Migraine aura and related phenomena: beyond scotomata and scintillations

Clinical features of migraine with aura: a REFORM study

BACKGROUND

About one-third of persons with migraine experience transient neurologic symptoms, referred to as aura. Despite its widespread prevalence, comprehensive clinical descriptions of migraine with aura remain sparse. Therefore, we aimed to provide an in-depth phenotypic analysis of aura symptoms and characteristics in a cross-sectional study of a large sample of adults diagnosed with migraine with aura.

METHODS

Data were extracted from the baseline characteristics of participants in the Registry for Migraine (REFORM) study - a single-center, prospective, longitudinal cohort study. Participants were adults diagnosed with migraine aura, reporting ≥ 4 monthly migraine days in the preceding 3 months. Trained personnel conducted in-person semi-structured interviews, capturing details on the nature, duration, localization, and progression of individual aura symptoms.

RESULTS

Of the 227 enrolled participants with migraine with aura, the mean age was 41.1 years, with a predominant female representation (n = 205 [90.3%]). Visual aura was present in 215 (94.7%) participants, somatosensory aura in 81 (35.7%), and speech and/or language aura in 31 (13.7%). A single type of aura was observed in 148 (65.2%) participants, whilst 79 (34.8%) reported multiple aura types. Most participants (n = 220 [96.9%]) described their aura symptoms as positive or gradually spreading. Headache in relation to aura was noted by 218 (96.0%) participants, with 177 (80.8%) stating that the onset of aura symptoms preceded the onset of headache.

CONCLUSIONS

This study offers a detailed clinical depiction of persons with migraine with aura, who were predominantly enrolled from a tertiary care unit. The findings highlight potential gaps in the available literature on migraine with aura and should bolster clinicians' acumen in diagnosing migraine with aura in clinical settings.

Astrocytes as critical players of the fine balance between inhibition and excitation in the brain: spreading depolarization as a mechanism to curb epileptic activity

Spreading depolarizations (SD) are slow waves of complete depolarization of brain tissue followed by neuronal silencing that may play a role in seizure termination. Even though SD was first discovered in the context of epilepsy research, the link between SD and epileptic activity remains understudied. Both seizures and SD share fundamental pathophysiological features, and recent evidence highlights the frequent occurrence of SD in experimental seizure models. Human data on co-occurring seizures and SD are limited but suggestive. This mini-review addresses possible roles of SD during epileptiform activity, shedding light on SD as a potential mechanism for terminating epileptiform activity. A common denominator for many forms of epilepsy is reactive astrogliosis, a process characterized by morphological and functional changes to astrocytes. Data suggest that SD mechanisms are potentially perturbed in reactive astrogliosis and we propose that this may affect seizure pathophysiology.

Prosopagnosia: face blindness and its association with neurological disorders

Loss of facial recognition or prosopagnosia has been well-recognized for over a century. It has been categorized as developmental or acquired depending on whether the onset is in early childhood or beyond, and acquired cases can have degenerative or non-degenerative aetiologies. Prosopagnosia has been linked to involvement of the fusiform gyri, mainly in the right hemisphere. The literature on prosopagnosia comprises case reports and small case series. We aim to assess demographic, clinical and imaging characteristics and neurological and neuropathological disorders associated with a diagnosis of prosopagnosia in a large cohort. Patients were categorized as developmental versus acquired; those with acquired prosopagnosia were further subdivided into degenerative versus non-degenerative, based on neurological aetiology. We assessed regional involvement on [18F] fluorodeoxyglucose-PET and MRI of the right and left frontal, temporal, parietal and occipital lobes. The Intake and Referral Center at the Mayo Clinic identified 487 patients with possible prosopagnosia, of which 336 met study criteria for probable or definite prosopagnosia. Ten patients, 80.0% male, had developmental prosopagnosia including one with Niemann-Pick type C and another with a forkhead box G1 gene mutation. Of the 326 with acquired prosopagnosia, 235 (72.1%) were categorized as degenerative, 91 (27.9%) as non-degenerative. The most common degenerative diagnoses were posterior cortical atrophy, primary prosopagnosia syndrome, Alzheimer's disease dementia and semantic dementia, with each diagnosis accounting for >10% of this group. The most common non-degenerative diagnoses were infarcts (ischaemic and haemorrhagic), epilepsy-related and primary brain tumours, each accounting for >10%. We identified a group of patients with non-degenerative transient prosopagnosia in which facial recognition loss improved or resolved over time. These patients had migraine-related prosopagnosia, posterior reversible encephalopathy syndrome, delirium, hypoxic encephalopathy and ischaemic infarcts. On [18F] fluorodeoxyglucose-PET, the temporal lobes proved to be the most frequently affected regions in 117 patients with degenerative prosopagnosia, while in 82 patients with non-degenerative prosopagnosia, MRI revealed the right temporal and right occipital lobes as most affected by a focal lesion. The most common pathological findings in those with degenerative prosopagnosia were frontotemporal lobar degeneration with hippocampal sclerosis and mixed Alzheimer's and Lewy body disease pathology. In this large case series of patients diagnosed with prosopagnosia, we observed that facial recognition loss occurs across a wide range of acquired degenerative and non-degenerative neurological disorders, most commonly in males with developmental prosopagnosia. The right temporal and occipital lobes, and connecting fusiform gyrus, are key areas. Multiple different pathologies cause degenerative prosopagnosia.

Genetically proxied HTRA1 protease activity and circulating levels independently predict risk of ischemic stroke and coronary artery disease

HTRA1 has emerged as a major risk gene for stroke and cerebral small vessel disease with both rare and common variants contributing to disease risk. However, the precise mechanisms mediating this risk remain largely unknown as does the full spectrum of phenotypes associated with genetic variation in HTRA1 in the general population. Using a family-history informed approach, we first show that rare variants in HTRA1 are linked to ischemic stroke in 425,338 European individuals from the UK Biobank with replication in 143,149 individuals from the Biobank Japan. Integrating data from biochemical experiments on 76 mutations occurring in the UK Biobank, we next show that rare variants causing loss of protease function in vitro associate with ischemic stroke, coronary artery disease, and skeletal traits. In addition, a common causal variant (rs2672592) modulating circulating HTRA1 mRNA and protein levels enhances the risk of ischemic stroke, small vessel stroke, and coronary artery disease while lowering the risk of migraine and age-related macular dystrophy in GWAS and UK Biobank data from > 2,000,000 individuals. There was no evidence of an interaction between genetically proxied HTRA1 activity and levels. Our findings demonstrate a central role of HTRA1 for human disease including stroke and coronary artery disease and identify two independent mechanisms that might qualify as targets for future therapeutic interventions.

