The pathogenesis of migraine - 17th to early 20th century understandings

Comparison of migraine with left- versus right-sided headache: A cross-sectional study

OBJECTIVE

The goal of this study was to clarify whether clinical differences exist between patients with migraine who experience headache that is typically left-sided ("left-migraine") versus right-sided ("right-migraine") during attacks.

BACKGROUND

Migraine has been associated with unilateral headache for millennia and remains a supportive trait for the clinical diagnosis of migraine of the International Classification of Headache Disorders. It is currently unknown why headache in migraine is commonly unilateral, and whether headache-sidedness is associated with other clinical features.

METHODS

This is a cross-sectional study comparing left- versus right-migraine using all available intake questionnaires of new patients evaluated at an academic tertiary headache center over a 20-year period. Eligibility was based on patient written responses indicating the typical location of headache during attacks. In our analyses, the side of headache (left or right) was the predictor variable. The outcomes included various migraine characteristics and psychiatric comorbidities.

RESULTS

We identified 6527 patients with migraine, of which 340 met study eligibility criteria. Of these, 48.8% (166/340) had left migraine, and 51.2% (174/340) had right migraine. When comparing patients with left- versus right-migraine, patients with left migraine experienced 3.6 fewer headache-free days (95% confidence interval [CI] 1.3-5.9; p = 0.002) and 2.4 more severe headache days (95% CI 0.8-4.1; p = 0.004) in the previous 4 weeks. No significant differences in age, sex, handedness, migraine characteristics, or psychiatric comorbidities were identified between the two groups.

CONCLUSIONS

Patients with migraine with typically left-sided headache during attacks reported a higher burden of headache frequency and severity than those with typically right-sided headache during attacks. These findings may have implications for our understanding of migraine pathophysiology, treatment, and clinical trial design.

Left- vs right-sided migraine: a scoping review

BACKGROUND

Migraine is a historically unilateral head pain condition, the cause of which is not currently known. A growing body of literature suggests individuals who experience migraine with left-sided headache ("left-sided migraine") may be distinguished from those who experience migraine with right-sided headache ("right-sided migraine").

OBJECTIVE

In this scoping review, we explore migraine unilaterality by summarizing what is currently known about left- and right-sided migraine.

METHODS

Two senior medical librarians worked with the lead authors to construct and refine a set of search terms to identify studies of subjects with left- or right-sided migraine published between 1988, which is the year of publication of the first edition of the International Classification of Headache Disorders (ICHD), and December 8, 2021 (the date the searches were conducted). The following databases were searched: Medline, Embase, PsycINFO, PubMed, Cochrane Library, and Web of Science. Abstracts were loaded into Covidence review software, deduplicated, then screened by two authors to determine study eligibility. Eligible studies were those involving subjects diagnosed with migraine (according to ICHD criteria) in which the authors either: a) compared left- to right-sided migraine; or b) described (with analysis) a characteristic that differentiated the two. Data were extracted by the lead author, including ICHD version, the definition of unilateral migraine used by the authors, sample size, whether the findings were collected during or between attacks, and their key findings. The key findings were grouped into the following themes: handedness, symptoms, psychiatric assessments, cognitive testing, autonomic function, and imaging.

RESULTS

After deduplication, the search yielded 5428 abstracts for screening. Of these, 179 met eligibility criteria and underwent full text review. 26 articles were included in the final analysis. All of the studies were observational. One study was performed during attack, nineteen between attacks, and six both during and between attacks. Left- and right-sided migraine were found to differ across multiple domains. In several cases, reciprocal findings were reported in left- and right-migraine. For example, both left- and right-sided migraine were associated with ipsilateral handedness, tinnitus, onset of first Parkinson's symptoms, changes in blood flow across the face, white matter hyperintensities on MRI, activation of the dorsal pons, hippocampal sclerosis, and thalamic NAA/Cho and NAA/Cr concentrations. In other cases, however, the findings were specific to one migraine laterality. For example, left-sided migraine was associated with worse quality of life, anxiety, bipolar disorder, PTSD, lower sympathetic activity, and higher parasympathetic activity. Whereas right-sided migraine was associated with poorer performance on multiple cognitive tests, a greater degree of anisocoria, changes in skin temperature, higher diastolic blood pressure, changes in blood flow through the middle cerebral and basilar arteries, and changes on EEG.

