Neuromodulation in migraine: state of the art and perspectives

Hallmarks of primary headache: part 1 - migraine

BACKGROUND AND AIM

Migraine is a common disabling conditions which, globally, affects 15.2% of the population. It is the second cause of health loss in terms of years lived with disability, the first among women. Despite being so common, it is poorly recognised and too often undertreated. Specialty centres and neurologists with specific expertise on headache disorders have the knowledge to provide specific care: however, those who do not regularly treat patients with migraine will benefit from a synopsis on the most relevant and updated information about this condition. This paper presents a comprehensive view on the hallmarks of migraine, from genetics and diagnostic markers, up to treatments and societal impact, and reports the elements that identify migraine specific features.

MAIN RESULTS

The most relevant hallmark of migraine is that it has common and individual features together. Besides the known clinical manifestations, migraine presentation is heterogeneous with regard to frequency of attacks, presence of aura, response to therapy, associated comorbidities or other symptoms, which likely reflect migraine heterogeneous genetic and molecular basis. The amount of therapies for acute and for prophylactic treatment is really wide, and one of the difficulties is with finding the best treatment for the single patient. In addition to this, patients carry out different daily life activities, and might show lifestyle habits which are not entirely adequate to manage migraine day by day. Education will be more and more important as a strategy of brain health promotion, because this will enable reducing the amount of subjects needing specialty care, thus leaving it to those who require it in reason of refractory condition or presence of comorbidities.

CONCLUSIONS

Recognizing the hallmarks of migraine and the features of single patients enables prescribing specific pharmacological and non-pharmacological treatments. Medical research on headaches today particularly suffers from the syndrome of single-disease approach, but it is important to have a cross-sectional and joint vision with other close specialties, in order to treat our patients with a comprehensive approach that a heterogeneous condition like migraine requires.

Combined Invasive Peripheral Nerve Stimulation in the Management of Chronic Post-Intracranial Disorder Headache: A Case Report

The introduction of ventricular shunts dramatically changed the outcome and quality of life of hydrocephalic patients. However, shunt surgery continues to be associated with numerous adverse events. Headache is one of the most common complications after shunt operation. It is often of prolonged duration, the symptoms resemble those of migraine, and pain does not respond to medication. We propose invasive peripheral nerve stimulation as a potential solution in the treatment of patients suffering from chronic headache associated with shunted hydrocephalus. A young woman presented with daily holocephalic headache with diffuse pain exacerbated by lying down. Imaging revealed panventricular enlargement and possible aqueduct stenosis. When a ventriculoperitoneal shunt was placed, clinical symptoms resolved. Nevertheless, she gradually exacerbated after a second valve replacement due to wound infection. Imaging revealed decompressed ventricles and appropriate shunt placement. The diagnosis of chronic post-intracranial disorder headache was set. Therefore, occipital nerve stimulation was applied and, considering that the patient did not have a total response, bilateral parietal stimulation was added. Three months after the combined PNS, she experienced total remission of headache. Combined PNS eases refractory headaches much more than occipital nerve stimulation alone and could be considered as a solution for shunted hydrocephalus-associated headache.

Effectiveness of High-Frequency Repetitive Transcranial Magnetic Stimulation in Migraine: A Systematic Review and Meta-analysis

OBJECTIVE

The aim of the study was to evaluate the effectiveness of repetitive transcranial magnetic stimulation in migraine measured by decrease in pain severity or attack frequency.

METHODS

A search at the Cochrane Controlled Trials Register (CENTRAL), MEDLINE (via PubMed), Embase, CINAHL, Web of Science, and Scopus. The risk of systematic bias was rated by using the Cochrane domain-based quality assessment tool. A random-effects model was used.

RESULTS

Of 434 identified records, 8 randomized control studies were included in the meta-synthesis. All have used a high-frequency repetitive transcranial magnetic stimulation targeting the left dorsolateral prefrontal cortex. The risk of systematic bias was low. The difference between repetitive transcranial magnetic stimulation and control groups in frequency of migraine days per month was 8.1 (95% confidence interval = 4.8 - 11.4) days in favor of repetitive transcranial magnetic stimulation. Respectively, for intensity of migraine pain (scaled from 0 to 100), this difference was 13.6 (95% confidence interval = 5.3 - 21.8) points in favor of repetitive transcranial magnetic stimulation. The heterogeneity was substantial with I2 = 86%.

