Genetic loading in familial migraine with aura

Aeromedical Risk of Migraine

INTRODUCTION: Migraine is a common condition that can carry considerable risk to aeromedical duties. Because randomized controlled trials are not an appropriate method to evaluate flight safety risk for medical conditions that may cause subtle or sudden incapacitation, the determination of fitness-to-fly must be based on risk assessments informed by extrapolated evidence. Therefore, we conducted a review of current literature to provide background information to inform the aeromedical risk assessment of migraine using a risk matrix approach.METHODS: We identified studies on topics pertinent to conducting an aeromedical risk assessment of migraine. We generated an overview of the literature synthesizing the findings of articles retrieved from searches of Scopus, Ovid, PubMed, and the Cochrane Library published in English from all years, in both general and aircrew populations. International headache and neurology guidelines, as well as headache policies from the U.S. Air Force, were also reviewed.RESULTS: This review includes information on the following topics relevant to conducting an evidence-based risk assessment of migraine: diagnosis, prevalence, incidence, natural course, clinical presentation, triggers, comorbidities, neuroimaging, implications of family history, and efficacy of pharmacological and nonpharmacological therapies.DISCUSSION: This review summarizes current literature on migraine for use in a risk matrix approach to the aeromedical assessment of migraine in prospective and current aircrew. Awareness of the most current epidemiological data related to a variety of migraine parameters facilitates an evidence-based risk assessment of migraine in aircrew and requires iterative updates as new information becomes available.Mainland RL, Skinner CR, Saary J. Aeromedical risk of migraine. Aerosp Med Hum Perform. 2024; 95(2):101-112.

Sex Differences in the Transmission of Migraine

Consistent evidence demonstrates that migraine is far more common in women than in men, but the explanations for this preponderance have not been systematically evaluated. We examined whether the female preponderance is attributable to genetic factors using data from a controlled family study which included 260 probands and their 1232 first-degree adult relatives. We found that although the risk of migraine was three times greater among the relatives of probands with migraine compared with controls, there was no differential risk of migraine among the relatives of male vs. female probands with migraine. Taking these data together with other family studies, we conclude that the increased risk of migraine in females is likely to result from increased exposure to non-familial endogenous or exogenous risk factors for migraine that lower the threshold for expression of migraine in women.

Chromosome 1p36 in migraine with aura: association study of the 5HT(1D) locus

Migraine with aura (MA) may share some but not all risk factors with other forms of migraine. As common migraine without aura (MO) has been associated with the chromosome 1p36 locus, we tested its involvement in MA by using two-point parametric linkage analysis to analyze 64 multiplex MA families. A logarithm of the odds score of 1.9 was suggestive of chromosome 1p36 linkage to MA. The transmission disequilibrium test analysis was then performed in 79 nuclear families with one MA parent and one MA offspring. We identified the presence of genetic association at chromosome 1p36 with MA (P=0.045, Bonferroni corrected): the locus encoding the 5HT(1D) receptor gene. Although these data suggest that the 1p36 locus may protect against MA, consistent with the role of the 5HT(1D) receptor in migraine treatment with triptan drugs, the study is subject to the limitations associated with studying a small number of affected families. As a result, we contrast evidence suggesting that the chromosome 1p36 locus is strongly MO associated with our finding that 1p36 has a more limited contribution to MA in the families we analyzed. Further work using a genome-wide association study approach in familial typical migraine, consisting of those affected by MO or MA, will serve to further distinguish how and why MA differs from MO.

Animal models of headache: from bedside to bench and back to bedside

In recent years bench-based studies have greatly enhanced our understanding of headache pathophysiology, while facilitating the development of new headache medicines. At present, established animal models of headache utilize activation of pain-producing cranial structures, which for a complex syndrome, such as migraine, leaves many dimensions of the syndrome unstudied. The focus on modeling the central nociceptive mechanisms and the complexity of sensory phenomena that accompany migraine may offer new approaches for the development of new therapeutics. Given the complexity of the primary headaches, multiple approaches and techniques need to be employed. As an example, recently a model for trigeminal autonomic cephalalgias has been tested successfully, while by contrast, a satisfactory model of tension-type headache has been elusive. Moreover, although useful in many regards, migraine models are yet to provide a more complete picture of the disorder.

Familial risks for common diseases: etiologic clues and guidance to gene identification

Familial clustering of a disease is a direct indicator of a possible heritable cause, provided that environmental sharing can be excluded. If the familial clustering is lacking, the likelihood of a heritable influence is also small. In the era of genome scans, the consideration of data on heritability should be important in the assessment of the likely success of the genome scan. The availability of a Multigeneration Register in Sweden provides a reliable access to families throughout the last century. This Register has been extensively used to study a number of different diseases through linkage to the Hospital Discharge Register. In the present article we review the obtained and some unpublished results for nine main disease classes. For each of these, familial risks are given for four disease subtypes. As measures of familial clustering we use risks between siblings, twins and spouses. Disease correlation between spouses suggests environmental sharing and a higher correlation between siblings and particularly twins shows heritable effects. We will also comment on the established susceptibility genes and the risks conferred by them. The data suggest high heritabilities for chronic obstructive pulmonary disease, asthma, noninfective enteritis and colitis, cerebral palsy and endocrine and metabolic diseases. Among the performed first-generation genome scans on various diseases, the success appears to be related to the a priori heritability estimates. To our knowledge this is a first attempt to summarize familial risks for a large number of diseases using data from a single population on which reasonable uniform diagnostic criteria have been applied.

