Partial cosegregation of familial hemiplegic migraine and a benign familial infantile epileptic syndrome

PRRT2 Related Epilepsies: A Gene Review

PRRT2 encodes for proline-rich transmembrane protein 2 involved in synaptic vesicle fusion and presynaptic neurotransmitter release. Mutations in human PRRT2 have been related to paroxysmal kinesigenic dyskinesia (PKD), infantile convulsions with choreoathetosis, benign familial infantile epilepsies, and hemiplegic migraine. PRRT2 mutations cause neuronal hyperexcitability, which could be related to basal ganglia or cortical circuits dysfunction, leading to paroxysmal disorders. PRRT2 is expressed in the cerebral cortex, basal ganglia, and cerebellum. Approximately, 90% of pathogenic variants are inherited and 10% are de novo. Paroxysmal attacks in PKD are characterized by dystonia, choreoathetosis, and ballismus. In the benign familial infantile epilepsy (BFIE), seizures are usually focal with or without generalization, usually begin between 3 and 12 months of age and remit by 2 years of age. In 30% of cases of PRRT2-associated PKD, there is an association with BFIE, and this entity is referred to as PKD with infantile convulsions (PKD/IC). PRRT2 mutations are the cause of benign family childhood epilepsy and PKD/IC. On the other hand, PRRT2 mutations do not seem to correlate with other types of epilepsy. The increasing incidence of hemiplegic migraine in families with PRRT2-associated PKD or PKD/IC suggests a common disease pathway, and it is possible to assert that BFIE, paroxysmal kinesigenic dyskinesia, and PKD with IC belong to a continuous disease spectrum of PRRT2-associated diseases.

Epilepsy in patients with familial hemiplegic migraine

OBJECTIVE

The coexistence of epilepsy in familial hemiplegic migraine (FHM) has not been reviewed systematically. We investigated the associations of epilepsy in patients with FHM with CACNA1A, ATP1A2, SCN1A or PRRT2 mutations along with clinical and genetic data.

MATERIALS AND METHODS

We performed a search in the PubMed bibliographic database and the Cochrane Library was screened for eligible studies, from April 1997 to December 2020. Additionally, Online Mendelian Inheritance in Man (OMIM) was searched for mutations in the CACNA1A, ATP1A2, SCN1A and PRRT2 genes. Brief reports, letters, and original articles about FHM and epilepsy were included in the review if their mutations and clinical course of diseases were identified.

RESULTS

Of the included patients with FHM whose information could be accessed, there were 28 families and 195 individuals, 78 of whom had epilepsy; 30 patients had focal epilepsy and 30 patients had generalized epilepsy. All mutations except ATP1A2, which could not be evaluated due to insufficient data, revealed first epilepsy then HM. In 60 patients for whom the epilepsy prognosis was evaluated, only 3.5% of patients were drug-resistant, and the remainder had a self-limited course or responded to anti-epileptic drug treatment.

CONCLUSION

Mutations in all three and possibly four FHM genes can cause epilepsy. Contrary to our expectations, the well-known epilepsy gene SCN1A mutations are not the leading cause; the highest number of cases associated with epilepsy belongs to the ATP1A2 mutation. Drug-resistant forms of epilepsy are rare in all FHM mutations, and this information is important for counseling patients.

Diagnostic and therapeutic aspects of hemiplegic migraine

Hemiplegic migraine (HM) is a clinically and genetically heterogeneous condition with attacks of headache and motor weakness which may be associated with impaired consciousness, cerebellar ataxia and intellectual disability. Motor symptoms usually last <72 hours and are associated with visual or sensory manifestations, speech impairment or brainstem aura. HM can occur as a sporadic HM or familiar HM with an autosomal dominant mode of inheritance. Mutations in CACNA1A, ATP1A2 and SCN1A encoding proteins involved in ion transport are implicated. The pathophysiology of HM is close to the process of typical migraine with aura, but appearing with a lower threshold and more severity. We reviewed epidemiology, clinical presentation, diagnostic assessment, differential diagnosis and treatment of HM to offer the best evidence of this rare condition. The differential diagnosis of HM is broad, including other types of migraine and any condition that can cause transitory neurological signs and symptoms. Neuroimaging, cerebrospinal fluid analysis and electroencephalography are useful, but the diagnosis is clinical with a genetic confirmation. The management relies on the control of triggering factors and even hospitalisation in case of long-lasting auras. As HM is a rare condition, there are no randomised controlled trials, but the evidence for the treatment comes from small studies.

