Migraine: a complex genetic disorder

Preventive agents for migraine: focus on the antiepileptic drugs

Migraine is among the 10 most disabling disorders worldwide. It is characterized by episodes of moderate or severe headaches with various degree of disability, resulting in a considerable health burden upon the sufferers and their family. The objective of this article is to review the use of prophylaxis with antiepileptic drugs. Particular focus is given to their mechanism of action, metabolism, pharmacokinetics, safety profile, efficacy and to provide a summary of the most relevant clinical studies and patient preference.

Tumour necrosis factor gene polymorphisms and migraine: a systematic review and meta-analysis

BACKGROUND

Data on the association between TNFα and TNFβ gene polymorphisms and migraine are conflicting.

METHODS

We performed a systematic review and meta-analysis of studies published until January 2011. We used data from published papers and as provided after contact with the authors. We calculated study specific odds ratios (OR) and 95% confidence intervals (CI) assuming additive, dominant, and recessive genetic models as well as pooled effect estimates.

RESULTS

Among the ten studies identified, the best evidence is available for the TNFα -308G>A and TNFβ 252A > G polymorphisms indicating no overall association with migraine. Subgroup analyses suggested that the A allele of the TNFα -308G > A variant more than doubles the risk for migraine among populations with a heterogeneous ethnic background, which was driven by associations for migraine without aura (additive model: pooled OR = 2.87, 95% CI 1.86-4.43). Further, the risk for migraine with aura was increased among Asian populations (additive model: pooled OR = 1.71, 95% CI 1.07-2.71). Both observed effects were stronger among females than males.

CONCLUSIONS

Our results indicate no overall association between TNFα and TNFβ gene variants and migraine. However, associations differed among specific populations. Our findings need to be treated with caution and further targeted research is warranted to evaluate population-specific effects including population stratification.

Association analysis of STX1A gene variants in common forms of migraine

OBJECTIVES

To examine the association of genetic variants in the syntaxin 1A gene (STX1A) with common forms of migraine, and perform a combined analysis of the data from the current study and previously published reports.

METHODS

We investigated the parent-to-offspring transmission of rs6951030, rs4363087 and rs2293489 in 191 family trios, each with a proband with childhood-onset migraine, and performed a case-control analysis between the probands and 223 unrelated controls. In addition, we performed a combined data analysis with an overall sample of 567 migraine patients and 720 unrelated controls and performed a migraine-specific gene-network analysis.

RESULTS

The transmission disequilibrium test revealed significant transmission distortion of rs4363087 in migraine overall (OR = 1.56, p = 0.006; p = 0.01 after correction for multiple testing) and migraine without aura (OR = 1.58, p = 0.01; corrected p = 0.04). Two-marker haplotype analysis revealed transmission distortion of A-G (rs6951030-rs4363087; OR = 1.47, p = 0.01) and A-C (rs4363087-rs2293489; OR = 0.66, p = 0.01). Combined analysis showed significant association of rs941298 with migraine overall (OR = 1.28, p = 0.004) and migraine without aura (OR = 1.3, p = 0.008). Network analysis identified 24 genes relating STX1A to other migraine candidate genes, including KCNK18 (TRESK channel) involved in the cytoplasmatic calcium signalling together with syntaxin 1A.

CONCLUSION

Our results provide support for the hypothesis that STX1A represents a susceptibility gene for migraine.

Genetics of migraine in the age of genome-wide association studies

Genetic factors importantly contribute to migraine. However, unlike for rare monogenic forms of migraine, approaches to identify genes for common forms of migraine have been of limited success. Candidate gene association studies were often negative and positive results were often not replicated or replication failed. Further, the significance of positive results from linkage studies remains unclear owing to the inability to pinpoint the genes under the peaks that may be involved in migraine. Problems hampering these studies include limited sample sizes, methods of migraine ascertainment, and the heterogeneous clinical phenotype. Three genome-wide association studies are available now and have successfully identified four new genetic variants associated with migraine. One new variant (rs1835740) modulates glutamate homeostasis, thus integrates well with current concepts of neurotransmitter disturbances. This variant may be more specific for severe forms of migraine such as migraine with aura than migraine without aura. Another variant (rs11172113) implicates the lipoprotein receptor LRP1, which may interact with neuronal glutamate receptors, thus also providing a link to the glutamate pathway. In contrast, rs10166942 is in close proximity to TRPM8, which codes for a cold and pain sensor. For the first time this links a gene explicitly implicated in pain related pathways to migraine. The potential function of the fourth variant rs2651899 (PRDM16) in migraine is unclear. All these variants only confer a small to moderate change in risk for migraine, which concurs with migraine being a heterogeneous disorder. Ongoing large international collaborations will likely identify additional gene variants for migraine.

Magnitude, impact, and stability of primary headache subtypes: 30 year prospective Swiss cohort study

OBJECTIVE

To determine the prevalence, impact, and stability of different subtypes of headache in a 30 year prospective follow-up study of a general population sample.

DESIGN

Prospective cohort study.

SETTING

Canton of Zurich, Switzerland.

PARTICIPANTS

591 people aged 19-20 from a cohort of 4547 residents of Zurich, Switzerland, interviewed seven times across 30 years of follow-up.

MAIN OUTCOME MEASURES

Prevalence of headache; stability of the predominant subtype of headache over time; and age of onset, severity, impact, family history, use of healthcare services, and drugs for headache subtypes.

