Aura and Head pain: relationship and gaps in the translational models

Migraine and the microbiota. Can probiotics be beneficial in its prevention? - a narrative review

Migraine is a recurrent disease of the central nervous system that affects an increasing number of people worldwide causing a continuous increase in the costs of treatment. The mechanisms underlying migraine are still unclear but recent reports show that people with migraine may have an altered composition of the intestinal microbiota. It is well established that the gut-brain axis is involved in many neurological diseases, and probiotic supplementation may be an interesting treatment option for these conditions. This review collects data on the gastrointestinal and oral microbiota in people suffering from migraine and the use of probiotics as a novel therapeutic approach in its treatment.

Effects of somatostatin, a somatostatin agonist, and an antagonist, on a putative migraine trigger pathway

OBJECTIVE

To determine whether somatostatin (SST) could be a cortico-brainstem neurotransmitter involved in producing the headache of migraine.

BACKGROUND

There is evidence to support the idea that a cortico-brainstem-trigeminal nucleus neuraxis might be responsible for producing migraine headache; we have suggested that SST may be one of the neurotransmitters involved.

METHODS

Rats were anesthetised and prepared for recording neurons in either the periaqueductal gray matter (PAG) or nucleus raphe magnus (NRM), as well as the trigeminal nucleus caudalis (TNC). The dura mater and facial skin were stimulated electrically or mechanically. SST, the SST agonist L054264 and the SST antagonist CYN54806 were injected intravenously, by microinjection, or by iontophoresis into the PAG or NRM. Cortical neuronal activity was provoked by cortical spreading depression (CSD) or light flash (LF) and was monitored by recording cortical blood flow (CBF).

RESULTS

Intravenous injection of SST: (a) selectively decreased the responses of TNC neurons to stimulation of the dura, but not skin, for up to 5 h; (b) decreased the ongoing discharge rate of TNC neurons while simultaneously increasing the discharge rate of neurons in either brainstem nucleus and; (c) prevented, or reversed, the effect of CSD and LF on brainstem and trigeminal neuron discharge rates. CSD and LF decreased the discharge rate of neurons in both brainstem nuclei and increased the discharge rate of TNC neurons. These effects were reversed by L054264 and mimicked by CYN54806. Injections of L054264 into the PAG or NRM reduced the response of TNC neurons to dural stimulation and skin stimulation differentially, depending on the nucleus injected. Injections of CYN54806 into either brainstem nucleus potentiated the responses of TNC neurons to dural and skin stimulation, but without a marked differential effect.

CONCLUSIONS

These results imply that SST could be a neurotransmitter in a pathway responsible for migraine pain.

Different vulnerability of fast and slow cortical oscillations to suppressive effect of spreading depolarization: state-dependent features potentially relevant to pathogenesis of migraine aura

BACKGROUND

Spreading depolarization (SD), underlying mechanism of migraine aura and potential activator of pain pathways, is known to elicit transient local silencing cortical activity. Sweeping across the cortex, the electrocorticographic depression is supposed to underlie spreading negative symptoms of migraine aura. Main information about the suppressive effect of SD on cortical oscillations was obtained in anesthetized animals while ictal recordings in conscious patients failed to detect EEG depression during migraine aura. Here, we investigate the suppressive effect of SD on spontaneous cortical activity in awake animals and examine whether the anesthesia modifies the SD effect.

METHODS

Spectral and spatiotemporal characteristics of spontaneous cortical activity following a single unilateral SD elicited by amygdala pinprick were analyzed in awake freely behaving rats and after induction of urethane anesthesia.

RESULTS

In wakefulness, SD transiently suppressed cortical oscillations in all frequency bands except delta. Slow delta activity did not decline its power during SD and even increased it afterwards; high-frequency gamma oscillations showed the strongest and longest depression under awake conditions. Unexpectedly, gamma power reduced not only during SD invasion the recording cortical sites but also when SD occupied distant subcortical/cortical areas. Contralateral cortex not invaded by SD also showed transient depression of gamma activity in awake animals. Introduction of general anesthesia modified the pattern of SD-induced depression: SD evoked the strongest cessation of slow delta activity, milder suppression of fast oscillations and no distant changes in gamma activity.

CONCLUSION

Slow and fast cortical oscillations differ in their vulnerability to SD influence, especially in wakefulness. In the conscious brain, SD produces stronger and spatially broader depression of fast cortical oscillations than slow ones. The frequency-specific effects of SD on cortical activity of awake brain may underlie some previously unexplained clinical features of migraine aura.

Visual Aura in Non-Migraine Headaches: A Population Study

BACKGROUND

Visual aura (VA) occurs mostly in migraine with aura (MA), but some case studies have reported aura in non-migraine headaches. Thus, information of VA in non-migraine headaches is scarce. Aim of this study was to investigate the prevalence and impact of VA in non-migraine headache and compare it with that of migraine headache.

METHODS

This study was a nationwide population-based study. We used an internet-based headache diagnosis questionnaire to diagnose headache, and various modules to evaluate clinical features and comorbidities of participants with headache. We defined migraine headache as migraine and probable migraine (PM), whereas non-migraine headache was defined as a headache but not migraine or PM. VA was defined as a self-reporting VA rating scale score ≥ 3.

RESULTS

Of the 3,030 participants, 1,431 (47.2%) and 507 (16.7%) had non-migraine headache and migraine headache, respectively. VA prevalence was much lower in the non-migraine headache group than in the migraine headache group (14.5% [207/1,431] vs. 26.0% [132/507], P < 0.001). In subjects with non-migraine headache, those with VA had a markedly higher number of headache days per 30 days (median [25th-75th percentiles]: 2.0 [1.0-5.0] vs. 2.0 [1.0-3.0], P < 0.001), and headache-related disability (6.0 [3.0-16.0] vs. 2.0 [0.0-7.0], P < 0.001) than those without VA. VA prevalence did not differ significantly according to age and sex.