Spreading depression and the clinical correlates of migraine

Migraine is the most common neurologic condition. One-third of migraineurs experience transient neurologic symptoms, the so-called aura. There is strong evidence that spreading depression (SD) is the electrophysiologic substrate of migraine aura. SD is an intense pan-depolarization wave that slowly propagates in gray matter by way of contiguity and transiently disrupts neuronal function. When induced subcortically, striatal SD causes hemiparesis, hippocampal SD can trigger seizures and impact cognition, and bilateral thalamic SD can diminish consciousness. Recent data show that transgenic mice expressing familial hemiplegic migraine (FHM) type 1 mutations in voltage-gated Ca2+ channels (Cav2.1) develop mutation-specific aura-like signs after a cortical SD similar to patients with the respective mutation. These signs are associated with facilitated subcortical SD propagation. As in FHM, mice with the R192Q mutation develop pure hemiplegia associated with cortical SDs propagating into caudoputamen. S218L mice display additional signs such as seizures and coma when SD propagates into hippocampus and thalamus. In hyperexcitable FHM brains, SD may propagate between cortex and subcortical structures via permissive gray matter bridges, or originate de novo in subcortical structures, to explain unusual and severe aura signs and symptoms. Reciprocal spread and reverberating waves can explain protracted attacks.

Triple cysteine module within M-type K+ channels mediates reciprocal channel modulation by nitric oxide and reactive oxygen species

We have identified a new signaling role for nitric oxide (NO) in neurons from the trigeminal ganglia (TG). We show that in rat sensory neurons from the TG the NO donor, S-nitroso-N-acetyl-dl-penicillamine, inhibited M-current. This inhibitory effect was blocked by NO scavenging, while inhibition of NO synthases increased M-current, suggesting that tonic NO levels inhibit M-current in TG neurons. Moreover NO increased neuronal excitability and calcitonin gene-related peptide (CGRP) release and these effects could be prevented by perturbing M-channel function. First, NO-induced depolarization was prevented by pre-application of the M-channel blocker XE991 and second, NO-induced increase in CGRP release was prevented by incubation with the M-channel opener retigabine. We investigated the mechanism of the effects of NO on M-channels and identified a site of action of NO to be the redox modulatory site at the triplet of cysteines within the cytosolic linker between transmembrane domains 2 and 3, which is also a site of oxidative modification of M-channels by reactive oxygen species (ROS). NO and oxidative modifications have opposing effects on M-current, suggesting that a tightly controlled local redox and NO environment will exert fine control over M-channel activity and thus neuronal excitability. Together our data have identified a dynamic redox sensor within neuronal M-channels, which mediates reciprocal regulation of channel activity by NO and ROS. This sensor may play an important role in mediating excitatory effects of NO in such trigeminal disorders as headache and migraine.

Idiopathic focal epilepsies

In this chapter we include a series of epilepsies with onset in pediatric age characterized by focal seizures, idiopathic etiology, normal psychomotor development, and a benign course related to the spontaneous remission of seizures without sequelae. These entities are age-dependent and seizures tend to disappear spontaneously. For these reasons often the drug treatment is not necessary. On the basis of genetic assessment idiopathic focal epilepsies can be divided into two groups: nonautosomal dominant and autosomal dominant. In the group of nonautosomal entities we include benign epilepsy with centro-temporal spikes, Panayiotopoulos syndrome, idiopathic childhood occipital epilepsy described by Gastaut, and benign idiopathic midline spikes epilepsy. Seizures are rare, sometimes prolonged, as autonomic status in Panayiotopoulos syndrome. A common feature is the presence of peculiar EEG interictal paroxysmal abnormalities. In the group with an autosomal dominant mode of inheritance we include benign familial infantile seizures and benign familial neonatal-infantile seizures. These entities are characterized by partial seizures in cluster, self-limited in a brief period during the first months of life. There are no typical interictal EEG abnormalities. In some families a mutation in SCN2A, the gene coding for the 2α subunit of the voltage-gated sodium channel, has been described.