Cortical spreading depolarization-induced constriction of penetrating arteries can cause watershed ischemia: A potential mechanism for white matter lesions

Periventricular white matter lesions (WMLs) are common MRI findings in migraine with aura (MA). Although hemodynamic disadvantages of vascular supply to this region create vulnerability, the pathophysiological mechanisms causing WMLs are unclear. We hypothesize that prolonged oligemia, a consequence of cortical spreading depolarization (CSD) underlying migraine aura, may lead to ischemia/hypoxia at hemodynamically vulnerable watershed zones fed by long penetrating arteries (PAs). For this, we subjected mice to KCl-triggered single or multiple CSDs. We found that post-CSD oligemia was significantly deeper at medial compared to lateral cortical areas, which induced ischemic/hypoxic changes at watershed areas between the MCA/ACA, PCA/anterior choroidal and at the tip of superficial and deep PAs, as detected by histological and MRI examination of brains 2-4 weeks after CSD. BALB-C mice, in which MCA occlusion causes large infarcts due to deficient collaterals, exhibited more profound CSD-induced oligemia and were more vulnerable compared to Swiss mice such that a single CSD was sufficient to induce ischemic lesions at the tip of PAs. In conclusion, CSD-induced prolonged oligemia has potential to cause ischemic/hypoxic injury at hemodynamically vulnerable brain areas, which may be one of the mechanisms underlying WMLs located at the tip of medullary arteries seen in MA patients.

A multimodal meta-analysis of gray matter alterations in trigeminal neuralgia

Background

Brain gray matter alterations in patients with trigeminal neuralgia (TN) have been detected in prior neuroimaging studies, but the results are heterogeneous. The current study conducted coordinate-based meta-analyses across neuroimaging studies, aiming to find the pattern of brain anatomic and functional alterations in patients with TN.

Methods

We performed a systematic literature search of PubMed, Embase, and Web of Science to identify relevant publications. A multimodal meta-analysis for whole-brain voxel-based morphometry (VBM) studies and functional imaging studies in TN was performed using anisotropic effect size-based signed differential mapping.

Results

The meta-analysis comprised 10 VBM studies with 398 TN patients and 275 healthy controls, and 13 functional magnetic resonance imaging studies with 307 TN patients and 264 healthy controls. The multimodal meta-analysis showed conjoint structural and functional brain alterations in the right fusiform gyrus and inferior temporal gyrus, bilateral thalamus, left superior temporal gyrus, left insula, and inferior frontal gyrus. The unimodal meta-analysis showed decreased gray matter volume alone in the left putamen, left postcentral gyrus, and right amygdala as well as only functional abnormalities in the left cerebellum, bilateral precuneus, and left middle temporal gyrus.

Conclusion

This meta-analysis revealed overlapping anatomic and functional gray matter abnormalities in patients with TN, which may help provide new insights into the neuropathology and potential treatment biomarkers of TN.

Estrogen modulation of cortical spreading depression

BACKGROUND AND AIMS

Cortical spreading depression (CSD), a transient neuronal and glial depolarization that propagates slowly across the cerebral cortex, is the putative electrophysiological event underlying migraine aura and a headache trigger. Migraine is three times more prevalent in women than men, linked to circulating female hormones. High estrogen levels or estrogen withdrawal may be a migraine trigger for many women. We, therefore, aimed to examine whether sex, gonadectomy, and female hormone supplementation and withdrawal affect the susceptibility to CSD.

METHODS

To determine CSD susceptibility, we recorded the frequency of CSDs triggered during 2-h topical KCl application in intact or gonadectomized female and male rats, without or with estradiol or progesterone supplementation via daily intraperitoneal injections. Estrogen or progesterone treatment followed by withdrawal was studied in a separate cohort. To take the first step towards identifying potential mechanisms, we studied glutamate and GABAA receptor binding using autoradiography.

RESULTS

The CSD frequency in intact female rats was higher than intact male and ovariectomized rats. We did not detect a change in CSD frequency during different stages of the estrous cycle in intact females. Daily estrogen injections for three weeks did not change CSD frequency. However, one-week estrogen withdrawal after two weeks of treatment significantly increased CSD frequency compared with the vehicle group in gonadectomized females. The same protocol of estrogen treatment and withdrawal was ineffective in gonadectomized males. In contrast to estrogen, daily progesterone injections for three weeks elevated CSD susceptibility, and one-week withdrawal after two weeks of treatment partially normalized this effect. Autoradiography did not reveal significant changes in glutamate or GABAA receptor binding density after estrogen treatment and withdrawal.

CONCLUSIONS

These data suggest that females are more susceptible to CSD, and sexual dimorphism is abrogated by gonadectomy. Moreover, estrogen withdrawal after prolonged daily treatment enhances CSD susceptibility. These findings may have implications for estrogen-withdrawal migraine, although the latter tends to be without aura.

