[Alternating hemiplegia of childhoood and oculomotor anomalies]

BACKGROUND

Alternating hemiplegia of childhood is a syndrome which begins in the first year of life. It is characterized by repeated attacks of uni-or bilateral hemiplegia or hemiparesia. In most cases paroxysmal manifestations are observed: movements or dystonia++ attacks, episodic nystagmus, abnormal eye movements and disturbance of the neurovegetative system, predominantly in the first year of life.

ANALYSIS

In half of the cases, neurological anomalies begin during the neonatal period with a non characteristic aspect. Typical attacks take place after one year of life, sometimes associated with partial epilepsy. In a quarter of cases, the oculomotor anomalies have been known since early life. The diagnosis is made prior to one year on the basis of associated oculomotor anomalies and other symptoms without EEG arguments for epilepsy. Paroxysmal nystagmus is always found. One eye is affect in most cases, generally with horizontal and seldom with vertical movements of large variable pendular amplitude. One eye with nystagmus and the other with mydriasis is sometimes reported. Most attacks last from 30 sec to 3 min. Paroxysmal strabismus described in half of the cases seems to be generally unilateral internuclear transitory ophthalmoplegia. Finally, ocular deviations on the hemiparetic side are described. They are generally unique or sometimes associated with head deviation. Spontaneous blinking is reduced.

CONCLUSION

Alternating hemiplegia of childhood is a non-epileptic sporadic, paroxysmal manifestation of unknown pathogenesis. Prognosis is poor. The presence of oculomotor signs suggests the diagnosis.

Detection of a novel missense mutation and second recurrent mutation in the CACNA1A gene in individuals with EA-2 and FHM

Mutations in the brain specific P/Q type Ca2+ channel alpha1 subunit gene, CACNA1A, have been identified in three clinically distinct disorders, viz. episodic ataxia type 2 (EA-2), familial hemiplegic migraine (FHM) and spinocerebellar ataxia 6 (SCA6). For individuals with EA-2, the mutations described thus far are presumed to result in a truncated protein product. Several different missense mutations have been identified in patients with FHM. At least two of these mutations have been identified on two different chromosome 19p13 haplotypes and thus represent recurrent mutations. In the present study, we have screened several individuals for mutations in all 47 exons in the CACNA1A gene by single-strand conformation analysis. We have characterised a novel missense mutation, G5260A, in exon 32 in a family segregating for EA-2. The consequence of this mutation is an amino acid substitution at a highly conserved position within the CACNA1A gene. This represents the first point mutation not resulting in a proposed truncated protein. Furthermore, this mutation has been detected in a family member with mild clinical signs including only migraine. Additionally, a second previously identified recurrent muta tion, C2272T, in exon 16 has been discovered in a patient with FHM.

A new CACNA1A gene mutation in acetazolamide-responsive familial hemiplegic migraine and ataxia

OBJECTIVE

To search for mutations in the calcium channel gene CACNA1A and to study the genotype-phenotype correlation in a family with a severe familial hemiplegic migraine (FHM) phenotype and a slowly progressive cerebellar ataxia.

BACKGROUND

CACNA1A gene mutations on chromosome 19 are involved in approximately 50% of FHM families. The association of FHM and cerebellar ataxia has been reported in a small number of FHM families, all linked to chromosome 19.

METHODS

The proband, in addition to typical hemiplegic migraine attacks, experienced severe episodes during which hemiplegia was associated with acutely altered consciousness and fever lasting several days. She, as well as her affected sister, developed a permanent, late-onset cerebellar ataxia and cerebellar atrophy evident on MRI. Linkage analysis was performed and the whole CACNA1A gene, 47 exon-intron boundaries, was analyzed by double gradient-denaturing gradient gel electrophoresis (DG-DGGE).

RESULTS

Genetic studies suggested linkage to chromosome 19p13, and DG-DGGE analysis detected a heteroduplex fragment in exon 13 of the CACNA1A gene. By direct sequencing, a G-to-A substitution resulting in an arginine to glutamine change at codon 583 in the second putative voltage sensor domain of the channel alpha1A-subunit, was identified, possibly representing the disease-causing mutation. The proband and her affected sister were treated with acetazolamide, reporting freedom from new FHM attacks but no benefit in the progression of ataxia.