Migraine- and dystonia-related disease-mutations of Na+/K+-ATPases: relevance of behavioral studies in mice to disease symptoms and neurological manifestations in humans

The two autosomal dominantly inherited neurological diseases: familial hemiplegic migraine type 2 (FHM2) and familial rapid-onset of dystonia-parkinsonism (Familial RDP) are caused by in vivo mutations of specific alpha subunits of the sodium-potassium pump (Na(+)/K(+)-ATPase). Intriguingly, patients with classical FHM2 and RDP symptoms additionally suffer from other manifestations, such as epilepsy/seizures and developmental disabilities. Recent studies of FHM2 and RDP mouse models provide valuable tools for dissecting the vital roles of the Na(+)/K(+)-ATPases, and we discuss their relevance to the complex patient symptoms and manifestations. Thus, it is interesting that mouse models targeting a specific α-isoform cause different, although still comparable, phenotypes consistent with classical symptoms and other manifestations observed in FHM2 and RDP patients. This review highlights that use of mouse models have broad potentials for future research concerning migraine and dystonia-related diseases, which will contribute towards understanding the, yet unknown, pathophysiologies.

Variants in the human potassium channel gene (KCNN3) are associated with migraine in a high risk genetic isolate

The calcium-activated potassium ion channel gene (KCNN3) is located in the vicinity of the familial hemiplegic migraine type 2 locus on chromosome 1q21.3. This gene is expressed in the central nervous system and plays a role in neural excitability. Previous association studies have provided some, although not conclusive, evidence for involvement of this gene in migraine susceptibility. To elucidate KCNN3 involvement in migraine, we performed gene-wide SNP genotyping in a high-risk genetic isolate from Norfolk Island, a population descended from a small number of eighteenth century Isle of Man ‘Bounty Mutineer’ and Tahitian founders. Phenotype information was available for 377 individuals who are related through the single, well-defined Norfolk pedigree (96 were affected: 64 MA, 32 MO). A total of 85 SNPs spanning the KCNN3 gene were genotyped in a sub-sample of 285 related individuals (76 affected), all core members of the extensive Norfolk Island ‘Bounty Mutineer’ genealogy. All genotyping was performed using the Illumina BeadArray platform. The analysis was performed using the statistical program SOLAR v4.0.6 assuming an additive model of allelic effect adjusted for the effects of age and sex. Haplotype analysis was undertaken using the program HAPLOVIEW v4.0. A total of four intronic SNPs in the KCNN3 gene displayed significant association (P < 0.05) with migraine. Two SNPs, rs73532286 and rs6426929, separated by approximately 0.1 kb, displayed complete LD (r² = 1.00, D′ = 1.00, D′ 95% CI = 0.96–1.00). In all cases, the minor allele led to a decrease in migraine risk (beta coefficient = 0.286–0.315), suggesting that common gene variants confer an increased risk of migraine in the Norfolk pedigree. This effect may be explained by founder effect in this genetic isolate. This study provides evidence for association of variants in the KCNN3 ion channel gene with migraine susceptibility in the Norfolk genetic isolate with the rarer allelic variants conferring a possible protective role. This the first comprehensive analysis of this potential candidate gene in migraine and also the first study that has utilised the unique Norfolk Island large pedigree isolate to implicate a specific migraine gene. Studies of additional variants in KCNN3 in the Norfolk pedigree are now required (e.g. polyglutamine variants) and further analyses in other population data sets are required to clarify the association of the KCNN3 gene and migraine risk in the general outbred population.

Pregabalin modulation of neurotransmitter release is mediated by change in intrinsic activation/inactivation properties of ca(v)2.1 calcium channels

In this work, we studied the effects of the anticonvulsant and analgesic drug pregabalin (PGB) on excitatory postsynaptic currents (EPSCs) at principal neurons of the mouse medial nucleus of the trapezoid body and on presynaptic calcium currents at the calyx of Held. We found that the acute application of PGB reduced the amplitude of EPSCs in a dose-dependent manner with a maximal blocking effect of approximately 30%. A clinical high-concentration dose of PGB (e.g., 500 μM) blocked Ca(v)2.1 channel-mediated currents and decreased their facilitation during a 100-Hz train, without changing their voltage-dependent activation. Furthermore, PGB also removed the inactivation of Ca(v)2.1 channels at a clinically relevant low concentration of 100 μM. These results suggest novel modulatory mechanisms mediated by the acute administration of PGB on fast excitatory synaptic transmission and might contribute to better understanding PGB anticonvulsant/analgesic clinical effects.

