Familial occipitotemporal lobe epilepsy and migraine with visual aura: Linkage to chromosome 9q

Cortical mechanisms in migraine

Migraine is the second most prevalent disorder in the world; yet, its underlying mechanisms are still poorly understood. Cumulative studies have revealed pivotal roles of cerebral cortex in the initiation, propagation, and termination of migraine attacks as well as the interictal phase. Investigation of basic mechanisms of the cortex in migraine not only brings insight into the underlying pathophysiology but also provides the basis for designing novel treatments. We aim to summarize the current research literatures and give a brief overview of the cortex and its role in migraine, including the basic structure and function; structural, functional, and biochemical neuroimaging; migraine-related genes; and theories related to cortex in migraine pathophysiology. We propose that long-term plasticity of synaptic transmission in the cortex encodes migraine.

Genetic Interaction of H19 and TGFBR1 Polymorphisms with Risk of Epilepsy in a Chinese Population

PURPOSE

Long non-coding RNA H19 was highly expressed in the latent period of epilepsy, contributing to apoptosis of hippocampal neurons by targeting let-7b. Transforming growth factor beta receptor 1 (TGFBR1), a target of let-7b, is located on the susceptibility locus for epilepsy. In this context, we investigated the association between tagSNPs in long non-coding RNA H19 and transforming growth factor beta receptor 1 (TGFBR1) rs6478974 and the risk of epilepsy.

PATIENTS AND METHODS

The present study consisted of 302 patients with epilepsy and 612 age- and gender-matched controls. The polymorphisms were analyzed using a TaqMan allelic genotyping assay. H19 and TGFBR1 mRNA levels were determined using quantitative real-time polymerase chain reaction.

RESULTS

The TGFBR1 AT and TT genotypes emerged as a protective factor for the risk of epilepsy (AT vs AA: adjusted OR = 0.59, 95% CI: 0.39-0.89, P = 0.01; TT vs AA: adjusted OR = 0.53, 95% CI: 0.35-0.80, P = 0.002, respectively). The protective effect was also observed in recessive genetic model (adjusted OR = 0.56, 95% CI: 0.38-0.82, P = 0.003). Individuals carrying the rs6478974 TT genotype had lower levels of TGFBR1 mRNA. Moreover, the TCTAT and TCCAA haplotypes emerged as a risk factor for epilepsy and the rs3741219-rs2839698-rs6478974 was associated with an interactive effect on the risk of epilepsy.

CONCLUSION

The current study provides evidence of the rs6478974 TT genotype decreasing the susceptibility to epilepsy by reducing the levels of TGFBR1 mRNA.

A familial t(4;8) translocation segregates with epilepsy and migraine with aura

Three relatives carrying a t(4;8)(p15.2;p23.2) translocation had juvenile myoclonic epilepsy, self‐limited photosensitive occipital epilepsy and migraine with aura. The t(4;8) translocation interrupted the coding sequence of CSMD1 gene and occurred immediately to the 3’UTR of STIM2 gene. STIM2 was overexpressed in the patient carrying the unbalanced translocation, and all three individuals had a single functional copy of CSMD1. Array CGH study disclosed that these three individuals also carried a deletion at 5q12.3 that involves the RGS7BP gene. The overall results favor the view that CSMD1, STIM2, and RGS7BP genes could contribute to epilepsy and migraine phenotypes in our family.

Genetic Analysis of a Large Family with Migraine, Vertigo, and Motion Sickness

BACKGROUND

Migraine is a common disorder most typically presenting as headache and often associated with vertigo and motion sickness. It is a genetically complex condition with multiple genes ultimately contributing to the predisposition and development of this episodic neurological disorder. We identified a large American family of 29 individuals of which 17 members suffered from at least one of these disorders, migraine, vertigo, or motion sickness. Many of these individuals suffered from several simultaneously. We hypothesized that vertigo and motion sickness may involve genes that are independent to those directly contributing to migraine susceptibility.

