Non-Invasive Vagus Nerve Stimulation for the ACute Treatment of Cluster Headache: Findings From the Randomized, Double-Blind, Sham-Controlled ACT1 Study

Vagus nerve stimulation in cerebral stroke: biological mechanisms, therapeutic modalities, clinical applications, and future directions

Stroke is a major disorder of the central nervous system that poses a serious threat to human life and quality of life. Many stroke victims are left with long-term neurological dysfunction, which adversely affects the well-being of the individual and the broader socioeconomic impact. Currently, post-stroke brain dysfunction is a major and difficult area of treatment. Vagus nerve stimulation is a Food and Drug Administration-approved exploratory treatment option for autism, refractory depression, epilepsy, and Alzheimer's disease. It is expected to be a novel therapeutic technique for the treatment of stroke owing to its association with multiple mechanisms such as altering neurotransmitters and the plasticity of central neurons. In animal models of acute ischemic stroke, vagus nerve stimulation has been shown to reduce infarct size, reduce post-stroke neurological damage, and improve learning and memory capacity in rats with stroke by reducing the inflammatory response, regulating blood-brain barrier permeability, and promoting angiogenesis and neurogenesis. At present, vagus nerve stimulation includes both invasive and non-invasive vagus nerve stimulation. Clinical studies have found that invasive vagus nerve stimulation combined with rehabilitation therapy is effective in improving upper limb motor and cognitive abilities in stroke patients. Further clinical studies have shown that non-invasive vagus nerve stimulation, including ear/cervical vagus nerve stimulation, can stimulate vagal projections to the central nervous system similarly to invasive vagus nerve stimulation and can have the same effect. In this paper, we first describe the multiple effects of vagus nerve stimulation in stroke, and then discuss in depth its neuroprotective mechanisms in ischemic stroke. We go on to outline the results of the current major clinical applications of invasive and non-invasive vagus nerve stimulation. Finally, we provide a more comprehensive evaluation of the advantages and disadvantages of different types of vagus nerve stimulation in the treatment of cerebral ischemia and provide an outlook on the developmental trends. We believe that vagus nerve stimulation, as an effective treatment for stroke, will be widely used in clinical practice to promote the recovery of stroke patients and reduce the incidence of disability.

Transcutaneous vagal nerve stimulation for treating gastrointestinal symptoms in individuals with diabetes: a randomised, double-blind, sham-controlled, multicentre trial

AIMS/HYPOTHESIS

Diabetic gastroenteropathy frequently causes debilitating gastrointestinal symptoms. Previous uncontrolled studies have shown that transcutaneous vagal nerve stimulation (tVNS) may improve gastrointestinal symptoms. To investigate the effect of cervical tVNS in individuals with diabetes suffering from autonomic neuropathy and gastrointestinal symptoms, we conducted a randomised, sham-controlled, double-blind (participants and investigators were blinded to the allocated treatment) study.

METHODS

This study included adults (aged 20-86) with type 1 or 2 diabetes, gastrointestinal symptoms and autonomic neuropathy recruited from three Steno Diabetes Centres in Denmark. Participants were randomly allocated 1:1 to receive active or sham stimulation. Active cervical tVNS or sham stimulation was self-administered over two successive study periods: 1 week of four daily stimulations and 8 weeks of two daily stimulations. The primary outcome measures were gastrointestinal symptom changes as measured using the gastroparesis cardinal symptom index (GCSI) and the gastrointestinal symptom rating scale (GSRS). Secondary outcomes included gastrointestinal transit times and cardiovascular autonomic function.

RESULTS

Sixty-eight participants were randomised to the active group, while 77 were randomised to the sham group. Sixty-three in the active and 68 in the sham group remained for analysis in study period 1, while 62 in each group were analysed in study period 2. In study period 1, active and sham tVNS resulted in similar symptom reductions (GCSI: -0.26 ± 0.64 vs -0.17 ± 0.62, p=0.44; GSRS: -0.35 ± 0.62 vs -0.32 ± 0.59, p=0.77; mean ± SD). In study period 2, active stimulation also caused a mean symptom decrease that was comparable to that observed after sham stimulation (GCSI: -0.47 ± 0.78 vs -0.33 ± 0.75, p=0.34; GSRS: -0.46 ± 0.90 vs -0.35 ± 0.79, p=0.50). Gastric emptying time was increased in the active group compared with sham (23 min vs -19 min, p=0.04). Segmental intestinal transit times and cardiovascular autonomic measurements did not differ between treatment groups (all p>0.05). The tVNS was well-tolerated.

CONCLUSIONS/INTERPRETATION

Cervical tVNS, compared with sham stimulation, does not improve gastrointestinal symptoms among individuals with diabetes and autonomic neuropathy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04143269 FUNDING: The study was funded by the Novo Nordisk Foundation (grant number NNF180C0052045).

Research hotspots and frontiers of cluster headaches: a bibliometric analysis

Background

Extensive research on cluster headaches (CHs) has been conducted worldwide; however, there is currently no bibliometric research on CHs. Therefore, this study aimed to analyze the current research hotspots and frontiers of CHs over the past decade.

Methods

Raw data on CHs was obtained from the Web of Science Core Collection database from 2014 to 2023. CiteSpace V6.2 R7 (64 bit) and Microsoft Excel were used to assess the annual publication volume, authors, countries, and references. VOSviewer 1.6.19 software was used to assess the institutions, cited authors, and keywords, and co-occurrence and clustering functions were applied to draw a visual knowledge map.

Results

In the past decade, the overall annual publication volume of articles related to CHs has increased year by year, showing promising development prospects. The total 1909 articles contained six types of literature, among which the proportion of original research articles was the highest (1,270 articles, 66.53%), published in 201 journals. Cephalalgia (439 articles, 23.00%) had the highest publication volume, and the Lancet was the journal with the highest impact factor (IF = 168.9). Furthermore, the United States of America was the country with the most published papers (584 articles, 30.60%), University of London was the research institution with the most published papers (142 articles, 7.44%), and Goodsby, Peter J was found to be the most prolific author (38 articles, 1.99%).

Conclusion

This study may provide some direction for subsequent researcher on CHs. The hotspots and frontiers of future research on CHs are suggested as follows: in basic medicine, more attention should be paid to pathophysiology, especially on increasing research on the pathogenesis mediated by CGRP; in clinical medicine, more attention should be paid to the design of evidence-based medicine methodology, especially the strict design, including double-blind, questionnaire, and follow-up, in randomized controlled trials, using high-quality articles for meta-analyses, and recommending high-level evidence; therapeutic techniques need to be further explored, suggesting the implementation of transcranial magnetic stimulation of the cortex, and stimulation of the sphinopalatine ganglia and occipital nerve to achieve peripheral neuromodulation. Furthermore, chronic migraine and insomnia are inextricably linked to CHs.

Autonomic dysfunction and treatment strategies in intracerebral hemorrhage

AIMS

Autonomic dysfunction with central autonomic network (CAN) damage occurs frequently after intracerebral hemorrhage (ICH) and contributes to a series of adverse outcomes. This review aims to provide insight and convenience for future clinical practice and research on autonomic dysfunction in ICH patients.

