Migraine genetics

Botulinum Toxin a Valuable Prophylactic Agent for Migraines and a Possible Future Option for the Prevention of Hormonal Variations-Triggered Migraines

BACKGROUND

In 1989, Botulinum toxin (BoNT) was accepted by the FDA for the management of some ophthalmic disorders. Although it was initially considered a lethal toxin, in recent times, Botulinum toxin A (BoNT-A), which is the more used serotype, has expanded to cover different clinical conditions, primarily characterized by neuropathic pain, including migraines and headaches. Evidence suggests that migraines are influenced by hormonal factors, particularly by estrogen levels, but very few studies have investigated the prevalence and management strategies for migraines according to the hormonal status. The effects of several therapeutic regimens on migraines have been investigated, but the medications used varied widely in proven efficacies and mechanisms of action. BoNT-A is increasingly used in the management of migraine and several placebo-controlled trials of episodic and chronic migraine are currently underway. This paper is a review of the recently published data concerning the administration of BoNT-A in the prevention of chronic migraines. Considering the lack of population-based studies about the effectiveness of BoNT-A in the alleviation of premenstrual and perimenopausal migraines, this study proposes a new perspective of the therapeutic approach of migraine syndrome associated with menopausal transition and the premenstrual period.

METHODS

We selected the reviewed papers from CrossRef, PubMed, Medline, and GoogleScholar, and a total of 21 studies met our inclusion criteria.

RESULTS

To date, no specific preventive measures have been recommended for menopausal women with migraines. BoNT-A often reduces the frequency and intensity of migraine attacks per month; the treatment is well tolerated and does not exhibit a significantly higher rate of treatment-related side effects. No population-based studies were conducted in order to highlight the role of BoNT-A in menopause-related migraines, neither in menstrual migraines.

CONCLUSION

There is a need for further research in order to quantify the real burden of menstrual and perimenopausal migraines and to clarify if BoNT-A could be used in the treatment of refractory postmenopausal and premenstrual migraines.

Differential effect of FHM2 mutation on synaptic plasticity in distinct hippocampal regions

INTRODUCTION

Familial hemiplegic migraine 2 is a pathology linked to mutation of the ATP1A2 gene producing loss of function of the α2 Na⁺/K⁺-ATPase (NKA). W887R/+ knock-in (KI) mice are used to model the familial hemiplegic migraine 2 condition and are characterized by 50% reduced NKA expression in the brain and reduced rate of K⁺ and glutamate clearance by astrocytes. These alterations might, in turn, produce synaptic changes in synaptic transmission and plasticity. Memory and learning deficits observed in familial hemiplegic migraine patients could be ascribed to a possible alteration of hippocampal neuronal plasticity and measuring possible changes of long-term potentiation in familial hemiplegic migraine 2 KI mice might provide insights to strengthen this link.

RESULTS

Here we have investigated synaptic plasticity in distinct hippocampal regions in familial hemiplegic migraine 2 KI mice. We show that the dentate gyrus long-term potentiation of familial hemiplegic migraine 2 mice is abnormally increased in comparison with control animals. Conversely, in the CA1 area, KI and WT mice express long-term potentiation of similar amplitude.

CONCLUSIONS

The familial hemiplegic migraine 2 KI mice show region-dependent hippocampal plasticity abnormality, which might underlie some of the memory deficits observed in familial migraine.

Children with allergic diseases have an increased subsequent risk of migraine upon reaching school age

The association between migraine and allergy has remained a subject of debate for more than a century. To systemically investigate the interaction between children with antecedent allergic diseases and their future risks of migraine on reaching school age, we recruited 16,130 children aged 7-18 with migraine diagnosed between 2000 and 2008, and 64,520 matched controls without a history of migraine. The ORs of migraine were calculated for the association with allergic diseases diagnosed before migraine diagnosis. The allergic diseases included atopic dermatitis, allergic conjunctivitis, allergic rhinitis (AR), and asthma. Children with preceding allergic diseases had a greater subsequent risk of migraine than the controls. Among the four evaluated diseases, AR had the highest adjusted OR (aOR) of 2.17 (95% CI 2.09 to 2.26). Children with all four allergic diseases had the highest aOR of 3.59 (95% CI 2.91 to 4.44). Further, an increasing trend of aORs was observed with more allergic disease-associated medical consulting. Our study indicates that children with allergic diseases are at increased subsequent risk of migraine when they reach school age, and the risk shows a cumulative effect of more allergic diseases and more allergy-related healthcare.