RESULTS

The average one year prevalences of subtypes of headache were 0.9% (female:male ratio of 2.8) for migraine with aura, 10.9% (female:male ratio of 2.2) for migraine without aura, and 11.5% (female:male ratio of 1.2) for tension-type headache. Cumulative 30 year prevalences of headache subtypes were 3.0% for migraine with aura, 36.0% for migraine without aura, and 29.3% for tension-type headache. Despite the high prevalence of migraine without aura, most cases were transient and only about 20% continued to have migraine for more than half of the follow-up period. 69% of participants with migraine and 58% of those with tension-type headache manifested the same predominant subtype over time. However, the prospective stability of the predominant headache subtypes was quite low, with substantial crossover among the subtypes and no specific ordinal pattern of progression. A gradient of severity of clinical correlates and service use was present across headache subtypes; the greatest effect was for migraine with aura followed by migraine without aura, and then tension-type headache and unclassified headaches.

CONCLUSIONS

These findings highlight the importance of prospective follow-up of people with headache. The substantial longitudinal overlap among subtypes of headache shows the developmental heterogeneity of headache syndromes. Studies of the causes of headache that apply diagnostic nomenclature based on distinctions between discrete headache subtypes may not capture the true nature of headache in the general population.

Polymorphisms of the SCN1A gene in children and adolescents with primary headache and idiopathic or cryptogenic epilepsy: is there a linkage?

The purpose of this study was to evaluate the distribution of the polymorphisms of the SCN1A gene in a series of children and adolescents with primary headache and idiopathic or cryptogenic epilepsy compared to controls. Five non-synonymous exonic polymorphisms (1748A > T, 2656T > C, 3199A > G, 5771G > A, 5864T > C) of the SCN1A gene were selected and their genotyping was performed, by high resolution melting (HRM), in 49 cases and 100 controls. We found that among the five polymorphisms, only 3199A > G was a true polymorphism. We did not find a statistically significant difference between distribution of 3199A > G genotypes between cases and controls. We excluded the role of the SCN1A gene in the pathogenesis of comorbidity between headache (especially migraine) and epilepsy. The SCN1A gene is a major gene in different epilepsies and epilepsy syndromes; the HRM could be the new methodology, more rapid and efficacious, for molecular analysis of the SCN1A gene.

Association of 5-HTT gene polymorphisms with migraine: a systematic review and meta-analysis

BACKGROUND/AIMS

Serotonin is known to play an important role in the pathogenesis of migraine, but individual genetic association studies that examine the relationship between polymorphisms of serotonin transporter (5-HTT) gene and migraine have yielded inconsistent results. This study aimed to evaluate the association between 5-HTT gene variants (including 5-HTTLPR, VNTR and SNP) and migraine using systematic review with meta-analysis.

METHODS

Relevant studies were identified by searching English and Chinese databases extensively. Allele and genotype frequencies for each included study were extracted. The odds ratio (OR) was calculated using a random-effects or fixed-effects model. Q statistic was used to evaluate homogeneity, and Egger's test and Funnel plot were used to assess publication bias. For family-based association studies, a descriptive analysis was carried out.

RESULTS

A total of 15 studies were identified for meta-analysis. It was found that the 5-HTT VNTR Stin2.12 allele or 12/12 genotype had an increased risk for migraine in the general population (Stin2.12 allele: OR, 95% CI: 1.34, 1.09-1.64, p=0.006; 12/12 genotype: OR, 95% CI: 1.55, 1.17-2.05, p=0.002), but there was no significant association between migraine and 5-HTTLPR or SNP rs2020942.

CONCLUSIONS

Existing evidence indicates that the 5-HTT VNTR polymorphism (mainly the STin2.12 genotype) is associated with an increased risk of migraine in the general population. Future studies with larger sample sizes will be necessary to confirm the present results.

Towards an understanding of genetic predisposition to migraine

Plausible genome-wide associations for episodic neurological diseases (such as migraine, epilepsy and ataxias) have been slow to emerge. The first such association was reported in a recent genome-wide association study of migraine, with quantitative expression analysis linking the variant to a nearby regulatory gene, MTDH/AEG-1. This putative mechanism, regulating the expression of the primary glutamate transporter in the brain, EAAT2/GLT-1, has interesting implications bridging the gap between Mendelian and common forms in this key group of disorders.

Evidence for an association between migraine and the hypocretin receptor 1 gene

The aim of our study was to investigate whether genetic variants in the hypocretin receptor 1 (HCRTR1) gene could modify the occurrence and the clinical features of migraine. Using a case-control strategy we genotyped 384 migraine patients and 259 controls for three SNPs in the HCRTR1 gene. Genotypic and allelic frequencies of the rs2271933 non-synonymous polymorphism resulted different (χ(2)=9.872, p=0.007; χ(2)=8.108, p=0.004) between migraineurs and controls. The carriage of the A allele was associated with an increased migraine risk (OR 1.42, 95% CI 1.11-1.81). When we divided the migraine patients into different subgroups, the difference reached the level of statistical significance only in migraine without aura. The different genotypes had no significant effect on the examined clinical characteristics of the disease. In conclusion, our data supports the hypothesis that the HCRTR1 gene could represent a genetic susceptibility factor for migraine without aura and suggests that the hypocretin system may have a role in the pathophysiology of migraine.