Genetic and hormonal factors modulate spreading depression and transient hemiparesis in mouse models of familial hemiplegic migraine type 1

Familial hemiplegic migraine type 1 (FHM1) is an autosomal dominant subtype of migraine with aura that is associated with hemiparesis. As with other types of migraine, it affects women more frequently than men. FHM1 is caused by mutations in the CACNA1A gene, which encodes the alpha1A subunit of Cav2.1 channels; the R192Q mutation in CACNA1A causes a mild form of FHM1, whereas the S218L mutation causes a severe, often lethal phenotype. Spreading depression (SD), a slowly propagating neuronal and glial cell depolarization that leads to depression of neuronal activity, is the most likely cause of migraine aura. Here, we have shown that transgenic mice expressing R192Q or S218L FHM1 mutations have increased SD frequency and propagation speed; enhanced corticostriatal propagation; and, similar to the human FHM1 phenotype, more severe and prolonged post-SD neurological deficits. The susceptibility to SD and neurological deficits is affected by allele dosage and is higher in S218L than R192Q mutants. Further, female S218L and R192Q mutant mice were more susceptible to SD and neurological deficits than males. This sex difference was abrogated by ovariectomy and senescence and was partially restored by estrogen replacement, implicating ovarian hormones in the observed sex differences in humans with FHM1. These findings demonstrate that genetic and hormonal factors modulate susceptibility to SD and neurological deficits in FHM1 mutant mice, providing a potential mechanism for the phenotypic diversity of human migraine and aura.

What's new in: "genetics in childhood epilepsy"

In recent years, different mutations in genes that control the excitability of neurons have been described in idiopathic childhood epilepsies. Most commonly, sodium/potassium channelopathies and GABA-receptor mutations are involved. Major progress has been made in the field of idiopathic generalised epilepsies associated with febrile seizures (GEFS+). It now is becoming clear that mutations should not only be looked for in familial cases, but also in sporadic cases, especially in infants and young children with unexplained severe epileptic encephalopathies. Many studies also define 'epilepsy susceptibility genes', which contribute to one's individual genetic vulnerability to develop epilepsy. It should be realized, however, that in the most common idiopathic benign childhood epilepsies (benign rolandic and occipital epilepsies), major breakthroughs are still awaited. In addition, a better clinical description of the epileptic phenotypes is needed to explain more precisely the genotypic and phenotypic heterogeneity. Genetic studies are nowadays becoming a necessary diagnostic step in the evaluation of idiopathic childhood epilepsies, not only in familial cases, but also in sporadic cases.

Migraine genetics: an update

A growing interest in genetic research in migraine has resulted in the identification of several chromosomal regions that are involved in migraine. However, the identification of mutations in the genes for familial hemiplegic migraine (FHM) forms the only true molecular genetic knowledge of migraine thus far. The increased number of mutations in the FHM1 (CACNA1A) and the FHM2 (ATP1A2) genes allow studying the relationship between genetic findings in both genes and the clinical features in patients. A wide spectrum of symptoms is seen in patients. Additional cerebellar ataxia and (childhood) epilepsy can occur in FHM1 and FHM2. Functional studies show a dysfunction in ion transport as the key factor in the pathophysiology of (familial hemiplegic) migraine that predict an increased susceptibility to cortical spreading depression--the underlying mechanism of migraine aura.

The spectrum of benign infantile seizures

Benign epilepsies during infancy are a wide topic, which needs both clinical and nosological clarifications. Already in 1963 Fukuyama reported patients with seizures during infancy with a benign outcome. In the late 80s and early 90s, Watanabe reported series of infants with complex partial seizures or partial seizures with secondary generalization, with a normal development before onset and a benign outcome. In the same years Vigevano focused on familial cases: he described several families with seizures with onset around the 6-month of age, and autosomal dominant mode of inheritance. To define this condition, he coined the term "benign familial infantile seizures" (BFIS). Afterwards, studying families with this phenotype, loci on chromosomes 19, 16 and 2 responsible for BFIS were detected. Similar loci were found in families affected by BFIS and subsequent choreoathetosis, and BFIS associated with familial hemiplegic migraine. In most recent years a new form of benign epilepsy has been proposed, with an intermediate onset between the neonatal and infantile age, which was defined with the term benign familial neonatal-infantile seizures (BFNIS). This condition could have some clinical and genetic features overlapping with BFIS. Seizures with a benign outcome have been reported also in infants during episode of mild gastroenteritis (BIS with MG) frequently with positive Rotavirus antigen. Lastly, sleep EEG abnormalities have been reported in children with a peculiar form of epilepsy by Capovilla, who defined this condition as benign infantile focal epilepsy with midline spikes and waves during sleep (BIMSE). Some of these entities have been included in the last classification proposed by the ILAE and have been differentiated in familial and non-familial forms. The aim of this review is to describe these entities, discuss their nosological aspects, pointing out the similarities and differences with benign neonatal seizures and benign focal epilepsies appearing later in life such as early-onset benign occipital seizure susceptibility syndrome (EBOSS), or benign epilepsy of childhood with centro-temporal spikes (BECTS).