CONCLUSIONS

In chronic migraine, repetitive transcranial magnetic stimulation seems to have positive effects on both migraine pain severity and attack frequency compared with sham stimulation. Although the effect on pain intensity was probably clinically insignificant, repetitive transcranial magnetic stimulation reduced pain frequency by 8 days per month on average.

Effects of Synergism of Mindfulness Practice Associated With Transcranial Direct-Current Stimulation in Chronic Migraine: Pilot, Randomized, Controlled, Double-Blind Clinical Trial

Chronic migraine is a difficult disease to diagnose, and its pathophysiology remains undefined. Its symptoms affect the quality of life and daily living tasks of the affected person, leading to momentary disability. This is a pilot, randomized, controlled, double-blind clinical trial study with female patients between 18 and 65 years old with chronic migraine. The patients underwent twelve mindfulness sessions paired with anodal transcranial direct-current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC), with current intensity of 2 mA applied for 20 min, three times a week for 4 weeks. In addition, 20 min of mindfulness home practices were performed by guided meditation audio files. A total of 30 participants were evaluated after the treatment, and these were subdivided into two groups—active tDCS and sham tDCS, both set to mindfulness practice. The FFMQ-BR (Five Facet of Mindfulness Questionnaire), MIDAS (Migraine Disability Assessment), and HIT-6 (Headache Impact Test) questionnaires were used to evaluate the outcomes. After the treatment, the active mindfulness and tDCS group showed better results in all outcomes. The sham group also showed improvements, but with smaller effect sizes compared to the active group. The only significant difference in the intergroup analysis was the outcome evaluated by HIT-6 in the post treatment result. Our results provide the first therapeutic evidence of mindfulness practices associated with left DLPFC anodal tDCS with a consequent increase in the level of full attention and analgesic benefits in the clinical symptoms of patients with chronic migraine.

Remote Electrical Neuromodulation for the Acute Treatment of Migraine in Patients with Chronic Migraine: An Open-Label Pilot Study

INTRODUCTION

Remote electrical neuromodulation (REN) is a novel acute treatment of migraine. Upper arm peripheral nerves are stimulated to induce conditioned pain modulation (CPM)-an endogenous analgesic mechanism in which conditioning stimulation inhibits pain in remote body regions. The REN device (Nerivio^®, Theranica Bio-Electronics LTD., Israel) is FDA-authorized for acute treatment of migraine in adults who do not have chronic migraine. The current study assessed the consistency of response over multiple migraine attacks in people with chronic migraine who are typically characterized with severe pain intensity, high disability, and less robust response to triptans.

METHODS

This was an open-label, single-arm, dual-center study conducted on adults with chronic migraine. Participants underwent a 4-week treatment phase in which they treated their migraine headaches with the device for 45 min within 1 h of attack onset. Pain levels were recorded at baseline, 2 h, and 24 h post-treatment. Efficacy outcomes (pain relief and pain-free responses at 2 h, sustained pain relief and sustained pain-free responses at 24 h) focused on intra-individual consistency of response across multiple attacks, which was defined as response in at least 50% of the treatments.

RESULTS

Forty-two participants were enrolled, and 38 participants were evaluable for analyses; 73.7% (28/38) achieved pain relief at 2 h, 26.3% (10/38) were pain-free at 2 h, 84.4% (27/32) had sustained pain relief response at 24 h and 45.0% (9/20) had sustained pain relief response at 24 h in at least 50% of their treated attacks. The effects of REN on associated symptoms and improvement in function were also consistent. The incidence of device-related adverse events was low (1.8%).

CONCLUSIONS

REN used for a series of migraine attacks was effective and well tolerated across attacks. REN may offer a safe and effective non-pharmacological alternative for acute treatment in patients with chronic migraine.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT04161807. Retrospectively registered on November 13, 2019.