METHODS

Genome-wide linkage analysis performed using 400 microsatellite repeat markers spaced at 10 cM throughout the genome. The members of this family were phenotyped for each condition, migraine, vertigo, and motion sickness and analyzed separately. Statistical analysis was performed using two-point and multipoint linkage analysis employing a number of models including autosomal recessive or dominant patterns of inheritance with high and low genetic penetrance.

RESULTS

We identified a novel locus for migraine, 9q13-q22 (maximum two-point logarithm of odds [LOD] score-2.51). In addition, there are suggestive LOD scores that localize to different chromosomes for each phenotype; vertigo (chromosome 18, LOD score of 1.82) and motion sickness (chromosome 4, LOD score of 2.09).

CONCLUSIONS

Our analysis supports our hypothesis that the migraine-associated vertigo and motion sickness may involve distinct susceptibility genes.

Pediatric Headache and Seizures

Headache and seizures are two of the most common complaints seen in the field of pediatric neurology with headache being number one. Both these conditions may coexist. Where the difficulty begins is when the symptoms are not clear cut in making a diagnosis, and conditions are possible as either an atypical seizure or migraine variant. What further complicates matters is the fact that there are many underlying neurologic conditions that carry with them a higher likelihood of developing both headaches and seizures, making each a distinct possibility when obtaining a history from a parent about unusual spells. Although differentiating between seizure and headache may not be easy, with a focused yet thorough history and appropriate use of investigative tools, it can be done. Coming to the correct diagnosis is only the start; once seizures and or headaches have been appropriately diagnosed then the real challenge begins and that is finding a way to successfully treat the headaches and seizures. Within pediatric neurology, the acute options tend to be more diagnosis specific whereas the prophylactic ones may overlap and treat both headaches and seizures. In the following review, we will discuss the epidemiology of pediatric headaches and seizures, the overlap between these 2 conditions in diagnosis, as well as how to tell them apart, and the treatment options and prognosis of both common neurologic disorders in children.

Phenotypic analysis of 303 multiplex families with common epilepsies

Gene identification in epilepsy has mainly been limited to large families segregating genes of major effect and de novo mutations in epileptic encephalopathies. Many families that present with common non-acquired focal epilepsies and genetic generalized epilepsies remain unexplained. We assembled a cohort of 'genetically enriched' common epilepsies by collecting and phenotyping families containing multiple individuals with unprovoked seizures. We aimed to determine if specific clinical epilepsy features aggregate within families, and whether this segregation of phenotypes may constitute distinct 'familial syndromes' that could inform genomic analyses. Families with three or more individuals with unprovoked seizures were studied across multiple international centres. Affected individuals were phenotyped and classified according to specific electroclinical syndromes. Families were categorized based on syndromic groupings of affected family members, examined for pedigree structure and phenotypic patterns and, where possible, assigned specific familial epilepsy syndromes. A total of 303 families were assembled and analysed, comprising 1120 affected phenotyped individuals. Of the 303 families, 117 exclusively segregated generalized epilepsy, 62 focal epilepsy, and 22 were classified as genetic epilepsy with febrile seizures plus. Over one-third (102 families) were observed to have mixed epilepsy phenotypes: 78 had both generalized and focal epilepsy features within the same individual (n = 39), or within first or second degree relatives (n = 39). Among the genetic generalized epilepsy families, absence epilepsies were found to cluster within families independently of juvenile myoclonic epilepsy, and significantly more females were affected than males. Of the 62 familial focal epilepsy families, two previously undescribed familial focal syndrome patterns were evident: 15 families had posterior quadrant epilepsies, including seven with occipito-temporal localization and seven with temporo-parietal foci, and four families displayed familial focal epilepsy of childhood with multiple affected siblings that was suggestive of recessive inheritance. The findings suggest (i) specific patterns of syndromic familial aggregation occur, including newly recognized forms of familial focal epilepsy; (ii) although syndrome-specificity usually occurs in multiplex families, the one-third of families with features of both focal and generalized epilepsy is suggestive of shared genetic determinants; and (iii) patterns of features observed across families including pedigree structure, sex, and age of onset may hold clues for future gene identification. Such detailed phenotypic information will be invaluable in the conditioning and interpretation of forthcoming sequencing data to understand the genetic architecture and inter-relationships of the common epilepsy syndromes.

