptoms, including aura. The aetiology is multifactorial with rare monogenic variants. Depression, epilepsy, stroke and myocardial infarction are comorbid diseases. Spreading depolarization probably causes aura and possibly also triggers trigeminal sensory activation, the underlying mechanism for the headache. Despite earlier beliefs, vasodilation is only a secondary phenomenon and vasoconstriction is not essential for antimigraine efficacy. Management includes analgesics or NSAIDs for mild attacks, and, for moderate or severe attacks, triptans or 5HT_1B/1D receptor agonists. Because of cardiovascular safety concerns, unreliable efficacy and tolerability issues, use of ergots to abort attacks has nearly vanished in most countries. CGRP receptor antagonists (gepants) and lasmiditan, a selective 5HT1_F receptor agonist, have emerged as effective acute treatments. Intramuscular onabotulinumtoxinA may be helpful in chronic migraine (migraine on ≥15 days per month) and monoclonal antibodies targeting CGRP or its receptor, as well as two gepants, have proven effective and well tolerated for the preventive treatment of migraine. Several neuromodulation modalities have been approved for acute and/or preventive migraine treatment. The emergence of new treatment targets and therapies illustrates the bright future for migraine management.

Non-invasive vagus nerve stimulation for prevention of migraine: The multicenter, randomized, double-blind, sham-controlled PREMIUM II trial

AIM

Evaluate the efficacy and safety of non-invasive vagus nerve stimulation for migraine prevention.

METHODS

After completing a 4-week diary run-in period, adults who had migraine with or without aura were randomly assigned to receive active non-invasive vagus nerve stimulation or sham therapy during a 12-week double-blind period.

RESULTS

Of 336 enrolled participants, 113 (active, n = 56; sham, n = 57) completed ≥70 days of the double-blind period and were ≥66% adherent with treatment, comprising the prespecified modified intention-to-treat population. The COVID-19 pandemic led to early trial termination, and the population was ∼60% smaller than the statistical target for full power. Mean reduction in monthly migraine days (primary endpoint) was 3.12 for the active group and 2.29 days for the sham group (difference, -0.83; p = 0.2329). Responder rate (i.e. the percentage of participants with a ≥50% reduction in migraine days) was greater in the active group (44.87%) than the sham group (26.81%; p = 0.0481). Prespecified subgroup analysis suggested that participants with aura responded preferentially. No serious device-related adverse events were reported.

CONCLUSIONS

These results suggest clinical utility of non-invasive vagus nerve stimulation for migraine prevention, particularly for patients who have migraine with aura, and reinforce the well-established safety and tolerability profile of this therapy.Trial Registration: ClinicalTrials.gov (NCT03716505).

Gut microbiota and migraine

Migraine is a leading cause of disability among the adult population and is a significant burden on the economies of the world. Studies into the underlying causes of migraine have spanned centuries but its underlying mechanisms are still not fully understood. In recent years, accumulating evidence implicates that microbiota-mediated gut-brain crosstalk may contribute to the pathogenesis of migraine. This review provides a brief account of the history of migraine theories and summarizes the recent studies showing how gut microbiota is involved in the pathophysiology of migraine. Future research perspectives for better understanding the role of the gut microbiota in migraine are also discussed.

Therapeutic applications of transcutaneous auricular vagus nerve stimulation with potential for application in neurodevelopmental or other pediatric disorders

Non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) as a newly developed technique involves stimulating the cutaneous receptive field formed by the auricular branch of the vagus nerve in the outer ear, with resulting activation of vagal connections to central and peripheral nervous systems. Increasing evidence indicates that maladaptive neural plasticity may underlie the pathology of several pediatric neurodevelopmental and psychiatric disorders, such as autism spectrum disorder, attention deficit hyperactivity disorder, disruptive behavioral disorder and stress-related disorder. Vagal stimulation may therefore provide a useful intervention for treating maladaptive neural plasticity. In the current review we summarize the current literature primarily on therapeutic use in adults and discuss the prospects of applying taVNS as a therapeutic intervention in specific pediatric neurodevelopmental and other psychiatric disorders. Furthermore, we also briefly discuss factors that would help optimize taVNS protocols in future clinical applications. We conclude from these initial findings that taVNS may be a promising alternative treatment for pediatric disorders which do not respond to other interventions.