Association of single nucleotide polymorphisms of CACNA1A gene in migraine

INTRODUCTION:

Migraine is a chronic, neurovascular polygenic disease where genetic and environmental factors are involved in its etiology. Dysfunction of neuronal ion transportation can provide a model for predisposition for common forms of migraine. Mutations in genes encoding ion channels disturb the rhythmic function of exposed tissue that may also explain the episodic nature of migraine. Our aim was to study the single nucleotide polymorphisms of CACNA1A gene in migraine patients.

MATERIALS AND METHODS:

The subjects were the patients of migraine, in the age range of 18-80 years, diagnosed by a Neurologist, as per the diagnostic criteria of International Headache Society (IHS) Classification 2004 after excluding other causes of headache by clinical examination and relevant investigations.

The controls were the age and sex matched healthy persons from the same population excluding the relatives of patients. Only those patients and the controls, who voluntarily participated in the study, were taken and their blood samples were taken for the study. Deoxyribonucleic acid (DNA) extraction was performed according to the manufacturer's protocol for Qiagen DNA extraction kits (Qiagen, Hilden, NRW, Germany). DNA content was quantified by spectrophotometric absorption (Nanodrop Spectrophotometer, BioLab, Scoresby, VIC, Australia). Polymerase chain reaction was performed using an iCycler Thermal Cycler (Bio.Rad, Hercules, CA, USA). The polymorphic analysis of CACNA1A gene was carried out by two methods: Restriction fragment length polymorphism and sequencing.

RESULTS:

The study included a total of 25 patients of migraine, diagnosed on out-patient department basis as per IHS Classification 2004 and compared with age and sex matched 25 healthy controls. Most of the patients 23 (92%) were below the age of 50 years. 20 of the patients (80%) were females and 5 (20%) were males. The polymorphic analysis of CACNA1A gene revealed the presence of only the wild form of the gene for the codon E993V in both case and control groups.

CONCLUSION:

In our study, we could not find any polymorphism of CACNA1A gene in the selected patients. Instead the wild type of genotype was found in both patients and controls. This negative result presented here, implies that if the CACNA1A gene is involved in typical migraine (with and without aura), its contribution is very modest and therefore difficult to discern. Nevertheless, there are other genes that could be considered potential candidates for typical migraine susceptibility for which further research is needed.

Pediatric migraine: abortive management in the emergency department

Studies suggest that headache accounts for approximately 1% of pediatric emergency department (ED) visits. ED physicians must distinguish between primary headaches, such as a tension or migraine, and secondary headaches caused by systemic disease including neoplasm, infection, or intracranial hemorrhage. A recent study found that 40% of children presenting to the ED with headache were diagnosed with a primary headache, and 75% of these were migraine. Once the diagnosis of migraine has been made, the ED physician is faced with the challenge of determining appropriate abortive treatment. This review summarizes the most recent literature on pediatric migraine with an emphasis on diagnosis and abortive treatment in the ED.

Amino acid changes in the amino terminus of the Na,K-adenosine triphosphatase alpha-2 subunit associated to familial and sporadic hemiplegic migraine

Familial hemiplegic migraine (FHM) is a rare subtype of migraine with aura inherited with an autosomal dominant pattern. Here, we report the genetic analysis of four families and one sporadic case with hemiplegic migraine (HM) in whom we searched for mutations in the three genes associated with the disease CACNA1A, ATP1A2 and SCN1A. Two novel amino acid changes p.Arg65Trp and p.Tyr9Asn, in the Na,K-adenosine triphosphatase (ATPase) alpha-2 subunit encoded by the ATP1A2 gene, were found in one FHM family and in the sporadic case, respectively. These mutations are peculiar for their location in the extreme N-terminus, an uncommon mutation target in this protein. Low frequency of migraine attacks in all our mutant patients with low complexity of the associated aura symptoms in the sporadic case is also observed. Besides the two novel mutations, the data here reported confirm the involvement of ATP1A2 gene in the sporadic form of HM, while the negative results on the other families tested for all genes known in HM strengthen the hypothesis of the existence of at least another locus involved in FHM.

