Migraine pathophysiology: anatomy of the trigeminovascular pathway and associated neurological symptoms, CSD, sensitization and modulation of pain

Sensory Processing Difficulties Correlate With Disease Severity and Quality of Life Among Children With Migraine

Introduction: Headaches are common among children and about 80% of children reporting them. Migraine and tension type headaches are the most common primary headaches in children and the prevalence of migraine is about 8%. Accompanying sensory symptoms are common before, during and after migraine attacks. They may be a part of a wider symptom constellation called sensory processing disorder or difficulties (SPD). This includes both hyper or hypo sensitivity to sensations. However, the literature regarding sensory processing symptoms of children and youth with headaches as well as its interaction with child's emotional aspects and quality of life is scarce. Materials and Methods: One hundred and thirty-four children between the ages of 8 and 12 participated in this study. Fifty-four children (22 boys and 32 girls) with episodic migraine were prospectively recruited from pediatric neurological clinics during the years 2014-2017. The control group included 80 healthy children. Both groups completed a health and demographic questionnaire, headache assessment including Ped-MIDAS, Short Sensory Profile, State-Trait Anxiety Inventory (STAI) for children, and the Pediatric Quality of Life Inventory. Results: Children with migraine showed significantly higher prevalence of sensory processing difficulties and lower quality of life compared to healthy controls. Among children with migraine, sensory processing difficulties significantly correlated with lower quality of life. Headache-related disability and sensory processing difficulties predicted quality of life. Conclusion: The possible relationship between migraine and sensory processing disorder or difficulties stresses the need to screen for sensory processing difficulties among children with migraine and when found-refer to their impacts on children's daily function and quality of life.

The Efficacy of Shinbaro for the Preventive Treatment of Migraine: A Pilot Study

OBJECTIVE

To investigate the therapeutic potential and efficacy of Shinbaro, an herbal medication for inflammatory diseases and bone disorders, as a preventive treatment of migraine.

METHODS

In this prospective, interventional, single-arm, pre-post study, 37 migraine patients took 600mg bid of Shinbaro for 12 weeks. At 4-week intervals, the migraine frequency and the rescue medications frequency were measured from each patient's headache diary. The modified Migraine Disability Assessment (MIDAS) questionnaires to assess migraine associated disabilities were also completed at each visit. The serum calcitonin gene-related peptide (CGRP) concentrations before and after 12 weeks of Shinbaro administration were compared.

RESULTS

The monthly migraine frequency was significantly reduced from 20.5 days at baseline to 16.4 days at week 12 (P =0.003), and 22% of the participants showed ≥ 50% reduction. The frequency reduction was observed by week 4 (P =0.035) and continuously occurred through week 8 (P =0.001) and week 12 (P =0.003). The rescue medications frequency also decreased significantly from 17.4 days at baseline to 13.2 days at week 12 (P =0.035). Lastly, the serum CGRP concentration dropped from 434.6 pg/mL at baseline to 371.4 pg/mL at week 12, which was statistically significant (P <0.001).

CONCLUSIONS

Shinbaro demonstrated prophylactic effects in migraine patients, significantly reducing their mean migraine frequency, rescue medications frequency, and the serum CGRP concentration after 12 weeks of treatment. This study is registered in Clinical Research Information Service, Seoul National University Hospital Clinical Research Institute (IRB No. 1604-138-758).

Corneal subbasal nerve plexus changes in patients with episodic migraine: an in vivo confocal microscopy study

Background and purpose: It has been generally thought that activation and sensitization of the trigeminovascular system may contribute to the pathogenesis of migraine. Nevertheless, there is little evidence on abnormalities in peripheral trigeminal afferent nerves from humans in vivo. Alterations of corneal nerves from the ophthalmic branch of the trigeminal nerve may support the notion that trigeminal afferent nerves are involved in migraine pathophysiology. The aim of the present study was to investigate the structural changes in corneal subbasal nerve plexus in patients with episodic migraine (EM) with in vivo confocal microscope (IVCM).

Methods: In this cross-sectional observational study, 10 EM patients and 10 age- and sex-matched healthy controls were included. Analysis of IVCM images with Image J software was performed to quantify the changes in the corneal subbasal nerve plexus.

Results: EM patients showed an increase in nerve fiber length (25.0±2.65 vs 22.3±2.41 mm/mm², p=0.047) and nerve fiber density (36.3±7.29 vs 30.5±6.19 fibers/mm², p=0.104) as compared with normal controls, but this difference was not statistically significant. Nerve branching and tortuosity were significantly increased in the EM subjects compared to the normal subjects (91.3±13.8 vs 75.0±14.2 branches/mm², p=0.030 and 2.30±0.46 versus 1.63±0.52, p=0.011, respectively). In addition, nerve sprouts and increased number of Langerhans cells were observed in the EM patients.

Conclusion: The morphologic changes of corneal subbasal nerve plexus and Langerhans cell aggregation suggest the presence of nerve regeneration and inflammation in EM. Furthermore, the alterations of corneal nerves from the ophthalmic branch of the trigeminal nerve offer support for the hypothesis that the peripheral trigeminal system may be involved in the pathogenesis of migraine.

Meningeal Mast Cells Contribute to ATP-Induced Nociceptive Firing in Trigeminal Nerve Terminals: Direct and Indirect Purinergic Mechanisms Triggering Migraine Pain

Peripheral mechanisms of primary headaches such as a migraine remain unclear. Meningeal afferents surrounded by multiple mast cells have been suggested as a major source of migraine pain. Extracellular ATP released during migraine attacks is a likely candidate for activating meningeal afferents via neuronal P2X receptors. Recently, we showed that ATP also increased degranulation of resident meningeal mast cells (Nurkhametova et al., 2019). However, the contribution of ATP-induced mast cell degranulation in aggravating the migraine pain remains unknown. Here we explored the role of meningeal mast cells in the pro-nociceptive effects of extracellular ATP. The impact of mast cells on ATP mediated activation of peripheral branches of trigeminal nerves was measured electrophysiologically in the dura mater of adult wild type (WT) or mast cell deficient mice. We found that a spontaneous spiking activity in the meningeal afferents, at baseline level, did not differ in two groups. However, in WT mice, meningeal application of ATP dramatically (24.6-fold) increased nociceptive firing, peaking at frequencies around 10 Hz. In contrast, in mast cell deficient animals, ATP-induced excitation was significantly weaker (3.5-fold). Application of serotonin to meninges in WT induced strong spiking. Moreover, in WT mice, the 5-HT3 antagonist MDL-7222 inhibited not only serotonin but also the ATP induced nociceptive firing. Our data suggest that extracellular ATP activates nociceptive firing in meningeal trigeminal afferents via amplified degranulation of resident mast cells in addition to direct excitatory action on the nerve terminals. This highlights the importance of mast cell degranulation via extracellular ATP, in aggravating the migraine pain.

Coping Strategies in Migraine without Aura: A Cross-Sectional Study

Background

In the context of a causal relationship between stress and migraine, coping strategies are aimed at managing stressful life events and reducing the distressing emotions connected to them.

Methods

Sixty-one consecutive patients with migraine without aura (MwoA) and sixty-one healthy controls (HCs) completed three self-report questionnaires assessing a broad range of coping (cognitive and behavioural) strategies: the Coping Orientation to Problems Experienced (COPE), the Coping Inventory for Stressful Situation (CISS), and the Proactive Coping Inventory (PCI). Moreover, the Perceived Stress Scale (PSS), a scale measuring self-perception of stress, global cognitive functioning, depressive symptoms, apathy, state, and trait anxiety, was administered to all participants.