DISCUSSION

We summarize the autonomic dysfunction in ICH from the aspects of potential mechanisms, clinical significance, assessment, and treatment strategies. The CAN structures mainly include insular cortex, anterior cingulate cortex, amygdala, hypothalamus, nucleus of the solitary tract, ventrolateral medulla, dorsal motor nucleus of the vagus, nucleus ambiguus, parabrachial nucleus, and periaqueductal gray. Autonomic dysfunction after ICH is closely associated with neurological functional outcomes, cardiac complications, blood pressure fluctuation, immunosuppression and infection, thermoregulatory dysfunction, hyperglycemia, digestive dysfunction, and urogenital disturbances. Heart rate variability, baroreflex sensitivity, skin sympathetic nerve activity, sympathetic skin response, and plasma catecholamine concentration can be used to assess the autonomic functional activities after ICH. Risk stratification of patients according to autonomic functional activities, and development of intervention approaches based on the restoration of sympathetic-parasympathetic balance, would potentially improve clinical outcomes in ICH patients.

CONCLUSION

The review systematically summarizes the evidence of autonomic dysfunction and its association with clinical outcomes in ICH patients, proposing that targeting autonomic dysfunction could be potentially investigated to improve the clinical outcomes.

Neuromodulation for Craniofacial Pain and Headaches

Headaches and facial pain are highly prevalent diseases but are often difficult to treat. Though there have been significant advances in medical management, many continue to suffer from refractory pain. Neuromodulation has been gaining interest for its therapeutic purposes in many chronic pain conditions, including headaches and facial pain. There are many potential targets of neuromodulation for headache and facial pain, and some have more robust evidence in favor of their use than others. Despite the need for more high-quality research, the available evidence for the use of neuromodulation in treating headaches and facial pain is promising. Considering the suffering that afflicts patients with intractable headache, neuromodulation may be an appropriate tool to improve not only pain but also disability and quality of life.

Baseline demographics and disease characteristics of patients with episodic or chronic cluster headache: data from two phase 3 randomized clinical trials in Europe and North America

Objective

Two phase 3 galcanezumab trials were conducted in Europe and North America to analyze the reduction of weekly cluster headache (CH) attack frequency in populations with episodic and chronic CH. The current study aims to illustrate prospectively recorded baseline clinical data from these trials and to identify possible predictors of response.

Methods

Patients (aged 18-65 years) met The International Classification of Headache Disorders 3rd edition-beta criteria for CH. Attacks were evaluated using an electronic headache diary for 7-day (episodic) or 14-day (chronic) eligibility assessments before patients were randomized 1:1 to monthly subcutaneous galcanezumab 300 mg or placebo.

Results

Data were collected from 106 patients with episodic and 237 with chronic CH. Overall, the mean age [standard deviation] was 45.4 [11.0] years; patients were predominantly White (84.5%), male (75.8%), and European (77.6%). Patients with episodic CH reported 17.5 [10.0] attacks/week; patients with chronic CH reported 18.8 [10.2] attacks/week. The average pain severity score (range 0-4) was 2.5 [0.7] for episodic CH and 2.7 [0.7] for chronic CH. Higher attack frequency was a possible predictor of response to galcanezumab; potential negative predictors of response were greater attack severity and duration.

Conclusion

This large dataset of patients with CH provides reliable systematically and prospectively collected information on disease characteristics. The analysis in episodic CH underscores potential predictors of response worth considering for future CH trial design.

Clinical Trial Registration

ClinicalTrials.gov, identifiers: NCT02397473 and NCT02438826.

Non-invasive neuromodulation: an emerging intervention for visceral pain in gastrointestinal disorders

Gastrointestinal (GI) disorders, which extend from the esophagus to the anus, are the most common diseases of the GI tract. Among these disorders, pain, encompassing both abdominal and visceral pain, is a predominant feature, affecting the patients' quality of life and imposing a substantial financial burden on society. Pain signals originating from the gut intricately shape brain dynamics. In response, the brain sends appropriate descending signals to respond to pain through neuronal inhibition. However, due to the heterogeneous nature of the disease and its limited pathophysiological understanding, treatment options are minimal and often controversial. Consequently, many patients with GI disorders use complementary and alternative therapies such as neuromodulation to treat visceral pain. Neuromodulation intervenes in the central, peripheral, or autonomic nervous system by alternating or modulating nerve activity using electrical, electromagnetic, chemical, or optogenetic methodologies. Here, we review a few emerging noninvasive neuromodulation approaches with promising potential for alleviating pain associated with functional dyspepsia, gastroparesis, irritable bowel syndrome, inflammatory bowel disease, and non-cardiac chest pain. Moreover, we address critical aspects, including the efficacy, safety, and feasibility of these noninvasive neuromodulation methods, elucidate their mechanisms of action, and outline future research directions. In conclusion, the emerging field of noninvasive neuromodulation appears as a viable alternative therapeutic avenue for effectively managing visceral pain in GI disorders.

Transcutaneous Auricular Vagal Nerve Stimulation Is Effective for the Treatment of Functional Dyspepsia: A Multicenter, Randomized Controlled Study

INTRODUCTION

Vagal nerve stimulation (VNS) can be used to modulate gastrointestinal motility, inflammation, and nociception. However, it remains unclear whether VNS is effective in adult patients with functional dyspepsia (FD). We investigated the effectiveness of transcutaneous auricular VNS (taVNS) in patients with FD.

METHODS

Consecutive patients with FD meeting Rome IV criteria with modified FD Symptom Diary score ≥10 were enrolled. Patients were randomly allocated to 10-Hz taVNS (V10 group), 25-Hz taVNS (V25 group), or sham group, with 30 minutes of treatment twice a day for 4 weeks. The primary outcome was the response rate at week 4, defined as the proportion of patients whose modified FD Symptom Diary score was reduced ≥5 when compared with the baseline. Secondary outcomes included adequate relief rate and adverse events.

RESULTS

A total of 300 patients were randomized to V10 (n = 101), V25 (n = 99), and sham groups (n = 100). After 4 weeks of treatment, V10 and V25 groups had a higher response rate (81.2% vs 75.9% vs 47%, both P < 0.001) and adequate relief rate (85.1% vs 80.8% vs 67%, both P < 0.05) compared with the sham group. There was no significant difference between V10 and V25 in response rate and adequate relief rate (both P > 0.05). The efficacy of taVNS (both 10 and 25 Hz) lasted at week 8 and week 12 during follow-up period. Adverse events were all mild and comparable among the 3 groups (1%-3%).

DISCUSSION

Our study firstly showed that 4-week taVNS (both 10 and 25 Hz) was effective and safe for the treatment of adult FD ( clinicaltrials.gov number: NCT04668534).

