Clinical Observation Of Percutaneous Auricular Vagus Nerve Stimulation For Migraine And FMRI Brain Imaging Study Of Its Mechanism

Objective1.A randomized cross-over trial was designed to investigated the short-term effect of transcranial auricular vagus nerve stimulation(taVNS)on the migraine patients.Based on functional magnetic resonance imaging(fMRI)data analysis,we aimed to explore the changes in the blood-oxygen-level-dependent(BOLD)signal of migraine patients during the taVNS intervention.We also aimed to analyzed the functional connectivity(FC)change of the three important brainstem nuclei(nucleus tractus solitarius,locus coeruleus,and raphe nucleus)with the whole brain before and after the short-term taVNS in migraine patients.2.A randomized controlled trial was conducted to investigate the clinical efficacy of transcranial auricular vagus nerve stimulation(taVNS)in the treatment of migraine.Similarly,we aimed to understand the the effect of longitudinal taVNS on the functional connectivity change of the three brain stem nuclei(nucleus tractus solitarius,NTS;locus coeruleus,LC and raphe nucleus,RN)with the whole brain before and after intervention.3.Based on the fMRI data acquired from the longitudinal trial,we aimed to explore the responsive imaging biomarkers of migraine patients treated with taVNS.By functionally segmenting the thalamus into 6 subregions,we analyzed functional connectivity of the 6 thalamic subregions with the whole brain and explore their correlation with the migraine attack changes.MethodsStudy 1:This study is a randomized cross-over controlled trial.29 migraine patients were randomly included in the real taVNS and sham taVNS groups,and received two interventions respectively(first real taVNS followed by sham taVNS or first sham taVNS followed by real taVNS),with an intermediate interval washout-period of at least one week.The fMRI scans before,during and after the intervention of each short-term stimulation were collected respectively,and the fMRI image acquisition during the intervention process adopts the method of block design.Finally,the whole brain analysis of fMRI during the stimulation intervention process is carried out to explore the changes of fMRI BOLD signal caused by real and sham stimulation during the intervention process.The brain stem nuclei(nucleus tractus solitarius,locus coeruleus,and raphe nucleus)closely related to the afferent center of the vagus nerve were selected as the Region of Interest(ROI)to perform the seed-based functional connectivity analysis before and after the short-term taVNS stimulation intervention.We also compared the functional connectivity change between real and sham taVNS after the short-term intervention.Study 2:This is a parallel randomized controlled clinical trial.Seventy eligible subjects were recruited and randomized into two groups,35 patients were included in the real stimulation group and 35 patients in the sham stimulation group.The treatment lasted for 4 weeks and 3 sessions per week,and the real or sham taVNS was continuously applied for 30 minutes during each session.The clinically relevant scales of migraine patients were collected before and after intervention to evaluate the clinical improvement of real and sham taVNS before and after treatment.The patients' fMRI data were also collected before and after the 4-week longitidinal intervention.The brain stem nucleus(nucleus tractus solitarius,locus coeruleus,raphe nucleus)were used to analyze the functional connectivity changes with the whole-brain before and after the treatment in migraine patients.Study 3:Based on the fMRI data acquired from the study 2,we also explored the functional connectivity change of the thalamic subregions before and after intervention in migraine patients.Thalamus was functionally parceled into 6 subregions and used as ROIs to analyzed the seed-based functional connectivity in migraine patients,Pearson's correlation were further used to explore the connection between the functional connectivity change and the migraine attack change.Results1.In study 1,29 migraine patients were recruited and randomized into short-term real or sham taVNS,and 26 patients completed all trials in total.The one-sample T test results of the whole brain showed that the short-term real taVNS intervention significantly activated the bilateral putamen,caudate nucleus,the right globus pallidus and the ventral thalamus;significantly inhibited the bilateral central posterior and central anterior gyrus,anterior cingulate gyrus,medial prefrontal cortex,precuneus,hippocampus,amygdala,fusiform gyrus,lingual gyrus,these are brain regions involved in default mode networks and limbic system.Brainstem nuclei were also found to be deactivated,regions included nucleus tractus solitarius,locus coeruleus,and raphe nucleus.Compared to the sham taVNS,the results showed that the real stimulation intervention deactivated the nucleus tractus solitarius,bilateral locus coeruleus,and raphe nucleus,and real stimulation has no significant activation of the brainstem area.2.The results of the functional connectivity of the seed-based analyses showed that short-term taVNS stimulation increased the FC of NTS with bilateral cerebellum,angular gyrus,middle/upper temporal gyrus,left superior temporal gyrus,superior/middle occipital gyrus,amygdala,hippocampus,putamen,right angular gyrus,inferior occipital gyrus,and middle occipital gyrus and reduced FC with left frontal and parietal lobe,precentral gyrus and right parietal operculum/SMG.Increased FC of LC with bilateral precuneus was found,and decreased FC of LC with bilateral PreCG/PoCG,right parietal operculum/central operculum/superior temporal gyrus/posterior insula and lingual gyrus was detected.We also found increased FC of RN with bilateral putamen,left pallidum,cerebellum and decreased FC of RN with bilateral precuneus/PCC.3.Compared to sham taVNS,real taVNS showed increase FC of NTS with bilateral fusiform gyrus/lingual