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Given its non-invasive nature, there is increasing interest in the use of transcutaneous vagus nerve stimulation (tVNS) across basic, translational and clinical research. Contemporaneously, tVNS can be achieved by stimulating either the auricular branch or the cervical bundle of the vagus nerve, referred to as transcutaneous auricular vagus nerve stimulation(VNS) and transcutaneous cervical VNS, respectively. In order to advance the field in a systematic manner, studies using these technologies need to adequately report sufficient methodological detail to enable comparison of results between studies, replication of studies, as well as enhancing study participant safety. We systematically reviewed the existing tVNS literature to evaluate current reporting practices. Based on this review, and consensus among participating authors, we propose a set of minimal reporting items to guide future tVNS studies. The suggested items address specific technical aspects of the device and stimulation parameters. We also cover general recommendations including inclusion and exclusion criteria for participants, outcome parameters and the detailed reporting of side effects. Furthermore, we review strategies used to identify the optimal stimulation parameters for a given research setting and summarize ongoing developments in animal research with potential implications for the application of tVNS in humans. Finally, we discuss the potential of tVNS in future research as well as the associated challenges across several disciplines in research and clinical practice.

Background: Melatonin (MLT) and its receptor deficiency have been shown to be associated with type 2 diabetes mellitus (T2DM). Transcutaneous auricular vagus nerve stimulation (taVNS) is a non-invasive alternative intervention for patients suffering from hyperglycemia. Here, we aimed to investigate the role of taVNS on blood glucose modulation via intestinal melatonin receptors (MRs) and MLT secretion in hyperglycemia. Methods: Adult male Zucker diabetes fatty (ZDF) rats and Zucker lean (ZL) littermates were used. Forty ZDF rats were randomized into ZDF, taVNS, Px + taVNS and Lu + Px + taVNS groups (Px: pinealectomy, Lu: Luzindole). ZL rats served as a control group for comparison with ZDF rats without involvement in the taVNS intervention. Thirty min-taVNS interventions (2/15 Hz, 2 mA, 30 min/days) were administered once daily under anesthesia for 3 consecutive weeks in taVNS, Px + taVNS and Lu + Px + taVNS groups. Body weight and fasting blood glucose (FBG) were measured weekly in all rats, and real-time blood glucose was tested in the ZL and ZDF groups before, during and after the taVNS intervention. Plasma MLT concentration and the expression of MRs in the duodenum, jejunum and ileum were measured by the end of experiments. Results: Compared with the ZL group, the level of FBG and body weight increased (all p < 0.01), plasma MLT secretion and the expression of MRs in duodenum, jejunum and ileum of ZDF rats decreased obviously (all p < 0.05), respectively. TaVNS can significantly reverse the hyperglycemia by regulating the non-pineal-derived MLT and MRs system in Px + taVNS group. Compared with the ZDF group, the expression of different intestinal MRs in the taVNS group was increased and more compactly arranged (both p < 0.05), the level of plasma MLT secretion was up-regulated (p < 0.01), and FBG and body weight were decreased (both p < 0.01). Meanwhile, after taVNS intervention in rats in the Px + taVNS group, we observed an increase in MLT secretion and the number of intestinal MRs compared with the taVNS group (all p > 0.05). In contrast, ZDF rats in which the pineal gland was excised by taVNS intervention and injected with the MRs antagonist Luzindole did not show these changes. Conclusion: The glucose reduction effect of taVNS may be related to regulating MLT levels and expressing intestinal MRs. [ABSTRACT FROM AUTHOR]

Background: Depression is a common psychiatric disorder in diabetic patients. Depressive mood associated with obesity/metabolic disorders is related to the inflammatory response caused by long‐term consumption of high‐fat diets, but its molecular mechanism is unclear. In this study, we investigated whether the antidepressant effect of transcutaneous auricular vagus nerve stimulation (taVNS) in high‐fat diet rats works through the P2X7R/NLRP3/IL‐1β pathway. Methods: We first used 16S rRNA gene sequencing analysis and LC–MS metabolomics assays in Zucker diabetic fatty (ZDF) rats with long‐term high‐fat diet (Purina #5008) induced significant depression‐like behaviors. Next, the forced swimming test (FST) and open field test (OFT) were measured to evaluate the antidepressive effect of taVNS. Immunofluorescence and western blotting (WB) were used to measure the microglia state and the expression of P2X7R, NLRP3, and IL‐1β in PFC. Results: Purina#5008 diet induced significant depression‐like behaviors in ZDF rats and was closely related to purine and inflammatory metabolites. Consecutive taVNS increased plasma insulin concentration, reduced glycated hemoglobin and glucagon content in ZDF rats, significantly improved the depressive‐like phenotype in ZDF rats through reducing the microglia activity, and increased the expression of P2X7R, NLRP3, and IL‐1β in the prefrontal cortex (PFC). Conclusion: The P2X7R/NLRP3/IL‐1β signaling pathway may play an important role in the antidepressant‐like behavior of taVNS, which provides a promising mechanism for taVNS clinical treatment of diabetes combined with depression. [ABSTRACT FROM AUTHOR]

