Molecular mechanisms of migraine?

Targeted next generation sequencing identifies a genetic spectrum of DNA variants in patients with hemiplegic migraine

Objective:

Hemiplegic migraine in both familial (FHM) and sporadic (SHM) forms is a rare subtype of migraine with aura that can be traced to mutations in the CACNA1A, ATP1A2 and SCN1A genes. It is characterised by severe attacks of typical migraine accompanied by hemiparesis, as well as episodes of complex aura that vary significantly between individuals.

Methods:

Using a targeted next generation sequencing (NGS) multigene panel, we have sequenced the genomic DNA of 172 suspected hemiplegic migraine cases, in whom no mutation had previously been found by Sanger sequencing (SS) of a limited number of exons with high mutation frequency in FHM genes.

Results:

Genetic screening identified 29 variants, 10 of which were novel, in 35 cases in the three FHM genes ( CACNA1A, ATP1A2 and SCN1A). Interestingly, in this suspected HM cohort, the ATP1A2 gene harboured the highest number of variants with 24/35 cases (68.6%), while CACNA1A ranked the second gene, with 5 variants identified in 7/35 cases (20%). All detected variants were confirmed by SS and were absent in 100 non-migraine healthy control individuals. Assessment of variants with the American College of Medical Genetics and Genomics guidelines classified 8 variants as pathogenic, 3 as likely pathogenic and 18 as variants of unknown significance. Targeted NGS gene panel increased the diagnostic yield by fourfold over iterative SS in our diagnostics facility.

Conclusion:

We have identified 29 potentially causative variants in an Australian and New Zealand cohort of suspected HM cases and found that the ATP1A2 gene was the most commonly mutated gene. Our results suggest that screening using NGS multigene panels to investigate ATP1A2 alongside CACNA1A and SCN1A is a clinically useful and efficient method.

A case of cluster headache accompanied by myoclonus and hemiparesis

Background

Cluster headache is a primary headache disorder characterized by periodic episodes of intense headache accompanied by autonomic symptoms. We report an unusual clinical presentation of cluster headache that was preceded by myoclonus and accompanied by hemiparesis.

Case Report

A 26-year-old man visited hospital due to recurrent jerky movements on the left side of his face and neck area lasting 3 days. These jerky movements had disappeared spontaneously without specific treatment. On the 10th day after onset of the jerky movements, the patient developed a series of unilateral severe headaches that were accompanied by autonomic symptoms lasting 1-2 hours. According to the second edition of The International Classification of Headache Disorders, he was diagnosed as having cluster headache. Two of the 16 severe headache attacks this patient suffered were accompanied by dysarthria and hemiparesis. Electroencephalography performed during hemiparesis revealed diffuse lateralized slow activity on the ipsilateral hemisphere of the headache side. The headache and accompanying hemiparesis disappeared after medical treatment for cluster headache.

Conclusions

We describe a case of cluster headache accompanied by hemiparesis, which was preceded by myoclonus. We also outline the possible mechanisms underlying this case.

A dominant-negative mutation in the TRESK potassium channel is linked to familial migraine with aura

Migraine with aura is a common, debilitating, recurrent headache disorder associated with transient and reversible focal neurological symptoms. A role has been suggested for the two-pore domain (K2P) potassium channel, TWIK-related spinal cord potassium channel (TRESK, encoded by KCNK18), in pain pathways and general anaesthesia. We therefore examined whether TRESK is involved in migraine by screening the KCNK18 gene in subjects diagnosed with migraine. Here we report a frameshift mutation, F139WfsX24, which segregates perfectly with typical migraine with aura in a large pedigree. We also identified prominent TRESK expression in migraine-salient areas such as the trigeminal ganglion. Functional characterization of this mutation demonstrates that it causes a complete loss of TRESK function and that the mutant subunit suppresses wild-type channel function through a dominant-negative effect, thus explaining the dominant penetrance of this allele. These results therefore support a role for TRESK in the pathogenesis of typical migraine with aura and further support the role of this channel as a potential therapeutic target.