Vagus Nerve Stimulation with Mild Stimulation Intensity Exerts Anti-Inflammatory and Neuroprotective Effects in Parkinson's Disease Model Rats

Transcutaneous auricular vagus nerve stimulation improves cortical functional topological properties and intracortical facilitation in patients with Parkinson's disease

Our study aimed to investigate the neural mechanisms of taVNS in the motor symptoms of PD, focusing on the topological properties of cortical functional networks and cortical excitability. Thirty-two PD patients underwent functional near-infrared spectroscopy and transcranial magnetic stimulation evaluation prior to and after two-week taVNS, which were controlled by 20 healthy controls (HCs). PD patients exhibited decreased nodal efficiency (Ne) in the right M1 and increased Ne in the left pre-motor and supplementary motor area compared with HCs. The decreased Ne in the right M1 was negatively associated with UPDRS-III scores. Interestingly, taVNS treatment improved PD motor symptoms by increasing Ne in the right M1 and enhancing intracortical facilitation (ICF, ISI 10, and 15 ms). The increased Ne and ICF (ISI 15 ms) were negatively correlated with the decreased UPDRS-III scores. taVNS could improve nodal information processing efficiency in the M1 and enhance cortical facilitation to improve PD motor disorders.

Transcutaneous vagus nerve stimulation for Parkinson's disease: a systematic review and meta-analysis

Background

Transcutaneous vagus nerve stimulation (tVNS) has emerged as a novel noninvasive adjunct therapy for advanced Parkinson's disease (PD), yet no quantitative analysis had been conducted to assess its therapeutic effect.

Objectives

This review aimed to investigate the efficacy of tVNS on motor function, other potential clinical targets and its safety in various treatment conditions.

Methods

We searched six databases for randomized controlled trials (RCTs) that involved treating PD patients with tVNS. Primary outcome was motor functions, including severity of motor signs, functional mobility and balance, and gait parameters. Secondary outcomes were cognition, emotion, sleep related impairments, patient reported non-motor outcomes, and any adverse events. All outcomes were classified and analyzed according to the treatment duration and medication condition of an included study. Risk of bias was evaluated by referencing Cochrane risk of bias tool 1.0. Data was analyzed by Revman 5.4.

Results

6 RCTs with 176 PD patient were included. Several motor functions and non-motor functions measured during on-medication condition (severity of motor signs -0.48 [95% CI -0.93, -0.04], gait -0.48 [95% CI -0.85, -0.1], patients reported non-motor outcomes -0.4 [95% CI -0.78, -0.03]), improved significantly. However, verbal fluency, sleep-related impairment, and fatigue were negatively impacted by tVNS during on-medication condition. No distinct adverse events were reported.

Conclusion

tVNS is a relatively safe adjunct treatment for PD. It has small to moderate therapeutic effects on motor functions and may negatively impact on a few other outcomes. Quality level of the evidence is low and further research is warranted.

Systematic review registration

https://www.crd.york.ac.uk/prospero/#recordDetails, identifier CRD42024503322 (PROSPERO).

Non-invasive vagus nerve stimulation in anti-inflammatory therapy: mechanistic insights and future perspectives

Non-invasive vagus nerve stimulation (VNS) represents a transformative approach for managing a broad spectrum of inflammatory and autoimmune conditions, including rheumatoid arthritis and inflammatory bowel disease. This comprehensive review delineates the mechanisms underlying VNS, emphasizing the cholinergic anti-inflammatory pathway, and explores interactions within the neuro-immune and vagus-gut axes based on both clinical outcomes and pre-clinical models. Clinical applications have confirmed the efficacy of VNS in managing specific autoimmune diseases, such as rheumatoid arthritis, and chronic inflammatory conditions like inflammatory bowel disease, showcasing the variability in stimulation parameters and patient responses. Concurrently, pre-clinical studies have provided insights into the potential of VNS in modulating cardiovascular and broader inflammatory responses, paving the way for its translational application in clinical settings. Innovations in non-invasive VNS technology and precision neuromodulation are enhancing its therapeutic potential, making it a viable option for patients who are unresponsive to conventional treatments. Nonetheless, the widespread adoption of this promising therapy is impeded by regulatory challenges, patient compliance issues, and the need for extensive studies on long-term efficacy and safety. Future research directions will focus on refining VNS technology, optimizing treatment parameters, and exploring synergistic effects with other therapeutic modalities, which could revolutionize the management of chronic inflammatory and autoimmune disorders.

