Pathophysiology of Migraine: A Disorder of Sensory Processing

Postural instability during attacks of migraine without aura

BACKGROUND AND PURPOSE

Migraine has long been associated with unsteadiness and dizziness but postural control has not been studied in the ictal state. Here, the stability of upright stance during migraine attacks was measured.

METHODS

Static balance was assessed prospectively in migraine patients (n = 30) during quiet stance for 40 s on a posturographic force platform. Recordings were performed both ictally and in the pain-free interval. Subjects were assessed under four different conditions yielding different visual and proprioceptive feedback environments. Both ictal and interictal data were compared with age-matched healthy controls (n = 30).

RESULTS

Postural instability increased significantly under all experimental conditions during migraine attacks. Whilst standing on a foam pad with eyes closed, median sway area was 353 mm² in control subjects, 318 mm² in migraineurs in the pain-free period and 618 mm² in the ictal state. However, Romberg and vestibular Romberg quotients were not altered during migraine attacks. Spectral analyses of postural sway also showed similar profiles in migraineurs and controls. The severity of headache was inversely correlated to Romberg quotients.

CONCLUSIONS

The demonstrated pattern of balance disorder during migraine attacks suggests a transient cerebellar dysfunction. Our findings also indicate that intense headache induces a re-weighting of sensory processing toward less dependence on visual and proprioceptive information.

Inhibitory Gi/O-coupled receptors in somatosensory neurons: Potential therapeutic targets for novel analgesics

Primary sensory neurons in the dorsal root ganglia and trigeminal ganglia are responsible for sensing mechanical and thermal stimuli, as well as detecting tissue damage. These neurons express ion channels that respond to thermal, mechanical, or chemical cues, conduct action potentials, and mediate transmitter release. These neurons also express a large number of G-protein coupled receptors, which are major transducers for extracellular signaling molecules, and their activation usually modulates the primary transduction pathways. Receptors that couple to phospholipase C via heterotrimeric G_q/11 proteins and those that activate adenylate cyclase via G_s are considered excitatory; they positively regulate somatosensory transduction and they play roles in inflammatory sensitization and pain, and in some cases also in inducing itch. On the other hand, receptors that couple to G_i/o proteins, such as opioid or GABA_B receptors, are generally inhibitory. Their activation counteracts the effect of G_s-stimulation by inhibiting adenylate cyclase, as well as exerts effects on ion channels, usually resulting in decreased excitability. This review will summarize knowledge on G_i-coupled receptors in sensory neurons, focusing on their roles in ion channel regulation and discuss their potential as targets for analgesic and antipruritic medications.

Symptoms of premenstrual syndrome in female migraineurs with and without menstrual migraine

BACKGROUND

Menstrual migraine (MM) and premenstrual syndrome (PMS) are two conditions linked to specific phases of the menstrual cycle. The exact pathophysiological mechanisms are not fully understood, but both conditions are hypothesized to be triggered by female sex hormones. Co-occurrence of MM and PMS is controversial. The objective of this population-based study was to compare self-assessed symptoms of PMS in female migraineurs with and without MM. A total of 237 women from the general population who self-reported migraine in at least50% of their menstruations in a screening questionnaire were invited to a clinical interview and diagnosed by a neurologist according to the International Classification of Headache Disorders II (ICHD II), including the appendix criteria for MM. All women were asked to complete a self-administered form containing 11 questions about PMS-symptoms adapted from the Diagnostic and Statistical Manual of Mental Disorders. The number of PMS symptoms was compared among migraineurs with and without MM. In addition, each participant completed the Headache Impact test (HIT-6) and Migraine Disability Assessment Score (MIDAS).

FINDINGS

A total of 193 women returned a complete PMS questionnaire, of which 67 women were excluded from the analyses due to current use of hormonal contraception (n = 61) or because they did not fulfil the ICHD-criteria for migraine (n = 6). Among the remaining 126 migraineurs, 78 had MM and 48 non-menstrually related migraine. PMS symptoms were equally frequent in migraineurs with and without MM (5.4 vs. 5.9, p = 0.84). Women with MM reported more migraine days/month, longer lasting migraine attacks and higher HIT-6 scores than those without MM, but MIDAS scores were similar.

CONCLUSION

We did not find any difference in number of self-reported PMS-symptoms between migraineurs with and without MM.

Susceptibility of the cerebral cortex to spreading depolarization in neurological disease states: The impact of aging

Secondary injury following acute brain insults significantly contributes to poorer neurological outcome. The spontaneous, recurrent occurrence of spreading depolarization events (SD) has been recognized as a potent secondary injury mechanism in subarachnoid hemorrhage, malignant ischemic stroke and traumatic brain injury. In addition, SD is the underlying mechanism of the aura symptoms of migraineurs. The susceptibility of the nervous tissue to SD is subject to the metabolic status of the tissue, the ionic composition of the extracellular space, and the functional status of ion pumps, voltage-gated and other cation channels, glutamate receptors and excitatory amino acid transporters. All these mechanisms tune the excitability of the nervous tissue. Aging has also been found to alter SD susceptibility, which appears to be highest at young adulthood, and decline over the aging process. The lower susceptibility of the cerebral gray matter to SD in the old brain may be caused by the age-related impairment of mechanisms implicated in ion translocations between the intra- and extracellular compartments, glutamate signaling and surplus potassium and glutamate clearance. Even though the aging nervous tissue is thus less able to sustain SD, the consequences of SD recurrence in the old brain have proven to be graver, possibly leading to accelerated lesion maturation. Taken that recurrent SDs may pose an increased burden in the aging injured brain, the benefit of therapeutic approaches to restrict SD generation and propagation may be particularly relevant for elderly patients.

Increased functional connectivity between the right temporo-parietal junction and the temporal poles in migraine without aura

Rather than a localized alteration, increased visual reactivity in migraine patients seems to result from a complex interaction between several brain structures, mostly involving the ventral attention network. The hub of this network is the right temporo-parietal junction. In this report, complementing our previous findings, we describe the differences in seed-to-voxel resting-state functional connectivity seeded in the right temporo-parietal junction (right angular gyrus) between migraine patients and healthy controls. Resting-state functional MRIs of episodic migraine without aura patients in the interictal period ( n = 19) and matched healthy controls ( n = 19) were analysed. With the seed placed in the right temporo-parietal junction (right angular gyrus), seed-to-voxel connectivity was compared between groups. Electrophysiological, voxel-based morphometry (both groups) and specific region of interest (ROI)-to-ROI functional connectivity (migraine patients) data have already been published. Migraine patients showed a higher positive interaction between the right temporo-parietal junction and both temporal poles and a higher negative interaction between this same region and bilateral areas of the visual cortex. On the basis of our results, and because of their established properties as multisensory integration hubs, it is likely that the right temporo-parietal junction and both temporal poles are involved in the altered processing of sensory stimulus commonly observed in migraine patients. Therefore, more attention should be paid to these regions for migraine research in the future.