CONCLUSION

Non-migraine headache with VA patients had more severe symptoms than those without VA. These findings may improve the understanding of VA and the management of individuals with non-migraine headache.

Changes of migraine aura with advancing age of patients

AIM

Given the similar presentation of migraine aura and acute ischemic stroke, advancing patient age might change the characteristics of migraine with aura (MA) and be clinically important. Clinical data, however, are limited. Experimental studies indicate a decrease in the magnitude of cortical spreading depression (CSD), the pathophysiological correlate of migraine aura, with advancing age. Our study aimed to assess the influence of age on the clinical features of MA.

METHODS

Three hundred and forty-three patients were interviewed using a structured questionnaire. The questions covered the headache characteristics and symptom types including the characteristics of the C-criterion, as defined by the International Classification of Headache Disorders 3rd Edition. The association of age with MA characteristics was assessed.

RESULTS

The median age was 29 (IQR 28-52) and 235 of the 343 patients were women (69%). Individual symptoms of the C-criterion such as gradual aura spreading over longer than 5 min (P < 0.001), two or more aura symptoms occurring in succession (P = 0.005), duration of at least one MA symptom for longer than 60 min (P = 0.004), and associated headache (P = 0.01) were more frequent in younger patients. The number of symptoms including the C-characteristics decreased with increasing age (P < 0.001). Patients with sensory (P < 0.001), motor (P = 0.004) and speech disturbance (P = 0.02) were younger, and older patients with headache had less photophobia (P = 0.04) and phonophobia (P = 0.03). Sensitivity analyses yielded similar results.

CONCLUSION

The frequency of typical characteristics of migraine aura and migraine headache including photophobia and phonophobia decreases with advancing patient age. This might have potentially difficult implications for the diagnosis of MA in the elderly.

Potent dual MAGL/FAAH inhibitor AKU-005 engages endocannabinoids to diminish meningeal nociception implicated in migraine pain

BACKGROUND

Engaging the endocannabinoid system through inhibition of monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), degrading endocannabinoids (endoCBs) 2-arachidonoylglycerol (2-AG) and anandamide (AEA), was proposed as a promising approach to ameliorate migraine pain. However, the activity of MAGL and FAAH and action of endoCB on spiking activity of meningeal afferents, from which migraine pain originates, has not been explored thus far. Therefore, we here explored the analgesic effects of endoCB enhancement in rat and human meningeal tissues.

METHODS

Both MAGL and FAAH activity and local 2-AG and AEA levels were measured by activity-based protein profiling (ABPP) and LC-MS/MS, respectively, in rat meninges obtained from hemiskulls of P38-P40 Wistar rats and human meninges from elderly patients undergoing non-migraine related neurosurgery. The action on endoCBs upon administration of novel dual MAGL/FAAH inhibitor AKU-005 on meningeal afferents excitability was tested by investigating paired KCl-induced spiking and validation with local (co-)application of either AEA or 2-AG. Finally, the specific TRPV1 agonist capsaicin and blocker capsazepine were tested.

RESULTS

The basal level of 2-AG exceeded that of AEA in rat and human meninges. KCl-induced depolarization doubled the level of AEA. AKU-005 slightly increased spontaneous spiking activity whereas the dual MAGL/FAAH inhibitor significantly decreased excitation of nerve fibres induced by KCl. Similar inhibitory effects on meningeal afferents were observed with local applications of 2-AG or AEA. The action of AKU-005 was reversed by CB1 antagonist AM-251, implying CB1 receptor involvement in the anti-nociceptive effect. The inhibitory action of AEA was also reversed by AM-251, but not with the TRPV1 antagonist capsazepine. Data cluster analysis revealed that both AKU-005 and AEA largely increased long-term depression-like meningeal spiking activity upon paired KCl-induced spiking.

CONCLUSIONS

In the meninges, high anti-nociceptive 2-AG levels can tonically counteract meningeal signalling, whereas AEA can be engaged on demand by local depolarization. AEA-mediated anti-nociceptive effects through CB1 receptors have therapeutic potential. Together with previously detected MAGL activity in trigeminal ganglia, dual MAGL/FAAH inhibitor AKU-005 appears promising as migraine treatment.

Visual Disturbances Spectrum in Pediatric Migraine

Migraine is a complex neurological disorder with partially unknown pathophysiological mechanisms. The prevalence in childhood ranges from 7.7% to 17.8%, thus representing the most frequent primary headache. In half of the cases, migraine is accompanied or preceded by various neurological disturbances, among which the visual aura is the best known. In literature, other conditions, such as Alice in Wonderland Syndrome and Visual Snow syndrome, are characterized by visual manifestations and are often associated with migraine. The aim of this narrative review is to describe the spectrum of visual disturbances in pediatric migraine and their pathophysiological mechanisms.

The NMDA receptor antagonists memantine and ketamine as anti-migraine agents

Migraine is a debilitating disorder affecting females more frequently than males. There is some evidence that drugs targeting glutamate receptors: memantine and ketamine might be beneficial in the therapy of this entity. Therefore, the purpose of this work is to present NMDA receptor antagonists, memantine and ketamine, as potential anti-migraine agents. We searched PubMed/MEDLINE, Embase, and clinical trials submitted to ClinicalTrials.gov to find publications describing eligible trials published between database inception and December 31, 2021. This comprehensive literature review summarizes data on the use of the NMDA receptor antagonists memantine and ketamine in the pharmacotherapy of migraine. Results from 20 previous and recent preclinical experiments are discussed and correlated with 19 clinical trials (including case series, open-label, and randomized placebo-controlled trials). For the purposes of this review, the authors hypothesized that the propagation of SD is a major mechanism in the pathophysiology of migraine. In several animal studies and in vitro studies, memantine and ketamine inhibited or reduced propagation of the SD. In addition, the results of clinical trials suggest that memantine or ketamine may be an effective treatment option for migraine. However, most studies on these agents lack control group. Although further clinical trials are needed, the results suggest that ketamine or memantine may be promising molecules for the treatment of severe migraine. Particular attention should be paid to people who have a treatment-resistant form of migraine with aura or have exhausted existing treatment options. For them, the drugs under discussion could represent an interesting alternative in the future.