Linkage analysis and disease models in benign familial infantile seizures: a study of 16 families

PURPOSE

Benign familial infantile seizures (BFIS) is a genetically heterogeneous condition characterized by partial seizures, onset age from 3 to 9 months, and favorable outcome. BFIS loci were identified on chromosomes 19q12-13.1 and 16p12-q12, allelic to infantile convulsions and choreathetosis. The identification of SCN2A mutations in families with only infantile seizures indicated that BFNIS and BFIS may show overlapping clinical features. Infantile seizures also were in a family with familial hemiplegic migraine and mutations in the ATP1A2 gene. We have examined the heterogeneous genetics of BFIS by means of linkage analysis.

METHODS

Sixteen families were examined. Probands underwent neurologic examination, at least one EEG recording, and, when possible, brain CT and MRI. Clinical information about relatives was collected. Families with SCN2A or ATP1A2 mutations were excluded from the study. Chromosome 16p and 19q loci were examined by linkage analysis using two models that differed in penetrance rate. Genetic heterogeneity was evaluated with both models.

RESULTS

Clinical information was available for 124 members of affected families. BFIS was diagnosed in 69 subjects. One patient without BFIS had a single febrile seizure, and another had rare episodes of paroxysmal dystonia. Evidence of linkage was obtained only for chromosome 16. Moreover, the high penetrance allowed the identification of genetic heterogeneity.

CONCLUSIONS

Our data confirm the relevance of the chromosome 16 locus in BFIS and suggest the presence of an additional locus. This study shows that the genetic model used affects the outcome of linkage analysis.

Both insulin and calcium channel signaling are required for developmental regulation of serotonin synthesis in the chemosensory ADF neurons of Caenorhabditis elegans

Proper calcium channel and insulin signaling are essential for normal brain development. Leaner mice with a mutation in the P/Q-type voltage-gated calcium channel, Cacna1a, develop cerebellar atrophy and mutations in the homologous human gene are associated with increased migraine and seizure tendency. Similarly, abnormalities in insulin signaling are associated with abnormal brain growth and migraine tendency. Previously, we have shown that in the ADF chemosensory neurons of Caenorhabditis elegans UNC-2/Ca(2+) channel function affects TGF-beta-dependent developmental regulation of tryptophan hydroxylase, the rate-limiting enzyme in serotonin synthesis. Here we show that developmental expression of a tryptophan hydroxylase: :GFP reporter construct is similarly decreased by reduction-of-function mutations in the daf-2/insulin receptor. This decreased expression of tryptophan hydroxylase observed in both the daf-2 and unc-2 mutant backgrounds is suppressible either genetically by reduction-of-function mutations in the daf-16/forkhead transcription factor, an effector of the DAF-2/insulin receptor, or pharmacologically by the serotonin receptor antagonist cyproheptadine. Overall, these data suggest that both UNC-2 and DAF-2 function are required in the developmental regulation of DAF-16 and serotonin-dependent inhibition of tryptophan hydroxylase expression.

A Novel SCN2A Mutation in Family with Benign Familial Infantile Seizures

Benign familial infantile seizures (BFIS) is a clinical entity characterized by focal seizures with or without secondary generalization, occurring mostly in clusters, and usually first seen between 4 and 8 months of life. Psychomotor development is normal, and seizures usually resolve within the first year of life. BFIS is a genetically heterogenous condition with loci mapped to chromosomes 19 and 16. Mutations in the voltage-gated sodium channel alpha2 subunit (SCN2A) gene on chromosome 2 were recently identified in families affected by neonatal and infantile seizures (benign familial neonatal-infantile seizures, BFNIS) with typical onset before 4 months of life. The identification of SCN2A mutations in families with only infantile seizures indicated that BFNIS and BFIS show overlapping clinical features. We report a pedigree showing three affected individuals over three generations. All subjects experienced clusters of focal seizures with or without secondary generalization and onset between 4 and 12 months of life. Response to antiepileptic drugs and the outcome were good. No subjects had other forms of epilepsy later in the life. Neonatal or febrile seizures did not occur in the family. Genetic study in this family revealed a novel heterozygous mutation c.3003 T>A in the SCN2A gene. Comparative analysis of different sodium channel alpha subunits indicates that the mutated residue is highly conserved throughout the evolution, suggesting an important functional role for this domain. Additional families with the infantile form of benign familial seizures should be investigated to corroborate that BFIS and BFNIS may share the same genetic abnormality.