Cluster headache: state of the art in treatment

Cluster headache (CH) is the most common and devastating autonomic headache with multiple and recent advances in treatment. However, it usually goes unrecognized and is found to have a delayed and inappropriate treatment. This paper aims to review the current therapeutic options for patients with CH. We conducted a narrative literature review on the treatments available for this condition using the American Academy of Neurology (AAN) classification of therapeutic evidence. We found effective and safe pharmacological and non-pharmacological therapies with heterogeneity of clinical trial designs for patients with CH, and they are divided into three phases, namely, transitional, acute, and preventive interventions. Prednisone (A) is the most studied treatment in the transitional phase; acute attacks are treated using triptans (A), oxygen (A), and non-invasive transcutaneous vagal nerve stimulation (A). Verapamil (A) and monoclonal antibodies (possible A) are considered the first options in preventive treatments, followed by multiple pharmacological and non-pharmacological options in prophylactic treatments. In conclusion, numerous effective and safe treatments are available in treating patients with episodic, chronic, and pharmacoresistant CH according to the clinical profile of each patient.

European Academy of Neurology guidelines on the treatment of cluster headache

BACKGROUND AND PURPOSE

Cluster headache is a relatively rare, disabling primary headache disorder with a major impact on patients' quality of life. This work presents evidence-based recommendations for the treatment of cluster headache derived from a systematic review of the literature and consensus among a panel of experts.

METHODS

The databases PubMed (Medline), Science Citation Index, and Cochrane Library were screened for studies on the efficacy of interventions (last access July 2022). The findings in these studies were evaluated according to the recommendations of the European Academy of Neurology, and the level of evidence was established using GRADE (Grading of Recommendations Assessment, Development, and Evaluation).

RECOMMENDATIONS

For the acute treatment of cluster headache attacks, there is a strong recommendation for oxygen (100%) with a flow of at least 12 L/min over 15 min and 6 mg subcutaneous sumatriptan. Prophylaxis of cluster headache attacks with verapamil at a daily dose of at least 240 mg (maximum dose depends on efficacy and tolerability) is recommended. Corticosteroids are efficacious in cluster headache. To reach an effect, the use of at least 100 mg prednisone (or equivalent corticosteroid) given orally or at up to 500 mg iv per day over 5 days is recommended. Lithium, topiramate, and galcanezumab (only for episodic cluster headache) are recommended as alternative treatments. Noninvasive vagus nerve stimulation is efficacious in episodic but not chronic cluster headache. Greater occipital nerve block is recommended, but electrical stimulation of the greater occipital nerve is not recommended due to the side effect profile.

Effects of Non-Invasive Neuromodulation of the Vagus Nerve for the Management of Cluster Headache: A Systematic Review

BACKGROUND

Cluster headache (CH) is a type of headache that has a global prevalence of 0.5-3/1000 people, provokes severe, strictly unilateral pain through the first branch of the trigeminal nerve, and is associated with observable autonomous responses. CH provokes intense pain and decreases quality of life.

OBJECTIVE

In this study, we aimed to carry out a systematic review of the effectiveness of non-invasive neuromodulation of the vagus nerve in patients with cluster headaches, which was registered on PROSPERO No. CRD42021265126.

METHODS

Six databases were used from their date of inception to February 2023 to obtain studies with the group intervention of non-invasive neuromodulation of the vagus nerve for cluster headache, with outcomes based on pain attacks, duration, and disabilities. Data on the subjects, group intervention, main outcomes, and results were collected by two authors.

RESULTS

The search provided 1003 articles, with three clinical trials being eligible for inclusion in the review. The methodological quality scores ranged from 6 to 8 points (mean: 7.3, SD: 0.8) out of a maximum of 10 points. The post-treatment results showed some positive effects using n-VNS as a treatment for cluster headache, more specifically regarding cervical neuromodulation of the vagus nerve.

CONCLUSIONS

The systematic review found moderate-to-high-quality evidence supporting that n-VNS and cervical n-VNS may have some positive effects at the end of the treatment being effective to relieve the frequency and intensity of cluster headaches. The poor quantity of studies available and the lack of homogeneity in the study protocols did not allow the pooling of data for a meta-analysis.

Baseline heart rate variability predicts placebo hypoalgesia in men, but not women

Introduction

Placebo hypoalgesic effects vary greatly across individuals, making them challenging to control for in clinical trials and difficult to use in treatment. We investigated the potential of resting vagally-mediated heart rate variability (vmHRV) to help predict the magnitude of placebo responsiveness.

Methods

In two independent studies (total N = 77), we administered a placebo paradigm after measuring baseline HRV. In Study I, we delivered heat pain to the forearm, on skin patches treated with "real" and "control" cream (identical inactive creams). In Study II, electrical pulses to the forearm were modulated by sham transcutaneous electrical nerve stimulation. We combined data from both studies to evaluate the relationship between vagally-mediated HRV (vmHRV) parameters and the placebo response size, while also assessing sex differences in this relationship.

Results and Discussion

This revealed a positive association between vmHRV and the degree of pain relief, and this effect was driven by men. These results not only reveal new insights into the (sex-specific) mechanisms of placebo hypoalgesia, but also suggest that measuring vmHRV may be helpful in predicting placebo responsiveness. Given that placebo hypoalgesic effects contribute substantially to treatment outcomes, such a non-invasive and easily obtained predictor would be valuable in the context of personalized medicine.

Current treatment options for cluster headache: limitations and the unmet need for better and specific treatments-a consensus article

AIM

Treatment for cluster headache is currently based on a trial-and-error approach. The available preventive treatment is unspecific and based on few and small studies not adhering to modern standards. Therefore, the authors collaborated to discuss acute and preventive treatment in cluster headache, addressing the unmet need of safe and tolerable preventive medication from the perspectives of people with cluster headache and society, headache specialist and cardiologist.

FINDINGS

The impact of cluster headache on personal life is substantial. Mean annual direct and indirect costs of cluster headache are more than 11,000 Euros per patient. For acute treatment, the main problems are treatment response, availability, costs and, for triptans, contraindications and the maximum use allowed. Intermediate treatment with steroids and greater occipital nerve blocks are effective but cannot be used continuously. Preventive treatment is sparsely studied and overall limited by relatively low efficacy and side effects. Neurostimulation is a relevant option for treatment-refractory chronic patients. From a cardiologist's perspective use of verapamil and triptans may be worrisome and regular follow-up is essential when using verapamil and lithium.

CONCLUSION

We find that there is a great and unmet need to pursue novel and targeted preventive modalities to suppress the horrific pain attacks for people with cluster headache.

Trigeminal Autonomic Cephalalgias and Neuralgias in Children and Adolescents: a Narrative Review

PURPOSE OF REVIEW

To summarize the available literature as well as the authors' experience on trigeminal autonomic cephalalgias (TACs) and cranial neuralgias in children and adolescents.

RECENT FINDINGS

While TACs and cranial neuralgias are rare in children, several recent case series have been published. TACs in children share most of the clinical features of TACs in adults. However, there are many reported cases with clinical features which overlap more than one diagnosis, suggesting that TACs may be less differentiated in youth. Indomethacin-responsive cases of cluster headache and SUNCT/SUNA have been reported in children, whereas in adults indomethacin is usually reserved for paroxysmal hemicrania and hemicrania continua. Neuralgias appear to be rare in children. Clinical features are often similar to adult cases, though clinicians should maintain a high index of suspicion for underlying causes.