Interictal alterations of the trigeminal somatosensory pathway and periaqueductal gray matter in migraine

Migraine has been traditionally considered a nonprogressive, paroxysmal disorder with no brain abnormalities between attacks. We used diffusion tensor imaging to examine interictal diffusion properties of the brains of migraineurs with aura, migraineurs without aura and matched healthy controls. Areas of lower fractional anisotropy were present in migraineurs along the thalamocortical tract. In addition, migraineurs with aura had lower fractional anisotropy in the ventral trigeminothalamic tract, and migraineurs without aura had lower fractional anisotropy in the ventrolateral periaqueductal grey matter. Our results indicate the presence of permanent interictal changes in migraineurs, pointing to an effect of migraine on the trigeminal somatosensory and modulatory pain systems.

Transcranial direct current stimulation reveals inhibitory deficiency in migraine

The issue of interictal excitability of cortical neurons in migraine patients is controversial: some studies have reported hypo-, others hyperexcitability. The aim of the present study was to observe the dynamics of this basic interictal state by further modulating the excitability level of the visual cortex using transcranial direct current stimulation (tDCS) in migraineurs with and without aura. In healthy subjects anodal tDCS decreases, cathodal stimulation increases transcranial magnetic stimulation (TMS)-elicited phosphene thresholds (PT), which is suggested as a representative value of visual cortex excitability. Compared with healthy controls, migraine patients tended to show lower baseline PT values, but this decrease failed to reach statistical significance. Anodal stimulation decreased phosphene threshold in migraineurs similarly to controls, having a larger effect in migraineurs with aura. Cathodal stimulation had no significant effect in the patient groups. This result strengthens the notion of deficient inhibitory processes in the cortex of migraineurs, which is selectively revealed by activity-modulating cortical input.

A novel ATP1A2 mutation in a family with FHM type II

Familial hemiplegic migraine (FHM) is a rare subtype of migraine with aura with an autosomal dominant pattern of inheritance. Six FHM families underwent extensive clinical and genetic investigation. The authors identified a novel ATP1A2 mutation (E700K) in three patients from one family. In the patients, attacks were triggered by several factors including minor head trauma. In one subject a 3-day coma developed after a cerebral angiography. Overall, the phenotype of the patients closely resembles that of previously reported cases of FHM type II. The E700K variant might be regarded as the cause of the disease in this family, but this was not tested functionally.

Association of migraine and ESR1 G325C polymorphism

Migraine is a genetically complex disorder in which sexual hormones influence the phenotype. ESR1 G594A polymorphism has been associated with migraine in Australians. We performed a case-control study with G594A and G325C polymorphisms to determine whether ESR1 is associated with migraine in our population. An association between G594A and migraine could not be demonstrated here. By contrast, we observed that the C325 allele conferred a 1.6 (95% confidence interval=1.1-2.4) higher risk for suffering from migraine in women than the G allele. Women carrying the C352C genotype were over 3 times more likely to suffer from migraine than those carrying the G325G genotype. Therefore, we conclude that ESR1 G325C polymorphism is associated with migraine in our population.

Etiology of primary headaches: the importance of genes and environment

Results from twin studies show that genes play an important role for susceptibility to migraine. The propensity for migraine to run in some families but not in others arises predominantly from alleles shared by family members and not the shared family environment, and that environmental influences on migraine are unique to the affected family member. The main genetic and environmental architecture for the other two major primary headaches, tension-type and cluster, remains to be elucidated. This review focuses on recent advances in twin studies of primary headaches and the future prospects are outlined.

Molecular Pharmacology of Topiramate: Managing Seizures and Preventing Migraine

Topiramate is a neuromodulatory compound with stabilizing properties that was initially introduced for the management of partial seizures. Topiramate has been demonstrated to modify several receptor-gated and voltage-sensitive ion channels, including voltage-activated Na+ and Ca2+ channels and non-NMDA receptors. These receptors have been implicated in the pathophysiology of both epilepsy and migraine. The pharmacological mechanisms of action for topiramate that may explain its antiepileptic and migraine preventive activities will be discussed in this review. In addition, the potential relationship between the molecular activities of topiramate and its efficacy in epilepsy and migraine prevention will be emphasized.