The visual system as target of non-invasive brain stimulation for migraine treatment: Current insights and future challenges

The visual network is crucially implicated in the pathophysiology of migraine. Several lines of evidence indicate that migraine is characterized by an altered visual cortex excitability both during and between attacks. Visual symptoms, the most common clinical manifestation of migraine aura, are likely the result of cortical spreading depression originating from the extrastriate area V3A. Photophobia, a clinical hallmark of migraine, is linked to an abnormal sensory processing of the thalamus which is converged with the non-image forming visual pathway. Finally, visual snow is an increasingly recognized persistent visual phenomenon in migraine, possibly caused by increased perception of subthreshold visual stimuli. Emerging research in non-invasive brain stimulation (NIBS) has vastly developed into a diversity of areas with promising potential. One of its clinical applications is the single-pulse transcranial magnetic stimulation (sTMS) applied over the occipital cortex which has been approved for treating migraine with aura, albeit limited evidence. Studies have also investigated other NIBS techniques, such as repetitive TMS (rTMS) and transcranial direct current stimulation (tDCS), for migraine prophylaxis but with conflicting results. As a dynamic brain disorder with widespread pathophysiology, targeting migraine with NIBS is challenging. Furthermore, unlike the motor cortex, evidence suggests that the visual cortex may be less plastic. Controversy exists as to whether the same fundamental principles of NIBS, based mainly on findings in the motor cortex, can be applied to the visual cortex. This review aims to explore existing literature surrounding NIBS studies on the visual system of migraine. We will first provide an overview highlighting the direct implication of the visual network in migraine. Next, we will focus on the rationale behind using NIBS for migraine treatment, including its effects on the visual cortex, and the shortcomings of currently available evidence. Finally, we propose a broader perspective of how novel approaches, the concept of brain networks and the integration of multimodal imaging with computational modeling, can help refine current NIBS methods, with the ultimate goal of optimizing a more individualized treatment for migraine.

Cathodal tDCS Guided by Thermography as Adjunctive Therapy in Chronic Migraine Patients: A Sham-Controlled Pilot Study

Objective: To explore the efficacy of cathodal tDCS applied ipsilateral to the cold patch, as determined by thermographic evaluation, in the treatment of chronic migraine. Background: Transcranial direct current stimulation (tDCS) is a non-invasive and safe technique that modulates the activity of the underlying cerebral cortex. tDCS has been extensively tested as a possible treatment for chronic pain and migraine with controversial results mainly due to the different setting procedure and location of electrodes. Since the presence of a hypothermic patch region detected through thermography has been suggested as a possible support for headache diagnosis, this "cold patch" could considered as possible effective location for tDCS application. Methods: Forty-five patients with chronic migraine were randomized to receive either cathodal (25 patients) or sham tDCS, for 5 consecutive daily sessions plus a recall session after 1 month. Cathodal tDCS was delivered at 1.5 mA for 15 min in each session. Subjects were evaluated before treatment (baseline, T0), and after 10 (T10), 60 (T60), and 120 (T120) days after treatment. The number of attacks, duration of attacks, pain intensity, number of days with headache, and number of analgesics were collected at each time evaluation. Results: Patients in the tDCS group showed a significant improvement compared to the sham group, during the whole study period in the frequency of migraine attacks (tDCS vs. sham: -47.8 ± 50.1% vs. -14.2 ± 16.5%, p = 0.004), number of days with headache (tDCS vs. sham: -42.7 ± 65.4% vs. -11.3 ± 18.0%, p = 0.015), duration of attacks (tDCS vs. sham: -29.1 ± 43.4% vs. -7.5 ± 17.6%, p = 0.016), intensity of the pain during an attack (tDCS vs. sham -31.1 ± 36.9% vs. 8.3 ± 13.5%, p = 0.004), and number of analgesics (tDCS vs. sham -54.3 ± 37.4% vs. -16.0 ± 19.6%, p < 0.0001). Conclusion: Our results suggest that cathodal tDCS is an effective adjuvant technique in migraine provided that an individual correct montage of the electrodes is applied, according to thermographic investigation.

Frontal infrared thermography in healthy individuals and chronic migraine patients: Reliability of the method

BACKGROUND

The use of frontal infrared thermography in the diagnosis of primary headaches provided scattering results due to measurement fluctuations and different types of headaches or research protocols.

OBJECTIVE

This study aims to assess the reliability of frontal infrared thermography in healthy individuals and provide a preliminary evaluation in chronic migraine patients using a commercial infrared thermal camera.

METHODS

Thermographic images were acquired in 20 controls and 15 patients at three consecutive time-points in two daily sessions. The Side Difference and Asymmetry Index parameters were defined. The reproducibility of the measurements, the correlation of Asymmetry Index and Side Difference with clinical evaluations and patient perceptions, and the ability of the parameters to discriminate between patients and controls were investigated.