Management of cluster headache: Treatments and their mechanisms

BACKGROUND

The management of cluster headache is similar to that of other primary headache disorders and can be broadly divided into acute and preventive treatments. Acute treatments for cluster headache are primarily delivered via rapid, non-oral routes (such as inhalation, nasal, or subcutaneous) while preventives include a variety of unrelated treatments such as corticosteroids, verapamil, and galcanezumab. Neuromodulation is becoming an increasingly popular option, both non-invasively such as vagus nerve stimulation when medical treatment is contraindicated or side effects are intolerable, and invasively such as occipital nerve stimulation when medical treatment is ineffective. Clinically, this collection of treatment types provides a range of options for the informed clinician. Scientifically, this collection provides important insights into disease mechanisms.

METHODS

Two authors performed independent narrative reviews of the literature on guideline recommendations, clinical trials, real-world data, and mechanistic studies.

RESULTS

Cluster headache is treated with acute treatments, bridge treatments, and preventive treatments. Common first-line treatments include subcutaneous sumatriptan and high-flow oxygen as acute treatments, corticosteroids (oral or suboccipital injections) as bridge treatments, and verapamil as a preventive treatment. Some newer acute (non-invasive vagus nerve stimulation) and preventive (galcanezumab) treatments have excellent clinical trial data for episodic cluster headache, while other newer treatments (occipital nerve stimulation) have been specifically tested in treatment-refractory chronic cluster headache. Most treatments are suspected to act on the trigeminovascular system, the autonomic system, or the hypothalamus.

CONCLUSIONS

The first-line treatments have not changed in recent years, but new treatments have provided additional options for patients.

Neuroimmunomodulation of vagus nerve stimulation and the therapeutic implications

Vagus nerve stimulation (VNS) is a technology that provides electrical stimulation to the cervical vagus nerve and can be applied in the treatment of a wide variety of neuropsychiatric and systemic diseases. VNS exerts its effect by stimulating vagal afferent and efferent fibers, which project upward to the brainstem nuclei and the relayed circuits and downward to the internal organs to influence the autonomic, neuroendocrine, and neuroimmunology systems. The neuroimmunomodulation effect of VNS is mediated through the cholinergic anti-inflammatory pathway that regulates immune cells and decreases pro-inflammatory cytokines. Traditional and non-invasive VNS have Food and Drug Administration (FDA)-approved indications for patients with drug-refractory epilepsy, treatment-refractory major depressive disorders, and headaches. The number of clinical trials and translational studies that explore the therapeutic potentials and mechanisms of VNS is increasing. In this review, we first introduced the anatomical and physiological bases of the vagus nerve and the immunomodulating functions of VNS. We covered studies that investigated the mechanisms of VNS and its therapeutic implications for a spectrum of brain disorders and systemic diseases in the context of neuroimmunomodulation.

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.

Primary headache disorders: From pathophysiology to neurostimulation therapies

Primary headache disorders including migraine, cluster headache, and tension-type headache are among the most common disabling diseases worldwide. The unclear pathogenesis of primary headache disorders has led to high rates of misdiagnosis and limited available treatment options. In this review, we have summarized the pathophysiological factors for a better understanding of primary headache disorders. Advances in functional neuroimaging, genetics, neurophysiology have indicated that cortical hyperexcitability, regional brain dysfunction, central sensitization and neuroplasticity changes play vital roles in the development of primary headache disorders. Moreover, we have also discussed a series of neurostimulation approaches with their stimulation mechanism, safety and efficacy for prevention and treatment of primary headache disorders. Noninvasive or implantable neurostimulation techniques show great promise for treating refractory primary headache disorders.

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.

Electroceutical and Bioelectric Therapy: Its Advantages and Limitations

Given the long history, the field of electroceutical and bioelectric therapy has grown impressively, recognized as the main modality of mental health treatments along with psychotherapy and pharmacotherapy. Electroceutical and bioelectric therapy comprises electroconvulsive therapy (ECT), vagus nerve stimulation (VNS), repetitive transcranial magnetic stimulation (rTMS), deep brain stimulation (DBS), transcranial electrical stimulation (tES), and other brain stimulation techniques. Much empirical research has been published regarding the application guidelines, mechanism of action, and efficacy of respective brain stimulation techniques, but no comparative study that delineates the advantages and limitations of each therapy exists for a comprehensive understanding of each technique. This review provides a comparison of existing electroceutical and bioelectric techniques, primarily focusing on the therapeutic advantages and limitations of each therapy in the current electroceutical and bioelectric field.

Symptoms and pathophysiology of cluster headache. Approach to combined occipital and supraorbital neurostimulation

Cluster headache (CH) is included under section 3 - Trigeminal autonomic cephalalgias (TAC) of the International Headache Society (IHS) classification. It is one of the most frequent, painful and disabling primary headaches. Acute and preventive pharmacological treatments are often poorly tolerated and of limited effectiveness. Due to improved understanding of the pathophysiology of CH, neuromodulation devices are now considered safe and effective options for preventive and acute treatment of CH. In this paper, we review the information available to date, and present the case of a patient with disabling cluster headache highly resistant to medical treatment who underwent implantation of a peripheral nerve neurostimulation system to stimulate the supraorbital nerves (SON) and greater occipital nerve (GON) in our Pain Unit. We also review the diagnostic criteria for CH, the state of the knowledge on the pathophysiology of CH, and the role played by neuromodulation in treating this condition.

Vagus Nerve Stimulation: A Personalized Therapeutic Approach for Crohn's and Other Inflammatory Bowel Diseases

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are incurable autoimmune diseases characterized by chronic inflammation of the gastrointestinal tract. There is increasing evidence that inappropriate interaction between the enteric nervous system and central nervous system and/or low activity of the vagus nerve, which connects the enteric and central nervous systems, could play a crucial role in their pathogenesis. Therefore, it has been suggested that appropriate neuroprosthetic stimulation of the vagus nerve could lead to the modulation of the inflammation of the gastrointestinal tract and consequent long-term control of these autoimmune diseases. In the present paper, we provide a comprehensive overview of (1) the cellular and molecular bases of the immune system, (2) the way central and enteric nervous systems interact and contribute to the immune responses, (3) the pathogenesis of the inflammatory bowel disease, and (4) the therapeutic use of vagus nerve stimulation, and in particular, the transcutaneous stimulation of the auricular branch of the vagus nerve. Then, we expose the working hypotheses for the modulation of the molecular processes that are responsible for intestinal inflammation in autoimmune diseases and the way we could develop personalized neuroprosthetic therapeutic devices and procedures in favor of the patients.

Narrative Review of Noninvasive Brain Stimulation in Stroke Rehabilitation

Stroke is a disease with a high incidence and disability rate, resulting in changes in neural network and corticoid-subcortical excitability and various functional disabilities. The aim of the present study was to discuss the current status of research and limitations and potential direction in the application of noninvasive brain stimulation (NIBS) on post-stroke patients. This literature review focused on clinical studies and reviews. Literature retrieval was conducted in PubMed, Cochrane, Scopus, and CNKI, using the following keywords: Repeated transcranial magnetic stimulation, Transcranial direct current stimulation, Transcranial alternating current stimulation, Transcranial alternating current stimulation, Transcranial focused ultrasound, Noninvasive vagus nerve stimulation, Stroke, and Rehabilitation. We selected 200 relevant publications from 1985 to 2022. An overview of recent research on the use of NIBS on post-stroke patients, including its mechanism, therapeutic parameters, effects, and safety, is presented. It was found that NIBS has positive therapeutic effects on dysfunctions of motor, sensory, cognitive, speech, swallowing, and depression after stroke, but standardized stimulus programs are still lacking. The literature suggests that rTMS and tDCS are more beneficial to post-stroke patients, while tFUS and tVNS are currently less studied for post-stroke rehabilitation, but are also potential interventions.

