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

Differential alteration of fMRI signal variability in the ascending trigeminal somatosensory and pain modulatory pathways in migraine

BACKGROUND

The moment-to-moment variability of resting-state brain activity has been suggested to play an active role in chronic pain. Here, we investigated the regional blood-oxygen-level-dependent signal variability (BOLDSV) and inter-regional dynamic functional connectivity (dFC) in the interictal phase of migraine and its relationship with the attack severity.

METHODS

We acquired resting-state functional magnetic resonance imaging from 20 migraine patients and 26 healthy controls (HC). We calculated the standard deviation (SD) of the BOLD time-series at each voxel as a measure of the BOLD signal variability (BOLDSV) and performed a whole-brain voxel-wise group comparison. The brain regions showing significant group differences in BOLDSV were used to define the regions of interest (ROIs). The SD and mean of the dynamic conditional correlation between those ROIs were calculated to measure the variability and strength of the dFC. Furthermore, patients' experimental pain thresholds and headache pain area/intensity levels during the migraine ictal-phase were assessed for clinical correlations.

RESULTS

We found that migraineurs, compared to HCs, displayed greater BOLDSV in the ascending trigeminal spinal-thalamo-cortical pathways, including the spinal trigeminal nucleus, pulvinar/ventral posteromedial (VPM) nuclei of the thalamus, primary somatosensory cortex (S1), and posterior insula. Conversely, migraine patients exhibited lower BOLDSV in the top-down modulatory pathways, including the dorsolateral prefrontal (dlPFC) and inferior parietal (IPC) cortices compared to HCs. Importantly, abnormal interictal BOLDSV in the ascending trigeminal spinal-thalamo-cortical and frontoparietal pathways were associated with the patient's headache severity and thermal pain sensitivity during the migraine attack. Migraineurs also had significantly lower variability and greater strength of dFC within the thalamo-cortical pathway (VPM-S1) than HCs. In contrast, migraine patients showed greater variability and lower strength of dFC within the frontoparietal pathway (dlPFC-IPC).

CONCLUSIONS

Migraine is associated with alterations in temporal signal variability in the ascending trigeminal somatosensory and top-down modulatory pathways, which may explain migraine-related pain and allodynia. Contrasting patterns of time-varying connectivity within the thalamo-cortical and frontoparietal pathways could be linked to abnormal network integrity and instability for pain transmission and modulation.

Ictal and interictal brain activation in episodic migraine: Neural basis for extent of allodynia

In some patients, migraine attacks are associated with symptoms of allodynia which can be localized (cephalic) or generalized (extracephalic). Using functional neuroimaging and cutaneous thermal stimulation, we aimed to investigate the differences in brain activation of patients with episodic migraine (n = 19) based on their allodynic status defined by changes between ictal and interictal pain tolerance threshold for each subject at the time of imaging. In this prospective imaging study, differences were found in brain activity between the ictal and interictal visits in the brainstem/pons, thalamus, insula, cerebellum and cingulate cortex. Significant differences were also observed in the pattern of activation along the trigeminal pathway to noxious heat stimuli in no allodynia vs. generalized allodynia in the thalamus and the trigeminal nucleus but there were no activation differences in the trigeminal ganglion. The functional magnetic resonance imaging (fMRI) findings provide direct evidence for the view that in migraine patients who are allodynic during the ictal phase of their attacks, the spinal trigeminal nucleus and posterior thalamus become hyper-responsive (sensitized)–to the extent that they mediate cephalic and extracephalic allodynia, respectively. In addition, descending analgesic systems seem as “switched off” in generalized allodynia.

Entrapment of the Greater Occipital Nerve with Chronic Migraine and Severe Facial Pain: A Case Report

Migraine is thought to be a primary neurovascular headache due to brain dysfunction and is known to involve peripheral and central sensitization. A female patient with chronic migraine symptoms for 30 years reported severe pain in the deep ear and face. This headache always showed the same pattern and temporal progression. The sudden onset of ache and throbbing pain in the right temporo-occipital area extended to the left temporo-occipital areas. She felt sick as if the head would burst, and nausea and vomiting occurred. During the last 3 years, the patient endured sharp pain in bilateral deep ears and severe pain in the face as if all the facial bones were broken, and tears flowed. Chronic disabling headache and facial pain improved with the decompression of the greater occipital nerve. This case suggests that peripheral sensitization may be related to the pathophysiology of migraine, especially in the migraine without aura.

Parabrachial complex processes dura inputs through a direct trigeminal ganglion-to-parabrachial connection

Migraines cause significant disability and contribute heavily to healthcare costs. Irritation of the meninges' outermost layer (the dura mater), and trigeminal ganglion activation contribute to migraine initiation. Maladaptive changes in central pain-processing regions are also important in maintaining pain. The parabrachial complex (PB) is a central region that mediates chronic pain. PB receives diverse sensory information, including a direct input from the trigeminal ganglion. We hypothesized that PB processes inputs from the dura. Using in vivo electrophysiology recordings from single units in anesthetized rats we identified 58 neurons in lateral PB that respond reliably and with short latency to electrical dura stimulation. After injecting tracer into PB, anatomical examination reveals retrogradely labeled cell bodies in the trigeminal ganglion. Neuroanatomical tract-tracing revealed a population of neurons in the trigeminal ganglion that innervate the dura and project directly to PB. These findings indicate that PB is strategically placed to process dura inputs and suggest that it is directly involved in the pathogenesis of migraine headaches.

miR-34a-5p up-regulates the IL-1β/COX2/PGE2 inflammation pathway and induces the release of CGRP via inhibition of SIRT1 in rat trigeminal ganglion neurons

Migraine is a debilitating neurological condition, with a global prevalence rate of 10.68% in men and 18.79% in women. Elucidation of the molecular mechanisms underlying migraines is of great importance for improving the quality of life of patients. The release of the neuropeptide calcitonin gene-related peptide (CGRP) from trigeminal nerve terminals is involved in the pathogenesis of migraine. Recent studies have shown that up-regulation of miR-34a-5p expression is associated with acute migraine attacks. Here, we investigated whether alteration of the expression of miR-34a-5p induces the release of the vasoactive peptide CGRP. We isolated primary rat trigeminal ganglion neurons and performed gain- and loss-of-function assays to alter the expression level of miR-34a-5p. Down-regulation of miR-34a-5p inhibited the expression of interleukin-1β (IL-1β)/cyclooxygenase 2 (COX2)/prostaglandin E2 (PGE2), decreased IL-1β, PGE2 and CGRP release, and up-regulated the expression of silencing information regulator 1 (SIRT1) in trigeminal ganglion, whereas overexpression of miR-34a-5p enhanced the expression of IL-1β/COX2/PGE2, increased the release of IL-1β, PGE2 and CGRP, and decreased the expression of SIRT1 in trigeminal ganglion. In addition, overexpression of miR-34a-5p induced apoptosis in primary rat trigeminal neurons. In summary, these findings suggest that miR-34a-5p up-regulates the IL-1β/COX2/PGE2 inflammation pathway, induces apoptosis and enhances release of CGRP via inhibition of SIRT1 expression in trigeminal ganglion neurons; thus, miR-34a-5p may have potential as a therapeutic target for the treatment of migraine.