Resting-state abnormalities in functional connectivity of the default mode network in migraine: A meta-analysis

Migraine-a disabling neurological disorder, imposes a tremendous burden on societies. To reduce the economic and health toll of the disease, insight into its pathophysiological mechanism is key to improving treatment and prevention. Resting-state functional magnetic resonance imaging (rs-fMRI) studies suggest abnormal functional connectivity (FC) within the default mode network (DMN) in migraine patients. This implies that DMN connectivity change may represent a biomarker for migraine. However, the FC abnormalities appear inconsistent which hinders our understanding of the potential neuropathology. Therefore, we performed a meta-analysis of the FC within the DMN in migraine patients in the resting state to identify the common FC abnormalities. With efficient search and selection strategies, nine studies (published before July, 2022) were retrieved, containing 204 migraine patients and 199 healthy subjects. We meta-analyzed the data using the Anisotropic Effect Size version of Signed Differential Mapping (AES-SDM) method. Compared with healthy subjects, migraine patients showed increased connectivity in the right calcarine gyrus, left inferior occipital gyrus, left postcentral gyrus, right cerebellum, right parahippocampal gyrus, and right posterior cingulate gyrus, while decreased connectivity in the right postcentral gyrus, left superior frontal gyrus, right superior occipital gyrus, right orbital inferior frontal gyrus, left middle occipital gyrus, left middle frontal gyrus and left inferior frontal gyrus. These results provide a new perspective for the study of the pathophysiology of migraine and facilitate a more targeted treatment of migraine in the future.

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.

Evaluating migraine with typical aura with neuroimaging

Objective

To provide an up-to-date narrative literature review of imaging in migraine with typical aura, as a means to understand better migraine subtypes and aura biology.

Background

Characterizing subtypes of migraine with typical aura and appreciating possible biological differences between migraine with and without aura, are important to understanding the neurobiology of aura and trying to advance personalized therapeutics in this area through imaging biomarkers. One means of doing this over recent years has been the use of increasingly advanced neuroimaging techniques.

Methods

We conducted a literature review of neuroimaging studies in migraine with aura, using a PubMed search for terms 'imaging migraine', 'aura imaging', 'migraine with aura imaging', 'migraine functional imaging' and 'migraine structural imaging'. We collated the findings of the main studies, excluding small case reports and series with n < 6, and have summarized these and their implications for better understanding of aura mechanisms.

Results

Aura is likely mediated by widespread brain dysfunction in areas involving, but not limited to, visual cortex, somatosensory and insular cortex, and thalamus. Higher brain excitability in response to sensory stimulation and altered resting-state functional connectivity in migraine sufferers with aura could have a genetic component. Pure visual aura compared to visual aura with other sensory or speech symptoms as well, may involve different functional reorganization of brain networks and additional mitochondrial dysfunction mediating more aura symptoms.

Conclusion

There is a suggestion of at least some distinct neurobiological differences between migraine with and without aura, despite the shared phenotypic similarity in headache and other migraine-associated symptoms. It is clear from the vast majority of aura phenotypes being visual that there is a particular predisposition of the occipital cortex to aura mechanisms. Why this is the case, along with the relationships between cortical spreading depression and headache, and the reasons why aura does not consistently present in affected individuals, are all important research questions for the future.

Non-aura visual disturbance with high visual aura rating scale scores has stronger association with migraine chronification than typical aura

OBJECTIVES

To investigate the clinical correlates of visual symptoms in patients with migraine.

METHOD

Patients with migraine that attended our headache clinics were enrolled. Headache profiles, disability, and comorbidities were acquired with structured questionnaires. A semi-structured visual phenomenon questionnaire was also used to assess the characteristics of visual symptoms, including visual aura in patients with migraine with aura and transient visual disturbance in patients with migraine without aura. Headache specialists interviewed with the participants for the ascertainment of diagnosis and verification of the questionnaires.

RESULT

Migraine with aura patients with visual aura (n = 743, female/male = 2.3, mean age: 34.7 ± 12.2 years) and migraine without aura patients with non-aura transient visual disturbance (n = 1,808, female/male = 4.4, mean age: 39.4 ± 12.6 years) were enrolled. Patients with transient visual disturbance had higher headache-related disability and more psychiatric comorbidities. Chronic migraine was more common in migraine without aura than migraine with aura patients (41.9% vs. 11.8%, OR = 5.48 [95% CI: 4.33-7.02], p < 0.001). The associations remained after adjusting confounding factors.

CONCLUSION

Presence of non-aura transient visual disturbance may suggest a higher migraine-related disability and is linked to higher risk of chronic migraine than typical migraine aura in migraine patients. Further studies are needed to elucidate the potential mechanism.

Interictal Cognitive Performance in Children and Adolescents With Primary Headache: A Narrative Review

Primary headache is a very common and disabling disease. The burden of pain and recurrent attacks may lead to a poor quality of life, anxiety and depression. An increased risk of low functioning and curricular performances in young patients with primary headache has been described. The mechanisms underlying the relationship between migraine and poor school achievement may be various and could be a reflection of weak cognitive skills. Data concerning the cognitive functioning in the free pain interval in pediatric age are under-investigated and results are far from conclusive. The present review article suggests that, though considered a benign disease, pediatric migraine may be associated to altered neuropsychological functioning in the interictal phase. Although children and adolescents with migraine generally have a normal intelligence, they may show a not homogeneous cognitive profile, characterized by possible difficulties in verbal skills, in particular comprehension abilities. Pediatric primary headache may present altered neuropsychological functioning involving attentional resources, processing speed and memory, particularly verbal memory. Given the impact that this disease can have on school performance and the tendency to persist from childhood to adulthood, a cognitive screening in young patients affected by primary headache is pivotal. Additional neuropsychological research using more homogenous methods is needed.

Structural and Functional Brain Changes in Patients With Classic Trigeminal Neuralgia: A Combination of Voxel-Based Morphometry and Resting-State Functional MRI Study

Objectives

Brain structural and functional abnormalities have been separately reported in patients with classic trigeminal neuralgia (CTN). However, whether and how the functional deficits are related to the structural alterations remains unclear. This study aims to investigate the anatomical and functional deficits in patients with CTN and explore their association.

Methods

A total of 34 patients with CTN and 29 healthy controls (HCs) with age- and gender-matched were recruited. All subjects underwent structural and resting-state functional magnetic resonance imaging (fMRI) scanning and neuropsychological assessments. Voxel-based morphometry (VBM) was applied to characterize the alterations of gray matter volume (GMV). The amplitude of low-frequency fluctuation (ALFF) method was used to evaluate regional intrinsic spontaneous neural activity. Further correlation analyses were performed between the structural and functional changes and neuropsychological assessments.