Neurological channelopathies

Inherited ion channel mutations can affect the entire nervous system. Many cause paroxysmal disturbances of brain, spinal cord, peripheral nerve or skeletal muscle function, with normal neurological development and function in between attacks. To fully understand how mutations of ion channel genes cause disease, we need to know the normal location and function of the channel subunit, consequences of the mutation for biogenesis and biophysical properties, and possible compensatory changes in other channels that contribute to cell or circuit excitability. Animal models of monogenic channelopathies increasingly help our understanding. An important challenge for the future is to determine how more subtle derangements of ion channel function, which arise from the interaction of genetic and environmental influences, contribute to common paroxysmal disorders, including idiopathic epilepsy and migraine, that share features with rare monogenic channelopathies.

The dynamic regulation of cortical excitability is altered in episodic ataxia type 2

Episodic ataxia type 2 and familial hemiplegic migraine are two rare hereditary disorders that are linked to dysfunctional ion channels and are characterized clinically by paroxysmal neurological symptoms. Impaired regulation of cerebral excitability is thought to play a role in the occurrence of these paroxysms, but the underlying mechanisms are poorly understood. Normal ion channels are crucial for coordinating neuronal firing in response to facilitatory input. Thus, we hypothesized that channel dysfunction in episodic ataxia type 2 and familial hemiplegic migraine may impair the ability to adjust cerebral excitability after facilitatory events. We tested this hypothesis in patients with episodic ataxia type 2 (n = 6), patients with familial hemiplegic migraine (n = 7) and healthy controls (n = 13). All subjects received a high-frequency burst (10 pulses at 20 Hz) of transcranial magnetic stimulation to transiently increase the excitability of the motor cortex. Acute burst-induced excitability changes were probed at 50, 250, 500 and 1000 ms after the end of the burst. This was done using single-pulse transcranial magnetic stimulation to assess corticospinal excitability, and paired-pulse transcranial magnetic stimulation at an interstimulus interval of 2 and 10 ms to assess intracortical inhibition and facilitation, respectively. The time course of burst-induced excitability changes differed between groups. Healthy controls showed a short-lived increase in excitability that was only present 50 ms after the burst. In contrast, patients with episodic ataxia type 2 showed an abnormally prolonged increase in corticospinal excitability that was still present 250 ms after the transcranial magnetic stimulation burst. Furthermore, while controls showed a decrease in intracortical facilitation during the 1 s period following the transcranial magnetic stimulation burst, patients with episodic ataxia type 2 had increased intracortical facilitation 1000 ms after the burst. Intracortical inhibition was unaltered between groups. Patients with familial hemiplegic migraine were not significantly different from either controls or patients with episodic ataxia type 2. Together, these findings indicate that patients with episodic ataxia type 2 have an excessive increase in motor cortex excitability following a strong facilitatory input. We argue that this deficient control of cortical excitability may set the stage for the emergence of paroxysmal neural dysfunction in this disorder.

Migraine and psychiatric comorbidity: a review of clinical findings

Migraine is an extremely common disorder. The underlying mechanisms of this chronic illness interspersed with acute symptoms appear to be increasingly complex. An important aspect of migraine heterogeneity is comorbidity with other neurological diseases, cardiovascular disorders, and psychiatric illnesses. Depressive disorders are among the leading causes of disability worldwide according to WHO estimation. In this review, we have mainly considered the findings from general population studies and studies on clinical samples, in adults and children, focusing on the association between migraine and psychiatric disorders (axis I of the DSM), carried over after the first classification of IHS (1988). Though not easily comparable due to differences in methodology to reach diagnosis, general population studies generally indicate an increased risk of affective and anxiety disorders in patients with migraine, compared to non-migrainous subjects. There would also be a trend towards an association of migraine with bipolar disorder, but not with substance abuse/dependence. With respect to migraine subtypes, comorbidity mainly involves migraine with aura. Patients suffering from migraine, however, show a decreased risk of developing affective and anxiety disorders compared to patients with daily chronic headache. It would also appear that psychiatric disorders prevail in patients with chronic headache and substance use than in patients with simple migraine. The mechanisms underlying migraine psychiatric comorbidity are presently poorly understood, but this topic remains a priority for future research. Psychiatric comorbidity indeed affects migraine evolution, may lead to chronic substance use, and may change treatment strategies, eventually modifying the outcome of this important disorder.

Adult attention deficit hyperactivity disorder is associated with migraine headaches

Attention deficit hyperactivity disorder (ADHD) is now recognized as a common disorder both in child and adult psychiatry. Adult patients with a diagnosis of ADHD (n = 572) and community controls (n = 675) responded to auto-questionnaires rating past and present symptoms of ADHD, co-morbid conditions, including migraine, treatment history and work status. The prevalence of migraine was significantly higher in the patient group compared to the controls (28.3% vs. 19.2%, P < 0.001, OR = 1.67, CI 1.28-2.17). The difference from controls was particularly marked for men (22.5% vs. 10.7%, P < 0.001, OR = 2.43, CI 1.51-3.90) but was also significant for women (34.4% vs. 24.9%, P = 0.008, OR = 1.58, CI 1.13-2.21). In both patients and controls, migraine was associated with symptoms of mood and anxiety disorders. These findings point to a co-morbidity of migraine with ADHD, and it is possible that these patients represent a clinical and biological subgroup of adult patients with ADHD.