CONCLUSION

Left- and right-sided migraine differed across a wide range of domains, raising the possibility that the pathophysiology of left- and right-migraine may not be identical.

History of migraine

Migraine symptoms were described in ancient Babylonia, and supernatural forces were felt to play a role in etiology and treatment. This changed in the Greco-Roman period, when the (dis)balance of humors was considered in (patho)physiology and treatment based on this. Aretaeus distinguished between cephalalgia, cephalea, and heterocrania. The latter term was changed to hemicrania by Galen. Physicians in the 17th century attributed headache to the meninges, extracranial periost, and cranial blood vessels. As for the pathophysiology, Willis suggested intracranial vasoconstriction with subsequent dilatation. Tissot and Fothergill gave comprehensive descriptions of migraine, including visual symptoms. Symptomatic and idiopathic hemicrania were distinguished in the early 19th century. Vasomotor pathophysiology was scientifically studied in the 1860s, leading to sympathicotonic and angioparalytic theories. Latham combined them, stating the latter follows the first. Ergot was introduced in 1868; ergotamine was isolated in 1918. This led to the vasodilatation theory of migraine (Wolff), the discovery of 5-HT, and later the specific agonists. Aura and cortical spreading depression were studied in the early 1940s and related to spreading oligemia in the 1980s. Subsequently, hyperemia followed by oligemia after CSD was found. After the discovery of CGRP, a new a class of drugs became the subject of clinical studies.

Molecular simulations reveal the impact of RAMP1 on ligand binding and dynamics of calcitonin gene-related peptide receptor (CGRPR) heterodimer

Calcitonin gene-related peptide receptor (CGRPR) is a heterodimer protein complex consisting of a class-B G protein-coupled receptor (GPCR) named calcitonin receptor-like receptor (CLR) and an accessory protein, receptor activity modifying protein type 1 (RAMP1). Here in this study, with several molecular modeling approaches and molecular dynamics (MD) simulations, the structural and dynamical effects of RAMP1 on the binding of small molecule CGRPR inhibitors (namely rimegepant and telcagepant) to the CGRPR extracellular ectodomain complex site (site 1) and transmembrane binding site (site 2) are investigated. Results showed that although these molecules stay stable at site 1, they can also bind to site 2, which may be interpreted as non-specificity of the ligands, however, most of these interactions at transmembrane binding site are not sustainable or are weak. Furthermore, to examine the site 2 for gepant binding, different in silico experiments (i.e., alanine scanning mutagenesis, SiteMap, ligand decomposition binding free energy analyses) are also conducted and the results confirmed the putative binding pocket (site 2) of the gepants at the CGRPRs.

Positional headache induced by isolated middle cerebral artery dissection: Two case reports

BACKGROUND

Isolated middle cerebral artery dissection is uncommon and occurs in patients reporting headaches as the only symptom. This makes intracranial artery dissection challenging to diagnose and treat.Case description: We describe two cases of positional headache caused by isolated middle cerebral artery dissection, confirmed using high-resolution magnetic resonance imaging. The two patients presented with sudden-onset headache, occurring when lying in the lateral decubitus position. When lying down in the decubitus position ipsilateral to the intracranial artery dissection, the headache aggravated and middle cerebral artery flow velocity increased on transcranial Doppler ultrasonography compared to when in the supine position. Both patients were treated with antiplatelet agents, and the headache completely resolved within 1-2 weeks.

CONCLUSION

We recommend additional imaging studies evaluating intracranial artery dissection as a cause of positional headache.

Changes in retinal vessel diameters in migraine patients during attack-free period

AIM

To evaluate the retinal vessel diameters in patients with migraine by optical coherence tomography (OCT).

METHODS

In this cross-sectional study, 124 eyes of 62 patients with a diagnosis of unilateral migraine during attack-free period and 42 age- and sex-matched control subjects were included. Migraine patients were divided into the ≤2 migraine attacks per month group and the ≥5 migraine attacks per month group. All subjects underwent complete ophthalmological and neurological examinations before measurements. Retinal vessel diameters and choroidal thickness were examined with the Spectralis OCT.