CONCLUSIONS

The combination of episodic dysfunction and permanent deficit could depend on the variety of functions of calcium channels and their distribution in the nervous system.

Genetic heterogeneity in Italian families with familial hemiplegic migraine

OBJECTIVE

To verify linkage to chromosome 19p13, to detect mutations in the CACNA1A gene, and to correlate genetic results to their clinical phenotypes in Italian families with familial hemiplegic migraine (FHM).

BACKGROUND

FHM is an autosomal dominant disease, classified as a subtype of migraine with aura. Only a proportion of FHM patients have been associated with chromosome 19p13. Among these, four missense mutations within the CACNA1A gene in five unrelated families have been described.

METHODS

A linkage study was performed in 19 patients affected by FHM from five families by studying microsatellite markers associated with the 19p13 region. All familial and seven additional sporadic patients with FHM were analyzed to search for mutations within the CACNA1A gene by applying the double gradient-denaturant gradient electrophoresis technique.

RESULTS

Lod score values did not establish significantly linkage to chromosome 19. However, seven new genetic variants were detected: six were new polymorphisms. The seventh was a missense mutation present in family 1, and it was associated with a hemiplegic migraine phenotype without unconsciousness and cerebellar ataxia. Because this missense mutation is absent in the general population and cosegregates with the disease, it may be a pathologic mutation.

CONCLUSIONS

Genetic heterogeneity of FHM has been shown in familial and sporadic FHM patients of Italian origin. The new missense mutation-G4644T-is associated with milder clinical features compared with typical FHM.

A novel nonsense mutation in CACNA1A causes episodic ataxia and hemiplegia

OBJECTIVE

To identify the disease-causing mutation and to characterize penetrance and phenotypic variability in a large pedigree with episodic ataxia type 2 (EA-2) previously linked to chromosome 19.

BACKGROUND

Mutations in the CACNA1A gene on chromosome 19 encoding a calcium channel subunit cause EA-2, which is characterized by recurrent attacks of imbalance with interictal eye movement abnormalities.

METHODS

The authors used single-strand conformation polymorphism (SSCP) analysis to screen for point mutations, and direct sequencing to identify mutations in CACNA1A. Allele-specific oligonucleotides were designed to detect the presence of the diseased allele in members of their pedigree as well as in normal control subjects.

RESULTS

Reassessment of members of the pedigree revealed two notable clinical features. Diffuse weakness during attacks of ataxia was a prominent complaint. Two affected individuals had had episodic hemiplegia, one with typical migraine headaches. SSCP analysis revealed aberrant bands in exon 29 in affected members but not in normal control subjects. Direct sequencing of exon 29 identified a C-to-T change at position 4914 of the coding sequence of CACNA1A, predicting an early stop code at codon 1547. Two asymptomatic mutation carriers demonstrated the incomplete penetrance of this mutation.

CONCLUSIONS

A nonsense mutation in CACNA1A causes episodic ataxia and complaint of weakness, and may be associated with hemiplegia.

Coincidence of familial hemiplegic migraine and hemicrania continua? A case report

A case is presented of a 39-year-old woman with a history of simultaneous Familial hemiplegic migraine (FHM) and hemicrania continua (HC). The family history of the patient revealed different types of migraine and cyclic syndromes in childhood in four generations. The possible links between FHM and HC are discussed. The pedigree gives further evidence that cyclic syndromes in childhood belong to the spectrum of migraine.

Epilepsy and paroxysmal movement disorders in families: evidence for shared mechanisms

The epilepsies have been regarded as clinically distinct from the paroxysmal movement disorders. Recently, a variety of ion channel defects have been identified as the biological basis of certain familial epilepsies and paroxysmal movement disorders. We studied two families with the co-occurrence of epilepsy, movement disorders and migraine. Information was obtained on 147 individuals in the two families. In family WF, there was a co-occurrence of epilepsy (benign infantile convulsions, idiopathic generalized epilepsy), episodic ataxia (with cerebellar atrophy and without myokymia) and common migraine. In family CL, epilepsy (febrile seizures, febrile seizures plus), kinesigenic paroxysmal dyskinesia and migraine (including hemiplegic migraine) were observed in various combinations over 3 generations. The observations in these two families, together with review of the literature, suggest that the co-occurrence of epilepsy (particularly benign infantile convulsions), paroxysmal movement disorders and migraine is not due to chance. Thus, these distinct clinical phenomena could have a shared biological basis and ion channel defects are an attractive possibility.