Preparation and evaluation of tubular micelles of pluronic lecithin organogel for transdermal delivery of sumatriptan

The present work focuses on the preparation and evaluation of lecithin organogel system of thermoreversible polymer pluronic F127, which would enhance the stability and absorption of sumatriptan succinate across the skin. Formulations were developed with and without co-surfactant (pluronic F127). The prepared organogels were evaluated for its appearance, organoleptic characteristics, and feel upon application, homogeneity, occlusivenes, washability, pH, viscosity, spreadability, gel transition temperature of formulations. The formulations were also evaluated for drug content, in vitro drug diffusion properties and skin irritation testing. In vivo evaluation of formulations was carried out by hot plate and writhing test method, and finally the optimized formulation was subjected to stability studies. The developed formulations were easily washable, smooth in feel, and showed no clogging which indicate superior texture of system. Formulation, containing pluronic showed greater spreadability and higher drug diffusion rate as compared to pluronic free organogel. Drug content of organogel formulations was in the range of 94-97%. The pH of the formulations was 6.48 ± 0.5 and 6.98 ± 0.1, reflecting no risk of skin irritation. Pluronic not only enhances the stability of organogel by increasing the viscosity (from 6,541 ± 234.76 to 7,826 ± 155.65 poise) but also increases the release of drug from 67.39 ± 1.53% to 74.21 ± 1.7%. The sumatriptan exhibits higher and long lasting antinociceptive effect as indicated by the persistent increase in reaction time in hot plate and inhibited abdominal contraction in acetic acid-induced writhing test (p < 0.05). The prepared optimized formulation was found to be stable without any significant changes at room temperature.

Pain as a channelopathy

Mendelian heritable pain disorders have provided insights into human pain mechanisms and suggested new analgesic drug targets. Interestingly, many of the heritable monogenic pain disorders have been mapped to mutations in genes encoding ion channels. Studies in transgenic mice have also implicated many ion channels in damage sensing and pain modulation. It seems likely that aberrant peripheral or central ion channel activity underlies or initiates many pathological pain conditions. Understanding the mechanistic basis of ion channel malfunction in terms of trafficking, localization, biophysics, and consequences for neurotransmission is a potential route to new pain therapies.

Benign paroxysmal vertigo of childhood: Long-term outcome

Introduction

Benign paroxysmal vertigo (BPV) is characterized by recurrent attacks of dizziness in a healthy child. Complete recovery typically takes place during childhood, and an epidemiological link with migraine has been pointed out. Nevertheless, data concerning long-term patient outcome are scarce.

Subjects and methods

We analyzed the clinical data of 17 patients diagnosed with BPV between 1991 and 2008 in our neuropediatric department; we particularly focused on family medical history and long-term patient outcome by reviewing their medical files and by interviewing the families with a standardized questionnaire administered by phone.

Results

Thirteen families responded to the questionnaire, performed 1.1 to 24.5 years after onset. Among 10 patients older than 11 years of age, five continue to suffer attacks of vertigo. Median age at recovery was six years. Nine subjects exhibited migraine, including all six aged 15 years or older. There was a first-degree history of migraine in eight out of 13 children.

Conclusion

BPV may not be a homogeneous condition, as some children have a poorer prognosis than others. The strong link with migraine, already noticed by previous authors, led us to discuss the pathophysiology of this condition.

STin2 VNTR polymorphism in the serotonin transporter gene and migraine: pooled and meta-analyses

Data on the association between the SLC6A4 STin2 VNTR polymorphism and migraine are conflicting. To perform pooled and meta-analyses, we searched for studies published until September 2009 using electronic databases (MEDLINE, EMBASE, Science Citation Index) and reference lists of studies. Assessment for eligibility and extraction of data was performed by two independent investigators. We extracted allele and genotype frequencies for each study. We then calculated study-specific and pooled odds ratios (OR) and 95% confidence intervals (CI) assuming allele and genotype models. We also calculated pooled ORs and 95% CIs based on study-specific effect estimates for the allele model. We included five studies investigating the association between the STin2 VNTR polymorphism and migraine. Results from the allele model suggested a protective effect against migraine for the STin2.9 and STin2.10 alleles compared to the STin2.12 allele among populations of European descent, which however was not significant. Results from the genotype model indicated a significant ~25% reduced risk for migraine among carriers of the 10/12 genotype compared with carriers of the 12/12 genotype among all study populations (OR = 0.76, 95% CI 0.60–0.97) for any migraine, which was more pronounced among populations of European descent (OR = 0.68, 95% CI 0.53–0.87). Results for migraine with and without aura were of similar magnitude, but were not statistically significant. Our results suggest a protective effect of non-STin2.12 alleles compared to STin2.12 alleles, respectively, 10/12 and 10/10 genotypes compared to the 12/12 genotype against migraine among populations of European descent. Associations in non-European populations may differ.

A visual migraine aura locus maps to 9q21-q22

OBJECTIVE

To identify susceptibility loci for visual migraine aura in migraine families primarily affected with scintillating scotoma type of aura.

METHODS

We included Finnish migraine families with at least 2 affected family members with scintillating scotoma as defined by the International Criteria for Headache Disorders-II. A total of 36 multigenerational families containing 351 individuals were included, 185 of whom have visual aura and 159 have scintillating scotoma. Parametric and nonparametric linkage analyses were performed with 378 microsatellite markers. The most promising linkage loci found were fine-mapped with additional microsatellite markers.