Noninvasive vagus nerve stimulation and morphine transiently inhibit trigeminal pain signaling in a chronic headache model

Noninvasive vagus nerve stimulation suppressed persistent trigeminal nociception in a chronic headache model similarly to morphine and may provide a safe, nonaddictive abortive therapy for chronic headache.

Introduction:

Chronic headache conditions are characterized by persistent sensitization of the trigeminal system, which involves dysfunction of descending pain modulation. We previously reported that noninvasive vagus nerve stimulation (nVNS) inhibits trigeminal nociception in models of episodic migraine through a mechanism involving enhanced serotonergic and GABAergic descending pain signaling.

Objectives:

The analgesic effectiveness of nVNS and morphine were investigated in an animal model of chronic headache mediated by the combination of the 3 migraine risk factors of neck muscle tension, paradoxical sleep deprivation, and pungent odors.

Methods:

Sprague–Dawley rats were injected with complete Freund's adjuvant in the trapezius and sleep deprived for 1 night to promote trigeminal sensitization. After 7 days, animals were exposed to a pungent odor, and mechanical nocifensive head withdrawal responses were determined using von Frey filaments. Beginning on day 3 after odor exposure, animals were treated daily with either nVNS or morphine for 7 days.

Results:

Exposure of animals sensitized by neck inflammation and sleep deprivation to a pungent odor resulted in a prolonged state of trigeminal nociception. Daily administration of nVNS or morphine significantly repressed the nocifensive response; however, cessation resulted in a return to heightened pretreatment nocifensive levels.

Conclusions:

The combination of reported migraine risk factors promotes a state of sustained trigeminal hypersensitivity characteristic of chronic headache. Daily nVNS was similarly effective as morphine in inhibiting nociception and may represent a safer, opioid-sparing therapeutic option for other chronic pain disorders involving sensitization of the trigeminal system by promoting descending pain modulation.

Open Label Prospective Experience of Supplementation with a Fixed Combination of Magnesium, Vitamin B2, Feverfew, Andrographis Paniculata and Coenzyme Q10 for Episodic Migraine Prophylaxis

BACKGROUND

To investigate the efficacy and safety of supplementation with a fixed combination of magnesium, vitamin B2, feverfew, andrographis paniculata and coenzyme Q10 in episodic migraine (EM) prevention.

METHODS

A pilot, single-arm, open-label study was conducted. After a one-month baseline period, the above-described supplementation was introduced in 113 EM Greek patients, who were prospectively followed-up for three months. The primary endpoint was the change in monthly migraine days between baseline period (BSL) and the third month of supplementation (T3). Secondary endpoints included changes in mean intensity of migraine and in days with use of acute migraine medications. Changes in scores of Migraine Disability Assessment questionnaire (MIDAS), Headache Impact Test-6 (HIT-6), Migraine Therapy Assessment questionnaire (MTAQ), Migraine-Specific Quality-of-life questionnaire (MSQ-QOL), Hospital Anxiety and Depression Scale (HADS) were also evaluated. Those with ≥50% reduction in monthly migraine days at T3, compared to BSL were considered supplementation-responders.

RESULTS

The mean number of migraine days was significantly decreased between BSL and T3 (9.4 ± 3.7 vs. 6.1 ± 3.5; p < 0.001). Likewise, days with peak headache intensity of >4/10 (5.7 ± 3.4 vs. 4.9 ± 3.1; p < 0.001) as well as days using acute headache medications per month (8.9 ± 3.6 vs. 5.7 ± 3.4; p < 0.001) were significantly reduced. At T3, 64 patients (56.6%) were classified as responders. The beneficial effect of supplementation was also associated with significant changes in HIT-6, MIDAS, MTAQ and MSQ-QOL scores. There were no safety concerns.

CONCLUSIONS

The supplementation we have tested appears to be an effective and well-tolerated preventive approach against EM. A randomized, placebo-controlled study is needed to confirm our results.

Anti-Inflammatory and Neuromodulatory Effects Induced by Tanacetum parthenium Water Extract: Results from In Silico, In Vitro and Ex Vivo Studies

Tanacetum parthenium (feverfew) has traditionally been employed as a phytotherapeutic remedy in the treatment of migraine. In this study, a commercial T. parthenium water extract was investigated to explore its anti-inflammatory and neuromodulatory effects. Isolated mouse cortexes were exposed to a K⁺ 60 mM Krebs-Ringer buffer and treated with T. parthenium water extract. The prostaglandin E₂ (PGE₂) level, brain-derived neurotrophic factor (BDNF), interleukin-10 (IL-10), and IL-1β gene expression were evaluated in the cortex. The effects on dopamine (DA) release and dopamine transporter (DAT) gene expression were assayed in hypothalamic HypoE22 cells. A bioinformatics analysis was conducted to further investigate the mechanism of action. The extract was effective in reducing cortex PGE₂ release and IL-1β gene expression. In the same experimental system, IL-10 and BDNF gene expressions increased, and in HypoE22 cells, the extract decreased the extracellular dopamine level and increased the DAT gene expression due to the direct interaction of parthenolide with the DAT. Overall, the present findings highlight the efficacy of T. parthenium water extract in controlling the inflammatory pathways that occur during cortical-spreading depression. Additionally, the inhibition of the hypothalamic DA release observed in this study further supports the role of dopaminergic pathways as key targets for novel pharmacological approaches in the management of migraine attacks.

Renin-Angiotensin-Aldosterone System and Migraine: A Systematic Review of Human Studies

Migraine is a common neurologic condition marked by recurrent episodes of headache. Its pathophysiology is highly complex involving neuronal, inflammatory and vascular mechanisms. The Renin-Angiotensin System (RAS) can modulate all these mechanism, being a potential pharmacological target for migraine treatment. We carried out a systematic review of the studies evaluating the involvement of RAS in patients with migraine. There is evidence from genetic studies exploring the relation between migraine and RAS-related genes and from clinical trials evaluating the efficacy of Angiotensin II Type 1 (AT1) receptor antagonists and angiotensin converting enzyme inhibitors in migraine prophylaxis. RAS seems to play a role in the pathophysiology of migraine, but more direct evidence is still missing.

Responsivity to light in familial hemiplegic migraine type 1 mutant mice reveals frequency-dependent enhancement of visual network excitability

Migraine patients often report (inter)ictal hypersensitivity to light, but the underlying mechanisms remain an enigma. Both hypo- and hyperresponsivity of the visual network have been reported, which may reflect either intra-individual dynamics of the network or large inter-individual variation in the measurement of human visual evoked potential data. Therefore, we studied visual system responsivity in freely behaving mice using combined epidural electroencephalography and intracortical multi-unit activity to reduce variation in recordings and gain insight into visual cortex dynamics. For better clinical translation, we investigated transgenic mice that carry the human pathogenic R192Q missense mutation in the α_1A subunit of voltage-gated Ca_V 2.1 Ca²⁺ channels leading to enhanced neurotransmission and familial hemiplegic migraine type 1 in patients. Visual evoked potentials were studied in response to visual stimulation paradigms with flashes of light. Following intensity-dependent visual stimulation, FHM1 mutant mice displayed faster visual evoked potential responses, with lower initial amplitude, followed by less pronounced neuronal suppression compared to wild-type mice. Similar to what was reported for migraine patients, frequency-dependent stimulation in mutant mice revealed enhanced photic drive in the EEG beta-gamma band. The frequency-dependent increases in visual network responses in mutant mice may reflect the context-dependent enhancement of visual cortex excitability, which could contribute to our understanding of sensory hypersensitivity in migraine.