Functional consequences of mutations in the human alpha1A calcium channel subunit linked to familial hemiplegic migraine

Mutations in alpha1A, the pore-forming subunit of P/Q-type calcium channels, are linked to several human diseases, including familial hemiplegic migraine (FHM). We introduced the four missense mutations linked to FHM into human alpha1A-2 subunits and investigated their functional consequences after expression in human embryonic kidney 293 cells. By combining single-channel and whole-cell patch-clamp recordings, we show that all four mutations affect both the biophysical properties and the density of functional channels. Mutation R192Q in the S4 segment of domain I increased the density of functional P/Q-type channels and their open probability. Mutation T666M in the pore loop of domain II decreased both the density of functional channels and their unitary conductance (from 20 to 11 pS). Mutations V714A and I1815L in the S6 segments of domains II and IV shifted the voltage range of activation toward more negative voltages, increased both the open probability and the rate of recovery from inactivation, and decreased the density of functional channels. Mutation V714A decreased the single-channel conductance to 16 pS. Strikingly, the reduction in single-channel conductance induced by mutations T666M and V714A was not observed in some patches or periods of activity, suggesting that the abnormal channel may switch on and off, perhaps depending on some unknown factor. Our data show that the FHM mutations can lead to both gain- and loss-of-function of human P/Q-type calcium channels.

[Familial hemiplegic migraine]

Familial hemiplegic migraine (FHM) is a rare subtype of migraine with aura. It is inherited as an autosomal dominant trait. A gene for FHM has been assigned to chromosome 19. This gene codes for a brain-specific calcium channel, and is responsible for FHM in 55% of the FHM families. Other FHM families have been linked to two different locations on chromosome 1. These locations contain possible candidate genes coding for calcium-and potassium channels. Thus FHM is a genetically heterogenous ion channel disorder, which is caused by at least three different genes. About 29% of the FHM families also have cerebellar ataxia, these families have all been linked to chromosome 19. The identification of the genes for FHM may be a key to the identification of the gene/genes for migraine with and without aura.

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.

Variable clinical expression of mutations in the P/Q-type calcium channel gene in familial hemiplegic migraine. Dutch Migraine Genetics Research Group

Familial hemiplegic migraine (FHM) is an autosomal dominant subtype of migraine with aura, with half of the families being assigned to chromosome 19p13. We identified missense mutations in a brain-specific calcium channel alpha1A-subunit (CACNA1A) gene on 19p13 segregating with FHM and truncating mutations in families with episodic ataxia type 2 (EA-2). Expansions of an intragenic CAG repeat have been shown in autosomal dominant cerebellar ataxia (SCA6). Hence, FHM, EA-2, and SCA6 are allelic ion channel disorders. We analyzed the phenotype-genotype relation in three unrelated FHM families with the calcium channel alpha1A-subunit gene mutations I1811L (two families) and V714A (one family). We found mutations in all but three patients with FHM (i.e., three phenocopies). In addition, the I1811L mutation occurred in two patients with "nonhemiplegic" migraine and in one subject without migraine. Cerebellar ataxia was found in both families with the I1811L mutation but not in the family with the V714A mutation. We failed to find expansions of the intragenic CAG repeat in FHM patients with cerebellar ataxia. We conclude that the I1811L mutation causes both FHM and cerebellar ataxia independent of the number of CAG repeats. The I1811L mutation may also occur in "normal" migraine patients, supporting the hypothesis that FHM is part of the migraine spectrum.

Familial hemiplegic migraine with irreversible brain damage

Familial hemiplegic migraine (FHM) is an autosomal dominant syndrome characterized by recurrent episodes of varying degrees of hemiparesis associated with migraine. The aura including hemiparesis may be prolonged and in severe attacks may often be associated with confusion or coma. We describe a case of FHM whose aura was atypically prolonged and resulted in irreversible brain deficit which on magnetic resonance imaging (MRI) was suggestive of cortical hyperperfusion. A subsequent MRI showed left brain atrophy.