gyrus,left hippocampus and superior parietal gyrus;decreased FC of NTS with left dlPFC/superior frontal gyrus.Increased FC of LC was found with bilateral precuneus,right inferior occipital gyrus,and decreased FC with bilateral PAG,ACC/mPFC,supplementary motor area/middle cingulate gyrus/paracentral gyrus,left PoCG,right operculum/posterior insula.Real taVNS also showed increased FC of RN with bilateral putamen and left thalamus(ventral);there is no significant decreased FC of RN was found.4.In study 2,after screening and baseline assessment,seventy patients were randomized in taVNS and sham taVNS groups(35 in the taVNS group,35 in the sham taVNS group).Fifty-nine patients(33 in the taVNS group,26 in the sham taVNS group)completed the two fMRI scans(baseline and after 4-week treatment)and included in the final fMRI analysis.Clinical results showed that after four weeks of chronic intervention with taVNS can significantly reduce the number of migraine attack days(the primary clinical outcome),the pain intensity measured by VAS and the migraine attack times in migraine patients.5.Compared to sham group,the real taVNS group showed:1)decreased NTS functional connectivity with the bilateral medial prefrontal cortex(mPFC)and bilateral hippocampus(HPC);and increased functional connectivity with the bilateral raphe nuclei after treatment;2)decreased LC functional connectivity with the bilateral postcentral gyrus(PoCG),superior parietal gyrus(SPG),left precentral gyrus(PreCG);and increased functional connectivity with the bilateral thalamus after treatment;3)decreased RN functional connectivity with the bilateral thalamus and right PoCG;increased functional connectivity with the bilateral mPFC,left occipital frontal cortex(OFC),left angular gyrus(AG),right caudate and putamen after treatment.More importantly.Pearson's correlation analysis showed that the number changes of migraine attack days before and after intervention in the real taVNS group was significantly positively correlated with changes in the functional connectivity between the bilateral raphe nucleus and the right putamen(r=0.55,p<0.001).6.Combing the seed-based FC results of the short-term taVNS and longitudinal taVNS intervention,we found that both short-term taVNS intervention and chronic taVNS intervention can modulate FC of NTS-hippocampus,LC-postcentral gyrus,and RN-putamen.And it is consistent in reducing the functional connection between the locus coeruleus and the central posterior gyrus and enhancing the functional connection between the raphe nucleus and the putamen.7.Compared to the sham group,the real taVNS group showed increased connections between "motor" thalamic seed with the rostral anterior cingulate cortex/medial prefrontal cortex(rACC/mPFC)after treatment.Also,real taVNS,compared to sham taVNS,showed decreased connectivity between 1)the "parietal" thalamic seed and the right supramarginal gyrus(SMG);2)the "temporal" thalamic seed and the right superior parietal gyrus(SPG);3)the "occipital" thalamic seed and the bilateral postcentral gyrus(PoG),right SMG,and right precuneus(PCu)/SPL.Pearson's correlation showed that the FC change of the "occipital"thalamic seed and the bilateral PoG is significantly correlated with the reduction of the migraine days in the real taVNS group after treatment.ConclusionsThis current study explored the central brain responsive mechanism of migraine patients under short-term and chronic taVNS intervention based on the fMRI analysis.The results of the study showed that during short-term taVNS stimulation,real taVNS significantly deactivated the brain regions involved in the default mode network,limbic system,and the brain stem nuclei closely related to the central afferent pathway of the vagus nerve,including the nucleus tractus solitarius,locus coeruleus and raphe nucleus.Meanwhile,compared with the sham stimulation,the real taVNS intervention has a significant deactivated effect on the brainstem nuclei including NTS,LC and RN,suggesting that the brainstem nucleus may be closely related to the regulation of the central nervous system by taVNS in migraine patients.Furthermore,based on the resting state fMRI analysis,we found that short-term taVNS and chronic taVNS may play a central regulatory mechanism by regulating the functional connections between the NTS-hippocampus,LC-primary somatosensory cortex and RN-putamen.In addition,we found that after chronic taVNS stimulation intervention,the changes in the functional connection between the RN and putamen are significantly associated with the primary outcome measured in the current study—the changes in the number of migraine attacks days before and after treatment.Since the RN is the main synthesis and projection nucleus of serotonin in the central nervous system,meanwhile serotonin plays an important role in pain regulation and improvement of migraine symptoms,the results of this study suggest that chronic taVNS may be related to the change of the nucleus raphe projecting serotonin in the putamen.and thus plays a role in improving migraine syndromes.Lastly,in order to refine the response of different subregions of the thalamus in migraine patients to taVNS treatment,we use a functional segmentation method to analyze the FC of thalamus in migraine patients.By dividing the thalamus into 6 subregions,we investigated a detailed role of thalamus in migraine patients when using taVNS as treatment.The results showed that the functional connection between the thalamus subregions of the visual cortex and the bilateral primary sensory cortex was changed before and after treatment,and this change was also significantly correlated with the improvement of the clinical symptoms of migraine patients(the number of migraine attacks).This part of the study explored the potential imaging biomarkers of taVNS treatment in migraine patients,and provided new path for the evaluation and prognosis of the individualized use of taVNS in the treatment of migraine in the future.