Migraine, Familial Hemiplegic, 2

A number sign (#) is used with this entry because familial hemiplegic migraine-2 (FHM2) and familial basilar migraine are caused by heterozygous mutation in the gene encoding the alpha-2 subunit of the sodium/potassium pump (ATP1A2; 182340) on chromosome 1q23.

Alternating hemiplegia of childhood (104290) is an allelic disorder with an overlapping phenotype.

For a phenotypic description and a discussion of genetic heterogeneity of familial hemiplegic migraine, see FHM1 (141500).

Clinical Features

Echenne et al. (1999) reported a boy who experienced recurrent comas precipitated by hemiparesis or paresthesias, aphasia, headaches, and behavioral changes, with subsequent loss of consciousness. A history of migraine or hemiplegic migraine was found in several family members. Linkage to chromosome 1q21-q23 was found.

Marconi et al. (2003) reported 2 Italian families with autosomal dominant familial hemiplegic migraine. One large family had multiple affected members over 6 generations. Clinical features of the 2 families were similar, with age at onset in the first or second decade (range, 2 to 18 years), migraine with aura, visual disturbances, language disturbances (dysarthria, dysphasia), hemiparesis, hemiparesthesias, and often confusion. Five patients had seizures, and 3 patients in the large family had mild to moderate mental retardation.

Vanmolkot et al. (2003) reported a Dutch family in which 5 members in 3 generations were affected with familial hemiplegic migraine, each with a somewhat different clinical phenotype. The proband, a 33-year-old woman, had onset at age 3 years of headache accompanied by one-sided sensory symptoms, weakness in one arm, and transient speech disturbances. Total attack duration was 1 to 2 days, with a frequency of twice a year to bimonthly. Her mother and grandmother were both affected from ages 7 and 9 years, respectively, until menarche (age 16 years in both) with headache with aura, and hand or arm weakness for 1 to 2 days. An uncle of the proband had attacks of aura without headache, with speech difficulties, sensory symptoms, and unilateral loss of hand control. Finally, a cousin of the proband had attacks with headache with aura, sensory symptoms, and weakness in arm and face.

Spadaro et al. (2004) reported an Italian family in which 8 members spanning 3 generations had FHM2. Onset for all patients was before 30 years of age, and 6 patients had severe neurologic involvement with alterations of consciousness and fever. Frequency of attacks ranged from 1 per month to 1 per year and typically lasted for several days. The proband was a 28-year-old woman who had migraine with visual aura since age 8 years. Beginning at age 12 years, she had several episodes of tonic-clonic seizures followed by elevated temperature and coma. Subsequently, she had hemiparesis, global aphasia, and cerebellar deficits, including nystagmus, dysarthria, dysmetria, gait ataxia, and intention tremor. During coma, CT scans showed diffuse swelling of the brain and EEG showed diffuse slow delta and theta activity that returned to normal in 2 weeks. Her mother had episodes of migraine with aura often associated with hemiparesis or hemihypoasthesia. Confusion, aphasia, fever, and cerebellar signs also occurred. The proband's 72-year-old grandmother had a similar history of hemiplegic migraines and was the only patient to show residual interictal cerebellar signs. Spadaro et al. (2004) noted that cerebellar involvement had not previously been associated with FHM2.

Jurkat-Rott et al. (2004) reported 6 unrelated families with FHM2. Unusual aura symptoms included dysarthria, diplopia, alien limb phenomenon, impaired hearing, and vertigo. Triggering factors included exercise, heat, emotional stress, head trauma, and angiography.

Dreier et al. (2005) reported a 29-year-old man who developed a fever, right-sided hemiplegia, aphasia, and coma over the course of several days triggered by exertional heat stroke. Approximately 24 hours after symptom onset, T1-weighted MRI studies showed evidence of a mild but significant left hemispheric blood-brain barrier opening limited to the cortex and preceding cortical edema. The findings suggested that the delayed cortical edema was vasogenic in this patient, and Dreier et al. (2005) suggested a link with the theory of cortical spreading depression in migraine aura. After a medical history suggested FHM, genetic analysis identified a mutation in the ATP1A2 gene, consistent with FHM2.