Preclinical studies investigating the neural mechanisms involved in the co-morbidity of migraine and temporomandibular disorders: the role of CGRP

BACKGROUND AND PURPOSE

Temporomandibular disorders (TMD) and migraine can be co-morbid. This can be a significant factor in exacerbating and increasing the prevalence of migraine-like symptoms. However, the underlying mechanisms involved are unknown. Our objective was to investigate these neural mechanisms and the role of CGRP as a key modulator in this co-morbidity.

EXPERIMENTAL APPROACH

We combined experimental approaches using CGRP, which triggers a migraine-like response in patients, with that of masseteric muscle injection of complete Freund's adjuvant (CFA), to model myofascial TMD-like inflammation. Using validated electrophysiological methods to assess each of the above approaches independently or in combination, we examined their effects on the response properties of migraine-like dural-trigeminocervical neurons.

KEY RESULTS

Independently, in ~2/3 of animals (rats) each approach caused delayed migraine-like activation and sensitisation of dural-trigeminocervical neurons. The response to masseteric-CFA was attenuated by a selective CGRP receptor antagonist. The combination approach caused a migraine-like neuronal response in all animals tested, with somatosensory-evoked cranial hypersensitivity significantly exacerbated.

CONCLUSION AND IMPLICATIONS

The data demonstrate a neuronal phenotype that translates to the exacerbated clinical co-morbid phenotype, supporting this combination approach as a relevant model to study the mechanisms involved. It provides a pathophysiological rationale for this exacerbated phenotype, strongly implicating the involvement of CGRP. The results provide support for targeting the CGRP pathway as a novel monotherapy approach for treating this co-morbid condition. This has key implications into our understanding of this co-morbid condition, as well as potentially addressing the major unmet need for novel and effective therapeutic approaches.

Pharmacological strategies to treat attacks of episodic migraine in adults

INTRODUCTION

Migraine patients prioritize early complete relief of headache and associated symptoms, sustained freedom of pain, and good tolerability. One major obstacle for the successful use of drug treatment of migraine attack is that the speed of action of triptans, 5-HT_1B/1D receptor agonists, is delayed.

AREAS COVERED

In this review, the author discusses the following features of acute migraine drugs: pharmacology; pharmacokinetics, and absorption of drugs during migraine attacks. Next, dose-response curves for effect; and the delayed onset of action is reviewed. In the more clinical part of the review, the following items are discussed: overall clinical judgments; comparison of triptans; comparison of triptans with NSAIDs; early intervention with triptans; medication-overuse headache; comments on the effect of gepants; and the general principle of acute migraine therapy.

EXPERT OPINION

The delay in the onset of effect of acute migraine drugs is likely due to a complex antimigraine system involving more than one site of action. Investigations into the mechanisms of the delay should have a high priority, both in studies with animals, migraine models, and in migraine patients during attacks. Non-oral administration of antimigraine drugs resulting in early absorption of drugs should be developed as they possibly also can increase E_max.

Understanding the most commonly billed diagnoses in primary care: Headache disorders

This article, part of a series about the most commonly billed diagnoses in primary care, describes the pathophysiologic processes of the three most common types of headache disorders as well as how the clinical manifestations and treatments are linked to the pathogenesis of the disorders.

The association between melatonin and episodic migraine: A pilot network meta-analysis of randomized controlled trials to compare the prophylactic effects with exogenous melatonin supplementation and pharmacotherapy

Although exogenous melatonin supplementation has been suggested to be effective for episodic migraine prophylaxis, there is no conclusive evidence comparing the efficacy of exogenous melatonin supplementation to the other FDA-approved pharmacotherapy for episodic migraine prophylaxis. The aim of the current network meta-analysis (NMA) was to compare the efficacy of exogenous melatonin supplementation in patients with episodic migraine. The randomized placebo-controlled trials or randomized controlled trials (RCTs) incorporating a placebo in the study designs were included in our analyses. All of the NMA procedures were conducted under the frequentist model. The primary outcome was changes in frequency of migraine days and response rate after migraine prophylaxis with melatonin supplementation or pharmacological interventions. We included 25 RCTs in total with 4499 patients (mean age = 36.0 years, mean female proportion = 78.9%). The NMA demonstrated that migraine prophylaxis with oral melatonin 3 mg/d (immediate-release) at bedtime was associated with the greatest improvement in migraine frequency [mean difference = -1.71 days, 95% confidence interval (CI): -3.27 to -0.14 days compared to placebo] and the second highest response rate (odds ratio = 4.19, 95% CI = 1.46 to 12.00 compared to placebo). Furthermore, oral melatonin 3 mg (immediate-release) at bedtime was the most preferred pharmacological intervention among all of the investigated interventions when improvements in migraine frequency, response rate, dropout rate, and rates of any adverse events were taken into account. This pilot NMA suggests the potential prophylactic role of exogenous melatonin supplementation in patients with episodic migraine.

Dynamic functional connectivity of the migraine brain: a resting-state functional magnetic resonance imaging study

Migraine headache is an episodic phenomenon, and patients with episodic migraine have ictal (headache), peri-ictal (premonitory, aura, and postdrome), and interictal (asymptomatic) phases. We aimed to find the functional characteristics of the migraine brain regardless of headache phase using dynamic functional connectivity analysis. We prospectively recruited 50 patients with migraine and 50 age- and sex-matched controls. All subjects underwent a resting-state functional magnetic resonance imaging. Significant networks were defined in a data-driven fashion from the interictal (>48 hours apart from headache phases) patients and matched controls (interictal data set) and tested to ictal or peri-ictal patients and controls (ictal/peri-ictal data set). Both static and dynamic analyses were used for the between-group comparison. A false discovery rate correction was performed. As a result, the static analysis did not reveal a network which was significant in both interictal and ictal/peri-ictal data sets. Dynamic analysis revealed significant between-group differences in 7 brain networks in the interictal data set, among which a frontoparietal network (controls > patients, P = 0.0467), 2 brainstem networks (patients > controls, P = 0.0467 and <0.001), and a cerebellar network (controls > patients, P = 0.0408 and <0.001 in 2 states) remained significant in the ictal/peri-ictal data set. Using these networks, migraine was classified with a sensitivity of 0.70 and specificity of 0.76 in the ictal/peri-ictal data set. In conclusion, the dynamic connectivity analysis revealed more functional networks related to migraine than the conventional static analysis, suggesting a substantial temporal fluctuation in functional characteristics. Our data also revealed migraine-related networks which show significant difference regardless of headache phases between patients and controls.