Genetic biomarkers for migraine

Biomarkers are physical signs or laboratory measurements that occur in association with a pathological process and have putative diagnostic and/or prognostic utility. In migraine, clinical, radiological, and biochemical biomarkers might be helpful to improve diagnosis, get insight in pathophysiology, and facilitate treatment choices. Genetic biomarkers are defined as genetic variations (mutations or polymorphisms) that can predict disease susceptibility, disease outcome, or treatment response. As yet, only a few genetic biomarkers for migraine are available. Mutations in 3 different genes responsible for familial hemiplegic migraine, a monogenetic subtype of migraine with aura, and the MTHFR C677T polymorphism in common forms of migraine are clear examples. Many positive findings from linkage studies and association studies in common forms of migraine have not been replicated, and are therefore of less clinical use. In this review, we will discuss genetic biomarkers in migraine.

Epilepsy and migraine headache: is there a connection?

INTRODUCTION

This study investigated the prevalence of migraine headache in pediatric patients with epilepsy and the incidence of these two disorders in the family history.

METHOD

A retrospective chart review was conducted on 475 patients with a primary diagnosis of epilepsy between January 2003 and June 2004. The patients were managed in a pediatric neurology outpatient clinic at a major teaching hospital. Cases were selected using the ICD-9-CM definition for epilepsy. Data collected included age, sex, headache, migraine, and family history.

RESULTS

The study revealed a higher prevalence of migraine in epilepsy patients (14.7%) than in the general population (2.7% to 11%). Only 4.7% had a family history of migraine, but 20.6% had a positive family history of epilepsy, supporting current ideas of the genetic etiology of some epilepsies.

DISCUSSION

This study specifically addressed epilepsy and migraine in children, but whenever a primary diagnosis is made, the potential for a coexisting disorder should be investigated.

The CACNA1A and ATP1A2 genes are not involved in dominantly inherited migraine with aura

Epidemiological studies indicate that migraine with typical aura (MA) has a major genetic component but the genes for MA have not been identified. However, the autosomal dominantly inherited familial hemiplegic migraine (FHM) is often caused by mutations in the CACNA1A or ATP1A2 genes. The aim of the study was to investigate if the CACNA1A or ATP1A2 genes are involved in MA with an apparently autosomal dominant mode of inheritance. From a clinic population diagnosed by a trained physician we recruited 34 extended families (comprising 174 MA patients) with an apparently autosomal dominant mode of inheritance of MA. We performed a linkage analysis of 161 of 174 MA patients and 79 unaffected relatives using a framework marker set of 44 markers for chromosome 1 and 22 markers for chromosome 19. Linkage analysis was made with a non-parametric or autosomal dominant parametric model, either allowing for heterogeneity or not, using an affected only analysis. We identified no linkage to CACNA1A and ATP1A2 loci on chromosome 19 or 1, respectively. Additionally, at least two patients from each family and 92 healthy, unrelated controls were selected for a sequence analysis. We sequenced the 48 exons of CACNA1A and the 23 exons of ATP1A2, including promoter and flanking intron sequences. No polymorphism was identified in the CACNA1A or ATP1A2 genes with a strong correlation to MA. Our study shows that the CACNA1A or ATP1A2 genes are probably not involved in MA. To identify the genes involved in the common forms of migraine, future genetic studies should focus on MA and migraine without aura (MO) and not FHM.

Implications of Clinical Subtypes of Migraine With Aura

OBJECTIVE

To compare the clinical characteristics of familial hemiplegic migraine (FHM), sporadic hemiplegic migraine (SHM), and nonhemiplegic migraine with aura (NHMA) and further, to compare subtypes of NHMA.

BACKGROUND

To discover distinct underlying genetic and pathophysiological mechanisms it is crucial to drive clinical subdivision of migraine with aura as far as possible. The documentation of subtypes of migraine with aura depends on the clinical characteristics as the genetic mechanisms are unknown except for the dominantly inherited FHM.

METHODS

Patients with FHM, SHM, or familial NHMA were recruited from specialist practice and diagnosed according to the International Classification of Headache Disorders (ICHD) in a validated interview by a physician. Patients with hemiplegic migraine had a physical and neurological examination. Patients with population-based NHMA from a previous Danish study were used for comparison.