Transcutaneous Cervical Vagal Nerve Stimulation in Patients with Posttraumatic Stress Disorder (PTSD): A Pilot Study of Effects on PTSD Symptoms and Interleukin-6 Response to Stress

BACKGROUND

Posttraumatic stress disorder (PTSD) is a highly disabling condition associated with alterations in multiple neurobiological systems, including increases in inflammatory and sympathetic function, responsible for maintenance of symptoms. Treatment options including medications and psychotherapies have limitations. We previously showed that transcutaneous Vagus Nerve Stimulation (tcVNS) blocks inflammatory (interleukin (IL)-6) responses to stress in PTSD. The purpose of this study was to assess the effects of tcVNS on PTSD symptoms and inflammatory responses to stress.

METHODS

Twenty patients with PTSD were randomized to double blind active tcVNS (N=9) or sham (N=11) stimulation in conjunction with exposure to personalized traumatic scripts immediately followed by active or sham tcVNS and measurement of IL-6 and other biomarkers of inflammation. Patients then self administered active or sham tcVNS twice daily for three months. PTSD symptoms were measured with the PTSD Checklist (PCL) and the Clinician Administered PTSD Scale (CAPS), clinical improvement with the Clinical Global Index (CGI) and anxiety with the Hamilton Anxiety Scale (Ham-A) at baseline and one-month intervals followed by a repeat of measurement of biomarkers with traumatic scripts. After three months patients self treated with twice daily open label active tcVNS for another three months followed by assessment with the CGI.

RESULTS

Traumatic scripts increased IL-6 in PTSD patients, an effect that was blocked by tcVNS (p<.05). Active tcVNS treatment for three months resulted in a 31% greater reduction in PTSD symptoms compared to sham treatment as measured by the PCL (p=0.013) as well as hyperarousal symptoms and somatic anxiety measured with the Ham-A p<0.05). IL-6 increased from baseline in sham but not tcVNS. Open label tcVNS resulted in improvements measured with the CGI compared to the sham treatment period p<0.05).

CONCLUSIONS

These preliminary results suggest that tcVNS reduces inflammatory responses to stress, which may in part underlie beneficial effects on PTSD symptoms.

Non-invasive neuromodulation in the acute treatment of migraine: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

A systematic review and meta-analysis was performed to determine the efficacy of non-invasive neuromodulation modalities for the treatment of acute migraine.

BACKGROUND

Although pharmacological treatments are the gold standard for the management of acute migraine, some patients may require non-pharmacological treatment options. Non-invasive neuromodulation may provide an alternative, and techniques include transcranial magnetic stimulation (TMS), non-invasive vagal nerve stimulation (nVNS), non-painful remote electrical stimulation (NRES), and external trigeminal nerve stimulation (e-TNS).

METHODS

This systematic review and meta-analysis was performed following PRISMA guidelines. We searched PUBMED, EMBASE, ClinicalTrials.gov, Cochrane Center Register of Controlled Trials, and LILACS databases. We included randomized controlled clinical trials studying patients with migraine treated with any form of non-invasive neuromodulation. Primary outcome was pain freedom within 2 h post-treatment. Secondary outcomes were pain relief within 2-h post-treatment and sustained pain freedom and sustained pain relief 48 h post-treatment.

RESULTS

Pooled analysis demonstrated a significant effect of non-invasive neuromodulation on pain-free rates within 2 h (RR, 1.66; 95% CI, 1.35 to 2.05; P < 0.00001) and pain relief rates within 2 h (RR, 1.52; 95% CI, 1.13 to 2.05; P = 0.005) post-treatment. Non-invasive neuromodulation had no significant effect on sustained pain freedom at 48 h (RR, 1.56; 95% CI, 0.68 to 3.59; P = 0.29) or sustained pain relief at 48 h (RR, 1.47; 95% CI, 0.57 to 3.77; P = 0.43) after administration.