Melatonin as a Potential Prophylactic Therapy for Menstrual-Related Migraine Headache: A Randomized Clinical Trial

Background: Migraine is a common disabling and chronic neurological disorder affecting women aged 25 - 55 with a considerably higher frequency. It has been shown that migraine attack rates change according to the hormonal changes during the menstrual cycle. A study showed that reduced progesterone levels, especially during the end days of the luteal phase and menstruation, are associated with increased episodes of attacks in more than half of the migraine patients. Moreover, another study suggested that the melatonin level changes are positively correlated with the progesterone blood level. Previous studies indicated that the level of nocturnal urinary melatonin is lower in patients with menstrual-related migraine than in healthy subjects. Objectives: Considering the potential role of melatonin in the circadian system and its relationship with gonadal steroid blood level changes in patients, we aimed to investigate the therapeutic efficacy of melatonin in patients with menstrual-related migraines. Methods: An open-label randomized clinical trial was conducted (IR code: IRCT20121110011424N4). Patients with menstrual-related migraine referring to the Neurology Clinic of Imam Khomeini Hospital were evaluated and randomly assigned to either naproxen (250 mg every 12 hours) or melatonin (3 mg, half an hour before sleep) treatment groups. At the end of the first and third menstrual bleeding phases, the patients were assessed by a migraine diary, Visual Analog scale (VAS) for pain, and the Berlin questionnaire. Results: The study evaluated 56 patients (26 in the melatonin arm and 30 in the naproxen arm). Attack days (P < 0.001) and the headache severity (P < 0.001) improved in both groups compared to baseline. A significant difference was found between the melatonin and naproxen treatment groups in sedative and analgesic drug use (P < 0.05). Also, melatonin significantly changed the snoring rate and post-sleep tiredness compared to baseline (P < 0.05 and P < 0.05, respectively) whereas no improvement was observed in the naproxen treatment group concerning the sleep quality. Conclusions: We showed the beneficial role of melatonin in reducing the attack frequency and severity in migraine patients with menstrual-related headaches. Preventive therapy with melatonin also showed a significant reduction in the number of sedative drug use during attacks and improved the patients’ sleep quality when compared to naproxen.

Use of CGRP receptor blocker erenumab in the management of post-traumatic headache: a case series of 5 women

CONTEXT

Post-traumatic headache (PTH) is a disabling headache disorder and the most common sequela of mild traumatic brain injury. The pathophysiology of PTH is poorly understood and there is limited available evidence to guide prophylactic medication selection. Emerging understanding of the pathophysiology of migraine headaches has led to the development of monoclonal antibodies, including erenumab. Erenumab has shown promise for the prevention of primary migraine headache; however, it has not yet been studied in PTH.

CASE SERIES

five women (average age 43.0 ± 17.9y) received treatment with erenumab for PTH secondary to mTBI. The average duration of PTH prior to starting erenumab was 32.0 ± 18.2 months. All patients were taking at least one daily headache prophylactic therapy prior to erenumab. The average pre-erenumab headache intensity was 86/100. On erenumab, the average reported reduction in headache intensity was 51.1%. After starting erenumab, all five patients were able to discontinue one or more medication(s). The most common side effect was constipation (three patients). There were no serious adverse events after an average follow-up of 3.4 ± 1.5 months. One patient discontinued erenumab during this period of follow-up after the resolution of her headaches.

CONCLUSION

Erenumab appears to be safe and effective for the management of PTH.

Magnetic Resonance Imaging in Pediatric Migraine

This literature review provides an overview of the research using magnetic resonance imaging (MRI) in pediatric migraine and compares findings with the adult migraine literature. A literature search using PubMed was conducted using all relevant sources up to February 2019. Using MRI methods to categorize and explain pediatric migraine in comparison with adult migraine is important, in order to recognize and appreciate the differences between the two entities, both clinically and physiologically. We aim to demonstrate the differences and similarities between pediatric and adult migraine using data from white matter and gray matter structural studies, cerebral perfusion, metabolites, and functional MRI (fMRI) studies, including task-based and resting-state blood oxygen level-dependent studies. By doing this we identify areas that need further research, as well as possible areas where intervention could alter outcomes.

Altered resting-state functional connectivity between subregions in the thalamus and cortex in migraine without aura

BACKGROUND AND PURPOSE

Migraine is a complex and disabling neurological disorder, the exact neurological mechanisms of which remain unclear. The thalamus is considered to be the hub of the central processing and integration of nociceptive information, as well as the modulation of these processes.

METHODS

A total of 48 migraineurs without aura (MWoAs) during the interictal phase and 48 age- and sex-matched healthy controls underwent resting-state functional magnetic resonance imaging scans. We utilized masked independent component analysis and seed-based functional connectivity (FC) to investigate whether MWoAs exhibited abnormal FC between subregions in the thalamus and the cortex regions.

RESULTS

The MWoAs showed significantly weaker FC between the anterior dorsal thalamic nucleus and left precuneus. Additionally, MWoAs exhibited significantly reduced FC between the ventral posterior nucleus (VPN) and left precuneus, right inferior parietal lobule (R-IPL) and right middle frontal gyrus. Furthermore, the FC Z-scores between the VPN and R-IPL were negatively correlated with pain intensity in MWoAs. The disease duration of patients was negatively correlated with the FC Z-scores between the VPN and R-IPL.

CONCLUSION

These altered thalamocortical connectivity patterns may contribute to multisensory integration abnormalities, deficits in pain attention, cognitive evaluation and pain modulation. Pain sensitivity and disease duration are closely tied to abnormal FC between the VPN and R-IPL. Remarkably, recurrent headache attacks might contribute to this maladaptive functional plasticity closely related to pain intensity.

Cortical spreading depolarisation-induced facial hyperalgesia, photophobia and hypomotility are ameliorated by sumatriptan and olcegepant

Cortical spreading depolarisation (CSD), the neural mechanism underlying migraine aura, may cause headache by sensitising the trigeminal system. Photophobia, the most bothersome accompanying symptom during migraine attacks, is more prevalent in migraine with aura than in migraine without aura. Whether CSD plays a role in developing photophobia remains unknown. Moreover, migraine-induced physical hypoactivity contributes to loss of productivity. We aimed to investigate the development of trigeminal sensitisation, photophobia and locomotive abnormality after KCl-induced CSD using 86 male C57BL/6 mice. Sham-operated mice were used as controls. We confirmed the presence of trigeminal sensitisation and photophobia at 24 h after CSD. CSD-subjected mice also exhibited significantly reduced locomotive activity in both light and dark zones. Hence, the CSD-induced hypomobility was likely to be independent of photophobia. The 5-HT1B/1D agonist, sumatriptan, corrected all these CSD-induced abnormalities. Moreover, dose dependency was demonstrated in the ameliorating effect of the calcitonin gene-related peptide (CGRP) receptor antagonist, olcegepant, on these abnormalities. Sumatriptan and olcegepant improved mouse locomotion with therapeutic lags ranging from 20 to 30 min. Collectively, CSD caused trigeminal sensitisation, photophobia and hypomobility that persisted for at least 24 h by a mechanism involving the 5-HT1B/1D and CGRP activity.

Pharmacologic Characterization of ALD403, a Potent Neutralizing Humanized Monoclonal Antibody Against the Calcitonin Gene-Related Peptide

ALD403 is a genetically engineered, humanized immunoglobulin G1 monoclonal antibody that inhibits the action of human calcitonin gene-related peptide (CGRP). Clinical trial data indicate that ALD403 is effective as a preventive therapy for migraine and has an acceptable safety profile. For preclinical characterization of ALD403, rabbit antibodies targeting α-CGRP were humanized and modified to eliminate fragment crystallizable (Fc) γ receptor (FcγR) and complement interactions. The ability of ALD403 to inhibit CGRP-induced cAMP production was assessed using a cAMP bioassay (Meso Scale Discovery). The IC50 for inhibition of cAMP release was 434 and 288 pM with the rabbit-human chimera antibody and the humanized ALD403, respectively. ALD403 inhibited α-CGRP binding with an IC50 of 4.7 × 10-11 and 1.2 × 10-10 M for the α-CGRP and AMY1 receptors, respectively. ALD403 did not induce antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity and did not stably interact with any of the FcγR mediating these functions, exhibiting only weak binding to FcγRI. ALD403 significantly lowered capsaicin-induced blood flow responses in rodents at all time points starting at 5 minutes postapplication in a dose-dependent manner. In conclusion, ALD403 is a potent functional ligand inhibitor of α-CGRP‒driven pharmacology. SIGNIFICANCE STATEMENT: α-Calcitonin gene-related peptide blockade by ALD403 was assessed via radiolabeled ligand displacement, in vitro inhibition of cell signaling, and in vivo inhibition of capsaicin-induced vasodilation. Lack of engagement of fragment crystallizable-mediated immune-effector functions by ALD403 was shown.