Primary Headaches

The primary headaches are composed of multiple entities that cause episodic and chronic head pain in the absence of an underlying pathologic process, disease, or traumatic injury. The most common of these are migraine, tension-type headache, and the trigeminal autonomic cephalalgias. This article reviews the clinical presentation, pathophysiology, and treatment of each to help in differential diagnosis. These headache types share many common signs and symptoms, thus a clear understanding of each helps prevent a delay in diagnosis and inappropriate or ineffective treatment. Many of these patients seek dental care because orofacial pain is a common presenting symptom.

Photophobia and sensations of dryness in patients with migraine occur independent of baseline tear volume and improve following botulinum toxin A injections

BACKGROUND

To evaluate the efficacy of botulinum toxin A (BoNT-A) in reducing photophobia and dry eye symptoms in individuals with chronic migraine. Additionally, we aimed to evaluate tear film volume as a potential contributor to symptoms in these patients.

METHODS

Retrospective review of 76 patients who received BoNT-A for chronic migraine between 23 August 2017 and 13 December 2017 at the Miami Veterans Affairs Medical Center Neurotoxin Clinic. Demographic data and all comorbidities were queried via chart review. Standardised validated surveys were administered to assess symptoms prior to and after BoNT-A injection. Preinjection tear volumes were obtained using the phenol red thread (PRT) test.

RESULTS

Preinjection migraine, photophobia and dry eye symptom scores were all significantly correlated, p<0.05, and none were associated with preinjection PRT results. After BoNT-A, improvements in migraine, photophobia and dry eye symptoms were also significantly correlated, p<0.05 and similarly did not associate with preinjection PRT results. Photophobia scores significantly improved following BoNT-A, while dry eye symptoms significantly improved in those with severe symptoms at baseline (DEQ-5 score ≥12), p=0.027. In logistic regression analysis of all individuals with dry eye symptoms (DEQ-5 ≥6), individuals with more severe dry eye symptoms were more likely improve, OR 1.27, 95% CI 1.06 to 1.51, p<0.01.

CONCLUSIONS

BoNT-A significantly improved photophobia in patients being treated for migraine and also improved dry eye symptoms in patients with severe symptoms at baseline, independent of baseline tear film volume. These improvements may be due to modulation of shared trigeminal neural pathways.

Using a Genetic Risk Score Approach to Predict Headache Response to Triptans in Migraine Without Aura

A large meta-analysis of genome-wide association studies has recently identified a number of risk loci for migraine without aura (MwoA). In this study, we tested the hypothesis that a genetic risk score based on single-nucleotide polymorphisms (SNPs), previously reported to be associated with MwoA at genome-wide significance, may influence headache response to triptans in patients with migraine without aura. Genotyping of rs9349379, rs2078371, rs6478241, rs11172113, rs1024905, and rs6724624 was conducted with a real-time PCR allelic discrimination assay in 172 MwoA patients, of whom 36.6% were inconsistent responders to triptans. Each genetic risk score model was constructed as an unweighted score, calculated by adding the number of risk alleles for MwoA across each SNP at selected loci. The association with headache response to triptans was evaluated by logistic regression analysis adjusted for triptan, and the P values were corrected for the false discovery rate. The genetic risk score including susceptibility risk alleles at TRPM8 rs6724624 and FGF6 rs1024905 was found to be inversely associated with risk of inconsistent response to triptans (OR, 0.62; 95%CI, 0.43-0.89; false discovery rate q value, 0.045). In addition, adding this genetic risk score to the triptan-adjusted logistic regression model significantly improved (P = .037) the discrimination accuracy, from 0.57 (95%CI, 0.50-0.65) to 0.64 (95%CI, 0.57-0.72). A modest but significant effect on risk of inconsistent response to triptans was identified for a genetic risk score model composed of 2 known risk alleles for MwoA, suggesting its potential utility in predicting headache response to triptan therapy.

Effects of systemic inhibitors of acid-sensing ion channels 1 (ASIC1) against acute and chronic mechanical allodynia in a rodent model of migraine

BACKGROUND AND PURPOSE

Acid-sensing ion channels (ASICs) are neuronal proton sensors emerging as potential therapeutic targets in pain of the orofacial region. Amiloride, a non-specific ASIC blocker, has been shown to exert beneficial effects in animal models of migraine and in patients. We explored the involvement of the ASIC1-subtype in cutaneous allodynia, a hallmark of migraine affecting cephalic and extra-cephalic regions in about 70% of migrainers.

EXPERIMENTAL APPROACH

We investigated the effects of systemic injections of amiloride and mambalgin-1, a specific inhibitor of ASIC1a- and ASIC1b-containing channels, on cephalic and extra-cephalic mechanical sensitivity in a rodent model of acute and chronic migraine induced by i.p. injections of isosorbide dinitrate.

KEY RESULTS

I.v. injections of these inhibitors reversed cephalic and extra-cephalic acute cutaneous mechanical allodynia in rats, a single injection inducing a delay in the subsequent establishment of chronic allodynia. Both mambalgin-1 and amiloride also reversed established chronic allodynia. The anti-allodynic effects of mambalgin-1 were not altered in ASIC1a-knockout mice, showing the ASIC1a subtype is not involved in these effects which were comparable to those of the anti-migraine drug sumatriptan and of the preventive drug topiramate on acute and chronic allodynia respectively. A single daily injection of mambalgin-1 also had a significant preventive effect on allodynia chronification.

CONCLUSIONS AND IMPLICATIONS

These pharmacological data support the involvement of peripheral ASIC1-containing channels in migraine cutaneous allodynia as well as in its chronification. They highlight the therapeutic potential of ASIC1 inhibitors as both an acute and prophylactic treatment for migraine.

Migraine and cluster headache - the common link

Although clinically distinguishable, migraine and cluster headache share prominent features such as unilateral pain, common pharmacological triggers such glyceryl trinitrate, histamine, calcitonin gene-related peptide (CGRP) and response to triptans and neuromodulation. Recent data also suggest efficacy of anti CGRP monoclonal antibodies in both migraine and cluster headache. While exact mechanisms behind both disorders remain to be fully understood, the trigeminovascular system represents one possible common pathophysiological pathway and network of both disorders. Here, we review past and current literature shedding light on similarities and differences in phenotype, heritability, pathophysiology, imaging findings and treatment options of migraine and cluster headache. A continued focus on their shared pathophysiological pathways may be important in paving future treatment avenues that could benefit both migraine and cluster headache patients.

The Effects of Chronic Stress on Migraine Relevant Phenotypes in Male Mice

Migraine is a disabling neurological disorder affecting 12% of the world’s population. Stress is a major reported trigger and exacerbator of migraine. We evaluated the effects of two chronic stress paradigms on migraine relevant phenotypes in male C57Bl/6 mice.

Methods: Fifty six mice were used in a 14 day social defeat stress (SDS) and twenty three mice were used in a 40 day chronic variable stress (CVS) paradigm. Anxiety measures were evaluated using the open field and elevated plus maze (EPM) tests. Migraine relevant phenotypes were evaluated using the nitroglycerin (NTG) and cortical spreading depression (CSD) models.