Population-based approaches to genetics of migraine

BACKGROUND

While the most accurate diagnosis of migraine typically requires a clinical interview guided by strict diagnostic criteria, an alternative approach that ascertains migraine by questionnaire in population-based settings has been instrumental in the discovery of common genetic variants influencing migraine risk. This result may be surprising. Population-based approaches are often criticized for limited ability to distinguish migraine from other forms of primary headache. It is thus useful to revisit prevailing ideas about population-based ascertainment of migraine to evaluate the extent to which this approach has potential for additional insights into migraine genetics and therefore pathophysiology.

OVERVIEW

We review recent findings suggesting that the success of the population-based approach is derived from the possibility of collecting much larger samples than in the clinic-based setting even at the risk of introducing phenotypic and genetic heterogeneity. The findings are also consistent with new appreciations for the genetic basis of many other common, complex clinical characteristics. However, clinic-based ascertainment and other settings will remain more effective than population-based approaches for investigating certain, often very specific aspects of migraine genetics.

CONCLUSION

We argue that the detailed genetic architecture of migraine, various aspects of methodology, and the ultimate sample size achieved by population-based ascertainment will be critical determinants of the future success of this approach to genetic analysis of migraine and its comorbidities.

Medical Comorbidities in Pediatric Headache

Comorbid conditions frequently occur in pediatric headaches and may significantly affect their management. Comorbidities that have been associated with pediatric headaches include attention-deficit or hyperactivity disorder, autism, developmental disabilities, depression, anxiety, epilepsy, obesity, infantile colic, atopic disorders, inflammatory bowel disease, and irritable bowel syndrome. The goal of this article is to review these comorbidities associated with pediatric headache, thereby empowering child neurologists to identify common triggers and tailor management strategies that address headache and its comorbidities.

On the midway to epilepsy: is cortical excitability normal in patients with isolated seizures?

Paired pulse transcranial magnetic stimulation was used to investigate differences in cortical excitability between patients with isolated (unrecurrent, unprovoked) seizures and those with epilepsy. Compared to controls, cortical excitability was higher in the isolated seizure group at 250-300 ms. Compared to epilepsy, cortical excitability was lower in patients with isolated seizures also at 250 and 300 ms. Lowered seizure threshold caused by disturbances within inhibitory circuits is present in patients who experience a seizure even if no further seizures occur.

Comorbidity of Migraine

Migraine is a common neurological disorder and can be severely disabling during attacks. The highest prevalence occurs between the ages of 25 and 55 years. Prior studies have found that migraine occurs together with other illnesses at a greater coincidental rate than is seen in the general population. These occurrences are called "comorbidities". To delineate the comorbidities of migraine is important, because it can help improve treatment strategies and the understanding of the possible pathophysiology of migraine.

Application of density estimation algorithms in analyzing co-morbidities of migraine

In this study, we will propose a density estimation based data analysis procedure to investigate the co-morbid associations between migraine and the suspected diseases. The primary objective of this study has aimed to develop a novel analysis procedure that can discover insightful knowledge from large medical databases. The entire analysis procedure consists of two stages. During the first stage, a kernel density estimation algorithm named relaxed variable kernel density estimation (RVKDE) is invoked to identify the samples of interest. Then, in the second stage, a density estimation algorithm based on generalized Gaussian components and named G²DE is invoked to provide a summarized description of the distribution. The results obtained by applying the proposed two-staged procedure to analyze co-morbidities of migraine revealed that the proposed procedure could effectively identify a number of clusters of samples with distinctive characteristics. The results further revealed that the distinctive characteristics of the clusters extracted by the proposed procedure were in conformity with the observations reported in recently published articles. Accordingly, it is conceivable that the proposed analysis procedure can be exploited to provide valuable clues of pathogenesis and facilitate development of proper treatment strategies.

