What do genetic studies tell us about the heritable basis of common epilepsy? Polygenic or complex epilepsy?

The search for genes associated with common epilepsy, including both focal and generalised epilepsies, has been intensive in the past few decades. Consequently, our understanding of the genetic background of common epilepsy has improved considerably, and current genetic studies have optimised their design accordingly, showing much promise for the future. Nevertheless, we can only explain a fraction of the heritability of common epilepsy with the currently known genetic factors. These factors have been identified with a range of different gene mapping techniques, including linkage analysis of epilepsy families, association studies, and recent large scale sequencing studies, which individually are optimal to detect a certain class of genetic variation. Here, we give a selected overview of the genetic studies that illustrate the evolution of epilepsy genetics and contribute to the evidence for a polygenic basis of common epilepsy that likely involves both rare and common disease variants.