Episodic ataxia and channelopathies

Clinical details are given of different types of episodic ataxia: type 1, with myokymia, and attacks which usually last a few minutes, and may occur several times a day, and treatment with acetazolamide can reduce the number of attacks; type 2, with interictal nystagmus, and attacks which last for several hours to a day or more, and treatment with acetazolamide is very effective; paroxysmal choreoathetosis with episodic ataxia, with attacks lasting for about 20 min and occurring at varying intervals; and familial hemiplegic migraine, with transient hemiplegia presenting during the aura of a migraine headache, the symptoms improving on treatment with acetazolamide. Their inheritance is of dominant type; and the gene for type 1 is mapped to chromosome 12p near to a cluster of potassium channel genes, and that for type 2 and for familial hemiplegic migraine to chromosome 19p near to calcium channel genes. The differential diagnosis from other conditions with a periodic symptomatology is discussed, especially from a number of metabolic disorders. Treatment is effective for many of these, and the treatment of the episodic ataxias with acetazolamide can sometimes have a dramatic effect. The possible role of the channelopathies in the causation of some periodic neurological disorders is considered; with the expectation that further research will improve the identification of specific diseases, and lead to more effective treatment.

A new locus for hemiplegic migraine maps to chromosome 1q31

A single familial hemiplegic migraine locus has been previously mapped to 19p13.1 and associated with mutations in a calcium channel gene (CACNL1A4). We describe a new 39-member four-generation family from Wyoming of German-Native American descent with autosomal dominant familial hemiplegic migraine that is not linked to the chromosome 19p locus. Affected individuals showed a stereotypic pattern of migrainous headache associated with hemisensory and hemiparetic attacks, without other headache types. Eighty-three percent reported minor head trauma as a trigger for individual attacks. Seventy-two percent reported other typical migraine triggers for the attacks. Attack frequency decreased with age and the overall course was benign. Genetic linkage studies of this family found strong evidence for the disease gene in this family being located at chromosome 1q31. Multipoint analysis showed lod scores > 3 in a 44-cm region flanked by D1S158 and D1S2781, using 80% penetrance and a phenocopy rate of 1/50. Haplotype and multipoint analysis, including flanking markers, suggested incomplete penetrance and variable expressivity of the disease. A single affected patient who reports atypical symptoms including daily headaches likely represents a phenocopy. This new locus for hemiplegic migraine suggests that mutations of additional calcium channels in the region may cause the disease.

Wolff Award 1997. Involvement of a Ca2+ channel gene in familial hemiplegic migraine and migraine with and without aura. Dutch Migraine Genetics Research Group

A gene for familial hemiplegic migraine, a subtype of migraine with aura, was assigned to chromosome 19p13. In this region, we identified a brain-specific P/Q-type calcium-channel alpha 1A-subunit gene, CACNA 1A, with 47 exons covering 300 kb. Sequencing of all exons and their flanking surroundings revealed polymorphic variations, including a (CA)n-repeat and a (CAG)n-repeat in the 3' untranslated region. In patients with familial hemiplegic migraine, we found four different missense mutations in conserved functional domains. One of the mutations has occurred on two different haplotypes in unrelated familial hemiplegic migraine families. Moreover, in episodic ataxia type 2, we found two mutations disrupting the reading frame. Thus, familial hemiplegic migraine and episodic ataxia type 2 can be considered as allelic channelopathies. Involvement of this familial hemiplegic migraine locus in migraine with and without aura was demonstrated by sib-pair analysis. We showed an increase of shared marker alleles of locus D19S394, which is tightly linked to the gene. The association between the alpha 1A calcium channel and familial hemiplegic migraine, and the increase of shared alleles in migraine-affected sib-pairs, have uncovered a new pathway for the pathophysiology of migraine. This finding may provide a rationale for the development of specific prophylactic therapy for migraine and other (paroxysmal) cerebral disorders.

Factor V Leiden mutation: an unrecognized cause of hemiplegic cerebral palsy, neonatal stroke, and placental thrombosis

Activated protein C resistance caused by an Arg506Gln mutation in the factor V gene (factor V Leiden mutation) is the most common cause of familial thrombosis. This mutation is associated with arterial and venous thromboembolic disease in neonates, infants, and children, but is not a significant risk factor for ischemic stroke in adults. We report on 3 babies with different neonatal cerebrovascular disorders including ischemic infarction and hemorrhagic stroke who are heterozygous for factor V Leiden mutation. One infant had multiple thrombi in the fetal placental vasculature. This is the first reported association between hemiplegic cerebral palsy, placental thrombosis, and factor V Leiden mutation. We suspect that activated protein C resistance may be an important cause of in utero cerebrovascular disease and hemiplegic cerebral palsy.

