Severe neurological diseases thus arise following various mutations in ATP1A2 and ATP1A3 (de Vries et al., 2009; Benarroch, 2011; Bøttger et al., 2012): Familial hemiplegic migraine type 2 (FHM2) arises upon mutations in ATP1A2 (De Fusco et al., 2003) and is a severe autosomal form of migraine with aura associated with hemiparesis and sometimes accompanied by manifestations such as epilepsy, seizures, ataxia and developmental disabilities (Pietrobon, 2007; Bøttger et al., 2012). The gene discussed is ATP1A2; the disease is developmental disability.