Results

No significant difference was found on the scales and subscales of PCI and CISS as well as in the PSS between MwoA patients and HCs. However, the two groups showed different scores in the subscale “turning to religion” of COPE (22.08 ± 5.19 in migraineurs vs. 24.70 ± 4.44 in HCs, p = 0.003). A significant negative correlation of the turning to religion score with the HIT-6 score was found.

Conclusions

The present study revealed that MwoA patients show a significantly reduced use of the “turning to religion” approach, an emotion-focused coping strategy. Although migraine patients appeared to be less oriented to transcendent (that means a reduced utilization of an adaptive coping strategy), they did not perceive daily living as more stressful than HCs. Finally, the reduced utilization of the “turning to religion” coping strategy is associated with a great impact of migraine on ability to function on the job or at school, at home, and in social situations in migraine patients.

Advanced visual network and cerebellar hyperresponsiveness to trigeminal nociception in migraine with aura

Background

Despite the growing body of advanced studies investigating the neuronal correlates of pain processing in patients with migraine without aura (MwoA), only few similar studies have been conducted in patients with migraine with aura (MwA). Therefore, we aimed to explore the functional brain response to trigeminal noxious heat stimulation in patients with MwA.

Methods

Seventeen patients with MwA and 15 age- and sex-matched healthy controls (HC) underwent whole-brain blood oxygen level–dependent (BOLD) fMRI during trigeminal noxious heat stimulation. To examine the specificity of any observed differences between patients with MwA and HC, the functional response of neural pathways to trigeminal noxious heat stimulation in patients with MwA was compared with 18 patients with MwoA. Secondary analyses investigated the correlations between BOLD signal changes and clinical parameters of migraine severity.

Results

We observed a robust cortical and subcortical pattern of BOLD response to trigeminal noxious heat stimulation across all participants. Patients with MwA showed a significantly increased activity in higher cortical areas known to be part of a distributed network involved in advanced visual processing, including lingual gyrus, inferior parietal lobule, inferior frontal gyrus and medial frontal gyrus. Moreover, a significantly greater cerebellar activation was observed in patients with MwA when compared with both patients with MwA and HC. Interestingly, no correlations were found between migraine severity parameters and magnitude of BOLD response in patients with MwA.

Conclusion

Our findings, characterized by abnormal visual pathway response to trigeminal noxious heat stimulation, support the role of a functional integration between visual and trigeminal pain networks in the pathophysiological mechanisms underlying migraine with aura. Moreover, they expand the concept of “neurolimbic-pain network” as a model of MwoA including both limbic dysfunction and cortical dys-excitability. Indeed, we suggest a model of “neurolimbic-visual-pain network” in MwA patients, characterized by dysfunctional correlations between pain-modulating circuits not only with the cortical limbic areas but with advanced visual areas as well. Furthermore, the abnormal cerebellar response to trigeminal noxious heat stimulation may suggest a dysfunctional cerebellar inhibitory control on thalamic sensory gating, impinging on the advanced visual processing cortical areas in patients with MwA.

Electronic supplementary material

The online version of this article (10.1186/s10194-019-1002-3) contains supplementary material, which is available to authorized users.

CGRP and the Trigeminal System in Migraine

OBJECTIVE

The goal of this narrative review is to provide an overview of migraine pathophysiology, with an emphasis on the role of calcitonin gene-related peptide (CGRP) within the context of the trigeminovascular system.

BACKGROUND

Migraine is a prevalent and disabling neurological disease that is characterized in part by intense, throbbing, and unilateral headaches. Despite recent advances in understanding its pathophysiology, migraine still represents an unmet medical need, as it is often underrecognized and undertreated. Although CGRP has been known to play a pivotal role in migraine for the last 2 decades, this has now received more interest spurred by the early clinical successes of drugs that block CGRP signaling in the trigeminovascular system.

DESIGN

This narrative review presents an update on the role of CGRP within the trigeminovascular system. PubMed searches were used to find recent (ie, 2016 to November 2018) published articles presenting new study results. Review articles are also included not as primary references but to bring these to the attention of the reader. Original research is referenced in describing the core of the narrative, and review articles are used to support ancillary points.

RESULTS

The trigeminal ganglion neurons provide the connection between the periphery, stemming from the interface between the primary afferent fibers of the trigeminal ganglion and the meningeal vasculature and the central terminals in the trigeminal nucleus caudalis. The neuropeptide CGRP is abundant in trigeminal ganglion neurons, and is released from the peripheral nerve and central nerve terminals as well as being secreted within the trigeminal ganglion. Release of CGRP from the peripheral terminals initiates a cascade of events that include increased synthesis of nitric oxide and sensitization of the trigeminal nerves. Secreted CGRP in the trigeminal ganglion interacts with adjacent neurons and satellite glial cells to perpetuate peripheral sensitization, and can drive central sensitization of the second-order neurons. A shift in central sensitization from activity-dependent to activity-independent central sensitization may indicate a mechanism driving the progression of episodic migraine to chronic migraine. The pathophysiology of cluster headache is much more obscure than that of migraine, but emerging evidence suggests that it may also involve hypersensitivity of the trigeminovascular system. Ongoing clinical studies with therapies targeted at CGRP will provide additional, valuable insights into the pathophysiology of this disorder.

CONCLUSIONS

CGRP plays an essential role in the pathophysiology of migraine. Treatments that interfere with the functioning of CGRP in the peripheral trigeminal system are effective against migraine. Blocking sensitization of the trigeminal nerve by attenuating CGRP activity in the periphery may be sufficient to block a migraine attack. Additionally, the potential exists that this therapeutic strategy may also alleviate cluster headache as well.

Phytomedicines in the Treatment of Migraine

Migraine is a disabling neurovascular disorder with few targeted, tolerable and effective treatments. Phytomedicines, or plant-based medicinal formulations, hold great promise in the identification of novel therapeutic targets in migraine. Many patients also turn toward herbal and plant-based therapies for the treatment of their migraines as clinical and preclinical evidence of efficacy increases. Patients seek effective and tolerable treatments instead of or in addition to current conventional pharmacologic therapies. We review some phytomedicines potentially useful for migraine treatment-feverfew (Tanacetum parthenium), butterbur (Petasites hybridus), marijuana (Cannabis spp.), Saint John's Wort (Hypericum perforatum) and the Damask rose (Rosa × damascena)-with respect to their mechanisms of action and evidence for treatment of migraine. The evidence for feverfew is mixed; butterbur is effective with potential risks of hepatotoxicity related to preparation; marijuana has not been shown to be effective in migraine treatment, and data are scant; Saint John's Wort shows relevant physiological activity but is a hepatic enzyme inducer and lacks clinical studies for this purpose; the Damask rose when used in topical preparations did not show efficacy in one clinical trial. Other plant preparations have been considered for migraine treatment but most without blinded randomized, placebo-controlled trial evidence.

The effect of orofacial complete Freund's adjuvant treatment on the expression of migraine-related molecules

Background

Migraine is a neurovascular primary headache disorder, which causes significant socioeconomic problems worldwide. The pathomechanism of disease is enigmatic, but activation of the trigeminovascular system (TS) appears to be essential during the attack. Migraine research of recent years has focused on neuropeptides, such as calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide 1–38 (PACAP1–38) as potential pathogenic factors and possible therapeutic offensives. The goal of present study was to investigate the simultaneous expression of CGRP and precursor of PACAP1–38 (preproPACAP) in the central region of the TS in a time-dependent manner following TS activation in rats.