CONCLUSION

Neuromodulation has demonstrated some efficacy in acute migraine management and may be considered in the treatment paradigm of acute migraine in patients with contraindications to pharmacological therapies.

Potential roles of vagus nerve stimulation on traumatic brain injury: Evidence from in vivo and clinical studies

Traumatic Brain Injury (TBI) is a one of the leading causes of death and disability worldwide. The consequences of TBI can be divided into two stages: 1) the immediate neuronal destruction during the initial trauma, resulting in the primary brain injury and pathophysiologic sequelae, and 2) the secondary brain injury, encompassing mitochondrial dysfunction, inflammation, cellular excitotoxicity, oxidative stress, and cortical edema, resulting in increased intracranial pressure (ICP) with exacerbated brain damage. Although the pathophysiology in TBI has been thoroughly investigated, the effectivity of therapeutic approaches for TBI is still lacking. Vagus nerve stimulation (VNS) has been used for treating medical refractory epilepsy and chronic drug-resistant depression. Several previous studies also demonstrated that VNS has beneficial effects for TBI in animal models and patients. The neuroprotective effects of VNS on TBI are possibly explained through several mechanisms, including a noradrenergic mechanism, anti-inflammatory effects, regulation of neurotransmitters, and attenuation of blood brain barrier breakdown, and brain edema. The aims of this review are to summarize and discuss the current evidence pertinent to the effect of VNS on both primary and secondary brain injury following TBI from both in vivo and clinical studies.

Assessment of the Use of Multi-Channel Organic Electrodes to Record ENG on Small Nerves: Application to Phrenic Nerve Burst Detection

Effective closed-loop neuromodulation relies on the acquisition of appropriate physiological control variables and the delivery of an appropriate stimulation signal. In particular, electroneurogram (ENG) data acquired from a set of electrodes applied at the surface of the nerve may be used as a potential control variable in this field. Improved electrode technologies and data processing methods are clearly needed in this context. In this work, we evaluated a new electrode technology based on multichannel organic electrodes (OE) and applied a signal processing chain in order to detect respiratory-related bursts from the phrenic nerve. Phrenic ENG (pENG) were acquired from nine Long Evans rats in situ preparations. For each preparation, a 16-channel OE was applied around the phrenic nerve’s surface and a suction electrode was applied to the cut end of the same nerve. The former electrode provided input multivariate pENG signals while the latter electrode provided the gold standard for data analysis. Correlations between OE signals and that from the gold standard were estimated. Signal to noise ratio (SNR) and ROC curves were built to quantify phrenic bursts detection performance. Correlation score showed the ability of the OE to record high-quality pENG. Our methods allowed good phrenic bursts detection. However, we failed to demonstrate a spatial selectivity from the multiple pENG recorded with our OE matrix. Altogether, our results suggest that highly flexible and biocompatible multi-channel electrode may represent an interesting alternative to metallic cuff electrodes to perform nerve bursts detection and/or closed-loop neuromodulation.

Low-Intensity Pulsed Ultrasound Stimulation Inhibits Cortical Spreading Depression

Cortical spreading depression (CSD), which is closely correlated with migraine aura, cerebral ischemia, seizure, and brain injury, is a spreading wave of neuronal and glial depolarization. The purpose of this study is to investigate whether low-intensity pulsed ultrasound stimulation (PUS) inhibits CSD by modulating neural activity and hemodynamics. Behavioral test, intrinsic signal optical imaging and western blot analysis were used for evaluating the inhibition effect of PUS on CSD in rat. We found that: 1) 30 min of PUS can significantly improve motor activity of rat with CSD. 2) Both 30 s and 30 min of PUS can significantly reduce count and propagation speed of CSD in rat and the inhibitory effect was enhanced with increase of ultrasound intensity. 3) 30 min of PUS significantly enhanced levels of brain-derived neurotrophic factor protein in brain tissue with CSD. These results suggest that PUS has the potential to treat brain disorders associated with CSD.

Updated review on the link between cortical spreading depression and headache disorders

INTRODUCTION

Experimental animal studies have revealed mechanisms that link cortical spreading depression (CSD) to the trigeminal activation mediating lateralized headache. However, conventional CSD as seen in lissencephalic brain is insufficient to explain some clinical features of aura and migraine headache.

