CACNA1A, hemiplegia, and the genetic of migraine

FHM. Each time I mention CACNA1A and its association with migraine to clinicians and scientists outside the field of pediatric neurology or neurointensive care, I need to take one step back. Yes, CACNA1A is one of the monogenic causes of hemiplegic migraine, but the clinical condition that we are typically concerned with has relatively little to do with common migraines. In contrast, we are talking about a neurodevelopmental disorder often associated with developmental concerns, ataxia, epilepsy and episodes of hemiplegia that may results in brain swelling and can be life-threatening. This condition, typically referred to as familial hemiplegic migraine type 1 (FHM1), neither runs in families nor does it typically result in migraine features. The historical naming conventions complicate awareness of one of the most enigmatic events in neurology, which we refer to as hemiplegic migraine episodes for a lack of a better word. However, I wanted to approach CACNA1A from a different perspective, given the recent publication of a large migraine genetic study in Nature Genetics. Continue reading

CACNA2D2, the ducky mouse, and what it takes to be an epilepsy gene

Subunit. Spontaneous mouse mutants help to identify candidate genes for disease mechanisms and have hinted at an important role for ion channels in epilepsy long before the first human channelopathies were identified. The ducky mouse has absence seizures and suffers from ataxia. A truncation mutation in CACNA2D2 could be identified in this phenotype, encoding for an auxiliary calcium channel subunit. This finding emphasizes the role of calcium channels in absence seizures and begs the question whether genetic variation in CACNA2D2 is also involved in human epilepsy. A recent publication in PLOS One now identifies the second recessive CACNA2D2 mutation in a patient with epileptic encephalopathy. But are two independent cases sufficient anymore to claim causality? Continue reading