Vagus nerve stimulation with a small total charge transfer improves motor behavior and reduces neuroinflammation in a mouse model of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons in the substantia nigra (SN). Conventional treatments are ineffective in reversing disease progression. Recently, the therapeutic and rehabilitation potential of vagus nerve stimulation (VNS) in PD has been explored. However, the underlying mechanisms remain largely unknown. In this study, we investigated the neuroprotective effects of VNS in a lateral lesioned mice model of PD. Excluding controls, experimental mice received cuff electrode implantation on the left vagus nerve and 6-hydroxydopamine administration into the bilateral striatum. After ten days, electrical stimulation was delivered for 11 consecutive days onto PD animals. Behavioral tests were performed after stimulation. The expression of TH, Iba-1, GFAP, adrenergic receptors and cytokines in the SN and striatum was detected by immunofluorescence or western blotting. The activity of noradrenergic neurons in the locus coeruleus (LC) was also measured. Our results suggest that VNS improved behavioral performance in rod rotation, open field tests and pole-climbing tests in PD mice, accompanied by a decrease in the loss of dopaminergic neurons in the SN and increased TH expression in the striatum. Neuroinflammation-related factors, such as GFAP, Iba-1, TNF-α and IL-1β were also suppressed in PD mice after VNS compared to those without treatment. Furthermore, the proportion of c-Fos-positive noradrenergic neurons in the LC increased when animals received VNS. Additionally, the expression of the adrenergic receptor of α1BR was also upregulated after VNS compared to PD mice. In conclusion, VNS has potential as a novel PD therapy for neuroprotective effects, and indicate that activation of norepinephric neurons in LC may plays an important role in VNS treatment for PD.

Vagus nerve stimulation in Parkinson's disease: a scoping review of animal studies and human subjects research

Parkinson's Disease (PD) is a prevalent, progressive neurodegenerative disease with motor and non-motor symptoms. Vagus Nerve Stimulation (VNS) has emerged as a potential therapeutic approach for PD, but published research on this topic varies widely. This scoping review maps existing literature on VNS for PD, highlighting stimulation methods, operational parameters, safety profiles, neurophysiological mechanisms, and clinical outcomes in human and animal models. Online databases were used to identify 788 papers published between 2013 and 2023, from which 17 publications on invasive and non-invasive VNS in PD were selected. Studies showed high variability in VNS parameters and study design. Evidence in animal models and human subjects suggests potential neurophysiological effects on PD-related pathology and motor function improvements. However, significant gaps in the literature remain. Future research should include rigorous reporting of study design, standardization of stimulation parameters, and larger sample sizes to ultimately facilitate translation of VNS into clinical practice.

Immediate modulatory effects of transcutaneous vagus nerve stimulation on patients with Parkinson's disease: a crossover self-controlled fMRI study

Background

Previous studies have evaluated the safety and efficacy of transcutaneous auricular vagus nerve stimulation (taVNS) for the treatment of Parkinson's disease (PD). However, the mechanism underlying the effect of taVNS on PD remains to be elucidated. This study aimed to investigate the immediate effects of taVNS in PD patients.

Methods

This crossover self-controlled study included 50 PD patients. Each patient underwent three sessions of resting-state functional magnetic resonance imaging (rs-fMRI) under three conditions: real taVNS, sham taVNS, and no taVNS intervention. We analyzed whole-brain amplitude of low-frequency fluctuations (ALFF) from preprocessed fMRI data across different intervention conditions. ALFF values in altered brain regions were correlated with clinical symptoms in PD patients.

Results

Forty-seven participants completed the study and were included in the final analysis. Real taVNS was associated with a widespread decrease in ALFF in the right hemisphere, including the superior parietal lobule, precentral gyrus, postcentral gyrus, middle occipital gyrus, and cuneus (voxel p < 0.001, GRF corrected). The ALFF value in the right superior parietal lobule during real taVNS was negatively correlated with the Unified Parkinson's Disease Rating Scale Part III (r = -0.417, p = 0.004, Bonferroni corrected).

