More rarely, SCN1A mutations lead to pure FHM (Dichgans et al., 2005; Vanmolkot et al., 2007), or to FHM associated either with generalized seizures (Castro et al., 2009), or with a stereotyped phenotype (elicited repetitive transient daily blindness) that suggests a retinal form of spreading depression (Vahedi et al., 2009; Fan et al., 2016). This evidence concerns the gene SCN1A and familial hemiplegic migraine.