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

PURPOSE

We studied a large Dutch-Canadian family, in which two very rare hereditary paroxysmal neurologic disorders, familial hemiplegic migraine (FHM) and a "benign familial infantile epileptic syndrome" concur and partially cosegregate. FHM is a dominantly inherited subtype of migraine with attacks of hemiparesis, linked to chromosome 19p13 in 50% of the families tested. Recently mutations in a brain-specific P/Q-type Ca2+ channel alpha1 subunit gene (CACNL1A4) were identified in families with chromosome 19-linked FHM. The infantile epileptic syndrome resembles to two other dominantly inherited benign epilepsies occurring in the first year of life, benign familial neonatal convulsions (BFNC), assigned to chromosomes 20q13.2 and 8q, and benign infantile familial convulsions (BIFC), as yet unlinked.

METHODS

Linkage analysis was performed for the known locations of FHM and BFNC. The question whether the two conditions in this family can be caused by a single gene defect was addressed by additional linkage analysis.

RESULTS

We excluded linkage of the infantile convulsions to markers on chromosome 20q13.2, 8q, or 19p13. This indicates the existence of a third locus for benign familial convulsions in the first year of life. Linkage of FHM to these markers was not formally excluded but seems very unlikely. Statistical analysis of whether, in this family, both conditions are caused by a single gene defect was inconclusive.

CONCLUSIONS

We describe a "benign familial infantile epileptic syndrome" with attacks of FHM at a later age. Further genetic studies in this family may help to unravel the genetic basis of epilepsy or migraine or both.

Interictal cortical excitability to magnetic stimulation in familial hemiplegic migraine

We studied interictal cortical excitability with magnetic stimulation in controls, in patients with migraine with aura, and in patients with familial hemiplegic migraine (FHM), in which ictal hemiparesis occurs. Amplitudes (p < 0.05) and amplitude ratios (p < 0.01) revealed heightened excitability in migraine with aura when compared to controls. In patients with FHM, mean thresholds were higher (p < 0.001) and conduction times longer (p < 0.01) than in controls. In FHM, amplitudes were lower on the ictally paretic side of the body than on the other (p < 0.05). Patients with FHM may have increased interictal cortical excitability, complicated by decreased excitability of the affected side.

A family with hemiplegic migraine and focal seizures

Familial hemiplegic migraine is a distinctive form of migraine with autosomal dominant inheritance. The patients undergo attacks of migraine complicated by hemiplegia. Seizures have not been reported as comprising a part of this syndrome. We describe three generations of a family with hemiplegic migraine and focal seizures occurring concurrently with the migrainous attacks. There were five affected family members whose clinical features included unilateral headache and transient hemiplegia. Two family members also had focal seizures during the migrainous attacks. One of the patients was treated with carbamazepine with good results. The only associated neurological finding was ataxia which was found in the oldest patient. The presence of focal seizures during an episode of hemiplegic migraine suggests that the two phenomena of migraine and focal seizures may share the same underlying pathophysiology.

Focal brain dysfunction in a 41-year old man with familial alternating hemiplegia

The acute pathophysiologic changes during hemiplegic spells and the long-term outcome of alternating hemiplegia remain obscure. In a 41-year-old male with familial alternating hemiplegia we found an increase in right frontal cerebral blood flow 3 h into a 5-h left hemiplegic episode. A repeat high-resolution brain SPECT study performed 26 h after the resolution of the left hemiplegia revealed normalization of the frontal blood flow accompanied by hyperperfusion in the right parietal lobe. An interictal SPECT scan several weeks later showed no asymmetries. Head CT and MRI scans were negative. Neuropsychologic assessment and neurologic examination revealed evidence of a diffuse disorder which predominantly involved the right hemisphere. To our knowledge, there are no previous correlative studies of serial high-resolution brain SPECT with MRI, or of detailed neuropsychologic assessment, in adult patients with such an advanced course of alternating hemiplegia of childhood.