Pain is reduced by transcutaneous cervical vagus nerve stimulation and correlated with cardiorespiratory variability measures in the context of opioid withdrawal

Over 100,000 individuals in the United States lost their lives secondary to drug overdose in 2021, with opioid use disorder (OUD) being a leading cause. Pain is an important component of opioid withdrawal, which can complicate recovery from OUD. This study's objectives were to assess the effects of transcutaneous cervical vagus nerve stimulation (tcVNS), a technique shown to reduce sympathetic arousal in other populations, on pain during acute opioid withdrawal and to study pain's relationships with objective cardiorespiratory markers. Twenty patients with OUD underwent opioid withdrawal while participating in a two-hour protocol. The protocol involved opioid cues to induce opioid craving and neutral conditions for control purposes. Adhering to a double-blind design, patients were randomly assigned to receive active tcVNS (n = 9) or sham stimulation (n = 11) throughout the protocol. At the beginning and end of the protocol, patients' pain levels were assessed using the numerical rating scale (0–10 scale) for pain (NRS Pain). During the protocol, electrocardiogram and respiratory effort signals were measured, from which heart rate variability (HRV) and respiration pattern variability (RPV) were extracted. Pre- to post- changes (denoted with a Δ) were computed for all measures. Δ NRS Pain scores were lower (P = 0.045) for the active group (mean ± standard deviation: −0.8 ± 2.4) compared to the sham group (0.9 ± 1.0). A positive correlation existed between Δ NRS pain scores and Δ RPV (Spearman's ρ = 0.46; P = 0.04). Following adjustment for device group, a negative correlation existed between Δ HRV and Δ NRS Pain (Spearman's ρ = −0.43; P = 0.04). This randomized, double-blind, sham-controlled pilot study provides the first evidence of tcVNS-induced reductions in pain in patients with OUD experiencing opioid withdrawal. This study also provides the first quantitative evidence of an association between breathing irregularity and pain. The correlations between changes in pain and changes in objective physiological markers add validity to the data. Given the clinical importance of reducing pain non-pharmacologically, the findings support the need for further investigation of tcVNS and wearable cardiorespiratory sensing for pain monitoring and management in patients with OUD.

Neuromodulation Applied to Diseases: The Case of HRV Biofeedback

The vagus or “wandering” nerve is the main branch of the parasympathetic nervous system (PNS), innervating most internal organs crucial for health. Activity of the vagus nerve can be non-invasively indexed by heart-rate variability parameters (HRV). Specific HRV parameters predict less all-cause mortality, lower risk of and better prognosis after myocardial infarctions, and better survival in cancer. A non-invasive manner for self-activating the vagus is achieved by performing a slow-paced breathing technique while receiving visual feedback of one’s HRV, called HRV-biofeedback (HRV-B). This article narratively reviews the biological mechanisms underlying the role of vagal activity and vagally mediated HRV in hypertension, diabetes, coronary heart disease (CHD), cancer, pain, and dementia. After searching the literature for HRV-B intervention studies in each condition, we report the effects of HRV-B on clinical outcomes in these health conditions, while evaluating the methodological quality of these studies. Generally, the levels of evidence for the benefits of HRV-B is high in CHD, pain, and hypertension, moderate in cancer, and poor in diabetes and dementia. Limitations and future research directions are discussed.

Vagus nerve stimulation as a novel treatment for systemic lupus erythematous: study protocol for a randomised, parallel-group, sham-controlled investigator-initiated clinical trial, the SLE-VNS study

INTRODUCTION

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease. SLE is treated with immunosuppressants with suboptimal efficacy and high risk of serious side effects. Patients with SLE have increased risk of mortality, organ damage and debilitating treatment-resistant fatigue. Autonomic nervous system dysfunction (AD) is present in approximately half of the patients and may promote autoimmunity by weakening the vagally mediated anti-inflammatory reflex. Recent studies suggest that transcutaneous vagus nerve stimulation (tVNS) has few side effects and beneficial effects on fatigue, pain, disease activity and organ function. This study investigates whether adjuvant tVNS improves measures of fatigue (primary end point), AD, clinical disease activity, inflammation, pain, organ function and quality of life.Hence, this study will contribute to the understanding of AD as a potentially important precursor of fatigue, disease activity, progression and complications in SLE, and how tVNS mechanistically may attenuate this. As adjuvant tVNS use may reduce the need for traditional immunosuppressive therapy, this trial may prompt a shift in the treatment of SLE and potentially other autoimmune disorders.

METHODS AND ANALYSIS

Eighty-four patients with SLE with fatigue and AD will be randomised 1:1 to active or sham tVNS in this double-blinded parallel-group study. In period 1 (1 week), participants will receive a 4 min tVNS 4 times daily and report on fatigue daily. After a 2-week pause, period 2 (8 weeks) will entail tVNS twice daily and participants will report on fatigue, pain and disease activity weekly. Secondary end points will be assessed before and after each period and after 1 week in period 2.

ETHICS AND DISSEMINATION

The study is approved by the Danish Medical Research Ethical Committees (case no: 2120231) and results will be published in international peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05315739.

Guidelines of the International Headache Society for Controlled Clinical Trials in Cluster Headache

In 1995, a committee of the International Headache Society developed and published the first edition of the Guidelines for Controlled Trials of Drugs in Cluster Headache. These have not been revised. With the emergence of new medications, neuromodulation devices and trial designs, an updated version of the International Headache Society Guidelines for Controlled Clinical Trials in Cluster Headache is warranted. Given the scarcity of evidence-based data for cluster headache therapies, the update is largely consensus-based, but takes into account lessons learned from recent trials and demands by patients. It is intended to apply to both drug and neuromodulation treatments, with specific proposals for the latter when needed. The primary objective is to propose a template for designing high quality, state-of-the-art, controlled clinical trials of acute and preventive treatments in episodic and chronic cluster headache. The recommendations should not be regarded as dogma and alternative solutions to particular methodological problems should be explored in the future and scientifically validated.

Recent Advances and Updates in Trigeminal Autonomic Cephalalgias

Trigeminal autonomic cephalalgias (TACs) are discrete primary headache disorders, characterized by severe unilateral head pain, typically trigeminal distribution, with ipsilateral cranial autonomic symptoms. The conditions within this group are hemicrania continua, cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing and short-lasting unilateral neuralgiform headache with autonomic symptoms. Several advances have been made in understanding the pathogenesis and evolving treatment options in TACs. This review will outline the advances and updates in each TAC.