Results: Stress sensitive SDS mice and chronically stressed CVS mice showed decreased exploration in the open field and reduced time spent in the open arms of the EPM compared to controls. Stress sensitive and resilient SDS mice had increased serum corticosterone levels, and stressed mice in the CVS paradigm had decreased weight gain compared to controls, providing combined behavioral and physiological evidence of a stress response. In the CVS paradigm but not the SDS paradigm, the stressed group showed a significant decrease in baseline mechanical withdrawal threshold compared to controls. All groups showed a significant reduction in withdrawal threshold after treatment with NTG, but the reduction was not larger in SDS or CVS than in controls. Interestingly, stress resilient SDS mice showed a rapid recovery from NTG effects that was not seen in other groups. No difference in CSD frequency or velocity was seen between stress and control mice in either stress paradigms.

Conclusion: We observed distinct effects of stress on generalized pain response, migraine relevant pain, and migraine relevant excitability. CVS but not SDS was associated with a reduced mechanical withdrawal threshold, consistent with a generalized pain response to chronic stress. Neither SDS nor CVS exacerbated phenotypes considered specifically relevant to migraine - withdrawal to NTG, and susceptibility to CSD. However, the significantly reduced response of stress resilient mice to the NTG stimulus may represent a specific migraine-resistant phenotype.

There's something in the air

A 20-year-old woman presented with bilateral constant positive visual phenomenon since she was 9 years old. The symptoms had been worsening and becoming more intrusive in the last 3 years. Recently she has also had a migrainous episode. All ophthalmic and neurological investigations were normal. Her symptoms met the diagnostic criteria for visual snow. The diagnosis was explained, and the patient was reassured. Ophthalmologists and neurologists need to be aware of this condition to avoid over investigation and worsening of patient anxiety.

[Anamnestic headache in patients with cervical artery dissection: clinical characteristics and pathogenetic mechanisms]

AIM

To study the frequency and characteristics of headache which is in the past history (HPH) of patients with cervical artery dissection (CeAD) and evaluate with the help of EEG and visual evoked potentials (VEP) the role of central mechanisms in its development.

MATERIAL AND METHODS

Two hundred and twenty-seven patients with CeAD verified by neuroimaging were studied. All patients were interviewed about the presence of a headache in the past history and its features. The comparison group comprised 35 patients (mean age - 32,3±8,9 years, 77% female) with migraine. Thirty-five patients with HPH and 35 patients of the comparison group underwent EEG and VEP.

RESULTS

HPH was found in 101 patients (average age of 38.5±8.5 years, 70% female) (44.5%) out of 227 patients. In 35 patients (15.4%), HPH met the International Criteria for migraine (with aura - 3.1%, without aura - 12.3%) and in 66 patients (29.1%) did not (non-migraine headache). The latter started at the age of 24.5±10.2 years, had mild/ moderate intensity (95%), diffuse localization (68%), dull/pressing/squeezing character (53%), never accompanied by vomiting and rarely by nausea (8%), photo- phonophobia (11%). HPH, which met the migraine criteria unlike migraine in the comparison group began at a later age (19.9±9.6 vs 16.2±4.4 years, p<0.03), more frequently did not have aura (80% vs 48%, p<0.003), less often was unilateral (31% vs 71%, p<0,004) and had less intensity. The visual EEG analysis less often found rhythmic disorganization in CeAD patients with HPH than in comparison group with migraine. The hyperventilation caused a slight increase in the spectral power of Teta, Delta waves in HPH patients and significant enhancement in comparison group with migraine (p<0.05). Pattern reversal VEP in patients with HPH had a greater latency and smaller amplitude of cortical responses than in comparison group with migraine (p=0.028 and =0.037, respectively). The flash VEP amplitude was lower in HPH patients than in migraine (p=0.01).

CONCLUSION

HPH in patients with CeAD meets criteria of migraine in 15.4% (with aura - 3.1%, without aura - 12.3%), 29.1% patients have nonmigraine HPH. Central mechanisms, namely, the hypersensitivity of the cerebral cortex playing the main role in migraine pathogenesis, are not significant in HPH genesis. The main role appears to have peripheral mechanisms - dysplastic changes in the wall of extra- and intracranial arteries that predispose both to headache and dissection.

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.

Fremanezumab blocks CGRP induced dilatation in human cerebral, middle meningeal and abdominal arteries

BACKGROUND

Fremanezumab (TEV-48125) is a fully humanized anti-calcitonin gene-related peptide (CGRP) monoclonal antibody (mAb) that has shown positive results in the prevention of episodic migraine and chronic migraine. Previous preclinical studies have revealed CGRP antagonistic effects on intracranial arteries (ICA). The aim of the study was to evaluate the in vitro antagonistic effects of fremanezumab on human arteries.

METHODS

Arteries were removed in conjunction with neurosurgery (cerebral, CA, and middle meningeal artery, MMA, n = 7) or reconstructive abdominal surgery (abdominal artery, AA, n = 6). Ring segments of the vessels were mounted in a sensitive myograph, the functional responses of vasoactive intestinal peptide (VIP), substance P and CGRP in increasing concentrations (10^- 10-10^- 7 M) were studied using pre-contraction with 30 mM potassium chloride (KCl). The concentrations of fremanezumab or isotype control antibody (66.7 nM, 0.33 μM, 0.67 μM) were given 30 min prior to CGRP administration.

RESULTS

All included arteries responded with a strong stable contraction to the application of 30 mM KCl. During this pre-contraction, CGRP caused a concentration-dependent relaxation which differed slightly in maximum effect (I_max) between the types of arteries (ICA = 100%; AA 80%). Fremanezumab (66.7 nM) showed a shift in the IC₅₀ value of CGRP, but no significant change in I_max. At higher doses there was also a reduction of I_max. For AA, the I_max decreased from 71% at 66.7 nM, to 4.5% with 0.33 μM of fremanezumab. Isotype control antibody did not modify the responses. There was no effect on concentration-dependent relaxation with VIP with 66.7 nM of fremanezumab or isotype control.

CONCLUSION

CGRP relaxes pre-contracted human arteries by 80-100%, but with different IC₅₀; the potency range was ICA < AA. The antagonistic effect and potency of fremanezumab was similar, suggesting that there are vasodilatory CGRP receptors present in all studied arteries and that the antibody may have effect in all studied vessels.

The Effect of Regional Anesthetic Sphenopalatine Ganglion Block on Self-Reported Pain in Patients With Status Migrainosus

BACKGROUND

Status migrainosus (SM) is defined as a debilitating migraine attack lasting more than 72 hours in patients previously known to suffer from migraine headache. Typically, these attacks fail to respond to over the counter and abortive medications. The sphenopalatine ganglion (SPG) plays a critical role in propagating both pain and the autonomic symptoms commonly associated with migraines. SPG block via transnasal lidocaine is moderately effective in reducing migraine symptoms, but this approach is often poorly tolerated and the results are inconsistent. We proposed that an SPG block using a suprazygomatic injection approach would be a safe and effective option to abort or alleviate pain and autonomic symptoms of SM.

