SCN8A and autism: As discussed above, mutations in all CNS-expressed sodium channel genes (SCN1A, SCN2A, SCN3A and SCN8A) cause various forms of epileptic phenotypes, and in the case of SCN1A also familial hemiplegic migraine, symptoms that by themselves not necessarily imply the presence of neurodevelopmental problems, autism or neurodegenerative phenotypes (Table 1).