No evidence of ATP1A2 involvement in 12 multiplex Italian families with benign familial infantile seizures

A missense mutation in the gene encoding the alpha(2) subunit of the Na(+),K(+) ATPase pump (ATP1A2) was found in a family with both familial hemiplegic migraine (FHM) and Benign Familial Infantile Seizures (BFIC). As it is still unclear whether ATP1A2 is responsible for pure BFIC syndromes, we checked mutations of the ATP1A2 gene in probands of 12 Italian multiplex families with pure BFIC, who were negative for mutations in the SCN2A gene. We screened the ATP1A2 gene by denaturing high performance liquid chromatography (D-HPLC) and direct sequencing of DNA fragments showing an aberrant elution pattern. We found one exonic variant and five intronic variants, none leading to significant amino acid changes or causing a modification of the physiological mRNA maturation. The ATP1A2 gene does not appear to be involved in the ethiopathogenesis of pure BFIC syndromes, at least in the explored Italian multiplex families. It could be either responsible of a minority of cases, or of complex syndromes where BFIC and FHM co-occur.

Benign familial infantile convulsions: linkage to chromosome 16p12-q12 in 14 families

PURPOSE

Benign familial infantile convulsions (BFIC) is a form of idiopathic epilepsy. It is characterized by clusters of afebrile seizures occurring around the sixth month of life. The disease has a benign course with a normal development and rare seizures in adulthood. Previous linkage analyses defined three susceptibility loci on chromosomes 19q12-q13.11, 16p12-q12, and 2q23-31. However, a responsible gene has not been identified. We studied linkage in 16 further BFIC families.

METHODS

We collected 16 BFIC families, without an additional paroxysmal movement disorder, of German, Turkish, or Japanese origin with two to eight affected individuals. Standard two-point linkage analysis was performed.

RESULTS

The clinical picture included a large variety of seizure semiologies ranging from paleness and cyanosis with altered consciousness to generalized tonic-clonic seizures. Interictal EEGs showed focal epileptiform discharges in six patients, and three ictal EEGs in three distinct patients revealed a focal seizure onset in different brain regions. In all analyzed families, we found no evidence for linkage to the BFIC loci on chromosomes 19q and 2q, as well as to the known loci for benign familial neonatal convulsions on chromosomes 8q and 20q. In 14 of the families, the chromosome 16 locus could be confirmed with a cumulative maximum two-point lod score of 6.1 at marker D16S411, and the known region for BFIC could be narrowed to 22.5 Mbp between markers D16S690 and D16S3136.

CONCLUSIONS

Our data confirm the importance of the chromosome 16 locus for BFIC and may narrow the relevant interval.

Toward a molecular genetic classification of familial hemiplegic migraine

The genetics of migraine is a fascinating and rapidly moving research area. Familial hemiplegic migraine, a rare subtype of migraine with a Mendelian pattern of inheritance, is caused by mutations in the chromosome 19 CACNA1A gene or in the chromosome 1 ATP1A2 gene. Familial migraine variants are classified on the basis of clinical, descriptive criteria, but this is insufficient. In the future, a diagnostic classification based on mutation-analysis is needed.

Novel mutations in the Na+, K+-ATPase pump gene ATP1A2 associated with familial hemiplegic migraine and benign familial infantile convulsions

Familial hemiplegic migraine (FHM) is a rare, severe, autosomal dominant subtype of migraine with aura. Up to 75% of FHM families have a mutation in the P/Q-type calcium channel Ca(v)2.1 subunit CACNA1A gene on chromosome 19p13. Some CACNA1A mutations also may cause epilepsy. Here, we describe novel missense mutations in the ATP1A2 Na(+),K(+)-ATPase pump gene on chromosome 1q23 in two families with FHM. The M731T mutation was found in a family with pure FHM. The R689Q mutation was identified in a family in which FHM and benign familial infantile convulsions partially cosegregate. In this family, all available affected family members with FHM, benign familial infantile convulsions, or both, carry the ATP1A2 mutation. Like FHM linked to 19p13, FHM linked to 1q23 also involves dysfunction of ion transportation and epilepsy is part of its phenotypic spectrum.

Evidence for a separate type of migraine with aura: sporadic hemiplegic migraine

OBJECTIVE

To compare clinical characteristics of patients with sporadic hemiplegic migraine (SHM) with those of patients with migraine with typical aura (MA) and patients with familial hemiplegic migraine (FHM).