AREAS COVERED

The importance of CSD in headache development including dysfunction of the thalamocortical network, neuroinflammation, calcitonin gene-related peptide, transgenic models, and the role of CSD in migraine triggers, treatment options, neuromodulation and future directions are reviewed.

EXPERT OPINION

The conventional understanding of CSD marching across the hemisphere is invalid in gyrencephalic brains. Thalamocortical dysfunction and interruption of functional cortical network systems by CSD, may provide alternative explanations for clinical manifestations of migraine phases including aura. Not all drugs showing CSD blocking properties in lissencephalic brains, have efficacy in migraine headache and monoclonal antibodies against CGRP ligand/receptors which are effective in migraine treatment, have no impact on aura in humans or CSD properties in rodents. Functional networks and molecular mechanisms mediating and amplifying the effects of limited CSD in migraine brain remain to be investigated to define new targets.

Noninvasive Neuromodulation in Headache: An Update

Background

Migraine is a common disabling primary headache condition. Although strives have been made in treatment, there remains an unmet need for safe, effective acute, and preventative treatments. The promising concept of neuromodulation of relevant neuronal targets in a noninvasive fashion for the treatment of primary headache disorders has led to the trial of numerous devices over the years.

Objective

We aimed to review the evidence on current neuromodulation treatments available for the management of primary headache disorders.

Methods

Randomized controlled trial as well as open-label and real-world studies on central and peripheral cephalic and noncephalic neuromodulation modalities in primary headaches were critically reviewed.

Results

The current evidence suggests a role of single-pulse transcranial magnetic stimulation, supraorbital nerve stimulation, and remote noncephalic electrical stimulation as migraine abortive treatments, with stronger evidence in episodic rather than in chronic migraine. Single-pulse transcranial magnetic stimulation and supraorbital nerve stimulation also hold promising evidence in episodic migraine prevention and initial positive evidence in chronic migraine prevention. More evidence should clarify the therapeutic role of the external vagus nerve stimulation and transcranial direct current stimulation in migraine. However, external vagus nerve stimulation may be effective in the acute treatment of episodic but not chronic cluster headache, in the prevention of hemicrania continua and paroxysmal hemicrania but not of short-lasting neuralgiform headache attacks. The difficulty in setting up sham-controlled studies has thus far prevented the publication of robust trials. This limitation along with the cost of these therapies has meant that their use is limited in most countries.

Conclusion

Neuromodulation is a promising nonpharmacological treatment approach for primary headaches. More studies with appropriate blinding strategies and reduction of device cost may allow more widespread approval of these treatments and in turn increase clinician's experience in neuromodulation.

Vagus nerve stimulation inhibits cortical spreading depression exclusively through central mechanisms

Experimental and clinical data strongly support vagus nerve stimulation (VNS) as a novel treatment in migraine. Vagus nerve stimulation acutely suppresses cortical spreading depression (CSD) susceptibility, an experimental model that has been used to screen for migraine therapies. However, mechanisms underlying VNS efficacy on CSD are unknown. Here, we interrogated the central and peripheral mechanisms using VNS delivered either invasively (iVNS) or noninvasively (nVNS) in male Sprague-Dawley rats. Cortical spreading depression susceptibility was evaluated 40 minutes after the stimulation. iVNS elevated the electrical CSD threshold more than 2-fold and decreased KCl-induced CSD frequency by 22% when delivered to intact vagus nerve. Distal vagotomy did not alter iVNS efficacy (2-fold higher threshold and 19% lower frequency in iVNS vs sham). By contrast, proximal vagotomy completely abolished iVNS effect on CSD. Pharmacological blockade of nucleus tractus solitarius, the main relay for vagal afferents, by lidocaine or glutamate receptor antagonist CNQX also prevented CSD suppression by nVNS. Supporting a role for both norepinephrine and serotonin, CSD suppression by nVNS was inhibited by more than 50% after abrogating norepinephrinergic or serotonergic neurotransmission alone using specific neurotoxins; abrogating both completely blocked the nVNS effect. Our results suggest that VNS inhibits CSD through central afferents relaying in nucleus tractus solitarius and projecting to subcortical neuromodulatory centers providing serotonergic and norepinephrinergic innervation to the cortex.