Symptoms and patterns of symptom propagation in incipient ischemic stroke and migraine aura

Background and objectives

Taking a detailed history of symptoms is important for differentiating incipient ischemic stroke and migraine aura. The aim of our study is to describe in detail symptom type and temporal pattern of symptom evolution (i.e., symptom succession and the time lapse between symptoms) and to identify differentiating clinical features in patients with ischemic stroke and migraine with aura.

Methods

Consecutive patients with ischemic stroke and migraine with aura were interviewed using a structured questionnaire. Stroke diagnosis was confirmed by imaging and migraine with aura was diagnosed according to the current criteria of the International Headache Society. Wake-up strokes and patients with severe cognitive deficits were excluded.

Results

In stroke patients and migraine patients, respectively, 50/78 (64%) vs. 123/326 (37%) had one, 18 (23%) vs. 127 (38%) had two, 5 (6%) vs. 69 (21%) had three, 2 (2%) vs. 4 (1%) had four, and 3 (3%) vs. 3 (1%) had five visual symptoms. In respect of sensory symptoms, 76/145 (52.4%) vs. 116/175 (66%) reported paresthesia and 92/145 (63.4%) vs. 132 (75%) numbness. Looking at the beginning, visual symptoms were the first symptom more often in migraine aura than in ischemic stroke (72.1 vs 18.8%, P < 0.001; PPV 86.8%). Sensory (29 vs 13.9%, P = 0.001; PPV 54.8%) and motor symptoms (20.5 vs 1.4%, P < 0.001; PPV 88.9%) were the first symptom more frequently in ischemic stroke. Of patients with consecutive symptoms, 39 of 201 (19%) compared to 34 of 117 (29%) (P = 0.02; PPV 46.6%) reported at least two simultaneous symptoms. A time lapse between symptoms of < 1 min (18.6 vs 6.3%, P < 0.001; PPV 57.1%) and > 360 min (15.8 vs 0%, χ² = 39.61, P < 0.001; PPV 100%) was more frequent in stroke whereas a time lapse between 5 and 60 min was more frequent in migraine aura (41.1 vs 68.7%, χ² = 23.52, P < 0.001; PPV 78.7%).

Conclusion

There is a significant overlap in the clinical presentation of stroke and migraine aura. In particular, a substantial proportion of patients in one group had symptoms that are traditionally attributed to the other group. This study highlights the similarities and differences between symptoms of ischemic stroke and migraine aura and challenges our reasoning in daily clinical practice.

Pathophysiology of migraine aura

Migraine aura occurs in about a third of patients with migraine and consists of a group of transient focal neurological symptoms that appear from 5 to 60min and then resolve prior to or in the early phase of a migraine headache attack. Migraine auras may consist of visual, language, unilateral sensory, or motor symptoms. There has been considerable debate as to the origins of the migrainous aura. Investigations during physiologically induced visual auras suggest that the phenomenon of cortical spreading depression or its human equivalent underpins the migraine aura. Single gene defects have been linked to relatively rare forms of the motor subtypes of aura known as familial hemiplegic migraine (FHM). These include CACNA1A (FHM1), ATP1A2 (FHM2), and SCN1A (FHM3). In the familial hemiplegic forms of migraine, the more typical forms of aura are almost always also present. Despite ample epidemiological evidence of increased heritability of migraine with aura compared to migraine without aura, identification of the specific variants driving susceptibility to the more common forms of aura has been problematic thus far. In the first genome-wide association study (GWAS) that focused migraine with aura, a single SNP rs835740 reached genome-wide significance. Unfortunately, the SNP did show statistical significance in a later meta-analysis which included GWAS data from subsequent studies. Here, we review the clinical features, pathophysiological theories, and currently available potential evidence for the genetic basis of migraine aura.

Lack of Habituation in Migraine Patients Based on High-Density EEG Analysis Using the Steady State of Visual Evoked Potential

Migraine is a periodic disorder in which a patient experiences changes in the morphological and functional brain, leading to the abnormal processing of repeated external stimuli in the inter-ictal phase, known as the habituation deficit. This is a significant feature clinically of migraine in both two types with aura or without aura and plays an essential role in studying pathophysiological differences between these two groups. Several studies indicated that the reason for migraine aura is cortical spreading depression (CSD) but did not clarify its impact on migraine without aura and lack of habituation. In this study, 22 migraine patients (MWA, N = 13), (MWoA, N = 9), and healthy controls (HC, N = 19) were the participants. Participants were exposed to the steady state of visual evoked potentials also known as (SSVEP), which are the signals for a natural response to the visual motivation at four Hz or six Hz for 2 s followed by the inter-stimulus interval that varies between 1 and 1.5 s. The order of the temporal frequencies was randomized, and each temporal frequency was shown 100 times. We recorded from 128 customized electrode locations using high-density electroencephalography (HD-EEG) and measured amplitude and habituation for the N1-P1 and P1-N2 from the first to the sixth blocks of 100 sweep features in patients and healthy controls. Using the entropy, a decrease in amplitude and SSVEP N1-P1 habituation between the first and the sixth block appeared in both MWA and MWoA (p = 0.0001, Slope = -0.4643), (p = 0.065, Slope = 0.1483), respectively, compared to HC. For SSVEP P1-N2 between the first and sixth block, it is varied in both MWA (p = 0.0029, Slope = -0.3597) and MWoA (p = 0.027, Slope = 0.2010) compared to HC. Therefore, migraine patients appear amplitude decrease and habituation deficit but with different rates between MWA, and MWoA compared to HCs. Our findings suggest this disparity between MWoA and MWA in the lack of habituation and amplitude decrease in the inter-ictal phase has a close relationship with CSD. In light of the fact that CSD manifests during the inter-ictal phase of migraine with aura, which is when migraine seizures are most likely to occur, multiple researchers have lately reached this conclusion. This investigation led us to the conclusion that CSD during the inter-ictal phase and migraine without aura are associated. In other words, even if previous research has not demonstrated it, CSD is the main contributor to both types of migraine (those with and without aura).