RESULTS

A novel locus on chromosome 9q22-q31 for migraine aura was identified (HLOD = 4.7 at 104 cM). Fine-mapping identified a shared haplotype segment of 12 cM (9.8 Mb) on 9q21-q22 among the aura affected. Four other loci showed linkage to aura: a locus on 12p13 showed significant evidence of linkage, and suggestive evidence of linkage was detected to loci on chromosomes 5q13, 6q25, and 13q14.

CONCLUSIONS

A novel visual migraine aura locus has been mapped to chromosome 9q21-q22. Interestingly, this region has previously been linked to occipitotemporal lobe epilepsy with prominent visual symptoms. Our finding further supports a shared genetic background in migraine and epilepsy and suggests that susceptibility variant(s) to visual aura for both of these traits are located in the 9q21-q22 locus.

A genome-wide linkage study of bipolar disorder and co-morbid migraine: replication of migraine linkage on chromosome 4q24, and suggestion of an overlapping susceptibility region for both disorders on chromosome 20p11

Migraine and Bipolar Disorder (BPAD) are clinically heterogeneous disorders of the brain with a significant, but complex, genetic component. Epidemiological and clinical studies have demonstrated a high degree of co-morbidity between migraine and BPAD. Several genome-wide linkage studies in BPAD and migraine have shown overlapping regions of linkage on chromosomes, and two functionally similar voltage-dependent calcium channels CACNA1A and CACNA1C have been identified in familial hemiplegic migraine and recently implicated in two whole genome BPAD association studies, respectively. We hypothesized that using migraine co-morbidity to look at subsets of BPAD families in a genetic linkage analysis would prove useful in identifying genetic susceptibility regions in both of these disorders. We used BPAD with co-morbid migraine as an alternative phenotype definition in a re-analysis of the NIMH Bipolar Genetics Initiative wave 4 data set. In this analysis we selected only those families in which at least two members were diagnosed with migraine by a doctor according to patients' reports. Nonparametric linkage analysis performed on 31 families segregating both BPAD and migraine identified a linkage signal on chromosome 4q24 for migraine (but not BPAD) with a peak LOD of 2.26. This region has previously been implicated in two independent migraine linkage studies. In addition we identified a locus on chromosome 20p11 with overlapping elevated LOD scores for both migraine (LOD=1.95) and BPAD (LOD=1.67) phenotypes. This region has previously been implicated in two BPAD linkage studies, and, interestingly, it harbors a known potassium dependant sodium/calcium exchanger gene, SLC24A3, that plays a critical role in neuronal calcium homeostasis. Our findings replicate a previously identified migraine linkage locus on chromosome 4 (not co-segregating with BPAD) in a sample of BPAD families with co-morbid migraine, and suggest a susceptibility locus on chromosome 20, harboring a gene for the migraine/BPAD phenotype. Together these data suggest that some genes may predispose to both bipolar disorder and migraine.

5-HTTLPR polymorphism in the serotonin transporter gene and migraine: a systematic review and meta-analysis

BACKGROUND AND METHODS

Data on the association between the SLC6A4 5-HTTLPR polymorphism and migraine are conflicting. We performed a systematic review and meta-analysis among studies published up to September 2009. For each study with genotype information, we calculated odds ratios (OR) and 95% confidence intervals (CI) assuming additive, dominant, and recessive genetic models. We then calculated pooled ORs and 95% CIs.

RESULTS

Among the ten studies identified there was no overall association between the polymorphism and any migraine for Europeans or Asians. However, European women carrying the S allele had an increased risk for any migraine (dominant model: pooled OR=2.02; 95% CI 1.24-3.28). Results among Europeans further suggested an increased risk for migraine with aura among carriers of the S/S genotype (recessive model: pooled OR=1.41; 95% CI 0.83-2.40).

CONCLUSIONS

While our results indicate no overall association between the SLC6A4 5-HTTLPR polymorphism and migraine among Europeans and Asians, gender and migraine aura status may have modifying roles among Europeans.

Headache-type adverse effects of NO donors: vasodilation and beyond

Although nitrate therapy, used in the treatment of cardiovascular disorders, is frequently associated with side-effects, mainly headaches, the summaries of product characteristics of nitrate-containing medicines do not report detailed description of headaches and even do not highlight the possibility of nitrate-induced migraine. Two different types of nitrate-induced headaches have been described: (i) immediate headaches that develop within the first hour of the application, are mild or medium severity without characteristic symptoms for migraine, and ease spontaneously; and (ii) delayed, moderate or severe migraine-type headaches (occurring mainly in subjects with personal or family history of migraine), that develop 3-6 h after the intake of nitrates, with debilitating, long-lasting symptoms including nausea, vomiting, photo- and/or phono-phobia. These two types of headaches are remarkably different, not only in their timing and symptoms, but also in the persons who are at risk. Recent studies provide evidence that the two headache types are caused by different mechanisms: immediate headaches are connected to vasodilation caused by nitric oxide (NO) release, while migraines are triggered by other actions such as the release of calcitonin gene-related peptide or glutamate, or changes in ion channel function mediated by cyclic guanosine monophosphate or S-nitrosylation. Migraines usually need anti-attack medication, such as triptans, but these drugs are contraindicated in most medical conditions that are treated using nitrates. In conclusion, these data recommend the correction of summaries of nitrate product characteristics, and also suggest a need to develop new types of anti-migraine drugs, effective in migraine attacks, that could be used in patients with risk for angina pectoris.