The bottom-up approach: Non-invasive peripheral neurostimulation methods to treat migraine: A scoping review from the child neurologist's perspective

Migraine is a common and invalidating disorder worldwide. Patients of all ages experience the disorder as very impairing regarding their personal and occupational lives. The current approach in migraine therapy is multimodal including lifestyle management, psychoeducation and, if available, psychotherapeutic interventions, and pharmacotherapy. The lack of non-pharmacological and non-invasive treatment options call for new and innovative therapeutic approaches. Peripheral neurostimulation is a relatively new method in migraine management offering a painless and non-pharmacological way of targeting specific mechanisms involved in migraine. This review summarizes 15 recent randomized clinical trials to provide an overview of non-invasive peripheral neurostimulation methods currently available for the treatment of migraine. Efficacy, tolerability, and safety of the different interventions and their feasibility in the pediatric setting are evaluated. Vagal nerve stimulation (VNS), remote electrical neuromodulation (REN) and supraorbital nerve stimulation (SNS) are considered effective in treating acute migraine attacks, the latter being more pronounced in migraine without aura. Regarding migraine prevention, occipital nerve stimulation (ONS) and supraorbital nerve stimulation (SNS) demonstrated efficacy, whereas repetitive neuromuscular magnetic stimulation (rNMS) may represent a further effective option in episodic migraine. REN and rNMS were found to be well-accepted with fewer patients discontinuing treatment than those receiving direct cranial nerve stimulation. In summary, peripheral neurostimulation represents a promising option to complement the multimodal therapy concept for pediatric migraine. In particular, rNMS opens a new field for research and treatment fitting the requirements of "non-invasiveness" for children. Given the reported efficacy, safety, and feasibility, the therapy decision should be made on an individual level.

Vagus nerve stimulation in brain diseases: Therapeutic applications and biological mechanisms

Brain diseases, including neurodegenerative, cerebrovascular and neuropsychiatric diseases, have posed a deleterious threat to human health and brought a great burden to society and the healthcare system. With the development of medical technology, vagus nerve stimulation (VNS) has been approved by the Food and Drug Administration (FDA) as an alternative treatment for refractory epilepsy, refractory depression, cluster headaches, and migraines. Furthermore, current evidence showed promising results towards the treatment of more brain diseases, such as Parkinson's disease (PD), autistic spectrum disorder (ASD), traumatic brain injury (TBI), and stroke. Nonetheless, the biological mechanisms underlying the beneficial effects of VNS in brain diseases remain only partially elucidated. This review aims to delve into the relevant preclinical and clinical studies and update the progress of VNS applications and its potential mechanisms underlying the biological effects in brain diseases.

Is Noninvasive Vagus Nerve Stimulation a Safe and Effective Alternative to Medication for Acute Migraine Control?

BACKGROUND

Noninvasive neuromodulation devices have been used for a variety of headache disorders, including cluster and migraine, since recently being cleared by the Federal Drug Administration. Although these devices have been touted as low-risk options for improved headache control, the data behind actual efficacy endpoints remain unclear.

OBJECTIVE

To critically assess current evidence regarding the efficacy of the noninvasive vagus nerve stimulator (nVNS) device for acute migraine management.

METHODS

The objective was addressed through the development of a structured critically appraised topic. This included a clinical scenario with a clinical question, literature search strategy, critical appraisal, results, evidence summary, commentary, and bottom line conclusions.Participants included consultant and resident neurologists, a medical librarian, clinical epidemiologists, and a content expert in the field of headache.

RESULTS

A randomized, double-blind, sham-controlled clinical trial was selected for critical appraisal. In this trial, the primary endpoint (pain freedom at 120 min after use of nVNS for first acute migraine attack) was not met when compared with sham device (30.4% for nVNS vs. 19.7% for sham; P=0.067). However, there were statistically significant differences found for various secondary endpoints favoring nVNS, such as pain freedom rates at 30 and 60 minutes, pain relief at 120 minutes, and mean percentage pain score reduction rates at 60 and 120 minutes.