Characterising the Features of 381 Clinical Studies Evaluating Transcutaneous Electrical Nerve Stimulation (TENS) for Pain Relief: A Secondary Analysis of the Meta-TENS Study to Improve Future Research

Background and Objectives: Characterising the features of methodologies, clinical attributes and intervention protocols, of studies is valuable to advise directions for research and practice. This article reports the findings of a secondary analysis of the features from studies screened as part of a large systematic review of TENS (the meta-TENS study). Materials and Methods: A descriptive analysis was performed on information associated with methodology, sample populations and intervention protocols from 381 randomised controlled trials (24,532 participants) evaluating TENS delivered at a strong comfortable intensity at the painful site in adults with pain, irrespective of diagnosis. Results: Studies were conducted in 43 countries commonly using parallel group design (n = 334) and one comparator group (n = 231). Mean ± standard deviation (SD) study sample size (64.05 ± 58.29 participants) and TENS group size (27.67 ± 21.90 participants) were small, with only 13 of 381 studies having 100 participants or more in the TENS group. Most TENS interventions were ‘high frequency’ (>10 pps, n = 276) and using 100 Hz (109/353 reports that stated a pulse frequency value). Of 476 comparator groups, 54.2% were active treatments (i.e., analgesic medication(s), exercise, manual therapies and electrophysical agents). Of 202 placebo comparator groups, 155 used a TENS device that did not deliver currents. At least 216 of 383 study groups were able to access other treatments whilst receiving TENS. Only 136 out of 381 reports included a statement about adverse events. Conclusions: Clinical studies on TENS are dominated by small parallel group evaluations of high frequency TENS that are often contaminated by concurrent treatment(s). Study reports tended focus on physiological and clinical implications rather than the veracity of methodology and findings. Previously published criteria for designing and reporting TENS studies were neglected and this should be corrected in future research using insights gleaned from this analysis.

Transcutaneous Cervical Vagus Nerve Stimulation Induces Changes in the Electroencephalogram and Heart Rate Variability of Healthy Dogs, a Pilot Study

Transcutaneous cervical vagus nerve stimulation (tcVNS) has been used to treat epilepsy in people and dogs. Objective electroencephalographic (EEG) and heart rate variability (HRV) data associated with tcVNS have been reported in people. The question remained whether EEG and electrocardiography (ECG) would detect changes in brain activity and HRV, respectively, after tcVNS in dogs. Simultaneous EEG and Holter recordings, from 6 client-owned healthy dogs were compared for differences pre- and post- tcVNS in frequency band power analysis (EEG) and HRV. The feasibility and tolerance of the patients to the tcVNS were also noted. In a general linear mixed model, the average power per channel per frequency band was found to be significantly different pre- and post-stimulation in the theta (p = 0.02) and alpha bands (p = 0.04). The pooled power spectral analysis detected a significant decrease in the alpha (p < 0.01), theta (p = 0.01) and beta (p = 0.035) frequencies post-stimulation. No significant interaction was observed between dog, attitude, and stimulation in the multivariate model, neither within the same dog nor between individuals. There was a significant increase in the HRV measured by the standard deviation of the inter-beat (SDNN) index (p < 0.01) and a decrease in mean heart rate (p < 0.01) after tcVNS. The tcVNS was found to be well-tolerated. The results of this pilot study suggest that EEG and ECG can detect changes in brain activity and HRV associated with tcVNS in healthy dogs. Larger randomized controlled studies are required to confirm the results of this study and to assess tcVNS potential therapeutic value.

Closed-Loop Vagus Nerve Stimulation for the Treatment of Cardiovascular Diseases: State of the Art and Future Directions

The autonomic nervous system exerts a fine beat-to-beat regulation of cardiovascular functions and is consequently involved in the onset and progression of many cardiovascular diseases (CVDs). Selective neuromodulation of the brain-heart axis with advanced neurotechnologies is an emerging approach to corroborate CVDs treatment when classical pharmacological agents show limited effectiveness. The vagus nerve is a major component of the cardiac neuroaxis, and vagus nerve stimulation (VNS) is a promising application to restore autonomic function under various pathological conditions. VNS has led to encouraging results in animal models of CVDs, but its translation to clinical practice has not been equally successful, calling for more investigation to optimize this technique. Herein we reviewed the state of the art of VNS for CVDs and discuss avenues for therapeutic optimization. Firstly, we provided a succinct description of cardiac vagal innervation anatomy and physiology and principles of VNS. Then, we examined the main clinical applications of VNS in CVDs and the related open challenges. Finally, we presented preclinical studies that aim at overcoming VNS limitations through optimization of anatomical targets, development of novel neural interface technologies, and design of efficient VNS closed-loop protocols.

Challenges and complexities in designing cluster headache prevention clinical trials: A narrative review

Objective

To provide a review of challenges in clinical trials for the preventive treatment of cluster headache (CH) and highlight considerations for future studies.

Background

Current guidelines for preventive treatment of CH are largely based on off‐label therapies supported by a limited number of small randomized controlled trials. Guidelines for clinical trial design for CH treatments from the International Headache Society were last issued in 1995.

Methods/Results

Randomized controlled clinical trials were identified in the European and/or United States clinical trial registries with a search term of “cluster headache,” and manually reviewed. Cumulatively, there were 27 unique placebo‐controlled prevention trials for episodic and/or chronic CH, of which 12 were either ongoing, not yet recruiting, or the status was unknown. Of the remaining 15 trials, 5 were terminated early and 7 of the 10 completed trials enrolled fewer patients than planned or did not report the planned sample size. A systematic search of PubMed was also utilized to identify published manuscripts reporting results from placebo‐controlled preventive trials of CH. This search yielded 16 publications, of which 7 were registered. Through critical review of trial data and published manuscripts, challenges and complexities encountered in clinical trials for the preventive treatment of CH were identified. For example, the excruciating pain associated with CH demands a suitably limited baseline duration, rapid treatment efficacy onset, and poses a specific issue regarding duration of investigational treatment period and length of exposure to placebo. In episodic CH, spontaneous remission as part of natural history, and the unpredictability and irregularity of cluster periods across patients present additional key challenges.

Conclusions

Optimal CH trial design should balance sound methodology to demonstrate efficacy of a potential treatment with patient needs and the natural history of the disease, including unique outcome measures and endpoint timings for chronic versus episodic CH.

Measuring Brain Response to Transcutaneous Vagus Nerve Stimulation (tVNS) using Simultaneous Magnetoencephalography (MEG)

Objective: Transcutaneous vagus nerve stimulation (tVNS) is form of non-invasive brain stimulation that delivers a sequence of electrical pulses to the auricular branch of the vagus nerve, and is used increasingly in the treatment of a number of health conditions such as epilepsy and depression. Recent research has focused on the efficacy of tVNS to treat different medical conditions, but there is little conclusive evidence concerning the optimal stimulation parameters.There are relatively few studies that have combined tVNS with a neuroimaging modality, and none that have attempted simultaneous magnetoencephalography (MEG) and tVNS due to the presence of large stimulation artifacts produced by the electrical stimulation which are many orders of magnitude larger than underlying brain activity. Approach: The aim of this study is to investigate the utility of MEG to gain insight into the regions of the brain most strongly influenced by tVNS and how variation of the stimulation parameters can affect this response in healthy participants. Main Results: We have successfully demonstrated that MEG can be used to measure brain response to tVNS. We have also shown that varying the stimulation frequency can lead to a difference in brain response, with the brain also responding in different anatomical regions depending on the frequency. Significance: The main contribution of this paper is to demonstrate the feasibility of simultaneous pulsed tVNS and MEG recording, allowing direct investigation of the changes in brain activity that result from different stimulation parameters. This may lead to the development of customised therapeutic approaches for the targeted treatment of different conditions.