RESULTS

We recruited 147 patients with FHM, 105 with SHM, and 362 with familial NHMA. FHM and SHM had similar aura and headache characteristics. Patients with FHM and SHM were more likely to experience two or more aura symptoms (100% vs. 31%, P < .0001), they more often had prolonged aura symptoms, they almost always had a headache associated with the aura (93% vs. 58%, P < .0001), and they more frequently had basilar-type symptoms (69% vs. 10%, P < .0001) than patients with population-based NHMA. Patients with familial NHMA were more likely to experience two or more aura symptoms than patients with population-based NHMA (61% vs. 32%, P < .0001). Within the subtypes of NHMA, patients with typical aura with migraine headache had an earlier age at onset (20 +/- 10 vs. 23 +/- 13 years, P= .044) and a higher co-occurrence of migraine without aura (43% vs. 22%, P= .002) than patients with typical aura with nonmigraine headache.

CONCLUSIONS

The present study proves that distinct subtypes of migraine with aura exist. It further underlines the phenotypic differences between the different subtypes of migraine with aura which likely are caused by different etiological mechanisms. In future studies FHM, SHM, and NHMA therefore should be analyzed as separate entities and patients with NHMA may be stratified by ICHD-2 subtype of NHMA.

Familial risks for migraine and other headaches among siblings based on hospitalizations in Sweden

Migraine and other headaches are common disabling conditions, reducing the quality of life in the affected individuals. The unambiguous definition of familial risk for subtypes of migraine and other headaches will advance the search for the heritable causes of these conditions and their underlying mechanisms. We aim at defining familial risks for siblings to be hospitalized because of migraine or other headaches. An ad hoc migraine database was constructed by linking the Multigeneration Register on 0- to 69-year-old siblings to the Hospital Discharge Register for data on migraines of all hospitalized patients in Sweden from years 1987 to 2001. Standardized incidence ratios (SIRs) were calculated for affected sibling pairs by comparison with those whose siblings had no migraine. Among a total of 14,123 hospitalized patients, 205 affected siblings were identified, with a familial SIR of 2.84. SIRs for migraine with and without aura were 3.08 and 2.67, respectively. The highest familial risk of 3.71 was noted for unspecified migraine. The risk tended to be higher for concordant (both siblings sharing the migraine subtype, ranging from 4.0 to 6.0) than discordant subtypes, but even many discordant SIRs were significant. The SIR for spouse correlation was 1.14 for husbands and 1.22 for wives, far from being significant. All subtypes of hospitalized migraines and other headaches show an increased familial risk, at least in specific age groups. The different subtypes appear to share susceptibility, which may imply common disease mechanisms.

New international classification of migraine with aura (ICHD-2) applied to 362 migraine patients

The International Classification of Headache Disorders 2nd edition (ICHD-2) subdivides migraine with aura (MA) differently from the ICHD-1 and includes new diagnostic criteria. The aim of the present study was to evaluate how the new classification works in practice and in comparison with the ICHD-1. The patients were recruited from a screen of the Danish National Patient Registry and from Danish neurologists. We included 362 patients diagnosed with MA according to the ICHD-1 in a validated semistructured physician-conducted interview. According to the ICHD-2, 89% (322 of 362) had MA and 11% (40 of 362) had probable MA. The MA patients had one or more ICHD-2 subtype of MA: 54% (173 of 322) had typical aura with migraine headache (MA-MH), 40% (129 of 322) had typical aura with non-migraine headache (MA-NMH), 37% (120 of 322) had aura without headache (MA-WOH), and 7% (26 of 322) had basilar-type migraine (MA-B). Of patients with MA-MH 34% (59 of 173) had co-occurrence of MA-WOH, 9% (16 of 173) had co-occurrence of MA-B and 5% (8 of 173) had co-occurrence of both MA-WOH and MA-B. Of patients with MA-NMH 27% (35 of 129) had co-occurrence of MA-WOH. Only 6% (18 of 322) of the MA patients had exclusively MA-WOH and <1% (2 of 322) had exclusively MA-B. Patients with MA-MH had an earlier age at onset (P = 0.044), an increased lifetime number of MA attacks (P = 0.054) and a higher co-occurrence of migraine without aura (P = 0.002) than patients with MA-NMH. Patients with MA-B tended to have an earlier age at onset and more severe attacks and patients with MA-WOH had a higher age at onset and less severe attacks than patients with MA-MH. The variations between ICHD-2 subtypes of MA indicate that patients with similar subtype of MA share phenotype and very likely have similar underlying aetiology.

Recent findings in headache genetics

PURPOSE OF REVIEW

The progress in headache genetics, especially migraine genetics, recently jumped ahead with some major discoveries.

RECENT FINDINGS

Family and epidemiological studies further strengthen the genetic contribution to migraine and two recent observations gave new molecular insights in the disease. Studies on the genetics of familial hemiplegic migraine revealed, in addition to the previously identified familial hemiplegic migraine type 1 gene CACNA1A on chromosome 19, the familial hemiplegic migraine type 2 gene ATP1A2, encoding the alpha2-subunit of sodium/potassium pumps. Recent genome screens in families with migraine identified susceptibility loci on chromosomes 4, 6, 11 and 14.

SUMMARY

The findings in familial hemiplegic migraine confirm that dysfunction in ion transport is a key factor in migraine pathophysiology and might help us in the elucidation of migraine molecular pathways. The identification of several migraine susceptibility loci underline its genetically complex nature.