Association study of the serotoninergic system in migraine in the Spanish population

In order to evaluate the contribution of 19 serotonin-related genes to the susceptibility to migraine in a Spanish population we performed a case-control association study of 122 single nucleotide polymorphisms (SNPs), selected according to genetic coverage parameters, in 528 migraine patients -308 with migraine without aura (MO) and 220 with migraine with aura (MA)- and 528 sex-matched migraine-free controls. The single-marker analysis identified nominal associations with the migraine phenotype or with the MO or MA subtypes. The multiple-marker analysis revealed risk haplotypes in three genes that remained significantly associated with migraine after correction by permutations. Two-marker risk haplotypes were identified in the HTR2B (rs16827801T-rs10194776G) and MAOA (rs3027400G-rs2072743C) genes conferring susceptibility to MO, and a four-marker haplotype in DDC was specific of MA (rs2329340A-rs11974297C-rs2044859T-rs11761683G). The present study supports the involvement of HTR2B and MAOA genes in the genetic predisposition to MO, while DDC might confer susceptibility to MA. These results suggest a differential involvement of serotonin-related genes in the genetic background of MO and MA.

Vestibular migraine

Vestibular migraine is a chameleon among the episodic vertigo syndromes because considerable variation characterizes its clinical manifestation. The attacks may last from seconds to days. About one-third of patients presents with monosymptomatic attacks of vertigo or dizziness without headache or other migrainous symptoms. During attacks most patients show spontaneous or positional nystagmus and in the attack-free interval minor ocular motor and vestibular deficits. Women are significantly more often affected than men. Symptoms may begin at any time in life, with the highest prevalence in young adults and between the ages of 60 and 70. Over the last 10 years vestibular migraine has evolved into a medical entity in dizziness units. It is the most common cause of spontaneous recurrent episodic vertigo and accounts for approximately 10% of patients with vertigo and dizziness. Its broad spectrum poses a diagnostic problem of how to rule out Menière's disease or vestibular paroxysmia. Vestibular migraine should be included in the International Headache Classification of Headache Disorders (ICHD) as a subcategory of migraine. It should, however, be kept separate and distinct from basilar-type migraine and benign paroxysmal vertigo of childhood. We prefer the term "vestibular migraine" to "migrainous vertigo," because the latter may also refer to various vestibular and non-vestibular symptoms. Antimigrainous medication to treat the single attack and to prevent recurring attacks appears to be effective, but the published evidence is weak. A randomized, double-blind, placebo-controlled study is required to evaluate medical treatment of this condition.

[What is migraine?]

Migraine is a multifactorial and heterogeneous disorder. Diagnostic criteria have been established by the International Headache Society, however these are only supportive in terms of definition. The pathophysiology involves neuronal and vascular phenomena. The former is supported by the cortical spreading depression being the aura correlate and by brainstem and hypothalamic activation during the pain phase; the latter is suggested by the association between migraine and cardiovascular disease and findings of pathological vasoreactivity and endothelial dysfunction. Triptans and calcitonin gene-related peptide receptor antagonists show only a relative migraine-specific action; up to 30% of patients are nonresponders. Despite a clear genetic component, the discovery of specific genes for common forms of migraine remains elusive. Electrophysiological studies consistently indicate a characteristic "dyshabituation" concurring with clinical features of altered sensory perception. The age- and sex-specific pattern along with the effect of external factors on the course of migraine argue in favor of the involvement of epigenetic mechanisms. Knowledge about migraine is still limited, which hampers a definition.

Two-stage case-control association study of dopamine-related genes and migraine

BACKGROUND

We previously reported risk haplotypes for two genes related with serotonin and dopamine metabolism: MAOA in migraine without aura and DDC in migraine with aura. Herein we investigate the contribution to migraine susceptibility of eight additional genes involved in dopamine neurotransmission.

METHODS

We performed a two-stage case-control association study of 50 tag single nucleotide polymorphisms (SNPs), selected according to genetic coverage parameters. The first analysis consisted of 263 patients and 274 controls and the replication study was composed by 259 cases and 287 controls. All cases were diagnosed according to ICHD-II criteria, were Spanish Caucasian, and were sex-matched with control subjects.

RESULTS

Single-marker analysis of the first population identified nominal associations of five genes with migraine. After applying a false discovery rate correction of 10%, the differences remained significant only for DRD2 (rs2283265) and TH (rs2070762). Multiple-marker analysis identified a five-marker T-C-G-C-G (rs12363125-rs2283265-rs2242592-rs1554929-rs2234689) risk haplotype in DRD2 and a two-marker A-C (rs6356-rs2070762) risk haplotype in TH that remained significant after correction by permutations. These results, however, were not replicated in the second independent cohort.

CONCLUSION

The present study does not support the involvement of the DRD1, DRD2, DRD3, DRD5, DBH, COMT, SLC6A3 and TH genes in the genetic predisposition to migraine in the Spanish population.