Methods

The right whisker pad of rats was injected with 50 μl Complete Freund’s Adjuvant (CFA) or saline. A mechanical allodynia test was performed with von Frey filaments before and after treatment. Transcardial perfusion of the animals was initiated 24, 48, 72 and 120 h after injection, followed by the dissection of the nucleus trigeminus caudalis (TNC). After preparation, the samples were stored at − 80 °C until further use. The relative optical density of CGRP and preproPACAP was analyzed by Western blot. One-way ANOVA and Kruskal-Wallis followed by Tukey post hoc test were used to evaluate the data. Regression analysis was applied to explore the correlation between neuropeptides expression and hyperalgesia.

Results

Orofacial CFA injection resulted in significant CGRP and preproPACAP release in the TNC 24, 48, 72 and 120 h after the treatment. The level of neuropeptides reached its maximum at 72 h after CFA injection, corresponding to the peak of facial allodynia. Negative, linear correlation was detected between the expression level of neuropeptides and value of mechanonociceptive threshold.

Conclusion

This is the first study which suggests that the expression of CGRP and preproPACAP simultaneously increases in the central region of activated TS and it influences the formation of mechanical hyperalgesia. Our results contribute to a better understanding of migraine pathogenesis and thereby to the development of more effective therapeutic approaches.

Evaluation of Electroencephalogram Using Exact Low-Resolution Electromagnetic Tomography During Photic Driving Response in Patients with Migraine

BACKGROUND

Photophobia is a common feature of migraine, which may involve abnormal cortical information processing. In electroencephalograms (EEG), photic driving is known as a reaction to visual stimulation. Both photophobia and photic driving response are present during light stimulation. We hypothesized that cortical response to photic stimulation would differ between migraine patients with and without aura.

METHODS

We recruited 50 migraine patients (migraine with aura [MWA] = 21; migraine without aura [MWOA] = 29). Spontaneous eyes-closed resting EEG from 20 electrodes on the scalp during the interictal phase was recorded. After recording, each photic stimulation was separately selected. We analyzed EEG by fast Fourier transform and observed the spectrum frequency peaks and topographies in response to photic stimulation. Exact low-resolution electromagnetic tomography (eLORETA) was used to compute the 3-dimensional intracerebral distribution of EEG activity.

RESULTS

Photic stimulation at frequencies 5, 8, 15, and 20 Hz showed significant differences between migraine patients with and without aura. MWOA patients consistently had a stronger response to photic stimulation than MWA patients. In all patients, the differential response was located in the visual cortex, except for the stimulation at 20 Hz, where the difference at subharmonic 10 Hz was located in the parietal cortex (Brodmann Area 7).

CONCLUSION

We confirmed high incidences of photic hypersensitivity and photic driving responses in migraine patients. We suggest that repeated occurrences of cortical spreading depression in MWA may suppress cortical function, thus contributing to a weaker visual cortical response to photic stimulation in MWA patients compared with MWOA patients.

Non-invasive Brain Stimulation in Pediatric Migraine: A Perspective From Evidence in Adult Migraine

Pediatric migraine remains still a challenge for the headache specialists as concerns both diagnostic and therapeutic aspects. The less ability of children to describe the exact features of their migraines and the lack of reliable biomarker for migraine contribute to complicate the diagnostic process. Therefore, there's need for new effective tools for supporting diagnostic and therapeutic approach in children with migraine. Recently, promising results have been obtained in adult headache by means of application of neurostimulation techniques both for investigating pathophysiological mechanisms and also for therapeutical applications. Non-invasive brain stimulation (NIBS) techniques like transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) indeed proved to be generally safe and showing also some evidence of efficacy particularly for the symptomatic treatment. On such basis, in the last years increasing interest is rising in scientific pediatric community to evaluate the potential of such approaches for treatment pediatric headaches, particularly in migraine, even if the evidence provided is still very poor. Here we present a perspective for application of TMS and tDCS technique in children migraine principally based on evidence coming by studies in adults.

TRP Channels and Migraine: Recent Developments and New Therapeutic Opportunities

Migraine is the second-most disabling disease worldwide, and the second most common neurological disorder. Attacks can last many hours or days, and consist of multiple symptoms including headache, nausea, vomiting, hypersensitivity to stimuli such as light and sound, and in some cases, an aura is present. Mechanisms contributing to migraine are still poorly understood. However, transient receptor potential (TRP) channels have been repeatedly linked to the disorder, including TRPV1, TRPV4, TRPM8, and TRPA1, based on their activation by pathological stimuli related to attacks, or their modulation by drugs/natural products known to be efficacious for migraine. This review will provide a brief overview of migraine, including current therapeutics and the link to calcitonin gene-related peptide (CGRP), a neuropeptide strongly implicated in migraine pathophysiology. Discussion will then focus on recent developments in preclinical and clinical studies that implicate TRP channels in migraine pathophysiology or in the efficacy of therapeutics. Given the use of onabotulinum toxin A (BoNTA) to treat chronic migraine, and its poorly understood mechanism, this review will also cover possible contributions of TRP channels to BoNTA efficacy. Discussion will conclude with remaining questions that require future work to more fully evaluate TRP channels as novel therapeutic targets for migraine.

Bidirectional association between migraine and fibromyalgia: retrospective cohort analyses of two populations

OBJECTIVE

Fibromyalgia (FM) and migraine are common pain disorders that tend to coexist. This study determined whether these two conditions exhibited any mutual influences.

SETTING

Cohort study.

PARTICIPANTS

A retrospective, longitudinal cohort study was conducted using data obtained from a nationwide healthcare database. This study had two arms. Arm 1 comprised 33 216 patients with FM and arm 2 consisted of 7420 patients with migraine; all of these patients were diagnosed between 2000 and 2010. Using the aforementioned database, control subjects who had neither FM nor migraine and were matched with the FM and migraine patients by sex, age and index date of diagnosis were recruited. Each control cohort was four times the size of the corresponding study cohort. Follow-up for the control and study cohorts was conducted until the end of 2011.

RESULTS

The incidence rates of FM and migraine were calculated in arms 1 and 2, respectively. The overall incidence of migraine was greater in the FM cohort than in the corresponding control cohort (4.39 vs 2.07 per 1000 person-years (PY)); crude HR=2.12, 95% CI=1.96 to 2.30; adjusted HR (aHR)=1.89, 95% CI=1.75 to 2.05). After adjustment for sex, age and comorbidities, the overall incidence of FM in the migraine cohort was 1.57 times greater than that in the corresponding control cohort (7.01 vs 4.49 per 1000 PY; aHR=1.52, 95% CI=1.39 to 1.65).

CONCLUSIONS

The present study revealed a bidirectional link between FM and migraine.

Targeting the central projection of the dural trigeminovascular system for migraine prophylaxis

Migraine abortives likely target both peripheral-dural and central trigeminovascular mechanisms in mediating their therapeutic effects. However, in preclinical assays, many migraine preventives have little success at inhibiting similar trigeminovascular-mediated peripheral changes within the dural microenvironment. In addition, their effects on central trigeminovascular neuronal responses are largely unknown. Using a validated preclinical model of acute dural-intracranial (migraine-like) head pain, using Sprague Dawley rats, we tested whether migraine preventives suppress ongoing firing of central trigeminocervical neurons, and evoked responses to cranial neurovascular activation. Flunarizine, sodium valproate, propranolol, and amitriptyline, all dose-dependently inhibited ongoing spontaneous firing of dural trigeminovascular neurons, and differentially affected neuronal responses to intracranial-dural and extracranial-cutaneous somatosensory stimulation. Lamotrigine, only effective in the treatment of migraine aura, did not affect responses. These data provide a mechanistic rationale for the clinical effects of migraine preventives in the treatment of migraine, via the modulation of dural-responsive central trigeminovascular neurons. Also, given their limited effect on peripheral dural vasdilatory responses, these data also suggest that migraine preventives specifically target central, rather than peripheral, components of trigeminal neurovascular mechanisms involved in migraine pathophysiology, to mediate their preventive action. Finally, these data further validate this preclinical model of central trigeminovascular activation to screen migraine preventives.