Evidence for a shared genetic susceptibility to migraine and epilepsy

PURPOSE

Although epilepsy and migraine are known to co-occur within individuals, the contribution of a shared genetic susceptibility to this comorbidity remains unclear. We investigated the hypothesis of shared genetic effects on migraine and epilepsy in the Epilepsy Phenome/Genome Project (EPGP) cohort.

METHODS

We studied prevalence of a history of migraine in 730 EPGP participants aged ≥ 12 years with nonacquired focal epilepsy (NAFE) or generalized epilepsy (GE) from 501 families containing two or more individuals with epilepsy of unknown cause. Information on migraine without aura (MO) and migraine with aura (MA) was collected using an instrument validated for individuals ≥ 12 years. Because many individuals have both MO and MA, we considered two nonoverlapping groups of individuals with migraine: those who met criteria for MA in any of their headaches (MA), and those who did not ("MO-only"). EPGP participants were interviewed about the history of seizure disorders in additional nonenrolled family members. We evaluated associations of migraine prevalence in enrolled subjects with a family history of seizure disorders in additional nonenrolled relatives, using generalized estimating equations to control for the nonindependence of observations within families.

KEY FINDINGS

Prevalence of a history of MA (but not MO-only) was significantly increased in enrolled participants with two or more additional affected first-degree relatives.

SIGNIFICANCE

These findings support the hypothesis of a shared genetic susceptibility to epilepsy and MA.

Genetics of epilepsy and relevance to current practice

Genetic factors are likely to play a major role in many epileptic conditions, spanning from classical idiopathic (genetic) generalized epilepsies to epileptic encephalopathies and focal epilepsies. In this review we describe the genetic advances in progressive myoclonus epilepsies, which are strictly monogenic disorders, genetic generalized epilepsies, mostly exhibiting complex genetic inheritance, and SCN1A-related phenotypes, namely genetic generalized epilepsy with febrile seizure plus and Dravet syndrome. Particular attention is devoted to a form of familial focal epilepsies, autosomal-dominant lateral temporal epilepsy, which is a model of non-ion genetic epilepsies. This condition is associated with mutations of the LGI1 gene, whose protein is secreted from the neurons and exerts its action on a number of targets, influencing cortical development and neuronal maturation.

Guanosine triphosphate cyclohydrolase 1 promoter deletion causes dopa-responsive dystonia

BACKGROUND

Autosomal dominant dopa-responsive dystonia (AD-DRD) is caused by a biochemical defect primarily resulting from guanosine triphosphate cyclohydrolase 1 gene (GCH1) mutations. Few families have been reported without mutations in GCH1.

METHODS

Genome-wide linkage analysis and positional cloning to identify the genetic defect in a Belgian AD-DRD family was carried out.

RESULTS AND CONCLUSION

In this study, we report on the identification and characterization of a novel 24-kb deletion spanning exon 1 and the 5' regulatory region of GCH1 causing a wide spectrum of motor and nonmotor symptoms in a large Belgian AD-DRD family. This large-scale deletion of regulatory sequences leads to decreased GCH1 activity in all carriers, most probably resulting from allelic loss of transcription. We mapped the breakpoints of this deletion to the nucleotide level, allowing the development of a straightforward polymerase chain reaction assay for fast, efficient detection of this large deletion, which will prove valuable for preimplantation genetic diagnosis.

Genetics of migraine: an update

An important genetic component of migraine was systematically established by epidemiological studies in the 1990s. Over the past 15 years, significant progress has been made in unraveling the genetic basis and pathophysiological mechanisms of familial hemiplegic migraine, a rare and severe autosomal-dominant subtype of migraine with aura. Three different causative genes (CACNA1A, ATP1A2 and SCN1A), all of which are involved in cerebral ion translocation, have been identified. Functional studies and mouse models have shown that mutations in these genes, by different mechanisms, cause a disturbed cerebral glutamate homeostasis and, thus, increase susceptibility to cortical spreading depression, the likely correlate of migraine aura. More recently, genome-wide association studies have, for the first time, detected robust risk variants associated with the more common, genetically complex types of migraine, which has generated new perspectives for genetic research in migraine. This review summarizes the current knowledge about migraine genetics, with a focus on both familial hemiplegic migraine and recent results of genome-wide association studies.