Conclusion

TaVNS could immediately modulate the functional activity of brain regions involved in superior parietal lobule, precentral gyrus, postcentral gyrus, middle occipital gyrus, and cuneus. These findings offer preliminary insights into the mechanism of taVNS in treating PD and bolster confidence in its long-term therapeutic potential. TaVNS appears to reduce ALFF values in specific brain regions, suggesting a potential modulation mechanism for treating PD.

The application of mesenchymal stem cells in the treatment of traumatic brain injury: Mechanisms, results, and problems

Mesenchymal stem cells (MSCs) are multipotent stromal cells that can be derived from a wide variety of human tissues and organs. They can differentiate into a variety of cell types, including osteoblasts, adipocytes, and chondrocytes, and thus show great potential in regenerative medicine. Traumatic brain injury (TBI) is an organic injury to brain tissue with a high rate of disability and death caused by an external impact or concussive force acting directly or indirectly on the head. The current treatment of TBI mainly includes symptomatic, pharmacological, and rehabilitation treatment. Although some efficacy has been achieved, the definitive recovery effect on neural tissue is still limited. Recent studies have shown that MSC therapies are more effective than traditional treatment strategies due to their strong multi-directional differentiation potential, self-renewal capacity, and low immunogenicity and homing properties, thus MSCs are considered to play an important role and are an ideal cell for the treatment of injurious diseases, including TBI. In this paper, we systematically reviewed the role and mechanisms of MSCs and MSC-derived exosomes in the treatment of TBI, thereby providing new insights into the clinical applications of MSCs and MSC-derived exosomes in the treatment of central nervous system disorders.

Cervical spinal cord stimulation exerts anti-epileptic effects in a rat model of epileptic seizure through the suppression of CCL2-mediated cascades

Epidural spinal cord stimulation (SCS) is indicated for the treatment of intractable pain and is widely used in clinical practice. In previous basic research, the therapeutic effects of SCS have been demonstrated for epileptic seizure. However, the mechanism has not yet been elucidated. In this study, we investigated the therapeutic effect of SCS and the influence of epileptic seizure. First, SCS in the cervical spine was performed. The rats were divided into four groups: control group and treatment groups with SCS conducted at 2, 50, and 300 Hz frequency. Two days later, convulsions were induced by the intraperitoneal administration of kainic acid, followed by video monitoring to assess seizures. We also evaluated glial cells in the hippocampus by fluorescent immunostaining, electroencephalogram measurements, and inflammatory cytokines such as C-C motif chemokine ligand 2 (CCL2) by quantitative real-time polymerase chain reaction. Seizure frequency and the number of glial cells were significantly lower in the 300 Hz group than in the control group. SCS at 300 Hz decreased gene expression level of CCL2, which induces monocyte migration. SCS has anti-seizure effects by inhibiting CCL2-mediated cascades. The suppression of CCL2 and glial cells may be associated with the suppression of epileptic seizure.

Relationship Between Short-chain Fatty Acids and Parkinson's Disease: A Review from Pathology to Clinic

Parkinson's disease (PD) is a complicated neurodegenerative disease, characterized by the accumulation of α-synuclein (α-syn) in Lewy bodies and neurites, and massive loss of midbrain dopamine neurons. Increasing evidence suggests that gut microbiota and microbial metabolites are involved in the development of PD. Among these, short-chain fatty acids (SCFAs), the most abundant microbial metabolites, have been proven to play a key role in brain-gut communication. In this review, we analyze the role of SCFAs in the pathology of PD from multiple dimensions and summarize the alterations of SCFAs in PD patients as well as their correlation with motor and non-motor symptoms. Future research should focus on further elucidating the role of SCFAs in neuroinflammation, as well as developing novel strategies employing SCFAs and their derivatives to treat PD.

The gut-brain axis in Parkinson's disease

There is a bi-directional communication between the gut, including the microbiota, and the brain through the autonomic nervous system. Accumulating evidence has suggested a bidirectional link between gastrointestinal inflammation and neurodegeneration, in accordance with the concept of the gut-rain axis. An abnormal microbiota-gut-brain interaction contributes to the pathogeny of Parkinson's disease. This supports the hypothesis that Parkinson's disease originates in the gut to spread to the central nervous system, in particular through the vagus nerve. Targeting the gut-to-brain axis with vagus nerve stimulation, fecal microbiota transplantation, gut-selective antibiotics, as well as drugs targeting the leaky gut might be of interest in the management of Parkinson's disease.