Results

Compared to the HCs, significantly reduced GMV was revealed in the right hippocampus, right fusiform gyrus (FFG), and temporal-parietal regions (the left superior/middle temporal gyrus, left operculo-insular gyrus, left inferior parietal lobule, and right inferior temporal gyrus) in patients with CTN. Increased functional activity measured by zALFF was observed mainly in the limbic system (the bilateral hippocampus and bilateral parahippocampal gyrus), bilateral FFG, basal ganglia system (the bilateral putamen, bilateral caudate, and right pallidum), left thalamus, left cerebellum, midbrain, and pons. Moreover, the right hippocampus and FFG were the overlapped regions with both functional and anatomical deficits. Furthermore, GMV in the right hippocampus was negatively correlated with pain intensity, anxiety, and depression. GMV in the right FFG was negatively correlated with illness duration. The zALFF value in the right FFG was positively correlated with anxiety.

Conclusion

Our results revealed concurrent structural and functional changes in patients with CTN, indicating that the CTN is a brain disorder with structural and functional abnormalities. Moreover, the overlapping structural and functional changes in the right hippocampus and FFG suggested that anatomical and functional changes might alter dependently in patients with CTN. These findings highlight the vital role of hippocampus and FFG in the pathophysiology of CTN.

Association between migraine and risk of ocular motor cranial nerve palsy

To assess association between migraines and development of ocular motor cranial nerve palsy (CNP) and finding risk factors using the National Sample Cohort database from the Korea National Health Insurance Service. Data was analyzed from 4,234,341 medical screening examinees aged 20–90 years in 2009. Cox proportional hazard regression analysis was used to the adjusted hazard ratios (HR) for ocular motor CNP according to presence of migraine. Subgroup analysis was performed to evaluate effect of other factors on association of migraine with ocular motor CNP. A total of 5806 participants (0.14% of subjects) developed ocular motor CNP and were assigned to CNP group, 4,048,018 were assigned to control group, with an average of 8.22 ± 0.93 years of follow-up. Incidence of ocular motor CNP increased in migraine group compared to control. After adjusting potential confounding variables, HR for ocular motor CNP was 1.166 (confidence interval [CI] 1.013–1.343) in migraine group. Subgroups of relatively younger age less than 65 years (HR = 1.267, 95% CI 1.067–1.504), male gender (HR = 1.228, 95% CI 1.000–1.122), smokers (HR 1.426, 95% CI 1.127–1.803), and diabetes mellitus patients (HR = 1.378, 95% CI 1.045–1.378) showed a stronger association between migraines and development of ocular motor CNP. Our population-based cohort study demonstrated a significant association between presence of migraines and incidence of ocular motor CNP. Especially, relatively younger age, males, smokers, and diabetes patients with migraines could have a higher risk of developing ocular motor CNP.

Altered Brain Topological Property Associated With Anxiety in Experimental Orthodontic Pain

Background

Orthodontic pain is orofacial pain caused by tooth movement. Anxiety is a strong predictor of the severity of such pain, but little is known about the underlying neuropsychological mechanisms of such effects. The purpose of this study was to investigate the effect of orthodontic pain on brain functional networks and to define the mediating role of anxiety in orthodontic pain and brain function.

Methods

Graph theory-based network analyses were applied to brain functional magnetic resonance imaging data from 48 healthy participants exposed to 24 h orthodontic pain stimuli and 49 healthy controls without any stimulation.

Results

In the experimental orthodontic pain stimulation, brain functional networks retained a small-world organization. At the regional level, the nodal centrality of ipsilateral brain nodes to the pain stimulus was enhanced; in contrast the nodal centrality of contralateral brain areas was decreased, especially the right mid-cingulate cortex, which is involved in pain intensity coding. Furthermore, anxiety mediated the relationship between nodal efficiency of mid-cingulate cortex and pain severity.

Conclusion

The results illuminate the neural mechanisms of orthodontic pain by revealing unbalanced hemispherical brain function related to the unilateral pain stimulation, and reveal clinically exploitable evidence that anxiety mediates the relationship between nodal function of right mid-cingulate cortex and orthodontic pain.

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.

[A case of suspected migraine with aura: transient cortical venous dilatation visualized by susceptibility-weighted imaging]

A 41-year-old man was admitted with proper name anomia and headache of sudden onset. He had a history of migraine without aura from the age of 35. Neurological examination on admission showed acalculia, proper name anomia, left-right disorientation and severe left-sided headache with nausea. Susceptibility-weighted MRI revealed dilatation of cortical veins of the left hemisphere. MR angiography and contrast CT revealed no cerebral arterial or venous occlusion. The patient's proper name anomia was improved at 5 hours from the onset and acalculia and left-right disorientation were improved at 17 hours from the onset. At 42 hours from the onset, he had recovered from his headache, and the dilatation of cortical veins of the left hemisphere had disappeared. Acalculia and left and right disorientation are rare presentations of migraine with aura. Susceptibility-weighted imaging may be a useful tool to distinguish migraine with aura from stroke and stroke mimics.

Cortical excitability in migraine: Contributions of magnetic resonance imaging

Migraine is characterized by symptoms related to cortical hyperexcitability such as photophobia, phonophobia, osmophobia and allodynia. One-third of migraineurs experience aura, whose neurophysiological substrate is thought to be cortical spreading depression (CSD). Functional magnetic resonance imaging (MRI) has shown the migraine aura to be characterized by cerebral hyperactivity/hyperperfusion followed by hypometabolism/hypoperfusion spreading along the occipital cortex with the same spatiotemporal organization as the experimentally triggered CSD. The link between migraine aura and headache remains undetermined. Neuroimaging studies have failed to show a leakage of the blood-brain barrier, which was suspected to occur during CSD and to cause the stimulation of trigeminal nociceptive receptors. However, recent studies have highlighted the involvement of neuroglial inflammation and other studies have suggested that a common central network plays a role in the link between CSD and migraine pain. Finally, MRI has made it possible to study the contribution of metabolites such as glutamic acid, γ-amino-butyric acid and sodium in the pathophysiology of hyperexcitability in migraine.