METHODS

Through a retrospective records review, we identified patients with a well-established diagnosis of migraine, based on the International Headache Society criteria. Patients selected for study inclusion were diagnosed with SM, had failed to respond to 2 or more abortive medications, and had received a suprazygomatic SPG block. Patients had also been asked to rate their pain on a 1-10 Likert scale, both before and 30 minutes after the injection.

RESULTS

Eighty-eight consecutive patients (20 men and 68 women) received a total of 252 suprazygomatic SPG block procedures in the outpatient headache clinic after traditional medications failed to abort their SM. At 30 minutes following the injections, there was a 67.2% (±26.6%) reduction in pain severity with a median reduction of 5 points (IQR= -6 to -3) on the Likert scale (ranging from 1 to 10). Overall, patients experienced a statistically significant reduction in pain severity (P < .0001).

CONCLUSION

The SPG is known to play an integral role in the pathophysiology of facial pain and the trigeminal autonomic cephalalgias, although its exact role in the generation and maintenance of migraine headache remains unclear. Regional anesthetic suprazygomatic SPG block is potentially effective for immediate relief of SM. We believe the procedure is simple to perform and has minimal risk.

Gain of Function for the SCN1A/hNav1.1-L1670W Mutation Responsible for Familial Hemiplegic Migraine

The SCN1A gene encodes for the voltage-dependent Na_v1.1 Na⁺ channel, an isoform mainly expressed in GABAergic neurons that is the target of hundreds of epileptogenic mutations. More recently, it has been shown that the SCN1A gene is also the target of mutations responsible for familial hemiplegic migraine (FHM-3), a rare autosomal dominant subtype of migraine with aura. Studies of these mutations indicate that they induce gain of function of the channel. Surprisingly, the mutation L1649Q responsible for pure FHM-3 showed a complete loss of function, but, when partially rescued it induced an overall gain of function because of modification of the gating properties of the mutant channel. Here, we report the characterization of the L1670W SCN1A mutation that has been previously identified in a Chinese family with pure FHM-3, and that we have identified also in a Caucasian American family with pure FHM-3. Notably, one patient in our family had severe neurological deterioration after brain radiation for cancer treatment. Functional analysis of L1670W reveals that the mutation is responsible for folding/trafficking defects and, when they are rescued by incubation at lower temperature or by expression in neurons, modifications of the gating properties lead to an overall gain of function. Therefore, L1670W is the second mutation responsible for FHM-3 with this pathophysiological mechanism, showing that it may be a recurrent mechanism for Na_v1.1 hemiplegic migraine mutations.

Evidence of an increased neuronal activation-to-resting glucose uptake ratio in the visual cortex of migraine patients: a study comparing 18FDG-PET and visual evoked potentials

BACKGROUND

Migraine attacks might be triggered by a disruption of cerebral homeostasis. During the interictal period migraine patients are characterized by abnormal sensory information processing, but this functional abnormality may not be sufficient to disrupt the physiological equilibrium of the cortex unless it is accompanied by additional pathological mechanisms, like a reduction in energetic reserves. The aim of this study was to compare resting cerebral glucose uptake (using positron emission tomography (18fluorodeoxyglucose-PET)), and visual cortex activation (using visual evoked potentials (VEP)), between episodic migraine without aura patients in the interictal period and healthy volunteers.

METHODS

Twenty episodic migraine without aura patients and twenty healthy volunteers were studied. 18FDG-PET and VEP recordings were performed on separate days. The overall glucose uptake in the visual cortex-to-VEP response ratio was calculated and compared between the groups. Additionally, PET scan comparisons adding area under the VEP curve as a covariate were performed. For case-wise analysis, eigenvalues from a specific region exhibiting significantly different FDG-PET signal in the visual cortex were extracted. Standardized glucose uptake values from this region and VEP values from each subject were then coupled and compared between the groups.

RESULTS

The mean area under the curve of VEP was greater in migraine patients compared to healthy controls. In the same line, patients had an increased neuronal activation-to-resting glucose uptake ratio in the visual cortex. Statistical parametric mapping analysis revealed that cortical FDG-PET signal in relation to VEP area under the curve was significantly reduced in migraineurs in a cluster extending throughout the left visual cortex, from Brodmann's areas 19 and 18 to area 7. Within this region, case-wise analyses showed that a visual neuronal activation exceeding glucose uptake was present in 90% of migraine patients, but in only 15% of healthy volunteers.

CONCLUSION

This study identifies an area of increased neuronal activation-to-resting glucose uptake ratio in the visual cortex of migraine patients between attacks. Such observation supports the concept that an activity-induced rupture of cerebral metabolic homeostasis may be a cornerstone of migraine pathophysiology. This article has been selected as the winner of the 2018 Enrico Greppi Award. The Enrico Greppi Award is made to an unpublished paper dealing with clinical, epidemiological, genetic, pathophysiological or therapeutic aspects of headache. Italian Society for the Study of Headaches (SISC) sponsors this award, and the award is supported through an educational grant from Teva Neuroscience. This article did not undergo the standard peer review process for The Journal of Headache and Pain. The members of the 2018 Enrico Greppi Award Selection Committee were: Francesco Pierelli, Paolo Martelletti, Lyn Griffiths, Simona Sacco, Andreas Straube and Cenk Ayata.

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.

Loss of Blood-Brain Barrier Integrity in a KCl-Induced Model of Episodic Headache Enhances CNS Drug Delivery

Cortical spreading depression (CSD) in the CNS is suggested as a common mechanism contributing to headache. Despite strong evidence for CNS involvement in headache disorders, drug development for headache disorders remains focused on peripheral targets. Difficulty in delivering drugs across the blood-brain barrier (BBB) may partially account for this disparity. It is known, however, that BBB permeability is increased during several CNS pathologies. In this study, we investigated BBB changes in response to KCl-induced CSD events and subsequent allodynia in rats. Cortical KCl injection in awake, freely moving rats produced facial allodynia with peak intensity between 1.5 and 3 h and CSD induction within 0.5-2 h postinjection. Brain perfusion of 14C-sucrose as a marker of BBB paracellular permeability revealed increased leak in the cortex, but not brainstem, beginning 0.5 h post-KCl injection and resolving within 6 h; no changes in tight junction (TJ) proteins occludin or claudin-5 expression were observed. Acute pretreatment with topiramate to inhibit CSD did not prevent the increased BBB paracellular permeability. CNS delivery of the abortive anti-migraine agent sumatriptan was increased in the cortex 1.5 h post-KCl injection. Surprisingly, sumatriptan uptake was also increased in the brainstem following CSD induction, suggesting regulation of active transport mechanisms at the BBB. Together, these results demonstrate the ability of CSD events to produce transient, time-dependent changes in BBB permeability when allodynia is present and to mediate access of clinically relevant therapeutics (i.e., sumatriptan) to the CNS.