Vanmolkot et al. (2006) reported a Dutch family with FHM2 confirmed by genetic analysis. At age 2 years, the proband had 2 episodes of transient blindness, restlessness, and fever that were triggered by head trauma. After the second episode, she showed developmental regression and autistic behavior; at age 8 years she had permanent mild mental retardation. Family history revealed several other affected members who were diagnosed retrospectively with hemiplegic migraine and confusional migraine.

Vanmolkot et al. (2007) reported a young woman with severe hemiplegic migraine who was found to be compound heterozygous for 2 mutations in the ATP1A2 gene (I286T; 182340.0011 and T415M; 182340.0012). The patient had onset at age 8 years of typical hemiplegic migraine with visual aura and subsequent dysphasia, hemiplegia, and migraine headache. Her mother and maternal aunt, both of whom were heterozygous for the I286T mutation, had aura without headache and a milder form of hemiplegic migraine, respectively. Her unaffected daughter was heterozygous for the T415M mutation, as were her father and son, who had nonmigrainous headaches and migraine with aura, respectively.

Castro et al. (2008) reported 2 Portuguese families with FHM2 in which some affected individuals had features consistent with borderline personality disorder and mental retardation, respectively.

Riant et al. (2010) identified putative pathogenic de novo mutations in the ATP1A2 gene in 11 (44%) of 25 patients with onset of sporadic hemiplegic migraine before age 16 years. Four had pure hemiplegic migraine, 5 had seizures, and 5 had developmental delay or learning disabilities at school. Two patients experiences episodes of unconsciousness or prolonged coma. None had permanent cerebellar ataxia. Among the remaining patients with sporadic disease, 8 (32%) had de novo mutations in the CACNA1A gene (601011), resulting in an overall mutation frequency of 76% among patients with early-onset sporadic hemiplegic migraine. Overall, the phenotype was more severe in patients with CACNA1A mutations.

Oh et al. (2015) reported a 3-generation Korean family (KNUF-47) in which 5 members had migraine without aura. The 26-year-old proband had onset of migraines at age 21. The migraines, which occurred an average of once a month and lasted 24 hours, involved pulsating at the right frontotemporal area accompanied by nausea, vomiting, and photophobia. He did not have any aura or neurologic symptoms, including dizziness, during attacks. The other 4 family members with migraine without aura did not have any other symptoms or signs. All 5 also had progressive, moderate to severe hearing loss.

Familial Basilar Migraine

Basilar migraine is a subtype of migraine with aura in which the aura symptoms originate from the brainstem or reflect the simultaneous involvement of both hemispheres. Ambrosini et al. (2005) reported a son and his father with basilar migraine who were found to have a heterozygous mutation in the ATP1A2 gene (182340.0010). Age at onset was 15 and 12 years, respectively. Aura was characterized by scintillating scotomas, paraesthesias and hypoesthesias in the arms and perioral region, dysarthria, bilateral tinnitus, and vertigo. Typical migraine symptoms of headache, nausea, vomiting, yawning, and photo- and phonophobia started soon after resolution of the aura. The ATP1A2 mutation was also identified in the proband's paternal uncle who had basilar migraines in his youth, but at the time of the report had migraine without aura, and in the proband's first cousin, who had migraine without aura. Ambrosini et al. (2005) concluded that basilar migraine is allelic to FHM2.

Mapping

Familial Hemiplegic Migraine 2

In a large French pedigree with FHM, Ducros et al. (1997) excluded linkage of the disorder to the MHP1 locus on chromosome 19 and found linkage to chromosome 1q21-q23. Linkage to chromosome 1 was confirmed in 2 other families, but linkage to both chromosome 1 and chromosome 19 was excluded in 4 families. Chromosome 1-linked families differed from chromosome 19-linked families in that penetrance was much lower in the former, and in some of the affected members, epileptic seizures occurred during severe migraine attacks.

In a large Italian family with FHM, Marconi et al. (2003) narrowed the critical region of FHM2 to a 0.9 Mb area on chromosome 1q23 between markers D1S2635 and CASQ1-SNP. All affected members of the family shared a common haplotype.