Background: Transcutaneous auricular vagus nerve stimulation (taVNS) is a crucial neuromodulation therapy for depression, yet its molecular mechanism remains unclear. Here, we aim to unveil the underlying mechanisms of antidepression by systematically evaluating the change of gene expression in different brain regions (i.e., hippocampus, anterior cingulate cortex, and medial prefrontal cortex). Methods: The adolescent depression rat model was established by chronic unpredictable mild stress (CUMS), followed by the taVNS treatment for 3 weeks. The open field test (OFT), forced swimming test (FST), elevated plus maze test (EPM), and new object recognition (NOR) test were used to evaluate depressive‐ and anxiety‐like behaviors. Gene expression analysis of three brain regions was conducted by RNA sequencing (RNA‐seq) and further bioinformatics methods. Results: The depressive‐ and anxiety‐like behaviors in CUMS‐exposed rats were manifested by decreased spontaneous locomotor activity of OFT, increased immobility time of FST, increased entries and time in the closed arms of EPM, and decreased new object index of NOR. Furthermore, CUMS exposure also led to alterations in gene expression within the hippocampus (HIP), anterior cingulate cortex (ACC), and medial prefrontal cortex (mPFC), suggesting a potential link between adolescent stress and pathological changes within these brain regions. TaVNS could significantly ameliorate depressive‐ and anxiety‐like behaviors. Its effects on these three brain regions were found related to regulation of the metabolism, and there were some brain region‐specific findings. Compared with ACC and mPFC, taVNS has a more concrete effect on HIP by regulating the inflammation response and glycolysis. Conclusion: taVNS is capable of ameliorating adolescent depressive‐ and anxiety‐like behaviors by regulating plenty of genes in the three brain regions. Suppressed level of inflammatory response and enhanced glycolysis manifests the dominant role of taVNS in HIP, which provides a theoretical foundation and data support for the molecular mechanism of antidepression by taVNS. [ABSTRACT FROM AUTHOR]

Background: Transcutaneous auricular vagus nerve stimulation (taVNS) is a vital neuromodulation for the treatment of depression, but its antidepressant molecular mechanism is unclear. The α7 nicotinic acetylcholine receptor (α7nAchR) is a key mediator of the vagus nerve that mediates its anti‐inflammatory efficacy. Here, we investigated whether the antidepressant effect of taVNS in chronic unpredicted mild stress (CUMS)‐exposed rats works through the α7nAchR/JAK2/STAT3/NF‐κB pathway. Methods: The depression model was established by CUMS for continuous 6 weeks in rats. From the 4th week of the experiment, CUMS‐exposed rats were subjected to taVNS for 3 weeks. To clarify the role of α7nAchR in the antidepressant effect of taVNS, we used α7nAchR−/− gene knockout rats. The sucrose preference test (SPT), open field test (OFT), and forced swimming test (FST) were used to evaluate depression‐like behaviors of rats. Immunofluorescent staining was used to observe the morphology of microglia in the hypothalamus. Western blot was used to examine the protein expression of α7nAchR, p‐JAK2, p‐STAT3, IL‐1β, NF‐κB p65, and p‐NF‐κB p65 in the hypothalamus. Results: Depression‐like behaviors in CUMS‐exposed rats were manifested by decreased SPT ratio, increased FST immobility time, decreased total distance, vertical movement score, and activity time of OFT. Hypothalamic neuroinflammation in CUMS‐exposed rats was manifested by an amoebic‐like activated state of microglia, downregulated expression of α7nAchR, p‐JAK2, p‐STAT3, and upregulated expression of NF‐κB p65, p‐NF‐κB p65, and IL‐1β. TaVNS could significantly reverse the above‐mentioned phenomena, but had a poor improvement effect for CUMS‐exposed α7nAchR−/− rats. Conclusion: The hypothalamic α7nAchR/JAK2/STAT3/NF‐κB signaling pathway may play an important role in the antidepressant‐like behavior of taVNS. [ABSTRACT FROM AUTHOR]