Electrophysiological Characteristics of the Migraine Brain: Current Knowledge and Perspectives

BACKGROUND

Despite pain being its most prominent feature, migraine is primarily a disorder of sensory processing. Electrophysiology-based research in the field has consistently developed over the last fifty years.

OBJECTIVE

To summarize the current knowledge on the electrophysiological characteristics of the migraine brain, and discuss perspectives.

METHODS

We critically reviewed the literature on the topic to present and discuss articles selected on the basis of their significance and/or novelty.

RESULTS

Physiologic fluctuations within time, between-subject differences, and methodological issues account as major limitations of electrophysiological research in migraine. Nonetheless, several abnormalities revealed through different approaches have been described in the literature. Altogether, these results are compatible with an abnormal state of sensory processing.

PERSPECTIVES

The greatest contribution of electrophysiological testing in the future will most probably be the characterization of sub-groups of migraine patients sharing specific electrophysiological traits. This should serve as strategy towards personalized migraine treatment. Incorporation of novel methods of analysis would be worthwhile.

In Situ Hybridisation Study of Neuronal Neuropeptides Expression in Models of Mandibular Denervation with or without Inflammation: Injury Dependant Neuropeptide Plasticity

Neuronal expression of neuropeptides is altered following peripheral tissue injury associated with inflammation or nerve injury. This results in neuropathic pain with or without neurogenic inflammation which is a major health problem regularly seen in trigeminal neuralgia. Activation of the trigeminal system results in the release of vasoactive neuropeptides substance P and Calcitonin Gene-related Peptide (CGRP) which contribute to nociception, pain and neurogenic inflammation in injured tissues.

Transcriptional Alterations in the Trigeminal Ganglia, Nucleus and Peripheral Blood Mononuclear Cells in a Rat Orofacial Pain Model

Orofacial pain and headache disorders are among the most debilitating pain conditions. While the pathophysiological basis of these disorders may be diverse, it is generally accepted that a common mechanism behind the arising pain is the sensitization of extra- and intracranial trigeminal primary afferents. In the present study we investigated gene expression changes in the trigeminal ganglia (TRG), trigeminal nucleus caudalis (TNC) and peripheral blood mononuclear cells (PBMC) evoked by Complete Freund's Adjuvant (CFA)-induced orofacial inflammation in rats, as a model of trigeminal sensitization. Microarray analysis revealed 512 differentially expressed genes between the ipsi- and contralateral TRG samples 7 days after CFA injection. Time-dependent expression changes of G-protein coupled receptor 39 (Gpr39), kisspeptin-1 receptor (Kiss1r), kisspeptin (Kiss1), as well as synaptic plasticity-associated Lkaaear1 (Lkr) and Neurod2 mRNA were described on the basis of qPCR results. The greatest alterations were observed on day 3 ipsilaterally, when orofacial mechanical allodynia reached its maximum. This corresponded well with patterns of neuronal (Fosb), microglia (Iba1), and astrocyte (Gfap) activation markers in both TRG and TNC, and interestingly also in PBMCs. This is the first description of up- and downregulated genes both in primary and secondary sensory neurones of the trigeminovascular system that might play important roles in neuroinflammatory activation mechanisms. We are the first to show transcriptomic alterations in the PBMCs that are similar to the neuronal changes. These results open new perspectives and initiate further investigations in the research of trigeminal pain disorders.

Gray matter volume modifications in migraine

Objective

To explore cross-sectional and longitudinal gray matter (GM) volume changes in patients with migraine and their association with patients' clinical characteristics and disease activity.

Methods

Brain T2-weighted and 3-dimensional T1-weighted scans were acquired from 73 episodic migraineurs and 46 age- and sex-matched nonmigraine controls at baseline. Twenty-four migraineurs and 25 controls agreed to be reexamined after a mean follow-up of 4 years. Using a general linear model and SPM12, a whole-brain analysis was performed to assess GM volume modifications.

Results

At baseline, compared to controls, patients with migraine showed lower cerebellar GM volume and higher volume of regions of the frontotemporal lobes. At follow-up, migraineurs were significantly older than controls. Over the follow-up, migraineurs developed an increased volume of frontotemporoparietal regions, which was more prominent in patients with a higher baseline disease activity: long disease duration and high attack frequency. Migraineurs also developed decreased GM volume of visual areas, which was related to higher pain severity. Patients with an increased attack frequency at follow-up experienced both increased and decreased volume of nociceptive regions. In migraineurs, reduced GM volume of extrastriate visual areas during the follow-up was significantly correlated to baseline disease activity: shorter disease duration and lower attack frequency.

Conclusion

In this cohort, the migraine brain changes dynamically over time, and different pathophysiologic mechanisms can occur in response to patients' disease severity. The interaction between predisposing brain traits and experience-dependent responses might vary across different nociceptive and visual areas, thus leading to distinct patterns of longitudinal GM volume changes.

Efficacy of Nimodipine Plus Yufeng Ningxin Tablets for Patients with Frequent Migraine

BACKGROUND/AIMS

To test the effects of Nimodipine plus Yufeng Ningxin tablets on frequent migraine.

METHODS

Two hundred forty-two patients with frequent migraine were divided into the control group with those consuming Flunarizine (120 cases) and the treatment group with those consuming Nimodipine plus Yufeng Ningxin tablets (122 cases). The course of frequent migraine treatment lasted 7 weeks. The number of migraine days, visual analogue scale (VAS) score, and response rate were measured.

RESULTS

There was significant difference in the cure rate as the Nimodipine plus Yufeng Ningxin tablets group compared with the Flunarizine group (78.7 vs. 21.7%; p < 0.001). Fewer migraine days and VAS score were observed in the treatment group when compared with the control group (p < 0.05). Nimodipine plus Yufeng Ningxin tablets were superior to Flunarizine in terms of the response rate at week 7 (p < 0.05).

CONCLUSION

Due to its high cure rate, treatment with Nimodipine plus Yufeng Ningxin tablets is recommended to control frequent migraine, and this hypothesis needs to be confirmed through further studies conducted on a more extensive population.

The Role of Magnesium in Neurological Disorders

Magnesium is well known for its diverse actions within the human body. From a neurological standpoint, magnesium plays an essential role in nerve transmission and neuromuscular conduction. It also functions in a protective role against excessive excitation that can lead to neuronal cell death (excitotoxicity), and has been implicated in multiple neurological disorders. Due to these important functions within the nervous system, magnesium is a mineral of intense interest for the potential prevention and treatment of neurological disorders. Current literature is reviewed for migraine, chronic pain, epilepsy, Alzheimer’s, Parkinson’s, and stroke, as well as the commonly comorbid conditions of anxiety and depression. Previous reviews and meta-analyses are used to set the scene for magnesium research across neurological conditions, while current research is reviewed in greater detail to update the literature and demonstrate the progress (or lack thereof) in the field. There is strong data to suggest a role for magnesium in migraine and depression, and emerging data to suggest a protective effect of magnesium for chronic pain, anxiety, and stroke. More research is needed on magnesium as an adjunct treatment in epilepsy, and to further clarify its role in Alzheimer’s and Parkinson’s. Overall, the mechanistic attributes of magnesium in neurological diseases connote the macromineral as a potential target for neurological disease prevention and treatment.

