The functional researches of SCN1A variants have confirmed that loss-of-function leading to haploinsufficiency is the main effect of both Dravet syndrome and GEFS+, although for some variants, mixed loss- and gain-of-function effects and for few variants a net gain-of-function have been observed (Mantegazza and Broccoli, 2019). This evidence concerns the gene SCN1A and Dravet syndrome.