New implications of the proteolytic balance between matrix metalloproteinases and their tissue inhibitors in migraine with and without aura

Matrix metalloproteinases (MMP) are proteolytic enzymes involved in the remodelling of almost all protein components of the extracellular matrix (ECM), characterized in 1960's during the metamorphosis process in tadpole tails. Ever growing research has identified MMP expression in a variety of physiological processes. Uncontrolled or inappropriate expression/activity of MMPs contributes to different pathologic conditions, including inflammation, tumour growth, cancer cell invasion and infection diseases. Under physiological conditions, MMP activity is precisely controlled by TIMPs and may have beneficial actions in the mature nervous system. However, an alteration of the MMP/TIMP balance is thought to be a key feature of the pathology of many inflammatory, degenerative and malignant neurological diseases; their pathogenesis is correlated to the detrimental effects of altered MMP/TIMP expression, leading to breakdown of the blood-brain barrier (BBB), demyelination, cytokine production and propagation of inflammatory response, deposition of amyloid proteins, tumor invasion and metastasis). Migraine is a complex, disabling disorder of the brain that manifests itself as attacks of often severe, throbbing head pain with sensory sensitivity to light, sound, smell and head movement (migraine without aura), and in a third of patients, with neurological symptoms (migraine with aura). In this issue of Clinica Chimica Acta, Martins-Oliveira et al. examine the different circulating MMP and TIMP profiles in women with migraine with and without aura. They confirm and expand the observation of increased MMP-9 plasma levels in migrainous patients, also describing for the first time that MMP-2, TIMP-1 and TIMP-2 show a different expression profile in migraine. Their findings are critically evaluated and reviewed. The knowledge of MMP- and TIMP-dependent pathways in migraine headache, the new proteolytic pathophysiological mechanisms, and the beneficial and detrimental effects of MMP inhibitory drugs may represent pieces of the complex migraine jigsaw puzzle, which is finalized to optimize cost-effectiveness of treatment and patient outcomes.

Advances in the basic and clinical science of migraine

Migraine continues to be an elephant in the room of medicine: massively common and a heavy burden on patients and their healthcare providers, yet the recipient of relatively little attention for research, education, and clinical resources. Its visibility is gradually increasing, however, as advances in genetics, imaging, epidemiology, and pharmacology produce a more definitive understanding of the condition, and identify more specific and effective treatments. Rapid evolution of concepts regarding its prevalence, pathophysiology, and clinical management is leading to growing recognition of migraine as a fundamentally important disorder of the nervous system.

Variations in the cannabinoid receptor 1 gene predispose to migraine

In animal models endogenous cannabinoids have an inhibitory effect on trigeminovascular activation through the cannabinoid receptor 1 (CB1), although there is no evidence of the potential role of CB1 in human migraine. In this study we applied single marker association and haplotypic trend regression analysis to investigate the relationship between the CB1 gene (CNR1) and headache with migraine symptoms (nausea, photophobia and disability, measured by the ID-migraine questionnaire). We identified our controls (CO=684) as those who have not reported ID-migraine symptoms at all and defined migraine headache sufferers (M=195) as those who reported all three symptoms. The CNR1 was covered by 10 SNPs located throughout the gene based on haplotype tagging (htSNP) and previous literature. Our results demonstrated a significant haplotypic effect of CNR1 on migraine headaches (p=0.008, after permutation p=0.017). This effect was independent of reported depression or drug/alcohol abuse although using neuroticism in the analysis as covariant slightly decreased this association (p=0.027, permutated p=0.052). These results suggest a significant effect of CNR1 on migraine headaches that might be related to the alteration of peripheral trigeminovascular activation. In addition, this is the first study to demonstrate the effectiveness of using trait components combinations to define extreme phenotypes with haplotype analysis in genetic association studies for migraine. However, further studies are needed to elucidate the role of CNR1 and the cannabinoid system in migraine.

Classification and clinical features of headache disorders in Pakistan: a retrospective review of clinical data

Background

Morbidity associated with primary headache disorders is a major public health problem with an overall prevalence of 46%. Tension-type headache and migraine are the two most prevalent causes. However, headache has not been sufficiently studied as a cause of morbidity in the developing world. Literature on prevalence and classification of these disorders in South Asia is scarce. The aim of this study is to describe the classification and clinical features of headache patients who seek medical advice in Pakistan.

Methods and Results

Medical records of 255 consecutive patients who presented to a headache clinic at a tertiary care hospital were reviewed. Demographic details, onset and lifetime duration of illness, pattern of headache, associated features and family history were recorded. International Classification of Headache Disorders version 2 was applied.

66% of all patients were women and 81% of them were between 16 and 49 years of age. Migraine was the most common disorder (206 patients) followed by tension-type headache (58 patients), medication-overuse headache (6 patients) and cluster headache (4 patients). Chronic daily headache was seen in 99 patients. Patients with tension-type headache suffered from more frequent episodes of headache than patients with migraine (p<0.001). Duration of each headache episode was higher in women with menstrually related migraine (p = 0.015). Median age at presentation and at onset was lower in patients with migraine who reported a first-degree family history of the disease (p = 0.003 and p<0.001 respectively).

Conclusions/Significance

Patients who seek medical advice for headache in Pakistan are usually in their most productive ages. Migraine and tension-type headache are the most common clinical presentations of headache. Onset of migraine is earlier in patients with first-degree family history. Menstrually related migraine affects women with headache episodes of longer duration than other patients and it warrants special therapeutic consideration. Follow-up studies to describe epidemiology and burden of headache in Pakistan are needed.