RESULTS

We reported a good reproducibility of the measurements (Inter-class Correlation Coefficient > 0.75 and Coefficient of Variation < 13.4%), independent from external factors. The Side Difference was significantly different between patients and controls (  p < 0.001). The Asymmetry Index showed good correlation with the side of unilateral pain (  p = 0.0056).

CONCLUSIONS

Frontal infrared thermography can be used to quantify the difference between the right and the left side of frontal vascular changes in chronic migraine patients, provided that standardized conditions are satisfied.

Brain Correlates of Single Trial Visual Evoked Potentials in Migraine: More Than Meets the Eye

Background: Using conventional visual evoked potentials (VEPs), migraine patients were found to be hyperresponsive to visual stimulus. Considering that a significant portion of neuronal activity is lost for analysis in the averaging process of conventional VEPs, in this study we investigated visual evoked responses of migraine patients and healthy volunteers using a different approach: single trial analysis. This method permits to preserve all stimulus-induced neuronal activations, whether they are synchronized or not. In addition, we used MRI voxel-based morphometry to search for cortical regions where gray matter volume correlated with single trial (st) VEP amplitude. Finally, using resting-state functional MRI, we explored the connectivity between these regions. Results: stVEP amplitude was greater in episodic migraine patients than in healthy volunteers. Moreover, in migraine patients it correlated positively with gray matter volume of several brain areas likely involved in visual processing, mostly belonging to the ventral attention network. Finally, resting state functional connectivity corroborated the existence of functional interactions between these areas and helped delineating their directions. Conclusions: st-VEPs appear to be a reliable measure of cerebral responsiveness to visual stimuli. Mean st-VEP amplitude is higher in episodic migraine patients compared to controls. Visual hyper-responsiveness in migraine involves several functionally-interconnected brain regions, suggesting that it is the result of a complex multi-regional process coupled to stimulus driven attention systems rather than a localized alteration.

Modulation of brainstem activity and connectivity by respiratory-gated auricular vagal afferent nerve stimulation in migraine patients

Migraine pathophysiology includes altered brainstem excitability, and recent neuromodulatory approaches aimed at controlling migraine episodes have targeted key brainstem relay and modulatory nuclei. In this study, we evaluated the impact of respiratory-gated auricular vagal afferent nerve stimulation (RAVANS), a novel neuromodulatory intervention based on an existing transcutaneous vagus nerve stimulation approach, in the modulation of brainstem activity and connectivity in migraine patients. We applied 3T-functional magnetic resonance imaging with improved in-plane spatial resolution (2.62 × 2.62 mm) in episodic migraine (interictal) and age- and sex-matched healthy controls to evaluate brain response to RAVANS (gated to either inhalation or exhalation) and sham stimulation. We further investigated RAVANS modulation of tactile trigeminal sensory afference response in the brainstem using air-puff stimulation directed to the forehead during functional magnetic resonance imaging. Compared with sham and inhalatory-gated RAVANS (iRAVANS), exhalatory-gated RAVANS (eRAVANS) activated an ipsilateral pontomedullary region consistent with nucleus tractus solitarii (NTS). During eRAVANS, NTS connectivity was increased to anterior insula and anterior midcingulate cortex, compared with both sham and iRAVANS, in migraine patients. Increased connectivity was inversely correlated with relative time to the next migraine attack, suggesting clinical relevance to this change in connectivity. Poststimulation effects were also noted immediately after eRAVANS, as we found increased activation in putative pontine serotonergic (ie, nucleus raphe centralis) and noradrenergic (ie, locus coeruleus) nuclei in response to trigeminal sensory afference. Regulation of activity and connectivity of brainstem and cortical regions involved in serotonergic and noradrenergic regulation and pain modulation may constitute an underlying mechanism supporting beneficial clinical outcomes for eRAVANS applied for episodic migraine.

