SCN1A and Dravet syndrome: Approximately 70–80% of DS patients have been found to have mutations in the SCN1A gene encoding a neuronal voltage-gated sodium channel Nav1.1 subunit and more than 90% of these SCN1A mutations are de novo (Escayg and Goldin, 2010; Brackenbury and Isom, 2011; Verbeek et al., 2011).