METHODS

The authors used a computer search of Denmark's National Patient Register to screen the population for patients with migraine with aura with motor weakness, and also examined case records from headache clinics and private practicing neurologists and placed advertisements. The authors screened patients and their relatives with a semi-structured validated telephone interview. All recruited patients were then interviewed by a physician and given a neurologic examination.

RESULTS

A total of 105 patients with SHM were identified. Seventy-two percent had four typical aura symptoms: visual, sensory, aphasic, and motor. All had at least two symptoms present during SHM attacks. A gradual progression and sequential appearance of aura symptoms was typical; compared with MA, the duration of each aura symptom was usually prolonged and bilateral motor symptoms were more frequent. Of the patients with SHM, 72% fulfilled the criteria for basilar migraine during SHM attacks. The aura was usually followed by headache, as is common in FHM but not MA.

CONCLUSIONS

Patients with sporadic hemiplegic migraine had clinical symptoms identical to familial hemiplegic migraine and significantly different from migraine with typical aura. Sporadic hemiplegic migraine is a separate entity, and should be classified with familial hemiplegic migraine.

Benign familial infantile seizures: further delineation of the syndrome

Benign familial infantile seizures are an autosomal dominant epilepsy disorder that is characterized by convulsions, with onset at age 3 to 12 months and a favorable outcome. Benign familial infantile seizures have been linked to chromosome 19q whereas infantile convulsions and choreoathetosis syndrome, in which benign familial infantile seizure is associated with paroxysmal choreoathetosis, has been linked to chromosome 16p 12-q12. Many additional families from diverse ethnic backgrounds have similar syndromes that have been linked to the chromosome 16 infantile convulsions and choreoathetosis syndrome region. Moreover, in one large pedigree with paroxysmal kinesiogenic dyskinesias only, the syndrome has also been linked to the same genomic area. Families with pure benign familial infantile seizures may be linked to chromosome 16 as well. In this study, we present a series of 19 families and 24 otherwise healthy infants with benign familial infantile seizures. Two of these families include members affected with benign familial infantile seizures and paroxysmal choreoathetosis. We included patients with normal neurologic examinations, who started having simple partial seizures, complex partial seizures, or apparently generalized seizures without recognized etiology between 2 months and 2 years of age. Neurologic studies were normal, but in all patients, there was a history of similar seizures and age at onset in either the father or the mother. Twenty-four patients (14 girls and 10 boys) were evaluated at our hospital between February 1990 and February 2001. Age at onset, sex, family history of epilepsy and/or paroxysmal dyskinesias, neurologic examination, semiology, distribution, and frequency and duration of seizures were evaluated. Electroencephalographic (EEG) and neuroradiologic studies were also performed. Seizures began between 3 and 22 months of life, with a median age of 5 1/2 months. Nine patients (37.5%) had only apparently generalized seizures, 5 patients (20.8%) had only partial seizures, and 10 patients had both partial and apparently generalized seizures (41.6%). Seizures were invariably brief, occurred during the waking state (100%), and presented mainly in clusters in 12 patients (50%). Interictal EEG was normal in 23 patients (95.8%). Sixteen patients (66.6%) had a confirmed history of convulsions in family members other than parents. Twenty-two patients became seizure free after 30 months of life. Two brothers in the same family had brief paroxysmal episodes of choreoathetosis in the hemibody triggered by stress while awake at 15 and 17 years old, respectively. One of them had paroxysmal choreoathetosis only, and the other was associated with benign familial infantile seizures. One father had brief spontaneous episodes of paroxysmal choreoathetosis when awake at age 18 years. All of them had a good response to antiepilepsy drugs, and neurologic examination and EEG and neuroradiologic studies were normal. Benign familial infantile seizure is a genetic epilepsy syndrome with autosomal dominant inheritance. It may be associated with paroxysmal choreoathetosis (infantile convulsions and choreoathetosis syndrome), which has been linked to the chromosome 16 infantile convulsions and choreoathetosis syndrome region. Patients in families with infantile convulsions and choreoathetosis syndrome could display either benign familial infantile seizures or paroxysmal choreoathetosis or both. It is likely that the disease in families with pure benign familial infantile seizures may be linked to the infantile convulsions and choreoathetosis region as well. We cannot exclude the possibility that the youngest patients may develop choreoathetosis or other dyskinesias later in life.