RESULTS

The mean diameters of the arteries in the eyes on the headache side of control group, ≥5 migraine attacks per month and ≤2 migraine attacks per month group at 480 µm from the optic disk (Raster 3) were 119.54±46.69, 136.68±25.93 and 119.34±31.75 µm respectively with a steady decline to 105.57±32.15, 118.18±31.87 and 108.05±38.77 µm at 1440 µm (Raster 7), the last measurement point, respectively. The retinal artery diameter measurements were significantly increased in ≥5 migraine attacks per month patients at four out of five measured points compared to control group (P<0.05). There were no statistical differences at any of the points of vein measurements. The choroidal thickness measurements were significantly decreased in ≥5 migraine attacks per month patients at all measured points compared to control group (P<0.05).

CONCLUSION

The retinal artery diameter is found to increase significantly and the choroidal thickness is found to decrease in the eyes on the headache side in ≥5 migraine attacks per month patients compared to control group.

Gray matter changes related to medication overuse in patients with chronic migraine

Objective

The objective of this article is to investigate the neurological substrates associated with medication overuse (MO) in patients with chronic migraine (CM).

Methods

We recruited age- and sex-matched CM patients with MO (CMwMO), CM patients without MO (CMwoMO), and healthy controls (HCs). Magnetic resonance T1-weighted images were processed by voxel-based morphometry, and the findings were correlated with clinical variables and treatment responses.

Results

A total of 66 patients with CM (half with MO) and 33 HCs completed the study. Patients with CMwMO compared to the patients with CMwoMO showed gray matter volume (GMV) decrease in the orbitofrontal cortex and left middle occipital gyrus as well as GMV increase in the left temporal pole/parahippocampus. The GMV changes explained 31.1% variance of the analgesics use frequency. The patients who responded to treatment had greater GMV in the orbitofrontal cortex ( p = 0.028). Patients with CM (with and without MO), compared with HCs, had decreased GMV at multiple brain areas including the frontal, temporal and occipital lobes, precuneus and cerebellum.

Conclusions

Our study showed GMV changes in CMwMO patients compared to the CMwoMO patients. These three cerebral regions accounted for significant variance in analgesics use frequency. Moreover, the GMV of the orbitofrontal cortex was predictive of the response to MO treatments.

The role of purinergic signaling in the etiology of migraine and novel antimigraine treatment

Etiopathogenesis of migraine involves different structures of the central nervous system: the trigeminal nerve with nuclei located in the brain stem, vascular system, and the cerebral cortex as well as diverse mechanisms and pathological processes. The multidirectional action of purines in different cell types (blood vessels, neurons, and satellite glial cells) and through different types of purinergic receptors contributes to the etiopathogenesis of migraine pain. Adenosine triphosphate (ATP) and its derivatives are involved in initiation and propagation of migrenogenic signals in several ways: they participate in vasomotor mechanism, cortical spreading depression, and in fast transmission or cross-excitation based on the satellite glial cells in trigeminal ganglion. Contribution of purinergic signaling in the conduction of pain is realized through the activation of P1 and P2 receptors expressed widely in the central nervous system: on the neurons and glial cells as well as on the smooth muscles and endothelium in the vascular system. Therefore, the purinergic receptors can be an excellent target for pharmacologists constructing new antimigraine therapeutics. Moreover, the mechanisms facilitating ATP and adenosine degradation may prevent vasodilatation and thus avoid a secondary central sensitization during a migraine attack. Thus, agonists and antagonists of P receptors as well as ecto-enzymes metabolizing nucleotides/nucleosides could gain the growing attention as therapeutic agents.

Migraine and epilepsy: review of the literature

Migraine and epilepsy are disorders that are common, paroxysmal, and chronic. In many ways they are clearly different diseases, yet there are some pathophysiological overlaps, and overlaps in clinical symptomatology, particularly with regard to visual and other sensory disturbances, pain, and alterations of consciousness. Epidemiological studies have revealed that the two diseases are comorbid in a number of individuals. Both are now recognized as originating from electrical disturbances in the brain, although their wider manifestations involve the recruitment of multiple pathogenic mechanisms. An initial excess of neuronal activity in migraine leads to cortical spreading depression and aura, with the subsequent recruitment of the trigeminal nucleus leading to central sensitization and pain. In epilepsy, neuronal overactivity leads to the recruitment of larger populations of neurons firing in a rhythmic manner that constitutes an epileptic seizure. Migraine aura and headaches may act as a trigger for epileptic seizures. Epilepsy is not infrequently accompanied by preictal, ictal, and postictal headaches that often have migrainous features. Genetic links are also apparent between the two disorders, and are particularly evident in the familial hemiplegic migraine syndromes where different mutations can produce either migraine, epilepsy, or both. Also, various medications are found to be effective for both migraine and epilepsy, again pointing to a commonality and overlap between the two disorders.