A genome-wide analysis of 'Bounty' descendants implicates several novel variants in migraine susceptibility

Migraine is a common neurological disease with a complex genetic aetiology. The disease affects ~12% of the Caucasian population and females are three times more likely than males to be diagnosed. In an effort to identify loci involved in migraine susceptibility, we performed a pedigree-based genome-wide association study of the isolated population of Norfolk Island, which has a high prevalence of migraine. This unique population originates from a small number of British and Polynesian founders who are descendents of the Bounty mutiny and forms a very large multigenerational pedigree (Bellis et al.; Human Genetics, 124(5):543-5542, 2008). These population genetic features may facilitate disease gene mapping strategies (Peltonen et al.; Nat Rev Genet, 1(3):182-90, 2000. In this study, we identified a high heritability of migraine in the Norfolk Island population (h (2) = 0.53, P = 0.016). We performed a pedigree-based GWAS and utilised a statistical and pathological prioritisation approach to implicate a number of variants in migraine. An SNP located in the zinc finger protein 555 (ZNF555) gene (rs4807347) showed evidence of statistical association in our Norfolk Island pedigree (P = 9.6 × 10(-6)) as well as replication in a large independent and unrelated cohort with >500 migraineurs. In addition, we utilised a biological prioritisation to implicate four SNPs, in within the ADARB2 gene, two SNPs within the GRM7 gene and a single SNP in close proximity to a HTR7 gene. Association of SNPs within these neurotransmitter-related genes suggests a disrupted serotoninergic system that is perhaps specific to the Norfolk Island pedigree, but that might provide clues to understanding migraine more generally.

Heritability and genome-wide linkage analysis of migraine in the genetic isolate of Norfolk Island

Migraine is a common neurovascular disorder with a complex envirogenomic aetiology. In an effort to identify migraine susceptibility genes, we conducted a study of the isolated population of Norfolk Island, Australia. A large portion of the permanent inhabitants of Norfolk Island are descended from 18th Century English sailors involved in the infamous mutiny on the Bounty and their Polynesian consorts. In total, 600 subjects were recruited including a large pedigree of 377 individuals with lineage to the founders. All individuals were phenotyped for migraine using International Classification of Headache Disorders-II criterion. All subjects were genotyped for a genome-wide panel of microsatellite markers. Genotype and phenotype data for the pedigree were analysed using heritability and linkage methods implemented in the programme SOLAR. Follow-up association analysis was performed using the CLUMP programme. A total of 154 migraine cases (25%) were identified indicating the Norfolk Island population is high-risk for migraine. Heritability estimation of the 377-member pedigree indicated a significant genetic component for migraine (h(2)=0.53, P=0.016). Linkage analysis showed peaks on chromosome 13q33.1 (P=0.003) and chromosome 9q22.32 (P=0.008). Association analysis of the key microsatellites in the remaining 223 unrelated Norfolk Island individuals showed evidence of association, which strengthen support for the linkage findings (P≤0.05). In conclusion, a genome-wide linkage analysis and follow-up association analysis of migraine in the genetic isolate of Norfolk Island provided evidence for migraine susceptibility loci on chromosomes 9q22.22 and 13q33.1.

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.