A review of combined neuromodulation and physical therapy interventions for enhanced neurorehabilitation

Rehabilitation approaches for individuals with neurologic conditions have increasingly shifted toward promoting neuroplasticity for enhanced recovery and restoration of function. This review focuses on exercise strategies and non-invasive neuromodulation techniques that target neuroplasticity, including transcranial magnetic stimulation (TMS), vagus nerve stimulation (VNS), and peripheral nerve stimulation (PNS). We have chosen to focus on non-invasive neuromodulation techniques due to their greater potential for integration into routine clinical practice. We explore and discuss the application of these interventional strategies in four neurological conditions that are frequently encountered in rehabilitation settings: Parkinson's Disease (PD), Traumatic Brain Injury (TBI), stroke, and Spinal Cord Injury (SCI). Additionally, we discuss the potential benefits of combining non-invasive neuromodulation with rehabilitation, which has shown promise in accelerating recovery. Our review identifies studies that demonstrate enhanced recovery through combined exercise and non-invasive neuromodulation in the selected patient populations. We primarily focus on the motor aspects of rehabilitation, but also briefly address non-motor impacts of these conditions. Additionally, we identify the gaps in current literature and barriers to implementation of combined approaches into clinical practice. We highlight areas needing further research and suggest avenues for future investigation, aiming to enhance the personalization of the unique neuroplastic responses associated with each condition. This review serves as a resource for rehabilitation professionals and researchers seeking a comprehensive understanding of neuroplastic exercise interventions and non-invasive neuromodulation techniques tailored for specific diseases and diagnoses.

Continuous vagus nerve stimulation exerts beneficial effects on rats with experimentally induced Parkinson's disease: Evidence suggesting involvement of a vagal afferent pathway

BACKGROUND

Vagus nerve stimulation (VNS) exerts neuroprotective and anti-inflammatory effects in preclinical models of central nervous system disorders, including Parkinson's disease (PD). VNS setting applied for experimental models is limited into single-time or intermittent short-duration stimulation. We developed a VNS device which could deliver continuous stimulation for rats. To date, the effects of vagal afferent- or efferent-selective stimulation on PD using continuous electrical stimulation remains to be determined.

OBJECTIVE

To investigate the effects of continuous and selective stimulation of vagal afferent or efferent fiber on Parkinsonian rats.

METHODS

Rats were divided into 5 group: intact VNS, afferent VNS (left VNS in the presence of left caudal vagotomy), efferent VNS (left VNS in the presence of left rostral vagotomy), sham, vagotomy. Rats underwent the implantation of cuff-electrode on left vagus nerve and 6-hydroxydopamine administration into the left striatum simultaneously. Electrical stimulation was delivered just after 6-OHDA administration and continued for 14 days. In afferent VNS and efferent VNS group, the vagus nerve was dissected at distal or proximal portion of cuff-electrode to imitate the selective stimulation of afferent or efferent vagal fiber respectively.

RESULTS

Intact VNS and afferent VNS reduced the behavioral impairments in cylinder test and methamphetamine-induced rotation test, which were accompanied by reduced inflammatory glial cells in substantia nigra with the increased density of the rate limiting enzyme in locus coeruleus. In contrast, efferent VNS did not exert any therapeutic effects.

CONCLUSION

Continuous VNS promoted neuroprotective and anti-inflammatory effect in experimental PD, highlighting the crucial role of the afferent vagal pathway in mediating these therapeutic outcomes.

Right vagus nerve stimulation improves motor behavior by exerting neuroprotective effects in Parkinson's disease rats

Background

Parkinson's disease (PD) is a common movement disorder disease. Left vagus nerve stimulation (LVNS) is a potential treatment option for PD. Compared with the left vagus nerve, the right vagus nerve is more closely connected with the midbrain dopaminergic neurons, which are the lesion locations of PD. However, whether right vagus nerve stimulation (RVNS) has a therapeutic effect on PD has not yet been studied. Therefore, in this study, we studied the therapeutic effect and underlying mechanism of RVNS using a PD rat model.