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

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

The fifth cranial nerve in headaches

The fifth cranial nerve is the common denominator for many headaches and facial pain pathologies currently known. Projecting from the trigeminal ganglion, in a bipolar manner, it connects to the brainstem and supplies various parts of the head and face with sensory innervation. In this review, we describe the neuroanatomical structures and pathways implicated in the sensation of the trigeminal system. Furthermore, we present the current understanding of several primary headaches, painful neuropathies and their pharmacological treatments. We hope that this overview can elucidate the complex field of headache pathologies, and their link to the trigeminal nerve, to a broader field of young scientists.

Migraine understood as a sensory threshold disease

Migraine encompasses a broader spectrum of sensory symptoms than just headache. These "other" symptoms, eg, sensory phobias, cognitive and mood changes, allodynia, and many others indicate an altered sensitivity to sensory input which can be measured, in principle, by quantifying sensory threshold changes longitudinally over time. Photophobia, for example, can be quantified by investigating the discomfort thresholds towards the luminance of light. The aim of this review is to look into how thresholds change in patients with migraine. We performed a PubMed search up to June 2018 targeting all peer-reviewed articles evaluating the changes in threshold, sensory phobia, or sensitivity in patients with migraine. Migraineurs, in general, exhibit lower sensory thresholds compared with healthy controls. These threshold changes seem to follow the different phases during a migraine cycle. In general, thresholds reach a nadir when the headache starts (the ictal phase), rise after the headache ends, and then gradually descend towards the next attack. The sensory modality of measurement-mechanical, thermal, or nociceptive-and the location of measurement-trigeminal vs somatic dermatome-also influence the sensory threshold. Functional imaging studies provide evidence that the hypothalamo-thalamo-brainstem network may be the driving force behind the periodic threshold changes. In summary, there is evidence in the literature that migraine could be understood as a periodic sensory dysregulation originating from the brain. Nevertheless, the interstudy discrepancy is still high due to different study designs and a lack of focus on distinct migraine phases. Further well-designed and harmonized studies with an emphasis on the cyclic changes still need to be conducted.

Information Processing in Migraine: A Review of Studies on P300

Subjective cognitive dysfunction is common among migraineurs. The aim of this review is to evaluate the usefulness of psychophysiology by means of the P300 component of the event-related potential in the understanding of subtle and sub-clinical changes in cognition that may occur during and between migraine episodes. Some P300 studies suggest a potential impairment of information processing, as reflected by only few findings of interictal decreased amplitude and prolonged latency, ictal augmented amplitude and prolonged latency, changes in cognitive habituation, and limited capacity to relocate attention away from painful stimuli. P300 may represent a valuable aid for clinicians to identify patients at risk of chronicization and cognitive weakening due to neurovascular complications; in this perspective a research agenda may be planned involving larger numbers of patients undergoing psychophysiological studies.

Sensory processing patterns affect headache severity among adolescents with migraine

OBJECTIVE

To evaluate the relationship between pain catastrophizing level, sensory processing patterns, and headache severity among adolescents with episodic migraine.

BACKGROUND

Catastrophizing about pain is a critical variable in how we understand adjustment to pain and has a unique contribution in predicting pain intensity. Recent reports found that migraine is also related to enhanced sensory sensitivity. However, the relationship between pain severity, pain catastrophizing level and sensory sensitivity requires greater study especially among adolescents.

METHODS

Participants were 92 adolescents aged 13-18 years, 40 with episodic migraine and 52 healthy controls. The migraine patients were prospectively recruited from outpatient pediatric neurology clinics. All participants completed the Adolescent/Adult Sensory Profile (AASP), and the Pain Catastrophizing Scale for children (PCS-ch). The migraine groups also completed the PedMIDAS, which measures Headache related disability.

RESULTS

Adolescents with migraine had significantly lower tendency to seek sensory input than healthy controls. Elevated rumination and helplessness correlated with higher migraine pain severity. Tendency to avoid sensory input predicted the migraine related disability level. They also significantly higher pain catastrophizing level than healthy controls, as seen in enhanced rumination (p ≤ 0.001) and helplessness (p ≤ 0.05).

CONCLUSIONS

Sensory processing difficulties are common among adolescents with episodic migraine. Sensory avoidance may be related to pain experience, and pain catastrophizing and disability level.

TRIAL REGISTRATION

ISRCTN ISRCTN73824458. Registered 28 September 2014. retrospectively registered.

Impact of laser iridotomy on headache symptoms in angle-closure subjects

BACKGROUND

Migraine symptoms are frequently referred by glaucoma patients. Although most studies analyze headache in the acute setting of angle closure, many patients with chronic occludable angles also complain of headaches. The aim of this study was to determine the impact of laser peripheral iridotomy (LPI) on the magnitude and frequency of headache symptoms in patients with occludable angles.

METHODS

Prospective cohort study. Patients with indication for prophylactic LPI due to occludable iridocorneal angle were included. Headache symptoms were assessed before and at least 4 weeks after LPI using the Headache Impact Test-6 (HIT-6) questionnaire. A HIT-6 score of ≥ 50 points was labeled as a clinically significant headache.

RESULTS

Thirty-one subjects were included. Prophylactic LPI was performed in 60 eyes, as 2 patients were pseudophakic in the fellow eye. Baseline HIT-6 score was 59.9 ± 11.8, with over three quarters of these patients scoring higher than 50 points (n = 24). A statistically significant reduction in HIT-6 score was found after LPI treatment (45.4 ± 7.7, p < 0.01). Sub-analysis within the clinically symptomatic subjects disclosed a significant improvement after treatment in this group (baseline, 65.3 ± 6.2 vs post-LPI 46.2 ± 8.3, p < 0.01), with a high baseline HIT-6 score being predictive of a symptomatic improvement after LPI (χ²(8) = 15.3, p = 0.001). This is mimicked from the patient's perspective, as the two subjective questions after LPI, concerning pain intensity and frequency, report that 79.2% had a statistically significant improvement of the headaches.

CONCLUSIONS

Within our sample, the majority of patients with occludable angles had clinically relevant headaches. LPI provided symptomatic relief in the majority of those patients with high HIT-6 scores. Further studies are needed to explore the relationships between headache and angle anatomy.