Inhibiting Endocannabinoid Hydrolysis as Emerging Analgesic Strategy Targeting a Spectrum of Ion Channels Implicated in Migraine Pain

Migraine is a disabling neurovascular disorder characterized by severe pain with still limited efficient treatments. Endocannabinoids, the endogenous painkillers, emerged, alternative to plant cannabis, as promising analgesics against migraine pain. In this thematic review, we discuss how inhibition of the main endocannabinoid-degrading enzymes, monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), could raise the level of endocannabinoids (endoCBs) such as 2-AG and anandamide in order to alleviate migraine pain. We describe here: (i) migraine pain signaling pathways, which could serve as specific targets for antinociception; (ii) a divergent distribution of MAGL and FAAH activities in the key regions of the PNS and CNS implicated in migraine pain signaling; (iii) a complexity of anti-nociceptive effects of endoCBs mediated by cannabinoid receptors and through a direct modulation of ion channels in nociceptive neurons; and (iv) the spectrum of emerging potent MAGL and FAAH inhibitors which efficiently increase endoCBs levels. The specific distribution and homeostasis of endoCBs in the main regions of the nociceptive system and their generation ‘on demand’, along with recent availability of MAGL and FAAH inhibitors suggest new perspectives for endoCBs-mediated analgesia in migraine pain.

The headache and aura-inducing effects of sildenafil in patients with migraine with aura

INTRODUCTION

It has not been established if migraine headache and migraine aura share common pathophysiological mechanisms. Sildenafil, a phosphodiesterase-5 inhibitor, causes cGMP accumulation and provokes migraine-like headache in patients with migraine without aura. We investigated if sildenafil induced aura and migraine-like headache in patients with migraine with aura.

METHODS

In a randomized, double-blinded, placebo-controlled crossover study, 16 patients with migraine with aura (of whom 11 patients exclusively had attacks of migraine with aura) received 100 mg sildenafil or placebo on two separate days. The development, duration, and characteristics of aura and headache were recorded using a questionnaire. The primary outcome was the incidence of migraine aura.

RESULTS

Aura symptoms were induced in three patients (19%) after sildenafil and none after placebo (P < 0.001). After administration of sildenafil, 12 patients (75%) developed headache compared with two patients (12.5%) after placebo (Fisher's exact test, P < 0.001). The headache in nine patients (56%) after sildenafil and one patient (6%) after placebo fulfilled the criteria for migraine-like attacks (Fisher's exact test, P = 0.002). All patients, who fulfilled the criteria for migraine-like attacks, reported that the attack mimicked the headache phase during their usual migraine attacks.

DISCUSSION

Sildenafil have a moderate migraine headache-inducing and a modest aura-inducing effect in patients with migraine with aura, even in those who exclusively experienced attacks of migraine with aura in their spontaneous attacks. These findings suggest that accumulation of cGMP by PDE5-inhibition do not play any significant role in the initiation of migraine aura and refute the hypothesis of sildenafil being a tool for pharmacological provocation of this phenomenon. These findings further support dissociation between the aura and the headache phase.Trial registration: ClinicalTrials.gov - NCT02795351.

Study on “Atypical” Migraine Auras in the Pediatric Age: The Role of Cortical Spreading Depression and the Physiopathogenetic Hypothesis Arising from Our Clinical Cases

Migraine is a complex neurologic disorder by which several systems of the central nervous system (autonomous system, affective, cognitive, sensory and motor system) may be affected on different levels. About a fourth of migraine patients have migraine auras. The most common aura is the visual aura followed by the sensorial aura but motor deficits, as well as deficits of higher cortical centers (disorders of thinking, orientation, coherence, or concentration), may occur as well. In analogy with a headache diary, an aura diary can deliver important help in the diagnostic process of rare migraine manifestations and prevent the under-diagnosis of unusual migraine manifestations. Complex migraine manifestations are a diagnosis of exclusion, and a broad diagnostic work-up is necessary in order to exclude dangerous neurologic pathologies. In addition, here, we discuss the atypical clinical presentation and possible physio-pathogenetic related aspects of these atypical migraine aura features in the developmental age. In addition, we wanted to stress and analyze the clinical aspects of our children/adolescents with atypical auras, which seem to be more difficult to frame with the mechanisms originally proposed to explain the physio-pathogenetic relationship between CSD and aura. Finally, we discuss in detail the complex aspects of this topic on the basis of available data and propose new terminology: “Multiple, Synchronous and Asynchronous, Cortical and Subcortical Spreading Depression”.

Cortical spreading depression induces propagating activation of the thalamus ventral posteromedial nucleus in awake mice

Background

As the relay centre for processing sensory information, the thalamus may involve in the abnormal sensory procedure caused by cortical spreading depression (CSD). However, few studies have focused on the transient response of thalamus during CSD. Our study aimed to investigate the neuronal activity of mouse thalamus ventral posteromedial nucleus (VPM) during CSD by in vivo micro-endoscopic fluorescence imaging of the genetic calcium probe GCaMP6s expressed in excitatory glutamatergic neurons.

Methods

Thirty-four transgenic VGluT2-GCaMP6s mice were used in the experiments. An endoscope was inserted into the VPM for image acquisition. CSD was induced by KCl topically applied unilaterally on the cranial dura. Data were acquired in awake (ipsilateral or contralateral VPM, saline instead of KCl, MK-801 treatment) and anaesthetized (isoflurane, pentobarbital) states. Statistical analysis was performed using analysis of variance (ANOVA) by SPSS.