Methods

To establish the PD rat model, 8-week-old male Sprague-Dawley rats were intraperitoneally injected with rotenone for 21 days. The cuff electrodes were implanted into the right cervical vagal carotid sheaths of the rats. The right vagus nerve was continuously stimulated for 14 days using a radio stimulation system. Behavioral tests were performed before and after stimulation. Finally, tyrosine hydroxylase (TH), vesicular monoamine transporter 2 (VMAT2), and α-synuclein in the midbrain, including the substantia nigra (SN) and ventral tegmental area (VTA), were detected by immunofluorescence.

Results

A markedly lower distance traveled and rearing number was observed in the rotenone, rotenone + sham, and rotenone + RVNS groups compared to the vehicle group. After the stimulation days, the distance traveled and rearing number were both higher in the rotenone + RVNS group compared to the rotenone and rotenone + sham groups (P<0.01, P<0.0001). A remarkable increase in distance traveled and rearing number was observed in the rotenone + RVNS group after stimulation. TH expression in the vehicle group was significantly up-regulated than the other groups. RVNS markedly up-regulated TH expression level. A significantly higher expression of α-synuclein was observed in the rotenone, rotenone + sham, and rotenone + RVNS groups compared to the vehicle group. The expression of α-synuclein was lower in the rotenone + RVNS group compared to the rotenone and rotenone + sham groups. A markedly higher VMAT2 expression was observed in the vehicle group compared to other groups. RVNS significantly up-regulated VMAT2 expression.

Conclusions

The improved motor behavior and neuroprotective effects on the midbrain dopaminergic neurons in the PD rat model suggest that RVNS could be used as a potential treatment for PD.

Fascicles split or merge every ∼560 microns within the human cervical vagus nerve

Objective.Vagus nerve stimulation (VNS) is Food and Drug Administration-approved for epilepsy, depression, and obesity, and stroke rehabilitation; however, the morphological anatomy of the vagus nerve targeted by stimulatation is poorly understood. Here, we used microCT to quantify the fascicular structure and neuroanatomy of human cervical vagus nerves (cVNs).Approach.We collected eight mid-cVN specimens from five fixed cadavers (three left nerves, five right nerves). Analysis focused on the 'surgical window': 5 cm of length, centered around the VNS implant location. Tissue was stained with osmium tetroxide, embedded in paraffin, and imaged on a microCT scanner. We visualized and quantified the merging and splitting of fascicles, and report a morphometric analysis of fascicles: count, diameter, and area.Main results.In our sample of human cVNs, a fascicle split or merge event was observed every ∼560µm (17.8 ± 6.1 events cm-1). Mean morphological outcomes included: fascicle count (6.6 ± 2.8 fascicles; range 1-15), fascicle diameter (514 ± 142µm; range 147-1360µm), and total cross-sectional fascicular area (1.32 ± 0.41 mm2; range 0.58-2.27 mm).Significance.The high degree of fascicular splitting and merging, along with wide range in key fascicular morphological parameters across humans may help to explain the clinical heterogeneity in patient responses to VNS. These data will enable modeling and experimental efforts to determine the clinical effect size of such variation. These data will also enable efforts to design improved VNS electrodes.

The role of the locus coeruleus/norepinephrine system in the pathogenesis of neurodegenerative disorders: An update

PURPOSE OF REVIEW

The aim of this review was to provide an update on current and emerging knowledge of the neuropathological processes affecting the locus coeruleus/norepinephrine (LC/NE) system, their effect on Alzheimer's disease and Parkinson's disease symptomatology, including efforts to translate these notions into therapeutic actions targeting the noradrenergic system.

RECENT FINDINGS

Over the past 2 years, work from multiple groups has contributed to support an early role of locus coeruleus degeneration and/or hyperactivation in the neurodegenerative process, including a trigger of neuroinflammation. Imaging advances are allowing the quantification of locus coeruleus structural features in vivo, which is critical in the early stages of disease. Nonmotor and noncognitive symptoms, often secondary to the involvement of the LC/NE system, are becoming more important in the definition of these diseases and their treatment.