Effect of propranolol with and without rosuvastatin on migraine attacks: a triple blind randomized clinical trial

Aim: To investigate the effect of rosuvastatin in combination with propranolol in reducing migraine attacks. Patients & methods: In a clinical trial study with census method, 120 patients with migraine headache were included. Patients were randomly assigned (using block randomization) to either propranolol (10 mg twice a day) with rosuvastatin (10 mg daily; intervention group [n = 60]) or propranolol (10 mg twice a day) with placebo (control [n = 60]). Results: The numbers of attacks were significantly decreased in the intervention group at the end of second, third and fourth weeks from the beginning of the intervention (p < 0.05). Conclusion: In patients with migraine, concomitant administration of propranolol (10 mg twice a day) and rosuvastatin (10 mg daily) is effective in reducing migraine attacks.

Novelty in Inflammation and Immunomodulation in Migraine

BACKGROUND

Migraine is a diffuse and disabling disease. Its pathophysiology is complex and involves both central and peripheral dysfunctions.

OBJECTIVE

This review will discuss the pathogenesis of migraine from the origin of the neuro-inflammatory theory, to the modern pathophysiological model and the latest therapies.

METHODS

PUBMED and EMBASE (up to May 2019) were searched for: migraine, inflammation, immunomodulation. An additional search was carried out from the bibliography of previous review articles.

RESULTS

Migraine was thought to be mainly a vascular disorder, according to the so-called "vascular theory". Based on animal models, a new hypothesis called "the neuro-inflammatory" was conceived at the end of the 20th century. The growing knowledge about the trigeminovascular system and its role in the inflammatory-pain pathway, allowed to identify other specific neurotransmitters, such as the Calcitonin Gene-Related Peptide and Pituitary Adenylate Cyclase-Activating Peptide. Evidence was provided that the inflammatory-pain system could become sensitised and, due to this sensitisation, the pain could also perpetuate, even in the absence of any triggers of the migraine attack. At last, brain immune cells modification during cortical spreading depression in migraine was demonstrated, along with the existence and function of the glymphatic system. The better comprehension of the immune system abnormalities allowed the development of new immunomodulating drugs: the monoclonal antibodies against the CGRP or the CGRP receptor. Moreover, new insights into the molecular mechanism of CGRP, and the function of C-fibres and Aδ-fibres, highlighted the mechanism of action of Botulinum Toxin type A in the treatment of chronic migraine.

From transformation to chronification of migraine: pathophysiological and clinical aspects

Chronic migraine is a neurological disorder characterized by 15 or more headache days per month of which at least 8 days show typical migraine features. The process that describes the development from episodic migraine into chronic migraine is commonly referred to as migraine transformation or chronification. Ample studies have attempted to identify factors associated with migraine transformation from different perspectives. Understanding CM as a pathological brain state with trigeminovascular participation where biological changes occur, we have completed a comprehensive review on the clinical, epidemiological, genetic, molecular, structural, functional, physiological and preclinical evidence available.

Neuroprotective Effect of Enriched Chicken Bone Broth as a Dietary Supplement in a Model of Migraine Mediated by Early Life Stress

Early life stress is a risk factor for development of migraine, a prevalent painful neurological disease characterized by sensitization and activation of trigeminal neurons. Secondary early life stress was previously shown to cause increased expression of neuronal proteins implicated in peripheral and central sensitization. Recently, dietary supplementation of chicken bone broth was shown to attenuate trigeminal nociception in an orofacial pain model. Accordingly, the focus of this study was to determine the effects of early life stress and dietary inclusion of bone broth on trigeminal nociceptor sensitization and activation in a model of episodic migraine. Adult Sprague-Dawley male sender rats subjected to primary traumatic stress were placed next to breeding or pregnant female rats that served as receiver rats (secondary traumatic stress) and in proximity to the offspring until weaning. Unstressed and stressed young adult offspring were tested for mechanical nocifensive response after exposure to a pungent odor known to be a migraine trigger, and in response to daily supplementation of bone broth. Early life stress promoted a primed state of trigeminal nociceptors that were activated by the pungent odor in both genders. Female animals exhibited a higher basal sensitization level and prolonged nociception compared with males. Supplementation of bone broth beginning at the time of weaning inhibited basal and triggered trigeminal mechanical sensitivity. Early life stress caused development of a sensitized trigeminal system that is implicated in migraine pathology and dietary supplementation with bone broth suppressed trigeminal sensitization, and thus may provide neuroprotective activity for reducing migraine risk.

Neurotransmitter and tryptophan metabolite concentration changes in the complete Freund's adjuvant model of orofacial pain

BACKGROUND

The neurochemical background of the evolution of headache disorders, still remains partially undiscovered. Accordingly, our aim was to further explore the neurochemical profile of Complete Freund's adjuvant (CFA)-induced orofacial pain, involving finding the shift point regarding small molecule neurotransmitter concentrations changes vs. that of the previously characterized headache-related neuropeptides. The investigated neurotransmitters consisted of glutamate, γ-aminobutyric acid, noradrenalin and serotonin. Furthermore, in light of its influence on glutamatergic neurotransmission, we measured the level of kynurenic acid (KYNA) and its precursors in the kynurenine (KYN) pathway (KP) of tryptophan metabolism.

METHODS

The effect of CFA was evaluated in male Sprague Dawley rats. Animals were injected with CFA (1 mg/ml, 50 μl/animal) into the right whisker pad. We applied high-performance liquid chromatography to determine the concentrations of the above-mentioned compounds from the trigeminal nucleus caudalis (TNC) and somatosensory cortex (ssCX) of rats. Furthermore, we measured some of these metabolites from the cerebrospinal fluid and plasma as well. Afterwards, we carried out permutation t-tests as post hoc analysis for pairwise comparison.

RESULTS

Our results demonstrated that 24 h after CFA treatment, the level of glutamate, KYNA and that of its precursor, KYN was still elevated in the TNC, all diminishing by 48 h. In the ssCX, significant concentration increases of KYNA and serotonin were found.

CONCLUSION

This is the first study assessing neurotransmitter changes in the TNC and ssCX following CFA treatment, confirming the dominant role of glutamate in early pain processing and a compensatory elevation of KYNA with anti-glutamatergic properties. Furthermore, the current findings draw attention to the limited time interval where medications can target the glutamatergic pathways.

Dawn of a New RAMPage

Receptor activity-modifying proteins (RAMPs) interact with G-protein-coupled receptors (GPCRs) to modify their functions, imparting significant implications upon their physiological and therapeutic potentials. Resurging interest in identifying RAMP-GPCR interactions has recently been fueled by coevolution studies and orthogonal technological screening platforms. These new studies reveal previously unrecognized RAMP-interacting GPCRs, many of which expand beyond Class B GPCRs. The consequences of these interactions on GPCR function and physiology lays the foundation for new molecular therapeutic targets, as evidenced by the recent success of erenumab. Here, we highlight recent papers that uncovered novel RAMP-GPCR interactions, human RAMP-GPCR disease-causing mutations, and RAMP-related human pathologies, paving the way for a new era of RAMP-targeted drug development.