A Highly Polymorphic Poly-Glutamine Stretch in the Potassium Channel KCNN3 in Migraine

OBJECTIVE

The present study is designed to further elucidate the molecular genetic basis of migraine with and without aura.

BACKGROUND

Migraine is a common disease of as yet unknown etiology. Interest in ion channels in migraine has been spurred by molecular genetic findings in familial hemiplegic migraine, since familial hemiplegic migraine type 1 is caused by mutations in the calcium channel gene CACNA1A.

METHODS

Given this role of ion channels in migraine, we assessed the potassium channel KCNN3 as a candidate gene for common migraine. We analyzed the highly polymorphic repeat region coding for a poly-glutamine stretch, which constitutes part of the cytoplasmic tail of the channel protein.

RESULTS

We found an excess of the allele coding for 15 poly-glutamines in migraine patients.

CONCLUSIONS

The potassium channel KCNN3 may thus be of pathophysiological importance in migraine with and without aura.

Familial retinal migraines

Approximately 25% of sufferers of retinal migraine are thought to have a positive family history. Retinal migraines can cause both transient, and rarely permanent, unilateral monocular visual loss. This report of familial retinal migraines furthers our understanding of this particular migraine subtype. Two families with retinal migraines are reported suggesting an autosomal-dominant inheritance pattern with variable expression and penetrance.

The molecular genetics of migraine

Within the past decade it has been possible to identify susceptibility gene loci that predispose to migraine using genetic markers distributed across the human genome. Five new loci with significant linkage to common types of migraine--migraine with or without aura--have been identified on four different chromosomes using a genome-wide screen approach. So far, only the locus on 4q has been replicated but no specific, disease-causing mutations have been described in these common forms of migraine. The best genetic evidence providing molecular insight into migraine still comes from the mutations detected in a rare Mendelian form of migraine with aura--familial hemiplegic migraine (FHM). In 50%-70% of FHM families, mutations in the calcium channel gene CACNA1A in chromosome 19p13 have been identified. In some families, mutations in the ATP1A2 gene encoding the alpha2 subunit of the Na+, K+-ATPase are associated with FHM, linked to 1q23. Here we discuss the current knowledge of the heritability of migraine and rare migraine variants as models for understanding the pathophysiology of common migraine and animal models that might contribute to understanding common forms of migraine.

Migraine: an ophthalmologist's perspective

PURPOSE OF REVIEW

Migraine is a common disorder with visual and neurologic manifestations. Many patients present to ophthalmologists without a previous diagnosis of migraine. It is therefore essential for the ophthalmologist to have a good understanding of migraine to appropriately help these patients. Neurologic syndromes with migraine and retinopathy are well known. Here again, the ophthalmologist may play a role in establishing the correct diagnosis.

RECENT FINDINGS

For long the initial changes during a migraine attack have been shown to occur in the occipital cortex. In the recent years, the understanding of migraine has advanced with the availability of functional neuroimaging. A possible role of brainstem structures in the initiation of migraine attacks has been proposed based on functional magnetic resonance imaging blood oxygenation level-dependent signals. Activation of brainstem structures preceded activation of occipital cortex. Our understanding of cortical spreading depression is also advancing. Using multiwavelength optical intrinsic imaging, cortical spreading depression has been shown to have a triphasic response in rats. For the first time it has been shown that the cortical spreading depression activated the trigeminovascular system, which is followed by a series of cortical meningeal and brainstem events that cause the migraine headache. Sildenafil has been shown to induce migraine attack without dilation of cerebral blood vessels, further confirming that Wolf's vasogenic theory may not be true. Several loci for migraine have been identified in recent years. A new locus for migraine with and without aura has been identified on chromosome 6, a locus for migraine without aura to chromosome 14, and a locus for migraine with aura on chromosome 4.

SUMMARY

Our understanding of migraine is rapidly evolving with functional neuroimaging. There are several unanswered questions. In this article, we will review the epidemiology, genetics, and clinical features of various forms of migraine with emphasis on ocular migraine, pathogenesis, and briefly the management of migraine.