Significant differences in gene expression of GABA receptors in peripheral blood leukocytes of migraineurs

Migraine is a debilitating neurovascular disorder, with a substantial genetic component. The exact cause of a migraine attack is unknown; however cortical hyperexcitability is thought to play a role. As Gamma-aminobutyric Acid (GABA) is the major inhibitory neurotransmitter in the brain, malfunctioning of this system may be a cause of the hyperexcitability. To date, there has been limited research examining the gene expression or genetics of GABA receptors in relation to migraine. The aim of our study was to determine if GABA receptors play a role in migraine by investigating their gene expression using profile in migraine affected individuals and non-affected controls by Q-PCR. Gene expression of GABA(A) receptor subunit isoforms (GABRA3, GABRB3, GABRQ) and GABA(B) receptor 2 (GABBR2) was quantified in mRNA obtained from peripheral blood leukocytes from 28 migraine subjects and 22 healthy control subjects. Analysis of results showed that two of the tested genes, GABRA3 and GABBR2, were significantly down regulated in migraineurs (P=0.018; P=0.017), compared to controls. Results from the other tested genes did not show significant gene expression variation. The results indicate that there may be specific GABA receptor gene expression variation in migraine, particularly involving the GABRA3 and GABBR2 genes. This study also identifies GABRA3 and GABBR2 as potential biomarkers to select migraineurs that may be more responsive to GABA agonists with future investigations in this area warranted.

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.

Headache among mesial temporal lobe epilepsy patients: a case-control study

Epilepsy and headache are two chronic disorders that are characterized by recurrent attacks, but the relationship between them is not completely understood. Using a structured questionnaire, we investigated the prevalence of headache during the previous year in a homogeneous group of 100 patients with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). The control group consisted of 100 age-matched individuals who were randomized from a nationwide Brazilian headache database. There was a significantly higher prevalence of headache (92%) among the MTLE-HS patients when compared with the controls (73%; p=0.001). Chronic daily headache (CDH) was significantly associated with MTLE-HS (OR 6.1, CI 95% 1.7-22, p=0.005). We did not find any association between the diagnosis of migraine or tension-type headache and MTLE-HS. This study showed that MTLE-HS increases the likelihood of a headache diagnosis. In addition, CDH was more prevalent among the MTLE-HS patients, which supports a common pathophysiological mechanism for epilepsy and headache.

Painful heat reveals hyperexcitability of the temporal pole in interictal and ictal migraine States

During migraine attacks, alterations in sensation accompanying headache may manifest as allodynia and enhanced sensitivity to light, sound, and odors. Our objective was to identify physiological changes in cortical regions in migraine patients using painful heat and functional magnetic resonance imaging (fMRI) and the structural basis for such changes using diffusion tensor imaging (DTI). In 11 interictal patients, painful heat threshold + 1°C was applied unilaterally to the forehead during fMRI scanning. Significantly greater activation was identified in the medial temporal lobe in patients relative to healthy subjects, specifically in the anterior temporal pole (TP). In patients, TP showed significantly increased functional connectivity in several brain regions relative to controls, suggesting that TP hyperexcitability may contribute to functional abnormalities in migraine. In 9 healthy subjects, DTI identified white matter connectivity between TP and pulvinar nucleus, which has been related to migraine. In 8 patients, fMRI activation in TP with painful heat was exacerbated during migraine, suggesting that repeated migraines may sensitize TP. This article investigates a nonclassical role of TP in migraineurs. Observed temporal lobe abnormalities may provide a basis for many of the perceptual changes in migraineurs and may serve as a potential interictal biomarker for drug efficacy.

Headache, epilepsy and photosensitivity: how are they connected?

Although headache and epilepsy have often been associated, the precise electroclinical and pathophysiological interaction between these disorders and in particular its relations with photosensitivity is as yet to be fully understood in adults or children. The association between headache and epilepsy commonly occurs in all types of epilepsy and not only in occipital epilepsy. Generally, peri-ictal headache is often neglected, regardless of its severity, because patients are more concerned about their seizures. Altered cerebral cortex excitability may be the link between these two conditions and photosensitivity shows this. The physician should bear this association in mind when dealing with epileptic and migraine patients so as to be able to offer such patients an accurate diagnosis and appropriate treatment; this should be borne in mind when declaring epileptic patients ‘seizure free’. To date neither the International Headache Society nor the International League against Epilepsy mention that headache/migraine may, on occasion, be the sole ictal epileptic manifestation. Lastly, studies designed to investigate the triggering role of photosensitivity in both headache and epilepsy are warranted.