CONCLUSIONS

When comparing nVNS with sham, no statistically significant differences were found with regards to the primary endpoint of pain freedom at 120 minutes, although differences were found with various secondary endpoints and post hoc analysis. nVNS is likely a safe alternative to medications.

Characterization of opioidergic mechanisms related to the anti-migraine effect of vagus nerve stimulation

Vagus nerve stimulation (VNS) is a promising neuromodulation approach used in the treatment of migraine, whose therapeutic mechanism is largely unknown. Previous studies suggest that VNS's anti-nociceptive effects may, in part, involve engaging opioidergic mechanisms. We used a validated preclinical model of head pain, with good translational outcomes in migraine, acute intracranial-dural stimulation, which has responded to invasive VNS. We tested the effects of μ (MOR), δ (DOR) and κ (KOR) opioid receptor agonists in this model, and subsequently the effects of opioid receptor antagonists against VNS-mediated neuronal inhibition. MOR, DOR, and KOR agonists all inhibited dural-evoked trigeminocervical neuronal responses. Both DOR and KOR agonists also inhibited ongoing spontaneous firing of dural responsive neurons. Both DOR and KOR agonists were more efficacious than the MOR agonist in this model. We confirm the inhibitory effect of invasive VNS and demonstrate that this effect was prevented by a broad-spectrum opioid receptor antagonist, and by a highly selective DOR antagonist. Our data confirm the role of MOR in dural-trigeminovascular neurotransmission and additionally provide evidence of a role of both DOR and KOR in dural-nociceptive transmission of trigeminocervical neurons. Further, the results here provide evidence of engagement of opioidergic mechanisms in the therapeutic action of VNS in headache, specifically the DOR. These studies provide further support for the important role of the DOR in headache mechanisms, and as a potential therapeutic target. The data begin to dissect the mode of action of the analgesic effects of VNS in the treatment of primary headache disorders.

The Instant Effects of Continuous Transcutaneous Auricular Vagus Nerve Stimulation at Acupoints on the Functional Connectivity of Amygdala in Migraine without Aura: A Preliminary Study

Background

A growing body of evidence suggests that both auricular acupuncture and transcutaneous auricular vagus nerve stimulation (taVNS) can induce antinociception and relieve symptoms of migraine. However, their instant effects and central treatment mechanism remain unclear. Many studies proved that the amygdalae play a vital role not only in emotion modulation but also in pain processing. In this study, we investigated the modulation effects of continuous taVNS at acupoints on the FC of the bilateral amygdalae in MwoA.

Methods

Thirty episodic migraineurs were recruited for the single-blind, crossover functional magnetic resonance imaging (fMRI) study. Each participant attended two kinds of eight-minute stimulations, taVNS and sham-taVNS (staVNS), separated by seven days in random order. Finally, 27 of them were included in the analysis of seed-to-voxel FC with the left/right amygdala as seeds.

Results

Compared with staVNS, the FC decreased during taVNS between the left amygdala and left middle frontal gyrus (MFG), left dorsolateral superior frontal gyrus, right supplementary motor area (SMA), bilateral paracentral lobules, bilateral postcingulum gyrus, and right frontal superior medial gyrus, so did the FC of the right amygdala and left MFG. A significant positive correlation was observed between the FC of the left amygdala and right SMA and the frequency/total time of migraine attacks during the preceding four weeks.

Conclusion

Continuous taVNS at acupoints can modulate the FC between the bilateral amygdalae and pain-related brain regions in MwoA, involving the limbic system, default mode network, and pain matrix, with obvious differences between the left amygdala and the right amygdala. The taVNS may produce treatment effects by modulating the abnormal FC of the amygdala and pain networks, possibly having the same central mechanism as auricular acupuncture.