Is selective 5-HT1F receptor agonism an entity apart from that of the triptans in antimigraine therapy?

Migraine is a neurovascular disorder that involves activation of the trigeminovascular system and cranial vasodilation mediated by release of calcitonin gene-related peptide (CGRP). The gold standard for acute migraine treatment are the triptans, 5-HT1B/1D/(1F) receptor agonists. Their actions are thought to be mediated through activation of: (i) 5-HT1B receptors in cranial blood vessels with subsequent cranial vasoconstriction; (ii) prejunctional 5-HT1D receptors on trigeminal fibers that inhibit trigeminal CGRP release; and (iii) 5-HT1B/1D/1F receptors in central nervous system involved in (anti)nociceptive modulation. Unfortunately, coronary arteries also express 5-HT1B receptors whose activation would produce coronary vasoconstriction; hence, triptans are contraindicated in patients with cardiovascular disease. In addition, since migraineurs have an increased cardiovascular risk, it is important to develop antimigraine drugs devoid of vascular (side) effects. Ditans, here defined as selective 5-HT1F receptor agonists, were developed on the basis that most of the triptans activate trigeminal 5-HT1F receptors, which may explain part of the triptans' antimigraine action. Amongst the ditans, lasmiditan: (i) fails to constrict human coronary arteries; and (ii) is effective for the acute treatment of migraine in preliminary Phase III clinical trials. Admittedly, the exact site of action is still unknown, but lasmiditan possess a high lipophilicity, which suggests a direct action on the central descending antinociceptive pathways. Furthermore, since 5-HT1F receptors are located on trigeminal fibers, they could modulate CGRP release. This review will be particularly focussed on the similarities and differences between the triptans and the ditans, their proposed sites of action, side effects and their cardiovascular risk profile.

More Than Meets the Eye: The Eye and Migraine-What You Need to Know

Migraine has long been associated with disturbances of vision, especially migraine with aura. However, the eye plays an important role in sensory processing as well. We have found that the visual quality of life is reduced in migraine. In this review, we discuss how the migraine and eye pain pathways are similar and affect many of the common complaints which are seen in ophthalmology and neuro-ophthalmology offices, such as dry eye and postoperative eye pain. We also review other related phenomena, including visual snow and photophobia, which also are related to altered sensory processing in migraine.

Phenotypic Features of Central Sensitization

PURPOSE

The current manuscript reviews approaches for phenotyping central sensitization (CS).

METHODS

The manuscript covers the concept of diagnostic phenotyping, use of endophenotypes, biomarkers, and symptom clusters. Specifically, the components of CS that include general sensory sensitivity (assessed by quantitative sensory testing) and a symptom cluster denoting sleep difficulties, pain, affect, cognitive difficulties, and low energy (S.P.A.C.E.).

RESULTS

Each of the assessment domains are described with reference to CS and their presence in chronic overlapping pain conditions (COPCs) - conditions likely influenced by CS.

CONCLUSIONS

COPCs likely represent clinical diagnostic phenotypes of CS. Components of CS can also be assessed using QST or self-report instruments designed to assess single elements of CS or more general composite indices.

Efficacy and safety of galcanezumab for the prevention of episodic migraine: Results of the EVOLVE-2 Phase 3 randomized controlled clinical trial

Introduction Galcanezumab is a humanized monoclonal antibody binding calcitonin gene-related peptide, used for migraine prevention. Methods A global, double-blind, 6-month study of patients with episodic migraine was undertaken with 915 intent-to-treat patients randomized to monthly galcanezumab 120 mg (n = 231) or 240 mg (n = 223) or placebo (n = 461) subcutaneous injections. Primary endpoint was overall mean change from baseline in monthly migraine headache days. Key secondary endpoints were ≥50%,  ≥ 75%, and 100% response rates; monthly migraine headache days with acute migraine medication use; Patient Global Impression of Severity rating; the Role Function-Restrictive score of the Migraine-Specific Quality of Life Questionnaire. Results Mean monthly migraine headache days were reduced by 4.3 and 4.2 days by galcanezumab 120 and 240 mg, respectively, and 2.3 days by placebo. The group differences (95% CIs) versus placebo were 2.0 (-2.6, -1.5) and 1.9 (-2.4, -1.4), respectively. Both doses were superior to placebo for all key secondary endpoints. Injection site pain was the most common treatment-emergent adverse event, reported at similar rates in all treatment groups. Both galcanezumab doses had significantly more injection site reactions and injection site pruritus, and the 240 mg group had significantly more injection site erythema versus placebo. Conclusions Galcanezumab 120 or 240 mg given once monthly was efficacious, safe, and well tolerated. Study identification EVOLVE-2; NCT02614196; https://clinicaltrials.gov/ct2/show/NCT02614196 . Trial Registration NCT02614196.

Non-invasive dural stimulation in mice: A novel preclinical model of migraine

BACKGROUND

Migraine is characterized by a collection of neurological symptoms in the absence of injury or damage. However, several common preclinical migraine models require significant damage to the skull to stimulate the dura mater, the likely source of afferent signaling leading to head pain. The goal of this study was to determine whether dural stimulation can be performed in mice using an injection that does not cause injury or damage.

METHODS

Using mice, injections of stimuli were administered to the dura mater through the soft tissue at the intersection between the lambdoidal and sagittal sutures. This technique did not require a permanent cannula nor did it cause damage to the skull or dura. Following injection of noxious stimuli, migraine-like behaviors were measured including cutaneous allodynia and facial grimace. The retrograde tracer fluorogold was applied onto the dura using the same injection technique to label trigeminal ganglion cell bodies, which were then testing in vitro using patch-clamp electrophysiology.

RESULTS

Dural injection of allyl-isothiocyanate, low pH, interleukin-6, or inflammatory soup but not vehicles, led to cephalic/extracephalic allodynia. Facial grimace responses were also observed with allyl-isothiocyanate, pH 6.0, and interleukin-6. Stimulation with interleukin-6 causes priming to normally subthreshold pH 7.0 stimulation of the dura following resolution of the initial interleukin-6 behavior. Systemic injection of sumatriptan at the time of dural stimulation with inflammatory soup decreased the resulting cutaneous hypersensitivity. Trigeminal ganglion cell bodies retrogradely labeled from the dura had low pH-evoked currents similar to those generated by acid-sensing ion channels.

CONCLUSION

Non-invasive dural stimulation in mice can be used as a model of migraine in the absence of injury.