Results

We found that after CSD induced in ipsilateral motor cortex, the neuronal activity increased and propagated from the posterior-lateral to the anterior-medial part of the VPM with an average speed of 3.47 mm/min. When CSD was induced in visual cortex, the response propagated in opposite direction, from the anterior-medial to the posterior-lateral part of the VPM. Aanaesthetics resulted in the suppression of VPM activation induced by CSD. No significant VPM activation was detected when CSD was induced in contralateral cortex or KCl was replaced by saline. When 5 mM MK-801 was applied to the dura, the electrode failed to record the DC shift of CSD, and there was no significant VPM activation after KCl application.

Conclusion

CSD induced propagating activation of the ipsilateral VPM in awake mice. The response might correlate to the cortical location where CSD was induced and might be affected by anaesthetics. No significant VPM activation was detected in saline and mk801 experiment results indicated that this VPM activation is due to CSD rather than mouse motion or direct effect of the KCl applying to the intact dura. This finding suggests the potential involvement of thalamus in the migraine auras.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-021-01370-z.

Cortical spreading depression and meningeal nociception

•

CSD evoked persistent activation and mechanical sensitization of dural nociceptors is likely to drive the headache phase in migraine with aura.

•

The development of neurogenic-mediated dural vasodilatation and increased plasma protein extravasation in the wake of CSD may not contribute to meningeal nociception.

•

Cortical vasoconstriction and reduced oxygen availability following CSD do not contribute to meningeal nociception.

•

Cortical neuroinflammation, involving neuronal pannexin1 and calcium-independent astrocytic signaling drive meningeal nociception following CSD.

•

CSD-related closing of K(ATP) channels and release of COX-driven prostanoids mediate the activation and sensitization of dural nociceptors respectively.

Migraine results in an enormous burden on individuals and societies due to its high prevalence, significant disability, and considerable economic costs. Current treatment options for migraine remain inadequate, and the development of novel therapies is severely hindered by the incomplete understanding of the mechanisms responsible for the pain. The sensory innervation of the cranial meninges is now considered a key player in migraine headache genesis. Recent studies have significantly advanced our understanding of some of the processes that drive meningeal nociceptive neurons, which may be targeted therapeutically to abort or prevent migraine pain. In this review we will summarize our current understanding of the mechanisms that contribute to the genesis of the headache in one migraine subtype – migraine with aura. We will focus on animal studies that address the notion that cortical spreading depression is a critical process that drives meningeal nociception in migraine with aura, and discuss recent insights into some of the proposed underlying mechanisms.

Clinical characteristics and perfusion-computed tomography alterations in a series of patients with migraine with aura attended as stroke code

OBJECTIVE

The aim of the current study was to determine the clinical characteristics of migraine with aura (MA) as well as the frequency and patterns of perfusion-computed tomography (PCT) alterations, in a series of patients with MA mimicking acute ischemic stroke.

BACKGROUND

MA is one of the most frequent stroke mimics, following seizures and psychiatric disorders. Previous case reports and short series have reported abnormal PCT patterns in patients with MA.

METHODS

We conducted a retrospective cohort study including all consecutive patients presenting with focal neurological symptoms during complete multimodal CT including baseline CT, angio-CT, and PCT with a final diagnosis of MA. We collected demographic data and clinical information about MA variables using the hospital electronic database.

RESULTS

We found 25 patients with a final diagnosis of MA among 1761 patients who attended our stroke center with complete multimodal CT (1.4% [95% CI: 0.9-2.1]). Among them, 14/25 (56%) were women, average age 38.7 years (SD 12.5), and 16/25 (64%) had a previous history of migraine. The most frequent type of aura was sensory. The median time elapsed between the onset of symptoms and CT was 171 min (IQR: 119-244). PCT alteration was found in 3/25 (12%) consisting of a hypoperfusion pattern not restricted to a vascular territory. The three patients had aphasia as the presenting symptom.

CONCLUSION

This is, to the best of our knowledge, the largest series of patients with MA managed as presumed stroke with clinical characteristics and PCT. In our study, most patients were young and had a prior history of migraine. PCT was normal in 88% of cases, with patients being still symptomatic by the time they were scanned. Further research will clarify the presence and type of PCT alterations in this entity.

Aura Mapping: Where Vision and Somatosensation Meet

While migraine auras are most frequently visual, somatosensory auras are also relatively common. Both are characterized by the spread of activation across a cortical region containing a spatial mapping of the sensory (retinal or skin) surface. When both aura types occur within a single migraine episode, they may offer an insight into the neural mechanism which underlies them. Could they both be initiated by a single neural event, or do the timing and laterality relationships between them demand multiple triggers? The observations reported here were carried out 25 years ago by a group of six individuals with migraine with aura. They timed, described and mapped their visual and somatosensory auras as they were in progress. Twenty-nine episode reports are summarized here. The temporal relationship between the onset of the two auras was quite variable within and across participants. Various forms of the cortical spreading depression hypothesis of migraine aura are evaluated in terms of whether they can account for the timing, pattern of symptom spread and laterality of the recorded auras.

Understanding the link between obesity and headache- with focus on migraine and idiopathic intracranial hypertension

BACKGROUND

Obesity confers adverse effects to every system in the body including the central nervous system. Obesity is associated with both migraine and idiopathic intracranial hypertension (IIH). The mechanisms underlying the association between obesity and these headache diseases remain unclear.

METHODS

We conducted a narrative review of the evidence in both humans and rodents, for the putative mechanisms underlying the link between obesity, migraine and IIH.

RESULTS

Truncal adiposity, a key feature of obesity, is associated with increased migraine morbidity and disability through increased headache severity, frequency and more severe cutaneous allodynia. Obesity may also increase intracranial pressure and could contribute to headache morbidity in migraine and be causative in IIH headache. Weight loss can improve both migraine and IIH headache. Preclinical research highlights that obesity increases the sensitivity of the trigeminovascular system to noxious stimuli including inflammatory stimuli, but the underlying molecular mechanisms remain unelucidated.