Visual Perception in Migraine: A Narrative Review

Migraine, the most frequent neurological ailment, affects visual processing during and between attacks. Most visual disturbances associated with migraine can be explained by increased neural hyperexcitability, as suggested by clinical, physiological and neuroimaging evidence. Here, we review how simple (e.g., patterns, color) visual functions can be affected in patients with migraine, describe the different complex manifestations of the so-called Alice in Wonderland Syndrome, and discuss how visual stimuli can trigger migraine attacks. We also reinforce the importance of a thorough, proactive examination of visual function in people with migraine.

Can you have a migraine aura without knowing it?

PURPOSE OF REVIEW

This review covers several aspects our understanding of episodic manifestations and unusual symptoms that may be associated with migraine aura.

RECENT FINDINGS

The episodic manifestation of migraine aura is typically visual in nature, although five other types are currently recognized: sensory, speech and/or language, motor, brainstem, and retinal. Other transitory perceptions or experiences such as emotional, olfactory, or auditory have been reported as possible migraine auras. As underlined by the much higher reported prevalence of aura manifestation in individuals with professional knowledge of its possible manifestations, it appears that a number of migraine auras may remain unnoticed, unreported, or misdiagnosed.

SUMMARY

Aura manifestations may be more common, complex, symptom-rich and variable than previously thought. Clinicians should proactively ask questions beyond those addressing visual symptoms when examining individuals with a potential diagnosis of migraine with aura.

Transient Neurologic Dysfunction in Migraine

Transient disturbances in neurologic function are disturbing features of migraine attacks. Aura types include binocular visual, hemi-sensory, language and unilateral motor symptoms. Because of the gradual spreading quality of visual and sensory symptoms, they were thought to arise from the cerebral cortex. Motor symptoms previously included as a type of migraine aura were reclassified as a component of hemiplegic migraine. ICHD-3 criteria of the International Headache Society, added brainstem aura and retinal aura as separate subtypes. The susceptibility to all types of aura is likely to be included by complex and perhaps epigenetic factors.

Mitochondria in migraine pathophysiology - does epigenetics play a role?

The approximately three times higher rate of migraine prevalence in women than men may result from the mitochondrial transmission of this disease. Studies with imaging techniques suggest disturbances in mitochondrial metabolism in specific regions of the brain in migraine patients. Migraine shares some clinical features with several mitochondrial diseases and many other disorders include migraine headaches. Epigenetic regulation of mitochondrial DNA (mtDNA) is a matter of debate and there are some conflicting results, especially on mtDNA methylation. Micro RNAs (miRNAs) and long-noncoding RNA (lncRNAs) have been detected in mitochondria. The regulation of the miRNA-lncRNA axis can be important for mitochondrial physiology and its impairment can result in a disease phenotype. Further studies on the role of mitochondrial epigenetic modifications in migraine are needed, but they require new methods and approaches.

Spreading depression as a preclinical model of migraine

Spreading depression (SD) is a slowly propagating wave of near-complete depolarization of neurons and glial cells across the cortex. SD is thought to contribute to the underlying pathophysiology of migraine aura, and possibly also an intrinsic brain activity causing migraine headache. Experimental models of SD have recapitulated multiple migraine-related phenomena and are considered highly translational. In this review, we summarize conventional and novel methods to trigger SD, with specific focus on optogenetic methods. We outline physiological triggers that might affect SD susceptibility, review a multitude of physiological, biochemical, and behavioral consequences of SD, and elaborate their relevance to migraine pathophysiology. The possibility of constructing a recurrent episodic or chronic migraine model using SD is also discussed.

Evaluation of the Optic Nerve by Strain and Shear Wave Elastography in Patients With Migraine

OBJECTIVES

To investigate the optic nerve's elastic properties using shear wave and strain elastography in patients with migraine compared to healthy individuals.

METHODS

The migraine group consisted of 30 patients (16 with visual auras and 14 without auras) who had previously had a diagnosis of migraine. These were age and sex matched with healthy participants to form the control group. The findings from shear wave and strain elastography in the groups were compared. The elastographic examination was performed with a 6-15-MHz multifrequency linear array transducer.

RESULTS

The evaluation involved 30 patients with migraine (3 male and 27 female), whose mean age ± SD was 34.63 ± 10 years, and 30 healthy participants (3 males, 27 females), whose mean age was 36.4 ± 10.5 years. In strain elasticity patterns, a statistically insignificant hardening of the optic nerve in the patients with migraine was observed (P = .052). Analysis of the shear wave elastic modulus values (9.8 ± 3.34 and 12.3 ± 5.25 kPa; P = .03) revealed that differences between the healthy participants and patients with migraine were statistically significant. The results for elasticity patterns and the shear modulus suggested that the differences between migraines with and without visual auras were insignificant (P > .05). A positive correlation was discovered between the duration of the disease and the shear modulus in the patients with migraine (r = 0.496; P < .01).

CONCLUSIONS

Histopathologic changes in the optic nerve may be seen in patients with migraine due to possible fibrotic changes. Elastographic techniques can be useful diagnostic tools for investigating these changes.

Neuroimaging clues of migraine aura

While migraine headaches can be provoked, or predicted by the presence of an aura or premonitory symptoms, the prediction or elicitation of the aura itself is more problematic. Therefore, imaging studies directly examining the aura phenomenon are sparse. There are however interictal imaging studies that can shed light on the pathophysiology of the migraine with aura (MWA) cascade. Here, we review findings pointing to the involvement of cortical spreading depression (CSD) and neuroinflammation in MWA. Whether asymptomatic CSD also happens in some migraine without aura is still under debate. In addition, new evidence points to glial activation in MWA, indicating the involvement of astrocytes in the neuroinflammatory cascade that follows CSD, as well as dural macrophages, supporting the involvement of the trigeminovascular system in migraine pain.