Transcutaneous vagal nerve stimulation blocks stress-induced activation of Interleukin-6 and interferon-γ in posttraumatic stress disorder: A double-blind, randomized, sham-controlled trial

Posttraumatic stress disorder (PTSD) is a highly disabling condition associated with alterations in multiple neurobiological systems, including increases in inflammatory function. Vagus nerve stimulation (VNS) decreases inflammation, however few studies have examined the effects of non-invasive VNS on physiology in human subjects, and no studies in patients with PTSD. The purpose of this study was to assess the effects of transcutaneous cervical VNS (tcVNS) on inflammatory responses to stress. Thirty subjects with a history of exposure to traumatic stress with (N ​= ​10) and without (N ​= ​20) PTSD underwent exposure to stressful tasks immediately followed by active or sham tcVNS and measurement of multiple biomarkers of inflammation (interleukin-(IL)-6, IL-2, IL-1β, Tumor Necrosis Factor alpha (TNFα) and Interferon gamma (IFNγ) over multiple time points. Stressful tasks included exposure to personalized scripts of traumatic events on day 1, and public speech and mental arithmetic (Mental Stress) tasks on days 2 and 3. Traumatic scripts were associated with a pattern of subjective anger measured with Visual Analogue Scales and increased IL-6 and IFNγ in PTSD patients that was blocked by tcVNS (p ​< ​.05). Traumatic stress had minimal effects on these biomarkers in non-PTSD subjects and there was no difference between tcVNS or sham. No significant differences were seen between groups in IL-2, IL-1β, or TNFα. These results demonstrate that tcVNS blocks behavioral and inflammatory responses to stress reminders in PTSD.

Effect of transcutaneous cervical vagus nerve stimulation on the pituitary adenylate cyclase-activating polypeptide (PACAP) response to stress: A randomized, sham controlled, double blind pilot study

Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide that plays a key role in the neurobiology of the stress response, and prior studies suggest that its function is dysregulated in post-traumatic stress disorder (PTSD). Transcutaneous cervical vagus nerve stimulation (tcVNS) acts through PACAP and other neurobiological systems to modulate stress responses and/or symptoms of PTSD. In this pilot study, we examined the effects of tcVNS on PACAP in a three day chronic stress laboratory paradigm involving serial traumatic and mental stress exposures in healthy individuals with a history of exposure to psychological trauma (n ​= ​18) and patients with PTSD (n ​= ​12).

Methods

A total of 30 subjects with a history of exposure to psychological trauma experience were recruited (12 with PTSD diagnosis) for a three-day randomized double-blinded study of tcVNS or sham stimulation. Subjects underwent a protocol that included both personalized trauma recall and non-personalized mental stressors (public speaking, mental arithmetic) paired to tcVNS or sham stimulation over three days. Blood was collected at baseline and multiple time points after exposure to stressors. Linear mixed-effects models were used to assess changes in PACAP over time (in response to stressors) and its relation to active tcVNS or sham stimulation.

Results

PACAP blood levels increased over the course of three days for both active tcVNS and sham groups. This increase was statistically-significant in the sham group at the end of the second (Cohen’s d_rm ​= ​0.35, p ​= ​0.04), and third days (d_rm ​= ​0.41, p ​= ​0.04), but not in the active tcVNS group (d_rm ​= ​0.21, d_rm ​= ​0.18, and p ​> ​0.20).

Conclusion

These pilot findings suggest tcVNS may attenuate this neurobiological stress-response. Larger studies are needed to investigate gender and interaction effects.

•

We examined the effects of tcVNS on PACAP in a three day chronic stress paradigm involving traumatic and mental stress.

•

PACAP levels increased over the course of three days for both groups, the elevation of PACAP was larger in the sham group.

•

These findings suggest that tcVNS may be a potential intervention for stress-related psychiatric disorders.

NOn-invasive Vagus nerve stimulation in acute Ischemic Stroke (NOVIS): a study protocol for a randomized clinical trial

Background

Secondary damage due to neurochemical and inflammatory changes in the penumbra in the first days after ischemic stroke contributes substantially to poor clinical outcome. In animal models, vagus nerve stimulation (VNS) inhibits these detrimental changes and thereby reduces tissue injury. The aim of this study is to investigate whether non-invasive cervical VNS (nVNS) in addition to the current standard treatment can improve penumbral recovery and limit final infarct volume.