CONCLUSIONS

This review highlights that at the epidemiological and clinical level, obesity increases morbidity in migraine and IIH headache, where weight loss can improve headache morbidity. However, further research is required to understand the molecular underpinnings of obesity related headache in order to generate novel treatments.

Kynurenine Pathway of Tryptophan Metabolism in Migraine and Functional Gastrointestinal Disorders

Migraine, the leading cause of disability in the population aged below 50, is associated with functional gastrointestinal (GI) disorders (FGIDs) such as functional nausea, cyclic vomiting syndrome, and irritable bowel syndrome (IBS). Conversely, changes in intestinal GI transit may cause diarrhea or constipation and are a component of the autonomic symptoms associated with pre- and post-dorsal phases of migraine attack. These mutual relationships provoke a question on a common trigger in migraine and FGIDs. The kynurenine (l-kyn) pathway (KP) is the major route for l-tryptophan (l-Trp) metabolism and transforms l-Trp into several neuroactive compounds. Changes in KP were reported in both migraine and FGIDs. Migraine was largely untreatable, but several drugs approved lately by the FDA, including monoclonal antibodies for calcitonin gene-related peptide (CGRP) and its receptor, create a hope for a breakthrough in migraine treatment. Derivatives of l-kyn were efficient in pain relief with a mechanism including CGRP inhibition. KP products are important ligands to the aryl hydrocarbon receptor (AhR), whose activation is implicated in the pathogenesis of GI and migraine. Toll-like receptors (TLRs) may play a role in migraine and IBS pathogeneses, and KP metabolites detected downstream of TLR activation may be an IBS marker. The TLR4 signaling was observed in initiating and maintaining migraine-like behavior through myeloid differentiation primary response gene 88 (MyD88) in the mouse. The aim of this review is to justify the view that KP modulation may provide common triggers for migraine and FGIDs with the involvement of TLR, AhR, and MyD88 activation.

Migraine with Visual aura and the Risk of Stroke- a Narrative Review

OBJECTIVES

Patients with migraine with visual aura (MwvA) often present to eye care providers for evaluation. A thorough ophthalmological history and examination is needed to exclude ophthalmologic disorders. Additionally, it has been increasingly recognized that MwvA is associated with ischemic stroke (IS). The aim of this narrative review is to provide a comprehensive overview of the differential diagnosis of MwvA and its association with IS.

MATERIALS AND METHODS

We conducted a PubMed search using key words including "migraine aura", "visual aura without headache", "late onset migraine accompaniment", "migraine and stroke", "migraine and atrial fibrillation", and "migraine and patent foramen ovale (PFO)". We narratively summarized the main findings of the identified studies in sections including age of onset and frequency of migraine with aura, stroke subtypes, and the role of cardioembolism in the migraine-stroke association.

RESULTS AND CONCLUSION

For women younger than 50 years, MwvA is associated with an increased risk of IS, and the risk further increases in patients who also smoke and use oral contraceptives. Age of onset of MwvA 50 years or greater is associated with IS that occurs in late life. Studies reported that increased frequency of aura is associated with an increased risk of IS in women. MwvA is associated with an increased risk of cardioembolic stroke and a higher incidence of atrial fibrillation compared to migraine without aura. Most studies that assessed the migraine-stroke association were based on patients with MwvA. The risks of stroke associated with other types of migraine aura or aura without headache, as well as such association in men require further investigation. More data is needed to determine the absolute risk of stroke when evaluating MwvA in situations including smoking and low dose estrogen use, new or late onset (>50 years) MwvA, to facilitate the development of practice guidelines for stroke prevention in specific clinical scenarios.

Narrative review of neuroimaging in migraine with aura

OBJECTIVE

To improve the understanding of the role and utility of various neuroimaging modalities (clinical and research) for the evaluation of migraine aura (MA) and hemiplegic migraine during the ictal and interictal phases.

BACKGROUND

MA is defined by reversible neurologic symptoms and is considered a manifestation of a primary condition. As such, most patients with MA do not require imaging. However, if there are atypical features, change in symptom pattern, or it is a first-time presentation, neuroimaging may be used to evaluate for secondary conditions. Neuroimaging includes many modalities, and it is important to consider what information is being captured by these modalities (i.e., structural vs. functional). Imaging abnormalities may be noted both during (ictal) and between (interictal) MA attacks, and it is important for clinicians to be familiar with neuroimaging findings reported in migraine with aura (MWA) compared with other conditions.

METHODS

With the assistance of a medical librarian, we performed a review of the literature pertaining to MWA and neuroimaging in PubMed. Search terms included were magnetic resonance imaging, positron-emission tomography, single photon-emission computed tomography, functional magnetic resonance imaging, and migraine with aura. We hand-searched these references to inform our subsequent literature review.

RESULTS

Acute MA can be associated with several unique neuroimaging findings-reversible cortical diffusion restriction, cortical venous engorgement, and a "biphasic" transition from hypoperfusion to hyperperfusion. Imaging findings during MA tend to span more than one vascular territory. Between acute attacks, neuroimaging in people with MWA can resemble migraine without aura in terms of white matter abnormalities and "infarct-like lesions." Research imaging modalities such as volumetric analysis and functional imaging have demonstrated unique findings in migraine with aura.

CONCLUSION

Although migraine is a clinical diagnosis, understanding of neuroimaging findings in MWA can help clinicians interpret imaging findings and improve patient care.

Updated review on the link between cortical spreading depression and headache disorders

INTRODUCTION

Experimental animal studies have revealed mechanisms that link cortical spreading depression (CSD) to the trigeminal activation mediating lateralized headache. However, conventional CSD as seen in lissencephalic brain is insufficient to explain some clinical features of aura and migraine headache.

AREAS COVERED

The importance of CSD in headache development including dysfunction of the thalamocortical network, neuroinflammation, calcitonin gene-related peptide, transgenic models, and the role of CSD in migraine triggers, treatment options, neuromodulation and future directions are reviewed.