Imaging of neuroinflammation in migraine with aura: A [11C]PBR28 PET/MRI study

OBJECTIVE

To determine if migraine with aura is associated with neuroinflammation, which has been suggested by preclinical models of cortical spreading depression (CSD) as well as imaging of human pain conditions.

METHODS

Thirteen migraineurs with aura and 16 healthy controls received integrated PET/MRI brain scans with [¹¹C]PBR28, a radioligand that binds to the 18 kDa translocator protein, a marker of glial activation. Standardized uptake value ratio (SUVR) was compared between groups, and regressed against clinical variables, using region of interest and whole-brain voxelwise analyses.

RESULTS

Compared to healthy controls, migraineurs demonstrated SUVR elevations in nociceptive processing areas (e.g., thalamus and primary/secondary somatosensory and insular cortices) as well as in areas previously shown to be involved in CSD generation (visual cortex). SUVR levels in frontoinsular cortex, primary/secondary somatosensory cortices, and basal ganglia were correlated with frequency of migraine attacks.

CONCLUSIONS

These findings demonstrate that migraine with aura is associated with neuroimmune activation/neuroinflammation, and support a possible link between CSD and glial activation, previously observed in animals.

Migraine improvement correlates with posterior cingulate cortical thickness reduction

Objective The main goal of this study was to correlate migraine improvement, after prophylactic therapy, with cortical thickness changes. Methods Cortical thickness maps were obtained with magnetic resonance imaging (MRI) from 19 patients with migraine before (first scan) and after (second scan) prophylactic treatment, and these were compared with controls using the FreeSurfer MRI tool. Cortical changes were correlated with the headache index (HI). Results Anincrease incortical thickness was found in the right cuneus and precuneus, somatosensory and superior parietal cortices in both patient scans, compared with the controls. No changes were observed in the left hemisphere. Following correction for multiple comparisons, no areas changed from the first to the second scan. Regression analysis showed a significant negative correlation between the HI improvement and cortical thickness changes in the left posterior cingulate, a region involved with nociception and, possibly, the development of chronic pain. Conclusion There were changes in cortical thickness in patients with migraine relative to controls in areas involved with vision and pain processing. Left posterior cingulate cortical changes correlated with headache frequency and intensity.

Migraine with Aura: Surface-Based Analysis of the Cerebral Cortex with Magnetic Resonance Imaging

Objective

Previous migraine studies have reported gray matter alterations in various cortical regions with conflicting results. This study aimed to explore a cortical morphometric difference in migraineurs with aura (MA) compared to healthy subjects (HS) and to delineate a possible difference between the cortical morphological features and different aura phenotypes.

Materials and Methods

Forty-eight MA and 30 HS that were balanced by sex, age, and educational level were selected for this study. T2-weighted and three-dimensional T1-weighted magnetic resonance imaging (MRI) of the brain were acquired using a 1.5T MRI scanner. Surface-based morphometry from the MRI data was used to identify differences between the MA and HS group, and then between MA subgroups. The MA group was subdivided into migraineurs who experienced only visual aura (MVA) and migraineurs who had visual, somatosensory and dysphasic symptoms (MVA+).

Results

The MVA+ group had significantly reduced cortical surface area of the left rostral middle frontal cortex compared with the MVA group (p < 0.001). Migraine patients had significantly reduced volume of the left fusiform gyrus relative to HS (p < 0.001). Also, the sulcal depth increased at the level of the left temporal pole in the MVA+ group relative to the MVA group (p < 0.001). The vertex-by-vertex analysis did not exhibit any significant difference in cortical thickness between MA and HS, and between MVA+ and MVA, when corrected for multiple comparisons.

Conclusion

Migraineurs with aura demonstrates different morphometric features from HS in multiple cortical regions. MVA+ have different morphometric features in the left frontal and temporal lobe relative to MVA, which could be a source of distinct symptoms and serve as potential biomarkers of different MA subtypes.

Visual symptoms and childhood migraine: Qualitative analysis of duration, location, spread, mobility, colour and pattern

AIM

To examine the characteristics of visual symptoms during attacks of migraine in children and adolescents.

METHOD

A qualitative analysis of prospectively collected data over 5 years, on characteristics of visual symptoms during migraine attacks. Diagnosis of migraine and aura was based on the International Classification of Headache Disorders 3^rd edition beta version. We also provided the opportunity for patients to illustrate their visual aura symptoms to aid in diagnosis.

RESULTS

Visual symptoms were reported by 387/1079 (36%) of migraineurs. Of these, 172 (16%) patients fulfilled the International Classification of Headache Disorders Criteria A, B, C iv and D, but missed one (n = 75; 43.5%) or two (n = 97; 56.5%) of the remaining items of criteria C as the visual symptoms were of non-gradual spread (n = 35; 20%), appeared in both visual fields (n = 99; 58%), or lasted less than 5 minutes or more than 60 minutes (n = 129; 75%).

CONCLUSION

The International Classification of Headache Disorders 3^rd edition beta version criteria are useful in diagnosis of migraine with visual aura in children and adolescents, but visual symptoms varied considerably in duration, pattern, mobility, location, mode of onset and colours. Providing opportunity for patients to illustrate their symptoms can provide additional diagnostic information. The pathophysiology and the clinical concept of typical MVA is still to an extent an assumption and needs further evaluation.

APPROVAL

The study was approved by the Health Research Authority - London and the local Research and Innovation Department at Barking Havering and Redbridge National Health Service Trust. Formal parental consent was not considered essential for this type of study.

Functional Neuroimaging Biomarkers in Migraine: Diagnostic, Prognostic and Therapeutic Implications

BACKGROUND

In current migraine clinical practice, conventional neuroimaging examinations are often sought to exclude possible causes of secondary headaches or migraineassociated disorders. Contrariwise, although advanced Magnetic Resonance Imaging (MRI) has improved tremendously our understanding of human brain processes in migraine patients, to the state of the art they have not superseded the conventional neuroimaging techniques in the migraine clinical setting.