Choroid thickness and ocular pulse amplitude in migraine during attack

AIM

To compare the choroidal thickness and ocular pulse amplitude (OPA) measurements obtained during the attack period in migraine patients and age and gender matched control group participants using high definition optical coherence tomography (OCT).

METHODS

Thirty eyes at the side of the headache of 30 subjects with a diagnosis of migraine with or without aura and unilateral migraine and 29 age and gender matched healthy participants were enrolled in this observational, cross-sectional study. OCT scans were performed to all participants. Choroidal thicknesses were measured at the fovea, 1500 μm nasal and 1500 μm temporal to the fovea. Intraocular pressure (IOP) and OPA were also measured.

RESULTS

The choroidal thickness measurements obtained during the attack period in migraine patients were (mean±SD) 279.82±35.87, 250.05±29.49, and 239.58±27.92 and in control group were 308.20±44.97, 276.95±41.39, and 281.60±41.38 at foveal, nasal, and temporal measurement points, respectively. Choroidal thickness significantly decreased according to the control group (P<0.05) at all measured points in migraine patients during attack. IOP (mean±SD) values were 16.71±3.26 and17.40±3.19 and OPA (mean±SD) values were 2.26±0.81 and 2.64±1.03 in migraine and control groups, respectively, and did not seem to be changed (P>0.05).

CONCLUSIONS

Choroidal thickness was found to be significantly decreased in unilateral migraine patients during the attack period when compared with the control group, whereas OPA did not change. The possible implications of these findings on the association between migraine and glaucoma are discussed.

Lack of association between oxidative stress-related gene polymorphisms and chronic migraine in an Italian population

Migraine patients present increased risks of vascular diseases such as high blood pressure, insulin resistance, metabolic syndrome, stroke and coronary heart disease. Oxidative stress (OS) is increasingly being studied in relation to the pathophysiology of migraine, stimulated by the described association with the most frequent migraine comorbidities. Because many of the gene-encoded players of the OS balance are characterized by functional polymorphisms, it is supposed that the individual genomic profile could affect susceptibility to OS and to related pathophysiological conditions. This study aimed to characterize a panel of 10 polymorphisms in 8 OS-related genes in a chronic migraine (CM) population and healthy controls, to recognize a genetic risk in the process of migraine chronification. The sample consisted of 45 healthy women and 96 women diagnosed with CM. No deviations from the Hardy-Weinberg equilibrium were detected, or in the overall population, or in the CM group or in the control group.

Making modern migraine medieval: men of science, Hildegard of Bingen and the life of a retrospective diagnosis

Charles Singer's retrospective diagnosis of Hildegard of Bingen as a migraine sufferer, first made in 1913, has become commonly accepted. This article uses Hildegard as a case study to shift our focus from a polarised debate about the merits or otherwise of retrospective diagnosis, to examine instead what happens when diagnoses take on lives of their own. It argues that simply championing or rejecting retrospective diagnosis is not enough; that we need instead to appreciate how, at the moment of creation, a diagnosis reflects the significance of particular medical signs and theories in historical context and how, when and why such diagnoses can come to do meaningful work when subsequently mobilised as scientific 'fact'. This article first traces the emergence of a new formulation of migraine in the nineteenth century, then shows how this context enabled Singer to retrospectively diagnose Hildegard's migraine and finally examines some of the ways in which this idea has gained popular and academic currency in the second half of the twentieth century. The case of Hildegard's migraine reminds us of the need to historicise scientific evidence just as rigorously as we historicise our other material and it exposes the cumulative methodological problems that can occur when historians use science, and scientists use history on a casual basis.