There are 9.9 million new cases of dementia in the world every year. Short-term conversion rate from mild cognitive impairment (MCI) to dementia is between 20% and 40%, but long-term in 5–10 years ranges from 60% to 100%. It is particularly important to prevent or prolong the development of MCI into dementia. Both auriculotherapy and vagus nerve stimulation are effective on improving cognitive functions. However, there is no double blinded randomized clinical trial to support the effectiveness of transcutaneous electrical stimulation of auricular acupoints in patients with MCI. This randomized controlled trial involved patients with MCI, aged from 55 to 75 years old. Patients were randomly allocated to transcutaneous auricular vagus nerve stimulation (taVNS) group or sham taVNS group. In the taVNS group, two auricular acupoints were stimulated, including heart (concha, CO 15) and kidney (CO 10), which are in the distribution of vagus nerve. While in the sham taVNS group, two other auricular acupoints were stimulated, including elbow (scaphoid fossa, SF 3) and shoulder (SF 4,5), which are out of the distribution of vagus nerve. The primary outcome was the Montreal cognitive assessment-basic, MOCA-B. The secondary outcomes included auditory verbal learning test-HuaShan version (AVLT-H), shape trails test A&B (STT-A&B), animal fluence test (AFT), Boston naming test (BNT), Pittsburgh sleep quality index (PSQI), rapid eye movement sleep behavior disorder screening questionnaire (RBDSQ), Epworth sleepiness scale (ESS) and functional activities questionnaire (FAQ). These outcome measures were taken at baseline, 24 weeks later. After 24 weeks of intervention, the data of 52 patients were intended for analysis. After intervention, there was significant difference in the overall scores of MoCA-B between taVNS group and sham taVNS group (p = 0.033 < 0.05). In taVNS group, compared with before intervention, the overall scores of MOCA-B increased significantly after intervention (p < 0.001). As for N5 and N7, the two sub-indicators of AVLT-H, in taVNS group, compared with before intervention, both N5 and N7 increased significantly after intervention (both ps < 0.001). As for STTB, in taVNS group, compared with before intervention, STTB was significantly reduced after intervention (p = 0.016). For BNT, in taVNS group, compared with before intervention, BNT increased significantly after intervention (p < 0.001). In taVNS group, compared with before intervention, PSQI, RBDSQ, ESS and FAQ decreased significantly after intervention (p = 0.002, 0.025, <0.001, 0.006 respectively). 1 patient with a history of tympanic membrane perforation in taVNS group was reported with mild adverse reactions which disappeared a week after termination of taVNS. The intervention of taVNS is effective on increasing the overall scores of MoCA-B, N5 and N7. The clinical trial demonstrated that taVNS can improve cognitive performance in patients with MCI. This inexpensive, effective and innovative method can be recommended as a therapy for more patients with MCI in the prevention or prolonging of its development into dementia, but it is still required to be further investigated. http://www.chictr.org.cn. (ID: ChiCTR2000038868) • It is particularly important to prevent or prolong its development of mild cognitive impairment (MCI) into Alzheimer's Disease (AD). • It is the first randomized controlled trial worldwide for taVNS to manage MCI. • Both vagus nerve stimulation and auriculotherapy are effective in improving cognitive functions. • It demonstrates that taVNS can improve cognitive performance in patients with MCI. [ABSTRACT FROM AUTHOR]