Signaling Interaction between Facial and Meningeal Inputs of the Trigeminal System Mediates Peripheral Neurostimulation Analgesia in a Rat Model of Migraine

Peripheral neurostimulation within the trigeminal nerve territory has been used for pain alleviation during migraine attacks, but the mechanistic basis of this non-invasive intervention is still poorly understood. In this study, we investigated the therapeutic role of peripheral stimulation of the trigeminal nerve, which provides homosegmental innervation to intracranial structures, by assessing analgesic effects in a nitroglycerin (NTG)-induced rat model of migraine. As a result of neurogenic inflammatory responses in the trigeminal nervous system, plasma protein extravasation was induced in facial skin by applying noxious stimulation to the dura mater. Noxious chemical stimulation of the dura mater led to protein extravasation in facial cutaneous tissues and caused mechanical sensitivity. Trigeminal ganglion (TG) neurons were double-labeled via retrograde tracing to detect bifurcated axons. Extracellular recordings of wide dynamic range (WDR) neurons in the spinal trigeminal nucleus caudalis (Sp5C) demonstrated the convergence and interaction of inputs from facial tissues and the dura mater. Peripheral neurostimulation of homotopic facial tissues represented segmental pain inhibition on cephalic cutaneous allodynia in the migraine model. The results indicated that facial territories and intracranial structures were directly connected with each other through bifurcated double-labeled neurons in the TG and through second-order WDR neurons. Homotopic stimulation at the C-fiber intensity threshold resulted in much stronger inhibition of analgesia than the same intensity of heterotopic stimulation. These results provide novel evidence for the neurological bases through which peripheral neurostimulation may be effective in treating migraine in clinical practice.

Inhibition of Trigeminal Nociception by Non-invasive Vagus Nerve Stimulation: Investigating the Role of GABAergic and Serotonergic Pathways in a Model of Episodic Migraine

Migraine is a prevalent neurological disease that is characterized by unpredictable episodic attacks of intense head pain. The underlying pathology involves sensitization and activation of the trigeminal system. Although non-invasive vagus nerve stimulation (nVNS) is recommended for the treatment of migraine, the abortive mechanism of action is not well-understood. The goal of this study was to compare the ability of nVNS and sumatriptan to inhibit trigeminal activation in two animal models of episodic migraine and to investigate the receptor mechanism of action of nVNS. Nocifensive head withdrawal response was investigated in adult male Sprague Dawley rats using von Frey filaments. To induce trigeminal nociceptor sensitization, complete Freund's adjuvant was injected in the trapezius muscle and trigeminal neurons were activated by exposure to a pungent odor or injection of the nitric oxide donor sodium nitroprusside. Some animals received nVNS or sumatriptan as treatment. Some animals were injected intracisternally with antagonists of GABAA, 5-HT3 or 5-HT7 receptors prior to nVNS since these receptors are implicated in descending modulation. While unsensitized animals exposed to the pungent odor or nitric oxide alone did not exhibit enhanced mechanical nociception, sensitized animals with neck muscle inflammation displayed increased trigeminal nocifensive responses. The enhanced nociceptive response to both stimuli was attenuated by nVNS and sumatriptan. Administration of antagonists of GABAA, 5-HT3, and 5-HT7 receptors in the upper spinal cord suppressed the anti-nocifensive effect of nVNS. Our findings suggest that nVNS inhibits trigeminal activation to a similar degree as sumatriptan in episodic migraine models via involvement of GABAergic and serotonergic signaling to enhance central descending pain modulation.

Tibetan medicine Ru-yi-Zhen-bao Pills exhibits anti-migraine effect through mediating PAG anti-nociceptive channel

ETHNOPHARMACOLOGICAL RELEVANCE

Migraine is a disabling neurovascular disorder, which increases risk of cardiovascular events and is a social burden worldwide. The present first-line anti-migraine medications can cause overwhelming side-effects, of which one includes the onset of cardiovascular disease. As one of the marketed Tibetan drugs, Ru-yi-Zhen-bao Pills (RYZBP) have been clinically used to treat cardiovascular disorders and as anti-migraine medication. However, there is currently no research exploring the anti-migraine actions of RYZBP.

AIM OF THE STUDY

The current research was designed to assess the anti-migraine roles of RYZBP and explore the underlying mechanisms in a nitroglycerin (NTG)-induced migraine rat model trial.

MATERIALS AND METHODS

120 rats were randomly divided into the following six groups of 20 rats each: normal control group, model control group, positive control group, and RYZBP high/medium/low-dose groups (Ru-yi-Zhen-bao Pills; TH 1.00 g/kg, TM 0.50 g/kg and TL 0.25 g/kg). All rats were administered intragastrically for 7 consecutive days, which were subcutaneously injected with the NTG (10 mg/kg) after the last gavage (except in the normal control group). 3min after NTG treatment, 30 rats (5 rats from each group) were anesthetized and devoted to electroencephalogram(EEG) testing, which was used to evaluate the analgesic effect of RYZBP. One hour after NTG treatment, the rest of the 90 rats (15 rats from each group) were anesthetized and midbrain tissue sample was dissected. The dissection was then washed with physiological saline and collected. The histopathological changes in the periaqueductal gray(PAG) of 5 tissue samples were determined by aematoxylin-eosin (H&E) staining, as well as an estimation of substance P (SP) and neurokinin 1 receptor (NK1R) expression through immunohistochemically staining(IHC). Another 5 midbrain preparations were carried out to evaluate calcitonin gene-related peptide (CGRP), proenkephalin (PENK), SP, and cholecystokinin (CCK) expressions by real-time quantitative polymerase chain reaction (RT-qPCR). The rest of the 5 brainstem tissues were then used to measure CCK, CGRP, and opioid peptide receptor (DORR) levels by western blotting(WB).

RESULTS

In the EEG test, RYZBP (TM 0.50 g / kg) treatment transformed the EEG pain-wave of the NTG-induced migraine model rats in different time period. In the mechanism assay, compared with the model control group, RYZBP pretreatment reduced inflammatory cell infiltration, fibrosis and vacuolation of neuronal cells of PAG tissue seen by HE staining. IHC experiments further showed that RYZBPTM up-regulated SP expression levels and enhanced NK1R levels in the NTG-induced migraine rats (P < 0.05). Therapeutic administration of RYZBP also increased PENK mRNA expression and DORR protein level. Both RT-qPCR and western blotting trials indicated that RYZBP treatment significantly decreased CCK and CGRP expression levels (P < 0.01 or P < 0.05) in the NTG-induced migraine rats.

CONCLUSIONS

RYZBP has the potential to be an effective anti-migraine treatment through suppressing the EEG pain-wave, increasing the levels of SP, PENK, DORR and reducing expression of CCK and CGRP. Mediating the PAG anti-nociceptive channel and inhibiting central sensitization were the two potential mechanisms, which offers further evidence for clinical therapy.

Chronic migraine and Botulinum Toxin Type A: Where do paths cross?

Migraine is a highly prevalent and disabling disorder accounted among the primary headaches. It is the expression of a complex, and not yet fully understood, pathophysiology involving the sensitization of peripheral and central nociceptive pathways. In this review we succinctly illustrate the molecular, anatomical, and functional abnormalities underlying the migraine attack that are relevant for understanding in more depth the neurobiology behind the therapeutic effect of Botulinum Toxin Type A (BoNT-A). BoNT-A has proved effective in several neurological conditions and, more recently, also in chronic migraine. Its antimigraine mechanism of action was initially thought to be limited to the periphery and interpreted as an inhibitory activity on the processes associated to the local release of neuropeptides, with subsequent induction of peripheral sensitization. Increasing experimental evidence has become available to suggest that additional mechanisms are possibly involved, including the direct/indirect inhibition of sensitization processes in central nociceptive pathways.