Typical Migraine Susceptibility

In a study of Australian twins with familial typical migraine, Nyholt et al. (2005) obtained a lod score of 1.53 on chromosome 1 at 159 cM using regression analysis. This peak was within 3 cM of the FHM-implicated ATP1A2 gene, thus potentially implicating this gene in familial typical migraine. By subphenotype analyses, they found indications that individual symptoms were differentially associated with particular linkage peaks in their data. Specifically, 5 of the 10 International Headache Society (IHS) symptoms produced nominally significant lod scores at the chromosome 1 locus, with 'nausea/vomiting' and 'phonophobia' being the symptoms most associated. In a subphenotype analysis for each symptom, in which affected individuals must simply have the individual symptom, regardless of latent-class analysis (LCA) diagnosis, the chromosome 1 locus was most associated with phonophobia (lod = 1.79).

Molecular Genetics

In a large Italian family with autosomal dominant familial hemiplegic migraine spanning 6 generations, De Fusco et al. (2003) identified a point mutation in the ATP1A2 gene (182340.0001). In a second family with 7 affected members, De Fusco et al. (2003) identified a different point mutation in the ATP1A2 gene (182340.0002). Functional data indicated that the putative pathogenetic mechanism is triggered by the loss of function of a single allele. The authors suggested that 2 synergistic events may occur as a result of a mutation: an increase in extracellular potassium, producing a wide cortical depolarization and an increase in intracellular potassium, which may promote an increase in intracellular calcium through the sodium/calcium exchanger. An increase in intracellular calcium would resemble the effect of CACNA1A (601011) mutations that cause FHM1.

In all affected members of a Dutch family with FHM2, Vanmolkot et al. (2003) identified a heterozygous mutation in the ATP1A2 gene (182340.0003).

In affected members of a large Dutch Canadian family reported by Terwindt et al. (1997) in which FHM and benign familial infantile seizures (BFIS) partially cosegregated over 5 generations, Vanmolkot et al. (2003) identified a mutation in the ATP1A2 gene (182340.0004). Of the patients for whom genetic information was available, 3 with the mutation had FHM and BFIS, 5 with the mutation had FHM without BFIS, 1 with the mutation had only BFIS, and 2 with the mutation had only migraine with or without aura. Several other members with migraines did not have the mutation. Pelzer et al. (2014) found that 4 affected members of the family reported by Vanmolkot et al. (2003) who had BFIS carried a heterozygous truncating mutation in the PRRT2 gene (614386.0016), consistent with benign familial infantile seizures-2 (BFIS2; 605751). Thus, 2 different neurologic disorders segregated in this family; the diagnosis was more complex as both disorders showed incomplete penetrance.

In affected members of an Italian family with severe FHM2, Spadaro et al. (2004) identified a mutation in the ATP1A2 gene (182340.0006).

Jurkat-Rott et al. (2004) identified 6 different mutations in the ATP1A2 gene (see, e.g., 182340.0008; 182340.0009) in affected members of 6 unrelated families with FHM2. Penetrance was mildly reduced at approximately 87%.

Vanmolkot et al. (2007) reported an affected family in which the proband with severe FHM2 was compound heterozygous for 2 mutations in the ATP1A2 gene (182340.0011; 182340.0012). Family members with milder forms of the disorder were heterozygous for 1 of the mutations, suggesting reduced penetrance. The authors stated that this was the first report of compound heterozygosity in FHM2.

De Vries et al. (2007) identified mutations in the ATP1A2 gene in 5 (13%) of 39 patients with sporadic hemiplegic migraine. Three relatives of 1 of these patients were subsequently found to carry the same ATP1A2 mutation: 1 developed FHM, and 2 remained asymptomatic, indicating reduced penetrance.

In affected members of a 3-generation Korean family with FHM2, Oh et al. (2015) identified a heterozygous missense mutation (V191M; 182340.0015) in the ATP1A2 gene. All affected members of the family also had progressive hearing loss. The mutation segregated with the phenotype in the family and was not found in the dbSNP or 1000 Genomes Project databases or in 200 Korean controls with normal audiograms. See DFNA7 (601412) and DFNA49 (608372) for 2 hearing loss loci that map to the same region as the ATP1A2 gene.

Pathogenesis

Upon venous infusion of CGRP (114130), Hansen et al. (2008) found no difference in the incidence of reported migraines or migraine-like headaches between 10 controls and 9 patients with familial hemiplegic migraine (FHM1 or FHM2). CGRP did not induce aura in any individuals. The findings suggested that FHM patients do not show hypersensitivity to the CGRP pathway, as had been observed in patients with migraine without aura (MO), suggesting that the FHM and MO phenotypes have different pathophysiologic mechanisms.