Neurovascular mechanisms of migraine and cluster headache

Vascular theories of migraine and cluster headache have dominated for many years the pathobiological concept of these disorders. This view is supported by observations that trigeminal activation induces a vascular response and that several vasodilating molecules trigger acute attacks of migraine and cluster headache in susceptible individuals. Over the past 30 years, this rationale has been questioned as it became clear that the actions of some of these molecules, in particular, calcitonin gene-related peptide and pituitary adenylate cyclase-activating peptide, extend far beyond the vasoactive effects, as they possess the ability to modulate nociceptive neuronal activity in several key regions of the trigeminovascular system. These findings have shifted our understanding of these disorders to a primarily neuronal origin with the vascular manifestations being the consequence rather than the origin of trigeminal activation. Nevertheless, the neurovascular component, or coupling, seems to be far more complex than initially thought, being involved in several accompanying features. The review will discuss in detail the anatomical basis and the functional role of the neurovascular mechanisms relevant to migraine and cluster headache.

Chinese herbal medicine for headache: A systematic review and meta-analysis of high-quality randomized controlled trials

BACKGROUND

Chinese herbal medicines (CHMs) are widely used to relieve headache in Asia. However, it is uncertain whether there is robust evidence on the effects of CHMs for headache.

PURPOSE

To assess the effectiveness and safety of CHMs for headache using systematic review of high-quality randomized controlled trials (RCTs).

METHODS

Electronic search was conducted on six databases from inception to January 2018. We included the RCTs that met the requirement of at least 4 out of the 7 domains according to the Cochrane risk of bias tool.

RESULTS

Thirty RCTs with 3447 subjects were ultimately included for analysis and all trials were conducted in Asia. Meta-analysis showed that CHMs monotherapy were superior to placebo in reducing headache frequency [SMD -0.48 (95% CI -0.76, -0.20); p < 0.01], headache days [SMD -0.29 (95% CI -0.45, -0.13); p < 0.01], headache duration[SMD -0.58 (95% CI -0.81, -0.36); p < 0.01], headache intensity [SMD -0.42 (95% CI -0.62, -0.23); p < 0.01] and analgesic consumption [SMD -0.36 (95% CI -0.52, -0.21); p < 0.01] and improving clinical efficacy rate (p < 0.01). Similarly, CHMs monotherapy were superior to western conventional medicines (WCMs) in headache frequency [SMD -0.57 (95% CI -0.84, -0.29); p < 0.01], headache days (p < 0.01), analgesic consumption [SMD -1.63 (95% CI -1.98, -1.28); p < 0.01], headache intensity [SMD -0.81 (95% CI -1.06, -0.57); p < 0.01], and clinical efficacy rate [RR 1.24 (95% CI 1.18, 1.31); p < 0.01], except reducing headache duration (p > 0.05). CHMs adjunct therapy can improve clinical efficacy rate compared with WCMs alone [RR 1.15 (95% CI 1.09, 1.22); p < 0.01]. Meanwhile, CHMs had fewer adverse events than that of controls.

CONCLUSION

The findings supported, at least to an extent, the use of CHM for headache patients; however, we should treat the results cautiously because the clinical heterogeneity.

Non-Trigeminal Nociceptive Innervation of the Posterior Dura: Implications to Occipital Headache

Current understanding of the origin of occipital headache falls short of distinguishing between cause and effect. Most preclinical studies involving trigeminovascular neurons sample neurons that are responsive to stimulation of dural areas in the anterior 2/3 of the cranium and the periorbital skin. Hypothesizing that occipital headache may involve activation of meningeal nociceptors that innervate the posterior ⅓ of the dura, we sought to map the origin and course of meningeal nociceptors that innervate the posterior dura overlying the cerebellum. Using AAV-GFP tracing and single-unit recording techniques in male rats, we found that neurons in C2-C3 DRGs innervate the dura of the posterior fossa; that nearly half originate in DRG neurons containing CGRP and TRPV1; that nerve bundles traverse suboccipital muscles before entering the cranium through bony canals and large foramens; that central neurons receiving nociceptive information from the posterior dura are located in C2-C4 spinal cord and that their cutaneous and muscle receptive fields are found around the ears, occipital skin and neck muscles; and that administration of inflammatory mediators to their dural receptive field, sensitize their responses to stimulation of the posterior dura, peri-occipital skin and neck muscles. These findings lend rationale for the common practice of attempting to alleviate migraine headaches by targeting the greater and lesser occipital nerves with anesthetics. The findings also raise the possibility that such procedures may be more beneficial for alleviating occipital than non-occipital headaches and that occipital migraines may be associated more closely with cerebellar abnormalities than in non-occipital migraines.SIGNIFICANCE STATEMENT Occipital headaches are common in both migraine and non-migraine headaches. Historically, two distinct scenarios have been proposed for such headaches; the first suggests that the headaches are caused by spasm or tension of scalp, shoulders, and neck muscles inserted in the occipital region, whereas the second suggests that these headaches are initiated by activation of meningeal nociceptors. The current study shows that the posterior dura overlying the cerebellum is innervated by cervicovascular neurons in C2 DRG whose axons reach the posterior dura through multiple intracranial and extracranial pathways, and sensitization of central cervicovascular neurons from the posterior dura can result in hyper-responsiveness to stimulation of neck muscles. The findings suggest that the origin of occipital and frontal migraine may differ.

Neurobiology of Photophobia

BACKGROUND

Photophobia is commonly associated with migraine, meningitis, concussion, and a variety of ocular diseases. Advances in our ability to trace multiple brain pathways through which light information is processed have paved the way to a better understanding of the neurobiology of photophobia and the complexity of the symptoms triggered by light.

PURPOSE

The purpose of this review is to summarize recent anatomical and physiological studies on the neurobiology of photophobia with emphasis on migraine.

RECENT FINDINGS

Observations made in blind and seeing migraine patients, and in a variety of animal models, have led to the discovery of a novel retino-thalamo-cortical pathway that carries photic signal from melanopsinergic and nonmelanopsinergic retinal ganglion cells (RGCs) to thalamic neurons. Activity of these neurons is driven by migraine and their axonal projections convey signals about headache and light to multiple cortical areas involved in the generation of common migraine symptoms. Novel projections of RGCs into previously unidentified hypothalamic neurons that regulate parasympathetic and sympathetic functions have also been discovered. Finally, recent work has led to a novel understanding of color preference in migraine-type photophobia and of the roles played by the retina, thalamus, and cortex.

SUMMARY

The findings provide a neural substrate for understanding the complexity of aversion to light in patients with migraine and neuro-ophthalmologic other disorders.

Pharmacokinetics and pharmacodynamics of new acute treatments for migraine

INTRODUCTION

Recommended medications for the acute treatment of migraine encompass triptans, nonsteroidal anti-inflammatory drugs (NSAIDs), and analgesics. While it is true that triptans have been the first successful mechanism-driven treatment in the field, recently, new targets involved in migraine pathogenesis have emerged and new drug classes have been studied for migraine attack therapy. Areas covered: Pharmacodynamics and pharmacokinetics of the new acute treatments of migraine (i.e. ditans, gepants, and glutamate receptor antagonists), considering also marketed drugs in new formulations and administration routes. Expert opinion: Research on the administration routes of marketed drugs was performed in order to improve, in accordance with basic pharmacokinetics parameters, the speed of action of these medications. Similar to the triptans, the new acute treatments are migraine-specific medications, acting on the trigeminovascular system, albeit with different mechanisms. Although available data do not conclusively indicate the superiority of a class over the others, the pharmacodynamics explains the peculiar tolerability and safety profile of different drug classes emerging from clinical trials. Further studies are needed to investigate the possibility of combining different drug classes to optimize the clinical response and the potential role of the novel drugs in medication-overuse headache.