EXPERT OPINION

The conventional understanding of CSD marching across the hemisphere is invalid in gyrencephalic brains. Thalamocortical dysfunction and interruption of functional cortical network systems by CSD, may provide alternative explanations for clinical manifestations of migraine phases including aura. Not all drugs showing CSD blocking properties in lissencephalic brains, have efficacy in migraine headache and monoclonal antibodies against CGRP ligand/receptors which are effective in migraine treatment, have no impact on aura in humans or CSD properties in rodents. Functional networks and molecular mechanisms mediating and amplifying the effects of limited CSD in migraine brain remain to be investigated to define new targets.

Widespread brain parenchymal HMGB1 and NF-κB neuroinflammatory responses upon cortical spreading depolarization in familial hemiplegic migraine type 1 mice

Neuroinflammatory changes involving neuronal HMGB1 release and astrocytic NF-κB nuclear translocation occur following cortical spreading depolarization (CSD) in wildtype (WT) mice but it is unknown to what extent this occurs in the migraine brain. We therefore investigated in familial hemiplegic migraine type 1 (FHM1) knock-in mice, which express an intrinsic hyperexcitability phenotype, the extent of neuroinflammation without and after CSD. CSD was evoked in one hemisphere by pinprick (single CSD) or topical KCl application (multiple CSDs). Neuroinflammatory (HMGB1, NF-κB) and neuronal activation (pERK) markers were investigated by immunohistochemistry in the brains of WT and FHM1 mutant mice without and after CSD. Effects of NMDA receptor antagonism on basal and CSD-induced neuroinflammatory changes were examined by, respectively, systemically administered MK801 and ifenprodil or topical MK801 application. In FHM1 mutant mice, CSD caused enhanced neuronal HMGB1 release and astrocytic NF-κB nuclear translocation in the cortex and subcortical areas that were equally high in both hemispheres. In WT mice such effects were only pronounced in the hemisphere in which CSD was induced. Neuroinflammatory responses were associated with pERK expression indicating neuronal activation. Upon CSD, contralateral cortical and striatal HMGB1 release was reduced by topical application of MK801 in the hemisphere contralateral to the one in which CSD was induced. This study reveals that neuroinflammatory activation after CSD is widespread and extends to the contralateral hemisphere, particularly in brains of FHM1 mutant mice. Effective blockade of CSD-induced neuroinflammatory responses in the contralateral hemisphere in FHM1 mice by local NMDA receptor antagonism suggests that neuronal hyperexcitability-related neuroinflammation is relevant in migraine pathophysiology, but possibly also other neurological disorders in which spreading depolarization is involved.

Migraine Visual Aura and Cortical Spreading Depression-Linking Mathematical Models to Empirical Evidence

This review describes the subjective experience of visual aura in migraine, outlines theoretical models of this phenomenon, and explores how these may be linked to neurochemical, electrophysiological, and psychophysical differences in sensory processing that have been reported in migraine with aura. Reaction-diffusion models have been used to model the hallucinations thought to arise from cortical spreading depolarisation and depression in migraine aura. One aim of this review is to make the underlying principles of these models accessible to a general readership. Cortical spreading depolarisation and depression in these models depends on the balance of the diffusion rate between excitation and inhibition and the occurrence of a large spike in activity to initiate spontaneous pattern formation. We review experimental evidence, including recordings of brain activity made during the aura and attack phase, self-reported triggers of migraine, and psychophysical studies of visual processing in migraine with aura, and how these might relate to mechanisms of excitability that make some people susceptible to aura. Increased cortical excitability, increased neural noise, and fluctuations in oscillatory activity across the migraine cycle are all factors that are likely to contribute to the occurrence of migraine aura. There remain many outstanding questions relating to the current limitations of both models and experimental evidence. Nevertheless, reaction-diffusion models, by providing an integrative theoretical framework, support the generation of testable experimental hypotheses to guide future research.

Brain Energy Deficit as a Source of Oxidative Stress in Migraine: A Molecular Basis for Migraine Susceptibility

People with migraine are prone to a brain energy deficit between attacks, through increased energy demand (hyperexcitable brain) or decreased supply (mitochondrial impairment). However, it is uncertain how this precipitates an acute attack. Here, the central role of oxidative stress is adduced. Specifically, neurons' antioxidant defenses rest ultimately on internally generated NADPH (reduced nicotinamide adenine dinucleotide phosphate), whose levels are tightly coupled to energy production. Mitochondrial NADPH is produced primarily by enzymes involved in energy generation, including isocitrate dehydrogenase of the Krebs (tricarboxylic acid) cycle; and an enzyme, nicotinamide nucleotide transhydrogenase (NNT), that depends on the Krebs cycle and oxidative phosphorylation to function, and that works in reverse, consuming antioxidants, when energy generation fails. In migraine aura, cortical spreading depression (CSD) causes an initial severe drop in level of NADH (reduced nicotinamide adenine dinucleotide), causing NNT to impair antioxidant defense. This is followed by functional hypoxia and a rebound in NADH, in which the electron transport chain overproduces oxidants. In migraine without aura, a similar biphasic fluctuation in NADH very likely generates oxidants in cortical regions farthest from capillaries and penetrating arterioles. Thus, the perturbations in brain energy demand and/or production seen in migraine are likely sufficient to cause oxidative stress, triggering an attack through oxidant-sensing nociceptive ion channels. Implications are discussed for the development of new classes of migraine preventives, for the current use of C57BL/6J mice (which lack NNT) in preclinical studies of migraine, for how a microembolism initiates CSD, and for how CSD can trigger a migraine.

Current perspectives on neuroimaging techniques used to identify stroke mimics in clinical practice

INTRODUCTION

Urgent clinical assessment and brain imaging are essential for differentiating stroke mimics from stroke and to avoid unnecessary initiation of reperfusion and other therapies in stroke mimic patients.