Comorbidities of migraine

Migraine is a common neurological disorder and can be severely disabling during attacks. The highest prevalence occurs between the ages of 25 and 55 years, potentially the most productive period of life. Migraine leads to a burden not only for the individual, but also for the family and society in general. Prior studies have found that migraine occurs together with other illnesses at a greater coincidental rate than is seen in the general population. These occurrences are called “comorbidities,” which means that these disorders are interrelated with migraine. To delineate the comorbidities of migraine is important, because it can help improve treatment strategies and the understanding of the possible pathophysiology of migraine. The comorbid illnesses in patients with migraine include stroke, sub-clinical vascular brain lesions, coronary heart disease, hypertension, patent foramen ovale, psychiatric diseases (depression, anxiety, bipolar disorder, panic disorder, and suicide), restless legs syndrome, epilepsy and asthma. In this paper, we review the existing epidemiological and hospital-based studies, and illustrate the connections between these illnesses and migraine.

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.

Sporadic hemiplegic migraine and epilepsy associated with CACNA1A gene mutation

Familial hemiplegic migraine (FHM) is a clinically and genetically heterogeneous disease most commonly linked to CACNA1A gene mutation. Epilepsy rarely occurs in FHM and is seen predominantly with specific CACNA1A gene mutations. Here we report a sporadic case of FHM1 linked to S218L CACNA1A gene mutation with the triad of prolonged hemiplegic migraine, cerebellar symptoms, and epileptic seizures. Epilepsy in this syndrome follows the pattern of isolated unprovoked seizures occurring only during childhood and hemiplegic migraine-provoked seizures occurring during adulthood. Clinical and electrographic status epilepticus can occur during prolonged migraine attacks. We suggest that patients with seizures, ataxia, and hemiplegic migraine be genetically tested for FHM. Patients with prolonged hemiplegic migraine attacks and confusion should be tested with continuous EEG recording to ascertain whether electrographic status is occurring, as intensive antiepileptic treatment not only resolves status but immediately stops hemiplegic migraine and improves associated neurological deficits.

[Is there a bridge between migraine and familial mesial temporal lobe epilepsy?]

Numerous reviews have emphasized the links between certain types of epilepsy and migraine. Historically, Gowers was one of the first, in 1907, to have drawn attention to a possible relationship between migraine headache and epilepsy in a period when no additional examination was available. In the last two decades, progress in molecular biology, electrophysiology, and neuro-imaging has enabled a better approach to the fundamental elements underlying the interrelationship between these two nosological domains. During this same time, a new term "channelopathy" has appeared in the literature. This term groups together affections involving a dysfunction of ion channels. In this article, the links between the different types of migraine and familial mesial temporal lobe epilepsy are illustrated by two case reports. This association does not appear to occur at random but would undoubtedly depend on a common genetic substratum, leading to a direct comorbidity. These occasional recurring symptoms would lie within the framework of a more general concept of "Primary Brain Channelopathies".

The borderland of epilepsy: clinical and molecular features of phenomena that mimic epileptic seizures

Paroxysmal losses of consciousness and other episodic neurological symptoms have many causes. Distinguishing epileptic from non-epileptic disorders is fundamental to diagnosis, but even this basic dichotomy is often challenging and is certainly not new. In 1907, the British neurologist William Richard Gowers published his book The Border-land of Epilepsy in which he discussed paroxysmal conditions "in the border-land of epilepsy-near it, but not of it" and their clinical differentiation from epilepsy itself. Now, a century later, we revisit the epilepsy borderland, focusing on syncope, migraine, vertigo, parasomnias, and some rarer paroxysmal disorders. For each condition, we review the clinical distinction from epileptic seizures. We then integrate current understanding of the molecular pathophysiology of these disorders into this clinical framework. This analysis shows that, although the clinical manifestations of paroxysmal disorders are highly heterogeneous, striking similarities in molecular pathophysiology are seen among many epileptic and non-epileptic paroxysmal phenomena.