Potential Application of Optogenetic Stimulation in the Treatment of Pain and Migraine Headache: A Perspective from Animal Studies

Optogenetic manipulation is uniquely useful in unraveling the functional organization of neuronal circuits in the central nervous system by enabling reversible gain- or loss-of-function of discrete populations of neurons within restricted brain regions. This state-of-the-art technology can produce circuit-specific neuromodulation by overexpressing light-sensitive proteins (opsins) in particular cell types of interest. Here, we discuss the principle of optogenetic manipulation and its application in pain research using animal models, and we also discuss how to potentially use optogenetic stimulation in the treatment of migraine headache in the future.

Novel hypotheses emerging from GWAS in migraine?

Recent technical advances in genetics made large-scale genome-wide association studies (GWAS) in migraine feasible and have identified over 40 common DNA sequence variants that affect risk for migraine types. Most of the variants, which are all single nucleotide polymorphisms (SNPs), show robust association with migraine as evidenced by the fact that the vast majority replicate in subsequent independent studies. However, despite thorough bioinformatic efforts aimed at linking the migraine risk SNPs with genes and their molecular pathways, there remains quite some discussion as to how successful this endeavour has been, and their current practical use for the diagnosis and treatment of migraine patients. Although existing genetic information seems to favour involvement of vascular mechanisms, but also neuronal and other mechanisms such as metal ion homeostasis and neuronal migration, the complexity of the underlying genetic pathophysiology presents challenges to advancing genetic knowledge to clinical use. A major issue is to what extent one can rely on bioinformatics to pinpoint the actual disease genes, and from this the linked pathways. In this Commentary, we will provide an overview of findings from GWAS in migraine, current hypotheses of the disease pathways that emerged from these findings, and some of the major drawbacks of the approaches used to identify the genes and pathways. We argue that more functional research is urgently needed to turn the hypotheses that emerge from GWAS in migraine to clinically useful information.

Nitroglycerine triggers triptan-responsive cranial allodynia and trigeminal neuronal hypersensitivity

Cranial allodynia associated with spontaneous migraine is reported as either responsive to triptan treatment or to be predictive of lack of triptan efficacy. These conflicting results suggest that a single mechanism mediating the underlying neurophysiology of migraine symptoms is unlikely. The lack of a translational approach to study cranial allodynia reported in migraine patients is a limitation in dissecting potential mechanisms. Our objective was to study triptan-responsive cranial allodynia in migraine patients, and to develop an approach to studying its neural basis in the laboratory. Using nitroglycerine to trigger migraine attacks, we investigated whether cranial allodynia could be triggered experimentally, observing its response to treatment. Preclinically, we examined the cephalic response properties of central trigeminocervical neurons using extracellular recording techniques, determining changes to ongoing firing and somatosensory cranial-evoked sensitivity, in response to nitroglycerine followed by triptan treatment. Cranial allodynia was triggered alongside migraine-like headache in nearly half of subjects. Those who reported cranial allodynia accompanying their spontaneous migraine attacks were significantly more likely to have symptoms triggered than those that did not. Patients responded to treatment with aspirin or sumatriptan. Preclinically, nitroglycerine caused an increase in ongoing firing and hypersensitivity to intracranial-dural and extracranial-cutaneous (noxious and innocuous) somatosensory stimulation, reflecting signatures of central sensitization potentially mediating throbbing headache and cranial allodynia. These responses were aborted by a triptan. These data suggest that nitroglycerine can be used as an effective and reliable method to trigger cranial allodynia in subjects during evoked migraine, and the symptom is responsive to abortive triptan treatments. Preclinically, nitroglycerine activates the underlying neural mechanism of cephalic migraine symptoms, central sensitization, also predicting the clinical outcome to triptans. This supports a biological rationale that several mechanisms can mediate the underlying neurophysiology of migraine symptoms, with nitrergic-induced changes reflecting one that is relevant to spontaneous migraine in many migraineurs, whose symptoms of cranial allodynia are responsive to triptan treatment. This approach translates directly to responses in animals and is therefore a relevant platform to study migraine pathophysiology, and for use in migraine drug discovery.

Double-blind placebo-controlled randomized clinical trial of ginger ( Zingiber officinale Rosc.) addition in migraine acute treatment

BACKGROUND

Previous studies have demonstrated the analgesic effects of ginger in different conditions, but evidence about its efficacy in migraine treatment is scarce.

OBJECTIVE

This study aimed to evaluate the potential of ginger to improve acute migraine as an add-on strategy to standard treatment.

METHODS

A double-blind placebo-controlled randomized clinical trial in the emergency room of a general hospital was conducted. Patients who sought medical care at the time of migraine attack were enrolled in this study. Only adults with episodic migraine (one to six migraine attacks per month) with or without aura were included. Sixty participants were randomized into two groups in which they received 400 mg of ginger extract (5% active ingredient) or placebo (cellulose), in addition to an intravenous drug (100 mg of ketoprofen) to treat the migraine attack. Patients filled a headache diary before, 0.5 h, 1 h, 1.5 h and 2 h after the medication. Pain severity, functional status, migraine symptoms and treatment satisfaction were also recorded.

RESULTS

Patients treated with ginger showed significantly better clinical response after 1 h ( p = 0.04), 1.5 h ( p = 0.01) and 2 h ( p = 0.04). Furthermore, ginger treatment promoted reduction in pain and improvement on functional status at all times assessed.

CONCLUSIONS

The addition of ginger to non-steroidal anti-inflammatory drugs may contribute to the treatment of migraine attack. This trial is registered at ClinicalTrials.gov (NCT02568644).

Protease activated receptor 2 (PAR2) activation causes migraine-like pain behaviors in mice

BACKGROUND

Pain is the most debilitating symptom of migraine. The cause of migraine pain likely requires activation of meningeal nociceptors. Mast cell degranulation, with subsequent meningeal nociceptor activation, has been implicated in migraine pathophysiology. Degranulating mast cells release serine proteases that can cleave and activate protease activated receptors. The purpose of these studies was to investigate whether protease activated receptor 2 is a potential generator of nociceptive input from the meninges by using selective pharmacological agents and knockout mice.

METHODS

Ratiometric Ca++ imaging was performed on primary trigeminal and dural cell cultures after application of 2at-LIGRL-NH2, a specific protease activated receptor 2 agonist. Cutaneous hypersensitivity and facial grimace was measured in wild-type and protease activated receptor 2-/- mice after dural application of 2at-LIGRL-NH2 or compound 48-80, a mast cell degranulator. Behavioral experiments were also conducted in mice after dural application of 2at-LIGRL-NH2 (2AT) in the presence of either C391, a selective protease activated receptor 2 antagonist, or sumatriptan.

RESULTS

2at-LIGRL-NH2 evoked Ca2+ signaling in mouse trigeminal neurons, dural fibroblasts and in meningeal afferents. Dural application of 2at-LIGRL-NH2 or 48-80 caused dose-dependent grimace behavior and mechanical allodynia that were attenuated by either local or systemic application of C391 as well as in protease activated receptor 2-/- mice. Nociceptive behavior after dural injection of 2at-LIGRL-NH2 was also attenuated by sumatriptan.