Evidence of activation of vagal afferents by non-invasive vagus nerve stimulation: An electrophysiological study in healthy volunteers

Background Benefits of cervical non-invasive vagus nerve stimulation (nVNS) devices have been shown in episodic cluster headache and preliminarily suggested in migraine, but direct evidence of vagus nerve activation using such devices is lacking. Vagal somatosensory evoked potentials (vSEPs) associated with vagal afferent activation have been reported for invasive vagus nerve stimulation (iVNS) and non-invasive auricular vagal stimulation. Here, we aimed to show and characterise vSEPs for cervical nVNS. Methods vSEPs were recorded for 12 healthy volunteers who received nVNS over the cervical vagus nerve, bipolar electrode/DS7A stimulation over the inner tragus, and nVNS over the sternocleidomastoid (SCM) muscle. We measured peak-to-peak amplitudes (P1-N1), wave latencies, and N1 area under the curve. Results P1-N1 vSEPs were observed for cervical nVNS (11/12) and auricular stimulation (9/12), with latencies similar to those described previously, whereas SCM stimulation revealed only a muscle artefact with a much longer latency. A dose-response analysis showed that cervical nVNS elicited a clear vSEP response in more than 80% of the participants using an intensity of 15 V. Conclusion Cervical nVNS can activate vagal afferent fibres, as evidenced by the recording of far-field vSEPs similar to those seen with iVNS and non-invasive auricular stimulation.

Cerebral metabolism before and after external trigeminal nerve stimulation in episodic migraine

Background and aim A recent sham-controlled trial showed that external trigeminal nerve stimulation (eTNS) is effective in episodic migraine (MO) prevention. However, its mechanism of action remains unknown. We performed 18-fluorodeoxyglucose positron emission tomography (FDG-PET) to evaluate brain metabolic changes before and after eTNS in episodic migraineurs. Methods Twenty-eight individuals were recruited: 14 with MO and 20 healthy volunteers (HVs). HVs underwent a single FDG-PET, whereas patients were scanned at baseline, directly after a first prolonged session of eTNS (Cefaly®) and after three months of treatment (uncontrolled study). Results The frequency of migraine attacks significantly decreased in compliant patients ( N = 10). Baseline FDG-PET revealed a significant hypometabolism in fronto-temporal areas, especially in the orbitofrontal (OFC) and rostral anterior cingulate cortices (rACC) in MO patients. This hypometabolism was reduced after three months of eTNS treatment. Conclusion Our study shows that metabolic activity of OFC and rACC, which are pivotal areas in central pain and behaviour control, is decreased in migraine. This hypometabolism is reduced after three months of eTNS. eTNS might thus exert its beneficial effects via slow neuromodulation of central pain-controlling areas, a mechanism also previously reported in chronic migraine and cluster headache after percutaneous occipital nerve stimulation. However, this finding needs to be confirmed by further studies using a sham condition.

Migraine prevention with percutaneous mastoid electrical stimulator: A randomized double-blind controlled trial

Objective To evaluate the effectiveness and safety of episodic migraine prevention with the percutaneous mastoid electrical stimulator (PMES). Methods This was a randomized, double-blind, and sham-controlled trial that involved four medical centers. Episodic patients with at least two migraine attacks every month were randomly 1:1 to PMES or sham stimulation treatment. The treatments were performed daily for 45 minutes over 3 months. The primary outcomes were change in migraine days per month and the 50% response rate. Results The PMES group had a significantly greater reduction of migraine days in the third month than the sham group (-71.3% vs. -14.4%, p < 0.001). The 50% response rate of migraine days in the PMES group (≥50% reduction of migraine days compared with the baseline) was significantly higher than that in the sham group (82.5% vs. 17.5%, p < 0.001). In the PMES group, 60% of the patients had a ≥75% reduction of migraine days in the third month, and 35% of the patients had no migraine attack in the third month. No patients in the sham group had a ≥75% reduction of migraine days. There were no adverse events in either group. Conclusion Treatment of migraine using non-invasive PMES was safe and effective.

What Have We Learned From Brain Functional Connectivity Studies in Migraine Headache?

Over the past 20 years, headache syndromes, especially migraine, have benefited significantly from the knowledge gained through neuroimaging studies. This article is focused on the neuroimaging studies of the functional organization and connectivity of the migraine brain. First, data sources and the study design elements in functional neuroimaging studies of the brain connectivity in migraine headaches are discussed. Then, the article reviews the findings to date and discusses how functional connectivity studies have contributed to a better understanding of the mechanisms of the migraine disease by extending the focus from a single region or structure to a network of regions and structures and the interactions among them. Finally, the potential scenarios for the translation of connectivity knowledge to the benefit for patients are discussed.