Ictal Headache and Visual Sensitivity

Migrainous headache is reported by patients with photosensitive epilepsy, whereas their relatives complain more often about headache than the relatives of patients with other types of epilepsy. We therefore investigated whether headache itself could be an epileptic symptom related to photosensitivity Four probands with headache and photosensitive epilepsy were selected. Their first-degree family members were studied using video-EEG with extensive intermittent photic stimulation and pattern stimulation. Nine of the 12 subjects (10 female and two male, mean age 30 years, range 14–46 years) proved to be photosensitive with either focal ( n = 5) or generalized ( n = 4) epileptiform discharges. In two subjects an ictal recording of headache occurred after visual stimulation. We found evidence that, in specific patients, headache could be an ictal sign of epilepsy. Photic stimulation during EEG recording can contribute to correct diagnosis and lead to the best care and management of the patient.

Genetics of migraine: an update with special attention to genetic comorbidity

PURPOSE OF REVIEW

To highlight recent genetic findings in migraine and discuss, new mutations in hemiplegic migraine genes in familial and sporadic cases and relevant candidate gene association studies. Special attention will be given to comorbid diseases of migraine.

RECENT FINDINGS

Familial hemiplegic migraine (FHM) is genetically heterogeneous with mutations in the CACNA1A (FHM1), ATP1A2 (FHM2) and SCN1A (FHM3) genes. Nineteen novel ATP1A2 mutations were identified last year, eleven of them in FHM2 families. A systematic genetic analysis of patients with sporadic hemiplegic migraine revealed five mutations in this gene, which has implications for genetic counselling. The identification of a second FHM3 SCN1A mutation definitely established SCN1A as a migraine gene. The identification of TREX1 mutations in families with retinal vasculopathy and associated diseases such as migraine may provide new insights in migraine pathophysiology.

SUMMARY

Many novel ATP1A2 mutations were identified in patients with familial and sporadic hemiplegic migraine. In sporadic patients, ATP1A2 screening has the highest chance of finding a causal mutation. A second FHM3 mutation definitely established the epilepsy SCN1A gene as a migraine gene. The discovery of genes in monogenic diseases in which migraine is prominent may lead to new insights in the molecular pathways involved in migraine pathophysiology.

Paroxysmal exercise-induced dyskinesia and epilepsy is due to mutations in SLC2A1, encoding the glucose transporter GLUT1

Paroxysmal exercise-induced dyskinesia (PED) can occur in isolation or in association with epilepsy, but the genetic causes and pathophysiological mechanisms are still poorly understood. We performed a clinical evaluation and genetic analysis in a five-generation family with co-occurrence of PED and epilepsy (n = 39), suggesting that this combination represents a clinical entity. Based on a whole genome linkage analysis we screened SLC2A1, encoding the glucose transporter of the blood-brain-barrier, GLUT1 and identified heterozygous missense and frameshift mutations segregating in this and three other nuclear families with a similar phenotype. PED was characterized by choreoathetosis, dystonia or both, affecting mainly the legs. Predominant epileptic seizure types were primary generalized. A median CSF/blood glucose ratio of 0.52 (normal >0.60) in the patients and a reduced glucose uptake by mutated transporters compared with the wild-type as determined in Xenopus oocytes confirmed a pathogenic role of these mutations. Functional imaging studies implicated alterations in glucose metabolism in the corticostriate pathways in the pathophysiology of PED and in the frontal lobe cortex in the pathophysiology of epileptic seizures. Three patients were successfully treated with a ketogenic diet. In conclusion, co-occurring PED and epilepsy can be due to autosomal dominant heterozygous SLC2A1 mutations, expanding the phenotypic spectrum associated with GLUT1 deficiency and providing a potential new treatment option for this clinical syndrome.