SCN9A and Epileptic encephalopathy: Pathogenic variants in the main CNS genes SCN1A, SCN2A, SCN3A, and SCN8A and the peripheral nervous system (PNS) gene SCN9A, that encode the NaV channels NaV1.1, NaV1.2, NaV1.3, NaV1.6, and NaV1.7, respectively, are associated with well-defined epileptic encephalopathies (Singh et al., 2009; Epi4K, 2013; Mulley et al., 2013; Ademuwagun et al., 2021).