Dimethyl fumarate alleviates the nitroglycerin (NTG)-induced migraine in mice

Background

Oxidative stress and inflammatory pathways are involved in migraine and endogenous antioxidant defense system has a role in the prevention of hyperalgesia in migraine. In this study, we aimed to evaluate the role of the most pharmacologically effective molecules among the fumaric acid esters (FAEs), dimethyl fumarate, nuclear factor E2-related factor 2/antioxidant response element (Nrf-2/ARE) pathway-mediated, in regulating the hypersensitivity in a mouse model of nitroglycerine (NTG)-induced migraine.

Methods

Mice were orally administered with DMF at the doses of 10, 30, and 100 mg/kg, 5 min after NTG intraperitoneal injections. We performed histological and molecular analysis on the whole brain and behavioral tests after 4 h by NTG-migraine induction. The expression of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-кB) subunit p65, nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (IκBα), inducible nitrite oxide synthase (iNOS), cyclooxygenase 2 (COX-2), Nrf-2, manganese superoxide dismutase (Mn-SOD), and heme-oxygenase-1 (HO-1) were detected by Western blot. Tail flick, hot plate, orofacial formalin, and photophobia tests were used to evaluate migraine-like pain and migraine-related light sensitivity.

Moreover, we evaluate Nrf-2-dependent mechanism by the in vitro stimulation of cells extracted by trigeminal ganglia with diethylenetriamine/nitric oxide (DETA/NO), a nitric oxide (NO) donor. The cells were pre-treated with DMF and an antagonist of Nrf-2, trigonelline (TR) 2 h before DETA/NO stimulation.

Results

DMF treatment notably reduced histological damage as showed by cresyl violet staining; also, regulating both NF-κB and Nrf-2 pathway, DMF treatment decreased the severity of inflammation and increased the protective antioxidant action. Moreover, the headache was significantly reduced. The protective effect of DMF treatment, via Nrf-2, was confirmed in in vitro studies, through inhibition of Nrf-2 by trigonelline. Cytotoxicity, iNOS, and MnSOD expression were evaluated.

Conclusion

These results provided the evidence that DMF, by Nrf-2 modulation, has a protective effect on central sensitization induced by NTG, suggesting a new insight into the potential application of DMF as novel candidates in drug development for migraine.

Fluctuations in local and widespread mechanical sensitivity throughout the migraine cycle: a prospective longitudinal study

BACKGROUND

People with migraine have localised (i.e., cephalic) mechanical sensitivity. There is uncertainty regarding widespread (i.e., extra-cephalic) mechanical sensitivity and variations in mechanical sensitivity throughout the migraine cycle. Therefore, this study aimed (1) to comprehensively assess mechanical sensitivity in both cephalic and extra-cephalic regions during the preictal, ictal, postictal and interictal phases; and (2) to compare these findings with mechanical sensitivity at corresponding time-points and locations in healthy participants.

METHODS

According to sample size calculations, 19 people with migraine and 19 matched healthy volunteers participated in a prospective longitudinal study. Pressure pain thresholds were evaluated in three cephalic regions (temporalis, upper trapezius and C1 paraspinal muscles) and two extra-cephalic regions (extensor carpi radialis and tibialis anterior muscle) with a digital algometer during the four phases of the migraine cycle in people with migraine and at corresponding intervals and locations in healthy participants. Linear mixed model analyses with a random intercept were used.

RESULTS

People with migraine had increased mechanical sensitivity in cephalic and extra-cephalic regions in all phases of the migraine cycle compared to healthy participants. Furthermore, this mechanical sensitivity was more severe in the preictal, ictal and postictal phase compared to the interictal phase in cephalic and extra-cephalic regions.

CONCLUSION

People with migraine have localised as well as widespread mechanical sensitivity compared to healthy participants. This sensitivity is even more pronounced immediately before, during and after a migraine attack.

Migraine pathways and the identification of novel therapeutic targets

Introduction: Migraine is a chronic neurovascular disorder characterized by recurrent headache attacks associated with neurological and autonomic symptoms. The pathophysiological mechanisms of the disease are extremely complex, involving hypothalamic and trigeminovascular activation, cortical spreading depression, release of pro-inflammatory peptides, peripheral and central sensitization. The underlying cellular and molecular mechanisms have been scarcely investigated. Recently, genetic studies have suggested that different metabolic pathways could be involved in the pathogenesis of migraine.Areas covered: This review focuses on cellular and molecular mechanisms involved in migraine, suggesting a role for circadian clocks, ion channels, synaptic plasticity, vascular factors, ion metal homeostasis, and impaired glucose metabolism in the pathogenesis of the disease. Accordingly, the article proposes new therapeutic targets that may be of particular relevance for disease prevention.Expert opinion: Several complex molecular mechanisms are involved in setting the genetic threshold for migraine and the pathogenesis of headache attacks. Most promising new therapeutic targets are the modulation of hypothalamic activity and ion channels involved in pain transmission. Further studies in animals and humans are necessary to enhance the elucidation of the molecular mechanisms of migraine and open new avenues for disease prevention.

Genetic variants in migraine: a field synopsis and systematic re-analysis of meta-analyses

OBJECTIVE

Numerous genetic variants from meta-analyses of observational studies and GWAS were reported to be associated with migraine susceptibility. However, due to the random errors in meta-analyses, the noteworthiness of the results showing statistically significant remains doubtful. Thus, we performed this field synopsis and re-analysis study to evaluate the noteworthiness using a Bayesian approach in hope of finding true associations.

METHODS

Relevant meta-analyses from observational studies and GWAS examining correlation between all genetic variants and migraine risk were included in our study by a PubMed search. Identification of noteworthy associations were analyzed by false-positive rate probability (FPRP) and Bayesian false discovery probability (BFDP). Using noteworthy variants, GO enrichment analysis were conducted through DAVID online tool. Then, the PPI network and hub genes were performed using STRING database and CytoHubba software.

RESULTS

As for 8 significant genetic variants from observational studies, none of which showed noteworthy at prior probability of 0.001. Out of 47 significant genetic variants in GWAS, 36 were noteworthy at prior probability of 0.000001 via FPRP or BFDP. We further found the pathways "positive regulation of cytosolic calcium ion concentration" and "inositol phosphate-mediated signaling" and hub genes including MEF2D, TSPAN2, PHACTR1, TRPM8 and PRDM16 related to migraine susceptibility.

CONCLUSION

Herein, we have identified several noteworthy variants for migraine susceptibility in this field synopsis. We hope these data would help identify novel genetic biomarkers and potential therapeutic target for migraine.

The Use of Antioxidants in the Treatment of Migraine

Despite numerous studies concerning the pathophysiology of migraine, the exact molecular mechanism of disturbances underlying migraine is still unknown. Furthermore, oxidative stress is considered to play a significant role in migraine pathogenesis. The notion of oxidative stress in migraine patients has been discussed for several decades. Over the past few years, among the substances that could potentially be used for migraine treatment, particular attention has been paid to the so-called nutraceutics, including antioxidants. Antioxidants supplied with food prevent oxidative stress by inhibiting initiation, propagation, and the oxidative chain reaction itself. Additionally, the agents used so far in the prevention of migraine indeed show some anti-oxidative action. The antioxidants discussed in the present paper are increasingly more often used by migraine patients not only due to mild or even a lack of side effects but also because of their effectiveness (decreased frequency of migraine episodes or shortening of an episode duration). The present review provides a summary of the studies on nutraceuticals with antioxidative properties.