Recent advances in the diagnosis and management of cluster headache

Cluster headache, a primary headache disorder, consists of short (15-180 minutes), frequent (up to eight a day), unilateral attacks of facial pain with associated ipsilateral autonomic features and restlessness. The attacks are suspected to be one of the most painful human experiences, and the disorder is associated with a high rate of suicidal ideation. Proper diagnosis is key, as some of the most effective treatments, such as high flow oxygen gas, are rarely used in other headache disorders. Yet diagnostic delay is typically years for this disorder, as it is often confused with migraine and trigeminal neuralgia, and secondary causes may be overlooked. This review covers the clinical, pathophysiologic, and therapeutic features of cluster headache. Recent updates in diagnosis include the redefinition of chronic cluster headache (remission periods lasting less than three months instead of the previous one month), and recent advances in management include new treatments for episodic cluster headache (galcanezumab and non-invasive vagus nerve stimulation).

Effects of acute and preventive therapies for episodic and chronic cluster headache: A scoping review of the literature

BACKGROUND

Cluster headache is the most common primary headache disorder of the trigeminal autonomic cephalalgias, and it is highly disabling.

OBJECTIVE

We undertake a scoping review to characterize therapies to prevent and acutely treat cluster headache, characterize trial methodology utilized in studies, and recommend future trial "good practices." We also assess homogeneity of studies and feasibility for future network meta-analyses (NMAs) to compare acute and preventive treatments for cluster headache.

METHODS

A priori protocol for this scoping review was registered and available on Open Science Forum. We sought studies that enrolled adult patients with cluster headache as identified by accepted diagnostic criteria. Both randomized controlled trials (RCTs) and observational studies (with a control group) were included. The interventions of interest were medications, procedures, devices, surgeries, and behavioral/psychological interventions, whereas comparators of interest were placebo, sham, or other active treatments. Outcomes were predefined; however, we did not exclude studies lacking these outcomes. A systemic search was conducted in Ovid Medline, Embase, and Cochrane. We performed a targeted search for conference abstracts from journals prominent in the field.

RESULTS

We identified 56 studies: 45 RCTs, four studies only available in clinical trial registries, and seven observational studies. Of the 45 RCTs, 20 focused on acute therapies and 25 on preventive therapies. Overall, we determined that it is feasible to pursue a NMA for acute therapy focusing on 15 or 30-min headache reduction for acute trials, as we identified 11 trials in the combined population of patients with either episodic or chronic cluster headache (2 trials in populations with chronic cluster headache were also found). For preventive therapy of cluster headache, we identified trials with common outcomes that may be considered for NMA, however, as these trials had differences in treatment effect modifiers that could not be corrected, NMAs appear infeasible for this indication. We identified new studies looking at noninvasive vagal nerve stimulation, sphenopalatine ganglion stimulation, prednisone, and oxygen published since the most recent systematic review in the field, although these acute treatments were previously identified as effective. However, for calcitonin gene-related peptide (CGRP) monoclonal antibodies, galcanezumab demonstrated effectiveness in episodic cluster headache, but a lack of effectiveness in chronic cluster headache, and fremanezumab was not effective for episodic nor chronic cluster headache. This finding highlights that CGRP monoclonal antibodies may not show a class effect in cluster headache prevention and need to be considered individually.

CONCLUSIONS

We describe the treatment landscape of cluster headache for both acute and preventive treatments. Last, we present the NMAs we will undertake in acute therapies of cluster headache.

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.

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).

Diagnostic protocols and newer treatment modalities for cluster headache

Cluster Headaches are one of the most arguably severe forms of primary headache syndrome that affects humans. Although it is relatively uncommon, it has a significant impact on the quality of life. It is a multifactorial disease that has risk factors ranging from seasonal changes, lifestyle habits to genetics. It occurs in 2 forms- Episodic and Chronic, each having its well-defined Diagnostic Criteria. Moreover, Cluster Headache has an exhaustive list of options for both Preventive and Abortive treatment. This article focuses on Cluster Headache, its pathophysiology, risk factors, differentials, and its diverse treatment modalities. In this study, an all-language literature search was conducted on Medline, Cochrane, Embase, and Google Scholar till October 2021. The following search strings and Medical Subject Headings (MeSH) terms were used: "Cluster Headache," "Triptans," "Neuromodulation," and "Migraine." We explored the literature on Cluster Headache for its epidemiology, pathophysiology, the role of various genes and how they bring about the disease as well as its episodic and chronic variants, and treatment options. Although we have a wide variety of options for Preventive and Abortive therapy, newer more effective pharmacological and non-pharmacological interventions are being developed, and must be integrated into new treatment protocols.

Noninvasive neuromodulation of the prefrontal cortex in mental health disorders

More than any other brain region, the prefrontal cortex (PFC) gives rise to the singularity of human experience. It is therefore frequently implicated in the most distinctly human of all disorders, those of mental health. Noninvasive neuromodulation, including electroconvulsive therapy (ECT), repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS) among others, can-unlike pharmacotherapy-directly target the PFC and its neural circuits. Direct targeting enables significantly greater on-target therapeutic effects compared with off-target adverse effects. In contrast to invasive neuromodulation approaches, such as deep-brain stimulation (DBS), noninvasive neuromodulation can reversibly modulate neural activity from outside the scalp. This combination of direct targeting and reversibility enables noninvasive neuromodulation to iteratively change activity in the PFC and its neural circuits to reveal causal mechanisms of both disease processes and healthy function. When coupled with neuronavigation and neurophysiological readouts, noninvasive neuromodulation holds promise for personalizing PFC neuromodulation to relieve symptoms of mental health disorders by optimizing the function of the PFC and its neural circuits. ClinicalTrials.gov Identifier: NCT03191058.

Neurostimulation Treatment in Chronic Cluster Headache-a Narrative Review

PURPOSE OF REVIEW

In this narrative review, the current literature on neurostimulation methods in the treatment of chronic cluster headache is evaluated. These neurostimulation methods include deep brain stimulation, vagus nerve stimulation, greater occipital nerve stimulation, sphenopalatine ganglion stimulation, transcranial magnetic stimulation, transcranial direct current stimulation, supraorbital nerve stimulation, and cervical spinal cord stimulation.