Studies on the pathophysiology and genetic basis of migraine

Migraine is a neurological disorder that affects the central nervous system causing painful attacks of headache. A genetic vulnerability and exposure to environmental triggers can influence the migraine phenotype. Migraine interferes in many facets of people's daily life including employment commitments and their ability to look after their families resulting in a reduced quality of life. Identification of the biological processes that underlie this relatively common affliction has been difficult because migraine does not have any clearly identifiable pathology or structural lesion detectable by current medical technology. Theories to explain the symptoms of migraine have focused on the physiological mechanisms involved in the various phases of headache and include the vascular and neurogenic theories. In relation to migraine pathophysiology the trigeminovascular system and cortical spreading depression have also been implicated with supporting evidence from imaging studies and animal models. The objective of current research is to better understand the pathways and mechanisms involved in causing pain and headache to be able to target interventions. The genetic component of migraine has been teased apart using linkage studies and both candidate gene and genome-wide association studies, in family and case-control cohorts. Genomic regions that increase individual risk to migraine have been identified in neurological, vascular and hormonal pathways. This review discusses knowledge of the pathophysiology and genetic basis of migraine with the latest scientific evidence from genetic studies.

Brainstem 1H-MR spectroscopy in episodic and chronic migraine

The pathogenesis of evolution from episodic migraine (EM) to chronic migraine (CM) has not yet been clearly determined. Some studies revealed that dysfunction of the brainstem may play a role. We aimed to determine the brainstem ¹H-MR spectroscopic (MRS) findings in episodic and chronic migraine. We recruited patients with EM, CM and controls. Patients with CM were divided into subgroups with and without medication overuse (MO). The ¹H-MRS metabolite ratios at the periaqueductal gray (PAG) and bilateral dorsal pons were measured and compared with those in controls. A total of 19 patients with EM, 53 patients with CM (with MO n = 30, without MO n = 23) and 16 control subjects completed the study. Patients with EM had the highest N-acetylaspartate (NAA)/creatine (Cr) ratio at the dorsal pons (right, P = 0.014; left, P = 0.034) in comparison with those of CM and controls. The latter two groups did not differ. Among migraine patients, NAA/Cr ratios at dorsal pons were inversely correlated with headache frequency (right, r = −0.350, P = 0.004; left, r = −0.284, P = 0.019) and intensity (right, r = −0.286, P = 0.019; left, r = −0.244, P = 0.045), but not disease duration. In contrast, the metabolite ratios did not differ at the PAG among the study groups. Of note, MO was not associated with brainstem MRS ratios in patients with CM. The increased NAA/Cr levels may suggest neuronal hypertrophy at the dorsal pons in EM. A progressive dysfunction of this region may occur from EM to CM since the levels declined with increasing headache frequency and intensity.

Headache endocrinological aspects

In this chapter we review the current understanding of how hormones, neurohormones, and neurotransmitters participate in the pain modulation of primary headaches. Stressful conditions and hormones intimately implicated in headache neurobiology are also discussed. With the recent progress in neuroimaging techniques and the development of animal models to study headache mechanisms, the physiopathology of several of the primary headaches is starting to be better understood. Various clinical characteristics of the primary headaches, such as pain, autonomic disturbances, and behavioral changes, are linked to hypothalamic brainstem activation and hormonal influence. Headache is greatly influenced by the circadian circle. Over the millennia the nervous system has evolved to meet changing environmental conditions, including the light-dark cycle, in order to ensure survival and reproduction. The main elements for synchronization between internal biological events and the external environment are the pineal gland and its main secretory product, melatonin. Melatonin is believed to be a significant element in migraine and in other headache disorders, which has implications for treatment. A potential therapeutic use of melatonin has been considered in several headache syndromes. In short, primary headaches are strongly influenced by physiological hormonal fluctuations, when nociceptive and non-nociceptive pathways are differentially activated to modulate the perception of pain.

Barriers to satisfactory migraine outcomes. What have we learned, where do we stand?

Barriers to optimal migraine care have traditionally been divided into a number of categories: under-recognition and underconsultation by migraine sufferers; underdiagnosis and undertreatment by health care professionals; lack of follow-up and treatment optimization. These "traditional" barriers have been recognized and addressed for at least 15 years. Epidemiologic studies suggest that consultation, diagnosis, and treatment rates for migraine have improved although many migraine sufferers still do not get optimal treatment. Herein, we revisit the problem, review areas of progress, and expand the discussion of barriers to migraine care. We hypothesize that the subjective nature of pain and difficulty in communicating it contributes to clinical and societal barriers to care. We then revisit some of the traditional barriers to care, contrasting rates of recognition, diagnosis, and treatment over the past 15 years. We follow by addressing new barriers to migraine care that have emerged as a function of the knowledge gained in this process.