METHODS

A comprehensive review was conducted of PubMed citations by entering the keyword "marker" and/or "biomarker" combined with "migraine" and/or "headache". Other keywords included "imaging" or "neuroimaging", "structural" or "functional". The only restriction was English-language publication. The abstracts of all articles meeting these criteria were reviewed, and the full text was retrieved and examined for relevant references.

RESULTS

Several authors tried to identify imaging biomarkers able to identify different migraine phenotypes or, even better, to follow-up the same migraine patients during the course of the disease, to predict the evolution into more severe phenotypes and, finally, the response to specific treatment.

CONCLUSION

The identification of diagnostic, prognostic and therapeutic advanced neuroimaging biomarkers in the migraine clinical setting, in order to approach to patients in a more and more rational and "tailored" way, is extremely intriguing and futuristic. Unfortunately, reliable and robust neuroimaging biomarkers are still lacking for migraine, probably due to both not completely understood pathogenesis and clinical and neuroimaging heterogeneity. Although further longitudinal advanced neuroimaging studies, aimed to identify effective neuroimaging biomarkers, are needed, this review aims to collect the main and most recent works on this topic.

Alien hand syndrome and migraine with aura: A case report

BACKGROUND

Alien Hand Syndrome (AHS) is an uncontrollable, involuntary, but in appearance, purposeful motor control disorder of the upper extremity.

CASE REPORT

A 42-year-old male patient was admitted to our clinic complaining of involuntary motor activity in his right hand. He had a previous history of migraine with visual aura. The uncontrollable motor control disorder was compatible with Alien Hand Syndrome, which was appearing immediately after the visual aura and before the beginning of headache.

CONCLUSION

Alien Hand Syndrome is usually observed with anterior cerebral artery infarction, midline tumors, trauma and several neurodegenerative diseases, but is rarely seen in paroxysmal conditions such as migraine with aura.

Clinical description of attack-related cognitive symptoms in migraine: A systematic review

Introduction

Cognitive symptoms have been described during migraine attacks since the Roman era; while being neglected throughout the centuries, they are relevant contributors to migraine-related disability.

Objective

To determine whether cognitive symptoms are included in clinical series describing migraine attack phenomenology, and which symptoms occur in each attack phase.

Method

Systematic review of existing data on clinical descriptions of migraine attacks, focusing on cognitive symptomatology. Data were organized and analyzed qualitatively, due to methodological differences between studies.

Results

Twenty-four articles were reviewed, with a total sample of 7007 patients, including 82.9% females with an average age of 39.2 years. Twenty one (75%) studies analyzed one phase of the attack (eight prodromes, five auras, one between aura and pain, three headaches and three postdromes), the remaining studied more than one phase. Cognitive complaints were the most frequent symptom of the prodromic (30%) and headache (38%) phases, while fatigue (70%) dominated the resolution phase. Not enough data is available to estimate the frequency of cognitive symptoms during the aura.

Discussion

Cognitive symptoms are described in all phases of the migraine attack phenomenology in published clinical series of migraine. Their characteristics appear to be different in each attack phase, although methodological limitations prevent generalization of this finding.

Alien Hand Syndrome

Alien hand syndrome (AHS) is a rare disorder of involuntary limb movement together with a sense of loss of limb ownership. It most commonly affects the hand, but can occur in the leg. The anterior (frontal, callosal) and posterior variants are recognized, with distinguishing clinical features and anatomical lesions. Initial descriptions were attributed to stroke and neurosurgical operations, but neurodegenerative causes are now recognized as most common. Structural and functional imaging and clinical studies have implicated the supplementary motor area, pre-supplementary motor area, and their network connections in the frontal variant of AHS, and the inferior parietal lobule and connections in the posterior variant. Several theories are proposed to explain the pathophysiology. Herein, we review the literature to update advances in the understanding of the classification, pathophysiology, etiology, and treatment of AHS.

Heterogeneous propagation of spreading depolarizations in the lissencephalic and gyrencephalic brain

In the recently published article, "Heterogeneous incidence and propagation of spreading depolarizations," it is shown, in vivo and in vitro, how KCl-induced spreading depolarizations in mouse and rat brains can be highly variable, and that they are not limited, as once thought, to a concentric, isotropic, or homogenous depolarization wave in space or in time. The reported results serve as a link between the different species, and this paper contributes to changing the way in which SD expansion is viewed in the lissencephalic brain. Here, we discuss their results with our previous observations made in the gyrencephalic swine brain, in computer simulations, and in the human brain.

How does spreading depression spread? Physiology and modeling

Spreading depression (SD) is a wave phenomenon in gray matter tissue. Locally, it is characterized by massive redistribution of ions across cell membranes. As a consequence, there is sustained membrane depolarization and tissue polarization that depress any normal electrical activity. Despite these dramatic events, SD remains difficult to observe in humans noninvasively, which, for long, has slowed advances in this field. The growing appreciation of its clinical importance in migraine and stroke is therefore consistent with an increasing need for computational methods that tackle the complexity of the problem at multiple levels. In this review, we focus on mathematical tools to investigate the question of spread and its two complementary aspects: What are the physiological mechanisms and what is the spatial extent of SD in the cortex? This review discusses two types of models used to study these two questions, namely, Hodgkin-Huxley type and generic activator-inhibitor models, and the recent advances in techniques to link them.

Pattern-Reversal Visual Evoked Potential Parameters and Migraine in the Teenage Population

Although migraine represents one of the most common form of primary headache in the teenage population, most neurophysiologic studies are only on the adulthood. We investigated 38 teenage patients with migraine with aura, 17 male and 21 female, with a mean age of 16.2 years, comparing them with gender- and age-matched patients with migraine without aura and healthy subjects. Also, characteristics of aura were correlated with pattern-reversal visual evoked potential parameters. There was a significant difference in left and right eye N2 wave latencies between migraine with aura and migraine without aura patients or healthy controls. In migraine with aura and migraine without aura, 26.3% of patients had abnormal wave latency. Reported tunnel vision during the aura was correlated with lower N1P1 and/or P1N2 wave amplitudes. Also, higher amplitude in patients with migraine with aura correlated with younger age and earlier disease onset, whereas longer aura duration correlated with prolonged wave latency. Findings suggest that migraine subtypes may be differentiated on the basis of N2 wave latency prolongation.