RECENT FINDINGS

Altogether, only nVNS and SPG stimulation are supported by at least one positive sham-controlled clinical trial for preventive and acute attack (only SPG stimulation) treatment. Other clinical trials either did not control at all or controlled by differences in the stimulation technique itself but not by a sham-control. Case series report higher responder rates. The evidence for these neurostimulation methods in the treatment of chronic cluster headache is poor and in part contradictive. However, except deep brain stimulation, tolerability and safety of these methods are good so that in refractory situations application might be justified in individual cases.

gammaCore for Cluster Headaches: A NICE Medical Technologies Guidance

Cluster headaches are excruciating attacks of pain that can last between 15 min and 3 h. Cluster headaches can be episodic, where patients have long pain-free intervals between attacks, or chronic, where they do not. As part of the Medical Technologies Evaluation Programme, the UK National Institute for Health and Care Excellence (NICE) considered the clinical effectiveness and cost impact of gammaCore (electroCore), a handheld, patient-controlled device used to treat and prevent cluster headache. gammaCore is a non-invasive vagus nerve stimulator, the aim of which is to modify pain signals by stimulating the vagus nerve through the skin of the neck. Evidence suggests that gammaCore reduces the intensity and frequency of cluster headaches and that the addition of gammaCore to standard care is cost saving. Therefore, the guidance published by NICE in December 2019 recommends routine adoption of gammaCore into the UK national health service. However, the guidance noted that gammaCore does not work for everyone and recommended that treatment with gammaCore should stop after 3 months in patients whose symptoms do not improve.

Intranasal ketamine for acute cluster headache attacks-Results from a proof-of-concept open-label trial

OBJECTIVE

To investigate the safety and efficacy of intranasal ketamine for the treatment of a single cluster headache (CH) attack.

BACKGROUND

Acute treatment options for patients with CH who have an insufficient response to oxygen and triptans are limited. Intranasal ketamine has anecdotally been successful in treating a CH attack.

METHODS

We conducted an open-label pilot study enrolling 23 patients with chronic CH (International Classification of Headache Disorders, 3rd edition), and of these, 20 patients treated a single CH attack with intranasal ketamine. Under in-hospital observation, patients received 15 mg of intranasal ketamine every 6 min a maximum of five times. The primary endpoint was a 50% reduction in pain intensity within 15 min after initiating treatment.

RESULTS

The primary endpoint was not met; 15 min after the first ketamine administration, the mean reduction in pain intensity was 1.1 (95% confidence interval [CI]: -0.6 to 2.7, p = 0.188) on the numeric rating scale (NRS), equivalent to a 15% reduction in pain intensity. However, 30 min after the first application, the pain intensity was reduced by 59% on an 11-point NRS (mean difference: 4.3, 95% CI: 2.4-6.2, p < 0.001, N = 16) and 11 out of 16 (69%) scored 4 or below on the NRS. Four patients received rescue medication 15 min after the first ketamine application and were therefore excluded from the analysis at 30 min. Half of the patients preferred ketamine to oxygen and/or sumatriptan injection. No serious adverse events were identified during the trial.

CONCLUSION

Intranasal ketamine may be an effective acute treatment for CH at 30 min but should be tested in a larger controlled design. Patients and physicians should be conscious of the abuse potential of ketamine.

Peripheral Nerve Stimulation for Treatment of Headaches: An Evidence-Based Review

Headaches are one of the most common medical complaints worldwide, and treatment is often made difficult because of misclassification. Peripheral nerve stimulation has emerged as a novel treatment for the treatment of intractable headaches in recent years. While high-quality evidence does exist regarding its use, efficacy is generally limited to specific nerves and headache types. While much research remains to bring this technology to the mainstream, clinicians are increasingly able to provide safe yet efficacious pain control.

Functional anatomy of the vagus system - Emphasis on the somato-visceral interface

Due to its pivotal role in autonomic networks, the vagus attracts continuous interest from both basic scientists and clinicians. In particular, recent advances in vagus nerve stimulation strategies and their application to pathological conditions beyond epilepsy provide a good opportunity to recall basic features of vagal peripheral and central anatomy. In addition to the "classical" vagal brainstem nuclei, i.e., dorsal motor nucleus, nucleus ambiguus and nucleus tractus solitarii, the spinal trigeminal and paratrigeminal nuclei come into play as targets of vagal afferents. On the other hand, the nucleus of the solitary tract receives and integrates not only visceral but also somatic afferents. Thus, the vagus system participates significantly in what may be defined as "somato-visceral interface".

tVNS in the management of headache and pain

First clinical observations of the therapeutic effect of vagus nerve stimulation were of patients who were treated for refractory epilepsy with a fully implanted vagus nerve stimulator, who also reported an improvement of their migraine and cluster headache. With the development of non-invasive vagus nerve stimulation, first clinical studies concerning a possible therapeutic effect in migraine and cluster headache were performed. In a controlled study, transcutaneous cervical vagus nerve stimulation (tcVNS) showed a significant but limited effect in acute treatment of a migraine attack. There was no significant prophylactic effect in episodic migraine. Concerning cluster headache, there was a clear beneficial effect in the prophylaxis of chronic cluster headache and in the attack treatment in episodic cluster headache. There are fewer studies in the literature on the effect of transcutaneous auricular vagus nerve stimulation (taVNS), with a partial overlap with studies on electrical ear acupuncture. In a small controlled clinical trial, there was a significant effect of taVNS in the prevention of chronic migraine. In less defined clinical studies, there were some positive signs that the method may be beneficial in chronic back pain and in unspecific gastro-intestinal pain in adolescents. Based on the available evidence, it is probable that vagus nerve stimulation can have a clinically meaningful influence on pain syndromes, but there are still several questions (e.g. frequency of the stimulation; duration of the stimulation; differential effects of auricular vagus stimulation and cervical vagus stimulation) to answer before vagus stimulation can be used widely in the clinic.

Regional cerebral blood flow as predictor of response to occipital nerve block in cluster headache

Background

Cluster headache is an excruciating disorder with no cure. Greater occipital nerve blockades can transiently suppress attacks in approximately 50% of patients, however, its mechanism of action remains uncertain, and there are no reliable predictors of treatment response. To address this, we investigated the effect of occipital nerve blockade on regional cerebral blood flow (rCBF), an index of brain activity, and differences between treatment responders and non-responders. Finally, we compared baseline perfusion maps from patients to a matched group of healthy controls.

Methods

21 male, treatment-naive patients were recruited while in a cluster headache bout. During a pain-free phase between headaches, patients underwent pseudo-continuous arterial spin labelled MRI assessments to provide quantitative indices of rCBF. MRIs were performed prior to and 7-to-21 days following treatment. Patients also recorded the frequency of their headache attacks in a daily paper diary. Neuropsychological assessment including anxiety, depression and quality of life measures was performed in a first, scanning free session for each patient.

Results

Following treatment, patients demonstrated relative rCBF reductions in posterior temporal gyrus, cerebellum and caudate, and rCBF increases in occipital cortex. Responders demonstrated relative rCBF increases, compared to non-responders, in medial prefrontal cortex and lateral occipital cortex at baseline, but relative reductions in cingulate and middle temporal cortices. rCBF was increased in patients compared to healthy controls in cerebellum and hippocampus, but reduced in orbitofrontal cortex, insula and middle temporal gyrus.

Conclusions

We provide new mechanistic insights regarding the aetiology of cluster headache, the mechanisms of action of occipital nerve blockades and potential predictors of treatment response. Future investigation should determine whether observed effects are reproducible and extend to other headache disorders.