Ictal and interictal single photon emission computed tomography in a patient with benign familial infantile convulsions

Ictal and interictal single photon emission computed tomography (SPECT) and ictal electroencephalography (EEG) were studied in a 3-month-old girl with benign familial infantile convulsions (BFIC) to reveal the epileptic focus. There was bilateral diffuse propagation from a left frontal lobe focus on the ictal EEG. Perfusion in the left frontal region was increased on ictal SPECT and decreased on interictal SPECT. Epileptic foci of BFIC showed the same characteristics as foci of symptomatic partial epilepsy.

Idiopathic epilepsy and paroxysmal dyskinesia

Although some motor manifestations of epilepsy and of paroxysmal dyskinesia may be difficult to differentiate clinically, the current understanding is that the two disorders are clinically distinct. However, there are several recent reports of families in which different individuals had either disorder or both manifestations, with age-related expression. Co-occurrence makes it likely that a common, genetically determined, pathophysiologic abnormality is variably expressed in the cerebral cortex and in basal ganglia. A rather homogeneous syndrome of autosomal dominant infantile convulsions and paroxysmal (dystonic) choreoathetosis (ICCA) was described in six families from France, China and Japan. Linkage analysis in the French and Chinese families allowed the mapping of the disease gene in a 10-cM interval within the pericentromeric region of chromosome 16. An Italian pedigree in which three members in the same generation were affected by rolandic epilepsy, paroxysmal exercise-induced dystonia (PED), and writer's cramp was subsequently reported. Linkage analysis showed a common homozygous haplotype in a critical region spanning 6 cM and entirely included within the ICCA critical region. Clinical analogies and linkage findings suggest that the same gene could be responsible for rolandic epilepsy, PED, writer's cramp (WC), and ICCA, with specific mutations accounting for each of these mendelian disorders. Evidence for a major gene or a cluster of genes for epilepsy and paroxysmal dyskinesia to the pericentromeric region of chromosome 16 is reinforced by the recent linkage of a family with autosomal dominant paroxysmal dyskinesia to a critical region partially overlapping with ICCA and contiguous to the RE-PED-WC regions. Additional autosomal dominant pedigrees are on record, from Australia and Italy, in which epilepsy was variably associated with paroxysmal kinesigenic or exercise-induced dystonia. Ion channel genes are potentially interesting candidates for syndromes featuring both these paroxysmal neurologic disorders. Increased awareness of their possible co-occurrence will certainly increase the number of observations in the next few years.

Prevalence of positive anticardiolipin antibody in benign infantile convulsion

We report six anticardiolipin antibody (aCL)-positive cases among 18 children with epilepsy showing various seizure types in our initial study. These six cases revealed normal coagulation tests. As three of these six cases involved benign infantile convulsion (BIC), we further investigated the high frequency of positive aCL-Immunoglobulin (Ig) G in BIC in our subsequent study of nine cases that included three cases from the previous study and an additional six BIC cases followed and/or diagnosed by co-author (T.K.). As a result, eight of nine BIC cases were positive for aCL-IgG and the values of aCL-IgG decreased over long-term observation in three of these cases. The frequency of positivity for aCL-IgG in BIC was obviously higher than that of controls. Based on these results, we suggest that some immunological responses may be responsible for the pathogenesis of BIC.

Molecular genetics of migraine headaches: a review

Following the recent discovery of neural calcium channel mutations in familial hemiplegic migraine, genetic linkage and association studies have been performed world-wide in an effort to unveil the genetic basis of the more common types of migraine too. Mutations in neural calcium channels, mitochondrial DNA, serotonin receptors and transporter, dopamine receptors and genetic prothrombotic risk factors have been especially investigated and are discussed here. No unambiguous conclusions have, however, been reached. FHM remains an isolated success story in the quest for the genetic basis of migraine.

Current status of genetic discoveries in migraine: familial hemiplegic migraine and beyond

Familial hemiplegic migraine (FHM) has been related to mutations in a brain calcium channel gene among Chr19p linked FHM families. Subsequent genetic Studies in different FHM families showed that additional causative genes must reside in other regions of the genome, including the long arm of Chromosome 1. Parallel discoveries in mouse mutants involving ion channel genes have also accelerated our understanding of the spectrum and functional significance of the CNS-related ion channel disorders. These studies have clear implications for migraine, epilepsy, and ataxia. An association study was suggested that other 'susceptibility' genes like the dopamine DRD2 receptor will be important in characterizing the genetic components of the larger, heterogeneous group of migraine disorders.