Propranolol treatment prevents chronic central sensitization induced by repeated dural stimulation

Migraine is currently conceptualized as a chronic disease with episodic manifestations. In some patients, migraine attack frequency increases, leading to chronic migraine. Daily preventive therapy is initiated to decrease attack frequency. Propranolol, a first-line medication for migraine prophylaxis, reduces attack frequency in nearly 50% of patients receiving it. However, the mechanisms of its antimigraine action are unclear. We examined the effect of daily propranolol treatment (10 mg·kg per os, 8 days) in a rat model of recurrent activation of dural nociceptors (repeated infusion of an inflammatory soup (IS) on the dura through a cannula every 2-3 days). Propranolol does not abort IS-induced acute cephalic mechanical allodynia but blocks the development of a chronic cutaneous hypersensitivity upon repeated IS injections. Furthermore, propranolol prevents (1) the elevated touch-evoked Fos expression within the trigeminocervical complex, (2) enhanced both spontaneous activity, and evoked responses of second-order trigeminovascular neurons, (3) elevated touch-evoked rostral ventromedial medulla and locus coeruleus Fos expression and (4) diffuse noxious inhibitory controls impairment, induced by repeated IS injections. Our results suggest that propranolol exerts its prophylactic action, at least in part, by blocking the chronic sensitization of descending controls of pain, arising from the rostral ventromedial medulla and locus coeruleus, and in turn preventing the maintenance of a state of facilitated trigeminovascular transmission within the trigeminocervical complex. Assessing changes in these brain areas has the potential to elucidate the mechanisms for migraine transformation and to reveal novel biological and molecular targets for specific migraine-preventive therapies.

Phase 1, randomized, parallel-group, double-blind, placebo-controlled trial to evaluate the effects of erenumab (AMG 334) and concomitant sumatriptan on blood pressure in healthy volunteers

OBJECTIVES

The aim of this study was to assess the effects of concomitant administration of erenumab and sumatriptan on resting blood pressure, pharmacokinetics, safety, and tolerability in healthy subjects.

METHODS

In this phase 1, parallel-group, one-way crossover, double-blind, placebo-controlled study, healthy adult subjects were randomized (1:2) to receive either intravenous placebo and subcutaneous sumatriptan 12 mg (i.e. two 6-mg injections separated by 1 hour) or intravenous erenumab 140 mg and subcutaneous sumatriptan 12 mg. Blood pressure was measured pre-dose and at prespecified times post-dose. The primary endpoint was individual time-weighted averages of mean arterial pressure, measured from 0 hours to 2.5 hours after the first dose of sumatriptan. Pharmacokinetic parameters for sumatriptan were evaluated by calculating geometric mean ratios (erenumab and sumatriptan/placebo and sumatriptan). Adverse events and anti-erenumab antibodies were also evaluated.

RESULTS

A total of 34 subjects were randomized and included in the analysis. Least squares mean (standard error) time-weighted averages of mean arterial pressure were 87.4 (1.0) mmHg for the placebo and sumatriptan group and 87.4 (1.2) mmHg for the erenumab and sumatriptan group. Mean difference in mean arterial pressure between groups was -0.04 mmHg (90% confidence interval: -2.2, 2.1). Geometric mean ratio estimates for maximum plasma concentration of sumatriptan was 0.95 (90% confidence interval: 0.82, 1.09), area under the plasma concentration-time curve (AUC) from time 0 to 6 hours was 0.98 (90% confidence interval: 0.93, 1.03), and AUC from time 0 to infinity was 1.00 (90% confidence interval: 0.96, 1.05). No clinically relevant safety findings for co-administration of sumatriptan and erenumab were identified.

CONCLUSION

Co-administration of erenumab and sumatriptan had no additional effect on resting blood pressure or on pharmacokinetics of sumatriptan. Trial registration: ClinicalTrials.gov, NCT02741310.

Effect of Fremanezumab Compared With Placebo for Prevention of Episodic Migraine: A Randomized Clinical Trial

IMPORTANCE

Fremanezumab, a fully humanized monoclonal antibody that targets calcitonin gene-related peptide, may be effective for treating episodic migraine.

OBJECTIVE

To assess the efficacy of fremanezumab compared with placebo for prevention of episodic migraine with a monthly dosing regimen or a single higher dose.

DESIGN AND SETTING

Randomized, double-blind, placebo-controlled, parallel-group trial conducted at 123 sites in 9 countries from March 23, 2016 (first patient randomized), to April 10, 2017, consisting of a screening visit, 28-day pretreatment period, 12-week treatment period, and final evaluation at week 12.

PARTICIPANTS

Study participants were aged 18 to 70 years with episodic migraine (6-14 headache days, with at least 4 migraine days, during 28-day pretreatment period). Patients who had previous treatment failure with 2 classes of migraine-preventive medication were excluded.

INTERVENTIONS

Patients were randomized 1:1:1 to receive subcutaneous monthly dosing of fremanezumab (n = 290; 225 mg at baseline, week 4, and week 8); a single higher dose of fremanezumab, as intended to support a quarterly dose regimen (n = 291; 675 mg of fremanezumab at baseline; placebo at weeks 4 and 8); or placebo (n = 294; at baseline, week 4, and week 8).

MAIN OUTCOMES AND MEASURES

The primary end point was mean change in mean number of monthly migraine days during the 12-week period after the first dose.

RESULTS

Among 875 patients who were randomized (mean age, 41.8 [SD, 12.1] years; 742 women [85%]), 791 (90.4%) completed the trial. From baseline to 12 weeks, mean migraine days per month decreased from 8.9 days to 4.9 days in the fremanezumab monthly dosing group, from 9.2 days to 5.3 days in the fremanezumab single-higher-dose group, and from 9.1 days to 6.5 days in the placebo group. This resulted in a difference with monthly dosing vs placebo of -1.5 days (95% CI, -2.01 to -0.93 days; P < .001) and with single higher dosing vs placebo of -1.3 days (95% CI, -1.79 to -0.72 days; P < .001). The most common adverse events that led to discontinuation were injection site erythema (n = 3), injection site induration (n = 2), diarrhea (n = 2), anxiety (n = 2), and depression (n = 2).

CONCLUSIONS AND RELEVANCE

Among patients with episodic migraine in whom multiple medication classes had not previously failed, subcutaneous fremanezumab, compared with placebo, resulted in a statistically significant 1.3- to 1.5-day reduction in the mean number of monthly migraine days over a 12-week period. Further research is needed to assess effectiveness against other preventive medications and in patients in whom multiple preventive drug classes have failed and to determine long-term safety and efficacy.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02629861.

Redox Mechanisms in Migraine: Novel Therapeutics and Dietary Interventions

SIGNIFICANCE

Migraine represents the third most prevalent and the seventh most disabling human disorder. Approximately 30% of migraine patients experience transient, fully reversible, focal neurological symptoms (aura) preceding the attack. Recent Advances: Awareness of the hypothesis that migraine actually embodies a spectrum of illnesses-ranging from episodic to chronic forms-is progressively increasing and poses novel challenges for clarifying the underlying pathophysiological mechanisms of migraine as well as for the development of novel therapeutic interventions. Several theories have evolved to the current concept that a combination of genetic, epigenetic, and environmental factors may play a role in migraine pathogenesis, although their relative importance is still being debated.