AREAS COVERED

In this article, the authors will review acute stroke imaging and then the imaging patterns of the most common stroke mimics. The authors have focused our review on brain CT scan, and more specifically CT perfusion, as this is the most commonly available and emerging tool in emergency settings. The authors also provide information on acute brain MRI and MR perfusion.

EXPERT OPINION

Imaging can contribute to the detection and diagnosis of acute stroke mimics. Knowledge of imaging findings in different stroke mimics can help distinguish these from patients with stroke who require timely reperfusion therapy. CT and MRI perfusion and diffusion-weighted imaging (DWI) MRI are useful imaging modalities for the assessment of acute stroke patients as they provide more accurate information than plain CT scan. Some of these modalities should be available in the emergency setting. The authors recommended CT perfusion as a useful tool for stroke management and differentiation with stroke mimics.

Post-traumatic headache due to mild traumatic brain injury: Current knowledge and future directions

BACKGROUND/OBJECTIVE

Post-traumatic headache is one of the most common and persistent symptoms following mild traumatic brain injury. The objective of this narrative review is to provide an update on the diagnostic criteria, clinical presentation, epidemiology, pathophysiology, and treatment of post-traumatic headache, and to identify future research priorities.

METHODS

This is a narrative review of the literature regarding post-traumatic headache attributed to mild traumatic brain injury.

RESULTS

Onset of post-traumatic headache within 7 days of injury is the only evidence for a causal relationship between the injury and the headache included in the diagnostic criteria. Post-traumatic headache often resolves within the first few days of onset, whereas it persists for at least 3 months in 30-50%. The majority of insights into post-traumatic headache pathophysiology come from pre-clinical animal studies and human imaging studies, which implicate structural, functional, metabolic, and neuroinflammatory mechanisms for post-traumatic headache. There is a paucity of quality evidence for how to best treat post-traumatic headache.

CONCLUSIONS

Although meaningful progress has been made in the post-traumatic headache field, priorities for future research are numerous, including the optimization of diagnostic criteria, a greater understanding of post-traumatic headache pathophysiology, identifying mechanisms and predictors for post-traumatic headache persistence, and identifying safe, well-tolerated, effective therapies.

Transient loss of interhemispheric functional connectivity following unilateral cortical spreading depression in awake rats

OBJECTIVE

Growing evidence shows a critical role of network disturbances in the pathogenesis of migraine. Unilateral pattern of neurological symptoms of aura suggests disruption of interhemispheric interactions during the early phase of a migraine attack. Using local field potentials data from the visual and motor cortices, this study explored effects of unilateral cortical spreading depression, the likely pathophysiological mechanism of migraine aura, on interhemispheric functional connectivity in freely behaving rats.

METHODS

Temporal evolution of the functional connectivity was evaluated using mutual information and phase synchronization measures applied to local field potentials recordings obtained in homotopic points of the motor and visual cortices of the two hemispheres in freely behaving rats after induction of a single unilateral cortical spreading depression in the somatosensory S1 cortex and sham cortical stimulation.

RESULTS

Cortical spreading depression was followed by a dramatic broadband loss of interhemispheric functional connectivity in the visual and motor regions of the cortex. The hemispheric disconnection started after the end of the depolarization phase of cortical spreading depression, progressed gradually, and terminated by 5 min after initiation of cortical spreading depression. The network impairment had region- and frequency-specific characteristics and was more pronounced in the visual cortex than in the motor cortex. The period of impaired neural synchrony coincided with post-cortical spreading depression electrographic aberrant activation of the ipsilateral cortex and abnormal behavior.

CONCLUSION

The study provides the first evidence that unilateral cortical spreading depression induces a reversible loss of functional hemispheric connectivity in the cortex of awake animals. Given a critical role of long-distance cortical synchronization in sensory processing and sensorimotor integration, the post-cortical spreading depression breakdown of functional connectivity may contribute to neuropathological mechanisms of aura generation.

Thalamocortical network interruption: A fresh view for migraine symptoms

Migraine is a multifaceted brain disorder where multisensory disturbances are associated with headache. Yet sensory symptoms are conventionally justified by dysfunctions confined to the cerebral cortex, a perspective through the complex interplay of thalamocortical network would provide the entire picture, more pertinent to the central sensory processing. It is important to consider thalamus as a hub that integrates multiple domains via extensive connections among anatomically and functionally separate cortical areas. Accordingly, cortical spreading depression (CSD), implicated in migraine pathophysiology can be seen as a tool to disconnect thalamocortical network by functionally eliminating cerebral cortex. Hence, including thalamic reticular nucleus and higher order thalamic nuclei, which conveys the information transthalamically among visual, somatosensory, language and motor cortical areas, would greatly improve our current understanding of migraine.

Migraine as a Cortical Brain Disorder

PURPOSE

Migraine is an exclusively human chronic disorder with ictal manifestations characterized by a multifaceted clinical complexity pointing to a cerebral cortical involvement. The present review is aimed to cover the clinical, neuroimaging, and neurophysiological literature on the role of the cerebral cortex in migraine pathophysiology.

OVERVIEW

Converging clinical scenarios, advanced neuroimaging data, and experimental neurophysiological findings, indicate that fluctuating excitability, plasticity, and metabolism of cortical neurons represent the pathophysiological substrate of the migraine cycle. Abnormal cortical responsivity and sensory processing coupled to a mismatch between the brain's energy reserve and workload may ignite the trigeminovascular system, leading to the migraine attack through the activation of subcortical brain trigeminal and extra-trigeminal structures, and driving its propagation and maintenance.

DISCUSSION

The brain cortex emerges as the crucial player in migraine, a disorder lying at the intersection between neuroscience and daily life. Migraine disorder stems from an imbalance in inhibitory/excitatory cortical circuits, responsible for functional changes in the activity of different cortical brain regions encompassing the neurolimbic-pain network, and secondarily allowing a demodulation of subcortical areas, such as hypothalamus, amygdala, and brainstem nuclei, in a continuous mutual crosstalk.