CONCLUSIONS

Functional protease activated receptor 2 receptors are expressed on both dural afferents and fibroblasts and activation of dural protease activated receptor 2 produces migraine-like behavioral responses. Protease activated receptor 2 may link resident immune cells to meningeal nociceptor activation, driving migraine-like pain and implicating protease activated receptor 2 as a therapeutic target for migraine in humans.

Migraine-Associated TRESK Mutations Increase Neuronal Excitability through Alternative Translation Initiation and Inhibition of TREK

It is often unclear why some genetic mutations to a given gene contribute to neurological disorders and others do not. For instance, two mutations have previously been found to produce a dominant negative for TRESK, a two-pore-domain K+ channel implicated in migraine: TRESK-MT, a 2-bp frameshift mutation, and TRESK-C110R. Both mutants inhibit TRESK, but only TRESK-MT increases sensory neuron excitability and is linked to migraine. Here, we identify a new mechanism, termed frameshift mutation-induced alternative translation initiation (fsATI), that may explain why only TRESK-MT is associated with migraine. fsATI leads to the production of a second protein fragment, TRESK-MT2, which co-assembles with and inhibits TREK1 and TREK2, two other two-pore-domain K+ channels, to increase trigeminal sensory neuron excitability, leading to a migraine-like phenotype in rodents. These findings identify TREK1 and TREK2 as potential molecular targets in migraine and suggest that fsATI should be considered as a distinct class of mutations.

Targeting MTHFR for the treatment of migraines

INTRODUCTION

Migraine is a common neurovascular disorder classified by the World Health Organization as one of the most debilitating diseases. Migraine is a complex disease and is a consequence of an interaction between genetic, epigenetic and environmental factors. The MTHFR gene is one of the few replicated genetic risk factors for migraine and encodes an enzyme that is crucial for the folate and the methionine cycles. Individuals carrying the T allele of the MTHFR C677T polymorphism have increased plasma concentrations of homocysteine which leads to endothelial cell injury and alterations in coagulant properties of blood. Areas covered: This review focuses on the recent advances in genetics and the role of the MTHFR gene and homocysteine metabolism in migraine etiopathogenesis. The article summarizes the potential of targeting MTHFR and homocysteine for disease prevention. Expert opinion: Determination of MTHFR C677T polymorphisms as well as measurement of homocysteine concentrations may be useful to migraine patients, particularly those suffering from migraine with aura. Preliminary studies support the use of folate, vitamin B6 and vitamin B12 for the prevention of migraine. However, the results of these studies await replication in larger randomized controlled clinical trials.

Increased susceptibility to cortical spreading depression and epileptiform activity in a mouse model for FHM2

Migraine is a highly prevalent, debilitating, episodic headache disorder affecting roughly 15% of the population. Familial hemiplegic migraine type 2 (FHM2) is a rare subtype of migraine caused by mutations in the ATP1A2 gene, encoding the α2 isoform of the Na+/K+-ATPase, predominantly expressed in astrocytes. Differential comorbidities such as epilepsy and psychiatric disorders manifest in patients. Using a mouse model harboring the G301R disease-mutation in the α2 isoform, we set to unravel whether α2+/G301R mice show an increased susceptibility for epilepsy and cortical spreading depression (CSD). We performed in vivo experiments involving cortical application of KCl in awake head-restrained male and female mice of different age groups (adult and aged). Interestingly, α2+/G301R mice indeed showed an increased susceptibility to both CSD and epileptiform activity, closely replicating symptoms in FHM2 patients harboring the G301R and other FHM2-causing mutations. Additionally, this epileptiform activity was superimposed on CSDs. The age-related alteration towards CSD indicates the influence of female sex hormones on migraine pathophysiology. Therefore, the FHM2, α2+/G301R mouse model can be utilized to broaden our understanding of generalized epilepsy and comorbidity hereof in migraine, and may be utilized toward future selection of possible treatment options for migraine.

Quantifying visual allodynia across migraine subtypes: the Leiden Visual Sensitivity Scale

Enhanced sensitivity to light (photophobia) and patterns is common in migraine and can be regarded as visual allodynia. We aimed to develop and validate a questionnaire to easily quantify sensitivity to light and patterns in large populations, and to assess and compare visual allodynia across different migraine subtypes and states. We developed the Leiden Visual Sensitivity Scale (L-VISS), a 9-item scale (score range 0-36 points), based on literature and patient interviews, and examined its construct validity. Furthermore, we assessed ictal and interictal visual sensitivity in episodic migraine with (n = 67) and without (n = 66) aura and chronic migraine with (n = 20) and without (n = 19) aura, and in healthy controls (n = 86). Differences between migraine subtypes and states were tested using a linear mixed model with 3 fixed factors (episodic/chronic, with/without aura, and ictal/interictal). Test-retest reliability and construct validity of L-VISS were good. Leiden Visual Sensitivity Scale scores correlated in the expected direction with light discomfort (Kendall's τ = -0.25) and pattern glare tests (τ = 0.35). Known-group comparisons confirmed its construct validity. Within migraine subtypes, L-VISS scores were higher in migraine with aura versus without aura and in chronic versus episodic migraine. The linear mixed model showed all factors affected the outcome (P < 0.001). The L-VISS is an easy-to-use scale to quantify and monitor the burden of bothersome visual sensitivity to light and patterns in large populations. There are remarkable ictal and interictal differences in visual allodynia across migraine subtypes, possibly reflecting dynamic differences in cortical excitability.

Histological investigations on the dura mater vascular system of mice

The human dura mater encephali is a well innervated and vascularized membrane. Its vascular system plays a crucial role in disorders and pathological cases like dural hematoma, meningitis, and different headache types. To investigate these diseases mouse models are increasingly being used. However, the literature on the vascular system of the mouse dura mater is sparse and explicit studies concerned exclusively with its vasculature are lacking. Here we present a detailed light and scanning electron microscopic investigation of the supratentorial dura mater of the mouse species, with a focus on the largest part of it, the parietal dura mater. By utilizing different immunohistochemical and classical staining methods, a "cartography" of the vascular system was achieved. Additionally, the different blood vessel types with their mural cells were characterized. In contrast to humans, no arteries were found in the mouse parietal dura mater. Its supply is assured through frontolateral and occipital localized arteriolar branches. These arteriolar vessels exhibit in some specimens arteriolar anastomoses with one another. The venous blood is drained to the superior sagittal and transverse sinus through satellite venules accompanying the arterioles or through solitary venules. In all samples, large ruptured venules were identified in the frontolateral dural area. Scanning electron microscopy revealed that these vessels were ruptured on the dorsal side (skull bones-oriented side) of the dura. Our results contribute to the anatomical data on the mouse species and may set up a basis for fundamental investigation of disorders, for which the role of dural blood vessels is not yet clarified.

Blast-induced brain injury in rats leads to transient vestibulomotor deficits and persistent orofacial pain

Blast-induced traumatic brain injury (blast-TBI) is associated with vestibulomotor dysfunction, persistent post-traumatic headaches and post-traumatic stress disorder, requiring extensive treatments and reducing quality-of-life. Treatment and prevention of these devastating outcomes require an understanding of their underlying pathophysiology through studies that take advantage of animal models. Here, we report that cranium-directed blast-TBI in rats results in signs of pain that last at least 8 weeks after injury. These occur without significantly elevated behavioural markers of anxiety-like conditions and are not associated with glial up-regulation in sensory thalamic nuclei. These injuries also produce transient vestibulomotor abnormalities that resolve within 3 weeks of injury. Thus, blast-TBI in rats recapitulates aspects of the human condition.

[The prevalence of the palmo-mental reflex in patients with cervicocranialgia]

AIM

To study characteristics of the palmo-mental reflex (PMR) in patients with cervicalgia accompanied by the most common forms of headaches: migraine, tension-type headache (TTH) and cervicogenic headache (CGH).