Do interictal microembolic signals play a role in higher cortical dysfunction during migraine aura?

Introduction

The aim of this study was to evaluate the prevalence and clinical impact of interictal microembolic signals (MES) in patients suffering from migraine with higher cortical dysfunction (HCD), such as language and memory impairment, during an aura.

Patients and methods

This study was carried out on 34 migraineurs with language and memory impairment during aura (HCD group), 31 migraineurs with only visual or visual and somatosensory symptoms during aura (Control group I), and 34 healthy controls (Control group II). We used a Doppler instrument to detect microemboli. Demographic data, disease features and the detection of MES between these groups, as well as the predictors of HCD during the aura, were analyzed.

Results

The duration of aura was longer and the frequency of aura was higher among patients with language and memory impairment during aura compared to Control group I. MES was detected in 29.4% patients from the HCD group, which was significantly higher compared to 3.2% in Control group I and 5.9% in Control group II. Regarding the absence or presence of MES, demographic and aura features were not different in the HCD subgroups. A longer duration of aura, the presence of somatosensory symptoms during the aura and the presence of interictal MES were independent predictors of HCD during the aura.

Conclusion

The present findings indicate that HCD and MES are related in patients with migraine with aura. Further research is needed to better understand the exact pathophysiological mechanism.

Dissecting the association between migraine and stroke

Migraine is a common disabling neurological disorder resulting from excessive cortical excitation and trigeminovascular afferent sensitization. In addition to aberrant neuronal processing, migraineurs are also at significant risk of vascular disease. Consequently, the impact of migraine extends well beyond the ictal headache and includes a well-documented association with acute ischemic stroke, particularly in young women with a history of migraine with aura. The association between migraine and stroke has been acknowledged for 40 years or more. However, examining the pathobiology of this association has become a more recent and critically important undertaking. The diversity of mechanisms underlying the association between migraine and stroke likely reflects the heterogenous nature of this disorder. Vasospasm, endothelial injury, platelet aggregation and prothrombotic states, cortical spreading depression, carotid dissection, genetic variants, and traditional vascular risk factors have been offered as putative mechanisms involved in migraine-related stroke risk. Assimilating these seemingly divergent pathomechanisms into a cogent understanding of migraine-related stroke will inform future studies and the development of new strategies for the prevention and treatment of migraine and stroke.

Cortical spreading depression in migraine-time to reconsider?

New evidence concerning the pathophysiology of migraine has come from the results of therapeutic transcranial magnetic stimulation (tTMS). The instantaneous responses to single pulses applied during the aura or headache phase, together with a number of other observations, make it unlikely that cortical spreading depression is involved in migraine. tTMS is considered to act by abolishing abnormal impulse activity in cortical pyramidal neurons and a suggestion is made as to how this activity could arise.

Variability of clinical features in attacks of migraine with aura

Background

There is significant variability in the clinical presentation of migraine, both among patients, and between attacks in an individual patient. We examined clinical features of migraine with aura in a large group of patients enrolled in a clinical trial, and compared retrospective migraine attack characteristics reported upon enrollment in the trial with those recorded prospectively in the trial.

Methods

Patients with migraine ( n = 267) with typical visual aura in more than 30% of their attacks were enrolled from 16 centers for a clinical trial. Upon enrollment, patients provided a detailed retrospective description of the clinical features of their attacks of migraine. During the trial, clinical symptoms in migraine attacks starting with aura were recorded prospectively in 861 attacks.

Results

Retrospectively reported visual aura symptoms were variable and often overlapping; the most common symptoms were dots or flashing lights, wavy or jagged lines, blind spots, and tunnel vision. Multiple patients reported more than one visual phenomenon. Approximately half of the patients reported nonvisual aura symptoms, the most common were numbness and tingling, followed by difficulty in recalling or speaking words. A significant percentage of patients also reported a change in olfaction. There were several inconsistencies between the features of prospectively recorded and retrospectively reported attacks. Headache, nausea, photophobia, and phonophobia were all less common in prospectively recorded attacks as compared with retrospective reporting. Nausea was prospectively recorded in only 51% of attacks and mostly with mild intensity. The occurrence and severity of nausea was reduced with advancing patient age. Phonophobia was not consistently recorded in conjunction with photophobia.

Conclusion

These findings are consistent with variable involvement of different brain regions during a migraine attack. The variable occurrence of nausea, and phonophobia in conjunction with photophobia, both defining features of migraine, may be an important consideration in designing clinical studies of migraine in which prospectively recorded attacks are diagnosed based on these clinical features.

Increased interictal visual network connectivity in patients with migraine with aura

OBJECTIVE

To evaluate the resting-state visual network functional connectivity in patients with migraine with aura and migraine without aura during the interictal period.

POPULATION AND METHODS

Using resting-state functional magnetic resonance imaging, the resting-state visual network integrity was investigated in 20 patients with migraine with aura, 20 age- and sex-matched patients with migraine without aura and 20 healthy controls. Voxel-based morphometry and diffusion tensor imaging were used to assess whether between-groups differences in functional connectivity were dependent on structural or microstructural changes.

RESULTS

Resting-state functional magnetic resonance imaging data showed that patients with migraine with aura, compared to both patients with migraine without aura and healthy controls, had a significant increased functional connectivity in the right lingual gyrus within the resting-state visual network (p < 0.05, cluster-level corrected). This abnormal resting-state visual network functional connectivity was observed in the absence of structural or microstructural abnormalities and was not related to migraine severity.

CONCLUSIONS

Our imaging data revealed that patients with migraine with aura exhibit an altered resting-state visual network connectivity. These results support the hypothesis of an extrastriate cortex involvement, centred in the lingual gyrus, a brain region related to mechanisms underlying the initiation and propagation of the migraine aura. This resting-state functional magnetic resonance imaging finding may represent a functional biomarker that could differentiate patients experiencing the aura phenomenon from patients with migraine without aura, even between migraine attacks.