Psychiatric disorders and headache familial recurrence: a study on 200 children and their parents

The main aim of the study was to examine the relationship between headache and familial recurrence of psychiatric disorders in parents and their children. Headache history and symptomatology have been collected in a clinical sample of 200 patients and their families, using a semi-structured interview (ICHD-II criteria). Psychiatric comorbidity was assessed by DSM-IV criteria. Chi squares and a loglinear analysis were computed in order to evaluate the main effects and interactions between the following factors: frequency and headache subtypes (migraine/not-migraine) in children, headache (migraine/not-migraine-absent/present) in parents, headache (absent/present) in grandparents, and psychiatric comorbidity (absent/present) have been analyzed: 94 mothers (47%) and 51 fathers (25.5%) had at least one psychiatric disorder, mainly mood and anxiety disorders. Considering the significant prevalence of Psi-co in children (P < 0.0001), we compared it with the presence of familiarity to headache: a significant interaction has been found (P < 0.05) showing that migraineurs with high familial recurrence of headache had a higher percentage (74.65%) of psychiatric disorders, than no-migraineurs (52.17%). Absence of headache familial loading seems to be related to psi-co only in no-migraine headache (87.5 vs. 45.5%). The occurrence of psychiatric disorders is high in children with headache, but a very different pattern seems to characterize migraine (familial co-transmission of migraine and Psi-Co?) if compared with non-migraine headache.

First mutation in the voltage-gated Nav1.1 subunit gene SCN1A with co-occurring familial hemiplegic migraine and epilepsy

Almost all mutations in the SCN1A gene, encoding the alpha(1) subunit of neuronal voltage-gated Na(V)1.1 sodium channels, are associated with severe childhood epilepsy. Recently, two mutations were identified in patients with pure familial hemiplegic migraine (FHM). Here, we identified a novel SCN1A L263V mutation in a Portuguese family with partly co-segregating hemiplegic migraine and epilepsy. The L263V mutation segregated in five FHM patients, three of whom also had epileptic attacks, occurring independently from their hemiplegic migraine attacks. L263V is the first SCN1A mutation associated with FHM and co-occurring epilepsy in multiple mutation carriers, and is the clearest molecular link between migraine and epilepsy thus far. The results extend the clinical spectrum associated with SCN1A mutations and further strengthen the molecular evidence that FHM and epilepsy share, at least in part, similar molecular pathways.

Common genetic influences underlie comorbidity of migraine and endometriosis

We examined the co-occurrence of migraine and endometriosis within the largest known collection of families containing multiple women with surgically confirmed endometriosis and in an independent sample of 815 monozygotic and 457 dizygotic female twin pairs. Within the endometriosis families, a significantly increased risk of migrainous headache was observed in women with endometriosis compared to women without endometriosis (odds ratio [OR] 1.57, 95% confidence interval [CI]: 1.12-2.21, P=0.009). Bivariate heritability analyses indicated no evidence for common environmental factors influencing either migraine or endometriosis but significant genetic components for both traits, with heritability estimates of 69 and 49%, respectively. Importantly, a significant additive genetic correlation (r(G) = 0.27, 95% CI: 0.06-0.47) and bivariate heritability (h(2)=0.17, 95% CI: 0.08-0.27) was observed between migraine and endometriosis. Controlling for the personality trait neuroticism made little impact on this association. These results confirm the previously reported comorbidity between migraine and endometriosis and indicate common genetic influences completely explain their co-occurrence within individuals. Given pharmacological treatments for endometriosis typically target hormonal pathways and a number of findings provide support for a relationship between hormonal variations and migraine, hormone-related genes and pathways are highly plausible candidates for both migraine and endometriosis. Therefore, taking into account the status of both migraine and endometriosis may provide a novel opportunity to identify the genes underlying them. Finally, we propose that the analysis of such genetically correlated comorbid traits can increase power to detect genetic risk loci through the use of more specific, homogenous and heritable phenotypes.

Genetic contributions to pain: a review of findings in humans

Pain represents the major motivating factor for which individuals seek healthcare, and pain responses are characterized by substantial inter-individual differences. Increasing evidence suggests that genetic factors contribute significantly to individual differences in responses to both clinical and experimental pain. The purpose of this review article was to summarize the current literature regarding genetic contributions to pain, highlighting findings relevant to oral pain where available. A brief discussion of methodologic considerations is followed by a review of findings regarding genetic influences on clinical pain. Next, the literature examining genetic contributions to experimental pain responses is presented, emphasizing genetic associations that have been replicated in multiple cohorts. It is hoped that an enhanced understanding of genetic contributions to pain responses will ultimately improve diagnosis and treatment of clinical pain conditions.

Migraine: where and how does the pain originate?

Migraine is a complex neurological disease with a genetic background. Headache is the most prominent and clinically important symptom of migraine but its origin is still enigmatic. Numerous clinical, histochemical, electrophysiological, molecular and genetical approaches form a puzzle of findings that slowly takes shape. The generation of primary headaches like migraine pain seems to be the consequence of multiple pathophysiological changes in meningeal tissues, the trigeminal ganglion, trigeminal brainstem nuclei and descending inhibitory systems, based on specific characteristics of the trigeminovascular system. This contribution reviews the current discussion of where and how the migraine pain may originate and outlines the experimental work to answer these questions.