In order to improve taVNS efficacy, the usage of fMRI to explore the predictive neuroimaging markers would be beneficial for screening the appropriate MDD population before treatment. A total of 86 MDD patients were recruited in this study, and all subjects were conducted with the clinical scales and resting-state functional magnetic resonance imaging (fMRI) scan before and after 8 weeks' taVNS treatment. A two-stage feature selection strategy combining Machine Learning and Statistical was used to screen out the critical brain functional connections (FC) that were significantly associated with efficacy prediction, then the efficacy prediction model was constructed for taVNS treating MDD. Finally, the model was validated by separated the responding and non-responding patients. This study showed that taVNS produced promising clinical efficacy in the treatment of mild and moderate MDD. Eleven FCs were selected out and were found to be associated with the cortico-striatal-pallidum-thalamic loop, the hippocampus and cerebellum and the HAMD-17 scores. The prediction model was created based on these FCs for the efficacy prediction of taVNS treatment. The R-square of the conducted regression model for predicting HAMD-17 reduction rate is 0.44, and the AUC for classifying the responding and non-responding patients is 0.856. The study demonstrates the validity and feasibility of combining neuroimaging and machine learning techniques to predict the efficacy of taVNS on MDD, and provides an effective solution for personalized and precise treatment for MDD. • Observating the neuroimaging markers in the treatment of MDD with taVNS. • Observing the correlation of meaningful brain functional features with clinical symptoms. [ABSTRACT FROM AUTHOR]

As an emerging neuromodulation therapy, transcutaneous auricular vagus nerve stimulation (taVNS) has been proven to be safe and effective for epilepsy, major depressive disorders, insomnia, glucose metabolic disorders, pain, stroke, post stroke rehabilitation, anxiety, fear, cognitive impairment, cardiovascular disorders, tinnitus, Prader-Willi Syndrome, and COVID-19. Although the history of taVNS is only two decades, the devices carrying taVNS technique have been constantly updated. Especially in recent years, the development of taVNS devices has presented a new trend. To conclude, the development of taVNS devices has entered a new era, thus the update speed and quality of taVNS devices will be considerably improved in the future. This article reviewed the history and classification of taVNS devices. The correlation between the effectiveness and stimulation parameters from taVNS devices still remains unclear. There is a lack of standard or harmonization among different taVNS devices. Strategies, including further comparative research and establishment of standard, have been recommended in this article to promote the future development of taVNS devices. [ABSTRACT FROM AUTHOR]

Primary insomnia (PI) is associated with increased spontaneous neuronal activity. Transcutaneous auricular vagus nerve stimulation (taVNS) modulates brain function, and it is an effective treatment for primary insomnia. However, whether taVNS alleviates insomnia through modulating spontaneous neuronal activity is not fully clarified. This study aims to investigate the instant effect of taVNS in modulating spontaneous neuronal activity in PI patients using resting-state functional magnetic resonance imaging (rs-fMRI). Twenty-two PI subjects underwent rs-fMRI scanning prior and immediately after 30 min treatment of taVNS controlled by twenty healthy adults. Amplitude of low frequency fluctuations (ALFF) analysis was employed to assess the difference in spontaneous neuronal activity between PI patients and healthy adults, as well as between pre-treatment and post-treatment of taVNS. The taVNS-induced altered ALFF brain areas were then selected as regions of interest to perform the resting state functional connectivity (RSFC) analysis in PI patients. The right precuneus showed significantly increased ALFF in PI patients. After immediate taVNS treatment, the ALFF was significantly decreased in the right precuneus and increased in the left middle occipital gyrus. The RSFC in right precuneus with right angular, right superior frontal gyrus, and right middle frontal gyrus was significantly decreased. This study provides insights into the instant brain effects of taVNS on PI patients. [ABSTRACT FROM AUTHOR]

Depression is a highly prevalent disorder, and its treatment is far from satisfactory. There is an urgent need to develop a new treatment for depression. Although still at its early stage, transcutaneous auricular vagus nerve stimulation (taVNS) has shown promising potential for treating depression. In this article, we first summarize the results of clinical studies on the treatment effect of taVNS on depression. Then, we re-analyze a previous study to identify the specific symptoms taVNS can relieve as indicated by subscores of the 24-item Hamilton Depression Scale in patients with depression. We found that taVNS can significantly reduce multiple symptoms of depression patients, including anxiety, psychomotor retardation, sleep disturbance, and hopelessness. Next, we pose several hypotheses on the mechanism of taVNS treatment of depression, including directly and indirectly modulating the activity and connectivity of key brain regions involved in depression and mood regulation; inhibiting neuro-inflammatory sensitization; modulating hippocampal neurogenesis; and regulating the microbiome-brain-gut axis. Finally, we outline current challenges and lay out the future directions of taVNS treatment of depression, which include (1) intensively comparing stimulation parameters and "dose effect" (treatment frequency and duration) to maximize the treatment effect of taVNS; (2) exploring the effect of taVNS on disorders comorbid with depression (such as chronic pain disorders, cardiovascular disorder, and autism) to provide new "two-for-one" treatment approaches for patients with these disorders; and (3) applying multiple scale methods to explore the underlying mechanism of taVNS. [ABSTRACT FROM AUTHOR]