CRITICAL ISSUES

One critical issue that deserves a particular attention is the role of oxidative stress in migraine. Indeed, potentially harmful oxidative events occur during the migraine attack and long-lasting or frequent migraine episodes may increase brain exposure to oxidative events that can lead to chronic transformation. Moreover, a wide variety of dietary, environmental, physiological, behavioral, and pharmacological migraine triggers may act through oxidative stress, with clear implications for migraine treatment and prophylaxis. Interestingly, almost all current prophylactic migraine agents exert antioxidant effects.

FUTURE DIRECTIONS

Increasing awareness of the role of oxidative stress and/or decreased antioxidant defenses in migraine pathogenesis and progression to a chronic condition lays the foundations for the design of novel prophylactic approaches, which, by reducing brain oxidative phenomena, could favorably modify the clinical course of migraine. Antioxid. Redox Signal. 28, 1144-1183.

Flunarizine in migraine-related headache prevention: results from 200 patients treated in the UK

BACKGROUND AND PURPOSE

For over 20 years, as a group we have been using flunarizine in primary headache disorders. Flunarizine is widely used in Europe, but not licensed in the UK. In September 2014, the National Institute for Clinical Excellence published supportive guidelines for flunarizine use in migraine, based on randomized controlled evidence that it is as effective as propranolol and topiramate in adults.

METHODS

We reviewed a cohort of adult patients (n = 200) treated with flunarizine from our practice. The clinical information of these patients, i.e. diagnosis, dose, efficacy, side effects and duration of treatment, was collected.

RESULTS

The most common indication for flunarizine use was chronic migraine, followed by migraine with aura, sporadic hemiplegic migraine, familial hemiplegic migraine and new daily persistent headache with migrainous features. Flunarizine was generally effective, with only 24% (n = 47) of patients reporting no clinical effect. The most common dose used was 10 mg per day. Duration of treatment information was available for 39% (n = 78) of patients. Of these patients, 64% (n = 50) continued treatment for more than 1 year. Doses up to 15 mg were generally well tolerated, with only 10.5% (n = 21) of patients stopping treatment due to adverse effects. The most common adverse events were tiredness, mood change and weight gain.

CONCLUSION

The data provide supportive evidence from tertiary headache practice in the UK for the use of flunarizine in migraine. The data encourages development of future guidance regarding flunarizine use in headache centres in countries where its use is not routine.

Vascular and molecular pharmacology of the metabolically stable CGRP analogue, SAX

The main purpose of this study was to compare in vitro pharmacological properties of human αCGRP (CGRP) and a recently discovered metabolically stable CGRP analogue, SAX, in isolated rat and human artery segments. In rat, CGRP and SAX induced similar vasodilatory responses in isolated mesenteric artery with the potency of SAX being lower than that of CGRP (vasodilatory pEC₅₀ 8.2 ± 0.12 and 9.0 ± 0.11, respectively). A corresponding difference in receptor binding affinity of SAX and CGRP was determined in rat cerebral membranes (pKi 8.3 ± 0.19 and 9.3 ± 0.14, respectively). CGRP and SAX-induced vasodilation was antagonised with similar potencies by the CGRP receptor antagonist BIBN4096BS supporting a uniform receptor population for the agonists. In human tissue, SAX and CGRP induced similar pharmacological responses with different potencies in subcutaneous artery (vasodilatory pEC₅₀ 8.8 ± 0.18 and 9.5 ± 0.13, respectively) and human recombinant receptors (cAMP signalling pEC₅₀ 9.1 ± 0.16 and 10.2 ± 0.19). Like in the rat mesenteric artery, both SAX and CGRP-responses were inhibited by the CGRP receptor antagonist BIBN4096BS with similar antagonistic potencies. In conclusion, all pharmacological characteristics of SAX and CGRP in human and rat sources points towards action via a uniform BIBN4096BS sensitive receptor population with the potency of SAX being 5-10 fold lower than that of CGRP.

CGRP – a target for acute therapy in migraine: Clinical data

Background

A better understanding of the mechanisms underlying the migraine attack has reinforced the concept that migraine is a complex brain disease, and has paved the way for the development of new migraine specific acute treatments. In recent years, targeting the calcitonin gene-related peptide and its receptors has been one of the most promising pharmacological strategies for both acute and preventive treatment of migraine.

Findings

Randomized double-blind placebo-controlled trials have demonstrated the superiority of small molecule calcitonin gene-related peptide receptor antagonists (gepants) over placebo in treating acute migraine attacks measured as the two-hour pain free endpoint. Gepants also improved migraine associated symptoms, such as nausea, photophobia and phonophobia. Two of the class have had their development stopped because of hepatotoxicity, which is emerging as being due to metabolites. Gepants have a good tolerability and can be safely used in patients with stable cardiovascular disease.

Conclusion

Exciting results have been obtained targeting the calcitonin gene-related peptide pathway to abort acute migraine attacks, thus reinforcing the relevance of mechanism-based treatments specific for migraine.

The Evidence for the Role of Nutraceuticals in the Management of Pediatric Migraine: a Review

PURPOSE OF REVIEW

Nutraceuticals are a form of complementary and alternative medicine that is commonly used by children and adolescents with migraine. In this review, observational studies, randomized controlled trials, systematic reviews, and meta-analyses on the efficacy and safety of single compound nutraceuticals for the management of migraine in children and adolescents were identified through a literature search of MEDLINE, Embase, and EBM Reviews-Cochrane Central Register of Controlled Trials.

RECENT FINDINGS

Twenty-one studies were reviewed, of which 11 were observational studies, 7 were randomized controlled trials, and 3 were systematic reviews. Six different nutraceuticals were included in the review: vitamin D, riboflavin, coenzyme Q10, magnesium, butterbur, and polyunsaturated fatty acids. All but three of the studies assessed the role of nutraceuticals in migraine prevention, while three studies evaluated the role of intravenous magnesium for acute migraine management. Overall, the quality and size of the studies were limited. Due to low quality evidence and limited studies, no definite conclusions can be drawn on the efficacy of nutraceuticals for the treatment of pediatric migraine. Future studies are warranted in order to establish evidence upon which to define the role of nutraceuticals in this patient population.

Current Prophylactic Medications for Migraine and Their Potential Mechanisms of Action

A relatively high number of different medications is currently used for migraine prevention in clinical practice. Although these compounds were initially developed for other indications and differ in their mechanisms of action, some general themes can be identified from the mechanisms at play. Efficacious preventive drugs seem to either suppress excitatory nervous signaling via sodium and/or calcium receptors, facilitate GABAergic inhibition, reduce neuronal sensitization, block cortical spreading depression and/or reduce circulating levels of CGRP. We here review such mechanisms for the different compounds.