MATERIAL AND METHODS

Prevalence of PMR was studied in a sample of 142 patients with neck pain (mean age 39.1±12.1 years; 103 women and 39 men) accompanied by migraine, TTH or CGH. The first group included 66 patients (51 women and 15 men; mean age 39.4±12.8 years) with neck pain accompanied predominantly by migraine. The second group included 76 patients (52 women and 24 men; mean age 38.9±11.7 years) with TTH and/or CGH.

RESULTS

The palmo-mental reflex was observed in 86.4% patients of the 1-st group and 7.0% of the second group (χ²=91.41; p=0.000).

CONCLUSION

The results suggest the presence of anatomical and pathophysiological premises for occurrence of this reflex in patients with neck pain accompanied by migraine.

Visually induced analgesia during face or limb stimulation in healthy and migraine subjects

Background

Visually induced analgesia (VIA) defines a phenomenon in which viewing one’s own body part during its painful stimulation decreases the perception of pain. VIA occurs during direct vision of the stimulated body part and also when seeing it reflected in a mirror. To the best of our knowledge, VIA has not been studied in the trigeminal area, where it could be relevant for the control of headache.

Subjects and methods

We used heat stimuli (53°C) to induce pain in the right forehead or wrist in 11 healthy subjects (HSs) and 14 female migraine without aura (MO) patients between attacks. The subjects rated pain on a visual analog scale (VAS) and underwent contact heat-evoked potential (CHEP) recordings (five sequential blocks of four responses) with or without observation of their face/wrist in a mirror.

Results

During wrist stimulation, amplitude of the first block of P1–P2 components of CHEPs decreased compared to that in the control recording when HSs were seeing their wrist reflected in the mirror (p = 0.036; Z = 2.08); however, this was not found in MO patients. In the latter, the VAS pain score increased viewing the reflected wrist (p = 0.049; Z = 1.96). Seeing their forehead reflected in the mirror induced a significant increase in N2 latency of CHEPs in HSs, as well as an amplitude reduction in the first block of P1–P2 components of CHEPs both in HSs (p = 0.007; Z = 2.69) and MO patients (p = 0.035; Z = 2.10). Visualizing the body part did not modify habituation of CHEP amplitudes over the five blocks of averaged responses, neither during wrist nor during forehead stimulation.

Conclusion

This study adds to the available knowledge on VIA and demonstrates this phenomenon for painful stimuli in the trigeminal area, as long as CHEPs are used as indices of central pain processing. In migraine patients during interictal periods, VIA assessed with CHEPs is within normal limits in the face but absent at the wrist, possibly reflecting dysfunctioning of extracephalic pain control.

Tracking patients with chronic occipital headache after occipital nerve decompression surgery: A case series

BACKGROUND

The therapeutic benefit of nerve decompression surgeries for chronic headache/migraine are controversial.

AIM

To provide clinical characteristics of headache type and treatment outcome of occipital nerve decompression surgery.

METHODS

A retrospective review of clinical records. Inclusion criteria were evidence of chronic occipital headache with and without migrainous features and tenderness of neck muscles, occipital allodynia, and inadequate response to prophylactic drugs.

RESULTS

Surgical decompression of the greater and lesser occipital nerves provided complete and extended (3-6 years) relief of new daily persistent headache in case 3 (46 year old female), and of chronic post-traumatic headache in cases 4 and 6 (35 and 30 year old females, respectively), partial relief of chronic headache/migraine in cases 1 and 2 (41 year old female and 36 year old male), and no relief of episodic (cases 3 and 4) or chronic migraine (case 5, 52 year old male), or chronic tension-type headache (case 7, 31 year old male).

CONCLUSIONS

As a case series, this study cannot test a hypothesis or determine cause and effect. However, the complete elimination of new daily persistent headache and post-traumatic headache, and the partial elimination of chronic headache/migraine in two patients - all refractory to other treatment approaches - supports and justifies the effort to continue to generate data that can help determine whether decompression nerve surgeries are beneficial in the treatment of certain types of chronic headache.

Myofascial trigger points in migraine and tension-type headache

BACKGROUND

A myofascial trigger point is defined as a hyperirritable spot in skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band. It has been suggested that myofascial trigger points take part in chronic pain conditions including primary headache disorders. The aim of this narrative review is to present an overview of the current imaging modalities used for the detection of myofascial trigger points and to review studies of myofascial trigger points in migraine and tension-type headache.

FINDINGS

Different modalities have been used to assess myofascial trigger points including ultrasound, microdialysis, electromyography, infrared thermography, and magnetic resonance imaging. Ultrasound is the most promising of these modalities and may be used to identify MTrPs if specific methods are used, but there is no precise description of a gold standard using these techniques, and they have yet to be evaluated in headache patients. Active myofascial trigger points are prevalent in migraine patients. Manual palpation can trigger migraine attacks. All intervention studies aiming at trigger points are positive, but this needs to be further verified in placebo-controlled environments. These findings may imply a causal bottom-up association, but studies of migraine patients with comorbid fibromyalgia syndrome suggest otherwise. Whether myofascial trigger points contribute to an increased migraine burden in terms of frequency and intensity is unclear. Active myofascial trigger points are prevalent in tension-type headache coherent with the hypothesis that peripheral mechanisms are involved in the pathophysiology of this headache disorder. Active myofascial trigger points in pericranial muscles in tension-type headache patients are correlated with generalized lower pain pressure thresholds indicating they may contribute to a central sensitization. However, the number of active myofascial trigger points is higher in adults compared with adolescents regardless of no significant association with headache parameters. This suggests myofascial trigger points are accumulated over time as a consequence of TTH rather than contributing to the pathophysiology.

CONCLUSIONS

Myofascial trigger points are prevalent in both migraine and tension-type headache, but the role they play in the pathophysiology of each disorder and to which degree is unclarified. In the future, ultrasound elastography may be an acceptable diagnostic test.

Migraine with aura and white matter tract changes

We aimed to explore whether a migraine with aura (MA) is associated with structural changes in tracts of a white matter and to compare parameters of diffusivity between subgroups in migraineurs. Forty-three MA and 20 healthy subjects (HS), balanced by sex and age, were selected for this study. Analysis of diffusion tensor parameters was used to identify differences between MA patients and HS, and then between MA subgroups. A diffusion tensor probabilistic tractography analysis showed that there is no difference between MA patients and HS. However, using more-liberal uncorrected statistical threshold, we noted a trend in MA patients toward lower diffusivity indices of selected white matter tracts located in the forceps minor and right anterior thalamic radiation (ATR), superior longitudinal fasciculus (temporal part) (SLFT), cingulum-cingulate tract, and left uncinate fasciculus. Migraineurs who experienced somatosensory and dysphasic aura, besides visual symptoms, had tendency toward lower diffusivity indices, relative to migraineurs who experienced only visual symptoms, in the right inferior longitudinal fasciculus, forceps minor, and right superior longitudinal fasciculus (parietal part), SLFT, and cingulum-angular bundle. Aura frequency were negatively correlated with axial diffusivity and mean diffusivity of the right ATR (partial correlation = - 0.474; p = 0.002; partial correlation = - 0.460; p = 0.002), respectively. There were no significant differences between MA patients and HS, neither between MA subgroups. Migraineurs with abundant symptoms during the aura possibly have more myelinated fibers relative to those who experience only visual symptoms. Lower diffusivity indices of the right ATR are linked to more frequent migraine with aura attacks.