SUMMARY

The diverse symptomatology of Parkinson's disease and Alzheimer's disease, which is not limited to cardinal motor and cognitive abnormalities, strongly suggests a multisystem neurodegenerative process. In this context, it is increasingly clear how the LC/NE system plays a key role in the initiation and maintenance of the neurodegenerative process.

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.

Role of the Cholinergic Anti-Inflammatory Reflex in Central Nervous System Diseases

In several central nervous system diseases, it has been reported that inflammation may be related to the etiologic process, therefore, therapeutic strategies are being implemented to control inflammation. As the nervous system and the immune system maintain close bidirectional communication in physiological and pathological conditions, the modulation of inflammation through the cholinergic anti-inflammatory reflex has been proposed. In this review, we summarized the evidence supporting chemical stimulation with cholinergic agonists and vagus nerve stimulation as therapeutic strategies in the treatment of various central nervous system pathologies, and their effect on inflammation.

The Cholinergic Anti-Inflammatory Pathway Attenuates the Development of Atherosclerosis in Apoe-/- Mice through Modulating Macrophage Functions

(1) Background: The cholinergic anti-inflammatory pathway (CAP) has been implicated in the regulation of various diseases, including chronic inflammatory cardiovascular disorders such as atherosclerosis (AS). This study aims to explore the underlying regulatory mechanisms of CAP activity in the progression of AS. (2) Methods: The Apoe^-/- mice were subjected to sham, bilateral cervical vagotomy surgery (VGX), and VGX supplemented with Gainesville Tokushima scientists (GTS)-21 (4 mg/kg/d) and then fed with a high-fat diet for 10 weeks. Atherosclerotic lesion size and inflammation levels were investigated by histology and inflammatory cytokines analysis. The blood M1/M2 macrophages were analyzed by flow cytometry. Primary mouse bone marrow-derived macrophages (BMDM), peritoneal macrophages, and RAW264.7 cells were treated with CAP agonists acetylcholine (Ach) and GTS-21 to study their effects on macrophage functions. (3) Results: Compared with the sham group, inhibition of CAP by the VGX resulted in growing aortic lipid plaque area, deteriorated inflammatory levels, and aberrant quantity of M1/M2 macrophages in Apoe^-/- mice. However, these detrimental effects of VGX were significantly ameliorated by the reactivation of CAP through GTS-21 treatment. The in vitro study using macrophages revealed that stimulation with CAP agonists suppressed M1, but promoted M2 macrophage polarization through the upregulation of TNFAIP3 and phosphorylation STAT3 levels, respectively. Moreover, the activation of CAP inhibited the formation of macrophage foam cells in the peritoneal cavity by regulating genes related to cholesterol metabolism. (4) Conclusions: This study provides novel evidence and mechanisms that the CAP plays an important role in the regulation of AS development by controlling macrophage functions, implying a potential use of CAP activation as a therapeutic strategy for AS treatment.

Noninvasive vagus nerve stimulation in Parkinson's disease: current status and future prospects

INTRODUCTION

Parkinson's disease (PD) is a common progressive neurodegenerative disorder with multifactorial etiology. While dopaminergic medication is the standard therapy in PD, it provides limited symptomatic treatment and non-pharmacological interventions are currently being trialed.

AREAS COVERED

Recent pathophysiological theories of Parkinson's suggest that aggregated α-synuclein form in the gut and spread to nuclei in the brainstem via autonomic connections. In this paper, we review the novel hypothesis that noninvasive vagus nerve stimulation (nVNS), targeting efferent and afferent vagal projections, is a promising therapeutic tool to improve gait and cognitive control and ameliorate non-motor symptoms in people with Parkinson's. We conducted an unstructured search of the literature for any studies employing nVNS in PD as well as for studies examining the efficacy of nVNS on improving cognitive function and where nVNS has been applied to co-occurring conditions in PD.

EXPERT OPINION

Evidence of nVNS as a novel therapeutic to improve gait in PD is preliminary, but early signs indicate the possibility that nVNS may be useful to target dopa-resistant gait characteristics in early PD. The evidence for nVNS as a therapeutic tool is, however, limited and further studies are needed in both brain health and disease.