Methods

NOVIS is a single-center prospective randomized clinical trial with blinded outcome assessment. One hundred fifty patients will be randomly allocated (1:1) within 12 h from clinical stroke onset to nVNS for 5 days in addition to standard treatment versus standard treatment alone. The primary endpoint is the final infarct volume on day 5 assessed with MRI.

Discussion

We hypothesize that nVNS will result in smaller final infarct volumes as compared to standard treatment due to improved penumbral recovery. The results of this study will be used to assess the viability and approach to power a larger trial to more definitively assess the clinical efficacy of nVNS after stroke.

Trial registration

ClinicalTrials.govNCT04050501. Registered on 8 August 2019

Transcutaneous cervical vagal nerve stimulation reduces sympathetic responses to stress in posttraumatic stress disorder: A double-blind, randomized, sham controlled trial

Objective

Exacerbated autonomic responses to acute stress are prevalent in posttraumatic stress disorder (PTSD). The purpose of this study was to assess the effects of transcutaneous cervical VNS (tcVNS) on autonomic responses to acute stress in patients with PTSD. The authors hypothesized tcVNS would reduce the sympathetic response to stress compared to a sham device.

Methods

Using a randomized double-blind approach, we studied the effects of tcVNS on physiological responses to stress in patients with PTSD (n = 25) using noninvasive sensing modalities. Participants received either sham (n = 12) or active tcVNS (n = 13) after exposure to acute personalized traumatic script stress and mental stress (public speech, mental arithmetic) over a three-day protocol. Physiological parameters related to sympathetic responses to stress were investigated.

Results

Relative to sham, tcVNS paired to traumatic script stress decreased sympathetic function as measured by: decreased heart rate (adjusted β = -5.7%; 95% CI: ±3.6%, effect size d = 0.43, p < 0.01), increased photoplethysmogram amplitude (peripheral vasodilation) (30.8%; ±28%, 0.29, p < 0.05), and increased pulse arrival time (vascular function) (6.3%; ±1.9%, 0.57, p < 0.0001). Similar (p < 0.05) autonomic, cardiovascular, and vascular effects were observed when tcVNS was applied after mental stress or without acute stress.

Conclusion

tcVNS attenuates sympathetic arousal associated with stress related to traumatic memories as well as mental stress in patients with PTSD, with effects persisting throughout multiple traumatic stress and stimulation testing days. These findings show that tcVNS has beneficial effects on the underlying neurophysiology of PTSD. Such autonomic metrics may also be evaluated in daily life settings in tandem with tcVNS therapy to provide closed-loop delivery and measure efficacy.ClinicalTrials.gov Registration # NCT02992899.

Application of Noninvasive Vagal Nerve Stimulation to Stress-Related Psychiatric Disorders

BACKGROUND

Vagal Nerve Stimulation (VNS) has been shown to be efficacious for the treatment of depression, but to date, VNS devices have required surgical implantation, which has limited widespread implementation.

METHODS

New noninvasive VNS (nVNS) devices have been developed which allow external stimulation of the vagus nerve, and their effects on physiology in patients with stress-related psychiatric disorders can be measured with brain imaging, blood biomarkers, and wearable sensing devices. Advantages in terms of cost and convenience may lead to more widespread implementation in psychiatry, as well as facilitate research of the physiology of the vagus nerve in humans. nVNS has effects on autonomic tone, cardiovascular function, inflammatory responses, and central brain areas involved in modulation of emotion, all of which make it particularly applicable to patients with stress-related psychiatric disorders, including posttraumatic stress disorder (PTSD) and depression, since dysregulation of these circuits and systems underlies the symptomatology of these disorders.

RESULTS

This paper reviewed the physiology of the vagus nerve and its relevance to modulating the stress response in the context of application of nVNS to stress-related psychiatric disorders.

CONCLUSIONS

nVNS has a favorable effect on stress physiology that is measurable using brain imaging, blood biomarkers of inflammation, and wearable sensing devices, and shows promise in the prevention and treatment of stress-related psychiatric disorders.