Rationale for electrical parameter determination in external trigeminal nerve stimulation (eTNS) for migraine: A narrative review

Background

Migraine is a primary headache disorder involving dysregulation of central and peripheral pain pathways. Medical treatment is often limited by drug side effects, comorbidities and poor compliance. This makes neuromodulation an ideal option for migraine treatment. Cefaly® is a transcutaneous electrical neurostimulator designed specifically for migraine treatment. It results in external trigeminal nerve stimulation of the supraorbital and supratrochlear nerves. External trigeminal nerve stimulation is effective for acute and preventive migraine treatment and may result in normalization of dysregulated pain pathways.

Objective

Our objective was to provide a narrative review of the neuroanatomical and pathophysiological basis of external trigeminal nerve stimulation for migraine treatment and to provide the rationale behind the choice of the electrical parameters used for external trigeminal nerve stimulation.

Methods

We reviewed external trigeminal nerve stimulation clinical trial publications, basic science neurostimulation literature, publications describing pathophysiological mechanisms in migraine, and documentation used in the application for the Food and Drug Administration approval of external trigeminal nerve stimulation.

Results

The electrical parameters used for external trigeminal nerve stimulation were chosen to maximize safety and efficacy. Critical parameters include generator characteristics, pulse shape, pulse duration, pulse frequency and session duration and frequency. We explain the rationale behind determination of each parameter. There is evidence of dysregulated central and peripheral pathways in migraine and evidence that external trigeminal nerve stimulation may normalize function of these pathways.

Conclusion

External trigeminal nerve stimulation is a safe and effective Food and Drug Administration-approved option for the acute and preventive treatment of migraine. The electrical parameters were optimized specifically for external stimulation of the trigeminal nerve to maximum safety, comfort and efficacy.

Strides Toward Better Understanding of Post-Traumatic Headache Pathophysiology Using Animal Models

PURPOSE OF REVIEW

In recent years, the awareness of the detrimental impact of concussion and mild traumatic brain injuries (mTBI) is becoming more apparent. Concussive head trauma results in a constellation of cognitive and somatic symptoms of which post-traumatic headache is the most common. Our understanding of post-traumatic headache is limited by the paucity of well validated, characterized, and clinically relevant animal models with strong predictive validity. In this review, we aim to summarize and discuss current animal models of concussion/mTBI and related data that start to shed light on the pathophysiology of post-traumatic headache.

RECENT FINDINGS

Each of the models will be discussed in terms of their face, construct, and predictive validity as well as overall translational relevance to concussion, mTBI, and post-traumatic headache. Significant contributions to the pathophysiology of PTH garnered from these models are discussed as well as potential contributors to the development of chronic post-traumatic headache. Although post-traumatic headache is one of the most common symptoms following mild head trauma, there remains a disconnect between the study of mild traumatic brain injury and headache in the pre-clinical literature. A greater understanding of the relationship between these phenomena is currently needed to provide more insight into the increasing frequency of this debilitating condition in both military and civilian populations.

[Progressive muscle relaxation according to Jacobson for migraine prophylaxis : Clinical effectiveness and mode of action]

Progressive muscle relaxation (PMR) after Jacobson has been used for migraine prophylaxis since the early 1970s. Migraine patients are assumed to have an enhanced autonomic arousal which can be counterbalanced by systematic relaxation. Relaxation techniques are thought to reduce the activation level, to alter cortical pain processing and to enhance activation in pain-reducing cortical structures in the periaqueductal grey matter. Meta-analyses could show PMR to be just as efficacious as pharmacological treatment options. A beneficial effect can only arise if regular daily exercises of 5-25 min are performed and the exercises are transferred into the daily routine. This review critically summarizes the empirical findings concerning the effects of PMR on migraine. A lack of recent research on this topic was determined. In a study by this group 50 migraine patients and 46 healthy controls were examined. It could be shown that in addition to the clinical efficacy on migraine frequency, changes in cortical information processing, measured by means of the evoked potential contingent negative variation (CNV) could also be determined. The initially increased CNV amplitude became normalized after regular PMR training in migraine patients. With the review of PMR studies on migraine prophylaxis and the results of our own study it could be shown that PMR is an efficacious non-pharmacological treatment option for migraine prophylaxis. In addition to its clinical effects, alterations in cortical stimulation processing in terms of a normalization of the CNV could be documented.

Brain structure and function related to headache: Brainstem structure and function in headache

OBJECTIVE

To review and discuss the literature relevant to the role of brainstem structure and function in headache.

BACKGROUND

Primary headache disorders, such as migraine and cluster headache, are considered disorders of the brain. As well as head-related pain, these headache disorders are also associated with other neurological symptoms, such as those related to sensory, homeostatic, autonomic, cognitive and affective processing that can all occur before, during or even after headache has ceased. Many imaging studies demonstrate activation in brainstem areas that appear specifically associated with headache disorders, especially migraine, which may be related to the mechanisms of many of these symptoms. This is further supported by preclinical studies, which demonstrate that modulation of specific brainstem nuclei alters sensory processing relevant to these symptoms, including headache, cranial autonomic responses and homeostatic mechanisms.

REVIEW FOCUS

This review will specifically focus on the role of brainstem structures relevant to primary headaches, including medullary, pontine, and midbrain, and describe their functional role and how they relate to mechanisms of primary headaches, especially migraine.

Migraine as a risk factor for primary open angle glaucoma: A systematic review and meta-analysis

Migraine is increasingly being reported as a risk factor for primary open angle glaucoma (POAG). However, studies aimed to investigate this association yielded conflicting results. To assess the consistency of the data on the topic, we performed a systematic review and meta-analysis. A systematic literature search from Embase, Web of Science, and PubMed was performed to identify relevant studies on the relationship between migraine and POAG. Random effects models were used to estimate the pooled relative risks (RRs) with 95% confidence intervals (95% CIs) in this meta-analysis. A total of 11 studies meeting the inclusion criteria were included in this meta-analysis. Our findings showed an RR of developing POAG of 1.24 (95% CI = 1.12-1.37) in migraine patients. No evidence of significant heterogeneity was detected across studies (P = .071; I = 41.7%). This association was not modified by the glaucoma type of the included patients. A significant association was observed in case-control design studies, but not in cohort design studies. Little evidence of publication bias was found. The findings of this meta-analysis suggest that migraine can significantly increase the risk of the development of POAG. However, the cohort study design failed to identify this association. Whether migraines can significantly increase the risk of developing POAG is still controversial.

Advances in migraine neuroimaging and clinical utility: from the MRI to the bedside

INTRODUCTION

In current migraine clinical practice, no specific diagnostic investigations are available and therefore the diagnosis is an eminently clinical process where instrumental examinations may have a part to exclude possible causes of secondary headaches. While migraine clinical phenotype has been widely characterized, migraine pathophysiology has still a gap that might be partly bridged by structural and functional neuroimaging investigations. Areas covered: This article aims to review the recent advances in functional neuroimaging, the consequent progress in the knowledge of migraine pathophysiology and their putative application and impact in the clinical setting. A comprehensive review was conducted of PubMed citations by entering the key word 'MRI' combined with 'migraine' AND/OR 'headache.' Other key words included 'gray matter' OR 'white matter,' 'structural' OR 'functional.' The only restriction was English-language publication. The abstracts of all articles meeting these criteria were reviewed, and full texts were examined for relevant references. Expert commentary: Advanced magnetic resonance imaging (MRI) techniques are tremendously improving our knowledge about brain abnormalities in migraine patients. However, advanced MRI could nowadays overcome the limits linked to the clinicians' judgment through the identification of objectively measurable neuroimaging findings (quantitative biomarkers) concerning the diagnosis, the prognosis and 'tailored' therapeutic-care pathways.