Background: Depression presents a significant burden to both patients and society. One treatment that has emerged is vagus nerve stimulation (VNS), an FDA-approved physical treatment for depressive disorders. However, the application of this intervention has been limited by the involvement of surgery and potential side effects. The aim of this study is to explore the effectiveness of stimulating the superficial branches of the vagus nerve as a solo treatment for MDD.Methods: This is a nonrandomized, controlled study. The first cohort of patients (n=91) only received transcutaneous auricular VNS (taVNS) for 12 weeks. In the second cohort (n=69), patients first received 4 weeks of sham taVNS followed by 8 weeks of taVNS. All treatments were self-administered by the patients at home after they received training from the hospitals. The primary outcome measurement was the 24-item Hamilton Depression Rating Scale measured at weeks 0, 4, 8, and 12. Data analysis included a timelag analysis comparing (1) real and sham taVNS groups at week 4; (2) the real taVNS group at week 4 vs the sham taVNS group at week 8 (fourth week of real taVNS following 4 weeks of sham); and (3) the real taVNS group at week 8 vs the sham taVNS group at week 12 (eighth week of real taVNS following sham).Results: After four weeks of treatment, MDD patients in the taVNS group showed greater improvement than patients in the sham taVNS group as indicated by Hamilton score changes as well as response and remission rates at week four. In addition, we also found that the clinical improvements continued until week 12 during taVNS.Limitations: Patients were not randomized in this study.Conclusions: Our results suggest that taVNS is a promising, safe, and cost-effective therapeutic method for mild and moderate MDD. [ABSTRACT FROM AUTHOR]

Previous studies have found that transcutaneous auricular vagus nerve stimulation (taVNS) is clinically effective in the treatment of major depressive disorder (MDD), and its efficacy mechanism is related to modulation of the default mode network (DMN) and cognitive control network (CCN). However, the mechanism of the immediate effect of taVNS for MDD remains to be elucidated. A total of 58 patients with MDD and 54 healthy controls(HCs) were included in this study. The MDD group was treated with taVNS for 30 min (20 Hz, 4-6 mA) immediately, and we observed amplitude of low-frequency fluctuations (ALFF) abnormalities in the MDD group and changes in ALFF and functional connectivity (FC) before and after immediate treatment. The ALFF brain regions altered by taVNS induction were used as regions of interest to analyze whole-brain FC changes in the MDD group. After taVNS treatment, ALFF in the right precuneus was decreased in the MDD group. The FC of the right precuneus with the left middle frontal gyrus, the left posterior cingulate gyrus and the left angular gyrus were decreased in the MDD group. Correlation analysis showed that the FC values between the right precuneus and the left posterior cingulate gyrus in the pre-treatment MDD group was negatively correlated with the 17-item Hamilton depression rating scale scores. TaVNS has an immediate modulatory effect on DMN and CCN. It would be proposed that these functional networks may be effective targets for the long-term treatment of MDD patients with taVNS. [ABSTRACT FROM AUTHOR]

Abstract: Objective: We investigated the safety and efficacy of transcutaneous auricular vagus nerve stimulation (ta-VNS) for the treatment of pediatric epilepsy. Methods: Fourteen pediatric patients with intractable epilepsy were treated by ta-VNS of the bilateral auricular concha using an ear vagus nerve stimulator. The baseline seizure frequency was compared with that after 8weeks, from week 9 to 16 and from week 17 to the end of week 24, according to the seizure diaries of the patients. Results: One patient dropped out after 8weeks of treatment due to lack of efficacy, while the remaining 13 patients completed the 24-week study without any change in medication regimen. The mean reduction in seizure frequency relative to baseline was 31.83% after week 8, 54.13% from week 9 to 16 and 54.21% from week 17 to the end of week 24. The responder rate was 28.57% after 8weeks, 53.85% from week 9 to 16 and 53.85% from week 17 to the end of week 24. No severe adverse events were reported during treatment. Conclusion: Transcutaneous auricular VNS may be a complementary treatment option for reducing seizure frequency in pediatric patients with intractable epilepsy and should be further studied. [Copyright &y& Elsevier]